US2954917A - Electric swinging compressor - Google Patents

Description

Oct. 4, 1960 F. BAYER ELECTRIC swmcmc COMPRESSOR Filed Dec 4 Sheets-Sheeg 1 Inventor FRIEDRICH 8A YER A flomeys Oct. 4, 1960 'F. BAYER 2,954,917

ELECTRIC SWINGING COMPRESSOR Filed Dec. 7, 1956 4 Sheets-Sheet 2 Fig.4

Fig. 5

25per/s FR/E'DR/CH BAYER Attorneys Oct. 4, 1960 F. BAYER ELECTRIC swmcmc COMPRESSOR 4 Sheets-Sheet 3 Filed Dec. 7, less .lm emor:

FRIEDRICH BA YER A fforneys Oct. 4, 1960 F. BAYER 2,954,917

ELECTRIC SWINGING COMPRESSOR Filed Dec. 7, 1956 4 Sheets-Sheet 4 Fig I2 95 P as 89 g3 82: I an Wllllllll 94 zz L"! FR/EDR/CH BAYER A ffameys [04C I035 I046 Inventor:

United States Patent ELECTRIC SWINGING COMPRESSOR Friedrich Bayer, Stuttgart-Mohringen, Germany, assignor to Licentia Patent-Verwaltungs-G.m.b.H., Hamburg, Germany Filed Dec. 7, '1956, Ser. No. 626,884

Claims priority, application Germany Dec. 7,1955

4 Claims. (Cl. 2'3055) This invention relates to compressors. More in particular, this invention relates to electro-magnetic oscillating compressors compressing gaseous substances used, for example in refrigerating systems and the like.

, One of the greatest problems confronting the art with respect to electro-magnetic oscillating compressors operated by A.C. current supplied by the public electrical net work resides in the extremely elevated speed of the piston of the compressor. This great speed is due to the fact that the electro-magnetic oscillatory frequency is 50 or 100 cycles p. sec., if an A.C. current of 50 cycles p. see. is supplied by the net work; it is 60 or 120 cycles p. sec. in the case of an A.C. current of 60 cycles supplied by the net. The frequency of the A.C. current available from the lines of a public electrical net shall be referred to hereinafter as net frequency. This corresponds in the first case to a number of revolutions of the corresponding motor compressors of from 3000 or 6000 p. min. or in the second case of from 3600 or 7200 p. min. At such tremendous speeds it is very difficult to have sufliciently large cross sections of the valves and generally to have valves which can follow these fast oscillations in a satisfactory manner, while at the same time having a good sealing performance and a sufliciently long life time. Additional difiiculties are caused by the construction of the necessary springs for adjusting the oscillating mechanical system to the frequency of the impelling A.C. current. Finally, the considerable forces of friction produced in the compressor on account of elevated oscillating speeds are undesirable and a cause of inefliciency. v

These difliculties have been widely recognized and various attempts have been made in the art to reduce the frequency of oscillation of the impelling means.

Several attempts have been made in this direction with electro-dynamic oscillatory impulsions wherein the frequency of oscillation is equal to the frequency of excitation because of the requisite D.C.-polarization. In one instance it has been possible to reduce the frequency of oscillation to half the amount of frequency of excitation, i.e. to reduce the frequency of oscillation to 25 cycles p. sec. at a frequency of 50 cycles p. sec. of the feeding A.C. current by so constructing the oscillating system that the magnetic field permeating the armature winding fed by the A.C. current assumes an opposite direction on both sides of the intermediate position of the oscillating armature. (Swiss Patent 208,419). However, the electrodynamic oscillatory impelling system suffers from the disadvantage of requiring two current sources for its operation, although the magnetizing DC. current can in some cases be replaced by permanent magnets. In addition, the amount of windings required is comparatively great. Furthermore, the quantitative yield as well as the degree of efiiciency are very low if these impelling systems are used for refrigerating compressors.

In the known art electro-magnetic oscillatory impelling systems have been devised wherein the mechanical frequency of oscillation is made equal to the net frequency by polarization or by employing permanently ice magnetic armatures. According to another construction, the mechanical frequency of oscillation is brought to the same level as the net frequency by feeding the exciting system with half waves of the A.C. current supplied by the net. This is done by means of a half wave rectifier. (Patents 1,637,401; 2,180,189.)

Finally, an equalization of the respective frequency of oscillation can be accomplished by mechanical means. This is achieved by providing the armature and the magnet poles with teeth and causing the armature to oscillate between neighboring, magnet pole teeth polarized in the same sense. In this case the oscillating, mechanical system must be tuned to this frequency. (Patent 2,351,6 3.)

With all these electro-magnetic oscillating systems it is practically impossible to further reduce the frequency of oscillation. In order to further reduce this frequency, additional devices are needed suppressing a determined number of the half waves of the A.C. current as, for instance electric retarding net works, gate-circuits, and the like. This strictly electrical method of reducing the frequency of oscillation is accompanied by great disadvantages. First of all, a considerable array of supplemental switching' means is needed for eliminating the surplus half waves. Thereby the economic operation of such oscillatoryimpelling systems is greatly impeded. In addition, only a fraction of the supplied energy is utilized within the exciting magnet itself and the degree of efficiency is therefore extraordinarily low. Another disadvantage accompanying this type of oscillating compressors is the undesirable range of operation of the piston of the compressor: whenever the oscillating mechanical system is in resonance with the exciting frequency, as this is usually the case, the oscillating stroke increases rapidly unless there is a counter pressure within the compressor, as for example during the initial stages of the operation or because of some kind of a disturbance. The result of this considerable increase of the oscillating stroke makes the piston of the compressor hit against the cover of the cylinder. Not only the piston and the cylinder but, what is worse, the valves are in great peril of being damaged and, quite apart from that a strong noise is produced, making this type of oscillating impelling system unbearable in household appliances, as for example refrigerators.

This problem has been recognized in the art and it has been suggested to prevent the piston from hitting the cover of the cylinder of electro-magneting oscillating compressors operated in resonance with the exciting frequency by attaching to the cylinder a small ante-chamber (German Patent 596,890). This small ante-chamber is sealed against the space of compression by an intermediate valve and against the pressure conduit by a spring actuated pressure valve. The pressure valve maintains the pressure within the ante-chamber above a certain minimum value.

By virtue of this arrangement a counter pressure sufficiently dampening the oscillating stroke is produced during the initial stage of operation of the compressor. This counter pressure rises rapidly because of the small volume of the ante-chamber and thus counteracts unduly great amplitudes of the oscillation.

Experience and practical tests made with this device have shown, however, that the ante-chamber taken alone does not suflice to prevent the piston from hitting the cover of the cylinder, unless the dead space in the compression cylinder is to be expanded to such a degree that the efficiency is fatally reduced. The tested device results only in a certain dampening of the hitting process and does not eliminate the noise to a satisfactory degree.

It is an object of the present invention to provide a system comprising an lectro-magnetic element, an oscillating element and a stator, wherein the oscillating element can be caused to oscillate with half the frequency by very simple means, when the stator is excited by AC. current supplied from the net.

It is another object of the present inventionto-provide an electro-magnetically irnpelled oscillating compressorwherein the friction losses are reduced and conventional valves can be used. 7 I 7 It is still another object of the present invention to provide an electro-magnetically impelled oscillating compressor wherein the oscillating masses are comparatively small.

It is a further objectofthe present invention to provide an electro-magnetically impelled oscillating corn pressor which oscillates with half the frequency of the current supplied by anordinary A. c. current net without requiring a great number of additional switch means.

It is another object of the present invention to provide an electro-magnetically impelled oscillating compressor wherein the electro-magnetic impelling system is so constructed that excessively high oscillating strokes in the absence of a counter pressure are eliminated.

It is still a further object of the present invention to provide an'electro-magnetically impelled oscillating compressor wherein the compressor works very quietly irrespective of the load conditions.

It is still another object of the present invention to provide an electro-magnetically impelled oscillatingcompressor wherein the compressor has a comparatively small dead space. y f

These objects as well as other objects and advantages which will become apparent from the following. description are accomplished and the aforementioned disadvantages, of the apparatus known in the art are avoided by the oscillating electro-mechanical system of the invention, comprising, in combination, an electric impelling system, a magnetic system and a mechanical device to be impelled. The mechanical device may consisnfpr example, of a compressor or a pump. v

The magnetic system consists of a stator and an oscillator which is so arranged relative to the pole surfaces of the stator that an oscillatory movement results having a direction parallel to the polelsurfaces and which results in anoscillation, the amplitudev of which has no mechanical limitation. v 1 v The electric impelling system comprises a half wave rectifier and one or several exciting windings coiled; around the aforementioned stator of the magnetiesystem.

The entiresystem is operated by the half waves obtained from the half wave rectifier fed by an ordinary- A.C. current line. The resting position of the oscillator must be so chosen that of two following half waves the first half wave moves the oscillator in the first end position and the second half wave moves the oscillator into the opposite, second end position. This is accomplished by providing one of the two members forming the magnetic system with teeth. The difference of the number of the two members must be an odd figure and should preferably be 1. Furthermore, care must be taken that the pole surfaces of the two members are not symmetrically congruent relative to one another during the resting position of the oscillator.- The pole surfaces of the two members should preferably be so opposed that they do not cover each other.

The oscillator is adjusted to the desiredresting posi tion by resilient and preferably elastic means. The oscillating mechanical system comprising the armature, the compressor piston and the resilient means are broughtto a natural frequency corresponding'approxirnatelyto half the net frequency. I

The preferred embodimentof the electromechanical system of the invention consists of an oseill atingeom pressor having an electromagnetic impelling-system with poles and an armature which is provided with teeth; according to this preferred embodiment thedifieren'ce-between the number of the teeth of the poles and the teeth of the armature is, 1 and if there is no current the ar-mature assumes a position relative to the poles that the teeth of the poles are facing the intermediate space between two neighboring teeth of the armature, hereinafter called interstice.

The oscillations of the exciting system of the-invention oscillating in resonance must be prevented from attaining excessively large amplitudes which would result in the piston hitting against the cylinder "cover. This is avoided by displacing the resting position of the armature from a symmetrical position opposite tojthe pole shoes to such an extent that in the absence of a sufficient counter pres-. sure in the compressor the armature oscillates in the beginning at the frequency of the exciting current half waves and with a small amplitude. After a sufficient counter pressure has been built up the oscillation of the armature is automatically synchronized to the mechanical natural frequency corresponding substantially to half the net frequency, thus performing oscillations having a large amplitude. v 7

The displacement from the symmetrical resting position must be effected in the direction of the compression stroke. The distance of the displacement depends upon the ratio of the width of the poles to the Width of the distance between the parts of the subdivided poles and the width of the opposite pole.

This will be illustrated by numerical data indicated further below. v I

. Furthermore, the energy of the resilient means must be adjusted in such a manner that in the absence of counter pressure the oscillator does not swing back beyond the symmetrical position of the pole having an inferior number of teeth in front of the interstioe of the pole having the greater number of teeth.

The advantages of these features of the invention can befurther increased by a particular construction of the compressor. For example, the compressor cylinder can be made to assume an elongated, configuration which is longer than the stroke produced by the oscillating impulsion would normally require. The cylinder space can be divided into a cylinder space proper and an antechamber of a correspondingly smaller volume byan in tertnediate valve occupying the entire cross section of the cylinder and arranged. substantially at the point oftreversal of the piston at maximum pressure; According to a preferred embodiment of this part of the. invention an intermediate valvegis'chosen "which can-be pushed .forward -by the. piston in case of great amplitudes of oscillation.

Additional objects and advantages will become apparent from the following detailed description of the accompanying drawings wherein, H

Figure l is a diagram of; an electro-magnetic oscillat-. ing compressor of the invention, and its switch connections;

Figure :2 is a cross-section along the line II -tII in Figure 1 and shows the'poles and the armature of the compressor of the invention; a I

Figure 3 is a diagram showing the half wave fed to the exciting coil and the corresponding movement of the armature at various operational pressures;

Figure 4 is a longitudinalsectional view of'a preferredembodiment of the apparatusof; the invention;

Figure 5 is a diagram illustrating the work performed bythec'ompressor of the apparatus shownin Figure. 4;

Figurev 6 is. a lateral view, partly'in section ofanother embodiment of the electromagnetic system of the. "ap-. par-atus oft'heainventiom' J Figure 7 isua lateral view partly in section of still another embodiment .of the electromagnetic timpelling rsys tem of the apparatus oftheinvention;

Figure 8 is a longitudinal sectional view .of' a further embodiment of the el'ectro-magnetic system of'the apparatusof theinyention; l

Figure 9 is a cross sectional view taken along the line IX-IX of the embodiment shown in Fig. 8;

Figure 10 is a diagrammatic lateral view of still another embodiment of the electro-magnetic impelling system of the invention;

Figure 11 is a diagrammatic view of the impelling system shown in Figure 10 as applied ,to a wing compressor with some modifications;

Figure 12 is a longitudinal sectional view taken along the line XII-XII of the Wing compressor shown in Figure 11;

Figure 13 is a cross-sectional view of the wing compressor shown along the line XIIIX[I'I in Figure 12;

Figure 13a shows an enlarged portion of the wing compressor shown in Figure 13;

Figure 14 is alongitudinal sectional view of a piston compressor with an electro-magnetic impelling system of the rotation-oscillating type, taken along the line XIV-XIV in Figure 15;

Figure 15 is a cross-sectional view of a piston compressor with an electro-magnetic impelling system of the rotation-oscillating type, taken along the line XV-XV in Figure 14;

Figure 16 is a sectional view of a piston compressor with an electro-magnetic impelling system of the rotationoscillating type, taken along the line XVI-XVI in Figure 15;

Figure 17 is a top view of the entire swing compressor of the embodiment of Figures 14 to 16.

' Referring now to the drawings more in detail, Figure 1 shows the overall construction of the electro-mechanical system of the invention and its electrical wiring. If the apparatus of the invention is employed, for example, in refrigerators as a refrigerating compressor, the apparatus is housed in a hermetically sealed casing 1. The entire system of the oscillating compressor is composed of a mechanical part and an electrical part. The mechanical part is composed, for example of the compressor cylinder 2, the piston 7 moving within the cylinder 2, and the housing 3 consisting of a non-magnetic material. In connection with this housing 3 there is arranged the magnet frame 4 of the electromagnetic impelling system forming the second part of the entire system of the invention' The magnet system is composed in a conventional manner of dynamo sheets and is equipped with two poles 5, 6 located opposite to each other. Each of the two poles 5, 6 is divided by an interstice or recess 5a and 6a respectively into two separate subpoles or teeth 5, 5" and 6', 6" respectively. Between these two poles, a disc shaped armature 9 serving as the oscillator is mounted upon the shaft 8 connected to the piston 7 of the compressor. The armature is adjusted relative to the toothed poles 5, 6, by resilient means such as, for instance, springs 10, 11 in such a manner that in its position of rest the aramature faces the interstices 5a and 611 between the subpoles 5, 5", 6, and 6". In addition, the springs 10 and 11 are so adjusted to the total mass of the combined armature 9, shaft 8 and the piston 7 that the entire movable mechanical system possesses a natural resonance frequency substantially corresponding to half the frequency of the exciting A.C. current. Preferably, the natural resonance is slightly inferior to half the frequency of the exciting A.C. cur rent, for reasons set forth further below. The magnet system is excited by exciting coil means disposed about the legs of the magnet. The exciting coil means may consist, for example, of two coils C5 and C6 connected in series. The exciting current is supplied by the norm-a1 A.C. current network and an interposed half wave rectifier R. Any suitable type of rectifier can be employed. It will be found useful to use dry plate rectifiers, e.g. a selenium rectifier. The exciting coil means is thus fed with half waves and receives 50 impulses of uniform direction per second if the net frequency is 50 cycles per second. The approximate characteristic of these current impulses is shown by the upper curve in Figure 3 of the drawings. The corresponding characteristic of the armature movements is shown by the lower curve of Figure 3.

These impulses produce the following efiect in the oscillatory mechanical system: 7

Every impulse creates an electro-magnetic field between the poles of the magnetic system. The two teeth of each pole 5 and 6 have identical polarity. If the armature 9 were to assume a position exactly between the teeth of the poles, the upper and the lower teeth would equally attract the armature and consequently the armature would 'retain its initial or zero position. For that reason the armature 6 is so adjusted in its position on shaft 8 as to assume a slightly asymmetrical position relative to the teeth 5', 6' on the one hand, and 5", 6" on the other hand. A very small degree of asymmetry is sufficient. If the armature 6 is positioned in this manner, the first current impulse will cause the armature to be attracted by the nearest couple of subpoles. If the nearest couple of subpoles should be the lower one, i.e. teeth 5" and 6" in Figure 1, if the system is disposed with shaft 8 in vertical position, the first half wave I (upper curve in Figure 3) will draw the armature in downward direction (see branch A of the lower curve in Figure 3). The armature 9 will then bridge the air gap between the two lower teeth 5" and 6". During the following currentless interval Ia (upper curve in Figure 3) the armature will be moved in upward direction by force of the tension spring 11 (see branch B of the lower curve in Figure 3). The kinetic energy stored in the armature 9 will make it swing through and beyond the substantially symmetrical resting or zero position and make it approach the zone between the upper teeth 5 and 6. By dint of the adjustment of the resonance of the swinging masses mentioned above, the last-mentioned motion of the armature 9 will occur during or immediately prior to the commencement of the next following half wave II (upper curve in Figure 3) The half wave causes the upper teeth 5' and 6' to attract the armature, since these teeth 5 and 6' now exercise a greater magnetic force of attraction upon the armature. The armature will thus continue to pursue the ascending motion initiated by spring 11, as shown by portion B of the lower curve in Figure 3. This movement is continued until the armature has reached the upper end position between the upper teeth 5' and 6'. During this last-mentioned phase of the operation, the last half wave II is subsiding, spring 11 is being detensioned and spring 10 is being tensioned. During the currentless period IIa (upper curve of Figure 3), the armature 6 is moved in opposite direction by the action of spring 10. The moving armature 9 passes the resting zero position and is pulled further downwardly by the third half wave III (see upper curve and portion C of lower curve in Figure 3). This alternating movement of the armature 6 is continued in the same manner as the armature is impelled by subsequent half waves. Dependent on the prevailing compressor pressure in the cylinder 2, there is a phase displacement between the curve described by the moving armature on the one hand and the curve of the exciting half waves on the other hand. The lower curve in Figure 3 drawn in full lines corresponds to a pressure of approximately 4 atmospheres; the lower curve in Figure 3 drawn as a dashed line corresponds to a pres sure of approximately 6 atmospheres and the lower curve in Figure 3 drawn as a dashed-dotted line corresponds to a pressure of approximately 8 atmospheres in the compressorcylinder 2; all curves have been obtained on the basis of the example described in greater detail further below. Thus, during a period composed of two half waves and two current intervals the armature performs one complete oscillation. During the same periodthe feeding A.C. current has performed two periods. As a result, the oscillatory compressor will perform 25 cycles 1). sec., ie, 1500 strokes p. min., if fed by an AC. current net of 50 cycles p. sec.

system is preferably "adjusted toa corresponding halffreque'ncy of 25 cycles p. sec. An exact adjustment is unnecessary, since the variations of the frequency occuring in an ordinary A.C. current net do not exercise any harmful influence upon the operation of the-compressor. By using an armature 9 the movement of which is not limited by the magnetic coil means C5 and C6, the elements of the magnetic circle attracting each other are prevented from colliding, independently of -the-oscil lating amplitude. Inview of the well-known fact that the resonance frequency of such an oscillating system becomes slightly displaced with increasing load, the mechanical adjustment ofresonance is effected preferably in such manner that, during idling, the frequency of resonance is somewhat less than half the net frequency.

Thereby, the resonance frequency is caused to approach the exciting frequency, as the load is increased and will coincide with half the net frequency when operated under full load. It has already beenmentioned further above, that an adjustment of resonance is advantageous in regard to the utilization of energy and conducive to obtaining sufficient oscillating amplitudes, but that, at the same time, it is accompanied by the difliculty of. providing excessively large amplitudes concurrently with a lack of counter pressure. The particular construction of the magnetic system, the manner of excitation, as well as the adjustment of the oscillating parts offer a solution to overcome this drawback. This is accomplished by the above-mentioned feature of displacing the resting or zero position of the armature 9 from a position which is symmetrical relativeto the poles 5 and 6 of the magnetic system, in the direction towards the compressor cylinder 2, until a position is reached, wherein the armature 9 assuredly remains within the range of influence of the subpoles 5" annd 6" which are situated in the proximity of the compressor while the half waves of the exciting current follow one upon the other. This resting or zero position of the armature is shown in the preferred embodiment of the present invention, which embodiment is illustrated in Figure 4 of the drawings. The desired zero position shown therein is attained by a corresponding adjustment of the springs 10 and 11.

Figure 5 shows how, from this position, the armature 9 starts to oscillate within the range of the lower subpoles 5"and 6" with small amplitudes and at a frequency which is identical to the net frequency. The small oscillations are continued until a sufiiciently elevated counter pressure has been created within the compressor cylinder 13a. The small oscillating amplitudes are due to the fact that, as long as the oscillating frequency is identical to the net frequency, the mechanical system is not in resonance during this first part of the oscillation. The counter pressure building up in the compressor cylinder 13a influences the armature 9 in the respective intervals between the occurrence of the half waves of the exciting current, and gradually displaces the zero position about which the armature 9 oscillates more and more away from its asymmetrical resting position. This continues until a zero position is reached which is situated closer to the upper subpoles 5' and 6' than to the lower subpoles 5" and 6", and the piston passes through that new zero position upwardly at a time when the following half wave starts to exercise its influence. Accordingly, the armature is pulled into the effective range of the upper subpoles. From this moment on, the armature executes large oscillating amplitudes at half the net frequency, in a part described further above. This manner of operation is further illustrated by right half of the oscillogram shown in Figure 5 of the drawings. As can be seen in Figure 5,'the oscillations of the armature are kept comparatively small during the critical period in which a counter pressure is missing and during which I In order toaccomplish large oscillation amplitudes, the mechanical oscillating 8 period the oscillating amplitudes cannot yet be dampened (left half of Figure 5). The above mentioned difliculties that excessively large amplitudes may "be generated, while counter pressure is lacking, are thereby avoided to a very great extent.

The abovenrentioned practical embodiment of an electromagnetic oscillatorycompressor shown in Figure 4 shall now be described in detail. The construction of thiscompressor is essentially in harmony with the diagramef-the electro-mechanical oscillating system shown in Figure 1. By way of simplification, the outer casing and external piping and electrical connections are not shown;

The electrical part of the oscillatory compressor 'comprises a U-shaped magnet core 4 having poles 5 and 6 inwardly directed atthe ends of the legs 4a .and 4b. The poles 5 and 6 are each composed of two subpoles 5 5" and 6', 6","respectively. The .subpoles of each pole are, in turn, separated by recesses 5a and 6a, respec-.' tively. 'The magnet core 4 preferably consists of laminations fabricated from a magnetic material known per se. -The two poles 5 and 6' are opposed to and face. each other. Between them there is arranged a shaft 8. and upon this shaft there is mounted a disk-shaped, preferably laminated armature 9 in such a manner that the shaft 8 and the armature 9 can move together freely in a vertical direction relative to the planes in which opposite subpoles extend. In order to mount armature 9 firmly upon the shaft 8, the latter being provided with a ledge-8a supporting the sheet metals of the armature 9. The sheet metals forming the latter are held in position by a pressure disk 31 pressing firmly against the uppermost sheet and secured by a bolt 32-passing through the shaft 8. The sheets are isolated from the shaft 8, for example, by an isolating layer 8b. Shaft 8 is positioned, on the one hand, in a bore 12 which is provided in the basis of core 4 and, on the other hand, connected to the piston 7 of the compressor. This piston 7 is guided inside the wall of the cylinder bore 13:: provided in the compressor casing 35. The two poles 5 and 6 are each surrounded by an exciting coil C5, C6, respectively, connected in exactly the same manner as described above with regard to Figure .1.

The height hof the armature 9 corresponds approxi mately to the-width b of the subpoles 5', 5" and 6, 6.', respectively. The recesses 5a and 6a between the subpoles measure approximately one and one half times the width of the subpoles. The armature 9 is adjusted to adopt the required resting position by means of the two helical springs 10 and 1'1 surrounding the shaft 8 and each resting with its one end against the armature 9 and, with its respective other end, spring 10 against the yoke 40 of magnet core 4, and spring 11 against the compressor casing 35, respectively. During the curr'entless state, the armature 9 is located in this determined resting position, opposite to and facing the interstice between the'subpoles, but being displacedsomewhat towards the lower sub poles 5" and 6 so that its lower edge 9a is at a level with the upper edges 50, 6c of the lower pair of subpoles 5" and 6" or so that it is situated slightly above the level of the upper edges 50 and 6c. The helical springs 10 and 11 are slightly tensioned while in their resting position. They are so adjusted to the other elements of the system as to form together with the armature 9, the shaft 8, and the compressor piston 7 an oscillating mechanical system having a natural frequency somewhat below the half frequency of the AC. current obtained from the main power network.

The casing 35 serves simultaneously as a carrier frame for the magnet system 4 and comprises the bore 13a being a part of the cylinder chamber 13. This cylinder chamber 13 is elongated in a downward direction through a bore 13b in an intermediate piece 14 which is fastened to the lower end of the compressor casing 35. This intermediate. piece 14 also provides the end wall .15 for the,

9 cylinder chamber 13. This arrangement provides a stunciently elongated cylinder chamber and the piston 7 cannot strike against the end wall 15, even when oscillating with its maximum amplitude.

To confine the apparatus to this construction would result in the disadvantage of having an undesirable large dead space. This large dead space would stifle the efliciency especially in case of elevated pressures. In order to compensate the elongated construction of the cylinder chamber 13, it is divided into two chambers formed by bores 13m and 13b. Near the plane of division, a spring loaded intermediate valve 16 is arranged parallel to the head surface 7a of the piston and covering the entire cross sectional area of the cylinder chamber 13; This intermediate valve divides the cylinder chamber 13 into the compression space proper (C) between the top surface 16a of the valve 16 and the head surface 7a of the reciprooating piston, and into a dampening space D between the lower surface 16b of the intermediate valve 16 and the cylinder end wall 15. The intermediate valve 16 is arranged approximately at the level of the point of reversal of the piston at the highest required pressure and thus forms,in a manner. of speaking, a first, displaceable cylinder cover. The intermediate valve 16 is adapted to be pushed downward ahead of the piston in case of large amplitudes of oscillation of the latter. This necessitates a graded configuration of the cylinder within the range of the dampening space, and, therefore, the intermediate piece 14 is provided with -a bore which is wider than the cylinder bore 13a. The intermediate piece 14 further comprises an internal ledge 17 and an opening 10, therein the diameter of which opening corresponds to the diameter of the bore 13a. The intermediate valve 16 rests against this ledge 17 and is pressed against the latter by the spring 19. It therefore functions like an ordinary pressure valve.

Above this intermediate valve 16 there is arranged a suction valve 20 formed as a ring valve and clamped between the end surface 35a of the casing 35 and the intermediate piece 14. In order to enable this valve to breathe, the inclined front surface 17a of the intermediate piece 14 facing toward the cylinder bore 13a is recessed. An annular groove 21 is cut into the end surface 35a of the casing 35 and is connected via the intake channel 22 with an intake conduit for the gas to be compressed (not shown). In the example of a'refrigerating compressor used in this description for the purpose of illustration only, the compressor is located within a hermetically sealed casing (not shown in Figure 4) subjected to suction pres sure (see Figure l), wherefore the intake channel is connected only with the interior of the sealed casing. The suction intake valve 20 formed by a ring plate which is clamped at its outer margin between end surface 35a of the casing 35 and the intermediate piece 14, rests resiliently against the annular groove 21; spring means are not re quired because of the tensioning of the valve as a diaphragm. The inner diameter of this annular valve is somewhat larger than the diameter of the piston, and the piston can therefore pass through the valve.

The suction valve can also be arranged laterally in the wall of the cylinder or in the bottom of the piston as an ordinary plate valve. In the latter instance the gas to be compressed can be conducted through the hollow shaft of the piston and the armature (see Patent 2,054,097).

The cylinder end wall 15 is connected via a central bore 23 to the lower end surfacel4a of piece 14. The

lower opening of bore 23 is surrounded by an annularupon the end of 'the intermediate piece 14 which is provided for this purpose with an external thread 33. The pressure valve 27 is pressed by a comparatively strong spring 29 against the end surface 14a to close the bore 23, and normally shuts off the cylinder and dampening space against the pressure conduit 26. The space enclosed in the cap 28 communicates with the interior of the outer casing 1 of Figurel through a bore 30. At its side 27a facing the cap space, the diaphragm forming valve 27 is, therefore, under the influence of the suction pressure prevailing in that external casing. The tensioning of the pressurev valve effected by the spring 29 is so chosen, that the piston 7 must work against a determined minimum bias pressure. The amount of this bias pressure depends on the demanded work pressures and will be in the order of 3 atmospheres at the normal Working pressure of from 6 to 8 atmospheres.

The operation terval following the first half wave, the armature swings back as it is influenced primarily by the energy of the spring 11. Since, with the exception of the pressure in the dampening space, there is as yet no counter pressure built up in the compressor, the armature swings only a very short distance beyond the resting position and, accordingly, the next following magnetic impulse again draws the armature downwardly, because, at the moment at which this impulse takes effect, the armature is still closer to the lower pair of subpoles than to the upper pair. The armature thus oscillates at the frequency of the exciting half wave, e.g. with a 50 cycle A.C. current, it oscillates at a frequency of 50 cycles p. sec. The amplitudes of the oscillation remain quite small, because the springs and the swinging masses are adjusted to half the exciting frequency. The oscillating frequency is therefore initially far beyond the range of the frequency of resonance which would eventually result in large amplitudes. During the period of a missing counter pressure, this adjustment therefore prevents the undesirable development of large amplitudes, which would result in the piston hitting against the cylinder bottom. This protective effect is further enhanced by the pressure within the dampening space D against which the piston must act, and which is not yet suflicientto lift the pressure valve 27. On the other hand, the intermediate valve 16 is already being actuated, even while there are but small oscillations and, hence, thepressure in the dampening space is being gradually increased.

The mounting pressure first in the dampening space and, after the tensioning of the pressure valve has beenovercome, also in the remaining parts of the system, gradually incites the armature during the following current intervals and because of the resulting counter pressure on piston 7, to swing back more and more beyond its resting position until, finally, the armature swings beyond the symmetrical position between the pole shoes 5 and 5", and 6' and 6" respectively. The zero position through which the armature passes at each oscillation is thereby shifted closer to the upper pair of subpoles 5', 6' than to the lower pair of subpoles, and, at the commencement of subsequent impulses, the annature is consequently attracted by the upper pair of sub: poles. At this moment, the stroke is suddenly increased and the oscillation of heretofore the entire net frequency is abruptly converted to half the net frequency. Atthe latter frequency, the system oscillates in resonance. 'It will easily be :seen from the drawings that this .change of the frequency of oscillation and theincreaseof the amplitudedoes not cause .the piston to .abrnptly swing downwardly and to hit hard against the intermediate valve. The latter drawback is avoided due to the :fact that the increase of the amplitude takes :placesubstanti-ally upwardly, in the direction of a suctionzstroke.

The time needed for the change of oscillation-terse: in depends upon the size of the dampening spacera nd the correspondingly adjusted counter pressure. 'In the example described, this time .does not exceed a:few..seconds. The course of the oscillations of ith'earmature from the start to full operation .is demonstratedbyxthe time-distance curve in Figure 5. During ithecriticalina itial stages of operation, both the starting oscillations at net frequency and the dampening space. with its minimum pressure contribute essentially to prevent the pis-' ton from hitting the intermediate valve forming the cover of the cylinder chamber C. After the-change of oscillation frequency the piston 7 may-advance well into the cylinder bore 13b in piece 14, as long-as the maximum pressure of operation has not yet been attained, and the amplitude of oscillation is correspondingly great. In doing so, the piston 7 pushes the intermediate valve ahead of it "in a downward direction. However, the counter pressure and the gas cushion forming 'betweemthe bottom of the piston and the plateshaped intermediate valve prevent the piston from hitting the intermediate valve abruptly and with excessive force. Thus, any damage to the intermediate valve is avoided and undesirable noise is eliminated. The course-described by the piston in downwarddirection beyond the level of ledge 17, at low pressures, does not greatly increase the amount of work performed because of the dampening effect which the dead space D has on this part of the stroke. In order to keep the volume of the dead space D below the intermediate valve 16 as small as possible, the pressure valve 27 is subjected to an elevated tension, whereby the piston 7 is forced to counteract from the start a certain minimum bias pressure. of the pressure valve 27, the valve is to some extent relieved at mounting pressures within the pressure conduit 26. This relief effect continues until the pressure valve does no longer perform its closing function at the prescribed operational pressure. However, this has detrimental effects, because, at elevated operational pressures, the function of the pressure valve 27 is taken over by the intermediate valve 16.

'In this manner, it has become possible to achieve a high degree of efficiency with a simple construction of the compressor and over a wide pressure range, because the dead space can be kept very small without incurring the danger of having the piston hit the cylinder bottom if there is no or only a small counter pressure.

The invention will be more fully appreciated by the following example of a swinging compressor'which has been carried out in practice, and which was subjected to numerous successfultests and experiments. In this example, the subpoles have a width'of -13 mm., the recess between every two subpoles is 21 mm. wide, the width of the armatureis 14 mm. The total weight of the oscillating masses attains approximately 300 grams. The adjustment and adaptation to resonance is effected by twohelical springs each having a length of 70 mm. and having a spring constant of Z 3.1 kg./cm. The armature is so adjusted that its lower edge protrudes 0.5 mm. from the lower edge of the lower pair of subpoles. The natural frequency can be reduced from, for instance, a half frequency of 25 cycles of the AC. current supplied by the net down to cycles during idling.

The following effects were accomplished with the aforementioned construction: During the initial stage of operation of the piston oscillating at a frequency of 50 Because of the above described arrangement cycles; until the change of frequency to half frequency of -.25- cyclesthe work; performed was in the order of 2 litersper minute. After the change of frequency and at an excess pressure of from3 'to 4 atmospheres, the work performed-was-9.5 liters per min., at an excess pressure of 6 atmospheres 6 liters perrmin, and at an excess pressure of 13 atmospheres 1 liter per min. The ordinary operational pressures were approximately 6 to 8 atmospheres excess pressures. The oscillatory drive was fed from. a public A.C. current net of 220 volts. The exciting coils had 600 windings each and a diameter of the coil wire of 0.7 mm. The current received was 1.5 amp. at a frequency of 50 cycles and 1.2 amp. at a frequency of 25 cycles. The integrated power absorption of 55 :to watts was therefore surprisingly low.

'It will of course be understood that the invention is notflimited to the aforesaid. example which was given by wayof illustration only. It must particularly be kept in mind that the construction of the electro-mechanica'l oscillating system can be varied in more than one way without departing from the basically new concept of the invention. A few further, merely illustrative examples will demonstrate some of the ways in which the basic invention can be modified.

For example, the number and the arrangement of the teeth or subpoles of the poles at the magnet frame and the number of core disks of the armature may be varied at will as long as the difference between the number of the teeth of a pole, and the'number of armature disks is equal to one. Figure .6 shows schematically a magnet system comprising a compressor housing 43, a magnet frame 44, the poles 45, 46 of which are undivided and each carry one exciting coil C45 and C46 respectively. Upon the. shaft .48 of the armature there are mounted 2 disk-shaped armatures 49', 49" at such a distance from each other that the interstice 49a between them is situ- I ated in the resting position exactly opposite the stator magnet poles 45 and 46. In order to achieve the same effect as described further above, the upper armature 49' must be positioned at a smaller distance from the stator poles 45 and 46 than the lower armature 49". Again, two helical springs '50, 51 effect the adjustment and adaptation of the system. As shown in Figure 7, the poles and the armatures may be further subdivided. In the example shown in this figure, two armature disks 59' and 59"face the interstices of three stator pole teeth 55a, 55b, 550 of stator pole 55 and teeth 56a, 56b, 560 of the opposite stator pole 56. The positioning of the armature in front of the interstices must be carried out exactly in the manner shown in Figure 4. Figure 7 also shows that the adjustment and adaptation can be carried out by means of a helical spring 61 the ends of which are fastened at 62a to the armature disk 59 on the one hand, and to the compressor casing '53 at 62 on the other hand. The spring 61 can be subject to pressure as well as to tension. The exciting coil means need not be divided into separate coils for each pole as indicated in the previous examples; it is suflicient to use one single exciting coil C7, as shown in Figure 7, and to mount this coil on the yoke 54a of the U-shaped magnet core 54. The compressor cylinder 53a is enclosed in the casing 53. The oscillating system is guided in straight direction solely by means of the elongated compressor piston 57 reciprocating in cylinder 530.

In all these examples, the magnet frame is so arranged that its central plane i.e. the plane defined by the magnetic flux circuit, coincides with the plane determined by the axis of oscillation of the oscillator. It is also possible to have the axis of oscillation positioned vertically relative to the central plane of the magnet frame. This is the case in the magnet system shown in cross section in Figure 8 and in longitudinal section in Figure 9. In these figures, reference numeral 74 identifies the magnet core, 73 designates the compressor casing with the cylinder "(not shown), 78 refers to the oscillatory shaft, and

is of the double-acting type.

79 to the armature mounted thereon. A non-magnetic yoke 73a is fixedly attached to the magnet core 74 and acts as a guide means for the oscillatory shaft 78.

Another modification is shown in Figure 10. In this example the armature 69 revolves around its shaft 68 and its surfaces facing and opposed to poles 65, 66 of the magnet frame 64 are provided with teeth 69', 69". The exciting coils C65 and C66 are mounted uponthe legs of the U-shaped magnet frame 64. The adjustment of the armature is effected, for instance, by means of two springs 70, 71 each acting with their one end upon the arm 69c of the armature 69. Their respectiveother ends are attached to casing 63. In the resting positionof the armature 69 the interstices 69a between the teeth of each pair 69 and 69" are situated opposite to the poles 65 and 66 of the magnet frame. The adjustment of the springs 70 and 71 can be made to be asymmetrical and the oscillatory mechanical system is simultaneously, adjusted to half the exciting frequency. After starting at the exciting frequency, the system automatically changes to half the exciting frequency after a short period.

In this drive system, the compressor is preferably of the type of a wing or wing piston compressor (not shown) and it is connected with the revolving axis shaft 68.

A further alternative embodiment is illustrated by an example shown in Figures 11 to 13a. In these figures, the U-shaped magnet core 84 has two poles 85 and 86, each having two subpoles 8'5, 85" and 86, 86 subdivided by the interstices 85a and 86a. The armature 89 is fixedly mounted upon the shaft 88 to be rotated therewith and it is located between the surfaces of the poles 85 and 86 facing each other. The exciting coil 82 is wound around the yoke of the U-shaped core; Shaft 88 is formed by a torsion bar and thus replaces the springs usually needed for the adjustment of the resting position and the adaptation to resonance of the system. For this purpose, shaft 88 is firmly clamped in a socket 81 with its free left end (see Figure 12). This socket constitutes a part of the frame of the frame 83 which is connected at one of its ends with the magnet core 84 in a manner known per se. The other end of the frame 83 supports the casing 90 of a wing compressor. As shown in Figure 13, the frame can be adapted to form a uniform structure with the compressor casing 90. In that case the casing 90 is provided with two small bridges 94 reaching to the basis of the U-shaped core and firmly attached to the latter. However, this particular construction of the frame and the modes of attaching the same to the compressor and the impelling magnet are not considered parts of the present invention. As

the suitable solutions of the problems arising in this connection are well within the reach of persons skilled in the art, a detailed description is considered unnecessary.

The torsion shaft 88 is clamped in socket 81' at its left, free end, and its right end is prolonged beyond the armature and bears the revolving piston 91. The

various parts are connected with the shaft in a manner generally known in the art. For example, a shrink fit may be used, and the shaft 88 is provided with parallel longitudinal grooves at the connecting points. The r'evolving piston 91 has two wings 91a and 91b and moves within the cylindrical compressor space 93 of the compressor casing 90. The compressor space 90 is covered by the cylinder covers 95 and 96 at those ends which are connected, for instance by screw connection, to the casing 90. Two valve bodies 92a and 92b containing the pressure valves 97 are arranged within the compressor space in diametrical position relative to each other. They are fixedly connected with at least one of the. cylinder covers 95, 96. The construction of these valve bodies will be clearly recognized from the enlarged view thereof shown in Figure 13a. The wing compressor The suction conduits 98 and the pressure conduits 99 serve for the connection of the respective pipes which are connected to the com- 14 pression system, for instance a refrigerating installation, in a generally known manner. The armature 89 is mounted upon the shaft 88 in a position in which its poles 89a and 89b are located opposite to and facing the interstices a and 86a, if the torsion shaft is de tensioned; the position of the armature 89 relative to the interstices 85a, 86a is somewhat asymmetrical in order to facilitate the first oscillations. The Figures 11 to 13a show another position, namely the compression end position in which the poles of the armature are located in front of one of the pairs of subpoles of the magnet systemand in which the wings 91a and 91b are positioned close in front of the valve bodies 92a and 92b, respectively.

The system operates as follows: In the resting position the armature '89 stands facing the interstices 85a, 86a between the magnet subpoles, and the wings 91a and 91b of the compressor assume a horizontal position. Upon exciting the coils with half waves, the armature will be brought to the indicated position by the first half wave. The rotary piston 91 now turns counterclockwise and compresses the gas within the compression space located in front of the piston and into which the gas has been pressed via the valve bores 97a in the valve bodies, the pressure valves 97 and the pressure channels 99. By the revolving movement of the wings 91a, 91b, the orifices of the suction channels 98 are rendered accessible shortly after the commencement of the operation, and by the following movements the gas is sucked through these channels into the space behind the wings. Of course the suction pipes are provided with suction valves in a conventional manner in order to prevent the sucked gas from being pushed back into the suction channels during the return movement of the wings. For the sake of Elarity, these suction valves are not shown. The return movement of the wings back to their initial resting position, after the exciting half wave has subsided, is effected by the detensioning of the torsion shaft 88 originally tensioned by the first movement of the armature. The latter as well as the masses of the armature and the wings connected thereto are again adapted to a proper resonance corresponding to half the net frequency. Consequently, the armature 89 swinging beyond its resting position due to its kinetic energy assumes this position exactly at the moment in which the next half wave becomes effective. Thereby the armature 89 which just had moved counter-clockwise, is now moved to the other end position in which its poles 89a and 8% face the subpoles 85" and 86'. In the same manner, the wings 91a and 91b are brought to their other end positions in front of the other side of the valve bodies 92a and 92b. They thereby produce a compression stroke and simultaneously the suction stroke for the next following compression. Thus, the compression stroke already starts during the return movement of the wings from their respective end positions.

Only in order to show that the basic principles of the invention can also be applied to piston compressors driven by a rotating armature, another example is shown in the Figures 14, 15, 16 and 17. In this example, the magnet system is constructed as described, before and for that reason, the same reference numerals have been applied to the corresponding elements. Only the exciting coil is subdivided into two equal subcoils 82a and 82b.

The exciting coil is mounted close to the poles upon the magnet frame 84. The magnet frame 84 is connected with a frame 103 which is U-shaped and has two legs 103a and 103b, the latter forming the bearings for the shaft 88 of the armature 89, on both sides of the magnet system. A three-armed T-shaped lever 104 is firmly connected with the axis 88 and provided with a downwardly extending leg 104a provided at its lower end with an elongated slot 105. The lower end of the lever is embraced by the fork-shaped end 1061: of the piston rod, or-as shown in the drawingsthe compressor 15 piston 106 itself. It is displaceably connected with the latter by means of a bolt 107 extending through the elongated slot 105. The compressor piston 106 cooperates with the cylinder 108, the latter being shut by the cylinder cover 109 containing the pressure valve and the suction valve in the usual manner. The two substantially horizontally extending legs and 104a are recessed at the back of'their respective lower ends at 112 and 113,. each recess receiving the ends of two helical springs 110 and 111 respectively. The other ends of these springs rest against corresponding protrusions IE4 and 115 respectively, of the cylinder 198 and the frame .103, respectively. These springs adjust the armature to its resting position, reset the same and adapt the entire oscillating mechanical system to the resonance frequency corresponding to half the exciting frequency.

Figures 14 to 17 show the entire construction in a position corresponding to the end of the suction stroke.

This construction operates in the samemanner as decribed for the example shown in Figure 10 as to the electrical operation, and as described for the example shown in Figure 4 as to the compressing operation.

It will be clearly understood from the examples heretofore described that many other modifications can be devised by any person skilled in the art. The invention is particularly susceptible to be used, for all sorts of pumps and compressors advancing or compressing air or other gases.

The invention has proved to be particularly useful if applied to refrigerating compressors-in refrigerators md especially household refrigerators. The invention offers a simple, sturdy and particularly noiseless compressor having a long life time and consuming a minimum of energy. v y

it will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What I claim is:

l. in an electro-mechanical system combining an electro-magnetic oscillating system comprising a stationary I electro-magnetic member, an oscillating member, and pole means associated with each of said two mnembers and comprising pole portions facing each other, with a fluid-conveying mechanical machine driven by saidoscillating member the combination of rectifying means for exciting said oscillating system with half waves derived from an electrical alternating current source, a plurality of pole portions forming the pole means of at least one of said two members, the difference between the number of pole portions associated with each of said two members being one, means for maintaining said oscillating member when at rest, in such a position relative to said stationary electro-magnetic member that the pole teeth of the pole means of one of said members face the interstices between the pole teeth of the pole means of the other of said members, the first of saidhalf waves thus forcing said oscillating member into the first end position and the following of said half waves forcing said oscillating member into the second end position, and means-for adjusting the oscillating system to a natural resonance corresponding to half the frequency of the A.C. current obtained from said electrical alternating current source, said fluid-conveying mechanical machine comprising a piston, an elongated cylinder for said piston, and a plurality of pressure pipes, said elongated cylinder comprising a cylinder and an intermediate piece,

said intermediate piece prolongating said cylinder, an

intermediate valve, said intermediate valve being arranged within said elongated cylinder at the point of reversal of said piston, said intermediate valve dividing the interior space of said elongated cylinder into a compression space in which said piston shuttles back and forth and 'a dampening space, further comprising a presi6 sure valve, said pressure valve shutting said dampening space. against said pressure pipes except for a minimum pressure allowed within said dampening space and against which the piston has to act.

2. The improved system asdescribed in claim 1 wherein said intermediate Valve covers the entire interior diameter of said cylinder and is adapted for being pushed ahead by the piston in case of large amplitudes of oscillation.

3. In an electro mechanical system as described in claim 1, the step of tensioning said pressure valve in accordance with the prevailing operational atmospheric pressure of said fluid-conveying mechanical machine, thereby adapting the minimum pressure in said dampening chamber against which said piston of said fluid-conveying mechanical machine has to act to the operational pressure of said compressor.

4. An electro-rnechanical system comprising, in combination: an electro-magnetic oscillating system comprising a stationary electro-magnetic member, an oscillating member, pole teeth connected with one of said two members, and spaced pole portions which face each other to form an interstice andwhich are connectedwith the other of said two members; a mechanical fluid conveying device driven by said oscillating member and having an operational frequency equal to that of said oscillating member; means for exciting said oscillating system with half waves derived from an electrical alternating current source, said oscillating system being adjusted to a natural resonant frequency equal to approximately half the frequency of the alternating current source; and means for resiliently maintaining said oscillating member, when at rest, in such a position relative to said stationary electro-magnetic member that said pole teeth of said one member are arranged asymmetrically in said interstice between said facing pole portions of said other member sothat when said exciting means excite said oscillating system, said pole teeth of said one member and said facing pole portions of said other member are displaced relative to each other in such a manner that during the time in which a counterforce is built up in the fluid conveying device, said oscillating member is forced in the same direction by each of the half waves, oscillating between one end position and approximately the position of rest with the amplitude of oscillation building up gradually until a point is reached at which said oscillating member is, at'the moment at which a new half wave begins, nearer to the other end position whereupon such new half wave will cause said oscillating member to be attracted toward said other end position so that from this point on said oscillating memher will oscillate between the two end positions, whereby said oscillating member initially oscillates at the frequency of the alternating current supplied'by said alternating current source and then, when said last-mentioned point is reached, automatically changes to an operational frequency which is half the frequency of said alternating current source, so that from said last-mentioned, point onward, the frequency of suction and discharge strokes of said fluid conveying device is equal to half the frequency of said alternating current source.

References Cited in the file of this patent UNITED STATES PATENTS

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