US3390674A - Inflatable mattress with fluid amplifier - Google Patents

Description

July 2, 1968 D. R. JONES 3,390,674

INFLATABLE MATTRESS WITH FLUID AMPLIFIER Filed May 28, 1965 INVENTOR DONNIE ROLAND JONES ATTORNEYS United States Patent 3,390,674 INFLATABLE MATTRESS WITH FLUID AMPLIFIER Donnie Roland Jones, Silver Spring, Md., assignor to Bowles Engineering Corporation, Silver Spring, Md., a corporation of Maryland Filed May 28, 1965, Ser. No. 459,705 7 Claims. (Cl. 128-33) ABSTRACT OF THE DISCLOSURE An inflatable mattress having a first group of inflatable sections isolated from and interleaved with a second group of inflatable sections, each group being connected to a respective fluid conduit. The conduits receive fluid flow from a respective pair of output passages of a pure fluid bistable element of the type which normally maintains its binary state irrespective of output passage backloading. A feedback passage extends from each output passage to a respective control nozzle of said bistable element for providing signals to change the binary state of the element whenever each group of inflatable sections is inflated sufliciently to produce a predetermined back pressure in its associated output passage.

The present invention relates to inflatable mattresses and similar types of body supports and, more particularly, to an inflatable mattress or body support and a control therefor such that the areas of support of the body may be cyclically altered so that no area of high pressure between the body and the support is maintained for an in definite length of time thereby resulting in increased comfort for the user.

It was determined some years ago that one of the contributing factors to bed sores in bedridden and substantially immobile patients resulted from sustained areas of high pressure contact between a mattress and the body of the individual. In order to overcome this difficulty, it was suggested that a mattress be provided having a plurality of generally parallel air passages with, for instance, the odd number of passages connected to a first manifold and the even number of passages connected to a second manifold. Timing means were employed to connect the two manifolds alternately and cyclically to a source of air pressure so that adjoining segments or passages were alternately expanded and exhausted. Such an arrangement effected a cyclic shifting of the body support areas, thus eliminating sustained high pressure contact between the body of the user and the support.

Such mattresses have been found to be quite satisfactory in preventing bed sores, but the dilficulty with such apparatus is the relatively high cost due to the large number of mechanical parts required in the control mechanism to effect the desired cycling of air to the two manifolds. In one typical such prior art device, the mechanical components required, in addition to a motor and pump, were two spool valves, one shuttle valve, two check valves, one timer motor with cam and two cam followers.

In accordance with the present invention, all of the above mechanical components may be replaced by a single pure fluid flip-flop of such construction that, in conjunction with the air mattress, the flip-flop operates as an oscillator. The oscillator frequency dependson the nozzle size and can be designed to cycle from a few seconds or less to several minutes, limited only by the mechanical construction technique.

A pure fluid flip-flop is a fluid element having two stable states. A stream of fluid is issued by a power nozzle through an interaction region towards two fluid receiving passages. In a typical such device sidewalls, em-

Patented July 2, 1968 ice ploye'd to define the lateral sides of the interaction region, are located such with respect to the power nozzle that, when the stream is directed to one of the output passages, a boundary layer develops between the adjacent sidewall and the stream to maintain the stream in its deflected position. An input flow of fluid may be provided to switch the stream to the other output passages and again, a boundary layer is developed between the power stream and the other sidewall to maintain the stream deflected to the second output passage.

Boundary layer fluid amplifiers may be made either sensitive or insensitive to load on the output passages. More particularly, a device may be made such that, if the passage is heavily loaded, the stream, after an initial deflection to an output passage, is deflected to the other output passage due to backloading. Alternatively, the device may be made insensitive to the load so that, once the stream is directed to an output passage, it remains directed to this passage regardless of the load. The present invention employs the latter type of boundary layer unit; that is, one which is insensitive to the load on the device.

Initially, it was attempted to employ a flip-flop sensitive to backloading such that, when a stream is initially deflected to one output passage and is conveyed by suitable means to one of the manifolds of the mattress, the stream maintains its deflection to this output passage until all of the passages in the mattress associated with the aforesaid manifold are substantially completely inflated. At this time, the load on the output passage is greatly increased above that which is present when the stream is initially deflected to this first output passage. As a result of the increase in load, the flip-flop is caused to switch to the other output passage and air is now supplied to the second manifold and through this manifold to the second plurality of passages in the mattress. The second plurality of passages begins to inflate, while due to the loss of pressure in the manifold associated with the first plurality of passages in the mattress, these passages begin to deflate. The air from this first plurality of passages may be entrained in the power stream and now transferred with the power stream to the second output passages and thence to the second plurality of passages in the mattress. When the second plurality of passages in the mattress become fully inflated, the second output passage of the flip-flop is suiliciently backloaded to produce switching of the flipflop and this power stream is now deflected to the first output passage and the cycle is repeated. It was found, however, that with this type of unit it was difficult to obtain full inflation of the mattress passages and at the same time insure switching of the power stream.

It has been found that the above difliculties may be overcome by employing a flip-flop insensitive to load changes and utilizing two feedback passages to effect switching. More particularly, the flip-flop is provided with two control nozzles on opposite sides of the power stream. Each of these control nozzles is connected through a passage to a point near the adjacent output channel of the flip-flop. When a stream is deflected to a particular output passage, its movement past the inlet orifice to the feedback channel tends to extract fluid from this channel and the reduced pressure thereby produced is transmitted through the feedback passage to the boundary layer region between the stream and the associated wall. This tends to further reduce the pressure in this area and thus increase the boundary layer effect and consequently the lock-on effect on the stream. However, as the passage becomes backloaded due to the mattress passages becoming nearly fully inflated, the static pressure in the output passage begins to build up and is transmitted through the feedback channel to the control nozzle rapidly increasing the pressure in a boundary layer region and assisting in a rapid breaking of the boundary layer effect. Therefore, switching of the power stream may be effected at a relatively precise pressure due to backloading of the stream. Specifically, rate of flow of fluid adjacent the sidewall remains relatively constant, maintaining a relatively constant differential in pressure across the power stream. It follows that a specific pressure and consequent flow must be applied to the control nozzle to switch the power stream. This specific pressure can be obtained only after the mattress passages have achieved a predetermined degree of inflation and thus controlled switching is obtained.

It is an object of the present invention to provide a pure fluid flip-flop for alternately and cyclically inflating alternately arranged air cells in a mattress or the like which flip-flop when connected to the mattress operates as a low speed oscillator.

It is another object of the present invention to provide a pure fluid control for mattresses or similar body support devices having alternately arranged inflatable passages which flip-flop device is inexpensive to manufacture and trouble-free in operation.

It is another object of the present invention to employ a pure fluid flip-flop with a mattress or similar body support having alternately arranged isolated inflatable air passages which flip-flop when connected to the mattress operates as an oscillator having a highly reliable and stable cycle of operation.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic illustration of a bistable flip-flop with feedback which may be employed to drive the mattress of the present invention;

FIGURE 2 is a diagrammatic illustration of the apparatus .of FIGURE 1 connected to an inflatable mattress; and

FIGURE 3 is a schematic view of the mattress of FIG- URE 2 in elevation showing alternately arranged inflated and deflated portions.

Referring now specifically to FIGURE 1, there is illustrated a pure fluid flip-flop generally designated by the reference numeral 1 which may be employed in accordance with the present invention to operate a mattress having alternately arranged groups of inflatable air passages adapted to be inflated out-of-phase with one another.

The flip-flop comprises a power nozzle 2 for directing fluid through an interaction region 3 towards two output passages 4 and 6. The interaction region is defined along its left and right sides by sidewalls 7 and 8. The sidewalls are positioned relative to the centerline of the nozzle 2 such that, when a stream is deflected to one of the .output passages, a low pressure boundary layer reigon is developed between the stream and one of the sidewalls to maintain the stream locked to the adjacent sidewall.

More particularly, if the stream issued by the nozzle 2 is initially deflected, for instance, to the passage 4, it will be noted that the stream passes relatively close to the wall 7. The rapidly moving stream tends to evacuate, entrain, the fluid existing between the stream and the sidewall 7 at a far more rapid rate than it can evacuate the fluid from the remainder of the interaction region 3 which is, under these circumstances, quite large relative to the region existing between the stream and the sidewall 8. Thus, the pressure in the region between the stream and the sidewall 7 is considerably less than the pressure in the remainder .of the interaction region. This differential in pressure maintains the stream directed towards the output passage 4.

As previously indicated, the flip-flops are of two types: those which switch due to backloading and those which do not switch, even though fully backloaded. The flip-flop 1 .of FIGURE 1 is of the type which does not switch due to backloading and, more particularly, is known as a flip-flop having memory. The ability of the stream to remain switched to the passage 4 in spite of backloading results from several factors such as the length of the interaction region 3, the placement of sidewalls 7 and 8 and other factors now to be discussed. The outlet passages 4 and 6 are defined in part by extensions of sidewalls 7 and 8 and by a divider 9, which in this particular instance, is symmetrical with the centerline of the nozzle 2. The distance of the downstream end 11 of the divider 9 from the egress orifice of the nozzle 2 is one factor in determining the ability of the device to remain locked to a wall in the presence of load. A cusp 18 formed at the upstream end of divider 9 creates a vortex flow in such a direction that the flow in the vertex is directed against the side of the stream remote from the sidewall to which the stream is attached and thus, further enhances the differential pressure across the stream.

In addition, a small booster region 12 is provided between the egress orifice of the nozzle 2 and control passages .13 and 14 to be discussed subsequently. The sidewalls of the booster region 12 are close to the power stream and a boundary layer effect is established between the power stream and the sidewall of the booster region along the side of the device to which the stream is deflected. This region is substantially completely isolated from the output passages 4 and 6 and the loads thereon and therefore tends to maintain the stream in the position directed regardless of load.

The device is also provided with a pair of vents 16 and 17, the purpose of which is to vent excess fluid provided to a passage after the passage is blocked. If, for instance, the stream is directed to passage 4 and the passage can accept no more fluid due to blockage, the power stream being locked to sidewall 7 continues to deliver fluid to the passage. A flow path must be supplied for this excess fluid and in the absence of the vent 17, the fluid would be directed to output passage 6, pressurizing this latter passage, an undesirable effect. The vents 16 and 17 provide passages for the excess fluid and thus permit the passage 6 to remain at a low pressure.

As stressed above, the flip-flop of FIGURE 1 is a memory type unit which will not switch on backload and in order to effect switching, the apparatus is provided with a pair of feedback channels 19 and 21. The channels 19 and 21 operate under one condition of flow as positive feedback channels and under another set of conditions operate as negative feedback channels. Specifically, when the stream is initially directed to the channel 4, the rapid movement of air past the upper end of the passage 19 which, for purposes of explanation, is designated by the reference numeral 22, extracts air from the passage and thus withdraws further fluid from the boundary layer region through the control nozzle .13. In order to accomplish this result, the passage 19 preferably enters the output channel 4 at an angle of betwen 0-90. At a greater angle, some of the fluid flowing through the output channel tends to enter passage 19 and defeat the positive feedback effect. Thus, upon initial deflection of the stream, the feedback channel 19 operates as a positive feedback channel be cause it enhances the boundary layer effect. Upon the passage 4 becoming sufliciently backloaded to substantially raise the pressure in this passage, the flow past the opening 22 is stopped so that fluid can no longer be extracted from the passage 19. In addition, the increase of pressure in the channel 4 is transmitted through the feedback passage 19 and the nozzle 13 into the boundary layer region between the stream and the sidewall. By this process, the pressure in this region is raised above the pressure in the remainder of the interaction region 3 and the stream is caused to switch to the passage 6.

The device is completely symmetrical and therefore the cycle repeats itself. Thus, if the passages 4 and 6 are equally and alternately backloaded, a symmetrical cycle of operation is effected and the device switches any rate determined by the fluid capacity of the load and the power stream pressure and flow rate. If the passages 4 and 6 were blocked at the ends where they are ended in FIGURE 1, the switching rate would be quite great. However, if the capacity of the load is quite large, then the switching rate is low. Regardless of the load, however, switching occurs at a precise pressure in the output passages 4 and 6 due to the use of the memory type unit with the feedback passages 19 and 21. More particularly, the flow past the sidewall lock-on region as designated by reference numerals 7 and 8, due to the presence of the vent passages 16 and 17, remains at a relatively high rate and is relatively independent of the size of the load. Thus, the reduced boundary layer pressure is relatively constant and switching must depend upon the pressure in the output passages achieving a specific value such that suflicient fluid issues through the control nozzles 13 and 14 to break the boundary layer effect.

Referring now specifically to FIGURES 2 and 3 of the accompanying drawings, there is illustrated the pure fluid flip-flop 1 connected to a mattress generally designated by the reference numeral 23 with which the flip-flop is to be employed. The mattress comprises a first plurality of inflatable passages 24 arranged in alternating relationship with a second plurality of inflatable air passages 26. The passages 24 are connected through a manifold 27 to output passage 6 of the flip-flop 1 while the passages 26 are connected via a manifold 28 to the output passage 4 of the flip-flop 1.

In operation, the power nozzle 2 is connected to a source of air pressure and, for instance, fluid is initially directed to the passage 4. As seen in FIGURE 3, the flow to the passage 4 produces inflation of the interconnected air passages 26 while the pressure in the passages 24 which are arranged in alternation with the passage 26 is greatly reduced and these elements become substantially flat. In consequence, the weight of the body of the user is supported on the upper layer of material defining the passages 26. After the passage 26 becomes substantially fully inflated, back pressure in the passage 4 increases and produces switching via the feedback channel 19.

Air pressure is now supplied through the manifold 27 to the passages 24 and these passages assume the shape of the passage 26 as illustrated in FIGURE 3 while the passages 26 are deflated and assume the illustrated shape of the passages 24. Thus, the body of the user is now supported on the upper surface of the material defining passages 24 and the areas of prior contact between the material defining passage 26 and the body is now under considerably lesser pressure which is a desirable feature in the elimination of bed sores.

Referring again to FIGURE 2, it will be noted that the feedback lines 19 and 21 have restrictions 27 and 28 formed therein. These restrictions are necessitated by the gain of the unit. Specifically, a flip-flop has pressure gain. The mattress 23 must support a person and as such, a pressure of, for instance, 1 to 2 p.s.i.g. must be supplied to the mattress and thus appears in passages 4 and 6. Due to gain of the flip-flop, pressures of only 0.1 to 0.2 p.s.i.g. are required to switch a power stream capable of producing pressures of 1 to 2 p.s.i.g. in the mattress. Thus, the restrictions 27 and 28 are required to drop the pressure at the control nozzles 13 and 14 to the proper value.

The cycle of operation is preferably slow, occurring every two-and-a-half-to-three minutes. As indicated above, the frequency is determined by the size of the nozzle 2 and therefore a unit may be designed for any desired frequency within reason, of course.

An important feature of the present invention is the ability of the apparatus to be employed where there is no electricity available or it is not desired to operate the apparatus from an electrical supply. More particularly, the flip-flop 1 connected to the mattress may be operated from a compressed air source such as bottled compressed air or the compressed air supplies in hospital rooms which supplies are found in the more modern hospitals. Thus, the motor and pump may be eliminated and, in consequence, the element 1 may be attached directly to the mattress and form a composite part therewith.

The apparatus is not necessarily limited to utilization with mattresses. It may be employed for pads in automobiles, particularly in trucks where a ready supply of compressed air is available from the air-brake compressor. The apparatus may also be employed in automobiles by providing a small pump motor driven from the 12-volt supply found in the standard automobile today. Thus, the apparatus is completely portable and, in many instances is completely independent of electricity where compressed air supplies are available. As previously indicated, the fluid flip-flop is quite light, relatively simple to manufacture. A typical fluid flip-flop may be less than two inches along each side and less than one inch thick, its weight amounting to less than a pound.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. An inflatable mattress or the like and control therefor comprising a mattress having at least a first group and a second group of inflatable regions, the inflatable regions of said first group of inflatable regions being generally interleaved with and isolated from the inflatable regions of said second group of inflatable regions, a first fluid flow means connected to supply fluid to said first group of inflatable regions, a second fluid flow means connected to supply fluid to said second group of inflatable regions, a pure fluid bistable element having an interaction region, at least a first output passage and a second output passage, a power nozzle for issuing a power stream of fluid through said interaction region toward said output passages, means connecting said first and second output passages to said first and second fluid flow means, respectively, first means responsive to inflation of said first group of inflatable regions for switching the power stream from said first output passage to said second output passage, and means responsive to inflation of said second group of inflatable regions for switching the power stream from said second output passage to said first output passage.

2. An inflatable member and control therefor comprising an inflatable member having at least two inflatable regions isolated from one another, a firs-t fluid flow means connected in fluid flow relationship to a first of said inflatable region, a second fluid flow means connected in fluid flow relationship to a second of said inflatable regions, a pure fluid bistable element having an interaction region, at least a first output passage and a second output passage, a power nozzle for issuing a power stream of fluid through said interaction region toward said output passages, means connecting said first and second output passages to said first and second fluid flow means, respectively, first control means responsive to inflation of said first inflatable region for switching the power stream from said first output passage to said second output passage and second control means responsive to inflation of said second inflatable region to switch said power stream from said second output passage to said first output passage.

3. The combination according to claim 2 wherein said first control means comprises a first feedback means responsive to pressure in said first output passage for issuing fluid into said interaction region in such a sense as to deflect said power stream from said first output passage to said second output passage.

4. The combination according to claim 3 wherein said second control means comprises a second feedback means responsive to pressure in said second output passage for issuing fluid into said interaction region in such a sense as to deflect said power stream from said second output passage to said first output passage.

5. The combination according to claim 4 wherein said flip-flop includes a first control nozzle disposed on the same side of the centerline of said power nozzle as said first output passage, and a second control nozzle disposed on the same side of the centerline of said power nozzle as said second output passage, said first feedback means extending between said first output passage and said first control nozzle and said second feedback means extending between said second output passage and said second control nozzle.

6. The combination according to claim 5 wherein said sages at an angle such that movement of the power stream through one of said output passages extracts fluid from its associated feedback means.

7. The combination according to claim 4 wherein said pure fluid bistable element is of the type in which switching is insensitive to backloading of said output passages in the absence of said first and second feedback means.

References Cited UNITED STATES PATENTS 2,460,245 1/1949 Summerville 12833 2,684,672 7/1954- Summerville 128-33 3,098,504 7/1963 Joesting 137-624.14

feedback means enter into their respective output pas- 1 L TRAP? Primary Examiner

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