US 3136075 A
Description (OCR text may contain errors)
June 9, 1964 M. BRIAN 3,136,075
ARTICULATED CENTRIFUGE Filed Feb. 25, 1962 5 Sheets-Sheet 1 IN V EN TOR.
me'd lae/ Brian,
ATTORNEY June 9, 1964 M. BRIAN ARTICULATED CENTRIFUGE 5 Sheets-Sheet 2 Filed Feb. 23, 1962 INVENTOR. mic/me! Bryan ATTORNEY June 9, 1964 M. BRIAN ARTICULATED CENTRIFUGE 5 Sheets-Sheet 3 Filed Feb. 23, 1962 INVENTOR. mic/zae/ B/z'a/z V. B Q
nw 3 R ATTORNEY June 9 1964 M. BRIAN 3,136,075
ARTICULATED CENTRIFUGE Filed Feb.- 23, 1962 5 Sheets-Sheet 4 lllll ll IN V EN TOR.
mic/me! Brian ATTORNEY 3,136,075 ARTICULATED CENTRIFUGE Michael Brian, Utica, Mich, assiguor to Republic Aviation Corporation, Farmingdale, N.Y., a corporation of Delaware Filed Feb. 23, 1962, Ser. No. 175,209 15 Claims. (Cl. 35-12) This invention relates generally to centrifuge devices and more particularly to an articulated centrifuge device by which rapid accelerations and decelerations are attained at and/or maintained for precise periods of time.
tions and decelerations, including controls to initiate and permit the operation of such means.
More specifically, the invention contemplates the mounting of an articulated centrifuge for controlled rotation about multiple axes disposed in different planes. The centrifuge is so organized and arranged that it is capable of rotating about a selected single axis or simultaneously rotating and bodily swinging about the several axes in selected sequences at controlled velocities.
To the above ends, the centrifuge proposed hereby comprises a primary arm rotatably mounted on stationary structure and a secondary arm rotatably mounted medially of its length on the primary arm adjacent the outer end/thereof. A gondola is pivotally' mounted at one end of the secondary arm for controlled rotation relative to the primary and secondary arms. The length of the secondary arm is such that, when rotating relative to the primary arm, an axis of the gondola scribes a circle that intersects the primary or stationary pivot or axis of the centrifuge.
Releasable lock means is provided between the gondola and stationary structure that is operable when the axis of the gondola is aligned with the primary pivot of the centrifuge whereby the primary and secondary arms may be rotated as a unit about the primary pivot and gondola.
'Upon release of the lock means, however, the primary and secondary arms are free for relative rotationon their respective pivots. In order to control this relative rotation, releasable differential means in included between the primary and secondary arms.
By means of the foregoing structure, predetermined g loads, as well as instantaneous onset loads, may be applied to persons and/ or equipment carried within the 3,136,075 Patented June 9, 1964 "ice FIG. 2 is a side elevation thereof with parts broken away to show the pivotal connection between the primary and secondary arms of the centrifuge as well as the pivotal connection of the primary arm to stationary mount-v ingvand supporting structure shown in section;
FIG. 3 is a section taken along line 3--3 of FIG. 2 to show'the articulated centrifuge per se in plan elevation;
FIG. 4 is a perspective view of the gondola and a frag- .ment of its associated supporting structure and drive mechanisms partly in section to show its mounting for rotation relative to the primary and secondary arms;
FIG. 5 is a section of one of the drives between the gondola and its supporting structure;
FIG. 6 is a fragmentary detail largely in section of engagement means by which the gondola is releasably secured against rotation relative tow the stationary mounting and supporting structure for the centrifuge and showgondola. Moreover, by combining and synchronizing the rotation of the primary and secondaryarrns and the gondola, a variety of effective gyration patterns may be attained that correspond to andsiinulate various'flightconditions' of vehicles wherebyv informative .data thereon .under such conditions may be obtained. 7
With the .above and other .Objects in view, as will he apparent, this invention consists in the construction, combination and arrangement of parts, all as-hereinafter more fully described, claimed and illustrated in the accompanying the control for the operation of said means;
FIG. 7 is a schematic view illustrative of the apparatus and one of the gyration patterns of the articulated centrifuge, i .e., the gyration pattern of the gondola, when the apparatus swings simultaneously about its multiple axes;
FIG. 8 is an electrical wiring diagram of the control circuits by which selected operating sequences of the articulated centrifuge are effected and a predetermined yration pattern of the gondola is produced.
Referring more particularly to the drawings, 10 .designates the primary arm of the articulated centrifuge formed in an open frame by a pair of parallelly disposed,
spaced, structural members or beams 11 and 12 The beams 11 and 12 are interconnected at one end by a transverse beam 13 to define a generally rectangular area 14. Mounted on and carried by the primary arm or frame 10 adjacent the beam 13 and projecting. outwardly of the arms 11 and-12 and area 14, is a pair of aligned trunnion 7 members 15 and 16. When the beam 13 is disposed in a vertical position perpendicular to a supporting surface 17 (FIG. 2), the arms-11 and 12 are located substantially parallel to such surface 17.
Thus disposed, the frame 10 is supported on the surface 17 through the trunnion 16 rotatably mounted in an annular su orting stanchi nlfi pp op e y an ed to the surface 17 through connectors 20. The frame 10 is. additionally supported onthe surface '17 .th r ough the trunnion 1,5 is rotatably mounted. The several stan- ,chions 18.,and associated endsof the spider. 22 may be structurally reinforced by suitable means, such as gussets 23. The length of the stanchions 18 and 19 and the beam 13 are suchas to locate the inner surface of, the spider 22 and the louter edge. of the stanchion 19:.in spaced rel tion t he arms .1 and 12, respe ti e y. f the-f ame 10 when thet unni us are ro a ab y m m d t s nxas descri Th runn on 15 a d 16 t olmt ou- Lstitut th pri y p ot of t e f ge I [The endsof the arms .11 andJlZ a ja ebs 3 are eonnected to respectiye extension beams 24 which converge outwardly and are integrally connected one to the other *to receive and mount a power unit o r thrust device,..such as a jet engine 2 5 ./An 'appropriate fuel ontain r 26is as at d h the eng n .25,"and.e' .0;1+ n s ng d li e 27 and u lcont o rd v ce 2, r l a e the flow of fuel from the tank .to theenginehfor its. operation.
Ope io f the e g ne 5 r ult n th rota n of'the entire frame 10 on its trunnions 15 land 16; rela-ya: tive to the surface 17 and the stationary supporting stanchions 18 and 19. Suitable reverse thrust means (FIG. 3) is incorporated in the engine 25 to facilitate in bringing the frame '10 to rest when desired. Such a reverse thrust means that may be employed for this purpose is fully disclosed in Patent No. 2,945,346, issued July 19, 1960, to Henry E. Arnzen. Generally, this thrust device comprises actuator means connected to a pair of coacting doors pivotally mounted in the exhaust duct for movement by the actuator to and from extreme positions transversely of and parallel to the duct. In the transverse position of the doors, side outlets provided in the wall of the duct are opened thereby for the diversion of exhaust gases therethrough. In the parallel position of the doors, on the other hand, the side outlets in the duct wall are closed thereby and the exhaust gases are discharged rearwardly for normal operation of the engine.
At their outer, unconnected ends, the arms 11 and 12 l are pierced by aligned openings adapted to receive and rotatably mount therein a pair of trunnions 29 and 30 projecting medially from opposed sides of the secondary arm of the articulated centrifuge, i.e., a carrier 31. The carrier 31 is thereby mounted for free rotation in the frame 10, and the trunnions 29 and 30 thus mounted constitute the secondary pivot of the centrifuge.
The opposed ends of the carrier 31 terminate in bifurcations 32 and 33, each adapted to receive a band 34 pivotally secured thereto through diametrically opposed studs 35 projecting integrally therefrom. These bands 34 are each connected to the periphery of a container or pod 36 and 41, which pods may be identical one to the other. For this purpose, at least one of the bands 34,
for example, the band associated with pod 41, is in the 7 form of a channel 37 (FIG. 4) opening inwardly thereof and adapted to receive and rotatably mount a ring gear 38. Localized, diametrically opposed projections 39 are formed or otherwise provided on the inner periphery of the ring gear 38, each terminating at its end in a rotatable bearing 40 provided on the associated pod 41. An access opening with a removable closure 42 which may, if desired, be transparent is provided in each of the pods 36 and 41.
Adjacent the bite of one or both of the bifurcations 32 and 33, the band 34 is perforated as at 43 whereby the teeth of the ring gear 38 are exposed for coacting engagement with a pinion gear 44 mounted on and projecting from a fixed bracket 45 carried by the associated bifurcation 33. Thus, rotation of the pinion gear 44 drives the ring gear 38 and the connected pod 41 in a plane substantially parallel to the surface 17.
At right angles tothe bearings 40 in the pod 41 are similar diametrically opposed bearings 46 adapted to mount and connect a second ring gear 47 to the surface of the pod. A pinion gear 48, similar in all respects to the gear44, is mounted .on and projects from a bracket 49 carried by the adjacent bifurcation 33 with its teeth projecting into for coaction with the teeth of the gear 47 whereby rotation of the pinion gear 48 drives gear 47 and the attached pod 41 in a plane normal to the surface 17. Thus, the pod 41 is'mounted at one end of the carrier 31 for substantially universal movement relative to the carrier. The effective length of the carrier 31 issuch that the vertical axis of the pod 41 intersectsand is disposed in coincidence with the axis of the trunnions 15 and 16 upon each revolution of the carrier on its trunnions 29 and 30, for purposes to become more apparent.
Referring momentarily to FIG. 5, the drive mechanism for the pinion gear 44 is illustrated, it being understood, that a similar mechanism may be employed in connection with the gear 48. The gear 44 comprises a pair of races 49 and 59 separated by suitable roller means 51. The race 56 is secured to and forms, in effect, an integral part of the associatedbracket 45, while the race 49 from which the pinion gear teeth project is rotatable relative thereto. The adjacent faces of the races 49 and 50 are provided with rotor and stator elements 49' and 50', respectively, whereby rotation is effected upon the generation of a current therethrough. Through operation of this drive mechanism, the pod 41 is rotated either horizontally or vertically for purposes of adjusting the attitude thereof as well as for spinning it about either of its axes.
For the purpose of securing and releasing the pod 41 for such operation relative to the carrier 31 and frame It a releasable locking mechanism 52 is provided. This mechanism is secured to the supporting surface 17 projecting therefrom through the annular stanchion 19. It comprises a vertical support 52' and terminates in springloaded plunger means 53 (FIG. 6) normally operative to engage coacting means carried by a boss 54 formed or otherwise provided on the associated portion of the pod 41. While only a single boss 54 has been illustrated, it is to be understood that several such bosses 54 may be employed, one located in a position on the pod corresponding to each position of its adjustment. The plunger means is connected to a reciprocable rod 55 which .constitutes the core of a solenoid 56 whereby the plunger is compressed against its normal action when the solenoid is energized and releases the pod 41 for movement relative to the carrier 31 and frame 10.
In view of the foregoing construction and arrangement of the apparatus, operation of the engine 25 produces thrust, rotating the frame 10 and carrier 31 about the primary pivot, i.e., the trunnions 15 and 16. When the carrier 31 and the frame 10 are thus rotated and the lock mechanism 52 is engaged to secure the pod 41 in a fixed position relative to the supporting surface 17, the gear 47 being connected to the carrier 31 through the pinion gear 48 is carried with it, rotating about the pod 41 on the bearings 46. At the same time, the ring gear 38 is relatively immovable with the pod 41 while the band 34 rotates with the carrier 31 and the pinion gear 44 operates ineffectively around the gear 38.
Releasable connection means is provided between the carrier 31 and the frame 10 whereby the former may be positively driven at a selected speed relative to that of the latter. For this purpose the annular stanchion 19 is formed adjacent its outer or upper end with a fixed, peripheral gear 57 which projects therefrom. The adjacent trunnion 30 on the carrier 31 is formed with an extension 58 on which a pinion gear 60 is rotatably mounted, as at 59. The teeth of gear 60 are disposed at all times in meshing cooperation with the teeth of the gear 57. Concentric with the gear 60, on the trunnion extension 58 is a reciprocable clutch 61 and biasing means 62 operative to maintain the plates of the clutch 61 engaged whereby rotation of the pinion gear 60 in unison with the frame 10 normally imparts movement to the carrier31.
Associated with the biasing means 62, however, is a solenoid 63, the energization of which serves to overcome the operation of biasing means 62, causing disengagement of the plates of the clutch 61 whereby subsequent rotation of the gear 60 transmits no movement to the carrier 31. To this end, the solenoid 63 is mounted within the carrier 31 adjacent the trunnion 30, and its core extends through a bore in the extension 58 provided therefor. At its outer end, the core terminates in a laterally projecting pressure plate 63' disposed between the clutch plates 61 and spring 62. Thus, when the solenoid is energized, the core is reciprocated to move the pressure plate 63' in opposition to the normal operation of the spring 62, causing the disengagement of the clutch plates 61.
When the clutch 61 is engaged as described, and the locking mechanism is released, the pod 41 may be instantaneously accelerated to the full speed of the frame 10. The effective rotation of the pod 41 at this time is a function of the gear ratio between gear 60 of the carrier 31 and the stationary gear 57. FIG. 7 is illustrative of the articulated rotation pattern of the pod 41 when, for example, a four-to-one gear ratio is employed. Thus, the centrifuge is concurrently rotated about its multiple axes, viz., trunnions 15, 16 and trunnions 29, 30. By preselecting the gear ratio between the gears 57 and 60, any one of a variety of rotation patterns of the pods 41 may be effected to produce the desired loads on the subject or object under test and located within the pod 41.
In order to accomplish substantially instantaneous stops of the centrifuge when desired, an electromagnetic brake 64 is provided. Preferably, this brake 64 is located adjacent the primary pivot of the centrifuge and comprises a depending annulus 65 carried by and projecting from the trunnion 16. At its lower or free end, the
annulus terminates in a flange 66 disposed within a chamber 67 provided in the stanchion 19. The chamber 67 may be produced in any known manner, such as, for example, by manufacturing the stanchion 19 in multiple parts and subsequently assembling and bolting or otherwise connecting the parts to form a unitary structure.
A coil 68 defines one wall of the chamber 67 in the final assembly, being associated in spaced relation with the flange 66 to coact therewith and thereby constitute stator and rotor elements. Loose filings or comparable particles 69 are disposed within the chamber 67 which normally are ineffective but which upon energizing of the coil 68 become magnetized and act as a rigid connector between the annulus 65 and the stationary stanchion 19.
FIG. 8 is an electrical wiring diagram which illustrates the circuitry through which is effected the operation of the several control elements, viz., fuel control or regulator 28, clutch solenoid 63, pod driving gears 44 and 48, pod release mechanism 52, electromagnetic brake 64, and the actuator of the reverse thrust device 25'. Each such control element connected to and adapted to rotate with the secondary arm or carrier 31 is individually connected by a lead or conductor 70 to a common electrical connector, such as a gang of electrically interconnected slip rings 71 between the carrier 31 and frame 10. These slip rings 71 are, in turn, in constant electrical engagement with a similar gang of electrically interconnected slip rings 72 operative between the frame and stationary structure associated with the apparatus. The slip rings 72 are each connected through an individual conductor 73 to a suitable source of electricalenergy.
A switch is provided in each lead 73 between the power source and the associated slip ring 72 whereby each circuit may be selectively energized in a predetermined sequence. For example, when the switch 78 is closed, a circuit is established from the .power source through its lead 73, slip rings 72 and 71, and lead'70 whereby solenoid 63 is energized, disengaging the clutch 61. Closing .the switch 74 completes the circuit from the power source When the frame 10 and carrier 31 attain a rotating ve- 'rier 31. At substantially the same time the switch 78 is opened for engagement of the clutch 61, giving the pod 41 an instantaneous acceleration from zero velocity to a velocity corresponding to that of the frame 10 and producing corresponding onset loads on the person or equipment within the pod 41. At the same time, the whip action effected by the articulated centrifuge imposes corresponding g loads. If desired, the operation of the switches 77 and 78 may be coordinated by appropriate interconnecting means well known to the art. I
The clutch 61 may be disengaged at this time by closing switch 78. The continued movement of the pinion gear 60 around the stationary gear 57 now transmits no rotation to the trunnion extension 58 and the carrier 31. With the locking mechanism 52 disengaged, the pod 41 is free to rotate about'the secondary pivot 29, 30 under, and corresponding to, the centrifugal force generated by the rotating frame 10.
The switches 79 and 80 are interconnected as at 81 for operation in unison to alternately connect when closed the vertical or horizontal rotating motor or drive gear 48 or 44, respectively, of the pod 41. A potentiometer is included in this circuit to permit the adjustment, if desired, of the speed of rotation of the respective gears 48 or 44 and the corresponding movement of the pod 41 in either plane of rotation. Through this circuitry it is designed and intended to permit the initial adjustment of the attitude of the pod 41 prior to ignition of the engine 25 or to effect rotation of the pod 41 at a selected speed about either axis during operation of the apparatus as already described.
Where it is desired to stop the rotation of the carrier 31 substantially instantaneously with the pod 41 located at any point in the selected pattern, switch 83 may be closed to complete the circuit between the power source and brake 64. A current is thereby induced in the coil 68 to effect a rigid connection between the rotating trunnion 16 and the stationary stanchion 19 as described.
In addition, a double-acting switch 84 is operatively connected in the circuit between the fuel control 28 and the power source that is operable from within the pod 41, for example, in an emergency when a human occupies the pod. Normally, this switch 84 is closed so that closing the switch 74 completes the circuit as described. In its alternate position, the switch 84 breaks this circuit and thereby terminates the flow of fuel to the engine 25. Concurrently, an additional circuit is completed through a conductor 85, slip rings 71 and 72, to the brake 64 for operation thereof in the same manner as described in connection with closing of switch 83. This alternate position of the switch 84 also establishes a circuit through a conductor 86, slip rings 71 and 72, to signal means such as a light 87 associated with and located externally of the apparatus. The operator or crew outside of the apparatus is thereby informed that the emergency switch has been actuated. Y
Upon completion of the selected operation of the centrifuge, it may be brought to a complete stop by operation of the reverse thrust device 25. To this end, switch 88 is closed, completing the circuit between the power source and the actuator of the device 25. The actuator is thereby extended, rotating the coacting doors to their transverse position, closing the exhaust duct, and sirnultaneously opening the side outlets of the engine and projecting the associated extension nozzles.
What is claimed is: I
1. An articulated centrifuge comprising a primary arm having a pivot rotatably mounted to stationary structure,
a secondary arm rotatably mounted on said primary arm adjacent an outer end thereof, said secondary arm terminating atone of its ends in'an independently rotatable pod normally disposed in axial alignment with said pivot, a connection betweensaid pod in its normal position and said stationary structure securing said pod against movement relative thereto, a drive operatively connected to said primary arm for the rotation thereof, and a control to break the connection aforesaid.
2. An articulated centrifuge comprising a primary arm having a pivot rotatably mounted to stationary structure, a secondary arm rotatably mounted on said primary arm adjacent an outer end thereof, said secondary arm terminating at one of its ends in an independently rotatable pod normally disposed in axial alignment with said pivot, a locking mechanism secured to said stationary structure and releasably engaging said pod, and a drive operatively connected to said primary arm for the rotation thereof.
3. An articulated centrifuge comprising a pair of arms rotatably interconnected one to the other, a pivot connecting one of said arms to stationary structure, a releasable engagement between the other said arm and said stationary structure establishing a selected rate of rotation thereof relative to said one arm, a pod carried by said other arm adjacent its free end and having an axis disposed in a plane intersecting the plane of said pivot upon relative rotation of the arms, a releasable connection between said stationary structure and said pod when disposed with its axis in the plane of the pivot as aforesaid, and a drive operatively connected to said one arm for the rotation thereof.
4. The centrifuge of claim 3 including brake means between said one arm and said stationary structure.
5. An articulated centrifuge comprising a pair of rotatably interconnected arms mounted for rotation on an axle connecting one of said arms to stationary structure, a pod rotatably mounted at a free end of the other of said arms and disposed in axial alignment with said axle, and a releasable connector securing said pod to the stationary structure when disposed as aforesaid.
6. The centrifuge of claim 5 including drive means for the rotation of said pod relative to and independently of said other arm upon the release of said connector.
7. The centrifuge of claim 5 including a drive operative on said one arm for the rotation thereof on its axle, and an electromagnetic brake between said axle and said stationary structure.
8. An articulated centrifuge comprising a primary arm rotatably mounted on stationary structure, a counterbalanced secondary arm rotatably mounted medially of its length on said primary arm adjacent the outer end thereof, said secondary arm terminating at each of its ends in a rotatably mounted pod extending outwardly therefrom, a closable access opening in each of said pods, a releasable connection securing one of said pods to said stationary structure, and a drive operatively connected to said primary arm for the rotation thereof.
9. An articulated centrifuge comprising a primary arm having trunnions rotatably mounted in stationary structure, a power drive carried by said primary arm and operative to rotate it relative to said structure, a counterbalanced secondary arm rotatably mounted on said primary arm adjacent an outer end thereof, a releasable differential engagement between said primary and said secondary arms, a pod rotatably mounted on a free end of said secondary arm and having an axis that intersects the axis of said trunnions upon each rotation of said secondary arm relative to the primary arm, releasable engagement means connecting said pod with said stationary structure when disposed in axial alignment with the trunnions as aforesaid, and a control for the operation of said power drive, said engagement and said connection in a selected sequence.
10. An articulated centrifuge comprising a primary arm rotatably mounted on a fixed stanchion, a power drive carried by said primary arm and operative to rotate it on said stanchion, a counterbalanced secondary arm rotatably mounted on said primary arm adjacent an outer end thereof,'a fixed gear carried by and projecting from said stanchion, an independently rotatable gear carried by and projecting from said secondary arm in constant direct mesh with said fixed gear, a releasable clutch between said rotatable gear and said secondary arm whereby rotation of the primary arm is imparted to the secondary arm, a pod rotatably mounted on a free end of said secondary arm and having an axis that aligns with the center of rotation of said primary arm upon each revolution of said secondary arm, releasable engagement means connecting said pod with said stanchion when disposed with its axis in alignment with the center of rotation of the primary arm as aforesaid, and control means for the operation of said power drive, said clutch and said engagement means in a selected sequence.
11. An articulated centrifuge comprising a powerdriven primary arm rotatably mounted on a fixed stanchion, a brake operative on said arm, a counterbalanced secondary arm rotatably mounted on said primary arm, a pair of coacting gears carried by and projecting from said stanchion and said secondary arm, respectively, said gears having a selected ratio for the rotation of the secondary arm at a predetermined speed, clutch means to operatively engage and disengage said gears, a pod rotatably mounted on a free end of said secondary arm and having an axis that aligns with the center of rotation of said primary arm upon each revolution of said secondary arm, releasable engagement means connecting said pod with said stanchion when disposed with its axis in alignment with the center of rotation of the primary arm as aforesaid, a plurality of individual electrical circuits between said power drive, said brake, said clutch means and said engagement means, a source of electrical power, and switch means to make and break said circuits, said source and said switch means being external to the centrifuge and said circuits being uninterrupted across the primary arm, the secondary arm and the stanchion through individual, constantly engaged slip rings.
12. The centrifuge of claim 11 including an additional normally open circuit between said power source and said brake through the pod, and a switch within said pod to close said circuit.
13. An articulated centrifuge comprising a primary arm rotatably mounted medially of its length on stationary structure, a drive connected to said arm for the rotation thereof, a secondary arm rotatably mounted medially of its length adjacent an outer end of said primary arm, a pod mounted on each end of said secondary arm, one of said pods being rotatably mounted on said secondary arm and having an axis in alignment with the center of rotation of said primary arm upon each revolution thereof, releasable means securing said one pod to said stationary structure with its axis aligned as aforesaid against relative movement therewith, an immovable gear concentrically disposed relative to said primary arm, a rotary gear projecting from and concentrically disposed relative to said secondary arm, said gears being in direct constant mesh one with the other, and releasable clutch means operative between said rotary gear and said secondary arm for the unitary rotation thereof.
14. An articulated centrifuge comprising a primary arm rotatably mounted medially of its length on stationary structure, a drive connected to said arm for the rotation thereof, a secondary arm rotatably mounted medially of its length adjacent an outer end of said primary arm, a pod mounted on each end of said secondary arm, an immovable gear concentrically disposed relative to said primary arm, a rotary gear projecting from and concentrically disposed relative to said secondary arm, said gears being of selected different sizes and in direct constant mesh one with the other, and releasable clutch means operative between said rotary gear and said secondary arm for the unitary rotation thereof.
15. An articulated centrifuge comprising a primary arm rotatably mounted medially of its length on stationary structure, a drive connected to said arm for the rotation thereof, a rigid secondary arm rotatably mounted centrally of its length on said primary arm adjacent an outer end thereof and disposed at all times in a plane 9 substantially parallel to said primary arm, a pod mounted on each end of said secondary arm in suspended, spaced relation to said primary arm, an immovable gear concentrieally disposed relative to said primary arm, a rotary gear projecting from and concentrically disposed relative to said secondary arm, said gears having peripheral, coacting teeth in direct constant mesh one with the other, and releasable clutch means operative between said rotary gear and said secondary arm for the unitary rotation thereof.
References Cited in the file of this patent UNITED STATES PATENTS Van Sant et a1. May 14, 1912 Pewitt Dec. 26, 1950 Castille Dec. 16, 1958