US2596130A - Manually operated telemetric gun control system - Google Patents

Description

y 13, 1952 E. c. CUNNINGHAM 6,130

MANUALLY OPERATED TELEMETRIC GUN CONTROL SYSTEM Filed June 28, 1945 3 Sheet sSheet l I E arl E Cunnivgham e: fimrjfmw Wag y 1952 E. c. CUNNINGHAM 2,596,130

MANUALLY OPERATED TELEMETRIC GUN CONTROL SYSTEM Filed June 28, 1945 3 Sheets-Sheet 2 T0 DIFFERENTIAL '"REPEATER E. C. CUNNINGHAM May 13, 1952 MANUALLY OPERATED TELEMETRIC GUN CONTROL SYSTEM 3 Sheets-Sheet 3 Filed June 28, 1945 pressure fluid is flowing to the motor.

Patented May 13, 1952 UNITED STATES rant ore ICE 7 r MANUALLY OPERATED TELEMETRIC GUN CONTROL SYSTEIVI 7 Claims.

amended April 30, 1928; 371) O. G. 757) The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to manual control mechanisms to control the rate of angular movement a source of high pressure oil through reversing When the valve is in connections to the motor. central position, no oil flows to the motor from the high pressure source and no movement of the gun takes place. As the piston of the valve is moved in one direction or the other, flow of high pressure oil is permitted from a correspond-"' ing end of the main valve, to thereby rotate the motor, exhaust taking place to the sump, by way of the other end of the main valve. Thus the direction of rotation of the motor depends upon the direction of displacement of the pilotvalve; and the rate of rotation is proportional to valve displacement. It will be understood that two motors are used, one to train the gun and one to elevate it, and that each is controlled by The descrip-"= a corresponding hydraulic valve.

tion will be confined to the train control since both operate upon the same principles.

Confining the description, then, to the mechanism for controlling movement of the gun in train, control of the hydraulic gun train motor is effected by a gun train differential repeater having a stator delta-connected to the stator of a gun position train transmitter, and a rotor deltaconnected to the stator of remote control train Movement of the hydraulic motor transmitter. control valve is effected by a mechanical connection with the rotor of the aforesaid gun train differential repeater. The rotor of the remote control transmitter, and the rotor of the gun position transmitter, are connected in parallel" witha single phase source. The rotor of the gun position train transmitter is connected to be driven from the corresponding hydraulic gun train motor and at a reduced rate such as 18.

to 1, so that said rotor is turned 18 complete revolutions for each 360 angular movement of the resultant gun in train.

When the aforesaid parts are at rest, the fields induced by the rotor and stator of the differential repeater, are in alignment and no torque is applied to the rotor. Hence the hydraulic motor control valve is in cut-off position so that no Upon rotation of the remote-control train transmitter 2 rotor, the direction of the induced field in the stator rotates proportionately and this rotation causes a corresponding rotation of the field induced by the rotor coils of the gun train differential repeater. Inasmuch as the gun is not moving, the field induced in the stator of the gun position train transmitter is at rest as well as the field controlled thereby in the stator of the gun train difierential repeater. Therefore, because of the interaction between the two difzferential repeater fields, the rotor thereof turns to eiiect a corresponding movement of the control valve. The connections are such that the resulting mcvementof the hydraulic gun train motor, acts to turn the rotor of the gun position train transmitter in the proper direction until the field induced in its stator and repeated in the stator of the differential repeater, is again in alignment with the field induced in the rotor of the gun train differential repeater, so that the rotor torque of the differential repeater drops to zero. Thereupon, the control valve returns to cut-off position under the urge of a centralizing spring and all movement ceases. Thus the gun angularly moves at all times in a direction determined by the direction of rotation of the transmitter rotor at the remote director, while the rate of angular movement is proportional to the rate of rotation of said rotor. In short, the rotor of the gun position transmitter follows the rotor of the remote control transmitter, so that the two actually rotate in synchronism.

From the foregoing description, it will be apparent that, if the rotor of the gun position train transmitter is disconnected and locked in position so that it is not moved in response to operation of the hydraulic gun train motor, the rotor of the gun train differential repeater will be responsive solely to displacement of the transmitter rotor at the remote control. As the hydraulic gun train motor will ordinarily be connected to the rotor of the gun position train transmitter in, say,'an 18 to 1 ratio, the transmitter at the remote control must rotate 18 times for each 360 rotation of the gun in train. By the disconnection and locking of the rotor of the gun position train transmitter, however, the rate of train of the gun is made proportional to the displacement of the remote control transmitter rotor, and a sensitive and rapid response of the gun is provided with relatively small displacements of the remote control rotor; i

At times it has been found desirable in combat either because the remote automatic director is out of action or for other reasons, to provide for manual control by a single observer located at a point somewhat remote from the gunwhereby the observer may direct the gun by observation of the tracers alone.

It is an object of my invention toimodify the .the shaft l2 vof a hydraulicfel'evating motor l3. "'Eachmotor 9'and l'3 may"incorp"ofate"control controlsjust described, whereby manual control may be substituted for the director quickly and without in any way impairing the re-conversion to automatic control when desired.

t is a further object of my invention to provide a manually operated control box that uses standard parts and that gives sensitive and rapid manual rate control of the gun in elevation and azimuth.

Another object is to provide an efficient and accurate manual control in case the automatic director is out of action.

A further object is to provide a mechanism enabling instantaneous ,lchange from director or automatic control of a power-operated gun, to manua control thereof. a

Anotherobject is to provide a single manual control lever for controlling movement of the gun about both axes of movement and so correlated with said axes that movement of said lever simulates movement of the gun itself A still further object is to provide a manual control as explained in the preceding paragraph that enables the observer to take the position; that is most favorable for each tactical situation '25 encountered.

Other objects and advantages will become apparent as the description proceeds.

In the drawings: a;

Fig. 1 is a diagrammatic view showing the general arrangement of a gun with my invention applied thereto;

Fig. 2 shows the transmitter and oil gear unit at the gun as used with automatic director control, it being understood that two units are used" 5 with each gun, one for control in train and the other in elevation;

Fig. 3 shows the construction of Fig. 2 after the necessary changes have been made to adaptthe same to manual control inaccordance withi the invention;

Fig. 4 is an enlarged detail showing a preferred manner of locking the'armature of the gun position transmitter, whereby direct manual control of the diiferentialrepeater is effected 5 Fig. 5 is a side elevation of Fig. 4;

Fig. 6 is an exterior View ofthe control box constructed in accordance with theinvention;

Fig. 7 is an elevation of the control box with one side removed to show the interior construe-" tion;

Fig. 8 is an exploded perspective view'of a modification whereby shifting of a lever acts instantaneously to disconnect the oil gear and lock the transmitter rotor;

Fig. 9 is a view showing a modification wherein a single joy stick control is employed for the elevation and train transmitters, and

Figure 10 is a schematic view of the electrical and hydraulic controls including remote control means.

At Fig. 1 I have shown, more or less schematically, a gun I having a cradle 2 with trunnions 3. These trunnions are mounted in bearings in. supports 4 fixed to a rotatable platform 5 that is journaled on a fixed base 6 for rotation about a vertical axis. A ring gear T is'fixed' to base 6 and is in mesh with a pinion 8'mounted upon the shaft of hydraulic train motor 9 which, in turn, is fixed to platform 5. A gear sector It is fixed to cradle 2 concentric of the axis of trunnions 3. A worm II is journaled upon platform 5 and meshes with said sector. Worm ,H is fixed to actuating means therefor for controlling the flow thereto of high pressure fiuid.

One such mechanism is shown in Fig. 10, where the cylinder it of a control valve has its ends connected by passageways i5 and it to motor ii, and its center connected by pipe I1 to a source of high pressure fiuid. A spool or piston [8 has its ends slidably fitting cylinder l4 so that, in the position shown, flow of fluid to the motor is prevented. The motor may be rotated in one direction or the other by a corresponding direction of movement of piston I8. The piston is actuated by means ofia rack 19 secured thereto and in mesh with a pinion 20 upon the rotor shaft of a 'difierential repeater motor 2|. This motor has 3-phase, deltaor Y-connected stator or field coils 83 and rotor or armature coils 84 so related that the rotor '84 'willbe urged. to place the resultant field induced in its coils, in alignment with the resultant field induced in the coils of stator 83. Thus, when any relative rotation between these fields occurs, valve l8 will be moved upwardly or downwardly, as the case may be, to effect a corresponding rotation of motor 9 and training movement of the gun.

As shown upon Figure 10,motor 9 has its shaft connected, as by a manually operable clutch 8", subsequently described, with the rotor shaft of gun position train transmitter 21, comprising a rotor 27a. and a stator 27b, and carried by platform 5. By this construction, as the gun is moved in train in response to displacement of valve is from central position, the rotor of transmitter 21 is turned in step therewith, for example, in an 18 to 1 ratio. Three-phase connections are indicated at 25!, between a transmitter 41 and repeater 2i, and at 30, between repeater 2i and transmitter 21. Thus, when the rotor of the train transmitter 41 at the remote control means or director is turned, a relative rotation of the rotor and stator fields in the differential repeater 2| is effected, resulting in a displacement of valve piston l8 and a rotation of motor 9 to train the gun in the proper direction. At the same time, the rotor of transmitter 21 is turned to correspondingly rotate the field induced in its stator coils. The reproduced field in the stator 83 of gun train differential repeater 2| is correspondingly turned and the connections are such that this field follows the field rotation induced in its rotor 84 by rotation of the remote transmitter 41. Thus, when the two fields in the repeater 2| are again matched, the torque exerted thereby reduces to zero and the valve resumes its centralized, or cut-01f position, under the influence of restoring springs, not shown. 7

Fig. 2 shows an actual construction employed in the oil gear of an antiaircraft gun, with cover plate 3l broken away. The numeral 32 identifies a framework carried by the gun carriage or platform mechanically coupled with one hydraulic motor such as 9, carries a worm 34, in mesh with gear 36 fixed to the rotor shaft 3? of gun train transmitter 21. Transmitter. 21 is electrically connected as shown upon Fig. 10. f I

At times, it is necessary or desirable to temporarily dispense with'the director and to provide for manual control of the gun whereby the same is trained and elevated in response to the observation of the tracers. 'In such cases, it is not sufficient merely to substitute a pair of handbperated transmitters corresponding to the '.ftransmitters .in' the director. the first place,

thesetransmitters," because of the geareddown operated manually, rough tracking would result.

In the second place, the transmitter shafts in the director not only control the rate of movement of the gun by their rate of displacement, but their actual displacement or rotation from a given position is proportional to a corresponding angular movement of the gun.

On the other hand, for manual control, it is extremely desirable to increase therate of response of the gun for a given relatively small angular displacement of the respective control transmitters, and to make said rate proportional to the displacement of the respective transmitters, instead of proportional to their rates of displacement. This is because the latter arrangement permits the operator to sense the deflections necessary to bring the tracer stream onto the target much more quickly and accurately in that, with practice, he can get the sense or feeling that he is directly moving the gun itself.

In the preferred form of the invention, means are provided to rapidly disconnect the gun position train transmitter 21 and gun position elevation transmitter 86 from the hydraulic motors 9 and [3, respectively, and, at the same time, lock the rotors of the aforesaid transmitters. Referring to Figs. 8 and 10, gun position train transmitter 21 has clutch teeth 58 fixed to its casing concentric of its splined shaft 59. The shaft has a reduced threaded end 60. A clutch element 6| has a splined bore 62 slidably fitting shaft 59 and is provided with clutch teeth 63 on one side to engage with teeth 58, and teeth 54 on its other side to engage the teeth 55 of a disc 66. This disc has a central bore 6'! to fit the reduced end 60 of shaft 59 so that when lock nuts 68 are in place, the disc may freely rotate upon the shaft when free of clutch element Bl. As shown upon Fig. 10, the shaft of hydraulic motor 9 is mechanically coupled in any suitable manner, with disc 66.

Clutch element 6| is formed with a peripheral gun and the gun posi-' channel 10 whose side walls are engaged by rollers, not shown, mounted on stub shafts ll of a forked lever 12. This lever is fulcrumed by a pin 13. When the lever is shifted in the direction of arrow D, Fig. 8, teeth 64 and B5 are brought into engagement and disc 66 and the shaft of motor 9 are locked to shaft 59 whereby the gun is adapted for control by a remote director or computer. When lever 12 is thrown in instantaneously merely by shifting lever 12. The

parts are so dimensioned that one pair of clutch teeth are fully separated before the other pair can begin to engage.

The hydraulic gun elevation motor [3 is similarly connected with its transmitter 85 by a clutch whose parts are identified upon Fig. 10 by the same numeral, primed, as are used to identify corresponding parts for the motor 9. Hence it is unnecessary to describe these parts in detail.

A control box 38 is provided that may conveniently be substantially cubical and about ten inches on a side. The box has astrap 43 and hangers 44', by which it may be suspended from the neck of the operator. As shown at Fig. 7, a standard receptacle 44 is mounted with the box and is adapted to receive a plug 45 on the end of cable 45, whereby all connections may be simultaneously made by the simple operation of securing the plug in its receptacle. This receptacle 44 may be identical with the one used in the director and may be similarly wired to the transmitters so that the change from director to manual control may be made simply by removing plug 45 from the director and inserting it in the receptacle in box 33. This is, of course, merely a matter of convenience, as the connections from gun to box 38 may be made in any way desired.

A train transmitter 41 comprising stator 41a and rotor 41b has a base 48 secured to the righthand wall of the box 38, as viewed in Fig. 7. The shaft 49 of the rotor of transmitter 41, extends upwardly through the top of the box and terminates in a knob or handle 50. Electrical connections 5! are provided between the transmitter and receptacle 44. An elevation transmitter 52 has its base 53 affixed to the bottom of box 38 and its rotor shaft 54 projects through the left hand wall of the box, as viewed in Fig. 7, and there carries a knob or handle 55. Electrical connections 29 are provided between the transmitter and receptacle 44 to junction box 51 on platform 5. The rotors of transmitters 21, 86, 4! and 52, are all energized in synchronism by a source of single phase A. C. 9|, and connections 90, Figure 10.

The operation will now be clear from the foregoing description. When the rotor of the gun position transmitters are locked, rotation of train transmitter knob 50, for example, causes a corresponding rotation of the induced field in its stator and effects a corresponding rotation of the field induced in the armature of gun train differential repeater 2|. Since the gun position transmitter rotors are locked, the field induced in the stator of each differential repeater motor is fixed. As a result, when knob is turned, armature 84 is displaced in a corresponding amount and direction. Since the displacement of the valve l8 of the hydraulic train motor 9 is proportional to the armature displacement, the gun is trained in a direction and at a rate .corresponding to the direction and amount of displacement of said knob. It will be understood that movements of knobs 50 and 55 is so related to the resulting gun movements that, when knob 55 is turned to the right, the gun moves to the right, and when knob 55 is elevated, the gun moves to increase its elevation. Thus, the two movements are effectively correlated and, with practice the operator comes to intuitively turn the controls in the proper direction and amount to quickly cause the trajectory of the tracers to intersect the target.

While I have shown the form of my invention now preferred by me, because it unitizes the remote control system to place responsibility in a single person, this is not absolutely necessary. If desired, the controls may be separated, one man being assigned to operate the azimuth knob, and another to operate the elevation knob. It has been found that a man with as much training as he normally receives on the director, is able to manipulate the controls instinctively to high precision control of the gun and eta rate faster than is possible either with the director --or previous systems of manual control.

would be insignificant, in comparison to the rector.

Furthermore, within the limits of the length of cable 46 connecting box 38 and the gun-platform, the operator may take the most advani tageous position for viewing the tracers-and the target at a point remote from the smoke and jar. There is no dead area as in the-case of director control, so that the field oi fire is literally, 360 of azimuth with my inventions many thousands of dollars cost of a single di- By'having the power plant and-junction box upon the gun truck (not shown) the gun may be fired in traveling position without dismounting from the truck so that only a negligible time need elapse between stopping the truck and the order toopen fire.

Where a simplified construction desired, it is possible-to realize the benefits of the invention without the two clutches 85 and 35'. Thus, referring to Figs. 2 through 5, the numeral 27 identifies a gun position train transmitter which is essentially similar to instrument 2? except that it has a plain shaft 31 to which a disc 39 is attached. A gear 35 is attached to disc 39 and is driven by a pinion 34 fixed to shaft 33 which, in turn, is mechanically coupled with motor 9. When the parts are as shown at Fig. 2, the gun is adapted for automatic or computer control. When direct manual control is desired, gear 36 is removed and disc 39 and shaft 31 are locked by a screw ll, Figs. 4- and'5, inserted through a hole in disc 39 and threaded into a tapped hole a lug 30 of the transmitter casing. The hydraulic gun train motor is thus disconnected from its transmitter and the rotor of the latter is looked, as in the preferred form. In this way the two clutches may be omitted although, of course, a longer time is required to effect change from one type of control to the other.

In Fig. 9, I have shown a joy stick control that may be substituted for the control shown at Figs. 6 and '7. This consists of a first slotted bail or yoke i3 journaled upon trunnions is and forming a diameter of said bail. One trunnion 14 is connected to the rotor of a transmitter 18 that may control movement of gun in train. A second slotted bail T! has trunnions l8 and 19 extending on a diameter of said bail. The axes of the two pairs of trunnions are mutually perpendicular and the rotor of an elevation transmitter 853, is secured to trunnion 18. Bail 11 is slightly less in diameter than ball 13, so that the two may rotate without any interference. A universally pivotable lever SI is universallymounted at 82 and extends through the opening defined by the overlapping slots in bails l3 and ll. The parts may be so mounted on a base, that, when in position on the person controlling the gun, the axis of trunnions 74-15 will be vertical while that of trunnions l8 and 19 will be horizontal. Thus, lever 8| has axes of movement similar to those of the gun and, by grasping the lever and moving it in the direction in which it is desired to move the tain's-the feel that he is actually moving the gun itself.

' Thus I have provi'd'edamechanism that: may

either replace or be instantaneously substituted for director control 0f a-gun, to manually control therate and-direction of movement of the gun in a smooth precise: and rapid manner. -By my invention; the flexibility and effectiveness' of a "weapon equippedtherewithare greatly'increased and the gun may be used under conditions of fire where director control is impractical orimpossible.

While I have shown myinvention in connection witlra 40-mmcfire unit, it willtbe understood that it is merely to comply with the requirements ofthe patent statutes and is not to'be construed-in a limiting sense. The control is'readily adapted touse with any powercontrolled weapon capable of being independently aimed. Therefore; I denot -wish to be limited to the-precise-details of construction shown; but" reserve all" such'modifications, alterations, andsubstitutions of equivalents as fall within the scope of "the sub-joined claims.

Having fully disclosed'the'invention, what I claim as new, and desire'to secureby Letters Patent is:

1. In a gun control system, a gun position transmitter having a fixed frame and a splined shaft, a first series of clutchteeth on said frame, a disc having a second series of clutch teeth and journaled on said shaft, means rotating said disc by and in proportion to angular movement of the gun about a predetermined axis, a clutch element splined to said shaft and having oppositely facing series of clutch teeth to engage said first and second clutchteeth,respectively, and means manuallyoperable-toshift said elementaxially of said shaft to ..thereby selectively clutch said disc to said'shaft'or alternatively to lock said shaft to said frame.

2. In a control system for a gun having a reversible hydraulic motor. connected to rotate the gun about a predetermined axis, control means for said motor comprising a.valve a repeater having stationary field coils and.v an armature, a driving connection betweensaid repeater armature and said valve, afirsttransmitter having its field coils connected to the field coils of said repeater so that the fields induced thereby rotate in synchronism, a second. transmitter having its field coils connected with the armature of said repeater so that the fields induced thereby rotate in synchronism, means connecting the armatures of said transmitters for synchronous energization by a source of alternating current, manually operable means connected to rotate the armature of said second transmitter, and means operable to selectively connect the armature of said first transmitter to be'operated by and in accordance with the operation of said motor, or to lock said armature against movement relatively to its field coils while simultaneously disconnecting thesame from said motor.

3. In a control system for agun angularly movable about first and'second mutually normal axes, first and second hydraulic motors each connected to move said gun'about a corresponding axis, a control valve for starting and reversing each motor, first andsecondtelemetric repeaters each having its armature connected to operate a-respectivecontrol valve, a support, firstand second manual transmitters on said support, manually operable means connected to turn the rotors of saidtransmitters, first. and

- second gun transmitterseachhavingits rotor 76' a'dapted to be turned in response tamovement of 9 said gun about a corresponding axis, means electrically connecting the stators of said gun transmitters with the stators of said first and second repeaters, respectively, whereby the fields induced thereby rotate synchronously, means electrically connecting the stators of said first and second manual transmitters with the armatures of said first and second repeaters, respectively, whereby their fields rotate synchronously, means energizing the rotors of said transmitters in phase, and means selectively operable to connect the rotor of each said gun transmitter to be turned by and in proportion to the angular movement of said gun about a corresponding axis, or to disconnect said rotors from said gun and lock the same in fixed relation with its respective stator.

4. In a manual control for a power-operated gun, a hydraulic elevation motor, a gun elevation transmitter. having rotor and stator coils, a differential repeater having relatively rotatable field and armature coils, one of said coils being electrically connected with the stator coils of said elevation transmitter, a remote transmitter having a manually-rotatable rotor coil, electrical connections between the stator coils of said remote transmitter and the other of the said coils of said repeater, means electrically connecting the rotors of said transmitters for energization in phase, a control valve for said motor connected to be actuated by rotation of said repeater armature and means operable at will to selectively connect the rotor of said gun elevation transmitter to be rotated by and in accordance with rotation of said elevation motor, or to disconnect said rotor from said motor and lock said rotor.

5. In a selective manual or remote director control for a power-operated gun, a reversible motor connected with the gun to angularly move the same, a gun transmitter having arotor and a stator, a differential repeater having relatively rotatable field and armature coils, one of said coils being electrically connected with the stator coils of said gun transmitter, a remote transmitter having stator coils and a rotor coil, manually operable means connected with the rotor coil of said remote transmitter to rotate the same, electrical connections between the stator coils of said remote transmitter and the other of the coils of said difierential repeater, means electrically connecting the rotors of said transmitters for synchronous energization from a common source of A. C., .a control including a part movable to control the direction and rate of movement 01' said reversible motor, a driving connection between said other coil of said differential repeater and said part, and means selectively operable to connect the rotor of said gun transmitter to be driven by said reversible motor synchronously therewith, or to lock said with corresponding coils of the stator of said second transmitter, the field coils of said differential repeater being electrically connected with corresponding field coils of said first transmitter, control means operable to control the direction and speed of operation of said motor, a driving connection between said control means and the armature of said differential repeater, and clutch means manually operable from a first position coupling the rotor of said first transmitter with said motor'for synchronous rotation therewith, to a second position disconnecting said motor and rotor while positively locking the rotor in fixed relation with its stator.

7. In a system for training a gun about a normally vertical axis, a hydraulic motor adapted to be connected to train the gun, a valve for controlling the direction and rate of movement of said motor, a differential repeater having polyphase field and armature windings, a driving connection between the armature of said 'rerotor in fixed relation with its stator and independent of said reversible motor.

6. In a control system for a gun having a motor connected to angularly move said gun about a predetermined axis, a first transmitter having stator and rotor coils, a second transmitter having stator and rotor coils, manually operable means connected with the rotor coil of said second transmitter to rotate the same, a difierential repeater having relatively rotatable field and armature coils, the armature coils of said differential repeater being electrically connected peater and said valve, first and second transmitters each having polyphase distributed stator windings and a single phase rotor winding, means manually operable to rotate the rotor of said second transmitter, electrical connections between the windings of the armature of said differential repeater and the stator windings of said second transmitter, electrical connections between the field windings of said'difierential repeater and the stator windings of said first transmitter, circuit means for synchronously energizing the rotor windings of said first and second transmitters from a source of A. C., and clutch means operable selectively from a first position positively connecting the rotor. of said first transmitter for operation by said hydraulic motor to a second position disconnecting said motor and rotor and locking said rotor in fixed relation with its stator windings.

EARL C. CUNNINGHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,122,942 Kaminski Dec. 29, 1914 1,360,664 Miller Nov. 30, 1920 1,393,837 Schneider Oct. 18, 1921 1,470,369 Kaminski Oct. 9, 1923 1,612,117 Hewlett et al Dec. 28, 1926 1,612,118 Hewlett et al. Dec. 28, 1926 1,612,119 Hewlett et a1 Dec. 28, 1926 1,612,434 Henderson Dec. 28, 1926 1,865,356 Daum June 28, 1932 1,894,822 Hewlett et al Jan. 17, 1933 1,942,079 Willard Jan. 2, 1934 2,040,014 Mosely May 5, 1936 2,107,803 Rolcik Feb. 8, 1938 2,203,097 Lamond June 4, 1940 2,373,990 Barnhart Apr. 17, 1945 2,379,778 Allen July 3, 1945 2,381,840, Schaefer et al Aug. 7, 1945 2,393,189 Richmond Jan. 15, 1946 2,408,068 Hull et al. Sept. 24, 1946 2,409,190 Brown et al. Oct. 15, 1946 FOREIGN PATENTS Number Country Date 11,570 Netherlands Aus. 15, 1924

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