US2454071A - Gun control mechanism - Google Patents

Description

Nov. 16, 1943. J, P, m, HAL 2,454,071-

GUN CQNTROL 'uncnmxsm I Filed May 20, 1944 a Sheets-Sheet 1 INVENTOR MITCHELL M. BERRY BY 7 JOHN P. LIDRAL ATTORNS Nov. 16, J. P. LIDRAL EI'AL GUN CONTROL MECHANISM 3 Sheets-Sheet 2 Filed May 20 1944 lnventor METCHELL M. BERRY JOHN P. LIDRAL.

attorney Nov. m, 1948.

Filed may 20. 1944 J. P. LIDRAL E-rm. 9

am; con-moi. uncmrsm s Sheets-Shem; 3

\ INVENTOR M lTCHELL M. BERRY JOHN P. LIDRAL I ATTQRNEYS- Patented Nov. 16, 1948 1 UITE STATES OFFlC GUN CONTROL Application May 20, 1944, Serial No. 536,554

5 Claims. 1 Our invention relates to mechanism capable of controlling a hydraulic motor system particularly useful for aiming a gun, such as a machine gun mounted in an aircraft for remote control.

In certain aircraft installations it has been found that a machine gun mounted in a location remote from the gunner can cover a larger or more advantageous field of fire than one operated directly by him. In such instances a sight movable with the gun is mounted at the gunners station. The fire of such a remotely positioned gun may be controlled more accurately, however, if

its control handles simulate the normal gun handles.

i A machine gun customarily has twin handles mounted on the rear portion of its casing. The gun is swiveled so that if the gunners wrists are tilted upward and his hands moved downward to depress the rear portion of the gun its barrel will be elevated, and vice versa. Similarly if the gunner's hands are shifted to the right the gun bar rel will be deflected toward the left, and vice versa. Any combination of right or left movement and up or down movement may be effected simultaneously to move the gun partially in traverse and partially in elevation.

It is therefore a principal object of our invention to provide control mechanism for a remotely operating gun which incorporates twin control handles corresponding to the machine gun handles usually mounted on'the rear of a gun.

Itis a further object to provide such mechanism for controlling a hydraulic motor system operatively connected to a gun or guns in a manner to effect elevation and/or traversing thereof in response to corresponding movement of the control mechanism.

More particularly it is an object of our invention to incorporate gun control handles and liy-' draulic, control mechanism for a remote gun installation in a compact and eillcient unit, which will enable a un to be trained by movement of the control handles in a manner very similar to that which would be required if the handles were mounted on the gun itself. Such modification in operating the handles of my control over the movement executed by the usual handles in aiming a gun actually renders control of the gun more convenient, without greatly altering the feel of the gun operation from that experienced in maneuvering the gun directly.

In such mechanism it is an object to achieve simplicity of structure and lightness without sacrificing effectiveness or efliciency, while at the same time promoting economy of manufacture. Additional advantages will be recognized in the particular construction of the control unit shown in the accompanying drawings and described below. While such mechanism is entirely practical, it may be considered as representative. In some instances it may be desirable to modify various features of it while 'still employing the principles of our invention.

Figure 1 is a perspective view of our control unit, and Figure 2 is a similar perspective view with the near quadrant of the control unit broken away to reveal interior construction. Figure 3 is a fragmentary vertical sectional view through the unit taken perpendicular to the control handle shaft.

Figure 4 is a perspective view of our control unit, parts of which have been broken away, showing the body of the unit in phantom and illustrating diagrammatically other elements of the system and the hydraulic liquid circuit through the control unit and other elements.

A machine gun installation, in order to be capable of sweeping universally-throughout its entire field of fire, must be capable of simultaneous elevational and traversing movement. Such universal training can be effected, however, by the provision of merely a traversing drive'and an elevational drive, provided that they can be operated simultaneously and at different rates. Since such drives are conventional they are mentioned here only to indicate the general type of mechanism with which my control unit may be assoelated. Because such arrangements are well known to those skilled in the art, neither a gun,

nor its mounting structure nor its drive arrangement is shown in detail, but in Figure 4 various conventional elements of such a system are included diagrammatically. I

In Figure 4, therefore, pump i may withdraw hydraulic liquid, usually oil of some suitable type, from a reservoir or tank H), for discharge under constant pressure into the delivery conduit I I connected to the control unit body 2. An accumulater [2 may be connected to this conduit to assist the pump 1 in maintainin stead pressure in the conduit. From the control unit body the hydraulic liquid will pass through the motor system piping shown in broken lines either to a motor [3, operative to traverse the gun, or to a motor 14, operative to move the gun in elevation, or to both. From these motors the hydraulic liquid returnsthrough the control unit body 2 back to the reservoir by way of return conduit I5.

While hydraulic liquid always flows through delivery plpe l l and return pipe IS in the directions indicated by the arrows,'it will be understood that to swing the gun to the right the liquid must flow to traversing motor l3 through one duct connected to it and return from it through the other, whereas in swinging the gun to the left the direction of flow through both of these conduits will be reversed; Similarly liquid will flow through one conduit to elevating motor l8 and return through-the other conduit to the control unit 2 for elevating the gun, but the direction of flow in both of these conduits will be reversed to depress the gun.

The function of the control unit, therefore, is to-distribute oil delivered to it from supply conduit il in the desired direction to one or-both oi the hydraulic motors i8 and I4, and simultaneously to enable liquid to return from one or both of these motors to tank l8 through conduit I8. The control also must operate to regulate the velocity of flow to each of motors l3 and I 4 independently of the rate of flow to the other, so that the speed of movement of the gun may be controlled accurately to coincide with the travel of the target.

As will be seen in Figure 1, the control unit 2 is exceedingly compact, consisting of three principal components. A central section 20 contains the ducts communicating with the elevating motor l4 and those for the supply and return conduits II and I5 connected to the pump l and to reservoir Ill, respectively. Below this central portion and integral with it is a valve assembly casing 2|, which houses the valves controlling traversing oi the gun, and which contains ducts connected to the conduits communicating with traversing motor l3. Surmounting the central section 20 and rotatable upon it about a vertical axis is a second valve assembly casing 22 housing the valve mechanism which controls the flow of liquid to elevating motor l4 for elevating or depressing the gun.

The valves in the two assemblies within the casings 2| and 22 are shifted-mechanically between open and closed positions by movement of control handles 28, which are mounted upon a horizontal shaft 24 extending centrally through casing 22. These handles may be moved universally to effect, in varying degree, movement of the valves in only one assembly or conjoint movement of the valves in both assemblies to accomplish the desired movement of the gun. In addition to controlling training of the gun these control handles preferably incorporate trigger levers 28 which may be squeezed to flre the gun. Such trigger levers are conventional.

Operation of motor M to eflect elevational movement of the gun is accomplished by the gunner tilting his wrists up or down to swing handles 23 for rotating shaft 24 without movement of casing 22 relative to the central section 20 of the unit. .On the other hand, operation of motor I 3 to traverse the gun is eflected by the gunner swinging his hands transversely to revolve handles 23 and shaft 24, and consequently also casing 22, about a vertical axis relative to the central section 28, and, more important, relative to casing 2|. It is evident that the gunner may simultaneously tilt his wrists up or down and swing his hands to the right or left, to effect combined rotation of shaft 24 within casing 22 and revolution of such shaft and easing about a vertical axis. Such movement will have the effect of operating coniointly, though perhaps at different rates, both motors l3 and M to accomplish a combined elevational and traversing movement of the gun, corresponding to the operation of the handles.

The only difl'erence between the movement of handles 28 effected to train a gun and that of corresponding conventional handles mounted directly on a gun is that in the latter case it is necessary to move the handles bodily throughout a range corresponding to the gun movement.

Consequently the handles are only in neutral position when the gun is directed centrally of its field of flre. In an'installation of the type for which our control is adapted, however, the gunner must rely on the position of his sight to indicate the attitude of the gun, since the handles 28 will be deflected from neutral position only to effect actual movement of the gun. At all other times the handles will be in neutral position about both a vertical and a horizontal axis, even though the gun may be deflected from neutral position, and perhaps even into an extreme position.

Instead of the handles 23 of our control unit being moved throughout a range corresponding to the sweep of the gun they are merely deflected relatively slightly from neutral position and held deflected in the proper sense for a length of time required for the gun to be aimed in the desired direction. Thereupon the handles are returned to neutral, which merely brings the gun to rest rather than returning it to its central position.

If it is desired to swing the gun back to center the handles must be deflected in the opposite sense and held thus until the gun returns.

The degree of deflection of handles 23 from their neutral position determines the speed at which the gun will be shifted, because the valves in the control unit controlling flow of liquid through the hydraulic system are moved to a corresponding extent. .If the handles are released the trigger levers 28 will return automatically into the inoperative position shown, and the handles will be shifted automatically back to neutral position by centering springs to terminate movement of the gun. A spider 28 carried by shaft 24 has bent fingers which engage over a spring wire ring 21 to hold it contracted radially, and consequently circumferentially, under stress. this ring overlap somewhat and are hooked to engage opposite sides of a lug 28 carried by casing 22. A finger 28 of spider 28 maybe disposed alongside and in registry with lug 28, so that it also is engaged between the hooked ends of spring 21.

It will be seen that rotation of spider 28 by shaft 24 will shift its finger 29 to pull the hook of spring ring 21 toward which the finger rotates away from its other hook held stationary by engagement with the opposite side of lug 28. Such movement will, of course, contract the spring circumferentially to increase the stress in it, so that when the, handles are released the resilience of the spring will expand it circumferentially to return spider finger 29 into coincidence with lug 28, consequently rotating shaft 24 and handles 28 back into neutral position. The spider 28 and spring 21 may be duplicated at the opposite side neutral position relative to block .20 when rotational pressure on casing 22 is terminated by releasing handles 23.

The ends of The valve mechanisms employed for controlling the supply of liquid to traversing motor l3 and elevating motor l4 housed in casings 2| and 22, respectively, are identical. Since the valve mechanism in casing 22 is shown in Figures 2 and 3 more clearly than that in casing 2| the former will be described in detail. Shaft 24, which extends through the casing, has a central portion of elliptical cross section rather than of circular shape, as shown in Figure 3, which functions as a valve operating cam. Extending radially from this ellipitical shaft portion, all in the same plane, are four apertures spaced ninety degrees apart. Each aperture receives a valve unit 3, which includes a body 3|] fitting snuglyin one of such apertures in casing 22.

In the bore of each valve body 30 a valve 3| is guided for reciprocation between a closed position engaging its seat .32 and an open position displaced radially outward from such seat. The valve stem 33 has a sliding fit within the bore of the valve body, and its radially inner end abuts the ellipticalportion of shaft 24. The valve is urged toward its seat by a spring 34 engaged between a flange on the valve and a cap 35 screwed or otherwise secured in the outer end of the valve body. 1

When handles 23 are in neutral position the ellipticalportion of shaft 24 is disposed with its major and minor axes bisecting the angles between valves 3. The valve stems are proportioned so that when the shaft 23 is in this position all the valve rods 33 contact shaft 23 at points equidistant from the shaft center, yet the valves are seated to prevent circulation of liquid through casing 22. Such engagement of the valves with their seats would, of course, prevent further inward movement of the valve stems.

If shaft 24 is now rotated by movement of handles 23 the major axis of the elliptical shaft portion will be rotated toward one pair of valves 3 disposed diametrically oppositely, so that K the valve stems 33 of these valves will be forced outward to open such valves and the extent of movement of both stems thus effected will be the same. Simultaneously the minor axis of the elliptical shaft portion 2a will be rotated toward the other pair of diametrically opposite valves, but they will not be moved because the shaft surface will be retreating from their stems 33 to leave a small space between them and the shaft. Such valves will therefore remain closed. If the handles 23 were rotated in the opposite direction, however, this latter pair of valves would be opened equally while the pair of diametrically opposite valves opened by the first mentioned operation would remain closed.

In whichever direction shaft 24 is rotated about its axis, therefore, one pair of valves will be opened and the other pair of valves will remain closed. Each pair of oppositely disposed valves may be connected between the elevating motor M and the supply and return conduits and I5, respectively, of the fluid supply system. Thus, for example, the supply conduit may, as shown in Figure 4, be connected by a duct 36 to one side of each of the two lower valves. The outflow side of one of these valves will be connected by a duct 31 to one side of the motor l4, while the outflow side'of the'other valve will communicate through a duct 38 with-the other side of this motor. The lower valves, therefore, will control supply of liquid under pressure to the elevating motor, and since, as previously pointed out, only one of these adjacent valves can be opened at any given time by rotation of shaft 24, the liquid can flow only to one side or the other of the motor.

The upper valves in casing 22, on the other hand, control return of liquid from the conduits communicating with motor M to the return pipe l5 connected to reservoir l9. Since the conduits connected to motor l4 serve alternately as supply and return passages, ducts 31 and 39 will be connected also to one side of the two upper valves, respectively, as shown in Figure 4. The upper or outflow sides of both of these valves are connected by a duct 39 to return conduit |5. In

order to facilitate drilling of the passages through casing 22 it will be convenient, as shown in all of Figures 2, 3, and 4, for duct 39 to extend centrally and vertically through the casing to intersect the bore through which shaft 24 passes,

which bore will consequently form part of this duct. In order to isolate the several ducts properly from each other suitable packing or gaskets will be located between various parts of each valve. body 30 and the casing 22, as well as between the valve stem 33. and the valve body of each valve unit.

If shaft 24 is rotated about its axis it will be seen that one of the lower supply valves will be opened to connect passage 33 with one or the other of motor ducts 31 and 38, for flow of liquid through it to the motor. Simultaneously the diametrically opposite upper return valve will be opened to establish communication between the other motor duct and return passage 39, so that liquid expelled from the motor may return to the supply system in an amount corresponding to that delivered from pipe II.

It will further be evident that the farther shaft 24 is rotated the greater will be the displacement of both of such opened valves from their seats, to increase the rate of flow of liquid to motor It and the flow back from it, and consequently the faster will the gunbe elevated or depressed. Also spring ring 21 will be tensioned proportionally to the degree of control handle rotation, so that when they are released the shaft 2t will be returned promptly to the neutral position shown in Figure 3, permitting the openedvalves to be closed by their respective springs 34, and simultaneously terminating movement of the gun.

lihe valve mechanism housed in casing 2|. which controls the operation of traversing motor I3, is similar to that described. In this assembly the valve operating shaft is not connected directly to control handles 23, but rather to the easing 22, which is rotatable with respect'to the lower stationary block of the unit 2, including central section 29 and valve casing 2|. Shaft d, as shown in Figure 2, extends axially through this block, and its portion in casing 2| may be formed as an element 49 separate from the upper portion of the shaft, and which is of elliptical cross section corresponding to the shape of the central portion of shaft 2a in Figure 3. These two parts of shaft 4 may be connected for rotation of part 40 by rotation of the upper part in any suitable manner, such as by the key shown in Figure 2.

For convenience of manufacture shaft 5 may be formed as a unit separate from casing 22. In any event all the ducts extending downward from the valves in such casing continue axially through shaft 4, where they communicate with annular grooves formed in its periphery, which register,

respectively, with the connections for the condults leading to motor I! and with supply and return conduits II and I5. This arrangement enables all the conduits connected with our control unit to be stationary, so that flexible conduits are entirely unnecessary. While these grooves may be formed encircling the shaft to simplify manufacture, it would be suflicient for them to have a circumferential extent only equal to the maximum rotation of shaft 4, which does not exceed forty-five degrees. Alternating with these grooves in shaft 4 communicating with the several passages extending through it are additional grooves accommodating suitable packing rings, which may be of rubber, acting to seal each duct groove from the groove or grooves adjacent to it.

The ducts in casing 2| establishing communication between the supply and return conduits II and i5 and the conduits connected to the traversing motor l3, correspond precisely to the ducts in casing 22. Thus the inlet conduit communicates through duct 36 withone side of each of the right and farthest valves, while the left and nearest valves each have one side communicating by duct 39' with the return conduit ii. A passage 31' connects the other side of each of the nearest and right valves to one conduit extending to motor i3, while duct 38' connects the other sides of the left and farthest valves to the other conduit leading to motor i3.

As handles 23 are swung conjointly to one side or the other, either with or without simultaneous rotation of shaft 24, casing 22 will be rotated about a. vertical axis to revolve 'shaft 4 and its elliptical portion ill. As previously described in connection with the valve arrangement in casing 22, opposite valves in casing 2| will be opened,

while the othervalves will remain closed. This opertion will establish communication from supply conduit ll through duct 36' to one or the other of motor ducts 31' and 38', depending upon the direction in which the control handles are 4 8 rotated and swung, the gun may be moved in elevation and in traverse, not only in diiferent degrees, but at varying speeds.

Our control unit affords such versatilityof operation without placing any stress on connections to the various conduits, for, with the exception of those communicating with motor it, all the conduits are connected to the stationary central section 20 of the unit. The pipes for motor I 3 are connected directly to casing 2|, but this arrangement is not objectionable because such casing likewise is stationary, only casing 22 being mounted for movement.

We claim as our invention:

1. Hydraulic control mechanism for use with an elevating motor and a traversing motor,- comprising a stationary block, ducts in said stationary block including two traversing motor ducts, two elevating motor ducts, a hydraulic liquid supply duct and a hydraulic liquid return duct, traversing valve means carried by said stationary block below said ducts and controlling communication between the traversing motor ducts and the supply and return ducts, an upright shaft received in and rotatable relative to said stationary block, a movable casing above said stationary block and integral with the upper end of said upright shaft, elevating valve means carried by said casing, said casing and said upright shaft having cooperating passages extending therethrough operable to establlsh communication between said elevating valve means, said elevating motor ducts, and said swung. Simultaneously opening of the diametrically opposite valve will establish communication between the other duct for motor l3 and return duct 39'.

Rotation of shaft 4 during such operation will not interrupt communication between the passages extending axially through it and the connections to conduits II and i5 and to the elevating motor conduits because of the peripheral shaft grooves interposed between the stationary and movable portions of the ducts in the central section 20. When the handles are released spring 21', which has been tensioned by such rotation of casing 22 and shaft 4 relative to the lower block, will return these parts into neutral position. Such movement will dspose the elliptical shaft portion relative to casing 2| so that its major and minor axes bisect the angles between the valves in such casing, and consequently they will all be closed.

It will thus be seen that the handles 23 may be rotated only to turn shaft 24 about its axis,'if desired, to drive motor id for merely elevating or depressing the gun, Alternatively the handles may be swung to control valves in casing 2| by rotation of casing 22 and shaft 4 for operating motor l3 only. to traverse the gun in one direction or the other. In addition, however, the control handles may be rotated and swung simulaneously to effect combined operation of motor ll in either direction with motor I3 in either direction, to effect simultaneous traversing and elevational movement of the gun. Moreover, depending upon the extent to which handles 23 are supply and return ducts in various rotated positions of said casing relative to said stationary block, said upright shaft having a solid lower end cnga/gea-ble with said traversing valve means and operable to actuate the same for operating the rotating motor by rotation of said shaft, a transverse shaft extending through said casing perpendicular to said upright shaft, and having a solid control portion engageable with said elevating valve means and operable to actuate the same for operating the elevating motor by rotation of said transverse shaft, and control handles mounted upon the opposite ends of said transverse shaft, movable to rotate said transverse shaft about its axis and to swing said transverse shaft for rotating said casing and said upright shaft, to effect separate or conjoint operation of said elevating and traversing valve means for establishing and controlling flow of liquid through said traversing motor ducts and through said elevating motor ducts separately or simultaneously.

2. Control mechanism for use with an elevating motor and a traversing motor, comprising a stationary block, a traversing motor conduit and an elevating motor conduit connected to said stationary block, an upright shaft Journaled in said block, traversing valve means including a plurality of units. each incorporating a valve and a valve seat. carried by said stationary block, distributed about said upright shaft and operatively connected therewith, the valves and valve seats of said units being relatively reciprocable by rotation of said upright shaft, to control flow of fluid through said traversing motor conduit. a movable casing rotatable with said upright shaft, a shaft extending transversely of said casing, ele'vating valve means including a plurality of units, each incorporating a valve and a valve seat, carried by said casing, distributed about said transverse shaft and operativelv connected therewith, the valves and valve seats of said elevating valve means units being relatively reciprocable by rotation of said transverse shaft. to control flow of fluid through said elevating motor conduit, and means establishing communication between said elevating valve means and said elevating motor conduit connected to said stationary block.

3. Control mechanism for use with an elevating motor and a traversing motor, comprising a stationary block. a traversing motor conduit and an elevating motor conduit connected to said stationary block, an upright shaft journaled in said block and having a portion generally elliptical in cross section, traversing valve means including a plurality of units, each incorporating a, valve and a valve seat, carried by said stationary block, distributed about said upright shaft and engazeable by the generally elliptical portion thereof, the valves and valve seats of said units being relatively reciprocable by rotation of said upright shaft to vary progressively the quantity of flow through said units corresponding to increased shaft rotation, to control flow of fluid through said traversing motor conduit at a correspondingly varying speed, a movable casing rotatable with said upright shaft, a shaft extending transversely of said casing and having a portion generallyelliptical in cross section, elevating valve means including a plurality of units, each incorporating a valve and a vale seat, carried by said casing, distributed about said transverse shaft and engageable by the generally elliptical portion thereof, the valves and valve seats of said elevating valve means units being relatively reciprocable by rotation of said transverse shaft to vary progressively the quantity of flow through said elevating valve means units corresponding to increased shaft rotation, to control flow of fluid through said elevating motor conduit at a correspondingly varying speed, and means establishing communication between said elevating valve means and said elevating motor conduit connected to said stationary block.

4. Hydraulic control mechanism for use with transverse shaft about its axis and to swing said transverse shaft for rotating said casing and said upright shaft, to effect separate or conjoint operation of said elevating and traversing valve means for establishing and controlling flow of liquid through said traversing motor conduits and said elevating motor conduits separately or simultaneously.

5. Hydraulic control mechanism for use with an elevating motor and a traversing motor, comprising a stationary block, conduits connected to said stationary block including two traversing motor conduits, two elevating motor conduits, a hydraulic liquid supply conduit, and a hydraulic liquid return conduit, an upright shaft received in and rotatable relative to said stationary block, having a lower portion generally elliptical in cross section, traversing valve means including a plurality of units, each incorporating a valve and a valve seat, carried by said stationary block, spaced angularly approximately 90 degrees about the generally elliptical lower portion of said upright shaft and engageable thereby, the valves and valve seats of said units being relatively reciprocable along lines perpendicular to said upright shaft by rotation thereof, to control flow of liquid through said traversing motor conduits, a movable casin above said stationary block and integral with said upright shaft, a transverse shaft extending through said casing perpendicular to saidupright shaft and having a central portion generally elliptical in cross section, elevating valve means including a pluralityof units, each incorporating a valve and a valve seat, carried by said casing. spaced angularly approximately 90 degrees about the generally elliptical central portion of said transverse shaft and engageable thereby, the, valves and valve seats of said units being relative- 0 ly reciprocable along lines perpendicular to said an elevating motor and a traversing motor, com- I prising a stationary block, conduits connected to said stationary block including two traversin motor conduits, two elevating motor conduits, a hydraulic liquid supply conduit, and a, hydraulic liquid return conduit, an upright shaft received in and rotatable relative to said stationary block. traversing valve means including a plurality of units, each incorporating-a valve and a valve seat, carried by said stationary block, distributed about said upright shaft and engageable thereby. the valves and valve seats of said units being relatively reciprocable along lines perpendicular to said upright shaft by rotation thereof, to control flow of liquid through said traversing motor conduits, a movable casing above said stationary block and integral with said upright shaft, a transverse shaft extending through said casing perpendicular to said upright shaft, elevating valve means including a plurality of units, each incorporating a valve and a valve seat, carried by said casing, distributed about said transverse shaft and engageable thereby. the valves and valve seats of said units being relatively reciprocable along lines perpendicular to said transverse shaft by rotation thereof, to control flow of liquid through said elevating motor conduits, said casing, upright shaft, and stationary block having cooperating passages extending therethrough operable to establish communication between said elevating valve means.

said elevating motor conduits, and said supply and return conduits in various rotated positions of said casing relative to said stationary block, and control handles mounted upon the opposite ends transverse shaft by rotation thereof, to control flow of liquid through said elevating motor conduits, said casing, upright shaft, and stationary block having cooperating passages extending therethrough operable to establish communication between said elevating valve means, said elevating motor conduits, and said supply and return conduits in various rotated positions of said casing relative to said stationary block, and control handles mounted upon the opposite ends of said transverse shaft, swingable to rotate said transverse shaft about its axis and to swing said transverse shaft for rotating said casing and said upright shaft, to effect separate or conjoint operation of said elevating and traversing valve means for establishing and controlling flow of liquid through said traversing motor conduits and said elevating motor conduits separately or simultaneously.

JOHN P. LIDRA MITCHELL M. BERRY.

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

UNITED STATES PATENTS Number Name Date 1,285,814 Silsbee Nov. 26,- 1918 2,057,088 DeMillar Oct. '13, 1936 2,221,462 Trainbly Nov. 12, 1940 2,284,611 Barnhart May 26, 1942 2,293,555 Mercier Aug, 18, 1942 2322518 Huber June 22, 1943 2,387,007 Buchanan Oct. 16, 1945

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