US2448675A - Control mechanism for a plurality of motors - Google Patents

Description

Sept. 7, 1948. P. L. LOEWE 2,448,675

CONTROL MECHANISM FOR A PLURALITY OF MOTORS Filed Nov. 6, 1943 2 Sheets-Sheet 1 42 60 2 40 61 8 MOTOR CIRCUIT T 212 mom PUMP 44 32 76 EXHAUST T0 RESERVOIR 3 a0 37' 5 Morofi c/Rcu/T Ezvenzor Pete?" llioewe Sept. 7, 1948. P. L. LOEWE 2,448,675

- CONTROL MECHANISM FOR A PLURALI'IY OF MOTORS I Filed Nov. 6, 1945 v 2 Sheets-Sheet 2 I Jltorn 631,5

Patented Sept. 7, 1948 CONTROL MECHANISM FOR A PLURALITY OF MOTORS Peter L. Loewe, Kalamazoo, Mich.

Application November 6,. 1943, Serial No. 509,255

12 Claims.

My invention relates to an improvement in control devices and has for one purpose to provide a control device which may be employed to control the operation of motors performin different functions and which are employed either simultaneously or at different times.

Another purpose is to provide control means for employment with a hydraulic circuit in which a plurality of motors are actuated from a common source of hydraulic pressure.

Another purpose is to provide an improved valve control system for hydraulic circuits.

Another purpose is to provide an improved system of power transmission which may be used in connection with control valves or other devices.

Another purpose is to provide an improved hydraulic circuit.

Other purposes will appear from time to time throughout the specification and claims.

The present application is a continuation in part of my co-pending application Serial No. 463,870, filed on the 30th day of October, 1942, now abandoned.

My invention is illustrated more or less diagrammatically in the accompanying drawings, Wherein Figure 1 is a section with parts in elevation;

Fig. 2 is a detail:

Figure 3 is a section along Figure 1;

Figure 4 is an elevation;

Figure 5 is a diagrammatic illustration of a circuit with which the valve control shown in Figure 1 may be employed;

Figure 6 is a partial transverse section; and Figure 7 is another diagram' illustrating the use of a single motor.

Referring first to Figure l, I illustrate a valve assembly housing generally indicated as A and including an end housing portion I, an intermediate housing portion 2, and an opposite end housing portion 3. The various portions are secured together in any suitable manner for example by screws 4.

As will later appear, the interiors of the various parts are in communication or may be put in communication hydraulically with each other. Referring to Figure 5, for the general circuit, 5 indicates any suitable fluid reservoir from which the fluid may be withdrawn along the pipe 5 to the line 3-3 of the pump 1 from which the fluid is delivered along the pump delivery pipe 8. The pipe 8 is shown as terminating at the intermediate member- 2, of the valve assembly generally indicated as A.

My control device is illustrated, in Figure 5, in

connection with a hydraulic circuit in which two individual motor circuits may be supplied with fluid under pressure from the reservoir 5 by the pump 1. Where, as in Figure 5, two separate systems are supplied from a single fluid source by a single pump, it is important that the flow to the two circuits or to the two power consuming devices be distributed without affecting volume and pressure delivered to one by withdrawing fluid from the other. 1 Considering the specific control valves shown, I illustrate in the housing portion 3, with its removable end plate 3a, an open ended valve cylinder H], having ports arranged in three groups, as at H, l2 and [3. The movable valve piston I4 is provided with slots I5, l6 at its ends and with intermediate slots 11. The valve may be actuated by any suitable link l8 pivoted as at'l9. The link is pivoted, as at 20, to ears 2| outwardly extending from a sleeve 22 which is rotatably mounted in a securing ring 23, which engages a bottom flange 24, permitting rotation of the sleeve 22 while preventing its endwise movement. The sleeve 22 is rotated by rotation of the control rod 50. The piston [4 when in the position in which it is shown in Figure l, closes the motor circuit controlled thereby. Solid cylindrical surfaces 25, 26 are effective to close the ports II and IS. The ports II and I3 in turn communicate with circumferential passages Ha, 13a which are in communication with pipes 29, 3B, which constitute a fluid circuit for the motor 3|, diagrammatically shown in Figure 5. Since the details of the motor do not of themselves form part of the present invention, the motor is indicated only diagrammatically.

32 is an exhaust passage extending from the housing portion 3 to the fluid reservoir 5. It will be observed that the piston I4 can be moved in one direction, by rotation of the sleeve 22, to connect the ports H and I2 and to deliver fluid along the pipe 29. A movement of the piston M in the opposite direction will put the ports l2 and [3, in commlmication, and cause the delivery 3 of fluid under pressure along the pipe 30, thus reversing the motor. When the piston i4 is in the neutral position in which it is shown in Figure 1, there is no useiul pas-sage of fluid through the circuit to the motor 3 1.

Another motor circuit is controlled by the valve piston which is longitudinally movable in the fixed open ended cylinder 4 I, provided with upper slots 40a, intermediate slots 40c and lower slots 4%, and with ports 42, 43 and 44, in communication with circumferential passages 42a, 43a and 44a. When the piston 40 is in the neutral position in which it is shown in Figure 1, the ports 42 and t4 are closed and no fluid moves along the circuit including the pipes 45 and 46. When the piston 48 is raised, referring to the position in which the parts are shown in Figure- 1, th ports 42 and 43 are connected and fluid is delivered along the pipe 45. When the piston 40 is lowered, the ports 43 and 44 are connected and fluid is directed along the pipe 4'5: Thus themotor 4'! shown diagrammatically in Figure 5, may be reversibly actuated, depending upon the position of the cylindrical closure surfaces 48 and 49 of the piston 40. The piston 43 may be actuated by longitudinal movement of the control rod 59. The control rod is provided with collars 51,. 52 which constrain the piston 4K! to endwise movement with the rod 50. Any suitable means such as the key I00, may be employed for preventing rotation of the piston 46 when the rod is rotated, The rod 56 is provided with a squared bottom portion 53 which penetrates a square aperture in the sleeve 22. Thus it will b understood that rotation of the rod 58 will move the piston I4 and endwise movementof the rod 50 will move the piston 40.

In order to obtain the proper distribution of flow between the two motors without affecting volume and pressure delivered to the one by withdrawing fluid for the other, I employ a control valve which is normally seated in a neutral position but which is moved from that neutral position in responseto or in timed relation to any movement of either of the pistons 14 and 40.

I illustrate the fixed open ended cylinder 60 with a piston 61 therein having a hollow portion 62- in communication with one end, the opposite end being shown as solid, and being provided with lugs 84' to which the actuating tension link 65 may be pivoted as at 66.

When the parts are in the neutral position in which they are shown in Figure 1, and assuming that the pump 1 is constantly operated, fluid is constantly delivered from the pump along the pipe 8' through the wall of th intermediate valve housing member 2. This pressure is effective in the passages indicated by 8a, and in the areas r22 and 43a. In connection with the inlet area is the circumferential passage [2a, aligned with the ports [2 in the valve cylinder 10 and the circumferential passage 43a, in communication with the ports 43 in the valve cylinder 4| With the parts in neutral, as in Figure 1, both motor circuits are closed. The piston portions 25 and 26 constitute in effect, closed valves,- having the effect of throttle valves, at each side of the motor 31. Simdaily the cylindrical portions 48 and 49 of the piston 40 constitute closed valve members, having the effect of throttle valves, at each side of the motor 41, However, the piston BI is in open positi'dn and the fluid delivered under pressure from the pump along the pipe 8 to the areas 8a flows through the ports 64a and 60b of the valve cylinder 60, and along the slots Bla and Blb. Fluid delivered along the slots Bla flows inwardly through the ports 62a to the hollow portion 62 of the piston SI and thence to the intermediate exhaust area 32a. Fluid delivered along the slots Elb flows past the upper end of the piston 6| to an upper portion of the exhaust area 32a. It will be noted that the slots Sla and Blb are reduced at their lower ends to provide a relatively gradual chang in volume and pressure, when the piston is moved from the neutral position in which it is shown in Figure 1, the piston 6| performing the function of a wide open bleeder Valve. The entire output of the pump passes the piston Iii, to the exhaust areas 32a, and thence along the exhaust passage 32, and no pressure is built up.

It will be understood that the unitary control rod or member 50 serves as a Control means for all of the pistons above described. Any suitable" means may be employed for selectively rotating or imparting endwise movement to the rod 50. I illustrate for example a rotatable coll ar sat with an upwardl extending arm 9m to which is pivoted, as at 92a, 9, control lever 93a having a control handle 94a guided in a slot 96a in the arm 95a which extends upwardly from the collar Qlla opposite the arm 9la. The operator may move the rod 50 up and down by moving the handle 94a up and down, or he may rotate the rod about its axis by employing the handle 94a to rotate the collar 90a, and thus the rod 59, or he may perform both movements at once. 91a is any suitable connection between the rod 5t and the lever 93a which constrains the rod 5!? to rotate when the collar 99a is rotated, and which constrains it to vertical movement when the handle 94a is raised or lowered, any suitable clearance being provided to prevent binding, It will be understood that the manual control device thus shown is basically diagrammatic or illustrative and the conventional controls used in airplanes, tanks or the like, or in connection with the sighting of artillery, may be employed.

Whenever either piston [4 or 49 is moved from i .7 the neutral .position of Figure 1, it is necessary to reduce the passage of fluid permitted by the piston tl, and to move 6| toward pressure building position, In the particular embodiment of my invention herein shown, I therefore provide means, responsive to the movement of the rod 53 for moving the piston 6| toward pressure building position, when either piston 54 or 4!) is moved toward circuit opening position.

Referring to the specific structure shown, the piston 6-1 is held in neutral position by the spring 'lll, which is compressed between the top of the [cylinder GI and the fixed abutment 18a.

15, it constitute abutments which may be fixed on or unitary with the housing portion 1'. Seated on them is the arm 11 with its circumferential ring or sleeve '18, surrounding the rod 50, and its hook 19 which passes through the lower slot of the tension member 65. The ring 18 is provided with generally diametrically opposedcam portions 8!, which are opposed to a pin or pins 82 which extend diametrically from opposite sides of the control rod 50, one pin end being shown in Figure 1. 83 is a fixed abutment in an upper portion of the housing I. 84 is a lever pivoted in relation to the housing, as at 85. The lever 84- terminates in a hook 86 which passes through the upper slot 8'! of the tension member 65. At the opposite side of the pivot 85, the lever 84 carries a circumferential ring or sleeve 38 which is provided with opposite cam surfaces 89 opposed to the pin 90, extending diametrically iromopposite sides of the, rod 50, one end of the pin appearing in Figure, 1. 9! is a coil spring compressed between the sleeves l8 and 88. 92 is a guiding cylinder for the ring '18, which may be permanently secured thereto, and which is surrounded by the spring 9|.

In considering the mechanical operation of the device, and assuming that the parts .are initially in the positions in which all parts are shown in Figure 1, assume that the shaft is rotated in such fashion as to move the pins 82 and 9D to the right, referring to theposition of the parts as shown in Figure 1. The end of the pin .82 shown in Figure 1, will engage the visible cam 81 of Figure 1, and will bodily raise the member 11 from the fixed abutments l5 and 16. This in turn will raise the tension member 65 and raise the piston 6| against the compression of the spring 10,. and reduce the flow of fluid past the piston 6|. If the movement is continued far enough, the solid cylindrical portions 6 lo and Bld of the piston 6| will eventually close the ports a and 60b, and no fluid will be by-passed. It will be understood that in the initial neutral position of Figure 1, all of the fluid is by-passed, none being delivered to either motor circuit. Rotation of the shaft 50 actuates the valve piston l4 and permits the passage of fluid under pressure through the circuit including the pipes 29 and 3D to the motor 3|. Rotation in one direction delivers the fluid along the pipe 29; rotation in the opposite direction delivers the fluid along the pipe 30, If a reversible fluid motor is employed, a reversal of its direction may thus be obtained by varying the direction of rotation of the rod 50. Regardless of which direction the rod 50 is rotated, the piston 6| will be moved toward pressure building position, as there are cams 8i and pins 82 at each side of the rod 50, those of one side only being shown in Figure 1.

When the shaft is rotated the pin 90 also engages the cam 89 and the lever 84 is rotated to lift the hook 86. The parts may be so proportioned thatit is the lever 84, primarily, which raises the member rather than the arm 11. In any event, rotation of the shaft 50 in either direction moves the piston 61 against compression of the spring 10, and thus reduces the bypass floW. 1

If the operator wishes to pass fluid through the circuit to the motor 41, he raises or lowers the rod 50. If he raises the rod 50, the piston 40 is raised and fluid is delivered along the pipe 45. If he lowers the rod 50, fluid is delivered along the pipe 46. Thus, if the motor 4'! is a reversible fluid motor, its direction of movement may be controlled by raising or lowering the rod 50. When the rod 50 is raised, the pins 82, which are in engagement with the cam surfaces 8|, bodily raise the member 11 and thus lift the piston 6| against compression of the spring 10. When the rod 5|] is lowered,the pins 90 engage the cams 89 and rotate the lever arm 84 and thus raise the piston 6| against compression of the spring 10.

- It will be understood that the parts can be proportioned to suit a variety of particular prob-. lems. If, in order to obtain a simultaneous actuation of both motor circuits, the rod 50 is both rotated and raised or lowered, the piston 6| is still moved toward cut-off position. Assume that the rod is first rotated, the lever arm 84 and the arm 11 'will both be moved toward piston raising position... The pins 82 and 90 will always be in con- I illustrate diagrammaticallya bleeder valve B. When the bleeder valve is fully open, all the fluid is by-passed to the reservoir 5. This :position corresponds to the position inwhich the piston 6| is shown in Figure 1, and no fluid is passing to either motor circuit. When the valves 25 and 26, which control the circuit for the motor 3!, are opened, then the bleeder valve B is partially closed, to reduce the by-passing of fluid. For simplification, the connections between the bleeder valve and thethrottle valves of the motor circuits are not shown in the diagram, or the means for reversing the direction of flow in the motor circuits. l

It will be realized that whereas I haveLillustrated my invention as connected to a hydraulic system, the particularmechanical means shown in Figure 1 may be employed in other connections.

Figure 7 illustrates a simpler circuit, in which only a single motor is employed. It illustrates any suitable reservoir lei with a pump 102 which draws fluid through thepipe Hi5 and delivers it along the. pipe I06 to the motor I03. I04 indicates the fluid in the reservoir. H0 is any suitable bleeder or by-pass valve between pump and motor. i0! is the exhaust pipe for the motor to the reservoir. III is a valve in the exhaust pipe on the exhaust side of the motor and H2 isa valve on the pump side of the motor I03. The two circuits, and the structure as shown in Figure 1, have in common that the relationship between output speed and, torque may be more accurately controlled. than has heretofore been possible.

While Ihave illustrated my invention. diagrammatically as applied to a hydraulic pump and a hydraulic motor, it will be understood that the hydraulic pump is merely exemplary of any means whereby fluid, preferably though not essentially liquid, may be supplied under pressure to a system such as by an elevated reservoir, an accumulator, or any one of a number of possible sources of fluid under pressure which are conceivable and would operate satisfactorily in con nection with my invention.

The motor also is shown diagrammatically because it is exemplary of any one of a large number of possible uses of fluid pressure. For instance, a motormay be regarded as a piston operating in a cylinder of infinite length. The motor might be a positive displacement motor or it might take the form of a turbine, and a wide range of relationships between fluid pressure power source, and fluid pressure power using elements are all involved'as possible mechanical exemplifications of the solutions of the power problem which I propose. The number of motors employed may be varied from the single motor shown in Figure "7 to a multiplicity of motors with circuits for each motor.

In both circuits there is included, a reservoir of fluid, a pump which draws fluid from the reservoir and a motor or motors to which the pump delivers. Interposed between the pump and the motoror .motors is va bleeder valve to any suitableby-pass valve, such as the cylinder 6.0 and its piston =61. The relationship between the bypass valve and the valves controlling the flow to the motor or motors is exceedinglyimportant. They may be manually controlled; they may be automatically controlled; they can be separately controlled to produce the desired result. They are preferably controlled in unison, as in the structure illustrated .in detail in Figure 1.

With reference to .Figure 5, the torque of 'motor .41 is controlled primarily bythe valve 49, operating in conjunction with the valve 48 and b'y-pass B. The valve 49 is on thedischarge or exhaust side 01 the motor 41. Similarly, the valve 26 of Figure 5, controls the torque of motor 3 in conjunction with valve .25 and bypass B.

In the structure shown in Figure 1 and relating it to the diagram of Figure 5, the functions of valves 48 and 49 are performed by the valve portions 25 and 26 of piston i l. Furthermore, the functions of valvesZll and 25 are equally performed by the valve portions 48 and 59 of piston 40. Figure varies from Figure 7 in that it illustrates the addition of a, second motor circuit or sub-circuit to the basic diagram of Figure 7. In the operation of the device, starting in neutral with the by-pass valve open, the entire output of the pum will be by-passed and no energy is used. When the valves are connected together .to work in unison as in Figure 1, as one or both of the pistons Her 46 begin to open, the piston 61 begins to close. The relative speeds of movement of .the various valves can be established or varied to suit the particular problem solved.

It will be realized that Whereas I have shown and described an operative device, still many changes might be made in the size, shape, arrangement and number of parts without departin materially 'from the. spirit .of my invention I wish, therefore, that my showing be regarded as in a broad sense as diagrammatic and illustrative rather than as a limitation to my precise showing.

For example, it will be understood that the details of the valves and of the connections between the valves may be widely varied. Where in the claims, I employ the term throttle valve or bleeder valve, I wish it to be understood that these terms are to be interpreted broadly .and not as limiting me to any specific valve de- :tails, not actually set out in the claims. For example, I wish the term bleeder valve tobe interpreted sufficiently broadly to cover any valve means for providing a variable fluid by-pass, Within a range of zero to maximum. I .wish the term throttle valve to be interpreted with suflicient breadth to cover any valve means for .varying the fluid flow through the motor circuits within a range of zero to maximum.

It will be noted that all of the various grooves have gradually changing or reduced insideedges in order to produce a gradual admission or reductic-n of fluid.

Whereas I have illustrated a circuit in Figure 5 in which two motor sub-circuits are employed and I show in Figures 1 to 4 a structure .embodying the circuit of Figure 5, it will be understood that not only can the single circuit sys tem of Figure '7 be employed but that circuits having a greater number of motor sub circuits can also'be employed.

I claim:

1. In a controldevice for fluidsystems, an actuating member mounted for rotational :and for non-rotational movement, a valve member mounted for movement in response to non-rotational movement of the actuating member, a second valve member and means for moving it in response to rotation of said actuating member, and a third valve member and means for moving it in response to eitherrotational or non-rotational movement of the actuating member.

2. -'In .a control device for hydraulic systems,

an actuating membermounted for rotational and for non-rotational movement, a valve member and means for moving it longitudinally in response to non-rotational movement of said actuating member along its axis, means for holding said valve member against rotation, a second valve member and means for movin it in response to rotation of said actuating member, and a third valve member and meansfor moving it in response to either rotational or non-rotational movement-of the actuating member. 3. In a control device for hydraulic systems, an actuating member mounted for rotational and for non-rotational movement, a valve member and means for moving it longitudinallyin response to non-rotational movementof said aotuating member along its axis, means for holding said valve member against rotation, a second valve member and means {or moving it in resp-onse to rotation of said actuating member, and a third valve member and means for moving it in response to either rotational or-non-rotational movement of the actuating member the path of movement of the second valve member being generally at right angles to the path of movement of the first valve member.

l. A hydraulic system including a pump, a plurality of motors, a separate circuit for each said motor, a'hydraulic fluid supply from which the pump may draw fluid, and to which the motors may exhaust fluid, a bleeder valve interposed between the pump and both motors and motor circuits, and adapted to be moved to control the discharge of motive fluid under pressure from the pump, a throttle valve interposedbetween the bleeder valve and the 'motor of each said circuit, and means for operating said valves in unison.

5. A hydraulic system including a pump, a.plu-- rality of motors, a separate circuit for each said motor, a hydraulic fluid supply from which the pump maydraw fluid, and to which the motors may exhaust zfiuid, a bleeder valve interposed between-the pump and both motorsand motor circuits, and adapted to be moved to control the discharge of motive fluid under pressure from the pump, and a throttle valve interposed between the bleeder valve and the motor of each said circuit and means for normally holding said bleeder valve in position to permit the-pump to return all .fiuid .directly to the hydraulic fluid supply.

6. A hydraulic system including a pump, a plurality of motors, a separate cirouit for each said motor, a hydraulic .fluid supply from which the pump may draw fluid, and to which the motors may exhaust fluid, a bleeder valve interposed betweenthe pumpand both motors and motor circuits, and adapted'to be moved to control the discharge .of .motive fluid under pressure from the pump, and a throttle valve interposed between the bleeder valve and the motor of each said circuit, and means for normally holding said bleeder valve in position to permit the pump to return allfluid-directly to the hydraulicfluid supply, rmeans for selectively actuating-said throttle valves and means for moving said bleeder valve toward pressure building position when any of said throttle valves are actuated.

7. In a hydraulic system and control means therefor, a motive fluid reservoir, a pump, a pump inlet duct extending from said reservoir to said pump, a bleeder valve in the line of delivery from said pump to said reservoir, a plurality of fluid motors, a circuit for each said motor, in circuit with said pump and reservoir through said bleeder valve, throttle valves, in each said circuit, on each side of the motor in said circuit, and means for actuating said throttle valves and said bleeder valve, said bleeder valve being normally in a neutral position in which it permits the return of all fluid delivered by the pump to the reservoir.

8. In a hydraulic system and control means therefor, a motive fluid reservoir, a pump, a pump inlet duct extending from said reservoir to said pump, a pump outlet duct extending from said pump to said reservoir, a bleeder valve in the line of delivery from said pump to said reservoir, a plurality of fluid motors, a circuit for each said motor, in circuit with said pump and reservoir through said bleeder valve, throttle Valves, in each said circuit, on each side of the motor in said circuit, means for actuating said throttle valves, said bleeder valve being normally in a neutral position in which it permits the return of all fluid delivered by the pump to the reservoir, and means for actuating said bleeder valve in response to actuation of any of said throttle valves.

9. In a hydraulic system and control means therefor, a motive fluid reservoir, a pump, a pump inlet duct, extending from said reservoir to said pump, a pump outlet duct extending from said pump to said reservoir, a bleeder valve in the line of delivery from said pump to said reservoir, said bleeder valve being normally in position to permit unrestricted passage of the fluid from the pump to the reservoir, a plurality of fluid motors, a circuit for each said motor, in circuit with said pump and reservoir through said bleeder valve, a control valve for each said circuit, means for actuating each said control valve individually and means for moving said bleeder valve toward pressure creating position in response to movement of any of said control valves.

10. In a hydraulic system and control means therefor, a motive fluid reservoir, a pump, a pump inlet duct, extending from said reservoir to said pump, a bleeder valve in the line of delivery from said pump to said reservoir, said bleeder valve being normally in position to permit unrestricted passage of the fluid from the pump to the reservoir, a plurality of fluid motors, a circuit for each said motor, in circuit with said pump and reservoir through said bleeder valve, a control valve for each said circuit, an actuating element mounted for rotary and non-rotary movement, an actuating connection between said element and one of said valves, adapted to move said valve in response to rotation of said actuating element, an actuating connection between said actuating element and another of said valves, adapted to actuate it in response to non-rotary movement of the actuating element, and means for moving said bleeder valve toward pressure creating position when either of said control valves is actuated.

11. In a hydraulic system including a pump and a motor, conduits leading respectively to the pump, from the pump to the motor and from the motor, a bleeder valve in the conduit between the pump and the motor adapted to by-pass the motor, a throttle valve in the conduit between the pump and the motor adapted to control flow of motive fluid from pump to motor, a throttle valve in the conduit leading from the motor adapted to control discharge of motive fluid from the motor, means for controlling the three valves in consonance to control speed and torque of the motor.

12. In a hydraulic system including a pump and a motor, conduits leading respectively to the pump, from the pump to the motor and from the motor, a bleeder valve in the conduit between the pump and the motor adapted to by-pass the motor, a throttle valve in the conduit between the pump and the motor adapted to control flow of motive fluid from pump to motor, a throttle valve in the conduit leading from the motor adapted to control discharge of motive fluid from the motor, means for controlling the three valves in com sonance to control speed and torque of motor, the throttle valve between the pump and the motor being located on the motor side of the bleeder valve.

PETER L. LOEWE.

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

UNITED STATES PATENTS Number Name Date 1,582,468 Heald et al Apr. 27, 1926 1,686,240 Klausmeyer Oct. 2, 1928 1,724,635 Bath Aug. 13, 1929 1,824,062 Winter Sept. 22, 1931 1,881,471 Gerling Oct. 11, 1932 1,972,462 Schafer Sept. 4, 1934 1,987,909 Parsons Jan. 15, 1935 1,991,349 Gallimore Feb. 12, 1935 2,004,522 Douglas June 11, 1935 2,005,731 Ernst et a1 June 25, 1935 2,005,732 Ernst et al June 25, 1935 2,127,877 Maglott Aug. 23, 1938 2,161,150 Flygare June 6, 1939 2,181,401 Hawthorne Nov. 28, 1939 2,202,216 Madsen May 28, 1940 2,221,308 Dischert Nov. 12, 1940 2,282,977 Mast May 12, 1942 2,285,968 Harrington June 9, 1942 2,297,953 Fulmer Oct. 6, 1942 2,327,920 Moohl Aug. 24, 1943 FOREIGN PATENTS Number Country Date 205,136 Great Britain Oct. 9, 1923 464,891 Great Britain Apr. 27, 1937 371,757 Italy June 2, 1939

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