US2931388A

US2931388A - Electro hydraulic control mechanism

Info

Publication number: US2931388A
Application number: US401176A
Authority: US
Inventors: Wendell E Renick; Kenneth C Goodman
Original assignee: American Brake Shoe Co
Current assignee: American Brake Shoe Co
Priority date: 1953-12-30
Filing date: 1953-12-30
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05

Description

April 5, 1960 w. E. RENICK ETAL 2,931,388

ELECTRO HYDRAULIC CONTROL MECHANISM Filed Dec. 30, 1953 2 Sheets-Sheet 1 INVENTORS FIG 1 WENDELL E. RENIGK KENNETH c. GOODMAN April 5, 1960 I w. E. RENICK ETAL 2,931,388

ELECTRO HYDRAULIC CONTROL MECHANISM Filed Dec. 30, 1953 2 Sheets-Sheet 2 Y INVENTORS 5O WENDELL E. RENICK I;(ENNETH G. GOODMAN 2,931,388 ELECTRO HYDRAULIC CONTROL MECHANISM Wendell E. Renick and Kenneth C. Goodman, Columbus, Ohio, assignors, by mesne assignments, to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Application December 30, 1953, Serial No. 401,176 8 Claims. (Cl. 137623) This invention relates generally to hydraulic apparatus and more particularly to control valve mechanism for hydraulic motors and actuating means for such control valve mechanism.

An object of this invention is to provide a control valve mechanism and actuating means therefor which will make a more accurate governing of the operations of a hydraulic motor possible.

Another object of this invention is to provide a control mechanism for a hydraulic motor which will utilize the movement of a portion of the motor to assist in governing the operation of the motor, another element operating according to a predetermined pattern working in conjunction with the portion of the motor to the end that desired operations may be automatically performed.

A further object of the invention is to provide a novel control valve mechanism having electronically governed pilot means which in turn controls the operation of main valve means and effects the substantially instantaneous response of the motor to control signals irrespective of the manner in which they are transmitted to the system.

A still further object of the invention is to provide a control valve mechanism having a main valve for selec tively controlling the operation of a reversible fluid motor, flow control means for determining the pressures of the fluid supplied to the fluid motor and electro-responsive pilot valve means for effecting the operation of the main valve, suitable electrical circuit means being provided to energize and de-energize the electro-responsive means.

Another object of the invention is to provide a novel circuit arrangement for electronically controlling the pilot valve portion of the control valve mechanism mentioned in the preceding paragraph so that the fluid motor may be caused to perform according to a predetermined pattern or plan and to automatically repeat such pattern of operations as many times as desired.

An object or" the invention also is to provide the electronic control circuit mentioned in the preceding paragraph with an electrical device known as a null bridge and to connect part of such device with a movable portion of the reversible fluid motor and another part with means for moving it according to a predetermined plan, such movement serving to cause an unbalance of the null bridge which in turn directs a signal to the pilot control mechanism making it cause the fluid motor to operate to restore the balance of such null bridge; due to the use of the electronic control circuit extreme sensitivity, speed and accuracy of operation of the fluid motor will be secured.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown.

In the drawings:

Fig. 1 is a diagrammatic view of the hydraulic circuit having a reversible fluid motor and a control valve mechanism formed in accordance with the. present invention innited States Patent corporated therein; the view also showing the electrical circuit for operating the control valve mechanism.

Fig. 2 is a vertical longitudinal sectional view taken through the control valve mechanism shown in Fig. 1.

Referring more particularly to the drawings, numeral 21 designates a reversible fluid motor. In the present instance, the motor 21 is of the piston and cylinder type, the cylinder being indicated by the numeral 22 and the piston by the numeral 23. This piston has a ram 24 projecting therefrom through one end of the cylinder 22. Fluid motors of this type are employed where reciprocatory motion is desired and are particularly employed in hydraulic presses.

The reversible fluid motor 21 is arranged in a hydraulic circuit designated generally by the numeral 25. This circuit has a source of fluid pressure including a reservoir 26, a motor driven pump 27 and a relief valve 28. These elements may be of any desired form and are only diagrammatically illustrated. The hydraulic circuit also includes a control valve mechanism forming part of the subject matter of this invention, this mechanism being designated generally by the numeral 30. A fluid pressure line 31 extends from the pressure source to the control valve mechanism 30 and an exhaust line 32 extends from the valve back to the reservoir. Forward and reverse motor lines 33 and 34 also extend from the control valve mechanism to the reversible fluid motor 21. The circuit further includes a pilot pressure line 35 leading from the outlet of the pump 27 to the upper portion of the control valve mechanism. This pilot pressure line 35 is provided with a pressure reducing valve 35A to limit the pressure supplied to the pilot control mechanism.

The control valve mechanism 30 is shown in detail in Fig. 2. From this figure, it will be observed that the control valve mechanism includes a body 36 and a pair of end caps 37 and 38. The body is provided with a main spool bore 40 having a plurality of annular grooves 41 to 45, inclusive, communicating therewith. In the form of the invention illustrated, the bore is enlarged at one end as shown at 46. The purpose of this enlargement will be set forth hereafter.

Ports

41 and 42 constitute inlet ports and are connected by

passages

47 and 48 with the inlet port 50, this port being connected with the line 31 leading from the fluid pressure source. Body 36 also has a pair of chambers 51 and 52 formed therein, these chambers communicating with the

passages

47 and 48. The chambers may be formed in any desired manner; they are separated by a partition 53. The

passages

47 and 48 are divided into sections by the chambers 51 and 52, certain sections of the passages communicating with the port 50 and the other sections communicating with the

grooves

41 and 42. The points of communication of these sections with the chambers 51 and 52 are longitudinally spaced. The chambers are provided with inserts 54 which form valve seats 55 between the points of communication of the passage sections with the chambers. These valve seats cooperate with valve portions 56 of piston valves 57 which are disposed for sliding movement in the sleeves 54. These piston valves constitute flow control valve elements in the operation of the mechanism.

Grooves

43 and 44 formed in the body 36 are connected by

ports

58 and 60 with the lines leading to the reversible fluid motor. Port 60 constitutes the forward motor port while 36 connect these

ports

58 and 60 with the inner ends of the chambers 51 and 52. The purpose of this connection said grooves providing

spaced heads

64, 65 and 66. The

will be made apparent in the following description.

The main valve bore 40 has a main valve spool 61 disposed for sliding movement therein, this spool having a pair of spaced

grooves

62 and 63 formed in the side wall,

. sume its centered position.

length of the 'g'roovesis such that, when the spool is cen- 40-to port 45 which constitutes the exhaust port, this port being connected by line 32 with the reservoir '26. Spool 61 is normally biased toward this centered position'by'coil springs 67 arranged between the ends of the spool and the end caps 37 and 38. End cap 37 has an adjusting screw 68 threaded therethrough for adjusting the tension of the spring 67. Spool 61'is pilot operated being controlled by a pilot valve indicated generally by the numeral 70. This pilot control valve is disposed in the upper portion of the valve casing 36, a bore 71 extending through the body 3 6 to receive this pilot valve. The end ;caps 37 and 38 have

passages

72 and 73 formed therein to establish communication between the ends of the bore 71 and the main spool bore 40. Bleed passages 74 also connect the

passages

72 and 73 with the exhaust port 45. g The pilot valve mechanism includes a spool 75 having spaced heads 76 adjacent the central portion and

valve stems

77 and 78 extending in opposite directions from the heads 76. These stems are tapered at their outer ends to form metering valves 80, these metering valves 80 cooperating with orifices 81 provided in plugs '82 disposed in the ends of the bore 71. The

stems

77 and 78 extend through central openings in

electromagnetic windl lugs

83 and 84, these windings being positioned in the bore 71 between the plugs 82 and the heads 76 of the valve spool 75. Since the valve spool is in effect a one'piece unit, movement in either direction in the bore 71 will simultaneously increase the effective size or area of the orifice'at one end and decrease the etfective size 'or area of the orifice at the other. The flow of pilot fluid pressure "to the main valve spool will thus be controlled. Heads 76 of spool 75 are provided withorifices 85 to permit flow of fluid from the pilot pressure inletrport 86

'tothe passages

72 and 73 leading to the ends of the main'valve bore40.

Due to the provision of the orifices 85, valve spool 75 operates as a flow divider, the orifices 85 creating a pressure diiferential between opposite ends of the heads 76. As long as the valve spool 75 is centered longitudinally in the bore 71, the effective size of the orifices 81 will be equal and pressure at opposite ends of the valve spool'75 will also be equal. The valve'spool 75 will then be dis posed in its longitudinally centered position. 'If either coil 84 M85 is energized, a magnetic force will be created which will cause the spool 75 to move in response to this magnetic force. When the spool moves in this manner, one of the orifices 81 will be reduced in eflective size while the other will be increased. The reducedorifice will restrict the volume of fluid permitted to flow therethrough and the pressure at the'respective-end of the bore 71 will increase. This pressure will tend to oppose the movement of the spool 75 by the magnetic force and, when the force is sufficiently diminished, will cause the spool to re- When the spool is 'movedtoward either end of the bore 71, the orifice 81 at the opposite end will be increased in eflective size and more fluid willflow through this orifice and be applied to the corresponding end of the main valve spool 61. This additional fluid will cause the main valve spool 61 to move from its centered position toward the opposite end of the valve bot-e40. In 50 moving, the

grooves

62, 63 in'the main valve spool will increase the communicationbetween one 'of

theinlet port

41 or 42 and the

motor port

43 or 44 served thereby at thesame time increasing communication between the other motor porLand the exhaust port 45. Fluid from thepressuresource will then flow to the motor port communicating with the inlet port and the motor 21 will be caused to operate intherespective direction. lithe valve spool were moved in the opposite direction,

itis obvious that the fluid motor would also operate in the opposite direction.

When the magnetic force is reduced sufliciently and the coil deenergized, valve spool 75 will return to its centered position causing the pilot pressure to equalize at the ends of the main spool and this element Will then return to its centered position. .In this position, the piston and ram of the 'hydraulic'motor will be held stationary. It is obvious that, since the piston 23 of the hydraulic motor 21 is of the differential type, the main valve spool may-not occupy a truly centered position to hold the motor piston 23 sta- 'tionary. For purposes of explanation, however, such position of the mainspool will be termed a centered position. To render the main spool 61 more sensitive, it is formed with a piston portion 87 which is disposed for movement in the enlarged portion 46 of the main spool bore. The main spool has a longitudinally extending passage formed therein which communicates with transverse passages so that pilot pressure 'from one end of the spool will be sup plied to the end of the piston 87 connected with the spool. The eflecvtive end areas of the spool 61 will thus beincreased to the end areas of the piston 87. A lower pilot pressure may be employed to operate or effect the movement of the main spool 61 because of the enlarged piston 87. The flow control valve elements are normally urged toward an open position, that is, spaced from the valve seats 55 bycoil springs 88 positioned between the partition 53 and the inner ends of sockets formed in the piston valves 57. The fluid supplied to the inlet port 50 will flow through the

passages

47 and 48 to' the inletports or

grooves

41 and 42. When the valve spool 61 is moved and reduces the degree of communication between either

groove

41 or 42 and the

adjacent groove

62 or 63 in the spool 61, the fluid pressure will increase in the

groove

41 or 42 from which flow is obstructed. 'This fluid pressure will be applied to the .end of the respective piston valve and will tend to movethe valve in opposition to its spring 88. When the valve spool 61 obstructs communication'between the

inlet groove

41 or 42 and one of the

groove

62 or 63 in the spool, the pressure in the latter groove will be reduced, this reduced pressure being applied to the inner end of the associated flow control piston valve 57. The differential in pressure at opposite ends of either flow control valve 57 will cause the valve to move toward a closed position to restrict the volume of fluid admitted to the respective inlet port of the main valve. The springs 88 selected will determine the closing pressure of the flow control valves and, therefore, the volume of fluid supplied to the reversible fluid motor.

Thespool 75 and the

coils

83 and 84 cooperate to form a .motor. This motor is connected with an electrical circuit illustrated in Fig. 1. This electrical circuit includes a source of direct current, indicated by the numeral 90, and alternating

current lines

91 and 92 leading from a suitable sourcerofgpower. These alternating current lines lead to corresponding portions "of

electrical coils

93 and 94, corresponding ends of these'coils being connected by

lines

95 and 96. The

coils

93 and 94 are open to receive for movement therein bars 97 and 98. The

coils

93 and 94 and the bars 97 and 98 form what is known in "the electrical art as a null bridge. Aslong as the bars 97 and 98 occupy arpredetermined position within the coils, the bridge is in balance and nopotential between opposite ends thereof exists. If, :however, one of the bars is displaced longitudinally in either direction from the predetermined position, a potential is created between the opposite ends of the coils. The object herein is to make use of this potential to control the operation of the hydraulic motor.

Line 95 .is connected .by a lead 100 with .one side of the primary coil of 'a;phase splitting transformer 101. The other end of this coil is connected byline 102 with line.96. When one of the bars in the null bridge is moved from its predetermined position in :one direction, a .potential "will be created which will cause a flow of current through .the coil of the transformer. This current will be of a certain phase and will be picked up by the secondary coil 103 of the transformer. If the bar in the coil has been moved in one direction, the phase of current induced in the coil 103 will cause the grid of a power amplifier tube 104 to be energized while, if the bar is moved in the opposite direction, the coil 103 will cause the grid of another tube 105 to be energized. When either of these grids is energized, current will be permitted to flow from the source of direct current 90 through a line 106 and through one or the other of the coils 83 and 84 (in valve mechanism 30) depending upon which of the

tubes

104 and 105 is energized, current flowing from the

particular coil

83 or 84 through

line

107 or 108 to the plate of the respective amplifier tube. The strength of the current permitted to flow through the coil will depend upon the strength of the signal created by the null bridge.

When the null bridge is unbalanced and the signal is created, as above mentioned, the

proper coil

83 or 84 of the motor will be energized and will operate the spool 75 to supply pilot pressure to the proper end of the main valve spool 61 causing fluid to be directed to the fluid motor 21 to make it move in the proper direction to cause the bar 97 carried thereby to move in the same direction as the other bar was moved and to the same extent. When bar 97 reaches a position corresponding to the position of the bar 98, the bridge will be in balance and no potential will exist at that time. Bar 98 may be moved in any desired manner but, for purposes of illustration, a motor driven cam 110 has been shown in registration with this bar. This cam will be provided with a predetermined shape to secure the desired pattern of movement of the ram 24. An electric motor 111 is connected with the cam to cause its operation, the motor being controlled by a rheostat 112. A push button switch 113 may be employed to selectively control the operation of the motor 111 or this motor may be continuously operated by closing a switch 114. The spool 75 will move a distance proportionate to the strength of current supplied to the coils. It will be obvious that the volume of fluid directed to the fluid motor by the main valve spool will depend upon the distance moved by spool 75. As the bar moved by the ram approaches a position corresponding to that of the bar 98, a potential developed by the bridge will decrease and the current supplied to the torque motor will correspondingly decrease. This current will be interrupted when the bridge is in balance and the ram will then stop moving.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

We claim:

1. A hydraulic valve comprising a casing having a valve bore with forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points; a reversing valve spool disposed for movement in said bore, said valve spool having flow directing means operative when said spool is in a predetermined position to form a flow metering orifice between selected inlet and motor passages, said orifice creating a pressure difierential on fluid flowing from the selected inlet to the selected motor passage; a valve element in said casing for controlling fluid flow through the selected inlet passage; and resilient means tending to move said valve element to a position to permit maximum flow through said inlet passage, said valve element being exposed on opposite surfaces and responsive to the different pressures on the inlet and motor passage sides of said orifice to move in opposition to said resilient means.

2. A hydraulic valve comprising a casing having a valve bore with forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points; a reversing valve spool disposed for movement in said bore, said valve spool having flow directing means operative when said spool is in a predetermined position to form a flow metering orifice between selected inlet and motor passages, said orifice creating a pressure difierential on fluid flowing from the selected inlet to the selected motor passage; a valve element in said casing for controlling fluid flow through the selected inlet passage; resilient means tending to move said valve element to" a position to permit maximum flow through said inlet passage, said valve element being exposed on opposite surfaces and responsive to the different pressures on the inlet and motor passage sides of said orifice to move in opposition to said resilient means; and means for moving said valve spool to vary the size of said orifice.

3. A hydraulic valve comprising a casing having a valve bore with forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points; a reversing valve spool disposed for movement in said bore, said valve spool having flow directing means operative when said spool is in a predetermined position to form a flow metering orifice between selected inlet and motor passages, said orifice creating a pressure differential on fluid flowing from the selected inlet to the selected motor passage; a valve element in said casing for controlling fluid flow through the selected inlet passage; resilient means tending to move said valve element to a position to permit maximum flow through said inlet passage, said valve element being exposed on opposite surfaces and responsive to the different pressures on the inlet and motor passage sides of said orifice to move in opposition to said resilient means; actuating means for said valve spool to vary the size of said orifice, said actuating means having pilot fluid passages leading to the ends of the reversing valve spool bore; and a pilot valve for governing fluid flow through said pilot fluid passages.

4. A hydraulic valve comprising a casing having a valve bore with forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points; a reversing valve spool disposed for movement in said bore, said valve spool having flow directing means operative when said spool is in a predetermined position to form a flow metering orifice between selected inlet and motor passages, said orifice creating a pressure differential on fluid flowing from the selected inlet to the selected motor passage; a valve element in said casing for controlling fluid flow through the selected inlet passage; resilient means tending to move said valve element to a position to permit maximum flow through said inlet passage, said valve element being exposed on opposite surfaces and responsive to the different pressures on the inlet and motor passage sides of said orifice to move in opposition to said resilient means; actuating means for said valve spool to vary the size of said orifice, said actuating means having pilot fluid passages leading to the ends of the reversing valve spool bore; a pilot valve for governing fluid flow through said pilot fluid passages; and electroresponsive means for moving said pilot valve.

5. A hydraulic valve comprising a casing having a valve bore with forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points; a valve spool disposed for movement in said bore to alternately connect said forward and reverse motor passages with said inlet and exhaust passages, said valve spool having means operative when said spool is in position to connect selected motor and inlet passages to form a flow metering orifice between the selected passages, said orifice creating a pressure differential on fluid flowing from the inlet to the selected motor passage; fluid pressure responsive means for moving said valve spool to select the motor and inlet passages to be connected and the location of the flow metering orifice; a plurality of valve elements disposed for movement in said casing to control fluid flow through the inlet passages; and resilient means tending to move said valve elements to positions to permit maximum flow through the inlet passages, each of said valve elements being exposed on opposite iSllIfaCfiS :and :responsive to the pressures at the inlet 'andmotor passage sides of a ditferent orifice to move in opposition to said resilient means. I

-6. A hydraulic valve comprising a casing'having-a valve .bore with forward and reverse motor and inlet and exhaust passages communicating therewith, at spaced points; a valve spool disposed for movement in-said bore to connect selected sets of said passages; means in said casing tending to dispose said valve spool in position to' connect all of the passages communicating with said bore; pressure responsive means for moving said spool in-opposition to said last-named means to positions to connect selected motor and inlet passages; means operative when said spool is in a position to connect selected motor and inlet passages to form an orifice between the passages connected, said orifice creating a pressure differential an fluid flowing from the inletto the selected motor passage; valve elements disposed for movement ,in said casing to controlfluid flow through the inlet passages; and resilient means tending to .move ,said valve :elements to positions to a permit maximum. flow through said inlet passages, each of said valve elements being exposed on opposite surfaces and responsive to the pressures at the inlet and motor passagelsides Of'fllfi orifice between'the inlet passage controlled by the respective :valvc element and the motor passage connected therewith to movein' opposition to said resilient means.

7. Hydraulic apparatus comprising a source of fluid pressure; a reversible fluid motor having amovable element; control mechanism between said pressure "source and said motor, said control mechanism .having a-valve casing with a bore and forward .and reverse motor and inlet and exhaust passages communicating therewith at spaced points, said motor passages communicating with said motor and said inlet passage communicating with said pressure source; a valve spool'disposed in said bore 'for movement from a first position establishing communication between all the passages to other positions establishing communication :between :a selected motor passage and said inlet and the other motor passage and said exhaust; 'means normally'tending to maintain'said valve spool in the first position; means on said valve spool to cooperate with said casing totform an orificebetween either motor passage and the inlet passage in communication therewith, said orifice creating a pressure difierential on fluid flowing from the inlet to theselected motor passage;valve elements movably disposedin the inlet passages to control fluid flow therethrough; resilient means tending to move said valve elements to positions topermit maximum'flow'through said inlet passages, said valve elements being exposed on oppositesurfaces to the pressures on he inlet and motor. passage sides of the orifices between the inlet passages andsaid motor passages andresponsive to differences in'rsuch pressures to move inopposition totsaid resilient means; fluid pressure means for movingtsaid valve spool :firom the 'first position :to

other positions to vary the size of saidonfices, said means having a pilot valve; electro-responsive means foractuating said pilot valve, said electro-responsive means having oppositely acting solenoids; an electrical circuit for supingtsaid pilot valve,

plying operation :current to said solenoids; and means partially controlled ,by the movable element --of said ,re- 'versible fluid motor for governing the flowof current in 'saidelectrical circuit.

8; Hydraulic apparatuscomprising agsource of fluid pressure; a reversible fluid motor having a movable element; control mechanism between said pressure source andsaid motor, said control mechanism'having a valve casing with a bore and forward and reverse motor and inlet and exhaust passages communicating therewith at spaced points, said motor passages communicating with said motor and said inlet passage communicating with said pressure source; a valvespool disposed in said bore for movementfroma first position establishing communication between all the passages to other positions estal) lishing communication between aselected motor passage and said inlet and the other motorpassage and 'said exhaust; means normally tending to maintain said valve spool in the first position; means on said valve spoolto cooperate with said casing to ,form an orifice between eithermotor passage and the inlet passage in communication therewith, =said orifice creating .a pressure diflerential on fluid flowingrfrom the inlet to the selectedmotor passage; -valve elements movably disposed in the inlet passages to control fluid flow therethrough; resilient means tendingtomove said valve elements .to positionsto permit maximum flow through said inlet passages, said valve elements being exposed on opposite surfaces to thepressures on the inlet and motor passage sides ,:of the orifices between the, inlet passagesand said motor passages and responsive to diflerences in such pressures to move 1in opposition totsaid resilient meanspfluid pressure means for moving said valve spool from the fiIShPQSltiOll'jtO other. positions to vary-the. size of said ,orifiees, said means havinga pilot valve; electro-responsive means for actuatsaid electro-responsive meanshaving oppositely actingsolenoids responsive tothestrengthof current supplied thereto to determinethe direction and extent of movement of. Said 'pilot -valve;-an electrical circuit forsupplyingoperatingcurrent to said solenoids; and

means in said circuit operated ,in part by thermovable element of said fiuidmotor and in partby aselectively actuated element for varying the strength of current supplied to said solenoids.

References Cited in the file of this patent UNITED STATES PATENTS Germany May 7, 1931