US3473442A

US3473442A - Hydraulic motor drive

Info

Publication number: US3473442A
Application number: US680431A
Authority: US
Inventors: Stanley E Farmer; Thomas E Dixon
Original assignee: Cascade Corp
Current assignee: Cascade Corp
Priority date: 1967-11-03
Filing date: 1967-11-03
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21
Also published as: DE1806264A1; DE6804807U; GB1206686A; DE1806264B2

Description

Oct. 21, 1969 v 5, F M EI'AL 3,473,442

HYDRAULIC VICTOR-DRIVE Filed Nov. 5. 1967 Sfanleg E. Farmer Thomas E. Dixon INVENTORS United States Patent 3,473,442 HYDRAULIC MOTOR DRIVE Stanley E. Farmer, Gresham, and Thomas E. Dixon,

Lake Grove, Qreg, assignors to Cascade Corporation, Portland, Greg, a corporation of Oregon Filed Nov. 3, 1967, Ser. No. 680,431 int. Ci. F161: 11/02, 13/06; F16d 33/02 US. Cl. 91-412 Claims AESTRACT OF THE DISCLOSURE In a lift truck attachment having a rotatable load support, a bidirectional motor drive to be operated from a source of pressure fluid for rotating the support, such drive including a shaft geared to the support, a pair of reversible hydraulic motors drivingly connected to the shaft, and a device responsive to the pressure of fluid supplied to one of the motors to control fluid flow through both motors. The device includes a valve which, with a low pressure condition existing in fluid supplied the one motor, occupies one state where it short-circuits the other motor with substantially all fluid flow from the source then being through the one motor, and which occupies another state on a higher pressure condition existing in fluid supplied the one motor where it connects the two motors in parallel, with fluid from the source dividing between the motors.

This invention relates to a fluid-operated motor drive. A specific embodiment of the invention includes the motor drive as a means for turning a rotatable load supporting means. Thus, the invention is described herein in connection with a lift truck attachment including a rotator and a pair of load clamps (load supporting means) mounted on the rotator, where the motor drive is used to turn the rotator.

The rate at which fluid under pressure may be delivered by a source or pump in an organization such as a lift truck is limited. Accordingly, it has been found desirable to provide as the fluid-operated motor drive, for rotating the rotator, means capable of turning the rotator at a low speed while delivering high torque, and at a substantially higher speed while delivering lower torque. Such produces flexibility in operation, permitting the rapid handling of light loads without sacrificing the ability to handle much heavier loads. For handling ease it is important that the drive means adjust itself automatically to the type of load being handled, to give the performance best suited for the load. Further, where the type of performance iven by a drive means is variable, it is important that the drive means not vacillate in the type of performance it gives, and that any transition between one type of performance and another by done smoothly.

Thus, a general object of the present invention is to provide a novel hydraulic motor drive which takes the above-indicated considerations into account in a practical and satisfactory manner.

More particularly, an object is to provide a motor drive of the type indicated, which is capable of both highspeed, low-torque performance and low-speed, hightorque performance, with the type of performance determined automatically by the amount of loading occuring in a drive shaft in the drive.

According to the invention, the drive shaft is drivingly connected to a pair of hydraulic motors, and a novel pressure-sensitive device is provided which responds to the pressure of fluid supplied to one of the motors to control fliud flow through both motors. Through such regulation of the fluid flowing in the motors, the device 3,473,442 Patented Oct. 21, 1969 controls the torque and speed operating characteristics of the drive.

More specifically, with fluid supplied to the one motor at a relatively low pressure (indicating that the load on the drive shaft is relatively light), the pressure-sensitive device short-circuits the other motor, and pressure fluid from the source is circulated entirely through the one motor. The motor drive then operates at relatively high speed and low torque. When the pressure of fiuid supplied the one motor becomes relatively high (indicating that the load on the drive shaft is relatively heavy), the device removes the short circuit from the other motor, and connects the two motors in parallel, with pressure fluid from the source then flowing to both motors. The motor drive then runs at a lower speed and produces greater torque.

A further object of the invention is to provide, for a motor drive of the type contemplated, a novel changeover valve controlling the type of performance obtained from the motor drive through controlling whether one or two motors in the drive are operating. The changeover valve is responsive to fluid pressure supplied one motor, and is constructed so that a greater pressure of fluid is required in the conduit system supplying the one motor to change the operation from one where one motor operates alone, to one where both motors operate together, than is required to maintain the two motors in a state where both are operating together. With this feature of the invention, tendencies of the motor drive to alternate back and forth between operation where one motor operates alone and operation where both motors operate conjointly is inhibited.

Yet another object is to provide a motor drive as outlined which is adapted for bidirectional operation.

These and other objects and advantages attained by the invention, will become more fully apparent as the description which follows is read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified side elevation illustrating loadhandling apparatus adapted for mounting on an industrial lift truck, with such apparatus including a rotator supporting a pair of load clamps, and employing a motor drive constructed according to the invention to operate the rotator;

FIG. 2 is a schematic diagram, partly in block form, further illustrating the motor drive of FIG. 1 (with the drive removed from the rotator in FIG. 1), and illustrating connections between the drive and a source of pressure fluid; and

FIG. 3 is an enlarged view illustrating details of a pressure-sensitive device employed in the motor drive of FIGS. 1 and '2.

Turning now to the drawings and referring first to FIG. 1, indicated generally at 10 is load-handling apparatus, including a rotator 12 and a load-clamping mechanism, or load support, 14 adapted to be mounted on the front of an industrial lift truck. The rotator includes an upright flat base plate 16 which may be mounted on the usual elevatable carriage (not shown) in a lift truck through a mounting plate 18 (suitably fastened to the carriage) and

brackets

20, 22 secured to the back of plate 16. The rotator further includes an upright, rotatable face plate 24- disposed in front of and substantially parallel with plate 16. Plate 24 is rotatably mounted on plate 16 through a conventional bearing assembly including an outer race partially shown at 26a fastened to the front of plate 16, and a relatively rotatable inner race, partially shown at 26b, secured to the back of plate 24. The axis of rotation of plate 24, shown at 28, extends in a direction normal to the planes of plates 16, 24.

Clamping mechanism 14 includes a pair of opposed, relatively movable, power-operated clamping

arms

30, 32 having clamping pads 30a, 32a, respectively, mounted on their forward extremities. The arms are mounted for movement toward and away from one another on a frame 34, and through this frame the mechanism is suitably anchored to the front of plate 24 in the rotator. With movement of the arms toward one another, the clamping pads are adapted to clamp against opposite sides of a cylindrical load, such as a paper roll. For a more detailed description of a load clamping mechanism similar to that shown herein reference is made to a copending application of Donald M. Faust and Henry F. Chochrek, entitled Clamping Mechanism, filed June 9, 1967, Ser. No. 645,027.

Plate 24 in the rotator is rotated under power by means of a hydraulic motor drive generally indicated at 36 (see FIGS. 1 and 2). The motor drive includes a pair of conventional reversible hydraulic motors 38, 40 with their casings suitably mounted on the casing of a drive unit 42, the latter being anchored to the back of plate 1'6. Motors 38, 40 are similar in construction, and include corresponding ports 38a, 38b and 40a, 4012 (represented in block form), respectively, which accommodate the flow of pressure fluid through the motors. With pressure fluid introduced into ports 38a, 40a (or into

ports

38b, 40b), the motors operate in the same direction. The motors are drivingly connected to opposite ends of a drive shaft 44 which extends between the motors, and through the housing in unit 42.

Shaft 44 is connected to a worm screw 46 in unit 42 which drives a worm gear 48 in the unit. A driving connection is established between gear 48 and plate 24 in the rotator by means of a shaft 50 which is turned by the gear, and suitable gears (not shown) connecting the shaft to the plate.

Further describing motor drive 36, and referring to FIG. 2, the motor drive includes a pressure-sensitive device (shown in block form at 52) having

ports

52a, 52b, 52c, 52d. Constructional details of device 52 will be considered more fully in a later discussion. Device 52 is connected to motor 38 through pair of

conduits

54, 56, and to motor 40 through pairs of

conduits

58, 60 and 62, 64. More specifically,

conduits

54, 56 have one set of ends connected to ports 38a, 38b, respectively, and an opposite set of ends connected to

ports

52a, 52b, respectively.

Conduits

58, 60 have one set of ends connected to ports 52c, 52d, respectively, and an opposite set of ends connected to

conduits

62, 64 respectively.

Conduits

62, 64, in turn, have one set of ends connected to motor ports 40a, 40b, respectively.

Hydraulic fluid under pressure for operating motors 38, 40 is furnished from a source generally indicated at '66 including a reservoir 68, a pump 70, a pressure relief valve 72, and a main control valve 74. These may be conventional pieces of equipment found on the usual lift truck. Pump 70 is connected to the reservoir by a conduit 76 and to valve 74 by a conduit 78. Valve 74 is connected directly to the reservoir by a conduit 80. Pressure relief valve 72 is connected to conduit 78 by a conduit 82, and to conduit 80' by a conduit 84. Valve 74 is connected as shown to the other set of ends of previously-mentioned

conduits

62, 64.

In FIG. 2, the valve spool of valve 74 is illustrated as a rectangle divided into three squares, with each square containing symbols illustrating how fluid flow takes place through the valve for various positions of the spool. The spool is normally biased to the neutral position in which it is shown by means of

springs

86, 88 acting on its opposite ends, and the spool may be adjusted to different positions through the operation of manual adjustment means 90, 92. With the valve spool in its neutral position,

conduits

62, 64 are closed off where they are connected to the valve, and

conduits

78, 80 communicate with one another through the valve. With the valve spool shifted downwardly from its neutral position in FIG. 2, pressure fluid is admitted to conduit 62 and exhausted from conduit 64. On the other hand, with the spool shifted upwardly from its neutral position in FIG. 2. pressure fluid is admitted to conduit 64 and exhausted from conduit 62.

Turning now to FIG. 3, and describing in detail the construction of pressure-sensitive device 52, the device includes a body 94. Extending completely through the body, from one side to the other in FIG. 3, is an elongated cylindrical passage including a central section 96 having one diameter, and a pair of end sections 98, which are similar to one another and which have somewhat larger diameters than the central section. Where section 98 joins with section 96 there is an annular shoulder 98a facing to the left in FIG. 3. A similar shoulder 100a exists, facing to the right in the figure. where section 100 joins section 96. The outer ends of passage section 98, 100 are closed off by plugs 102, 104, respectively, which are screwed into the sections.

Communicating with passage section 96 at points spaced along its length, and on diametrically opposite sides of the section, are pairs of

bores

106, 108 and 110. 112 which icommunicate with previously-mentioned

ports

52a, 52b, and 52c, 52d, respectively. Bores 106, 108 are somewhat more closely spaced together than are bores 110, 112.

Extending into body 94 from the lower side thereof in FIG. 3, and communicating with passage sections 98, 100, are pairs of axially aligned

bores

114, 116, and 118, 120, respectively. Bores 114, 118, have somewhat larger inside diameters than do bores 116, 120. The lower ends of bores 114, 118 are closed oif by

plugs

122, 124, respectively. The upper ends of bores 114, 118 communicate through

passages

126, 128 with bores 110, 112, respectively.

Extending into the left and right sides of body 94 in FIG. 3, and intersecting bores 116, at substantially right angles, are

bores

130, 132, respectively. The outer ends of

bores

130, 132 are closed off by

plugs

134, 136. respectively, and the inner ends of the bores communicate with bores 110, 112 through bores 138, respectively. The cross-sectional areas of bores 138, 140 are substantially the same, and are considerably smaller than those of

bores

130, 132.

Slidably mounted in passage section 96 is an elongated valve spool or member 142 having a length substantially the same as that of passage section 96. Extending about the outside of the spool, substantially midway between its opposite ends is an annular channel 144. Extending axially and inwardly from the right end of the spool in FIG. 3 is an elongated cylindrical passage 146. The left end of passage 146 communicates with a passage 148 (having a substantially smaller inside diameter than that of passage 146) and this passage in turn opens onto the left end of the spool in FIG. 3.

The spool is illustrated in a centered position relative to the opposite ends of passage section 96, and in this position it closes off the upper ends of bores 110, 112 while permitting the lower ends of bores 106, 108 to communicate with one another through channel 144, The spool is urged to this position by means of

pilots

150, 152 slidably received in passage sections 98, 100, respectively, and a pair of similar springs 154, 156 which act between plugs 102, 104 and

pilots

150, 152, respectively. The pilots are similar in construction, and considering pilot 150, it includes an elongated cylindrical part a having an axially extending passage 15012. The pilot further includes an annular flange 150a projecting radially outwardly from part 150a. In FIG. 3, the flange in pilot 150 seats against shoulder 98a, and against the left end of spool 142; The flange in pilot 152, similarly, seats against shoulder 100a and the right end of the spool.

According to the invention, with shifting of the spool to the right in FIG. 3, the connection between bores 106.

108 is broken, bore 110 communicates directly through passage section 96 with bore 106, and bore 112 communicates through channel 144 with bore 108. Similarly, with shifting of the spool to the left, the connection between bores 106, 108 is broken, and these bores communicate with bores 110, 112, respectively.

Blocking communication between bores 114, 116 is a ball 158. The ball is biased to the position shown, seated against the shoulder existing where bores 114, 116 join, by means of a spring 160 acting between the ball and plug 122. A similar ball and

spring

162, 164, respectively, are provided in bore 118 blocking communication between bores 118, 120. Normally closing off bore 138 where it joins with bore 130 is a ball 166. Ball 166 is biased to the position shown by a spring 168 which acts between the ball and plug 134. In a similar fashion, a ball 170 biased by a spring 172 acting between the ball and plug 136 blocks communication between

bores

132, 140.

Springs

168, 172 are substantially the same in construction.

Considering briefly the operation of device 52, spool 142 and the associated parts controlled by the spool constitute a change-over valve in the device. With pressure fluid supplied to conduit 58, such fluid is introduced through port 520 into bores 110, 138, where it acts upon ball 166. So long as the pressure of this fluid remains below a certain pressure, the ball remains in the position shown in FIG. 3. Spool 142 will remain centered in passage section 96, with the upper ends of bores 110, 112 closed olf, and the lower ends of bores 106, 108 communicating with one another through channel 144.

Some leakage of fluid may occur around the left end of the valve spool, and any fluid which leaks from bore 110 to the region adjacent the left end of the spool flows through passages 148, 146 to passage section 100 and bore 120. When the pressure of fluid in bore 120 is suflicient to shift ball 162 downwardly against spring 164, such fluid exhausts to conduit 60 through passage 128 and bore 112.

Upon the fluid pressure in bores 110, 138 exceeding a certain pressure, ball 166 shifts to open the left end of bore 138, and fluid flows through

bores

130, 116, passage section 98 and passage 1501) to the left end of spool 142. The spool shifts to the right in FIG. 3 against pilot 152 and spring 156. Thereupon bore 110 communicates with bore 106, and bore 112 communicates with bore 108. The direct connection between the lower ends of bores 106, 108 is broken. In addition, the left end of the spool (referred to as a piston face region) moves to a position where it is directly exposed to fluid in bore 110.

Upon shifting of the spool to the right as just explained, fluid contained in passage 146, passage section 100, and bore 120 acts upon ball 162 to lower it in bore 118, whereupon such fluid exhausts through passage 128 and bore 112. Thereafter, and with the spool continuing to occupy a position shifted to the right, a relatively small amount of fluid acting on the left end of the spool leaks through passages 148, 146 and is exhausted in the same manner.

With the spool 142 shifted to the right in the control device and the left end of the spool exposed to the fluid under pressure in bore 110, a substantial surface area in the spool is acted upon by such pressure fluid to produce a substantial force tending to hold the spool in its rightof-center position. Spring 156 resisting such movement and spring 168 resisting movement of ball 166 to open bore 138 are selected so that a substantially greater pressure of fluid is required in bore 110 to open bore 138 and initiate travel of the spool than is required to maintain the spool in its right-of-center position. Ball 166 therefore functions as and is referred to herein as a starter valve means located in a passage extending from bore 110 and communicating with the left end of the valve spool (or a piston face region in the spool) with this left end nonexposed directly to fluid under pressure in bore 110.

With motor 38 and motor 40 connected in parallel, and being supplied from the source, as occurs with such shifting of the valve spool, a substantial drop in pressure is required in conduit 58 before th control device will operate to remove motor 38 from the source. This is because a lower pressure is required to maintain the valve spool in its adjusted position than is required initially to start movement of the valve spool from its neutral position. Accordingly vacillation in the operation of the drive is minimized.

A similar operation takes place in device 52 with pressure fluid furnished to conduit 60 rather than to conduit 58. In this case, upon the pressure of fluid in bores 112, 14-0 exceeding a certain level, spool 142 shifts from its neutral or centered position to the left in FIG, 3. As in the first case described above, such shifting of the spool results in a breaking of the direct connection between bores 106, 108, and in connecting bores 110, 106 and bores 112, 108.

Explaining now how the motor drive operates, valve 74 may be adjusted to admit pressure fluid to conduits 62, 58 (with fluid permitted to exhaust from conduits 64, 60) to produce operation of the motor drive in one direction. Assuming that the load demand exerted on shaft 44 (resulting from the action of a load held between the clamping pads) is relatively light, the pressure of fluid in conduits 62, 58 (and hence the pressure of fluid acting on ball 166 in device 52), will be relatively low. Spool 142 remains in its neutral position blocking bores 110, 112 and thus stopping circulation of fluid between source 66 and motor 38. All pressure fluid coming from the source as a consequence circulates through motor 40, and motor 40 operates to drive shaft 44 at relatively high speed.

With turning of shaft 44, and because the shaft is common to both motors, motor 38 operates as a pump, and circulates fluid in

conduits

54, 56 which have been short-circuited by the valve spool. It will be noted that the body of fluid circulating in the closed system produced by such short circuit is isolated from the pump and reservoir.

Should the load demand on shaft 44 increase, this results in an increase in the pressure of fluid in

conduits

62, 58. Upon the pressure of such fluid exceeding a certain level, ball 166 in device 52 shifts to admit pressure fluid against the left end of spool 142 in FIG. 3. The spool then shifts to the right to remove the short circuit across motor 38, and to connect

conduits

54, 58 and

conduits

56, 60. When this occurs, pressure fluid in conduit 58 flows through the device to motor 38, and fluid exhausts from the motor through the device to conduit 60. Accordingly, fluid flowing from source 66 divides between motors 38, 40 with the motors together driving shaft 44. The drive then delivers higher torque at a slower speed.

To reverse the rotational direction of the motors, valve 74 is adjusted to admit pressure fluid to

conduits

64, 60. With such an adjustment made, the operation of motor drive 36 is similar to the operation just described. In this case, however, it is the pressure of fluid in

conduits

64, 60 which determines whether one or both of the motors drives shaft 44-.

Thus, the invention provides a novel hydraulic motor drive for driving a rotating shaft, where power is transmitted to the shaft at a torque and with a rotational speed which depends upon the loading of the shaft. The drive employes a pair of motors with one of such motors being short-circuited to produce high-speed, lowtorque characteristics.

While an embodiment of the invention has been described herein, it is appreciated that variations and modifications may be made without departing from the spirit of the invention. Accordingly, it is desired to cover all such variations and modifications which would be apparent to those skilled in the art, and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A motor drive to be operated from a source of fluid under pressure comprising a shaft and a pair of hydraulic motors drivingly connected to the shaft,

a conduit system interconnecting said source and said motors for circulating fluid between each of said motors and said source, and including a pair of conduits for each motor for supplying fluid to and exhausting it from the motor,

said conduit system further comprising a pressure sensitive device including fluid-pressure-operated valve means interposed between said pair of conduits for one motor responsive to the pressure of fluid supplied to the other motor operable, with a low pressure condition existing in fluid supplied said other motor, to establish a short circuit between the pair of conduits for said one motor producing an isolated body of fluid for circulation through said one motor, said valve means with a higher pressure condition existing in fluid supplied said other motor operating automatically to remove said short circuit and to connect said one motor through the pair of conduits provided therefor to said source for the circulation of fluid between the source and the one motor.

2. The motor drive of claim 1, wherein said valve means includes a shiftable valve member biased to a position establishing said short circuit, and held against such biasing, and with the fluid supplied said other motor at a pre-established pressure, in another position connecting said one motor through the pair of conduits provided therefor to said source for the circulation of fluid between the source and the one motor.

3. The motor drive of claim 2, wherein said valve means is constructed so that with its valve member in its firstmentioned position a pressure of fluid supplied said other motor exceeding said pre-established pressure is required to shift the valve member to its said other position.

4. The motor drive of claim 3, wherein the valve member includes a piston face region which communicates with pressure fluid circulating between the source of said other motor with the valve member in its said other position thus to be acted upon by such fluid, said face region occupying a noncommunicating position with respect to such pressure fluid with the valve member in its said first-mentioned position.

5. The motor drive of claim 4 which further includes a fluid passage communicating with said face region of said valve member with said valve member in its first-mentioned position and connected also to the pair of conduits for said other motor to reflect the pressure of fluid supplied to the other motor, and starter valve means is provided for said passage inhibiting flow through the passage of fluid circulated in said pair of conduits for said other motor until the pressure of fluid supplied to the other motor exceeds said pre-established pressure.

6. The motor drive of claim 2, wherein said motors are bidirectional, and said valve member is shiftable from its first-mentioned position to two other positions, one of said other positions connecting said one motor through the pair of conduits provided therefor to said source for the circulation of fluid producing rotation of the one motor in one direction, and the other of said other positions connecting the one motor to said source for the circulation of fluid producing rotation of the one motor in the reverse direction.

7. In a lift truck attachment including a rotatable load support, a bidirectional motor drive to be operated from a source of fluid under pressure for rotating the support comprising a shaft and a pair of nected to the shaft,

a conduit system interconnecting said source and said motors for circulating fluid between each of said motors and said source, and including a pair of conduits for each motor for supplying fluid to and exhausting hydraulic motors drivingly conit from the motor,

said conduit system further comprising a pressure-sensitive device including fluid-pressure-operated valve means interposed between said pair of conduits for one motor responsive to the pressure of fluid supplied to the other motor,

said valve means being operable, with a low pressure condition existing in fluid supplied the other motor, to short-circuit the pair of conduits for said one motor to produce an isolated body of fluid for circulation through said one motor,

said valve means being further operable automatically,

with a higher pressure condition existing in fluid supplied said other motor, to remove said short circut, and to connect said one motor through the pair of conduits provided therefor to said source for the circulation of fluid between the source and the one motor.

8. A motor drive to be operated from a source of fluid under pressure comprising a shaft and a pair of hydraulic motors drivingly connected to the shaft,

a conduit system interconnecting said motors and said source for circulating fluid between the source and the motors, and including a pair of conduits for each motor for supplying fluid to and exhausting it from the motor,

said conduit system further comprising a pressure-sensitive device including fluid-pressure-operated valve means interposed between said pair of conduits for one motor, and responsive to the pressure of fluid supplied the other motor for alternatively connecting and disconnecting the one motor and said source depending on the level of such pressure,

said valve means, with the one motor and source disconnected, connecting the same for the circulation of fluid therebetween on the pressure of fluid supplied to said other motor exceeding one pressure, and with the one motor and source connected, disconnecting the same on the pressure of fluid supplied to said other motor dropping below another pressure which is lower than said one pressure.

9. The motor drive of claim 8, wherein said valve means includes a movable valve member which occupies one position with said source and said one motor disconnected and another position with said source and said one motor connected, said valve member including a piston face region which communicates with pressure fluid circulating between the source and the other motor with the valve member in its said other position thus to be acted upon by such fluid, said face region occupying a noncommunicating position with respect to such pressure fluid with the valve member in its said one position.

10. The motor drive of claim 9 which further includes a fluid passage communicating with said piston face region of said valve member with said valve member in its said one position and connected also to the pair of conduits for said other motor to reflect the pressure of fluid supplied the other motor, and starter valve means is provided for said passage inhibiting flow through the passage of fluid circulated in said pair of conduits for said other motor until the pressure of fluid supplied the other motor exceeds said one pressure.

References Cited UNITED STATES PATENTS 2,370,526 2/1945 Doran. 2,374,588 4/1945 Doran. 2,500,627 3/1950 Chinn 6053 2,616,259 11/1952 Quintilian 60-53 EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R.