US2878015A - Hydraulic control mechanisms - Google Patents

Hydraulic control mechanisms Download PDF

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US2878015A
US2878015A US661114A US66111457A US2878015A US 2878015 A US2878015 A US 2878015A US 661114 A US661114 A US 661114A US 66111457 A US66111457 A US 66111457A US 2878015 A US2878015 A US 2878015A
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motor
fluid
piston
cylinder
hydraulic
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US661114A
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Hugo A Panissidi
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International Business Machines Corp
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International Business Machines Corp
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/08Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H61/00Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38Control of exclusively fluid gearing
    • F16H61/40Control of exclusively fluid gearing hydrostatic
    • F16H61/46Automatic regulation in accordance with output requirements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/20Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205Systems with pumps
    • F15B2211/2053Type of pump
    • F15B2211/20538Type of pump constant capacity
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/20Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/21Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/212Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/3052Shuttle valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/30525Directional control valves, e.g. 4/3-directional control valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/315Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/31552Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line
    • F15B2211/31558Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line having a single output member
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/32Directional control characterised by the type of actuation
    • F15B2211/321Directional control characterised by the type of actuation mechanically
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/35Directional control combined with flow control
    • F15B2211/353Flow control by regulating means in return line, i.e. meter-out control
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/40Flow control
    • F15B2211/405Flow control characterised by the type of flow control means or valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/40Flow control
    • F15B2211/415Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41554Flow control characterised by the connections of the flow control means in the circuit being connected to a return line and a directional control valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/40Flow control
    • F15B2211/42Flow control characterised by the type of actuation
    • F15B2211/428Flow control characterised by the type of actuation actuated by fluid pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/40Flow control
    • F15B2211/46Control of flow in the return line, i.e. meter-out control
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058Rotary output members
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/75Control of speed of the output member

Definitions

  • HYDRAULIC CONTROL MECHANISMS Filed May 23, 1957 5 Sheets-Sheet 3 REST v" DEQELERITE 0Q, ACCELERATION AND DECELERATION OF HYDRAULIC MOTOR 22 S CONTROL VALVE CAM so 99 AND 99 KNOCK OFF CAM 94 f 102 AND 102 DETENT CAM 95 INVENTOR.
  • This invention relates to hydraulic apparatus wherein there is a requirement to selectively control and regulate the extent of actuation of a hydraulic motor.
  • Hydraulic systems have been devised to control and regulate the extent of actuation of a hydraulic motor but the present invention is directed to the provision of means to adjust its extent of actuation, whereby the work accomplished by the hydraulic motor may be used for a variety of purposes.
  • the invention contemplates the control of a hydraulic motor, i. e. its starting and stopping, by opening or closing its fluid exit, to provide a metering cylinder which receives a predetermined volume of exhaust fluid proportional to the extent of actuation of the hydraulic motor, and to selectively adjust and change the volume of the exhaust fluid to vary the extent of actuation of the hydraulic motor.
  • the invention contemplates the provision of an exhaust fluid receiving metering cylinder which has an adjustable volume receiving capacity.
  • a metering cylinder in which a variable extent of movement of a piston in a cylinder receiving exhaust fluid controls the extent of actuation of the hydraulic motor.
  • said cylinder is completely closed with the exception of two fluid directing ducts and in said cylinder is a freely floating piston.
  • the fluid In one cyclic operation of the motor the fluid is directed from one duct against the piston which then floats along in the cylinder.
  • the latter At the end position of the piston the latter abuts an adjustable stop at which time the cylinder is filled and no more fluid can be received by the cylinder, and the motor stops.
  • a reverse operation takes place, but in each operation one of the ducts is open to the return duct to permit emptying of the exhaust fluid to provide an increasing volume of the cylinder to receive the fluid exhausted in the same operation.
  • the adjustable stops at the ends of the cylinders provide for the initial volume adjustment of the cylinder which is proportional to the volume of fluid discharge and the extent of motor actuation.
  • a still further object of the invention is to provide means to reduce the eflective area of the piston subjected to fluid pressure at both the start and finish of the rotation of the motor, whereby the acceleration and deceleration of the hydraulic motor is eflected gradually. This subjects the starting and stopping of the motor to less shock and provides a desirable type of rotation for many purposes.
  • Fig. 1 is a diagrammatic representation of the components of the apparatus and their inter-connection and the paper feeding device operated thereby to intermittently feed the paper web predetermined amounts.
  • Fig. 2 is a perspective view of some of the apparatus shown in Fig. 1. 1
  • Fig. 3 is a timing diagram.
  • Constant fluid pressure source The hydraulic motor to be described, which is operated herein to intermittently feed a paper strip a predetermined distance, is actuated by fluid at a constant pressure level derived from a hydraulic pump 10 preferably of the gear type.
  • the hydraulic gear pump 10 (Fig. 1) is continuously driven by an electric motor. 11.
  • a duct 12 is connected to the suction side of the gear pump 10 to draw fluid from a reservoir 13, said duct 12 having connected I at its end a foot valve 14 dipping in the reservoir 13.
  • the duct 15 is connected at one side to the pressure side of the gear pump 10 and at theother side to a filter 16 which in turn is connected to apressure regulator valve 17 having an overflow pipe 18, dipping inthe reservoir 13.
  • the Out side of pressure regulator 17 is connected to an accumulator 19 which serves'to keep the pressure at a constant predetermined level, said fluid then being directed through a check valve 20 to a duct 21.
  • the hydraulic motor 22 is of the fluid actuated type and the duct 21 is connected to the inlet side 23 of the hydraulic motor, whereby the pressureof the fluid in the duct 21 rotates said motor as long as the fluid output port 24 is unblocked to permit free exit of the exhaust fluid at a lower pressure through a duct 25.
  • Paper feeding mechanism The speed control for the hydraulic motor 22 is adapted herein to regulate and determine the extent of paper feed and to effect the feed in an intermittent manner.
  • the driven shaft 29 of thehydraulic'motor 22' has connected to it a gear 30 which drives through an idler change gear 31 a gear 32 connected to the feed roll shaft 33.
  • gears 35 a parallel feed roller shaft 34 is driven in order to oppositely drive a pair of feed rolls 36 between which a paper strip 37 passes.
  • Said strip is drawn from a roll (not shown), and has associated therewith a tension or slack roller 38. The paper strip is thus fed in the direction of the arrow shown in Fig. 2.
  • Machines of this type are provided wtih several pairs of" Shuttle or control valve
  • the closing or opening of the output side of the hydraulic motor 22 at output port 24 is controlled by a con-' trol valve 40 which is actuated in a 'manner'designed to produce the desired rotational characteristics to the hy-- draulic motor 22.
  • Said control valve comprises a block 41 suitably bored to provide a cylinder and associated ports and ducts.
  • the shuttle valve comprises a cylindrical bore in which fits-a" spool type valve.
  • the output port'25 ofhydraulic motor 22 is connected to the central input port 43 and is adapted; to be completely closed by a central piston to stopthc rotation of the hydraulic motor 22.
  • piston 44 In the position shown in Fig. 1 especially piston 44 has opened the input port 43 to a chamber 45, thus enabling fluid flow in the direction of the arrow to a duct 46 connected to chamber 45.
  • a lowered position (Fig. 2) of said piston 44 or righthand in Fig. l fluid communication is made between in put port 43 and a chamber 47 which has a connection to a duct 48.
  • piston 44 alternately directs the fluid output in duct 25 to either chambers 45 and 47 and related ducts 46 and 48, for a reason soon to be evident.
  • Said shuttle valve carries upper and lower end pistons 50 and 51 adapted to close or open chambers 53 or 54 which have fluid communication on one side to the respective ducts 46 and 48 and on the other side to related ducts 55, 56 which returns fluid back by a return duct 57 to the reservoir 13 (see Fig. 1).
  • the movements of the shuttle valve to elfect the desired rotational characteristics of the hydraulic motor 22 are controlled by a profile cam 60 against which bears the piston 50, and a spring 58 causes said piston assembly to follow the profile of the cam 60 as the latter is rotated.
  • Metering valve Associated with the control or shuttle valve is a metering valve which adjustably limits or meters the volume of fluid discharge from the exit port 24 of the hydraulic motor 22.
  • a closed cylinder 61 in which a freely floating piston 62 moves in one direction or the other according to whether fluid emerges from duct 46 or duct 48.
  • piston 62 is in such position that fluid emerging from either ducts 46 or 48 will strike one face or the other of the floating piston 62 shifting it in the cylinder in a related direction until it reaches its limit position at which time the cylinder is filled with fluid and stops the motor.
  • the available volume in the cylinder is determined by adjustable stops 63 and 64, and since they regulate the extent of movement of the floating piston 62, the volume of the cylinder is regulated. Further, the volume of fluid discharge is regulated to control the extent of rotation of the hydraulic motor, and the extent of paper feed.
  • stop plugs 70 and 71 are fitted and each consists of a cylindrical plug having channeled end rings carrying conventional piston rings 72.
  • the plug is reduced in diameter in the mid-portion at 73 to form an annular chamber 74 communicating with the bore 46 or 48' in the cylinder 61 to which ducts 46 or 48 are connected.
  • a central hole or orifice 75 in each stop plug is intersected by a hole 76 which opens to the chamber 74, formed by the reduced diameter mid-portion 73.
  • each plug 70, 71 is movable more or less into the cylinder by forming stops 63 and 64 as conventional adjusting screws which are attached to plugs 70 and 71 and are locked into position by lock nuts 79.
  • the motor would be rapidly accelerated which is not desirable.
  • the .efiective area of the piston 62 at the instant of starting is the reduced area exposed by the orifice 75 of the elfective stop plug to the tapered pin 77.
  • This reduced effective area at the instant of start decreases the rate of acceleration of the hydraulic motor in its angular excursion or rotation from zero to maximum velocity.
  • the other tapered pin 77 of the floating piston 62 moving in the cylinder 61 approaches the orifice 75 of the other stop plug the escaping fluid will be gradually restricted, thus, gradually decelerating the floating piston 62- a stop, and accordingly the hydraulic motor.
  • Cyclic operations It is desirable to eflect cyclic operations of paper feed by initiating the rotation of the hydraulic motor at desired times. A convenient way of accomplishing this is described as follows:
  • a motor 80 drives a shaft 81 through a belt drive 82 and interposed between shaft 81 and the shaft 83 carrying the cam 60 is an electromagnetically controlled clutch 84 of conventional construction.
  • One element of the clutch is constantly rotated by shaft 81 and the other element of the clutch which is attached to shaft 83 is clutched thereto when a clutch release arm 85 is rocked as a result of the energization of a control magnet 86.
  • No electrical circuit for energizing the clutch control magnet 86 is shown herein since it is evident that various means may be provided to complete the energizing circuit to energize the magnet 86.
  • the cam 60 is so designed that in one half revolution of shaft 83 during one cyclic operation it will move the piston 44 upwardly from the neutral position and back to neutral to cause duct 46 to receive the fluid discharge, and in a successive half revolution of shaft 83 during the next cyclic operation the piston 44 is moved downward from neutral position and back thereto to cause duct 48 to receive the fluid discharge.
  • the clutch 84 permit only half revolutions of the shaft 83 and other shafts during successive cyclic operations.
  • a gear 90 which drives a gear 91 secured to a counter shaft 92, through an idler gear 93.
  • Counter shaft 92 carries profile earns 94 and 95.
  • the profile cams 94 and 95 are adapted to receive a half revolution for each cyclic operation.
  • Pivoted on a stud 96 is a detent in the form of a bell crank, the rearward sharpened detent arm 97 being adapted to engage a ratchet detent wheel 98 secured to the hydraulic motor drive shaft 29. At the stopped position of the motor, detent arm 97 engages a tooth of the ratchet wheel 98.
  • cam 94 begins to turn in the arrow direction to cause a lobe 99 of the cam 94 bearing against a wheel 100 carried by a follower arm 101 integral with detent arm 97 to rock the detent arm 97 free of the ratchet wheel 98, permitting the hydraulic motor to rotate.
  • Sheet severingmechanism While the present apparatus so far described constitutes a useful entity in a paper web feeding apparatus, it may be desirable to sever the predetermined lengths of paper fed into separate sheets.
  • paper web is fed between a fixed cutting blade 110, and a reciprocable guillotine blade 111.
  • a motor 112 drives a shaft 113 by a belt drive 114.
  • a second electromagnetic clutch 115 controlled by a solenoid 116 clutches shaft 113 with an eccentric cam 117.
  • the eccentric cam moves the guillotine blade 111 against the companion blade 110 to sever the paper web, forming a sheet of a predetermined length, which drops in a storage magazine 118.
  • gears 30, 31 and 32 may be a conventional adjustable change gear mechanism in a change gear box 119 (Fig. 1).
  • a hydraulic motor whose rotation is started and stopped by respectively opening or closing the fluid discharge exit port of said motor, a control valve having its entrance port connected to said exit discharge port, said control valve having a discharge port, and a piston in said valve normally closing said fluid exit discharge port of said motor to stop said motor, means for positioning said piston to open said fluid exit discharge port to start said motor and discharge the exhaust fluid to the discharge port of said control valve, a metering valve having an entrance port receiving the discharged fluid from the discharge port of said control valve, a piston freely floating in the cylinder of the metering valve against which the discharged fluid impinges to move the piston in the cylinder, and means adjustable by the operator of the machine for limiting the extent of movement of the piston in the cylinder, whereby the volume of discharged fluid and the stopping of the motor is governed by the extent of move ment of the piston.
  • a hydraulic motor whose rotation is started and stopped by respectively opening or closing the fluid discharge exit port of said motor, a control valve having its entrance port connected to the fluid discharge port and having a pair of discharge ports, a piston in said valve for closing the discharge exit port to stop said motor and for opening said discharge exit port to rotate said motor and directing the discharged fluid to either of two discharge ports of said control valve, means for operating said piston to open the discharge exit port to rotate said motor and to effect discharge of the fluid to one and then the other of said two discharge ports of the control valve in successive startstop cyclic operations of said hydraulic motor, a metering valve having a piston floating in a closed cylinder and a pair of entrance ports connected to the respective one of the two discharge exit ports of the control valve, which entrance ports open in the cylinder in such a way as to impinge the fluid discharge against the piston to move it in the cylinder in one direction and then the other in successive cyclic operations, and means to limit the movement of the piston in each of the two directions it moves
  • a hydraulic apparatus defined in claim 2 wherein the piston of said metering valve carries a tapered stud, and the discharged fluid from an entrance port is discharged into an orifice normally blocked by said tapered stud whereby the area of the piston impinged by the discharged fluid is initially restricted and a gradual acceleration of rotation of the motor is eflected at the start as the piston moves said stud out of the orifice.
  • a hydraulic apparatus defined in claim 4 wherein as said piston moves in the metering valve the fluid previously discharged in the cylinder is emptied through an orifice of an entrance port, and the piston of said metering valve carries a pair of tapered studs, one of which studs fits in the orifice of the entrance port receiving the discharged fluid to reduce the effective area of the piston impinged by the discharged fluid and gradually increases the area as said piston is moved in the cylinder to effect a gradual acceleration of the motor at the start, and the other stud is received by said first orifice to gradually close said first orifice to decrease the rate of discharge of the emptied fluid, to thereby effect a gradual deceleration of the motor to a stop.
  • a hydraulically driven paper feeding apparatus the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, the starting and stopping of said motor being effected by respectively opening and closing an exit fluid discharge port, a control valve having a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston for opening said fluid discharge port during a predetermined period to cause the motor to rotate during said predetermined period, a metering valve having a cylinder receiving the fluid discharge from the control valve to cause the rotation of the motor and feed of the paper strip until the cylinder is filled, and means for decreasing the volume of the cylinder of said metering valve to effect rotation of the motor less than said predetermined period, and thereby predetermine the extent of paper feed.
  • a hydraulically driven paper feeding apparatus the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, a detent engaging a ratchet wheel attached to the driven shaft of said motor to lock said motor against rotation, the starting and stopping of said motor being effected by respectively opening and closing an exit fluid discharge port and the disengage ment of said detent from said ratchet wheel a control valve having a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston for opening said fluid discharge port during a predetermined period to cause the motor to rotate during said predeter mined period, cam operated means operable synchronously with said cam for disengaging the detent from said ratchet wheel when said control valve opens said fluid discharge port, a metering valve having a cylinder receiving the fluid discharge from the control valve to cause the rotation of the motor and feed of the paper strip until the cylinder is filled, said cam operated means causing the men detent to engage said ratchet wheel to
  • a hydraulically driven paper feeding apparatus the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, said motor having an exit fluid discharge port which is respectively closed and open to stop and start said motor, a control valve having an entrance port connected to the discharge port and a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston to first open said fluid discharge port to start the motor and then close said fluid discharge port to stop the motor, ametering valve comprising-a cylinder, a floating piston movable therein to a limited extent to predetermine the volume of the discharged fluid and having an entrance port receiving the fluid discharge from the control valve and opening in the cylinder of the metering valve to cause the fluid discharge to impinge upon the piston to permit rotation of the motor and feed of the paper strip until the cylinder is filled, and means for governing the extent of movement of the piston in the cylinder to vary the volume of the cylinder of the metering valve, the extent of rotation of the motor,

Description

March 17, 1959 H. A. PANlSSlDl HYDRAULIC CONTROL MECHANISMS s Sheets-Sheet 1 Filed May 25, 1957 GEAR BOX 3 ,32, CHANGE INVENTOR. HUGO A. PANISSIDI ATTORNEY H. A. PANISSIDI HYDRAULIC CONTROL MECHANISMS March 17, 1959 5 Sheets-Sheet 2 Filed May 23, 1957 INVENTOR.
ATTORNEY March 17, 1959 H. A. PANISSIDI 2,878,015
HYDRAULIC CONTROL MECHANISMS Filed May 23, 1957 5 Sheets-Sheet 3 REST v" DEQELERITE 0Q, ACCELERATION AND DECELERATION OF HYDRAULIC MOTOR 22 S CONTROL VALVE CAM so 99 AND 99 KNOCK OFF CAM 94 f 102 AND 102 DETENT CAM 95 INVENTOR.
HUGO A.PANISSD1 ATTORNEY 2,878,015 HYDRAULIC CGNTROL MECHANISMS Application May 23, 1957, Serial No. 661,114 9 Claims. (Cl. 2712.4)
' This invention relates to hydraulic apparatus wherein there is a requirement to selectively control and regulate the extent of actuation of a hydraulic motor. Hydraulic systems have been devised to control and regulate the extent of actuation of a hydraulic motor but the present invention is directed to the provision of means to adjust its extent of actuation, whereby the work accomplished by the hydraulic motor may be used for a variety of purposes. More specifically the invention contemplates the control of a hydraulic motor, i. e. its starting and stopping, by opening or closing its fluid exit, to provide a metering cylinder which receives a predetermined volume of exhaust fluid proportional to the extent of actuation of the hydraulic motor, and to selectively adjust and change the volume of the exhaust fluid to vary the extent of actuation of the hydraulic motor. In broader terms the invention contemplates the provision of an exhaust fluid receiving metering cylinder which has an adjustable volume receiving capacity.
More specifically it contemplates the provision of a metering cylinder in which a variable extent of movement of a piston in a cylinder receiving exhaust fluid controls the extent of actuation of the hydraulic motor.
In the attainment of this object said cylinder is completely closed with the exception of two fluid directing ducts and in said cylinder is a freely floating piston. In one cyclic operation of the motor the fluid is directed from one duct against the piston which then floats along in the cylinder. At the end position of the piston the latter abuts an adjustable stop at which time the cylinder is filled and no more fluid can be received by the cylinder, and the motor stops. In the next cyclic operation a reverse operation takes place, but in each operation one of the ducts is open to the return duct to permit emptying of the exhaust fluid to provide an increasing volume of the cylinder to receive the fluid exhausted in the same operation. The adjustable stops at the ends of the cylinders provide for the initial volume adjustment of the cylinder which is proportional to the volume of fluid discharge and the extent of motor actuation.
A still further object of the invention is to provide means to reduce the eflective area of the piston subjected to fluid pressure at both the start and finish of the rotation of the motor, whereby the acceleration and deceleration of the hydraulic motor is eflected gradually. This subjects the starting and stopping of the motor to less shock and provides a desirable type of rotation for many purposes.
5 The rotation of the hydraulic motor in this specific manner is found especially useful in operating machines for feeding paper strips. Herein the motor is disclosed with associated means for operating paper web feeding devices, although it is obvious that this is only illustrative. In a broader sense the present invention is directed to" novelcontrol means to accelerate and decelerate a hydraulic motor to a predetermined extent and to vary the extent as is found desirable.
2,878,015 nient a Mar. 17, meg
' Other objects of the invention will be pointed out in the following description and claims andillustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle. In the drawings: Fig. 1 is a diagrammatic representation of the components of the apparatus and their inter-connection and the paper feeding device operated thereby to intermittently feed the paper web predetermined amounts. Fig. 2 is a perspective view of some of the apparatus shown in Fig. 1. 1
Fig. 3 is a timing diagram.
Constant fluid pressure source The hydraulic motor to be described, which is operated herein to intermittently feed a paper strip a predetermined distance, is actuated by fluid at a constant pressure level derived from a hydraulic pump 10 preferably of the gear type. The hydraulic gear pump 10 (Fig. 1) is continuously driven by an electric motor. 11. A duct 12 is connected to the suction side of the gear pump 10 to draw fluid from a reservoir 13, said duct 12 having connected I at its end a foot valve 14 dipping in the reservoir 13. The duct 15 is connected at one side to the pressure side of the gear pump 10 and at theother side to a filter 16 which in turn is connected to apressure regulator valve 17 having an overflow pipe 18, dipping inthe reservoir 13. The Out side of pressure regulator 17 is connected to an accumulator 19 which serves'to keep the pressure at a constant predetermined level, said fluid then being directed through a check valve 20 to a duct 21.
The hydraulic motor 22 is of the fluid actuated type and the duct 21 is connected to the inlet side 23 of the hydraulic motor, whereby the pressureof the fluid in the duct 21 rotates said motor as long as the fluid output port 24 is unblocked to permit free exit of the exhaust fluid at a lower pressure through a duct 25.
Paper feeding mechanism The speed control for the hydraulic motor 22 is adapted herein to regulate and determine the extent of paper feed and to effect the feed in an intermittent manner. To this end the driven shaft 29 of thehydraulic'motor 22' has connected to it a gear 30 which drives through an idler change gear 31 a gear 32 connected to the feed roll shaft 33. By gears 35 a parallel feed roller shaft 34 is driven in order to oppositely drive a pair of feed rolls 36 between which a paper strip 37 passes. Said strip is drawn from a roll (not shown), and has associated therewith a tension or slack roller 38. The paper strip is thus fed in the direction of the arrow shown in Fig. 2.
Machines of this type are provided wtih several pairs of" Shuttle or control valve The closing or opening of the output side of the hydraulic motor 22 at output port 24 is controlled by a con-' trol valve 40 which is actuated in a 'manner'designed to produce the desired rotational characteristics to the hy-- draulic motor 22.
Said control valve comprises a block 41 suitably bored to provide a cylinder and associated ports and ducts. The shuttle valve comprises a cylindrical bore in which fits-a" spool type valve. The output port'25 ofhydraulic motor 22 is connected to the central input port 43 and is adapted; to be completely closed by a central piston to stopthc rotation of the hydraulic motor 22. In the position shown in Fig. 1 especially piston 44 has opened the input port 43 to a chamber 45, thus enabling fluid flow in the direction of the arrow to a duct 46 connected to chamber 45. In a lowered position (Fig. 2) of said piston 44 or righthand in Fig. l fluid communication is made between in put port 43 and a chamber 47 which has a connection to a duct 48. Hence, it will be seen that piston 44 alternately directs the fluid output in duct 25 to either chambers 45 and 47 and related ducts 46 and 48, for a reason soon to be evident.
Said shuttle valve carries upper and lower end pistons 50 and 51 adapted to close or open chambers 53 or 54 which have fluid communication on one side to the respective ducts 46 and 48 and on the other side to related ducts 55, 56 which returns fluid back by a return duct 57 to the reservoir 13 (see Fig. 1).
The movements of the shuttle valve to elfect the desired rotational characteristics of the hydraulic motor 22 are controlled by a profile cam 60 against which bears the piston 50, and a spring 58 causes said piston assembly to follow the profile of the cam 60 as the latter is rotated.
Metering valve Associated with the control or shuttle valve is a metering valve which adjustably limits or meters the volume of fluid discharge from the exit port 24 of the hydraulic motor 22.
In its simplified form it consists of a closed cylinder 61 in which a freely floating piston 62 moves in one direction or the other according to whether fluid emerges from duct 46 or duct 48. When the hydraulic motor has stopped, piston 62 is in such position that fluid emerging from either ducts 46 or 48 will strike one face or the other of the floating piston 62 shifting it in the cylinder in a related direction until it reaches its limit position at which time the cylinder is filled with fluid and stops the motor. The available volume in the cylinder is determined by adjustable stops 63 and 64, and since they regulate the extent of movement of the floating piston 62, the volume of the cylinder is regulated. Further, the volume of fluid discharge is regulated to control the extent of rotation of the hydraulic motor, and the extent of paper feed.
It is also explained that when fluid discharges into the cylinder by duct 46, for example, the fluid already in the cylinder is emptied by the other duct 48, since piston 50 has effected communication between ducts 48 and S6. The same emptying operation takes place when fluid discharges ,in the cylinder by duct 48.
In both Figs. 1 and 2, a. more detailed construction of the metering valveis shown. At each end of the cylinder 65 stop plugs 70 and 71 are fitted and each consists of a cylindrical plug having channeled end rings carrying conventional piston rings 72. The plug is reduced in diameter in the mid-portion at 73 to form an annular chamber 74 communicating with the bore 46 or 48' in the cylinder 61 to which ducts 46 or 48 are connected. A central hole or orifice 75 in each stop plug is intersected by a hole 76 which opens to the chamber 74, formed by the reduced diameter mid-portion 73.
The piston 62 floatsor moves in the cylinder 61 between the two plugs 70 or 71 and when the cylinder has been previously filled one or the other of the two tapered pins 77 carried by the piston 62 enters the orifice '75 of the related plug '70 or 71. To vary the cylinder volume and extent of displacement of piston 62, each plug 70, 71 is movable more or less into the cylinder by forming stops 63 and 64 as conventional adjusting screws which are attached to plugs 70 and 71 and are locked into position by lock nuts 79.
If the fluid discharge emerging from ducts 46 or 48 is not initially restricted, the motor would be rapidly accelerated which is not desirable. With the construction shown and described the .efiective area of the piston 62 at the instant of starting is the reduced area exposed by the orifice 75 of the elfective stop plug to the tapered pin 77. This reduced effective area at the instant of start decreases the rate of acceleration of the hydraulic motor in its angular excursion or rotation from zero to maximum velocity. As the other tapered pin 77 of the floating piston 62 moving in the cylinder 61 approaches the orifice 75 of the other stop plug the escaping fluid will be gradually restricted, thus, gradually decelerating the floating piston 62- a stop, and accordingly the hydraulic motor.
Cyclic operations It is desirable to eflect cyclic operations of paper feed by initiating the rotation of the hydraulic motor at desired times. A convenient way of accomplishing this is described as follows:
A motor 80 drives a shaft 81 through a belt drive 82 and interposed between shaft 81 and the shaft 83 carrying the cam 60 is an electromagnetically controlled clutch 84 of conventional construction. One element of the clutch is constantly rotated by shaft 81 and the other element of the clutch which is attached to shaft 83 is clutched thereto when a clutch release arm 85 is rocked as a result of the energization of a control magnet 86. No electrical circuit for energizing the clutch control magnet 86 is shown herein since it is evident that various means may be provided to complete the energizing circuit to energize the magnet 86.
The cam 60 is so designed that in one half revolution of shaft 83 during one cyclic operation it will move the piston 44 upwardly from the neutral position and back to neutral to cause duct 46 to receive the fluid discharge, and in a successive half revolution of shaft 83 during the next cyclic operation the piston 44 is moved downward from neutral position and back thereto to cause duct 48 to receive the fluid discharge. Thus, it is necessary that the clutch 84 permit only half revolutions of the shaft 83 and other shafts during successive cyclic operations.
Detent mechanism From Figs. 1 and 2 it will be seen that secured to the driven shaft 83 is a gear 90 which drives a gear 91 secured to a counter shaft 92, through an idler gear 93. Counter shaft 92 carries profile earns 94 and 95. The profile cams 94 and 95 are adapted to receive a half revolution for each cyclic operation. Pivoted on a stud 96 is a detent in the form of a bell crank, the rearward sharpened detent arm 97 being adapted to engage a ratchet detent wheel 98 secured to the hydraulic motor drive shaft 29. At the stopped position of the motor, detent arm 97 engages a tooth of the ratchet wheel 98. When clutch 84 engages, cam 94 begins to turn in the arrow direction to cause a lobe 99 of the cam 94 bearing against a wheel 100 carried by a follower arm 101 integral with detent arm 97 to rock the detent arm 97 free of the ratchet wheel 98, permitting the hydraulic motor to rotate. A short time thereafter and while detent arm 97 is in the up position a lobe 102 of cam 95 moves away from a follower wheel 103 carried by a latch pawl 104 and permits it to be rocked by a spring 105 to cause a lug 106 to catch under the follower arm 101, thereby retaining the detent arm 97 in an up position free of the detent wheel 98, while said hydraulic motor is rotated. These timing relationships are evident in the timing chart of Fig. 3.
As the piston 62 of the metering cylinder approaches its final position, the diametrically opposite knockofl lobe 102' of cam 95 will then rock latch arm 104 to unlatch the bell crank 97-101, and the detent arm 97 will now engage a tooth of the detent wheel .98, bringing the hy'.
draulic motor to a dead stop position. There is sufficient leakage in the motor and control valve 40 to permit the tooth of the detent wheel 98 to drift against the detent pawl arm 97, thus assuring an accurate mechanical stop.
Sheet severingmechanism While the present apparatus so far described constitutes a useful entity in a paper web feeding apparatus, it may be desirable to sever the predetermined lengths of paper fed into separate sheets.
To this end paper web is fed between a fixed cutting blade 110, and a reciprocable guillotine blade 111. A motor 112 drives a shaft 113 by a belt drive 114. A second electromagnetic clutch 115 controlled by a solenoid 116 clutches shaft 113 with an eccentric cam 117. The eccentric cam moves the guillotine blade 111 against the companion blade 110 to sever the paper web, forming a sheet of a predetermined length, which drops in a storage magazine 118.
It should be understood that by properly selecting the gear'drive to counter shaft 92, the detent mechanism, is proportioned for various lengths of paper which is fed, and primarily determined by the adjustable stops 63 and 64 of the metering cylinder. To this end gears 30, 31 and 32 may be a conventional adjustable change gear mechanism in a change gear box 119 (Fig. 1).
While there have been shown and described and pointed out the fundamental novel features of the invention, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.
What is claimed is:
1. In a hydraulic apparatus, the combination of a hydraulic motor whose rotation is started and stopped by respectively opening or closing the fluid discharge exit port of said motor, a control valve having its entrance port connected to said exit discharge port, said control valve having a discharge port, and a piston in said valve normally closing said fluid exit discharge port of said motor to stop said motor, means for positioning said piston to open said fluid exit discharge port to start said motor and discharge the exhaust fluid to the discharge port of said control valve, a metering valve having an entrance port receiving the discharged fluid from the discharge port of said control valve, a piston freely floating in the cylinder of the metering valve against which the discharged fluid impinges to move the piston in the cylinder, and means adjustable by the operator of the machine for limiting the extent of movement of the piston in the cylinder, whereby the volume of discharged fluid and the stopping of the motor is governed by the extent of move ment of the piston.
2. In a hydraulic apparatus, the combination of a hydraulic motor whose rotation is started and stopped by respectively opening or closing the fluid discharge exit port of said motor, a control valve having its entrance port connected to the fluid discharge port and having a pair of discharge ports, a piston in said valve for closing the discharge exit port to stop said motor and for opening said discharge exit port to rotate said motor and directing the discharged fluid to either of two discharge ports of said control valve, means for operating said piston to open the discharge exit port to rotate said motor and to effect discharge of the fluid to one and then the other of said two discharge ports of the control valve in successive startstop cyclic operations of said hydraulic motor, a metering valve having a piston floating in a closed cylinder and a pair of entrance ports connected to the respective one of the two discharge exit ports of the control valve, which entrance ports open in the cylinder in such a way as to impinge the fluid discharge against the piston to move it in the cylinder in one direction and then the other in successive cyclic operations, and means to limit the movement of the piston in each of the two directions it moves, whereby said limiting means stops the movement of the piston when said cylinder is filled with discharged fluid.
'6 3..A=hydraulic.apparatus defined in claim 2 wherein the piston of said control valve is operated and positioned by said operating means to normally close the fluid discharge exit port to stop the motor, then positioned to open said port to initiate the rotation of the motor to an extent determined by said metering valve, and then positioned to close said port to stop the motor, successively in each cyclic operation of the hydraulic motor. v 4. A hydraulic apparatus defined in claim 2 wherein the control valve is provided with two additional pistons, each adapted to connect the entrance port of the metering valve not receiving the discharged fluid to a fluid return duct, whereby the cylinder of the metering valve is empted of previously discharged fluid as new discharged fluid is entered in the cylinder by an entrance port receiving discharged fluid.
; 5. A hydraulic apparatus defined in claim 2 wherein the piston of said metering valve carries a tapered stud, and the discharged fluid from an entrance port is discharged into an orifice normally blocked by said tapered stud whereby the area of the piston impinged by the discharged fluid is initially restricted and a gradual acceleration of rotation of the motor is eflected at the start as the piston moves said stud out of the orifice.
6. A hydraulic apparatus defined in claim 4 wherein as said piston moves in the metering valve the fluid previously discharged in the cylinder is emptied through an orifice of an entrance port, and the piston of said metering valve carries a pair of tapered studs, one of which studs fits in the orifice of the entrance port receiving the discharged fluid to reduce the effective area of the piston impinged by the discharged fluid and gradually increases the area as said piston is moved in the cylinder to effect a gradual acceleration of the motor at the start, and the other stud is received by said first orifice to gradually close said first orifice to decrease the rate of discharge of the emptied fluid, to thereby effect a gradual deceleration of the motor to a stop.
7. In a hydraulically driven paper feeding apparatus, the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, the starting and stopping of said motor being effected by respectively opening and closing an exit fluid discharge port, a control valve having a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston for opening said fluid discharge port during a predetermined period to cause the motor to rotate during said predetermined period, a metering valve having a cylinder receiving the fluid discharge from the control valve to cause the rotation of the motor and feed of the paper strip until the cylinder is filled, and means for decreasing the volume of the cylinder of said metering valve to effect rotation of the motor less than said predetermined period, and thereby predetermine the extent of paper feed.
8. In a hydraulically driven paper feeding apparatus, the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, a detent engaging a ratchet wheel attached to the driven shaft of said motor to lock said motor against rotation, the starting and stopping of said motor being effected by respectively opening and closing an exit fluid discharge port and the disengage ment of said detent from said ratchet wheel a control valve having a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston for opening said fluid discharge port during a predetermined period to cause the motor to rotate during said predeter mined period, cam operated means operable synchronously with said cam for disengaging the detent from said ratchet wheel when said control valve opens said fluid discharge port, a metering valve having a cylinder receiving the fluid discharge from the control valve to cause the rotation of the motor and feed of the paper strip until the cylinder is filled, said cam operated means causing the men detent to engage said ratchet wheel to lock said motor against further rotation, and means for decreasing the volume of the cylinder of said metering valve to effect rotation of the motor less than said predetermined period, and thereby predetermine the extent of paper feed, said cam operated means being timed to cause the detent to engage the ratchet wheel to stop the motor for difierent extents of paper feed.
9. In a hydraulically driven paper feeding apparatus, the combination of feeding rollers for feeding a paper strip to a predetermined extent, a hydraulic fluid operated motor for rotating said feeding rollers, said motor having an exit fluid discharge port which is respectively closed and open to stop and start said motor, a control valve having an entrance port connected to the discharge port and a piston adapted to close and open said fluid discharge port, a cam for reciprocating said piston to first open said fluid discharge port to start the motor and then close said fluid discharge port to stop the motor, ametering valve comprising-a cylinder, a floating piston movable therein to a limited extent to predetermine the volume of the discharged fluid and having an entrance port receiving the fluid discharge from the control valve and opening in the cylinder of the metering valve to cause the fluid discharge to impinge upon the piston to permit rotation of the motor and feed of the paper strip until the cylinder is filled, and means for governing the extent of movement of the piston in the cylinder to vary the volume of the cylinder of the metering valve, the extent of rotation of the motor, and the extent of paper feed.
References Cited in the file of this patent UNITED STATES PATENTS' '2,10s,s24 Simonds Jan. 18, 193s
US661114A 1957-05-23 1957-05-23 Hydraulic control mechanisms Expired - Lifetime US2878015A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3511426A (en) * 1968-08-07 1970-05-12 Control Data Corp Mechanism for intermittently advancing and stopping material
US20060201004A1 (en) * 2003-03-21 2006-09-14 Per-Ola Vallebrant Device for controlling hydraulic power units
US20060249015A1 (en) * 2003-03-21 2006-11-09 Per-Ola Vallebrant Device for controlling a hydraulically driven motor
US20070034077A1 (en) * 2003-03-21 2007-02-15 Per-Ola Vallebrant Arrangement for controlling a hydraulically driven motor

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2105824A (en) * 1936-07-02 1938-01-18 Oilgear Co Sectional drive

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2105824A (en) * 1936-07-02 1938-01-18 Oilgear Co Sectional drive

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3511426A (en) * 1968-08-07 1970-05-12 Control Data Corp Mechanism for intermittently advancing and stopping material
US20060201004A1 (en) * 2003-03-21 2006-09-14 Per-Ola Vallebrant Device for controlling hydraulic power units
US20060249015A1 (en) * 2003-03-21 2006-11-09 Per-Ola Vallebrant Device for controlling a hydraulically driven motor
US20070034077A1 (en) * 2003-03-21 2007-02-15 Per-Ola Vallebrant Arrangement for controlling a hydraulically driven motor
US7451790B2 (en) 2003-03-21 2008-11-18 Parker-Hannifin Corporation Device for controlling hydraulic power units
US7487706B2 (en) * 2003-03-21 2009-02-10 Parker-Hannifin Corporation Device for controlling a hydraulically driven motor
US7784391B2 (en) * 2003-03-21 2010-08-31 Parker-Hannifin Corporation Arrangement for controlling a hydraulically driven motor

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