US3091140A

US3091140A - Hydraulic positioning system for gripping heads of forging machines

Info

Publication number: US3091140A
Application number: US161529A
Authority: US
Inventors: Kralowetz Bruno
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-01-07
Filing date: 1961-12-22
Publication date: 1963-05-28
Anticipated expiration: 1980-05-28

Description

May 28, 1963 B. KRALOWETZ 3,091,140 HYDRAULIC POSITIONING SYSTEM FOR GRIPPING HEADS OF FORGING MACHINES Filed Dec. 22, 1961 3 Sheets-Sheet l FIG] gu/vg K LWMVV May 28, 1963 B. KRALOWETZ 3,091,140

HYDRAULIC POSITIONING SYSTEM FOR GRIPPING HEADS OF FORGING-MACHINES Filed Dec. 22, 1961 3 Sheets-Sheet 2 nvvn/foi May 28, 1 B. KRALOWETZ 3,091,140

HYDRAULIC POSITIONING SYSTEM FOR GRIPPING HEADS OF FORGING MACHINES Filed Dec. 22, 1961 3 Sheets-Sheet 3 STEPPING 43 SWITCH mma/vroz KI UNQ (fix/0445 4 United States Patent 3,091,140 HYDRAULIC POSITIGNING SYSTEM FGR GRIT?- PING TEADS 0F FGRGING MACS Bruno Kralowetz, t. Ulrich, near Steyr, Austria Filed Dec. 22, 1961, Ser. No. 161,529 Claims priority, application Austria Jan. 7, 1961 6 Claims. (Cl. 78-99) This invention relates to an arrangement in forging machines comprising hammer tools which are radially movable toward the workpiece and a hydraulically displaceable gripping head for axially feeding the workpiece and having a hydraulic system which comprises valve means operable by electric limit switches, which are acted upon by cams which can be set in different positions depending on the desired displacement of the gripping head. When the gripping head has been started and a cam depresses the corresponding limit switch, the hydraulic system is switched over to assume the stop position and the gripping head is stopped. The switching over to effect the displacement of the gripping head is then also electrically performed, e.g., by means of a stepping switch. It has now been found that the desired position of the gripping head determined by the cam which is effective at a time may not be maintained or may not be reached or may be overrun. This is due to the fact that the gripping head is under the action of longitudinal forces which are derived from the forging forces and that it cannot be held in position by hydraulic means against the action of these forces owing to the inevitable leakage of oil, the deformation of the conduits and the fact that even a hydraulic fluid is compressible to a slight extent. The difficulties involved in stopping and holding the gripping head exactly in the desired position are due to the fact that feeding is not always effected at the same speed but may be performed at a low speed or a high one, depending on the stroke concerned. The displacement of the gripping head after the actuation of the limit switch varies with different speeds.

It is an object of the invention to provide an improvement in this respect by the provision of an arrangement which automatically and immediately compensates any undesired displacement of the gripping head after the end of an axial movement so that a more exact result of forging is ensured.

The invention resides essentially in that the cams serving to terminate respective increments of the displacement of the gripping head have associated with them run-up members which have oblique surfaces and which can also be set in different positions and each of which is adapted to act on a feeler, which is resiliently urged toward the run-up member and controls a slide valve, which is additionally provided in the hydraulic system and in response to any undesired movement of the gripping head from the desired position determined by the cam which is effective at a time causes a hydraulically effected return movement of the gripping head to this desired position. The run-up members are set in positions which correspond to those of the cams. With their oblique surfaces they force the feeler back to a smaller or larger extent against the force of the spring acting on it upon each displacement of the gripping head so that the additional slide valve is displaced, which causes now such a control operation that the desired position is resumed.

In a development of the invention, the hydraulic system comprises an auxiliary slide valve which is operable by the limit switches and which establishes the operative connection to the feeler-controlled slide valve when the system is changed over to the position for stopping the gripping head. It is thus ensured that the feeler-controlled slide valve will be operative only when the grip- 2 ping head is stopped but does not affect the control cycle in other respects.

Forging machines for which the arrangement according to the invention is intended are suitably controlled so that the piston for displacing the gripping head is permanently supplied with the pressure fluid at the rod-side end having the smaller effective piston area whereas it is supplied with pressure only from time to time at the cover-side end. This enables a control of the piston movement merely by changing the supply to the cover-side end. When pressure is supplied to the cover-side end of the piston, the latter will move in spite of the permanent supply to its rod-side end because the effective piston area on the cover-side end is much larger. When the cover-side end is connected to the drain, the piston will move toward the cover because the pressure resulting from the permanent supply to the rod-side end is larger. When the cylinder is closed on the cover side, the piston will be stopped. It is proposed according to the invention to provide in such a hydraulic system a pressure fluid conduit which leads through the auxiliary slide alve and preferably through a pressureregulating valve to the housing of the feeler-controlled slide valve, on the one hand, and, on the other hand, back through the auxiliary slide valve to the cover-side end of the piston which controls the movement of the gripping head, the feeler-controlled slide valve being arranged to open or close a discharge conduit depending on the position of the feeler. Since this pressure fluid conduit leads, on the one hand, to the cover side of the gripping head piston and, on the other hand, to the housing of the feeler-controlled slide valve, there will be equal pressure in the cylinder chamber at the cover-side end of the gripping head piston and in the slide valve housing. When the gripping head is in the desired position so that the feeler and its slide valve are in a neutral position, an equilibrium will be established and the gripping head will not change its position. On the other hand, if the gripping head is displaced from its desired position so that the feeler and with it the slide valve are displaced by means of the oblique surface of the run-up member, the slide valve will open the discharge conduit toa larger or smaller extent to reduce or increase the pressure at the cover end of the cylinder of the gripping head piston. This will result in a correcting displacement of the gripping head until the position of equilibrium of the gripping head is reached.

The feeler-controlled slide valve with the feeler is suitably secured to the gripping head bed and the gripping head comprises a longitudinal rail for receiving the runup members which can be set in different positions. Alternatively, the feeler-controlled slide valve could be carried by the displaceable gripping head and the run-up members could be stationary and carried by the gripping-head bed.

An illustrative embodiment of the invention is shown on the accompanying drawing, in which FIG. 1 is an elevation showing an arrangement embodying the invention carried by the gripping head bed and the gripping head of a forging machine,

FIGS. 2 and 3 are enlarged sectional views taken on line IIII and III-III of FIG. 1 and FIG. 4 is a diagram of the electrically controlled hydraulic system for displacing the gripping head.

A forging box 1 accommodates the hammer tools with their drive. A bed 2 for horizontally displaceable gripping head 3 is disposed before the forging box 1. The workpiece is gripped by the gripping head and is moved in longitudinal direction to enter between the hammers. It may also be rotated about its axis, if desired. The gripping head 3 is connected by a rod 4 to a piston 5.

which slides in a cylinder 6, which is accommodated in the gripping head bed 2. These parts as well as the elements for gripping and rotating the workpiece are known and for this reason are not shown in detail in FIG. 1. On that longitudinal side of the gripping head or gripping head bed which is not visible in FIG. 1, guides for cams 49 which can be set in different positions and limit switches 50 which are arranged to be actuated by the cams are disposed in the manner described hereinbelow with reference to FIG. 4. Each limit switch controls the flow of current from a source 52 to a valve of the hydraulic system for displacing the gripping head and each cam is set to terminate one of the successive displacements of the gripping head by depressing the limit switches so that the hydraulic system is changed over by the stepping switch 48.

According to the invention, a run-up member 7 having oblique engaging surfaces 8 is associated with each of these cams. These run-up members 7 are secured in a longitudinal bar 9 of the gripping head 3 and can be set in diiferent positions. A feeler 10 is mounted on the gripping bed 2 and can be displaced at right angles to the bar 9 and by means of an intermediate lever 11 acts on a slide valve 12. The slide valve 12 mounted in a suitable housing 13 is under the action of a compression spring 14, which urges the slide valve and, through the intermediary of the intermediate lever, the feeler against the run-up member 7. A pressure conduit 15 opens into and a drain conduit 16 leads from the slide valve housing 13. Pressure oil enters through a bore 17 an annular space 18 and through an annular recess 19 in the slide valve 12 reaches another annular space 20 and through a bore 21 enters the drain conduit 16. 22 is a control edge formed by the shoulder of the annular recess 19. It is apparent from FIG. 2 that the control edge 22 will more or less open or throttle the discharge of pressure fluid in dependence on the position of the slide valve determined by the feeler 10'.

FIG. 4 shows the diagram of the entire hydraulic system for displacing the gripping head. An electric motor 23 drives a pump 24, which sucks the hydraulic fluid from a reservoir 25 through a filter 26 and forces it through a check valve 27 into the conduit system. Additional pressure oil handled by a pump not shown may be added from a conduit 28 incorporating a check valve if the delivery of the pump 24 is not suflicient to meet the increased requirement for pressure fluid during a high-speed movement. Pressure oil is constantly supplied from a conduit 29 through a conduit 30 to the rod-side end of the piston 5. A slide valve 31 actuated by

solenoids

40, 41 and return

spring

42, 43 is incorporated in the conduit 29 behind its junction with the conduit 30. A conduit 32 incorporates another slide valve 33 actuated by solenoid 44 and a return spring 45 and a conduit 34 to the cover-side end of the piston 5. 35 is a by-pass conduit incorporating a throttle 36.

A conduit 37 branches from the conduit 31 and passes through an auxiliary slide valve 38 actuated by a solenoid 46 and a return spring 47 and a pressure-regulating valve 39. This conduit 37 supplies the conduit 15 to the feelercontrolled slide valve 12 and by a conduit 40 which passes back through the auxiliary slide valve 38 is connected to the conduit 34.

When the slide valve 31 is displaced to the left in FIG.

4 by the solenoid 4t} responsive to closing of the limit switch 50, the pressure oil is free to flow from conduit 29 into

conduit

32 or 35. Depending on the position of the slide valve 3-3,'pressure oil enters directly the conduit 34 for the high-speed movement of. flows for the lowspeed movement through the conduit 35 and the throttle 36 to the cover-side end of the piston 5. Whereas pressure oil is constantly supplied to the rod-side end of this piston through the conduit 30, the piston will now move to the left at low or high speed because the piston area on the cover side is much larger than that on the rod side. When the slide valve 31 is displaced by the solenoid 41 to the right from the intermediate position shown in FIG. 4, the conduit 34 will be connected to the drain either directly through conduit 32 (high-speed movement) or through the conduit 35 and the throttle valve 36 (low-speed movement) depending on the energizing of the solenoid 44 by the stepping switch 48. In this case the pressure permanently applied to the rod-side end of the piston 5 will predominate and the latter will move to the right so that the gripping head performs a return movement.

As soon as the pressure of the cam 49 which is effective at a time on its associated limit switch 50 deenergizes the solenoids of the slide valve 31, so that the latter is returned to its intermediate position shown by the

springs

42, 43, the gripping head movement will be terminated because the

conduits

34 and 32 or 35 extending from the cover side are closed. At the same time, however, the auxiliary slide valve 38' is displaced to the left when its solenoid 46 is energized by the stepping switch 48, and reaches a position, in which the previous blocking of the conduits 37 and 411 is removed. Pressure oil can then flow from the conduit 31) through conduit 37 to the housing 13 of the feeler-controlled slide valve through conduit 15 and to the cover-side end of the piston 5 through

conduits

40 and 34. When the gripping head is in the position shown, in which the feeler 1t engages the right-hand oblique surface 3 approximately in the middle thereof, the control edge 22 will open the discharge conduit 16 just to such an extent that this condition is maintained. On the other hand, if the gripping head is unintendedly displaced in one direction or another, whereby the feeler 10 and the slide valve 12 are forced inwardly or outwardly so that the drain conduit is opened or throttled further, the pressure on the cover-side end of the piston 5 will rise or fall and the piston or the gripping head will be displaced so as to return to the original, desired position. When a new movement of the gripping head is now performed, the auxiliary slide valve 38 will be moved back to its intermediate position shown by the spring 47 so that the additional device is rendered ineifective until this movement of the gripping head has been terminated and is followed by another change over, whereafter the next run-up member initiates the correcting movements. It is obvious that the same'correcting operations will result when the gripping head does not stop in its desired position and the feeler assumes from the beginning another than its neutral position.

What I claim is:

l. A hydraulic positioning system which comprises a positioning member which is movable in two mutually op posite, predetermined directions, a hydraulic motor which is operatively connected to said member and adapted to be energized by pressure fluid selectively in either of two mutually opposite senses to move said member in either of said directions, a hydraulic circuit for energizing said hydraulic motor, said circuit comprising valve means electrically operable to control the energization of said motor and the sense in which it is energized, said system further comprising electrically energizable means for operating said valve means, limit switch means for controlling the energization of said electrically operable.

means, a plurality of adjustable cam means, each of which is arranged to operate said limit switch means in a predetermined position of said member, a feeler-controlled slide valve adapted to be connected in said circuit, a feeler arranged to control said slide valve by a movement in a first direction, and a plurality of adjustable run-up members, each of which is associated with one of .said cam means and has an oblique surface, said feeler and run-up members being arranged to be relatively moved in a second direction, which is transverse to said first direction, in response to a movement of said positioning member in either of said predetermined directions, each of said run-up members being arranged to engage said feeler with a predetermined point of its oblique surface when said positioning member is in the predetermined position in which the cam means associated with the respective runup member operates said limit switch means, resilient means biasing said feeler in said first direction toward said run-up members, said slide valve being arranged to assume a neutral position when said feeler is engaged by said predetermined point of said oblique surface, said hydraulic circuit being arranged to energize said motor so as to move said positioning member to said predetermined position in response to a movement of said slide valve out of said neutral position when said slide valve is connected in said circuit.

2. A positioning system as set forth in claim 1, in which said positioning member is a gripping head of a forging machine, which is adapted to grip a workpiece and axially move the same.

3 A system as set forth in claim 2, which comprises a bed arranged to guide said gripping head and a longitudinal bar carried by said gripping head, said feelercontrolled slide valve and feeler being carried by said bed and said run-up members being carried by said bar.

4. A positioning system as set forth in claim 1, which comprises an auxiliary slide valve arranged to connect said feeler-controlled slide valve into said circuit in response to the operation of said limit switch means by one of said cam means.

5. A positioning system as set forth in claim 4, in which said hydraulic motor comprises a piston having a rod-side end on which the effective piston area is relatively small and a cover-side end on which the efifective piston area is relatively large and said valve means are arranged to supply pressure fiuid to said rod-side end constantly and to supply pressure fluid to said cover-side end from time to time, said feeler-controlled slide valve comprising a housing, said hydraulic system comprising a pressure conduit incorporating said auxiliary slide valve and connected between said housing and the coverside end of said piston, and a drain conduit controlled by said feeler-controlled slide valve.

6. A system as set forth in claim 5, in which said pressure conduit incorporates a pressure regulating valve in series with said auxiliary slide valve.

No references cited.

Claims

1. A HYDRAULIC POSITIONING SYSTEM WHICH COMPRISES A POSITIONING MEMBER WHICH IS MOVABLE IN TWO MUTUALLY OPPOSITE, PREDETERMINED DIRECTIONS, A HYDRAULIC MOTOR WHICH IS OPERATIVELY CONNECTED TO SAID MEMBER AND ADAPTED TO BE ENERGIZED BY PRESSURE FLUID SELECTIVELY IN EITHER OF TWO MUTUALLY OPPOSITE SENSES TO MOVE SAID MEMBER IN EITHER OF SAID DIRECTIONS, A HYDRAULIC CIRCUIT FOR ENERGIZING SAID HYDRAULIC MOTOR, SAID CIRCUIT COMPRISING VALVE MEANS ELECTRICALLY OPERABLE TO CONTROL THE ENERGIZATION OF SAID MOTOR AND THE SENSE IN WHICH IT IS ENERGIZED, SAID SYSTEM FURTHER COMPRISING ELECTRICALLY ENERGIZABLE MEANS FOR OPERATING SAID VALVE MEANS, LIMIT SWITCH MEANS FOR CONTROLLING THE ENERGIZATION OF SAID ELECTRICALLY OPERABLE MEANS, A PLURALITY OF ADJUSTABLE CAM MEANS, EACH OF WHICH IS ARRANGED TO OPERATE SAID LIMIT SWITCH MEANS IN A PREDETERMINED POSITION OF SAID MEMBER, A FEELER-CONTROLLED SLIDE VALVE ADAPTED TO BE CONNECTED IN SAID CIRCUIT, A FEELER ARRANGED TO CONTROL SAID SLIDE VALVE BY A MOVEMENT IN A FIRST DIRECTION, AND A PLURALITY OF ADJUSTABLE RUN-UP MEMBERS, EACH OF WHICH IS ASSOCIATED WITH ONE OF SAID CAM MEANS AND HAS AN OBLIQUE SURFACE, SAID FEELER AND RUN-UP MEMBERS BEING ARRANGED TO BE RELATIVELY MOVED IN A SECOND DIRECTION, WHICH IS TRANSVERSE TO SAID FIRST DIRECTION, IN RESPONSE TO A MOVEMENT OF SAID POSITIONING MEMBER IN EITHER OF SAID PREDETRMINED DIRECTIONS, EACH OF SAID RUN-UP MEMBERS BEING ARRANGED TO ENGAGE SAID FEELER WITH A PREDETERMINED POINT OF ITS OBLIQUE SURFACE WHEN SAID POSITIONING MEMBER IS IN THE PREDETERMINED POSITION IN WHICH THE CAM MEANS ASSOCIATED WITH THE RESPECTIVE RUNUP MEMBER OPERATES SAID LIMIT SWITCH MEANS, RESILIENT MEANS BIASING SAID FEELER IN SAID FIRST DIRECTION TOWARD SAID RUN-UP MEMBERS, SAID SLIDE VALVE BEING ARRANGED TO ASSUME A NEUTRAL POSITION WHEN SAID FEELER IS ENGAGED BY SAID PREDETERMINED POINT OF SAID OBLIQUE SURFACE, SAID HYDRAULIC CIRCUIT BEING ARRANGED TO ENERGIZE SAID MOTOR SO AS TO MOVE SAID POSITIONING MEMBER TO SAID PREDETERMINED POSITION IN RESPONSE TO A MOVEMENT OF SAID SLIDE VALVE OUT OF SAID NEUTRAL POSITION WHEN SAID SLIDE VALVE IS CONNECTED IN SAID CIRCUIT.