US2962960A - Remote positional control for hydraulic presses - Google Patents

Description

I F. s. SALTER 2,962,960 REMOTE POSITIONAL CONTROL FOR HYDRAULIC PRESSEZS 7 Dec. 6, 1960 Filed Sept. 27, 1957 INVENTOR United States Patent REMOTE POSITIONAL CONTROL FOR HYDRAULIC PRESSES Frank Sidney Salter, Parkstone, England, assignor to The Loewy Engineering Company Limited, Bournemouth, England, a corporation of Great Britain Filed Sept. 27, 1957, Ser. No. 686,718

Claims priority, application Great Britain Sept. 29, 1956 8 Claims. (Cl. 100-256) This invention relates to the remote control of hydraulic presses, such as forging presses, and, in particular, to mechanisms for the remote control of the movement of the press tool. The invention relates, in particular, to forging presses in which the tool is carried by a crosshead or platen moved by hydraulic pressure fluid, and in which the movements of the tool-carrying member, and hence the deformation of the ingot to be forged by the tool, are regulated through the main control valve which governs the admission of hydraulic pressure liquid to the main cylinders of the press.

A conventional hydraulic forging press was generally operated in such a manner that the actuating lever of its main control valve was moved into a position corresponding to a valve opening which, in the press operato-rs judgment, was most likely to result in the desired speed of the tool and deformation of the ingot. During the working stroke of the tool, the operator had continuously to watch the actual movement of the tool and to effect through the actuating lever corrections of the valve opening which were required.

Manual control of the working stroke of hydraulic forging presses of the conventional type was therefore a task which demanded a high degree of concentration and skill on the part of the operator. Added to the strain on the operator was the physical effort required to move the actuating lever and hold the same in its position against full pressure.

The use of hydraulic servo-control mechanisms for the main' control valve in hydraulic forging presses was a partial remedy in so far as it relieved the operator from. the physical effort. Servo-control mechanisms also had'the advantage of shock-free working and sensitive speed regulation. However, it still remained necessary for the operator to watch closely the movements of the press tool and to correlate the opening of the main .con trol valve to the actual movement of the tool by effecting any necessary corrections of that opening through the servo'control mechanism. Thus, the satisfactory progress of the forging operation still remained dependent to a high degree on the skill and experience of the press operator.

It is an object of the present invention to provide improved means in a hydraulic press and, in particular,

-in a hydraulic forging press for remotely controlling the movementof the press tool, especially during its working stroke, in such a manner that the operator of the press'is relieved from the task of constantly co-ordinatice The invention will now be described by way of example with reference to the accompanying drawing, in which the only figure illustrates one example of remote control means associated with the main control valve of a hydraulic forging press.

The hydraulic forging press 10 which is shown diagrammatically can be of conventionaldesign; it includes a crosshead 11 and a forging tool 11a, the crosshead being movable through hydraulic pressure relative to the press base 12. The main working cylinder and ram of the press are not shown. The crosshead 11 and the tool 11a can be lowered until the tool is in contact with an ingot 13, as shown in chain lines in the drawing, and the ingot subjected to any desired pressure and deformed.

The admission of pressure liquid to the main cylinder of the press whichrmoves the crosshead 11 and the tool 11a is controlled by a main control valve 20 shown here only in outline, as it can be of conventional design. Extending from the casing of the control valve 20 is a rocker or cam shaft 22, whose movements control the lifting and lowering of valve elements inside the main control valve 20, and, thereby, the admission of hydraulic pressure fluid to the main cylinder of the press during the working and return strokes of the moving crosshead 11. The shaft 22 carries an arm 23 extending between a pair of opposed hydraulic plungers 24 and 24a displaceable in cylinders 25 and 25a, each of the said cylinders being in fluid communication through lines 101 and 102 respectively with a servo-control valve 21, which may beof any suitable design.

In the embodiment shown, the servo-control valve has a casing 103 which is stationary, and a movable cylinder 104, in which two pistons and 106 respectively are displaceable together. The movable cylinder 104 is attached through a linkage system 27 to the rocker shaft 22; the two pistons 105 and 106 are connected through a rod 26 to a remote control system for the movements of the crosshead 11, which will be described in detail further below. Guides 26a ensure straight line movement of the rod 26.

' The casing 103 of the servo-control valve 24, as well as movable cylinder 104, are provided with suitable ports and passageways for a hydraulic control fluid, and the casing-103 is further connected to lines 107 and 108 for the admission and discharge of that fluid. The servocontrol valve 21 operates in such a manner that upon downward movement of the rod 26, hydraulic fluid is admitted to the cylinder 25, and that upon upward movement of the rod 26, hydraulic fluid is admitted to the cylinder. 25a, whereby the arm 23 is rocked in a clockwise or counter-clockwise direction respectively.

The remote control mechanism 40 for the movement of the crosshead 11 of the press comprises a housing 41 .44 and the slit 45 are parallel to each other, and extend over a substantial part of the length of the housing 41. The scales 43 and 44 correspond to the length of the press stroke, and are suitably graduated in unit lengths. -A pair of adjustable and releasable stops 47 and 47a are movably supported on the guide portion and are adapted to be held in position thereon in any suitable manner. They may be, for example, simflar to typewriter tabulator stops, so that they can be positioned at any desired point along the scale 44.

The control mechanism 40 comprises further a first chain and sprocket system 50 and a second chain and v sprocket system 61.

11 of the press, so that the movement of the crosshead is transmitted to that system. The system comprises further an endless chain 52 and a number of guide sprockets 52a for the latter mounted on the machine frame. 'The chain 52 rotates a sprocket 53, mounted on the same shaft as a sprocket 54 so that sprocket 54 is fixed for rotation with sprocket 53, the movement of the second sprocket 54 being transmitted to achain 55 which extends between sprockets 54 and 56. The'chain 55 will therefore move at a speed corresponding to that of the crosshead 11. Attached to a link of chain 55 is a pointer 57 which cooperates with the left hand scale 43. The pointer 57 will show, therefore, the actual position of the crosshead 11 at any particular instant during its movement.

The second chain sprocket system 61 includes a chain 62 which extends between two sprockets 63 and 64. Secured to chain 62 is a handle 65 which projects through slit 45 to the front of the panel 42 and across theright hand scale 44. The handle is in a position in which it is easily accessible to the operator of the press.

The sprocket 64 is further connected through a shaft 69 to a device 90 which limits the maximum speed of sprocket 64 and thus that of handle 65. This device may include brakes which are controlled by a centrifugal governor 91, or a fluid dashpot mechanism, or any other well-known device by which the speed of the shaft 69, resulting from movement of chain 62 when the handle 65 is manually operated, can be kept within limits. It is understood that means may be provided to adjust the device 90, and thereby the maximum speedfor which the device is set.

The handle 65 can be moved by the operator along the scale 44 and indicates, by means of a pointer on that scale, the desired position of the crosshead 11 at any particular instant, so that the actual position of the crosshead, as shown on scale 43, and that intended position of the crosshead, as shown on scale 44, can always be readily compared with each other. The movement of the handle 65 along the scale 44 is limited by the ad justable stops 47, 47a.

The endless chains 55 and 62 are in contact at diametrically opposite points with a sprocket wheel 70 mounted on a shaft 71, to which rod 26 is attached. Movement of the chains 55 and'62 at equal speeds will result in a rotation of the wheel 70, without any vertical displacement thereof. Any differential .movement between the chains 55 and 62 results not onlyin a rotation of wheel 70, but also in the latter beinglifted or lowered, according to which of the two chains 55 or 62 moves faster.

An auxiliary hand-control 80 is provided for the servocontrol valve 21; it includes a lever 81 and linkage member 82 which are attached to rod 26.

The remote control mechanism according to the invention operates as follows:

Before the movement of the crosshead is started, the operator adjusts the position of the stops '47, 47a on the scale 44, so that the distance therebetween corresponds to the desired length of stroke of the crosshead. He then grasps the handls 65 and moves it downwards towards stop 47a at a certain speed which, according to his judgment, corresponds to the desired speed of the crosshead 11. As the handle moves down, the chain 62 is moved, and since the crosshead and the chain 55 are still stationary, the wheel 70 rolls along on chain 55 and is displaced downwardly, rendering the servo-control mechanism 21 operative through the rod 26 and the two plungers 105 and 106. As described before, this will cause pressure fluid to flow into cylinder 25 and displace plunger 24 to the right, thereby rocking shaft 22 in a direction which causes the main control valve 20 to be so operated that fluid pressure is admitted to the main cylinder of the press 10, and the crosshead 11 begins to move.

The chain 52 is now displaced and moves the chain 55 and pointer 57 relative to the scale 43,'thereby indicating the actual'position of the crosshead during'its stroke.

The downward movement of the wheel 70 which may have started during the original downward movement of handle 65 is first slowed down and then balanced owing to the movement of chain 55 which moves with the crosshead 11 until the movement of handle 65 is stopped whereuponthe wheel 70 moves upwardly owing to continued movement of chain 55 to displace plunger 24a to the left and thereby rock shaft 22 in a direction which causes the main control valve to be so operated that fluid pressure to the main cylinder of the press is-cut off and the crosshead 11 is thereby stopped. Hence it is understood that wheel 70 is sensitive to the difference between the movement of the crosshead and the movement of the handle, which is reflected by the movement of their respective chains, so thatthe wheel moves up or down or is stationary in response to the direction of and the magnitude of the difference between the crosshead and handle movements.

If the crosshead moves at a speed which corresponds to the desired speed, i.e., the speed at which the operator is moving the handle 65, the wheel 70 will not undergo any upward or downward displacement, and the position of the servo-control mechanism 21, and thereby also that of the main control valve 20, are unchanged. The hydraulic pressure to the cylinder of the press remains therefore the same.

If, however, the downward movement of the crosshead 11 is slower than that of the handle 65, then wheel 70 is moved downwardly to also move the shaft 71 downwardly so that the servo-control mechanism 21 is operated, and also therethrough the main control valve 20, resulting in an increase in hydraulic pressure in the cylinder of the press, and in acceleration of the crosshead movement. This will continue until the movement of the crosshead corresponds to the desired movement, whereupon the downward displacement of wheel 70 and shaft 71 ceases. Conversely, if the crosshead of the press moves down faster than the handle 65, the wheel 70 and shaft 71 will move upwardly and the servo-control mechanism 21 and therethrough the main control valve 20 will be operated so as to decrease the hydraulic pressure in the cylinder of the press, with a consequent deceleration of the movement of the crosshead. This continues until the speed of the crosshead is equal to the desired speed.

The above-described corrections of the crosshead speed in one direction or the other are automatically effected during the stroke of the crosshead 11, and it will be seen that the crosshead follows, during its entire stroke, the movement of the handle 65, or, in other words, the handle 65 leads the crosshead 11.

At the end of the press stroke, the handle 65 meets either stop 47 or 47a, whereby the chain is stopped. As servo-control mechanism 21 and main control valve 20 do not alter their respective positions at the same time, crosshead 11 continues its movement so that wheel 70 rolls upwardly along chain 62 thereby operating, through rod 26, the servo-control mechanism 21, and therethrough the main control valve 20, so as to interrupt the flow of hydraulic pressure fluid to the cylinder of the press, and stop movement of the crosshead.

The device prevents the operator from moving the handle 65 too fact, and at a speed at which the crosshead 11 cannot follow. The device 90 is previously adjusted before operation of the press at a speed which is equal to, or preferably slightly less than, the maximum speed at which the press can be safely operated.

As mentioned before, movement of the crosshead 11 continues for a short distance after the handle 65 has met either stop 47 or 47a. This additional movement of the crosshead willbe substantially constant in a press of given design and can be allowed for by off-setting the graduations of scale 44 relative to scale 43, by the excess stroke of the crosshead, or by adjusting the position of the stops 47 or 47a on the scale 44. The crosshead 11 gvill then stop at the required distance from the press ase. r

Normally, the stops 47 and 47a determine the desired stroke of the handle 65, and thereby also that of the crosshead 11, so that the operator cannot move the crosshead beyond a fixed position determined by the two stops. As they are of the releasable type, the handle 65 can, if desired, be moved past stop 47 or 47a, so that, in exceptional cases, the crosshead 11 may be moved beyond the pre-set stroke, if required.

The auxiliary hand-control 80 is" retained, so that in the event of any emergency, the operator of the press can interrupt instantaneously the admission of pressure fluid to the press cylinder.

It is one of the important features of the invention that the handle 65 is moved continuously by the operator throughout the press stroke, and that the speed of the handle determines that of the press, so that the operator can lead the crosshead 11 during its stroke. The in vention provides also for the automatic stopping of the crosshead after it has performed a preset stroke, and prevents the crosshead from exceeding the permissable maximum speed.

The invention therefore enables the operator to con centrate his attention on the progress of the forging process. It enables him further to move the crosshead at or close to the maximum permissible speed so that the press can carry out a greater number of working strokes in a given time. This, again, may mean that less reheating of ingots is required, which is an important advantage.

The invention is not limited to the embodiment shown and described.

What I claim is:

1. Remote control means for the press tool of hydraulic presses having a tool carrying crosshead moveable under hydraulic pressure relative to a stationary pressure platen, and having a servo-mechanism for regulating the flow of hydraulic fluid for displacing said tool carrying crosshead, said remote control means comprising a differential unit in operative relationship with said servo-mechanism and comprising a first movable control means actuated by displacement of said crosshead, a second movable control means actuated by the press operator, and a driven member connecting both control means to the servo-mechanism and thereby driven by differences in the movement of both said control means whereby variations between the movement of both control means throughout the stroke of the crosshead cause a displacement of said driven member which is utilized to control said servo-mechanism in a direction eliminating the unbalance, said remote control means further including a housing for said differential unit, said housing being provided with a scale for each of said control means, both of said scales being adjacent each other and identically proportional to the stroke of the press, each of said control means being provided with a pointer overlying one of said scales, the pointer of said first control means on the scale corresponding thereto indicating the instantaneous actual position of said crosshead during displacement thereof, the pointer of said second control means indicating on the scale corresponding thereto the instantaneous intended position of said crosshead, whereby said pointers enable controlling the operation of said servomechanism in relation to the actual movement of said crosshead.

2. Remote control means according to claim 1, wherein an adjustable speed control is coupled to said second movable control means whereby the maximum velocity at which the press tool can operate is maintained within predetermined limits.

3. Remote control means according to claim 1, wherein said second movable means is associated with stop means for determining the degree of displacement thereof and thereby the length of the stroke of said tool carrying crosshead.

4. Remote controlmeans for the press tool of hydraulic presses having a tool carrying crosshead movable under hydraulic pressure relative to a stationary pressure platen, and having a servo-mechanism for regulating the flow of hydraulic fluid for displacing said tool carrying crosshead, said remote control means comprising a differential unit in operative relationship with said servo-mechanism and comprising a first movable control means actuated by 3 displacement of said crosshead, a second moveable control means actuated by the press operator, and a driven member connecting both control means to the servo-mechanism whereby variations between the velocities of both control means cause a displacement of said driven member which is utilized to control said servo-mechanism in a direction eliminating the unbalance, said remote control means further including a housing for said differential unit, said housing being provided with a scale for each of said control means, both of said scales being adjacent each other and identically proportional to the stroke of the press, each of said control means being provided with a pointer overlying one of said scales, the pointer of said first control means on the scale corresponding thereto indicating the instantaneous actual position of said crosshead during displacement thereof, the pointer of said second control means indicating on the scale corresponding thereto the instantaneous intended position of said crosshead, whereby said pointers enable controlling the operation of said servomechanism in relation to the actual movement of said crosshead, said first and second control means further comprising a pair of endless chain drives whose main longitudinal axes are arranged parallel one to the other, one of said chain drives being provided with a hand control and the other of said drives being driven by movement of the crosshead, and wherein said driven member comprises a sprocket wheel mounted on a longitudinally displaceable rod coupled to said servo-mechanism and in contact at diametrically opposite points with said chain drives, the arrangement being such that diflerential movement between the chain drives is resolved as longitudinal movement of the displaceable rod controlling said servomechanism and thereby said crosshead.

5. Remote control means according to claim 4, wherein an auxiliary hand control is coupled to said displaceable rod to control movement thereof independently of said differential unit.

6. Remote control means according to claim 4, wherein a further chain drive associated with said crosshead is arranged to drive one of said chain drives of the difierential unit.

7. Remote control means for hydraulic presses having a tool carrying crosshead movable under hydraulic pressure relative to a stationary pressure platen and having a servo-mechanism for regulating the flow of hydraulic fluid for displacing said tool carrying crosshead, said remote control means including a differential assembly connected to said servo-mechanism and comprising first movable control means actuated by displacement of said crosshead, second movable control means actuated by a press operator, and a driven member connecting both control means to said servo-mechanism and thereby driven by differences in the movement of both said control means whereby variations between the movement of both control means throughout the stroke of the crosshead cause a displacement of said driven member which is utilized to control said servo-mechanism in a direction eliminating the unbalance, said remote control means further including first and second indicator means each connected to one of said control means to register variations between the movement of both control means and respectively indicate instantaneously the actual position of said crosshead during displacement thereof and the intended position of said crosshead thereby enabling comparison of said positions throughout the stroke of the crosshead and operation of said second control means to control the operation of said servo-mechanism in relation tothe actual displacement of said crosshead.

8. Remote control means according to claim 7, wherein an adjustable speed control is coupled to said second movable control means whereby the maximum velocity at which the crosshead can be displaced is maintained within, predetermined limits.

References Cited in the file of this patent UNITED STATES PATENTS Coyle Apr. 26, 1910

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