US3033170A

US3033170A - Hydraulic ram apparatus

Info

Publication number: US3033170A
Application number: US842509A
Authority: US
Inventors: Norton Henry; Norton Hubert Veare; Norton Leslie Buckingham; Norton Douglas Edwin
Original assignee: Norton Tool Co Ltd
Current assignee: Norton Tool Co Ltd
Priority date: 1958-10-01
Filing date: 1959-09-25
Publication date: 1962-05-08
Anticipated expiration: 1979-05-08
Also published as: CH355352A; NL243893A; GB872951A

Description

May 8, 1962 H. NORTON ETAL 3,033,170

HYDRAULIC RAM APPARATUS Filed Sept. 25, 1959 l 2 Sheets-SheenI 1 /7 4 a 1 2f 1g Ild L [Qn 24 /3 22 23 /a/P FIG. F/G. 2.

lNv ENTORS HENQY Noz-roN HERBERT V. NorroN L EsLxE B. Narren DouLAs E NORTON ATTQQNEYS May 8, 1962 Filed Sept. 2 5, 1959 HA NORTON ETAL HYDRAULIC RAM APPARATUS 2 Sheets-Sheet 2 lNvENToRS HENRY NoZTON HERBERT V. NotzvoN LESLIE B. NoR'roN bouc-.As E.Nosz1'o- ATTORNEY:

United States Patent O M 3,033,170 HYDRAULIC RAM APPARATUS Henry Norton, Hubert Veare Norton, Leslie Buckingham Norton, and Douglas Edwin Norton, all of Horley, England, assignors to Norton Tool Company Limited, Horley, England, a company of Great Britain Filed Sept. 25, 1959, Ser. No. 842,509 Claims priority, application Great Britain Oct. 1, 1958 6 Claims. (Cl. 121-38) This invention relates to hydraulic ram apparatus suitable for numerous applications, for instance, for actuating machine tools such as hydraulic presses, Shapers and slotters, power steering gear, power transmission systems, mechanical handling equipment and rock drills.

It is an object of the invention to provide a hydraulic ram apparatus which is easily controllable to provide a variety of motions without excessive energy losses. Although in its basic form the apparatus is unusually simple it is capable of elaboration to provide a wider variety of motions.

Hydraulic ram apparatus according to the present invention comprises, in its simplest form, a double acting ram having differential effective areas, a connecting passage between the two ram chambers containing automatic unloader valve means having an open condition maintained at .above a predetermined pressure in the ram chamber of smaller effective area to permit flow from this ram chamber to the ram chamber of larger effective area and adapted to be brought into said open condition only on .attainment of a pressure substantially in excess of said predetermined pressure a source of hydraulic fluid under pressure (eg. a pump) in permanent communication with the ram chamber of smaller effective area, and a control valve communicating with the ram chamber of larger effective `area and operable to control release of hydraulic fluid.

This simple form of the apparatus provides for working and return strokes of controllable length and duration utilising a single control valve, as will be described in more detail hereinafter.

The automatic unloader valve may comprise a cylinder containing a spring-loaded piston of relatively large area controlling an outlet port in the cylinder Wall and carrying an inlet closure member which can seat on a seating of smaller .area than the piston and which is exposed to the Valve' inlet, the piston being exposed to the inlet only when the closure member is lifted from its seating, for instance by the application to the closure member of the said predetermined high pressure.

The automatic unloader valve may be provided with relief means between the piston and the seating operative to facilitate re-seating of the inlet closure member by relieving hydraulic fluid which might otherwise be trapped between the piston and the seating.

A preferred form of the invention provides a fast approach during the working stroke. In this form of the invention there is a source of hydraulic fluid at low pressure communicating with the ram chamber of larger effective area through a non-return valve. In such apparatus there may be an unloader valve between the supply of hydraulic fluid at low pressure and the last mentioned non-return valve, to unload the said supply when this non-return valve is closed.

The control valve is preferably such that the pressure at which it opens to permit fluid to escape from the apparatus is a function of the magnitude of a force applied to an acuating member of the valve. Such a valve enables the working force exerted by the ram on its working stroke to be controlled, since when the Working force is being applied by the ram the control valve 3,033,170 Patented May 8, 1962 will allow sufficient iluid to escape to maintain the effective fluid pressure on the ram at the desired value.

ln a further form of the invention providing a further range of motions, the simple types of control valve described above are replaced by a more elaborate control unit as described in the present applicants U.S. Patent No. 2,980,064 issued April 18, 1961.

The invention may be performed in various ways, and some specic embodiments will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 shows a simple form of hydraulic ram apparatus embodying the invention, as applied to a hydraulic press, with the ram stationary in its fully raised position;

FIGURE 2 shows the apparatus of FIGURE l during the approach portion of the Working stroke;

FIGURE 3 shows the apparatus of FIGURE l during the return stroke;

FIGURE 4 shows a more elaborate form of apparatus, during a fast approach portion of the working stroke; and

FIGURE 5 shows the apparatus of FIGURE 4 during the working portion of the working stroke.

In `all the drawings, identical parts have been given the same reference numerals. It is to be understood that the drawings are highly diagrammatic, with the object of illustrating the principles of the invention and the way the various valves and the like operate rather than the details of design .and construction.

rl`he hydraulic ram apparatus shown in FIGURES 1 to 3 comprises a double acting ram 10 having a cylinder 11 and a piston 12. The piston 12 has a piston rod 13 provided with a working head 14 which is required to press with a large force upon a work piece 15 resting on a base 16. The piston divides the cylinder into an upper chamber 17 and a lower chamber 18. Hydraulic fluid for operating the ram is drawn from a reservoir 19 by `a high pressure pump 20. The pump delivers fluid through a line 21 into a connecting line or

passage

22, 23,- 24, 25 which connects the chambers 17 .and 18 and which contains an automatic unloader valve 26. The unloader valve 26 comprises a cylinder 27 containing a piston 28 urged downwardly by a spring 29. The piston is provided with an inlet closure member 30 which can seat on an inlet seating 31, and itself controls the outlet port 32 in the wall of the cylinder 27. Communicating with the said connecting line between the

sections

24 and 25 thereof is a line 33 which leads to a control valve 34. The control valve 34 has a piston 35 provided with a closure member 36 which can seat on a seating 37, the

piston can be loaded by a spring 3S the force of which.

can `be adjusted by a manual control lever 39. A return line 40 leads from the control valve 34 to the reservoir 19.

The apparatus works as follows. shown in FIGURE 1 the piston 12 has finished a return stroke and is up against a dead stop 41 at the top of the cylinder 11, and the control valve 34 is in a position in which it permits free flow from the line 33 to the return line 40. The iiow from the pump 20 through the

connecting line sections

23 and 24 into the line 33 is sufficient to hold the unloader valve 26 open, as will be described later. In this condition the iiuid flow is as indicated by the arrows. When ya working stroke is to be performed the control lever 39 is moved towards the left as Shown in FlGURE 2 to increase the loading of the spring 38 and close the valve 34. The pressure then rises suiciently to overcome the resistance of the piston 12 so that the latter moves downwardly on the approach portion of the working stroke. As the piston 12 descends, uid is discharged from the lower chamber 18 and passes freely through the connecting line sections In the condition- 22, 23, the open unloader valve 26, and the connecting line sections 24, 2S into the upper chamber 17, as shown by the arrows in FIGURE 2, so that the pump 20 has only to supply enough fluid to malte up the difference in the volumes of these chambers. The operator can slow down the speed of approach by adjusting the control lever 39 towards the right. At the end of the approach, i.e. when the head 14 meets the workpiece 15, the pressure will build up as required until the valve 34- re-opens. This re-opening may take place voluntarily by the operator moving the control lever 39 towards the right, or automatically when the pressure overcomes the loading of the spring 38 with the control lever in its lefthaud position. In the latter case the maximum working force will continue to be applied to the work-piece so long as the control lever remains in the left-hand position. Movement of the control lever towards the right progressively eases the working force, that is to say, the position f the lever determines the magnitude of the working force. turn stroke as shown in FIGURE 3, the control lever 39 is moved fully to the right, to open the valve 34. The piston 12 can now rise freely, the fluid in the upper chamber 17 being discharged freely through the

lines

25 and 33, and through the valve 34, and all the delivery of the pump 20 passing into the lower chamber 18 so that there is no flow through the unloader valve 26 which accordingly closes. Since the pump 2G is at all times in communication with the lower chamber 18 the return movement of the piston begins practically instan taneously on opening the valve 34. When the piston 12 comes up against the dead stop 41 and can rise no further, the pressure in the

lines

21, 22 and 23 will rise to a high value, exerting suficient force on the closure member 3G of the unloader valve to lift it from its seating. As soon as this valve lifts, the pressure is applied to the whole under the surface of the piston 28, so that the piston is raised sufliciently to expose the port 32. The apparatus is now back in the condition shown in FIGURE l, so that the cycle described can be repeated.

It is not necessary for the return stroke to continue as far as the dead stop 41, since the return motion can be checked by moving the control lever 39 to the left to close the valve 34, whereupon another working stroke begins.

This apparatus thus provides for working and return strokes of controllable length and duration utilizing a single simple control valve.

The apparatus shown in FIGURES 4 and 5 is intended to provide a fast approach, and includes some other refinements. Its basic parts are essentially the same as those of the apparatus of` FIGURES 1 to 3, with some additions. In addition to the high pressure pump 20 there is provided a low pressure pump 5) which is connected through a low pressure unloader valve 51 and a non-return valve 52 to a line 53 which leads to the upper ram chamber 17 via the line 25. The low pressure unloader valve S1 has a valve member Se which is urged towards a seating 55 by a spring 56 and which is provided with a grooved stem 57 so that when it is lifted from its seating in a manner to be described, low pressure fluid can escape from the valve 51 through a return line 58. When the valve member 54 is closed, however, low pressure fluid must pass to the non-return valve 52. In order to ensure that the non-return valve 52 is not prevented from seating promptly by trapped low pressure fluid when it returns to its closed condition, a piston 59 is provided which holds the valve member 54 slightly open whenever the pressure in the line 53 is greater than the delivery pressure of the low pressure pump 50. One side of the piston 59 is exposed to the pressure on the outlet side of the non-return valve through a passage 60, while its other side is exposed to the delivery pressure of the pump S0 within the valve 51.

The high pressure unloader valve 26 is `also equipped To cause the piston 12 to rise on its rewith means for ensuring that trapped fluid cannot prevent it from seating promptly. In this case the lower part of the cylinder 27 communicates through a passage 61 with one end of a cylinder 62 in which is a piston 63. The space behind this piston is in communication with the upper part of the cylinder 17 through a passage 64. When the unloader valve 26 is nearing its closed position and has closed the port 32, fluid beneath the piston 28 will not be trapped since it will merely be expelled into the cylinder 62, the piston 63 being moved to the left correspondingly, there being in effect a displacement of fluid from the space of decreasing volume beneath the piston 28 into the space of increasing volume above it.

This apparatus works as follows. When the control lever is moved to the left as shown in FIGURE 4 to initiate the fast approach portion of the working stroke, fluid enters the upper ram chamber 17 not only from the high pressure pump 20 and from the lower ram chamber 18 as shown in FIGURE 2, but also from the low pressure pump Sil through the low pressure unloader valve 51, the non-return valve 52 and the line 53. The unloader valve 51 is so constructed that at the relatively low pressure needed to move the piston 12 in the approach portion of its working stroke the valve member 54 remains on its seating. In view of the large volume of uid supplied to the upper ram chamber 17 from these three sources, the piston 12 will descend rapidly. When the piston 12 meets resistance, i.e, when the head 14 touches the work-piece as shown in FIGURE 5, pressure will rapidly build up. The increase in pressure Will open the low pressure unloader valve S1, permitting low pressure fluid to return to the reservoir through the return line 5S, so that the non-return valve S2 and the bleed valve 60 closes. The low pressure part of the apparatus is now isolated from the high pressure part, which continues to operate in the manner described in relation to FIGURES 1 to 3.

What We claim as our invention and desire to secure by Letters Patent is:

1. Hydraulic double acting ram apparatus comprising a ram cylinder having a side wall and end Walls, a piston in said cylinder, a piston rod extending from said piston through one of said end walls, said cylinder, said piston and said piston rod defining a first ram chamber and a second ram chamber of smaller effective area than said iirst ram chamber, connecting passage means between said first and second ram chambers, automatic pressuresensitive unloader valve means disposed in said eonnecting passage means and having an inlet side connected to said second ram chamber, said valve means having an open condition maintained at above a predetermined pressure in said second ram chamber and a closed condition maintained at below said predetermined pressure, said valve means in said open condition permitting ow of hydraulic fluid in the direction from said second ram chamber to said first ram chamber, and in said closed position preventing such flow, said valve means being adapted to be brought into said open condition only on the attainment of a high pressure subtsantially in excess of said predetermined pressure applied to said inlet side, a source of hydraulic fluid under pressure in permanent communication with said second ram chamber, and a manual control valve operable to control release of hydraulic fluid and communicating with said first ram chamber.

2. Hydraulic ram apparatus according to claim l, in which said automatic unloader valve comprises a cylinder having an outlet port, an inlet connection to said cylinder, a seating adjacent said inlet connection, a piston slidable in said cylinder and having a cross-section greater than the cross-section of said seating, an inlet closure member carried by said piston in alignment with said seating, a spring loading said piston towards a position in which said inlet closure member seats on said seating, said piston when said inlet closure member is seated on said seating being isolated from said inlet connection, said piston when said inlet closure member is clear of said seating being exposed to said inlet connection through said seating, and said piston controlling said outlet port.

3. Hydraulic ram apparatus according to claim 2, in which said automatic unloader valve is provided with relief means, said relief means -being connected to said cylinder between said piston and said seating, said relief means being operative to facilitate re-seating of said inlet closure member.

4, Hydraulic ram apparatus according to claim l in which said control valve comprises a manual actuating member, a closure member, and means connecting said actuating member to said closure member to impart to said closure member a closing force which is a function of the manual force applied to said actuating member.

5. Hydraulic double-acting ram apparatus comprising a ram cylinder having a side wall and end Walls, a piston in said cylinder, a piston rod extending from said piston through one of said end Walls, said cylinder, said piston and said piston rod dening a first ram chamber and a second ram chamber of smaller elective area than said first ram chamber, connecting passage means between said iirst and second ram chambers, automatic pressure-sensitive valve means disposed in said connecting passage means in pressure communication with said second ram chamber, said valve means having an open condition maintained at above a predetermined pressure in said second ram chamber and a closed condition maintained at below said predetermined pressure, said valve means in said open condition permitting flow of hydraulic fluid in the direction from said second ram chamber to said first ram chamber, and in said closed position preventing such W, a source of hydraulic fluid under relatively high pressure in permanent communication with said second ram chamber, a control valve operable to control release of hydraulic -iluid and communicating with said References Cited in the le of this patent UNITED STATES PATENTS 2,381,923 Obstresal Aug. 14, 1945 2,645,960 Hutchinson July 21, -1953 2,770,222 Anderson Nov. 13, 1956 FORElGN PATENTS 828,188 Germany Ian, 17, -2