US2875732A - Ram for presses and the like - Google Patents

Description

March 3, 1959 o. HOFFMANN 2,875,732 RAM Foa PRESSES AND 'THE LIKE:

Filed Aug. 15, 1955 wfm United States PatentO RAM FOR PRESSES AND THE LIKE Otto Hoffmann, Kenmore, N. Y., assignor, by mesne assignments, to Lake Erie Machinery Corporation, Buffalo, N; Y., a corporation of New York Application August 15, 1955, Serial No. 528,233

Claims. (Cl. 121-38) `This invention relates to a ram for a press or the like and more particularly to such a ram for heavy duty presses such as are used in forming metal between dies.

In such heavy duty presses, it is usual to provide a so-called runaround circuit such as the one described in the copending application of Robert C. Haarmeyer, Serial No. 528,230, filed August 15, 1955, now U. S. Patent No. 2,800,110, for Hydraulic Circuit for Heavy Duty Presses and the Like. This circuit conducts the hydraulic liquid in the cylinder of the ram of the press `from its return pressure end to the working pressure end `thereof so as to permit initial rapid closing movement of the ram. When resistance is encountered, as when the workpiece is engaged, the liquid in the return pressure end of the cylinder is returned through an exhaust line into a tank or reservoir. The rams for such presses are composed of a large diameter piston part and a smaller diameter body part or end which projects through an opening at the return pressure end of the cylinder, and the runaround movement of the hydraulic iiuid is a function of the differential and effective sizes of the large piston part and the reduced body of the ram.

Such runaround circuits are entirely satisfactory to provide a rapid ram movement during the initial part of the closing stroke of the ram, but since large quantities of hydraulic fluid are required to be transferred, the pipes included in the runaround circuit are necessarily large and cumbersome. Further, special controls for such large quantities of hydraulic fluid must be provided for cutting the runaround circuit out of operation when the ram .encounters'the resistance of the workpiece.

It is the principal object of the present invention to provide a ram having a piston through which the hydraulic fluid freely passes from one end of `the cylinder to the other during the initial part of the `closing stroke ofthe ram, but which passage is closed during the Working parttof the closing `stroke as well as during the return orfopening movement of the ram. `It is another object of the invention to provide such a ram in which the opening and closing of the passage 1through the piston is a function of theresistance encountered by the piston from the hydraulic fluid in the cylinder.- t

It is another object of the invention to `provide such a ram which @is extremely simple in construction and which provides a large opening and free movement of the hydraulic iluid during the initial part of the closing movement of the ram and also provides an adequate seal against thepassagevofghydraulic fluid, both" during the working part of the closing stroke of the ram and also during the opening or return stroke thereof. p

- Another object. of the invention is to provide such a ram in"`w hich Vfull provision is `made to compensate f or the friction ofthe ram `piston against the cylinder wall.

Other objects and advantages of the invention will be apparent from the following description and drawings in which:

Fig. 1 is aplongitudinal section through the cylinder ICC 2 of a heavy duty hydraulic press enclosing a ram embodying the present invention, the parts being shown in the position occupied during the initial rapid closing movement of the ram.

Fig. 2 is a similar view showing the position of the parts when the resistance of the workpiece is encountered by the ram.

Fig. 3 is a similar View showing the position of the parts during the return or opening stroke of the ram.

The invention is shown in conjunction with a ram 5 for a heavy duty press or the like and which is contained within a ram cylinder 6. The ram cylinder is shown as having an end head 8 at its working pressure end, hydraulic uid under the pressure required for the operation of the ram being supplied from a working pressure line 9. At its opposite return pressure end 9, the ram cylinder 6 is provided with a concentric slideway or opening 10 in which the reduced body part 11 of the ram reciprocates into and out of the cylinder.. The cylinder 6 is provided at its return pressure end with a return line 12 and which is shown as containing an on-oi valve 13.

The ram 5 includes a large piston part 15 which ts within the ram cylinder 6 and is composed of two sections 16 and 18 secured together as by the screw joint 19 to provide a continuous piston. The section 16 is arranged toward the return pressure end of the cylinder 6 and has a coaxial passage 20 surrounded by an annular valve seat 21 which faces toward the working pressure end of the cylinder 6. The piston section 16 also has an enlarged annular central chamber 22 surrounding the valve seat 21. The effective cross sectional size of the pistou part 15 is greater than the effective cross sectional 'size of the reduced body part 11. The other section 18 of the piston has a concentric annular valve seat 23 within the large annular central chamber 22 and facing toward the return pressure end of the cylinder 6. This other section 18 of the piston also has a passage 24 establishing communication, past the valve seat 23, between the en larged chamber 22 and the working pressure end of the cylinder 6.

The outer extremity of this passage 24 is preferably enlarged, as indicated at 25, and this passage is crossed by radial arms 26 which -are formed integrally with the piston part 18 and support an integral hub 28. This hub is provided with a relatively large coaxial recess 29 whichfaces toward the cylinder end head 8 and this hub is provided with a relatively small coaxial recess 30 which faces toward the return pressure end of the cylin der 1.

The reduced body part 11 of the ram 5 is provided with a still further reduced neck 35 which is arranged in the passage 20 of the piston section 16. This neck 35 is connected with an enlarged valve head 36 arranged in the enlarged chamber 22. This valve head 36 is provided with an axially facing valve face 38 arranged to engage the valve seat 21 and is also provided with an opposite axially facing valve face 39 arranged to engage the valve seat 23,

On the side of the valve head 36 which faces the working pressure end of the cylinder 6, the reduced part 11 of the piston is formed to provide a still smaller coaxial neck 40 to which a coaxial valve rod. 41 is secured. This valve rod 41 extends through a slideway 42 provided in the hub` 28 between the recesses `or spring seats 29 and 30 and terminates in a head 43 arranged in a recess 44 provided in the cylinder head 8.` A relatively -smal-l helical compression spring 45 surrounds therod 41'and is interposed between the spring seat or recess 30 and the reduced neck 40 of the ram. A larger helical compression spring 46 surrounds the valve rod 41 and is interposed between the valve seat or recess 29 and the head 43 of the valve stem 41. An important consideration lis that the spring 46 be of suiiicient size andstrength to overcome `the friction between the piston 18 and the cylinder 6 during the closing movement of the ram and to this end, it fis made substantially stronger than the Vspring 45. These springs Vare in compressive `relation to each other and to the hub 28.

ln operation, at the start of the closing stroke kof the ram, thc valve 13 is closed to block off the return Vline `12. Accordingly, full line pressure from the working `pressure line 9 is impressed against the reduced body part 11 of the ra1n 5, the effective cross sectional size iof Vwhich is equal to that of the cylinder opening 10. Because of this small effective size of the reduced body .part 11 of the ram, it is forced out of the cylinder 6 fat a .high rate of speed, thus providing the rapid movement or the ram during the initial part of the closing stroke thereof.

This rapid closing movement of the reduced body part 11 of the ram 5 is transmitted through the rod 41, its :head 43 and through the helical compression spring 46 'to the hub 2S forming part of the piston part 18. This .causes the piston part 18 to move along lwith the reduced body part 11 of the ram. .lt is essential, however, that the spring 46 be strong enough to overcome the friction `between the piston part 18 and the cylinder 6 so that the valve head 36 does not seat against the seat 21 during this movement. By not seating the hydraulic fluid which otherwise would be trapped in the right hand end of lthe cylinder 6 is free to flow through Vthe ram, as indicated by the arrows, to the left-hand `or working pressure end thereof. This flow, which is the equivalent of the lflow through the runaround circuit in a conventional 4heavy duty press7 is between the piston 15 and reduced body part of the ram through the passage 29, enlarged chamber 22, and passage 24, 25.

When the ram 5 encounters the resistance of the workpiece, the valve 13 is opened. With the right-hand end of the cylinder 6 open to exhaust, the preponderating 4pressure on the left-hand end of the piston 15 causes this piston to move to the right and since the reduced body part 11 of the ram has been halted by the workpiece, this `causes the valve face 39 of the valve head 36 to engage the valve seat 23 on the piston 15 as shown in Fig. 2. The pressure from the working pressure line 9 is now effective against the full left-hand end 4of the -ram 5, that is, against both'its reduced ybody part 11 and its piston part 15. Accordingly, the full power of the ram is exerted against the workpiece to deform it into the desired shape.

After the working stroke has been completed, hydraulic uid under pressure is admitted to the return line 12 into the right-hand or return pressure end of the cylinder 6 and the working pressure line is connected to exhaust. The preponderating pressure is now on the right-hand end of the piston and causes this piston to move to the left and since the effective area of the piston 15 exceeds the effective area of the reduced body part 11 of the piston, the piston part 15 is moved relative to the reduced body part 11 so as to bring the face 38 of the valve head 36 into engagement with the valve seat 21 of the piston as shown in Fig. 3. The piston part 15 and reduced body part 11 of the ram 5 then move together as a unit until the ram reaches its full withdrawn position when the ram return fluid pressure from the return line 12 is cut off. With equal pressures on opposite sides of the piston, the helical compression spring 46, being strong enough to overcome the friction between the piston part 15 Vand a cylinder 6, moves the piston 15 to the right to restore the parts to the posi-4 tion shown in Fig. 1 in which the valve head 36 s unseated from the seat 21. The parts are now in the position .originallyassumedand ready for arepetition of thercycle.

From the foregoing, it .will be seen that by effecting the so-called runaround movement of the hydraulic iiuid of a heavy duty press directly through the ram, the necessity for the large piping and controls and for a conventional runaround circuit is avoided.

l claim:

1. A ram for presses or the like, comprising an enclosed cylinder, a ram including a piston part slidingly fitted in said cylinder and said ram also including a body .fixed tto said body part of said ram and having opposite ,axially facing valve faces alternately engageable with said first and second valve seats in response to correspending relative movement of said piston and body parts .of said ram relative to each other.

2. A'hydraulic ram as set forth in claim 1 wherein a reduced neck connects said valve head with said body part of said ram.

3. A hydraulic ram as set forth in claim 1 wherein spring means bias said piston part to a position in which both of said valve faces are `out of contact with said valve seats of said seats.

4. A ram as set forth in claim 3 wherein said spring means includes one spring biasing said piston part toward the end of said cylinder having said opening and another spring biasing said piston part in the opposite direction.

5, A ram as set forth in claim 4 wherein said one spring is strong enough to overcome the friction between the piston part and cylinder.

6. A ram as set forth in claim 4 wherein said one spring is stronger than said other spring.

7. A ram asset forth in claim 4 wherein each of said springs is in the form of a helical compression spring.

8. A ram as set forth in claim 1 wherein said passage forms an enlarged central valve chamber in said piston part and said valve seats are at opposite axialV ends of said chamber in opposing relation to each other, and wherein said valve head is arranged in said enlarged chamber, and the connection fixing said head to the corresponding end of said body part as in the form of a reduced neck.

9. A ram as set forth in claim 8 wherein said valve head includes a valve stem projecting axially from said valve head in a direction opposite from the end of said cylinder having said opening, a pair of helical compression springs on said stem in compressive relation with each other, and a member fixed to saidpiston part and interposed between the opposing ends of said helical compresslon springs.

10. A ram as set forth in claim 9 wherein the spring tending to bias said piston part toward the end of said cylinder having said opening is of suicient strength to overcome the friction between the piston part and cylinder and is stronger than the other spring.

References Cited in the file of this patent UNITED STATES PATENTS 523,419 Thorpe July 24, 1894 2,283,124 Peterson et al May 12, 1942 2,335,917 Cuthbert Dec. 7, 1943

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