Title:
Hydraulic press
United States Patent 2190755


Abstract:
This invention relates generally to hydraulic presses and more particularly to an improved arrangement of draw and main rams with which improved filling and distributing valves are combined. In hydraulic ree presses, particularly high speed presses for sheet metal work, it is desirable to...



Inventors:
Dinzl, Richard W.
Application Number:
US12935537A
Publication Date:
02/20/1940
Filing Date:
03/06/1937
Assignee:
BALDWIN LOCOMOTIVE WORKS
Primary Class:
Other Classes:
91/441, 91/446, 91/517
International Classes:
B30B15/16
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Description:

This invention relates generally to hydraulic presses and more particularly to an improved arrangement of draw and main rams with which improved filling and distributing valves are combined.

In hydraulic ree presses, particularly high speed presses for sheet metal work, it is desirable to hae a ve a relatively small ram and cylinder for drawing the sheet metal and to have a relatively large ram and cylinder to effect the final pressing actin rion. Various arrangements have heretofore been suggested and used but the same have involved structural and operating complications and expense, it being understood that these factors are of considerable importance in presses of large capacity where the presses may be of large physical size and ponderous weight.

It is an object of my invention to provide an improved arrangement. of draw and main rams in combination with an improved combined filling and distributing valve mechanism.

Another object is to provide improved control and operating means for the combined filling and distributing valve mechanism especially when 26 the valve mechanism is employed in combination with my improved draw and main ram arrangement.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which: Fig. 1 is a digrammatic elevation of a hydraulic press employing my improvements; Fig. 2 is an enlarged vertical section showing 36 a portion of the cylinder, rams and filling tank together with my improved filling and distributing valve mechanism and its control; Fig. 3 is a fragmentary sectional view of the combined distributing and filling valve shown in an intermediate position during its upward movement.

In the particular embodiment of the invention such as is disclosed herein merely for the purpose of illustrating one specific form among possible others that the invention might take in practice, I have shown in Fig. 1 a conventional type of press having a base or lower platen I suitably supporting an upper crosshead 2 through side columns or tie rods 3. A movable platen 4 is suitably secured to a main ram 5 which is received in a cylinder 6 supported upon the stationary crosshead. The main ram 5 is hollow to receive a stationary draw ram 7 for effecting a draw stroke of relatively low power compared to the final stroke which is effected by the relatively large main ram 5. Combined with the main and draw ram arrangement is an improved combined check and distributing valve mechanism and operating means therefor disposed partially within a filling tank 8 which is suitably supported upon the upper end of main cylinder 6. The main cylinder, Fig. 1, is adapted during a down ram stroke to be supplied from filling tank 8 with low pressure filling fluid through passages and ports 9 and 10, the ports 10 being f6rmed in a structure II formed integral with and depending from a cylinder head 12. Draw ram I is suitably secured to the structure II. The passage 9 is controlled by a filling valve 13 having an upwardly projecting stem 14 slidably supported in the upper end of a pilot cylinder 15 while the e lower end 16 of the valve stem is slidably supported within draw ram 7. The valve has a cylindrical wall 17 adapted to have a relatively close telescopic ft with the lowerwall portion 18 of passage 9 thereby to close this passage during certain periods of operation. The lower side of valve 13 is provid w ed with a reduced circular portion 19 whose lower surface is adapted to seat against the upper end of draw ram 7 to cushion the valve at the end of its lower stroke which is the position shown in Fig. 2. The lower stem 16 is of larger diameter than the upper stem 14 for reasons to be explained later. A passage 20 extends through both stems for communication with a draw ram passage 21 leading to the lower end of the draw ram cylinder 22 while radialports 23 communicate with passage 20. The remaining structure will be readily understood in connection with the description of the mode of operation of the press as a whole.

Operation In the position of the parts as shown in Fig. 2; it can be assumed that the press is held by fluid 40 pressure supplied from a preferably constant speed positive displacement pump 24 through a four way reversing valve 25 and thence through a pipe 26 to a pullback mechanism 27. Simultaneously pump fluid is supplied, Fig. 1, to a ,45 port 28 which is now closed by a pilot piston 29 held in its lowermost position in a manner to be described later. To start the press down, reversing valve 25 is shifted to the left to connect pullback cylinders to the suction side 30 of pump 24 as through pipe 26a, ports 25a and b and valve passage 25c. Simultaneously fluid pressure from the upper end of pilot cylinder 31 is discharged through a check valve 32 and a pipe 26b to the pump suction preparatory to a subsequent closing 66 operation of the filling valve. The main ram an platen now descends by gravity during whic time fluid from the filling tank flows freel through passages 9 and 10 to the main cylinde 6 and through a second filling check valve 31 to the draw cylinder, the rate of downward move ment being governed by the rate of. discharge c fluid from the pullback cylinders. Simultaneous ly with this down movement, pump 24 supplie fluid pressure through reversing valve ports 25, and e to pipe 33 and thence. through passages 2 and 21 to the draw ram cylinder 22. Upon con tact of the die with the sheet material or othe work piece, a relatively low force will be createc in draw cylinder 22 to close filling valve 31' an( move the main ram and platen 4 downwardly t4 effect a draw stroke. The resistance to the drav stroke gradually increases as the drawing opera. tion nears completion, thereby causing pumi pressure to increase. The increased pump pres. sure acts upon the lower end of valve stem II and when the pressure reaches a predetermined value, it overcomes the action of a spring 35 and also the pump pressure acting on the upper end of thesmaller diameter stem 14, thereby to raise the movable valve structure 13. As shown in Fg. 2, the cylindrical valve portion 1'7 enters passage 18 before ports 23 move out of the upper end of the draw ram 7. Flow of filling fluid, to the main cylinder is thereby discontinued and upon further upward movement of the valve structure, ports 23 are uncovered to supply pump pressure through passage 20, ports 23 and 10 to the main cylinder to increase the pressure therein. This increased. main cylinder pressure Immediately acts.upon the under side of valve 13 to move the same to its full closed position against the combined force of the relatively low liquid pressure in filling tank 8, the spring 35 and the Pump pressure on the top of valve stem 14. The main ram is thereupon moved downwardly under full pump pressure acting thereon and also under full pump pressure acting within the draw ram cylinder 22 to effect the final press operation. During the foregoing down stroke, pressure fluid is supplied from filling tank 8 through pipe 30a to pump suction pipe 30.

To reverse the press, valve 25 is moved so as to connect the pump discharge pipe 37 to pipes 26 and 26b but full pump pressure cannot build up in the pullback cylinders 27 because pipe 26b is in communication with an annular recess 39 in the now raised pilot piston 29, the recess in turn comn municating with a bleed or bypass port .40 leading to filling tank 8. The pump pressure is thereby maintained at a predetermined low value. This low pump pressure is transmitted from recess 39 upwardly through ports 41 to the upper end of pilot cylinder 15 which pressure together with spring 35 is sufficient to move valve 13 downwardly to open the same. When valve 25 Is first moved to its reversing position, the main cylinder 6 is initially subjected to the pump suction pressure through ports 23, passage 20 and pipe 33, 85 although due to the large volume of displaced fluid from the main cylinder on the up stroke the pump suction cannot handle it entirely. Also, by maintaining a relatively low pump pressure in the pullback cylinders, the upward force exerted thereby on the main ram as through platen 4, will not create a large pressure in the main cylinder.

Hence the filling valve can readily open against this small main cylinder pressure. As the filling valve moves down, it finally approaches the upper end of draw ram 7, but the flat valve shoulder ,d surface 19 will trap sufficient liquid to provide a h cushioning effect as this liquid is laterally y squeezed out between the surfaces. This cushionxr ing effect is supplemented by having annular pasI' sage 39 gradually cut off port 28, thereby re!- tarding flow of actuating fluid to the upper end if of pilot cylinder 15. When port 28 is fully cut - off so that bleed port 40 is no longer effective, s it is seen that pump pressure can build up to any d amount necessary to raise the pullback mecha0 nism together with the platen and main ram.

From the foregoing disclosure it is seen that I r have provided not only a relatively simple, comI pact and effective draw and main ram arrangeI ment but have also provided a combined dis> tributing and filling check valve adapted to be r brought into complete structural and functional cooperation with my improved ram arP rangement in such a manner as to reduce the cost - of construction, while still retaining positiveness of operation together with the necessary degree of sensitivity of the operating parts to insure maximum speed. While the general type of pilot cylI inder and piston disclosed herein constit(tes the subject matter of a separate application (Serial No. 128,998) of mine, yet this improved pilot structure Is particularly useful for operating the combined distributing and check valve disclosed herein although it will of course be understood that other types of pilot structure may be employed to operate this improved valve together with controlling the fluid pressure in the main and draw ram cylinders.

It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim: 1. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, movable means having a passage therein for initially supplying operating fluid to said draw cylinder, and means for thereafter simultaneously supplying operating fluid through the passage in said movable means to said draw and main cylinders.

2. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram forming a ,draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a fluid passage within said draw ram for conducting operating fluid to the draw cylinder, a movable element provided with a passage internally thereof and having coaxial telescopic engagement with said draw ram and communicating with said fluid passage, and means providing a port controlled by relative slidable movement between said passage element and draw ram for supplying operating fluid to said main cylinder.

3. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a fluid passage within said draw ram for conducting operating fluid to the draw cylinder, a movable element provided with a passage and having telescopic engagement with said draw ram and communicating with said fluid passage, radial ports in said passage element communicating with the passage therein, and 5- means associated with said.draw ram for controlling the opening and closing of said radial ports upon movement of said passage element whereby operating fluid is adapted to be supplied solely to the draw ram cylinder when said passage element is in its fully telescoped position with the draw ram and is adapted to supply operating fluid to said main cylinder when the passage element is moved outwardly to uncover the radial ports.

4. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and suported by the outer end of said main cylinder, a fluid passage within said draw ram for conducting operating fluid to the draw cylinder, a movable element provided with a passage and having telescopic engagement with said draw ram and communicating with said fluid passage and adapted when in a certain position to have communication with the main cylinder, and means associated with the upper end of said draw ram for cooperation with said passage element to prevent said communication with the main cylinder when the passage element is in full telescopic relation with the draw ram thereby to supply operating fluid solely to the draw cylinder, said passage element having communication with said main cylinder upon outward movement of 33 said passage element thereby to supply operating fluid simultaneously to both the draw and main cylinders.

5. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a filling tank, an element having a passage leading therefrom to said main cylinder, a combined distributing and filling check valve comprising a single movable element with a passage internally thereof for controlling said filling passage and sequentially supplying operating fluid through said internal passage to said draw cylinder and then to the main cylinder.

6. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a filling tank, a communicating passage between said tank and main cylinder, a filling Go valve adapted to be telescopically received in said communicating passage, a distributing valve operatively associated with said filling valve and adapted to supply operating fluid solely to said draw cylinder when said filling valve is either open or partially closed and to supply operating fluid to the main cylinder when the filling valve is fully closed, means for moving said filling valve into an initial telescopic relation with said communicating passage, and means whereby an additional closing force is imparted to said filling valve after said initial telescopic relation is effected.

7. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a filling tank, a communicating passage between said tank and main cylinder, a filling valve formed as an integral part of said element for sequentially distributing operating fluid through said supply passage first to said draw cylinder and then through said supply passage to said main cylinder, means for operating said distributing and filling valves so as to close said communicating passage when operating fluid is supplied to the main cylinder, pullback mechanism, means for supplying operating fluid to said pullback mechanism upon completion of a pressing operation, actuating means for opening said filling valve, and means for maintaining the pullback operating pressure below a predetermined value until said filling valve is open and thereafter permitting pullback pressure to build up to return the press to its initial position.

8. A hydraulic press for effecting draw and final pressing operations comprising, in combination, a main cylinder, a hollow main ram having a draw cylinder internally thereof, a stationary draw ram disposed within said draw cylinder and supported by the outer end of said main cylinder, a filling tank, a communicating passage between said tank and main cylinder, a filling valve for controlling said communicating passage, a distributing valve for controlling supply of operating fluid to said draw and main cylinders, means for operating said distributing and filling valves so as to close said communicating, passage when operat- n ing fluid is supplied to the main cylinder, pullback mechanism, means for supplying operating fluid to said pullback mechanism upon completion of a pressing operation, actuating means for opening said filling valve, means for maintaining said pullback operating pressure below a predetermined value while said filling valve is being opened, and means for retarding opening movement of said filling valve and simultaneously permitting pullback pressure to build up to return the press to its initial position. 60 9. A hydraulic press for effecting draw and final pressing operations comprising, in combination, main and draw cylinders, rams disposed in said cylinders, means for initially supplying operating fluid to said draw cylinder and for subsequently supplying operating fluid to said main cylinder including a filling tank, a filling fluid passage through which fluid is supplied from said tank to said main cylinder to supply low pressure filling fluid thereto, an operating pressure fluid supply passage, and a unitary element having a filling check valve for controlling said filling fluid passage and having means controlling distribution of operating fluid through said supply passage to said main cylinder and draw cylinder, said operating fluid supply passage being formed in said unitary element.

RICHARD W. DINZL.

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