US2187371A - Prefill valve for hydraulic presses - Google Patents

Description

Jam. 16, 1940. CANNON 2,187,371

PREFILL VALVE FOR HYDRAULIC PRESSES Filed Nov. 20, 1936 INVENTOR "Ev 0% wapg I] ATTORNEY Jan; 16, 1940 PREFILL VALVE FQR HYDRAULIC PRESSES Earl Cannon, Rockville Centre, N. Y., assignor to E. W. Bliss Company, Brooklyn, N. Y.,-a corporation of Delaware Application November 20, 1936, Serial No. 111,790

9 Claims. (Cl. 121-38) This invention relates to improvements in prefill valves (otherwise known as surge valves) which are employed for permitting the rapid filling and exhaustion of the ram work chamber of valves to effect a controlled exhaustion of the ram work chamber and thus eliminate shock. With this arrangement, extra piping was needed, yet this disadvantage was outweighed by the a hydraulic press with oil or other fluid during several advantages of the valve over the springthe operation thereof. closing type of valve.

The initial filling of the ram work chamber, The principal object of the present invention prior to the establishment of a relatively high is the provision of means in a spring-opening working pressure therein, ordinarily takes place type of prefill valve for alleviating or minimizing m as a result of suction which is set up in said any objectionable shock of the character heretochamber by the advance of the ram to a point fore referred to, without, however, employing an where it initially engages the material being additional piping to achieve such result. processed, various expedients being available for This object and certain advantages which reachieving such advance of the. ram. To that sult from the attainment thereof are achieved my end, auxiliary hydraulic rams may, for example, by my invention as described in the following be arranged to coact with opposite sides of the specification and shown, for illustrative purposes platen or die carried at the outer end of the ram only, in the accompanying drawing, in which: of a hydraulic press, or suitable means may be Figure 1 is a vertical substantially diametrical directly combined with the prefill valve and the section of a prefill valve employing a preferred W working ram of a hydraulic press in a manner embodiment of my invention. clearly described and illustrated in Patent No. Fig. 2 is a fractional section, similar to Fig. 1, 2,127,324, issued upon my co-pending application, illustrating another embodiment of my invention. Serial No. 105,005, filed October 10, 1936. The Fig. 3 is an elevational view of the under side present invention, however, does not depend upon of the valve illustrated in Fig. 2.

m the means employed for advancing the ram. Figs. 4a, 5 and 6, are details of still further emlPrefiIl valves may either be normally held bodiments of my invention. closed by tensioned. springs, under which ar- The invention, as illustrated in Fig. 1, is emrarigement the flow of fluid past such a valve bodied in a prefill valve comprising a closed-top must work against the tension of the spring, or valve casing II, and a ram chamber casing 12 m they may beheld normally open by tensioned held together by bolts l3 (only one being shown),

springs, under which latter arrangement the flow the casing M havi a b l4 into which 5 Valve of fluid is substantially unimpeded by the action element i5 is accurately fitted and adapted to of the valve as controlled by the spring tension. axially slide therewithin between a lowermost or For this, and other reasons, the latter arrangeclosed position and an uppermost or open posiment is generally preferred. tion, as indicated respectively in full and broken Where, however, prefill valves are arranged to lines in the drawing, and the casing l2 having a be held normally open by spring tension, a very bore I6, preferably in axial alignment with the objectionable and detrimental shock may be en bore l4 but being somewhat smaller in diameter countered when the valve is opened upon the than the latter, said bore forming a ram chamber w return stroke of the ram. This shock is ap- I6a. A ram I1 is accurately fitted into and 40 parently caused by the practically instantaneous a ap ed o S d t n S ram c release of the high working pressure from within The interior space above the valve element the ram work chamber at the instant of the (said space being hereinafter referred to as a opening of the prefill valve. Spring-opening prevalve-closing chamber Ma) varies in size with fill valves, heretofore developed, are so designed the movement of the valve element l5 between 45 that a relatively slight opening movement thereits extreme positions. A port Mb in the top of of suflices to completely and instantaneously rethe casing II is provided for the introduction lease the high working pressure and,.hence, to of fluid under pressure into said valve-closing suddenly release the structural stresses normally chamber and also serves for'the exhaustion of w encountered in the operation of the press. The said chamber. sudden release of such structural stresses sub- The bore M in the valve casing is enlarged at jects the press to shock and; strains which are its lower end to form an annular surge chamber detrimental to the press structure. H! which may be connected by a pipe 19 to a Independent exhaust ports have heretofore tank or other suitable container holding a supply been successfully employed with spring-opening of fluid for use in operating the press; such con- 55 tainer, however, not being shown in the drawing as such a showing is not necessary for an understanding of the invention.

The valve element I5 is provided with an interior passage 20 which extends axially and preferably concentrically from the outer or upper end of said element to the inner or lower end thereof. The said passage is normally closed by a check valve 2| having a stem 22 extending through openings in lower and upper perforate webs 23 and 24, respectively, within the valve element 5. The said check valve normally seats upon the under side of the web 23 in position tov close the perforations in the latter and, hence, to eifect'closure of the passage 20. The check valve is normally held in its uppermost or closed position, as shown in the drawing, by a compression spring 25 which is disposed about the stem 22. Said spring seats at its lower end against the web 23 and at its upper end against a bushing 26 which is accurately fitted to slide within the web 24 and extends upwardly therefrom and is held upon the said stem by locking nuts 21 screwed onto a threaded upper end portion 28 thereof.

The mounting of the check valve upon the two webs 23 and 24 serves to maintain the valve 2| in proper alignment and thebushing 26 serves to transmit the force of the spring 25 to a point above the upper web 24 where it acts upon the nuts 21 to normally hold the check valve closed. The disposition of said nuts above. the web 24 renders them easily accessible for adjusting the tension of the spring 25, the threaded portion 28, for this purpose, being of sufficient length to permit any desired range of adjustment.

The downward movement of the valve element i5 is limited by its engagement with an annular valve seat member 29 which is fitted tightly within the upperend of the bore IS in the ram chamber casing. Coacting oblique seating surfaces Ilia and 29a are provided on the valve element l5 and the valve seat member 29, respectively, and coacting vertical seating surfaces I51) and 29b are provided on said valve element and valve seat member respectively, all said seating surfaces contributing to aiford a substantially tight seal against the passage of fluid when the valve is closed. It is to be understood, of course, that the seating surfaces 29a and 29b may, if desired, be formed directly upon the casing l2, thus eliminating the valve seat member 29 as a separate member. The illustrated construction is preferred, however, as it permits the ready and economical replacement of worn seating surfaces.

A compression spring 30 is disposed about a reduced lower portion of the valve element l5, and seats, at its lower end, against the valve seat member 29, and at its upper end, against a shoulder 3| on said valve element whereby to normally hold the latter in its uppermost or open position. A plurality of grooves 32 of various lengths are provided in the lower part of the valve element l5. These grooves are disposed about and interrupt the vertical seating surface |5b of the valveelement and extend, preferably vertically, from the lower edge of said seating surface to points thereon which are at various distances from the upper limit thereof. The said disposition is such that each groove is matched by a diametrically opposite groove of a similar size, whereby to maintain a balance in the effect of said grooves in the operation of the valve. It will be seen that, as the valve element l5 risesto open, the oblique seating surfaces I51: and 29a become instantly disengaged over their entire areas and the longer grooves 32 and then the shorter grooves 32, in succession, extend beyond the upper edge of the vertical seating surface 29b of the valve seat member, thus establishing a relatively gradual progressive fluid communication between-the fluid inside the ram chamber and the fluid in the surge chamber l8 and permitting a relatively gradual release of the high working pressure existing in the ram chamber. Although the opening of the valve, in the practical operation of the press, takes place in a fraction of a second, the grooves 32 may nevertheless be so proportioned and arranged that the fluid pressure in the ram chamber |6a may be sufliciently reduced to substantially alleviate and minimize any objectionable shock, before the relatively sliding seating surfaces l5a and 29a become completely disengaged upon the opening of the valve.

The cycle of operation commences with ram H in its uppermost position, as indicated in the drawing, the valve element IS in a raised or open position, as indicated in broken lines, the check valve 2| closed and with fluid under substantially atmospheric pressure in the ram chamber Ifia, the surge chamber l8, and in the valve closing chamber Ma. The ram l I is caused to descend by any suitable means, as, for example, by separate hydraulically operated rams (not shown) which may operate directly upon the platen or die normally attached to the lower end of the ram H. The descent of the ram causes fluid to be drawn or sucked through the pipe l9 into the surge chamber l8 and thence past the raised valve element I 5 into the ram cylinder [6a.

Fluid is then admitted under relatively high pressure through the port Mb into the valveclosing chamber Ha. causing the valve element I5 to descend to a closed position. The continued introduction of pressure through the port Mb sets up pressure ,in the valve-closing chamber sufficient to open the check valve 2| against the tension of the spring 25, thus establishing fluid communication between the valve-closing chamber Ma and the ram chamber [6a and permitting the introduction of a suitable working pressure into the latter chamber. The pressure thus introduced into said ram chamber through the port Mb may be raised to the extent necessary to cause the ram to fully perform its desired work.

It will be seen that after the check valve 2| opens, a substantially uniform fluid pressure is present in both the valve-closing chamber a and the ram chamber Ilia. As the effective upper surface of the valve element l5 which is subjected to downward pressure is of greater area than. the effective lower surface thereof which is subjected to upward pressure, it is obvious that there is a predominant downward force exerted upon the valve element l5 which operates to hold said element in a closed position while working pressure is maintained in the ram chamber, it being apparent that the excess downward force must be suflicient to overcome, in addition, the expansive force of the spring 30.

The return stroke of the ram is accomplished by simultaneously releasing the pressure in the valve-closing chamber Ha through the port *IIb and raising the ram by any suitable means which may be the same or similar means as were used to efiect the descent of the ram on the down stroke. The release of the pressure in the valveclosing chamber permits the exhaustion of said chamber through the port I4b,'which exhaustion takes place as the valve element liis forcedfiupill iii

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wardly toward its open position by the expansive force of the spring 30 and by the raising of the ram.

The valve element l5, at the commencement of the return stroke of the ram, first becomes unseated at the oblique seating surfaces Ilia and 29a, while the vertical seating surfaces I51; and 2% remain in substantially coacting relationship, but as the valve element l5 continues its upward movement and while said coacting relationship continues, the several grooves 32, in succession, establish a relatively gradual progressively increasing fluid communication between the ram chamber. Mia and the surge chamber I8 and, hence, a gradual release of the working pressure in the ram work chamber, thus preventing any detrimental sudden release of structural stresses. First the longer of said grooves becomes effective in the manner stated, and then the shorter of said grooves, the communication between the two said chambers becoming progressively greater as the upward movement of the valve element continues until the seating surfaces I51) and 29?) become completely disengaged, whereupon there is a substantially complete communication between the ram chamber and the surge chamber. Although the opening of the valve and the return strolre of the ram is substantially instantaneous in practice, nevertheless the grooves 32, as hereinbefore stated, may .be proportioned to gradually, but quickly, release the working pressure and thus eliminate objectionable shock.

While the embodiment of Fig. 1 provides vertical seating surfaces which are below the oblique seating surfaces, the said relative positions thereof may be reversed if desired, as illustrated in Fig. 2. The embodiment illustrated in the latter figure includes a packing ring 33 having a vertical seating surface 33b coacting with the lower portion of the outer vertical wall of the valve element it, which portion serves as a vertical seating surface and has a plurality of grooves 32 of various lengths extending upwardly from the lower edge of said vertical wall, the longer-of said grooves extending to a point on said wall which, when the valve is completely closed, is just below the top surface of the packing ring 33; In this modification, the grooves 32 operate similarly to those employed in the modification of Fig. 1. As the valve element i5 is raised, the oblique seating surfaces first become disengaged, and then grooves 32 in succession establish communication between the ram chamber and the surge chamber.

The embodiment illustrated in Fig. 4 functions similarly to that illustrated in Fig. 1 but differs train the latter structurally in that no grooves such as grooves 32, are employed, but an outer surface it, referred to hereinafter and in the appended claims, as a seating surface, is provided to coact with the vertical seating surface 28b of the valve seat 28 to permit a relatively gradual establishment of fluid communication between ram chamber its and surge chamber l8. The seating surface 34, as illustrated herein, is angularly disposed relatively to'the seating surface itb, being slightly spaced from the latter at its lower end and entering into engagement therewith at its upper end. The principle employed in this. modification is similar to that employed in the other modifications. As the valve element it moves upwardly to an open position, the oblique seating surfaces first become completely disengaged, whereupon there is first established a restricted communication between the ram and surge chambers-which communication, because of the angular relationship of the seating surfaces 34 and 29b, becomes progressively greater as the valve opens and permits a substantial reduction of the pressure in the ram work chamber before the coaction between the seating surfaces 34 and 29b ceases.

Fig. 5 illustrates a further embodiment of the invention, which differs from the embodiment of Fig. 1 only in that grooves 35 are provided in the vertical seating surface 29b of the valve seat member instead of the grooves 32 in the vertical seating surface i517 of the valve element. 0bviously, if the valve seat member 29, as a'separate element, were to be omitted, as hereinbefore suggested, the grooves 35 could be formed in the upper portion of the bore i6. It may also be desirable, under some circumstances, to provide grooves in both the valve element and the valve seat member.

The embodiment of Fig. 6 employs the principle of angularly disposed coacting seating surfaces similarly to Fig. 4, but an angular seating surface 36 is provided upon the packing ring 33 instead of on the valve element l5.

In the following claims the expression cut away portion" or the limitation that a surface or portion is "cut away" are not used to define the method by which such portion or surface is formed but to define a structural characteristic or form of such portion or surface.

It will be apparent from the foregoing that my invention as described herein and illustrated in the accompanying drawings, solely for illustrative purposes, may be employed in various structures and in various modiflcations'of the seating surfaces without, however, departing from the spirit of the invention as defined in the following claims.

What-l claim is:

l. A hydraulic press or the like and a prefill valve therefor, comprising a ram chamber having a port for the filling and exhaustion thereof, means for conducting fluid at relatively low pressure to andfrom said port and a reciprocating valve element coacting with said port whereby to close the latter and retain fluid at relatively high working pressure in said ram chamber, said valve element and port having coacting surfaces one of which is substantially parallel to the line of movement of the valve element and another of which, at one extreme position of the valve element is adapted to coact with said substantially parallel surface whereby to substantially close said port, and has a progressively cut away portion which, during movement of the valve element from said extreme position, forms with the said parallel surface, a progressively enlarging means for passing fluid through said port.

2. In a prefill valve for hydraulic presses or the like having a ram chamber, a port to said chamber for passing fluid thereinto and a movable valve element adapted to close said port, means for establishing a relatively gradual increasein the passage of fluid through said port during the opening movement of/said valve, said means comprising a pair of coacting oblique seating surfaces on the valve element and about the port, said surfaces being disposed obliquely relatively to the line of movement of said valve element, and a second pairof seating surfaces on said element and about said port, one seating surface of said second pair being disposed substantially parallel to the line of movement of said valve element, the said second pair of surfacesbeing adapted to coact in varying degrees to eifect a relatively adapted to successively become operative as fluid passages with the movement of the valve element.

4. A hydraulic press or the like and a prefill valve therefor, according to claim 1, the said cut away portion comprising a plurality of grooves in the valve element adapted to successively become operative as fluid passages with the movement of the valve element.

5. A hydraulic press or the like and a prefill valve therefor, according to claim 1, the said cut away portion comprising a plurality of grooves, in the said surface of the port, adapted to successively become operative as fluid passages with the movement of the valve element.

6. A hydraulic press or the like and a prefill valve therefor, according to claim 1, the said cut away portion being cut away angularly to the said parallel surface, whereby to provide various-sized passages between said surfaces when the latter are disposed in various relative positions.

7. A hydraulic press or the like and a prefill valve therefor, according to claim 1, the said cut away portion being on the valve element and being cut away angularly to a coacting portion of the surface of the port, whereby to provide various-sized passages between said surfaces when the latter are disposed in various relative positions.

8. In a prefill valve for hydraulic presses or the like having a ram chamber, a port to said ram chamber for passing fluid thereinto, and a movable valve element adapted to close said port, means for restricting the passage of fluid through said port during the opening movement of the valve element, said means comprising coacting seating portions disposed on said element and about said port, and coacting surfaces disposed on said element and about said port, one of said surfaces having spaced-apart portions comprising a plurality of grooves of various lengths adapted to successively establish fluid communication through said port during the opening movement of the valve element.

9. In a prefill valve for hydraulic presses or the like having a ram chamber, a port to said ram chamber for passing fluid thereinto, and a movable valve element adapted to close said port, means for restricting the passage of fluid through said port during the opening movement of the valve element, said means comprising coacting seating portions disposed on said element and about said port, and coacting surfaces disposed on said element and about said port, one of the said coacting surfaces being disposed angularly relatively to the other whereby to afford a gradually increasing fluid communication through said portduring the opening movement of the valve element.

EARL CANNON.

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