US2774217A - Thrust-producing apparatus such as presses and the like - Google Patents

Description

Dec. 18, 1956 P. E. ASHTON 2,774,217

THRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THE LIKE Filed July 5 1950 3 Sheets-Sheet 2 INVENTOR Pm lzblilfskton.

M ATTORNEY Dec. 18, 1956 Filed July 5. 1950 P. E. ASHTON THRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THE LIKE 3 Sheets-Sheet 3 United States Patent THRUST-PRODUCING APPARATUS SUCH AS PRESSES AND THE LIKE Philip E. Ashton, Meriden, Conn. Application July 5, 1950, Serial No. 172,159 26 Claims. (Cl. 6054.5)

This invention relates to thrust-producing mechanisms, for instance presses and the like, in which thrust is exerted on a piece of work by a ram; and it relates more particularly to presses in which both a mechanical linkage and hydraulic thrust-multiplying means are utilized to provide great mechanical advantage.

An object of the invention is the provision of a thrustproducing device which will attain high working pressures and may be adapted for use in conveniently small machines such as hand-operated presses.

Another object is to provide a thrust-producing device which, during an initial stage, provides a relatively large movement of the thrust member under a comparatively low thrust, and which may be quickly shifted, without reducing the thrust, to succeeding stages for producing a multiplied thrust.

A further object is the provision of sturdy, simple and reliable means for controlling the change from one stage of ope-ration to a successive stage. i

A thrust-producing device embodying the principles of the invention has a plurality of cooperating and interrelated thrust-imparting means, each operable to apply thrust to a thrust member which acts upon the work, one of said thrust-imparting means being actuated by reaction from the thrust of another of said thrust-imparting means upon said thrust member. This may be carried forward into one or more succeeding thrust-multiplying means, although in practice the desired result is ordinarily attainable with two such means. The first means is poweroperable to transmit the power supplied, for instance, by a motor or by hand to the thrust member, which in presses is usually a ram. Such power-transmission means or a portion thereof is adapted to move due to reaction of the thrust imparted by it to the thrust member. The second thrust-imparting means, having a primary element connected to the transmission means and a multiplied thrust element connected to the thrust member, is actuated by movement of said transmission means to produce a multiplied thrust on the thrust member. A frame supports, either directly or indirectly, all the operating elements of the device.

An important feature of the invention is the provision of releasable restraining means operable to hold the powertransmission mechanism against substantial movement relative to the frame of the device. This, when functioning, restricts the action of the transmission means to imparting thrust directly to the ram and renders the thrust-multiplying means inoperative. Furthermore, the restraining means may desirably be automatically operable under a predeterminable load to release the transmission means for movement which, in turn, brings the thrustmultiplying means into operation so that both means operate concurrently.

One particularly desirable embodiment of the invention consists of a press having a ram moved only by mechanical linkage until a desired resistance is met by the ram, whereupon a hydraulic thrust-multiplying means is brought into operation to apply a multiplied thrust to the ram.

An important advantage provided by such a press is that a thrust on the order of five to ten tons or more can be produced by a convenient, small, compact and relatively inexpensive device. Furthermore, in such a press, the ram can be moved rapidly under no load or under loads within the limit of the mechanical linkage. Moreover, when the press is used, for instance, for metal piercing with a punch and die or for opening some types of molds used in molding plastics, the ram can --be positively and quickly retracted from the work by operating the mechanical linkage in the reverse direction.

The releasable restraining mechanism which, in its most desirable form, in responsive to thrust on the ram, can have a lever control alfording the choice of two ram thrust values, at which the change from one stage of operation to another may take place. One of these settings permits the change at a low ram thrust value and is useful in metal piercing and similar operations where both stages of mechanical advantage are needed as soon as the ram, or a tool mounted therein contacts a work piece. The other setting brings about the change at a relatively high ram thrust value and is of considerable value in cases where a press is used to force two pieces together, such as pressing a bushing into a hole, where it is desirable to feel the start of the assembly. This second setting is also of value in using the device in injection molding where a long, rapid stroke at moderate pressure is needed to inject material into the mold, and then a short, high-pressure stroke is required to force the material into all the details of the mold. For instance, in the first setting the change may take place at about lb. ram thrust, cal-ling for very little effort on the part of the operator and being sufiicient to place a piercing punch in intimate contact with a piece of metal that will require four or five tons of ram thrust to pierce it. The second setting would be used where 800 or 1000 lb. of ram thrust is required over a distance of one or two inches to fill a mold or to compact molding powder already placed in a mold, and where thereafter a short stroke of A to /2 inch is needed at a high ram thrust of four or five tons to fill all details in a mold or to effect a final compacting of a molding powder, such as phenolic resin.

For other applications, however, the restraining mechanism may be made to operate manually so that when the desired thrust is attained in the first stage, a lever on the restraining means is moved by the operator to change from simple to compound operation of the press.

Although a thrust-producing device embodying the principles of the invention is most desirably provided with restraining means which permit either simple or compound operation, a device without the restraining means is also within the scope of the invention.

The foregoing and other objects of the invention as well as novel features and advantages, will become further apparent from the specific description hereinafter.

Apparatus embodying the invention is illustrated in the accompanying drawings, in which Fig. 1 is a perspective view, partly in section and partly broken away, of a small manually operated press embodying the invention;

Fig. 2 is a plan view of the same with the housing cover removed;

Fig. 3 is a vertical section on the line 33 of Fig. 2;

Fig. 4 is an enlarged detail view of a control valve;

Fig; 5 is a cross-sectional view showing a mechanical latch type of releasable restraining means and part of the gear-carrier and taken on the line 55 of Fig. 3;

Fig. 6 is an elevation of the latch mechanism looking in the same direction as Fig. 5;

Fig. 7 is an end view of the latch shown in Fig. 6;

Fig. 8 is a detail of parts of the mechanical latch shown in another position of operation;

Fig. 9 is a section of part of a modified cylinder head showing another arrangement of the hydraulic valve mechanism;

Fig. 10 is a plan view, having certain parts removed, of another modified cylinder head incorporating a hydraulically operated device serving the same purpose as the mechanical latch shown in Figs. -8;

Fig. 11 is a cross-section view on the line 11-11 of Fig. and

Fig. 12 is an elevation looking in the direction 12-12 indicated in Fig. 10.

In the specific embodiment of the invention shown in the drawings, 16 is the base on which work may be performed, and upright members 11 and 12, rigidly mounted on base 10, support brackets 13 and 14 securely bolted or welded thereto. This structure forms the frame in which work is done by the thrust-producing mechanism. Shroud 15, which is secured to brackets 13 and 14, encloses the lower portion of the thrust mechanism, and strengthens the frame to help prevent bending thereof. Cylinder housing 16, provided with a cover 17, is securely mounted on bracket 14 in such manner as to be capable of transmitting the full reaction from thrust exerted by the ram to the frame of the press.

Ram 18, protruding through and guided by the bracket 13, may move vertically toward and away from base 10. The lower end of the ram may be adapted in any of several well known ways to carry such tools as are required. For instance, one way (not shown) is to bore a hole coaxially in the ram to house a tool shank which may be clamped in place by a set screw threaded into a transverse hole in the ram.

The ram passes through gear-carrier 19, which is slidable thereon and also on guide rod 20 rigidly supported at its ends by the brackets 13 and 14 and having its axis parallel with that of the ram. Gear shaft 21, having gear 22 at one end and star wheel 23 at the otherend, is rotatably supported in gear-carrier boss 24, which protrudes through an elongated opening 25 in shroud 15. The star wheel, gear shaft and gear are rigidly secured together so that torque may be transmitted from the star wheel to the gear, the gear teeth 26 engaging the teeth 27 of ram 18. v

Upon rotation of star wheel 23 in the direction indicated by the arrow shown in Fig. l, the gear-carrier 19 will tend to move upward along ram 18 and the carrier guide 20. In order to prevent any substantial amount of movement between the gear-carrier and the frame of the press, so that the gear 22 can exert a mechanical thrust on the ram 18 in a manner similar to an ordinary mechanical arbor press, gear-carrier 19 is provided with an extension or tongue 28 projecting from its underside and adapted to be held by latching means, hereinafter more fully described, mounted on the frame of the press. Tongue 28 passes through an opening 29 (Figs. 3 and 5) in bracket 13 and is provided at its lower end with a hard- "ened steel latch plate 30 having beveled latching faces 31. A pair of hardened steel latch blocks 32 having faces adapted to engage the faces 31 of latch plate 30, are carried on pins 33 (Fig. 5) and are free to turn thereon. Because the blocks are unbalanced on pins 33, they assume the position shown in Fig. 5 with their under surfaces resting on pins 34 and 35, Pins 33 are mounted in link side plates 36 which are in turn supported by pins 37, free to rotate in bearing blocks 38 which are secured to the underside of bracket 13. Pins 34 and 35 have reduced-diameter end portions 39 and 40 (Fig. 6), respectively, extending through and free to turn in side plates 36. Holes are cross drilled at the mid-portion of pins 34 and 35 to provide support for latch bolt 41, which is permitted to slide lengthwise and to rotate therein for reasons hereinafter explained. Each blo k 32 has a groove 42 cut across the lower portion to clear parts associated with bolt 41. It now becomes readily apparent that so long as latch blocks 32 remain in contact with the faces 31 of latch plate 30, the tongue 28 is locked in the position shown in Figs. 1, 3, 5 or 6, thereby preventing any substantial amount of movement of the gear-carrier 19 relative to the frame of the press.

The bolt 41 is reduced in diameter at one end for a portion of its length, thus forming a shoulder 43 (Figs. 5 and 8). The end of the reduced portion is threaded and carries adjusting nut 44 and compression spring 45 between washers 46 and 47. Washer 47 is adapted to be pressed under the influence of spring 45 either against pin 35 or against the shoulder 43 of bolt 41 as will be more clearly brought out hereinafter. The pressure exerted on washer 47 by spring 45 is adjustable by means of nut 44. In order to maintain a desired minimum space between the lower ends of links 36 and between blocks 32, a sleeve 48, mounted on bolt 41 between pins 34 and 35, is provided as a spacer for this purpose.

The head 49 of bolt 41, having a handle 59 by which the bolt may be rotated, has two pairs of concave faces 51 and 52, each pair being suited for mating engagement with the surface of pin 34. When the pair of faces 51 is engaged with pin 34, as shown in Figs. 5-7 inclusive, the shoulder 43 is located just within pin 35 against which washer 47 is pressed by spring 45, and the lower ends of the two links 36 are held as closely together as spacer 48 will permit. Any movement of the lower ends of the links away from each other will further compress spring 45, which has been pre-compresed by adjustment of nut 44 toward the bolt head. A tension spring 53 (Fig. 6) is attached to the reduced- diameter end portions 39 and 40 of pins 34 and 35 at one end of each and draws the links toward each other. Thus, with faces 51 of bolt head 49 in engagement with pin 34, as shown in Figs. 5 and 6, any effort to spread the links apart will be resisted by both springs 45 and 53.

If, however, bolt head 49 is turned so that faces 52 are in position for engagement with pin 34, the bolt is per mitted to slide longitudinally within pins 34 and 35, and the shoulder 43 will protrude beyond pin 35, as shown in Fig. 8, and is abutted by washer 47 so that the load of spring 45 is removed from the linkage. In this condition any effort to spread the links apart will only be resisted, within ractical limits, by spring 53. Consequently, an upward pull by tongue 28 against latch blocks 32, which is sufficient to spread links 36 against the tension of spring 53, will separate latch blocks 32 enough to release tongue 28 so that gear-carrier 19 is permitted to move relative to the frame of the press.

If desired, however, when the faces 51 of the bolt head 49 are engaged with pin 34, nut 44 may be tightened until spring 45 is substantially solid, in which case the lower ends of the links 36 are unable to spread apart enough to open the latch. On the other hand, if bolt head 49 is now turned so that faces 52 engage pin 34, the latch'will again be permitted to open under a force greater than the tension of spring 53.

Coming now to the second stage or hydraulic thrustmultiplying portion of the press, a pair of cylinders 54 and 55 are located within cylinder housing 16, the larger of these, 54, being the thrust cylinder and the smaller, 55, being the boost cylinder. Ram 18 extends into the thrust cylinder 54 and terminates in a piston 56 having a convenient seal, such as a conventional O-ring. A piston rod 57 has a reduced diameter portion 58, fitting in a hole in gear-carrier 19, and is anchored by a cross pin 59 against withdrawal. Any downward load on rod 57 is transmitted to gear-carrier 19 by the shoulder formed by the reduced diameter portion 58. The upper end of rod 57 has an enlarged diameter portion 60, which forms a piston for the boost cylinder and which also is fitted with a seal, such as an O-ring. The upper ends of the cylinders 54 and 55 are held in closefitting holes in a supporting member 61 secured to housing 16, and their lower ends are located in recesses in bracket 14, which is provided with openings through which ram 18 and piston rod 57 may pass.

The upper ends of the cylinders are a close fit in annular grooves in the cylinder head 62, and are sealed therein against leakage by soft synthetic rubber gaskets 63 and 64. The upper ends of the cylinders are chamfered so that the annular space provided permits some flow of the gasket material inward toward the cylinder bores when the head 62 is forced downward by cylinderhead retaining ring 65, which has screw threaded engagement with the inner wall of housing 16. This construction is clearly shown in Fig. 3, and in the modified forms of the head shown in Figs. 9 and 11. The above described method of sealing the cylinders in the cylinder head removes any need for precise matching of cylinder heights or the depths of the cylinder head grooves, and will seal pressures in excess of 5000 p. s. i. with very slight screw thread loading of ring 65. The space in prevents leakage of fluid from said reservoir.

The cylinder head 62, shown in Figs. 1 and 3, has an unobstructed passage 67 connecting the two cylinder bores so that identical pressure conditions are maintained within the cylinders at all times. Passage 68 is drilled from the outside of housing 16 through the cylinder head to cylinder 54 to provide a suitable connection for a pressure gauge. In the drawings, no gauge is shown, and passage 68 is closed off by a threaded plug. A port 69 is provided in the under face of the cylinder head, and holes 70 aredrilled therefrom to the upper side of the head, forming fluid passage between the reservoir and cylinder 54. A valve 71, guided in a drilling in the cylinder head, is arranged to close port 69 and is urged by spring 72, acting through washer 73 and cotter pin 74, to its closed position. Spring 72 is so proportioned that valve 71 will be opened by suction created by the downward movement of either piston 56 or piston 60. The difliculties commonly encountered in obtaining satisfactory valve seating in hydraulic service are overcome by facing the valve with a semi-rigid material, such as nylon, and shaping this facing so that it has a very narrow surface of initial contact with the mating surface of the cylinder head. This provides a reliable seal at low pressures and, although the shaped face of the seat is flattened at high pressures, it resumes its initial shape when pressure is released. A suitable construction of valve 71 is shown in Fig. 4, where the head of the valve is shaped to afford a groove into which seating ring 75 is snapped. The upper lip of the groove is made only a few thousandths of an inch smaller in diameter than the inside diameter of port 69, in which it is housed when the valve is closed, in order to prevent extrusion of the seating ring between the valve and the wall of port 69, under the influence of high pressure.

A valve leakage supporting member 76 (Figs. 2 and 3), mounted on the cylinder head 62, acts as a bearing for rocking shaft 77, having levers 78 and 79 rigidly attached thereto. Lever 78 is adapted to depress the stem of valve 71 and thereby open the valve when lever 79 is pulled downwardly by pull rod 80 which is movable vertically under the influence of gear-carrier 19, as will be explained hereinafter. The strength of spring 72 is suflicient to close the valve against the otherwise unbalanced weight of the levers. Pull rod 80, having a head 81 at its lower end and an adjusting nut 82 at its upper end, extends downward from lever 79, on which nut 82 rests, through a gland 83 in the cylinder head, through bracket 14 and through a clearance hole in lug 84- (Figs. 1 and 5) of gear-carrier 19; A compression spring 85, restrained between nut 86 and gland nut 87, serves to urge rod 80 upward and to relieve valve spring 72 of the weight of the rod and the friction caused by gland 83.

As is clearly shown in Fig. 5 there is a small gap between latch plate faces 31 and latch blocks 32 when the gear-carrier 19 is at its lowest point. This gap permits a limited upward movement of gear-carrier 19 prior to restraint of such motion by mutual engagement of the latching surfaces. The eflective length of pull rod 80 is adjusted by nut 82 so that, with gear-carrier 19 at its lowest point, lug 84 engaging rod head 81 causes the valve 71 to be held open. When the gear-carrier is moved upward until faces 31 engage their mating faces on blocks 32, the pull rod is also moved upward by spring 85, and this movement is sufficient to permit valve 71 to close.

Having fully described the various parts of one specific embodiment of the invention shown in the drawings, its operation will now be discussed in detail. Assuming that there is no work piece under the ram and that hydraulic fluid fills the cylinders above the pistons and the reservoir to the fluid level indicated approximately by the broken line L in Fig. 3, and also that gear-carrier .19 is'at its lowest point, rotation of the star wheel 23,

in the direction indicated by the arrow in Fig. 1, will cause ram 18 and its piston 56 to descend, and hydraulic fluid will be drawn past valve 71 into the cylinders. Reversal of the star wheel will reverse this action, and fluid will be returned to the reservoir since valve 71 is held open by the valve levers. Should there be suflicient friction between the seal of piston 56 and the wall of the thrust cylinder, or between ram 18 and its support in bracket 13, rotation of the star wheel in the direction shown will first cause gear 22, together with its carrier 19, to climb ram 18 until the mating latch parts 30 and 32 engage each other and arrest this move ment. In this condition valve 71 is free of the influence of pull rod 80, and 71 may close; but, since the valve is subject to opening by suction, descent of the ram will again draw fluid into the cylinders. Reversal of the star wheel will cause the gear-carrier to descend and open the valve by means of pull rod 80, thus permitting fluid to pass upward past the valve as the ram ascends.

Operation with a work piece under the ram will bethe same as above until the ram meets so much resistance to its descent that the upward reaction thrust of the gearcarn'er causes the beveled faces of the latch members 30 and 32 to force links 36 apart against the pressure of spring 53 and, if bolt head 49 is set as shown in Figs. 5-7, also against spring 45. When links 36 are moved far enough apart, blocks 32 become disengaged from faces 31 of latch plate 30. Gear-carrier 19 is then free to move upward along ram 18 and guide-rod 20 under the influence of the reaction of gear 22 on the ram. A reaction thrust will now be transmitted to boost piston 60 which will, in turn, create a pressure on the fluid trapped in the cylinders by the closing of valve 71, which pressure will exert a downward thrust on ram 18 through the piston 56.

The hydraulic thrust on the ram will bear the same relationship to the reaction thrust on piston 60 as does the area of piston 56 to the area of 60, and the distance traveled by 56 relative to the travel ofthe gear-carrier will be in inverse proportion to the above relationship of the piston areas.

It is important to note that, since valve 71 is closed before gear-carrier 19 is released by the restraining means, there is no relaxation of thrust on the ram during the change from simple to compound operation, even though the force which has to be applied to the star wheel 23 to maintain the original thrust on the ram is reduced. This is due to the fact that the fluid trapped in the cylinders 54 and 55 cannot escape and thus prevents any upward movement of the ram.

If the star wheel is then turned in the reverse direction the gear-carrier will descend until it reaches its lowest point and opens valve 71 as hereinabove described. As

and 55 respectively.

7 the gear-carrier approaches its lower position, the latch plate 30 will pass downward between latch blocks 32 and will tilt them, as indicated in Fig. 6 by broken lines, until it clears the lower edges of the blocks, which will then return to their normal position, being turned on their pins 33 by the unbalanced weight of their outer portions. Continued rotation of the star wheel in this same direction raises ram 18 and piston 56, since the gear-carrier 19 has returned to its lowest position and rests on bracket 13 of the press frame. The fluid in cylinder 54 flows back into the reservoir because valve 71 is held open by rod 80 working through the valve linkage 77, 78 and 79. If the tool attached to the lower end of the ram encounters any resistance in being removed or stripped from the work, as will happen for instance, in metal piercing with a punch and die, reverse rotation of the gear will exert a positive upward force on the ram thus quickly and easily extractingthe tool from the work.

From the foregoing description of a hand operated press according to the invention, it is obvious that the mechanical latch mechanism 28-53, although herein above described as operating automatically when a predetermined thrust is exerted on the ram by gear 22, can be readily adjusted for manual operation. This is accomplished, as previously mentioned, by placing bolt head 49 in the position shown in Fig. 5, and tightening nut 44 until spring 45 is substantially solid. The latch is then locked in its closed position, since spring 45 cannot be further compressed to the extent necessary to permit blocks 32 to clear latch plate 30. In order to release the latch, bolt head 49 is rotated 90 to engage faces 52 with pin 34, as shownin Fig. 8-. Since spring 53 is relatively light, it is easily overcome by any substantial pressure on the latch and, under these conditions the latch may be considered, for all practical purposes, as open. Manual operation of the latch is thus accomplished without difliculty whenever desired.

In the device as above described, there is only one valve, and any backward motion of the star wheel will result in a relaxation of the thrust of the ram whether in hydraulic boost action or only in direct mechanical action. This relaxation is not objectionable in many cases, such as when the press is being used for piercing, shearing or bending metal, but in the molding of some plastics it is essential that the press be locked under thrust pressure while the material in the mold is cured. This end may be accomplished by modification of the cylinder head and valve and the addition of other parts as shown in Fig. 9. In this modified form the cylinder head 62a is seated on cylinders 54 and 55 as before described and has a vertical assage 33 leading from the reservoir to boost cylinder 55. The lower portion of this passage is counter-drilled to provide space therein for a conventional ball check valve 89, consisting of a valve ball 90 urged by a spring 91 against a seat 92, all held in place by a retainer cup 93 which is threaded into the enlarged portion of passage 88 and has an opening 94 in its lower end. This intake valve will permit hydraulic fluid to flow from the reservoir to the boost cylinder through passage 8 but it will not permit fluid to thereby return to the reservoir. .A horizontal passage 95 is drilled in the cylinder head and plugged at its outer end. To this passage are drilled vertical passages 96 and Q7, which connect with the bores of cylinders 54. Passage 96 is counter-drilled and provided with a discharge valve 98, which is identical with valve 89 and which permits flow of hydraulic fluid therethrough only from the boost" cylinder the thrust cylinder 54.

The valve operating mechanism, including support member 76, rocking shaft 77, levers 78 and '79 and pull rod 86 is arranged exactly as described in connection with Figs. 2 and 3, but these parts are not shown in Fig. 9 for purposes of clarity.

A valve 100, which is generally similar to valve 71 previously described and which has generally similar functions, is urged to closed position by'a spring 101, acting through washer 102, and a spring retainer ring 103, which is snapped into a circumferential groove 104 in the stem of valve 100. The valve may be opened by suction exactly as in the case of valve 71. Three coaxial drillings are provided axially through valve 100.- The largest diameter drilling forms a valve chamber 105. The intermediate drilling forms a passage 106 connected by cross drillings 107 with the fluid reservoir by Way of port 108 and passages 109 in the cylinder head 62a. The smallest drilling 110 serves to guide a push-rod 111 Within the stem of valve 1%. A valve 112 of similar construction to valves 89 and 98 has a valve ball 113, a valve seat 114 and valve-closing spring 115 maintained in their places by retainer cup 116, which is threaded into chamber 105 and has an opening 117 in its lower end. The valve seats, used in valves 9, 98 and 112, are preferably made of a semi-rigid synthetic material similar to that used for valve seat ring of valve 7L hereinbefore described.

The push-rod 111 slides freely within the stem of valve 100 with its lower end resting on valve ball 113 and its upper end protruding slightly above the valve stem. The valve operating mechanism, comprising shaft 77, levers 78 and 79, and pull-rod are used with this modified construction in the same manner as in the previously describedembodiment, except for the fact that lever 78 contacts push-rod 111 and opens valve 112 before it opens valve 100. 1

In the operation of this modified form of the invention, the unmodified parts of the press function exactly as they did in the first embodiment disclosed. After the gearcarrier 19 has been released by the opening of the latch in the manner hereinabove described, it moves upward 98 into the thrust cylinder 54. Since valves 89,

and 112 are closed, flow of the fluid from the cylinders 54 and 55 into the reservoir is prevented, and downward pressure on the ram is developed. If the star wheel 23 is now released the pressure on the ram will be maintained (assuming that the work under the ram does not permit the ram to move), since valves 98, 100 and 112 are all closed. In this condition the ram is locked. Rotation of the star wheel in the reverse direction causes the boost piston to descend, valve 89 will be opened by suction and a new charge of hydraulic fluid will be drawn into the boost cylinder. Oscillation of the star wheel will cause the boost piston to pump fluid into the thrust cylinder and the ram may be traversed hydraulically for its full stroke by this means, provided that the star'wheel is not turned back far enough to cause the lug 84 on the gear-carrier to engage the head 81 and to force pull-rod 80 downward.

When pull-rod 80 is forced downward the valve opening lever 78 will depress push-rod 111, opening valve 112 before opening valve 100. This is necessary since valve 100, like valve 71, must be large enough to permit the free flow of fluid back to the reservoir when the ram travels upward. Valve 100 is then too large to be opened against the hydraulic pressure on a locked ram,

but valve 112 may be made small enough to be opened readily against high pressure and thus to serve as a pressure spill valve. In a press having a two inch diameter thrust piston and working up to 5000 p. s. i. (7.85 tons thrust on the ram), it has been found that a inch diameter is suitable for port 108 and that inch is suitable for the diameter of the passage through valve seat 114. It is thus possible to spill 5000 p. s. i. pressure from the thrust cylinder with less than 100 lb. load on push-rod 111, whereas over 1500 lb. load would be required to open valve 100 directly against this pressure.

The foregoing description of specific embodiments of the invention has assumed that the mechanical latch illustrated in detail in'Figs. 5-8 is used to change from simple tocompound operation of the press. The invention is obviously not limited to this construction. Inorder to illustrate another practical means which may be substituted for the mechanical latch, Figs. 1012 show a hydraulically operated mechanism, serving the function of the mechanical latch hereinabove disclosed and. oifering certain additional advantages such as low initial cost and greater adaptability to othertypes of framework in which the operative unit may be mounted. Furthermore, the hydraulically operated restraining mechanism is not sensitive to gravity as is the mechanical latch and, for this reason, it will operate with an inverted or horizontal unit without modification. 7

Figs. 10, 11 and 12 show a cylinder head having all of the functions of that shown in Fig. 9, but modified for the incorporation of the hydraulic device which may be substituted for the mechanical latch mechanism shown in Figs. to 8. In a construction employing the hydraulic restraining means, none of the latch parts previously described and having reference numerals 30m 53 inelusive are required; nor are gear-carrier extension 28 and hole 29 in bracket 13 needed. The cylinder head 62b is seated on cylinders 54 and 55 and is retained in housing 16 by ring 65 having gasket 66. This construction also has valves 89, 98, 100 and 112 together with valve control linkage including shaft 77, lever 78, pullrod 80 and push-rod 111 as previously described, but lever 120 is substituted for lever 79 as its shape difrers slightly from that of the latter inorder to accomplish an additional function hereinafter described. The position of valve 180 is indicated in Fig. 10 but has been omitted from Figs. 11 and 12 to clarify them. A vertical passage 121 (Fig. 11) leads from the boost cylinder 55 to passage 122 in valve housing 123 having a cylinder 124 into which passage 122 discharges. The bottom of cylinder 124 has a coaxial opening125 communicating, through passage 126 in cylinder head 62b, with valve' 98 having functions hereinbefore described. The junction of cylinder 124 and opening 125 forms a seat for the valve portion 127 of piston 128 which is slidably supported in the cylinder and has a convenient seal such as an O-ring indicated by 129. A plug 130 serves to seal the open end of passage 122, and resilient gaskets 131 and 132, housed in suitable cavities, seal the junctions. of passages 121 with 122 and 125 with 126 while permitting housing 123 to .be rigidly held in metal to metal contact with cylinder head 62b by means of screws 134 (Figs. 10 and 12). Y

A stud135 is secured to the cylinder head andpasses through a suitable opening in one end of a lever 136. An adjusting nut 137 is threaded .on the stud at its upper end, which protrudes through an opening provided in the cover of the reservoir. A cam block 138 having a handle 139 is rotatably mounted on stud 135 but is not threaded thereon. Notches 140, 141, 142, of varying depth are provided in the under face of camblock 138 and are adapted for individual engagement by a mating projection 143 on the top face of a second cam block 144. Cam block 144 is slidably mounted on stud 135 for vertical motion only and is restrained from turning thereon by key 145, which slides in a keyway in stud 135. A washer 146 is placed between nut 137 and cam block 138 to facilitate independent rotation of these members. A compression spring 147 is located on stud 135 between cam block 144 and the lever 136 which is supported by pin 148 in bearing posts 149 mounted on or integral with housing 123. In Fig. 10,-the cylinder housing cover 17 and spring adjusting members 137 to 145 have been removed in order to show the parts below more clearly in this view. Movement of nut 137 along the stud or varying the position of the projection 143 on cam block 144 in notches 140, 141 and 142 of cam block 138 will decrease or increase the pressure of spring 147 on lever 136 which bears on piston 128, in the manner clearly '10 shownin Fig. l1 and thus presses valve portion 127 on its seat.

The end of lever 136 remote from stud 135 is shaped to provide a latch portion 150 adapted for engagement by catch 151: (best seen in Fig. 12), which is pivoted on pin 152 mounted on housing 123. Catch 151 is urged counter-clockwise, as indicated by an arrow in Fig. 12, by torsion spring 153 having one end engaging pin 154 secured to housing 123, .and the other end bearing on catch 151. Lever 120, which is secured to shaft 77, engages an arm 155 of catch 151 so that depression of 120 will cause the catch to turn against the influence of spring 153 and in a clockwise direction as viewed in Fig. 12, while elevation of 120 will permit the catch to be turned in the opposite direction by the spring 153. If the latch portion 150 of lever 136 is pressed toward the cylinder head, it may be engaged and held by catch 151 until lever 120 is depressed in order that catch 151 will free latch portion 150, thus releasing lever 136 Operation of a press incorporating the device just described is generally similar to the operation of the press as previously set forth except that the upward motion of the gear-carrier will be restrained by fluid trapped in cylinder 55 and passages 121 and 122 between piston 60, valve 127 and piston 12%. Thus, pressure developed on the fluid by reaction thrust, transmitted by gear-carrier 19 to piston 60 will tend to force piston 128 upwards and to open valve 127, thereby permitting the flow of fluid into thrust cylinder 54 via valve 98. Assuming that gearcarrier 19 is at its lowest point, rotation of star wheel 23 in the proper direction will cause ram 18 to descend and fluid will be drawn from the reservoir, past valve 100 and into thrust cylinder 54, valve 100 being held open by pull-rod through lever 120, rocking shaft 77 and lever 78 as previously described. Any resistance to movement of the ram '18 will develop reaction on the gear-carrier, and this reaction will be opposed by fluid trapped in boost cylinder 55. When the reaction becomes sufliciently great, fluid pressure will cause piston 128 to move against the pressure of spring 147 acting through lever 136, and valve 127 will be lifted from its seat permitting some of the fluid under pressure to pass into the cylinder 54. This flow of fluid will permit carrier 19 to rise and release the tension on pull-rod 80, thus allowing valve to close.

Hydraulic pressure will then be imparted to the ram by pressure developed in cylinder 54. Should sufficient hydraulic pressure be maintained, piston 128 will continue to move against the pressure of spring 147 and the latch portion 150 of lever 136 will move toward the cylinder head 62b until it is engaged by catch 151, which at this point is not held by lever 120, due to the fact that pull rod 80 is released by gear carrier 19. Further movement of latch portion 150 is prevented by its contact with the lower face of the notch in catch 151 and lever 136 will be held stationary, thus releasing piston 128 and valve portion 127 from the influence of spring 147 so that the valve portion 127 can offer no further resistance to flow of fluid from cylinder 55 to cylinder 54 even though piston 60 is reciprocated to draw more fluid from the reservoir through valve 89 in order to pump it to cylinder 54. If gear-carrier 19 is returned to its lowest point, it will cause pull-rod 80 to descend and depress lever 120. As a result, valve 100 will be opened, and at the same time lever will strike arm 155, turning catch 151 on its pivot releasing lever 136 and allowing spring 147 to cause valve 127 to close.

It should 'be noted that the eflective area of piston 128, on which fluid pressure may act prior to the opening of valve 127 is less than the efiective area when the valve is off its sea-t. Therefore, these areas may be so proportioned that spring 147 can be relatively light yet still be adequate to hold the hydraulic restraining mechanism closed against heavy reaction loads but, once the valve 127 is opened and valve 100 is closed, only aslight reaction load will be needed to cause further movement of piston 128 suflicient 11 to allow catch 151 to engage latch portion 150 and thus to obviate the necessity for a heavy reaction load when not needed.

The modification illustrated in Figs. l12 is capable of rapid adjustment for automatic operation at high or low reaction loads and for manual operation similar to that of the mechanical latch previously described. It the cam blocks 13S and 144 are engaged so that the projection 143 is in the deepest notch 140 as shown in Fig. 11, the spring 147 will be under only a low compression load, and valve 127 will open when the ram 18 first meets any appreciable resistance from the work. By turning cam block 138 by means of handle 139 so that the projection 143 mates with notch 141, a higher load is placed on spring 147, thereby requiring a higher reaction load from ram 18 to lift valve 127. Further rotation of handle 139 brings notch 142 into engagement with projection 143. In this position spring 147 is substantially solid and the press can not operate hydraulically until the cam blocks are returned to either of the first two positions of engagement.

Further adjustment of the load on spring 147 can be obtained by turning down or unscrewing adjusting nut 137 on the upper end of stud 135. Thus, an infinite number of settings for releasing the hydraulic restraining means may be obtained by first placing the cam block 138 at the approximate setting desired and then making finer adjustments by means of nut 137.

While the invention has been disclosed as it would be used in a small manually operated press, it is obvious that it may be readily adapted to other applications, such as work holding clamps or Vises. By simple modifications of the hydraulic fluid reservoir and the mechanical latch, where this is used, the device may be disposed horizontally or it may be inverted so that the ram can carry a rising platen.

What is claimed is:

l. A thrust producing device comprising, in combination, a supporting frame, a thrust member mounted thereon for movement relative thereto, power-transmission means carried by said frame and movable relative thereto, said power-transmission means having a member in engagement with said thrust member for imparting an initial force thereto, thrust-multiplying means carried by said frame having a portion connected to, and operable by movement of, said power-transmission means to impart a multiplied thrust to said thrust member, said powertransmission means being moved by reaction of the said initial force imparted by said member to said thrust member whereby said thrust-multiplying means imparts a multiplied thrust to said thrust member.

2. The device set forth in claim 1, wherein said thrustmultiplying means comprises a primary element operatively connected to said power-transmission means and a multiplied thrust element connected to said thrust member, movement of said power-transmission means imparting such reaction to said primary element.

3. The device set forth in claim 2, which further includes releasable restraining means operable to hold said power-transmission means against substantial movement relative to said frame and restricting its action to imparting said initial force to said thrust member, said thrust-multiplying means being inoperative while said power-transmission means is restrained but being operable upon release of said transmission means from said restraining means.

4. The device set forth in claim 3, which includes a part carried by said power-transmission means and wherein said releasable restraining means comprises a mechanical latch secured to said frame and operable to restrainingly engage said part. 7 e

5. The device set forth in claim 4, wherein the latched parts are disengageable when said reaction has reached a predetermined magnitude.

6. The device set forth in claim 1,, which further in cludes releasable restraining means comprising a hydraulic mechanism operable to hold said power-transmission means against substantial movement relative to said frame and restricting its action to impartingsaid initial force to said thrust member, said thrust-multiplying means being inoperative while said power-transmission means is so restrained.

7. A thrust producing device comprising a frame and a thrust member movably supported thereby and adapted to engage the work, first and second thrust-imparting means supported by said frame, each of said means 'having provision to impart thrust to said member, said first thrust-imparting means engaging said member for imparting thrust thereto and having a part movable relative to said frame by reaction from said thrust, said second thrustimparting means having an operating portion connected to and movable by said part for imparting an added thrust to said member when said part is moved by said reaction.

8. A device as set forth in claim 7 having a releasable restraining means supported by said frame and engaging said movable part to restrain it from substantial movement and thereby preventing the operation of said second thrustimparting means.

9. In a thrust-producing device, a frame, a ram supported by said frame for longitudinal movement relative thereto, thrust-imparting means supported by said frame and comprising a mechanical linkage engaging said ram for applying initial thrust thereto, said thrust-imparting means having a portion movable with respect to said frame under reaction from the initial thrust applied by said thrust-imparting means to said ram, and hydraulic thrust-imparting means supported by said frame and comprising fluid-displaci-ng means and fluid-pressure-actuated means, said fluid-displacing means being actuated by movement of said movable portion in response to the reaction of said initial thrust, and said fluid-pressure-actuated means being adapted to apply increased thrust to said ram when fluid under pressure is supplied thereto by said fluid-displacing means.

10. A thrust-producing device comprising, in combination, a supporting frame, a ram mounted thereon for rectilinear thrust movement relative thereto, power-transmission means ca-rried by said frame and movable relative thereto in a rectilinear path parallel to said thrust movement, said transmission means having direct mechanical thrust-imparting engagement with said ram, releasable restraining means operable to hold said transmission means against substantial movement relative to said frame and restricting its action to imparting thrust to said ram, thrust-multiplying means carried by said frame, having a primary thrust element connected to said transmission means and a multiplied-thrust element connected to said ram, said thrust-multiplying means being inoperative while said transmission means is held by said restraining means, but being actuated upon release of said transmission means by movement thereof due to reaction of the thrust imparted by it to said ram.

11. The device set forth in claim 10, wherein a gear rack is provided rigid with said ram, and said transmission means comprises a gear carrier and a driven gear carried thereby in operative engagement with said. gear rack.

12. The device set forth in claim 11, wherein said thrust-multiplying means is a hydraulic system.

13. The device set forth in claim 12, wherein the hydraulic thrust-multiplying means comprises relatively small and large cylinders which are intercommunicating, a piston-connected to said gear-carrier and operable in said small cylinder to displace hydraulic fluid to said large cylinder, and a second piston connected to said ram and operable in saidlarge cylinder to impart thrust to said ram.

14. The device set forth in claim 13, which further includes a hydraulic fluid reservoir communicating with saidcylinders to supply fluid thereto, valve means controlling such communication between said reservoir and said cylinders operable to isolate either or both said cylinders from said reservoir, said valve means being urged to closed position by fluid pressure in said cylinders, resilient means further urging said valve means to closed position, and valve-actuating means operable by movement of said transmission means to open at least a part of said valve means.

15. The device set forth in claim 14, wherein said releasable restraining means comprises a mechanical latch secured to said frame and said gear-carrier has a part movable therewith, said mechanical latch being operable to restrainingly engage said part.

16. The device set forth in claim 15, wherein said mechanical latch is operable to release said part when said reaction has reached a predetermined value.

17. The device set forth in claim 10, wherein said thrust-multiplying means is a hydraulic system comprising relatively small and large cylinders which are intercommunicating, a piston connected to said transmission means and operable in said small cylinder to displace hydraulic fluid to said large cylinder, and a second piston connected to said ram and operable in said large cylinder to impart thrust to said ram; and said releasable restraining means comprises valve means disposed in the intercommunication between said small and large cylinders and operable to isolate said cylinders one from the other, and resilient means capable of urging said valve means to isolating position whereby said movement of said transmission means is restrained by the fluid trapped in said small cylinder.

18. A device as set forth in claim 9, wherein said fluid-pressure-actuated means comprises a cylinder having a piston connected to said ram, and wherein said hydraulic thrust-imparting means further includes a fluid reservoir communicating with said cylinder, a valve between said reservoir and said cylinder being urged to closed position by fluid pressure in said cylinder, and valve actuating means operable by said movable portion of said first mentioned thrust-imparting means to open said valve to permit flow of fluid from said cylinder to said reservoir.

19. A thrust producing device comprising, in combination, a supporting frame, a ram mounted thereon for rectilinear movement relative thereto, power-transmission means carried by said frame and having a portion rotatable relative thereto, said transmission means having thrust imparting engagement with said ram, thrust-multiplying means carried by said frame and comprising a hydraulic cylinder With a piston operable therein and connected to said ram to impart thrust thereto, pumping means connected to said transmission means for pumping hydraulic fluid under pressure to said cylinder, and a fluid reservoir communicating with said cylinder and said pumping means, said pumping means having an intake passage connected to said reservoir and a fluid discharge 1 passage connected to said cylinder, said pumping means being operable to supply fluid under pressure to said thrust-multiplying means by movement of said rotatable portion of said power-transmission means due to the 14 thrust imparted by said power transmission means to said ram.

20. The device set forth in claim 19, which further includes a pressure-operated valve between said pumping means and said cylinder for preventing the flow of fluid therebetween until a predetermined pressure is built up by said pumping means.

211. The device set forth in claim 20, wherein said pressure-operated valve is provided with latch means for maintaining it in open position.

22. The device set forth in claim 21, which further includes a valve between said reservoir and said cylinder, and valve-actuating means operable by said transmission means to open said last-mentioned valve while at substantially the same time releasing said pressure-operated valve from said latch means.

23. A thrust-pr0ducing device comprising, in combination, a supporting frame, a ram mounted thereon for rectilinear thrust movement relative thereto, power-transmission means carried by said frame and movable relative thereto, said transmission means having thrust imparting engagement with said ram, thrust-multiplying means carried 'by said frame and comprising relatively small and large cylinders which are intercommunicating, a piston connected to said transmission means and operable in said small cylinder to displace hydraulic fluid to said large cylinder, a second piston connected to said ram and operable in said large cylinder to impart thrust to said ram and a fluid reservoir communicating with said cylinders, -a valve between said reservoir and said small cylinder adapted to permit flow of fluid only from said reservoir to said small cylinder and a second valve between said cylinders adapted to permit flow of fluid only from said small cylinder to said large cylinder, said thrust-multiplying means being actuated by movement of said transmission means due to reaction of the thrust imparted by it to said ram.

24. The device set forth in claim 23, which further includes a pressure-operated valve between said cylinders for preventing the flow of fluid from said small cylinder to said large cylinder until a predetermined pressure is built up in said small cylinder.

25. The device set forth in claim 24, wherein said pressure-operated valve is provided with latch means for maintaining it in open position.

26. The device set forth in claim 25, which further includes a valve between said reservoir and said large cylinder, and valve-actuating means operable by said transmission means to open said last-mentioned valve while at substantially the same time releasing said pressure operated valve from said latch means.

References Cited in the file of this patent UNITED STATES PATENTS 775,853- Philipp et al. Nov. 22, 1904 1,659,157 Prouty Feb. 14, 1928 1,727,626 Adkisson Sept. 10, 1929 2,451,730 Greenlee Oct. 19, 1948

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