US3430538A

US3430538A - Stroke limiting mechanism for hydraulically operated machine

Info

Publication number: US3430538A
Application number: US649252A
Authority: US
Inventors: Adolf Weiss
Original assignee: ALPHA PRESS Co
Current assignee: ALPHA PRESS Co
Priority date: 1967-06-27
Filing date: 1967-06-27
Publication date: 1969-03-04
Anticipated expiration: 1986-03-04

Description

March 4; 1969 ALWEISS 1 3,43 ,538

STROKE LIMITING MECHANISM FOR HYDRAULICALLY OPERATED MACHINE Filed June 27, 1967 Sheet of s INVENTOR ADOLF WEISS BY J ATTORNEYS.

FIG. I

March 4, 1969 A. WEISS 3,430,538

STROKE LIMITING MECHANISM FOR HYDRAULICALLY OPERATED MACHINE Filed June 27. 1967 Sheet 2 of :5

q k m I T; J l INVENTOR \j 3 E E z ADOLF wuss (\l 5 g M9 BY ATTORNEYS.

A. WEISS March 4, 1969 STROKE LIMITING MECHANISM FOR HYDRAULICALLY OPERATED MACHINE Sheet Filed June 27. 1967 INVENTOR WEISS ADOLF ATTORNEYS.

United States Patent 3,430,538 STROKE LIMITING MECHANISM FOR HY- DRAULICALLY OPERATED MACHINE Adolf Weiss, Easton, Pa., assignor to Alpha Press Company, Alpha, N.J., a corporation of New Jersey Filed June 27, 1967, Ser. No. 649,252

U.S. Cl. 91361 13 Claims Int. Cl. F15b 13/16, 11/12, 13/042 ABSTRACT OF THE DISCLOSURE A stroke limiting mechanism to enable the movable member of a hydraulically operated machine to be precisely positioned to an accuracy of 0.0005 inch. Hydraulic cylinder and piston means are coupled to the movable member for movement thereof. Flow control means controls hydraulic fluid flow to the hydraulic cylinder and piston means. An elongated adjustment means carries a pair of stop members which can be relatively adjusted to vary the spacing therebetween. An abutment element carried by the movable member is disposed between the stop members. When the abutment element operatively engages a stop member, the adjustment means is axially displaced to thereby actuate the flow control means which in turn controls hydraulic flow to the cylinder and piston means to stop the movement of the movable member at exactly the predetermined position. An auxiliary stop control means can be coupled with one of the stop members to permit a double stopping of the moveable member. Thus, the moveable member can be stopped in a first predetermined position for a short time interval, then moved to a second predetermined position.

This invention relates to hydraulically operated machinery of the type wherein a hydraulic cylinder and piston assembly moves a moveable member of the machine, and more particularly, this invention relates to a stroke limiting mechanism which enables such a movable member to be stopped precisely at a predetermined position.

While the present invention is not limited to any particular type of machine, it finds particular utility in connection with hydraulic presses used for compacting operations. Such presses generally include a pair of relatively movable punch members, which, when driven toward one another, tend to compress or compact a powder or slurry material therebetween to form an article of desired size and shape. The powder or slurry material from which the article is formed, is usually introduced into a cavity in a die plate, with such a cavity being axially aligned with the punch members of the press. Generally, the bottom punch member extends partially into the cavity to block 01f a portion thereof, and as a result, relative adjustment between the die plate and the bottom punch will vary the size or volume of the cavity.

Those familiar with compacting presses of the type referred to hereinabove will appreciate that the charge of the powder or slurry material cannot reasonably be predetermined since variations occur due to different types of powder, differing humidity and temperature conditions, and so on. As a result, the volume of the powder or slurry, i.e., the size of the charge, is determined strictly by the size of the cavity, which, as aforementioned, can be adjusted by moving the bottom punch member and the die plate or die case relatively to one another. Naturally, it is extremely important that the size of the charge be exactly right so that the article to be formed will have the proper degree of compaction and will be of the proper dimensions. To accomplish such proper sizing of the charge or amount of material fill, the positioning of the die case must be very precise. Specifically, such position- 3,430,538 Patented Mar. 4, 1969 ing should be accurate within 0.0005 inch, and the present invention permits adjustment to this accuracy.

Another factor which must be considered with compacting presses of this type is the fact that it is often necessary to perform two separate positioning operations. That is, the die case may first have to be adjusted to a primary position which is accurate within 0.0005 inch and thereafter such die case may have to be adjusted to a secondary position which is also accurate within 0.0005 inch. An example of a situation where this type of operation would be necessary in one where the part or article to be formed is to have its upper and lower portions formed of difierent types of materials. In such an instance, the die case would initially be adjusted properly and the cavity would be filled with a first type of powder or slurry material. Then, the die case would be adjusted to a secondary position to slightly increase the cavity size and a second fill could then be made with a difierent type of powder or slurry material. In such an instance, due to the accuracy obtained by the present invention, each fill will be accurate and exactly the predetermined quantity of powder or slurry material will be disposed within the cavity for compaction by the machine punches. Another instance where a primary and secondary filling operation would be desirable is where the shape of the upper punch member is such that it normally tends to displace a certain portion of the material during compaction. If, for example, the leading edge of the punch is smaller in diameter than the shank of the punch so that there is a tapering wall portion therebetween, the introduction of the smaller leading end of the'punch into the die cavity will often cause a small portion of the powder therewithin to be displaced completely out of the cavity. Thus, when the main portion of the punch enters the cavity, the puantity of powder within such cavity will be less than that which is requirer. The primary and secondary positioning features of the present invention eliminate this problem. The primary positioning feature can be utilized to properly introduce the desired quantity of material into the cavity. Then, the secondary positioning feature can be utilized to increase the size of the cavity so that the powder material does not extend entirely to the top thereof. By adjusting the die case in this manner to vary the size of the cavity, the smaller or leading edge of the upper punch will not contact the material in the powder until the main portion or shank of the punch enters the top of the cavity. Thus, it is impossible for any of the powder material within the cavity to be entirely displaced out of the die case.

The foregoing considerations make clear that is extremely desirable and beneficial to provide a highly accurate adjusting device for a movable member of a hydraulic machine, such as a die case. In the usual instance, the lower punch is maintained stationary and the die case is moved relatively thereto by a hydraulic cylinder and piston means to thereby vary the size of the cavity. Of course, if desired, the die case could be maintained stationary and the lower punch could be adjusted relatively thereto to vary the size of the cavity. In either event, it will be understood and appreciated that the highly accurate positioning of the parts and the highly accurate variations of the size of the cavity will depend upon the very precise controlling of the hydraulic cylinder and piston means. The stroke limiting mechanism of the present invention accomplishes this desired control of the cylinder and piston means and thereby permits the aforementioned precise positioning of the parts and variation of the cavity size.

With the foregoing in mind it is, therefore, an object of the present invention to provide a. means for very accurately and precisely controlling the stroke of a hydraulic cylinder and piston assembly to thereby adjust a movable member coupled therewith to exactly a predetermined position.

Another object of the present invention is to provide a stroke limiting mechanism for precisely positioning a movable member in a hydraulically operated machine to an accuracy within 0.0005 inch.

Another object of the present invention is to provide an adjustment which enables a highly accurate primary positioning of a movable member in a hydraulically operated machine, and thereafter enables a similarly accurate secondary positioning of such movable member.

Another object of the present invention is to provide a means for accomplishing at least one, and preferably two, precise adjustments of the size of a cavity in a hydraulic compacting press.

Another object of the present invention is to provide a novel and efiicient means for controlling the stroke of a hydraulic cylinder and piston means to thereby control the movement of a member operated by such hydraulic cylinder and piston means.

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the invention.

Referring to the drawings:

FIGURE 1 is a sectional view of a stroke adjustment mechanism in accordance with the principles of the present invention coupled with a hydraulic operated machine;

FIGURES 2, 3 and 4 are sectional views showing a flow control means which forms a part of the present invention in various different operating positions; and,

FIGURES 5 and 6 are fragmentary sectional views showing the various operating positions of the secondary positioning device of the present invention.

In general, the apparatus of the present invention which is generally designated 10 includes a hydraulic operating means generally designated 12, a flow control means generally designated 14 and an elongated adjustment means generally designated 16.

The hydraulic operating means 12 includes an enlarged cylinder 18 having a rod end 20 and a blind end 22. An enlarged piston 24 is movably mounted within the cylinder 18 and is operable under hydraulic pressure from fluid introduced into the cylinder. A piston rod 26 extends from the piston 24 through the rod end 20 of the cylinder and connects to a lower platen 28. The lower platen 28 is dis posed beneath a stationary press table 30 having a lower tool or punch 32 mounted thereon. A die case or die plate 34 is disposed above the press table 30 and is provided with a cavity 36 axially aligned with the punch 32. Upstanding rods or support members 38 extend through suitable openings in the press table 30 to connect the die case 34 with the lower platen 28. It will thus be appreciated that movement of the piston 24 causes a corresponding movement of the lower platen 28 and a corresponding movement of the die case 34. As the die case is moved toward or away from the press table 30, the lower punch 32 will move further into or out of the cavity 36 and hence the volume of the cavity will be changed. It will, therefore, be appreciated that proper adjustment or control of the degree of movement of the piston 24 will serve to carefully control the positioning of the die case 34, which, in turn, will serve to very accurately determine the size of the cavity 36. Through utilization of the present invention, it is possible to position the die case 34 within an accuracy of 0.0005 inch, to thereby give extremely accurate control of the size of the cavity 36. The powder or slurry material to be compacted is then introduced into the die cavity 36 where it is supported upon the upper surface of the lower tool or punch 32. A scraper or other suitable expedient is utilized to remove any excess powder which extends above the upper surface of the die case 34 so that the volume of the powder charge will be exactly as predetermined.

An upper platen 40 is movably mounted above the die case and is supported by a suitable operating rod 42. This rod may be driven by any suitable power source such as an additional hydraulic cylinder and piston means, to thereby permit the upper platen 40 to be raised and lowered. An upper punch 44 is mounted on the undersurface of the upper platen 40 in coaxial alignment with the cavity 36 and the lower punch 32. Thus, when the upper platen 40 is lowered for a sufiicient distance to introduce the upper punch 44 into the cavity 36, the powder or slurry material already in the cavity 36 will be compacted between the

respective punches

32 and 44. This, of course, will form the article being pressed. By varying the shape of the respective punch members, or by varying the configuration of the cavity 36, or both, suitable shapes may be imparted to the article being formed.

In the form illustrated, the upper punch 44 has a main shank diameter substantially the same size as the cavity 36. However, the leading end 46 of the punch is somewhat smaller in diameter and a tapering or diverging wall portion 48 extends between the leading end and the punch shank. As mentioned hereinabove, when a punch of this configuration is introduced into a cavity wherein the powder level extends entirely to the top surface of the die case 34, there is a tendency to force or displace some of the powder along the tapering portion 48 so that such powder will be outside of the cavity by the time that the main shank portion of the punch enters the cavity. If this occurs, the quantity of power material in the finish article will be less than that predetermined, and as a result, the finished article will not have the required degree of compaction. To overcome this problem, the present invention can include both a primary and a secondary positioning device. The primary positioning means would move the die case 34 until the size of the cavity 36 was such that exactly the required amount of powder would fill the same and be even with the top level of the die case. Then, a secondary positioning means can be utilized to raise the die case 34 by a small increment so that the level of the powder therein will no longer be even with the top surface of the die case 34. Instead, there will be a small upper portion of the cavity which will have no powder at all therewithin. Thus, when the upper platen 40 is lowered and the upper punch 44 starts to enter the cavity 36, the leading end 46 thereof will not contact the powder until theentire tapered surface 48 has passed the top level of the die case. In this manner, none of the powder can be forced out of the cavity during the compacting operation.

From the foregoing description, it will be appreciated that the entire purpose of the present invention is to provide a means for very accurately positioning the die case 34 to thus vary the cavity size. In any event, at least one positioning of the die case 34 will be required, and in many instances, a first positioning of the die case will be required, to be followed by a second positioning of the die case. Each of these positioning steps must be so accurately controlled that the final placement of the die case is accurate within 0.005 inch. As aforementioned, it would also be possible to maintain the die case 34 in a stationary position and to connect the press table 30 with the lower platen 28 so that the two would move concurrently. In such event, the cavity 36 would remain stationary and the lower punch 32 would be accurately raised and lowered therein to adjust the final cavity volume. Having thus described the general operating characteristics of the overall press and the objectives to be accomplished by the present invention, attention will now be directed to the means by which the objectives of the present invention are accomplished.

It will first be seen that an elongated rod or shaft 50 depends from the lower platen 28, passes through an opening in a plate 52 connected with the rod end 20 of the cylinder and serves to mount a cross-plate element 54 at the lower end thereof. The elongated adjustment means 16 of the present invention includes a pair of elongated rods 56 disposed on opposite sides of the rod 50, each of the rods 56 having screw threads 58 disposed along the major portion thereof. Each of the threaded rods or shafts 56 extends through the plate 52 and, if desired, an enlarged head 60 can be provided on the upper end of the rods 56. As can best be seen from FIGURES 5 and 6 hereof, the cross-plate 54 includes an opening 62 along either side thereof through which the threaded shafts 56 freely extend. Thus, as the lower platen 28 is raised or lowered through operation of the piston 24, the cross-plate 54 can be raised and lowered along the threaded rods or shafts 56 without engaging the same. An elongated rib or runner 64 is affixed to the cylinder body 18 and serves more or less as a key which fits into a groove along the edge of the cross-plate 54 to prevent the same from rotating as it is raised and lowered.

A pair of stop members are provided on the adjustment means 16, with one such stop member being mounted on each threaded rod 56. Each stop member has an internally threaded aperture whose screw threads mate with the screw threads 58 on the shafts 56. Thus, the stop members act similarly to nuts which are threaded upon the shafts 56 and whose axial position therealong can be adjusted by relative rotation between the stop member and the shaft itself. The lower stop member is designated 66 and it includes a groove 68 along the edge thereof which receives the rib or runner 64. This prevents the lower stop member 66 from rotating. The upper stop member designated 70 is mounted upon the other threaded shaft and it includes a groove portion 72 along the inner edge thereof which at least partially surrounds the rod 50. This prevents the upper stop member 70 from rotating. There is thus a spacing or gap between the lower stop member 66 and the upper stop member 70 and the cross-plate 64 is movable therebetween. As can best be seen in FIGURES 2 through 6, each rod 56 has mounted thereupon, near the lower end thereof, a sprocket 74. Each sprocket is fixed to the rod, as by means of a pin 76, so that rotation of the sprockets will in turn cause rotation of the rods 56. The sprockets may each be connected by means of a chain drive to a suitable hand wheel or other adjusting means, which, when operated, causes the rod 56 to rotate. As each rod 56 is rotated, the stop member mounted thereupon is moved axially upward or downward therealong, depending upon the direction of rotation. Thus, by proper operation of both hand wheels, the spacing between the upper stop member 70 and the lower stop member 66 can be selectively adjusted.

The present invention also includes a flow control means generally designated 14, connected with the hydraulic operating means at the blind end 22 thereof. Such fiow control means includes a valve body 80 having a first hydraulic port 82 adapted to be connected with a main flow control valve generally designated 84 and a second hydraulic port 86 connected with the blind end 22 of the cylinder 18. A movable spool type valve member 88 is mounted within the valve body and is operable to establish or disestablish flow between the

hydraulic ports

82 and 86. Thus, hydraulic fluid fiow to and from the blind end of the cylinder 18 must traverse the valve body 80.

As can best be seen from FIGURES 2-4, the lower end of the threaded shafts 56 includes a reduced diameter portion disposed within a bore 90 formed in the top of the valve body 80. Actuator means in the form of an enlarged actuator plate 92 is attached to the two threaded rods 56. Specifically, the actuator plate 92 includes a pair of enlarged openings, one coaxially aligned with each of the threaded shafts 56. A bushing type hearing 94 is disposed within each of these openings and extends between the top surface of the plate 92 and the lower surface of the sprocket 74. A locking nut or element 96 is disposed beneath the lower surface of the plate 92 and is connected to the shaft by means of a pin 98. In this manner, the actuator plate 92 is locked in position upon the two threaded shafts 56 and is movable therewith. The lower end of the threaded shafts, which is reduced in diameter, extends beyond the locking member 96 and at least partially into the cavity or bore formed in the top surface of the valve body 80. Also, the valve member 88 is connected to the actuator plate by means of an enlarged connecting screw 100 so that movement of the actuating plate 92 controls movement of the valve member 88.

The flow control means of the present invention includes signal generating means, which, in the preferred embodiment of the present invention, consists of a pair of spaced apart

limit switches

102 and 104. At least a portion of the actuator plate means 92 is disposed between these two signal generating means and is engageable with one or the other thereof. While this exact operation will be described in further detail hereinafter, it is sufiicient to state at the present time that such movement of the actuator plate means 92 is broadly responsive to movement of the cross-plate 54. A biasing means generally designated 106, which will also be described in detail hereinafter, acts upon the valve spool 88 and hence upon the actuator plate 92 to normally position such actuator plate in the position shown in FIGURE 4 whereat neither of the signal generating means is engaged or actuated. When the lower platen 28 is lowered, however, the cross-plate 54 will eventually contact the lower stop member 66. After such contact occurs, and lower platen 28 continues to move downwardly, the force of the crossplate 54 on the lower stop member 66 will cause both threaded shafts 56 and the actuator plate 92 connected therewith, and the movable valve member 88 connected therewith, to move downwardly against the force of the biasing means 106. Such downward movement will continue until the assembly reaches the lowermost position as shown in FIGURES 1 and 2 whereat the actuator plate means 92 operates the lower limit switch 102. A1 ternatively, if the lower platen 28 is raising and the crossplate 54 operatively engages the upper stop member 70, the entire assembly will be raised against the force of the biasing means 106 until it reaches the position of FIGURE 3 whereat the actuator plate means 92 energizes the upper limit switch 104.

It will, of course, be understood and appreciated that the signal generating means of the present invention need not be confined strictly to the

limit switches

102 and 104 disclosed hereinabove. Instead, any suitable form of electrical, mechanical, optical or other form of control means may be utilized. For example, the

limit switches

102 and 104 might be replaced by photocell devices wherein the actuator plate means 92 breaks the light beam as it is raised or lowered. It is sufficient to state that the signal generating means shculd be such that a neutral position can be assumed, as shown in FIGURE 4, whereat no signal is given, that a lower signal device is actuated, as shown in FIGURE 2 and that an upper signal device is actuated, as shown in FIGURE 3. It will also be understood that the threaded shafts 56 themselves are slightly raised and lowered due to the contacting force of the cross-plate 54. Thus, the length of the bores 90 in the valve body 80 should be such that the lower end of the shaft 56 can move from the position of FIGURE 2 to the position of FIGURE 3 without becoming displaced therefrom.

Refering again to the valve body 80, it will be seen that the same includes a central bore extending completely therethrough with the diameter of such bore corresponding substantially to the diameter of the movable valve spool or member 88. Thus, while the valve body 80 can be mounted in a stationary manner, the valve member or spool 88 therewithin can be moved in a reciprocable manner due to movement of the actuator plate means 92. A pair of

annular flow chambers

110 and 112 are formed in spaced apart relationship in the valve housing as can best be seen from FIGURES 2, 3 and 4. The flow chamber 110 communicates with the port 86 while the flow chamber 112 communicates with the port 82. That portion of the valve body between the

flow chambers

110 and 112 defines a land area 114 having a flat shoulder portion 116 defining a boundary of the flow chamber 110 and a similar flat shoulder portion 118 defining a boundary of the flow chamber 112.

The valve member 88 has a reduced diameter portion 120 formed therein which is bounded by a pair of spaced apart shoulder areas 122 and 124. As can be seen, the length of the reduced diameter portion 120 as determined by the distance between the shoulder portions 122 and 124, exceeds the length of the valve body land portion 114 as determined by the distance between the shoulder portions 122 and 124. A first flow passage 126 extends through the valve member 88 and communicates with the flow chamber 110, regardless of the position of the valve member. A similar flow passage 128, disposed on the opposite side of the reduced diameter portion 120, extends through the valve member 88 and communicates with the flow chamber 112, regardless of the position of the valve member. A central flow passage 130 is disposed medially of the reduced diameter portion 120 and extends therethrough.

As can be seen from the drawings, a pair of

check valve chambers

132 and 134 are formed interiorly of the valve member 88 with the check valve 136 being disposed within the chamber 132 and the check valve 138 being disposed within the chamber 134. A central core 140 is positioned between the

check valve chambers

132 and 134. This check valve core 140 has transverse bore communicating with the flow passage 130 and it also has an axial bore communicating with the transverse bore to thereby admit flow from the flow passage 130 into the check valve chambers. Thus, the check valve 136 controls cross flow between the flow passage 130 and the flow passage 126. In a similar manner, the check valve 138 controls cross flow between the flow passage 130 and the flow passage 128.

To complete description of the valve means, it will be seen that a pair of

auxiliary ports

150 and 152 are formed in the valve body 80. The port 150 is a pressure port which is connected to the pressurized source of hydraulic fluid while the port 152 is an exhaust port which returns to the tank or reservoir. An annular recess 154 is formed in the valve member 88 as shown in FIGURES 2, 3 and 4, with the position of this annular portion normally providing communication with the pressure port 150. However, as shown in FIGURE 3, when the valve is moved to its uppermost position, the length of the annular portion 154 is such as to permit cross flow between the

hydraulic ports

150 and 152.

Considering now the biasing means 106, it will be seen that the lower end of the valve member 88 carries a shaft 160 having a threaded end thereupon. This shaft 160 passes freely through enlarged apertures in

plates

162 and 164 which have a compression spring 166 disposed therebetween. A nut 168 mounted on the end of the shaft 160 prevents the plates and the spring from becoming disengaged therefrom. The entire biasing means is housed within a casing 170 coupled with the valve body 80 and the casing has an internal shoulder 172 formed therein. When the cross plate 54 is out of engagement with either stop member so that the elongated adjustment rods 56 are not being either raised or lowered, due to movement of the lower platen 28, the compression spring 166 exerts a suflicient biasing force to move the parts to the position shown in FIGURE 4, which can also be referred to as a centered position. That is, the plate 162 is biased into engagement with the valve body 80 while the plate 164 is biased into engagement with the shoulder 172 on the casing. It will also be noted that the valve member 88 itself is in a centered position wherein the reduced diameter portion thereof is centered with respect to the land portion 114 of the valve body. In this position, hydraulic flow between the

hydraulic ports

82 and 86 is direct and need not take place through the flow passages disposed interiorly of the valve member 88. The annular recess 154 is aligned with the pressure port 150 of the valve body.

As shown in FIGURE 2, the valve member is in its lowermost position and this situation occurs when the downward force of the cross-plate means 54 against the lower stop member 66 exceeds the biasing force of the spring 166. In this position, the shoulder 122 on the valve member 88 is substantially aligned with the shoulder portion 16 of the flow chamber 10. This prevents the direct communication between the

hydraulic ports

82 and 86 and such communication must therefore be established through the internal flow passages within the valve member. In such situation, the fluid at supply pressure will be delivered through the port 82, will flow through the central flow passage and the core and will cause the check valve 136 to lift from its solid line position in FIGURE 2 to its dotted line position therein. This slight lifting of the check valve 136 will enable a small amount of fluid at supply pressure flow to pass through the chamber 132, through the flow passage 126, through the flow chamber 110 and through the hydraulic port 86 into the cylinder 18. This will gradually start the lifting of the valve member 88 since the fluid entering through the port 86 into the cylinder 18 will act on the underside of the piston 24 to raise the piston and the platen 28 connected therewith. As the platen 28 lifts, so does the cross-plate element 54 which is connected to the platen by the rod 50. When the element 54 thus raises away from the lower stop member 66, the forces resisting the biasing means 106, and in particular, the spring 166, are released, and hence the biasing means exerts an unresisted upward force to raise the valve member 88. As soon as the valve member 88 has lifted slightly, so that the level of the valve member shoulder 122 is above the level of the land shoulder 116, direct flow will again be established between the

ports

82 and 86.

The reverse situation can be established as shown in FIGURE 3, when the pressure of the cross-plate means 54 against the upper stop member 70 is sufiicient to overcome the biasing force of the spring 166. In such event, the valve member 88 is raised until the shoulder portion 124 thereof is substantially aligned with the shoulder portion 118 along the land 114. It will also be noted that shortly prior to the shoulders 118 and 124 coming into alignment, the annular portion 154 of the valve body will communicate with the exhaust port 152 to relieve the pressure of the fluid within such annulus. When the alignment of the shoulders takes place, direct flow between the

ports

82 and 86 is blocked off and flow must therefore take place through the internal passages of the valve member. In such event, the fluid at return pressure enters through the port 86, passes through the center flow passage 130 and the core 140 and enters the check valve chamber 134, moving the check valve 138 therein from its solid line position of FIGURE 3 to its dotted line position. This permits a small amount of fluid at return pressure to pass from the check valve chamber 134 through the flow passage 128, through the flow chamber 112 and through the hydraulic port 82. At this time, the higher pressure within the cylinder 18 will be acting upon the upper face of the piston 24 and thus the piston 24, and the platen 28 and cross-plate element 54 coupled therewith, will start to lower. This lowering, of course, removes the cross-plate element 54 from its aforementioned contact with the upper stop member 70 and thus the biasing force of the spring 166 once again takes over to urge the valve member 88 downwardly. During the lowering of the valve member 88, as soon as the shoulder portion 124 thereof has lowered beneath the level of the shoulder 118 on the land, direct communication between the

hydraulic ports

82 and 86 will again be established.

Before describing even the simplest operation of the overall unit, it is necessary to describe the main flow control valve 84. This valve is a conventional four-way hydraulic valve having a pair of spring biased energizing

solenoids

180 and 182 connected therewith. The limit switch 104 is electrically coupled with the solenoid 180 and the limit switch 102 is electrica ly coupled with the solenoid 182. It will, of course, be understood that the four-way main control valve 84 connects directly to the rod end 20 of the cylinder and connects through the

valve

80, 88 to the blind end 22 of the cylinder. Thus, depending upon the position of the valve 84, pressurized fluid designated P will be delivered therethrough to one end of the cylinder 18 and exhaust fluid from the other end of the cylinder will return therethrough to a tank designated T.

It will be seen that an auxiliary stop control means or secondary positioning device generally designated 200 is connected with the upper stop member 70. The details of this control means will be described in detail hereinafter and it will be understood at this point that the control means 200 is utilized to control secondary adjustment or second movement of the die case 34. However, if only a primary adjustment were desired, the entire means 200 could be removed so that the cross-plate 54 could directly contact the upper stop member 70. To describe the operation of this simpler embodiment of the invention, let it be considered that a flow line L1 connects from the main flow control valve 84 to the port 82 in the valve body 80 and that a similar flow line L2 connects from the main flow control valve 84 to a hydraulic port (not shown) at the rod end 20 of the cylinder. Let it be assumed that the parts are in the withdrawal position shown in FIGURES 1 and 2 and that the die case 34 is lowered to a position whereat the top of the punch 32 is even with the top of the die case 34. Upon a signal S to the solenoid 180, the pressure P is connected with the line L1, and the line L2 is connected with the tank T. It will also be seen that at such position, the actuator plate means 92 is engaged with the limit switch 102. The pressurized hydraulic fluid being delivered to the line L1 flows through the center flow passage 130 and the core 140, lifts the check valve 136, flows through the check valve chamber 132 and the flow passage 126, then through the flow chamber 110 and the hydraulic port 86 to enter the cylinder 18 and to exert pressure on the underside of the piston 24. This force exerted on the underside of the piston 24 will start to lift the same very slightly thereby causing the lower platen 28 and the die case 34 connected thereto to move upwardly. Similarly, this upward movement will lift the cross-plate means 54 from engagement with the lower stop member 66 and thus the biasing spring 166 can lift the valve member 88 and the actuator plate means 92 connected thereto. This releases the limit switch 102 and at the same time raises the valve member shoulder 122 above the level of the land shoulder 116. At this time, the full capacity of the flow through the line L1 can be delivered directly from the hydraulic port 82 to the hydraulic port 86. At such time, the valve will be in the centered position shown in FIGURE 4. The upward movement of the piston 24 will continue due to the force of the pressurized fluid therebeneath and consequently, the die case 34, the lower platen 28, the rod 50 and the cross-plate means 54 will all continue to raise. Such raising will continue thus causing the crossplate means 54 to contact the upper stop member 70. Further upward movement will overcome the biasing force of the spring 166 and will lift the rods 56 until the actuator plate means 92 contacts the limit switch 104. At this time, the valve will have reached the position shown in FIGURE 3 blocking the flow of further pressurized fluid to the underside of the piston 24. This will stop any further movement of the piston 24 and hence of the die case 34 connected therewith. The present invention enables such stopping to take place within an accuracy of 0.0005 inch and when such stopping has taken place, that portion of the cavity 36 disposed above the lower punch 32 will be exactly of the predetermined amount. Then, suitable powder or slurry material can fill the cavity and the upper platen 40 can be lowered until the upper punch 44 enters the cavity and compacts the material therewithin to form the finished article. The upper platen 40 is then raised and the finished article remains disposed in the cavity.

Then a signal S can be delivered to the solenoid 182 to cause a flow reversal through the main flow control valve 84. That is, the pressurized fluid P will be delivered through the line L2 and the line L1 will be connected with the tank T. This pressurized fluid will act on the upper face of the piston 24 thereby causing the same to move downward slightly. This downward movement of the piston 24 will cause a downward movement of the cross-plate means 54 thus releasing the same from the upper stop member 70. The biasing force of the spring 166 can then start to act upon the same to move the valve from the position of FIGURE 3 to the position of FIGURE 4. Initially, because direct flow from the hydraulic port 86 to the hydraulic port 82 is blocked, the flow will be through the center flow passage and the core to displace the check valve 138. Such flow will continue through the check valve chamber 134, the flow passage 138 and the hydraulic port 82 and will return to the tank T. However, as soon as the shoulder 124 descends below the level of the land shoulder 118, direct and full capacity flow between the

hydraulic ports

86 and 82 will be established. The piston 24 will continue its downward movement thus causing the cross-plate means 54 to contact the lower stop member 66. Further downward movement will return the parts to the position shown in FIGURES 1 and 2. At this time, the die case 34 will have been lowered and the finished part will remain seated freely upon the punch 32. Such finished part can then be automatically or manually removed or ejected from the press. Thereafter, the foregoing cycle can be repeated.

When electrical signal S is supplied to the solenoid 180, such as by closing of a manual switch, valve 88 and actuator plate 92 raise until limit switch 104 is contacted. This contact of plate 92 against limit switch 104 releases the signal S, thus effectively deenergizing solenoid 180, and at this time, the die case 34 is stopped at the proper raised position. When electrical signal S is supplied to the solenoid 182, the valve 88 and actuator plate 92 lower until limit switch 102 is contacted, and this contact releases the signal S. At this time, the die case 34 will be at the proper lowered position and the finished part will, as aforesaid, be seated freely upon the punch 32.

It will be understood that the foregoing cycle of operations is applicable and useful in a situation wherein only a single controlled stop of the die case 34 is desired. However, as mentioned hereinbefore, it is often desirable to provide a double stopping action and in such event, the secondary or auxiliary positioning device 200 becomes important. For a more detailed description of this means 200, attention is directed to FIGURES l, 5 and 6. By referring to such figures, it will be seen that a cylinder body 202 is mounted on the stop member 70 and is fixed therewith. A piston 204 is movably mounted within the cylinder and is provided with a piston rod 206 depending therefrom. This piston rod carries an auxiliary plate 208 having an aperture 210 therewithin to permit free passage of the threaded shaft 56. The plate 208 also has a groove 212 positioned at the end thereof which cooperates with the rod 50 of the cross-plate means 54 to prevent inadvertent rotation thereof. An adusting screw 214 is connected with the cylinder 202 to vary the stroke of the piston 204 therewithin. A cross flow valve means generally designated 216 is connected with the cylinder 202 to enable pressure to be delivered either above or beneath the piston 204. A control solenoid 218 is connected with the valve 216 to control the position thereof. It will be understood that once the auxiliary positioning means 200 is provided, the cross-plate means 54 no longer directly contacts the upper stop member 70, but instead, only operatively contacts or engages the same.

To understand the operation of the secondary positioning device 200, let attention first be directed to FIG- URE 5. In such figure, the valve 216 is delivering pressurized fluid through the top of the cylinder 202, thereby causing the piston to assume the position shown in FIG- URE at the bottom of the cylinder. In the solid line illustration of FIGURE 5, the cross-plate means 54 is just contacting the plate 208, thus meaning that the rod 50 and the main piston 24 are still moving upwardly. As further upward movement continues, the entire assembly will be lifted from its solid line position to its dotted line position in FIGURE 5. That is, since the pressure on the top of the piston 204 exceeds the lifting force of the cross-plate means 54, the piston 204 and the piston rod 206 will not move upwardly in the cylinder 202. Instead, the entire piston and cylinder means will be lifted, thereby causing the threaded rod 56 to be lifted against the forces of the biasing means 106. Thus, the actuator plate means 92 will be lifted until the same actuates the limit switch 104 as shown in dotted lines. At this time, the primary or initial positioning of the die case 34 will have been completed within its desired accuracy.

To now accomplish the secondary positioning, attention is directed to FIGURE 6. In this figure, the parts shown in solid lines are in the same position as the parts shown in dotted lines in FIGURE 5. In other words, the solid line illustration of FIGURE 6 shows the parts with the primary positioning of the die case having been completed. To accomplish a secondary positioning, the solenoid 218 is energized by a signal S" thereby reversing the flow through the valve 216. When this occurs, the pressurized fluid will be delivered beneath the piston 204 and the fluid above the piston 204 will be returned to the tank. This will cause the plate 208 to 'be lifted out of contact with the cross-plate 54, as shown in dotted lines, with the increment of lift being determined through appropriate adjustment of the screw 214. As soon as the plate 208 is lifted away from the cross-plate 54 in this manner, the biasing means 106 acts upon the valve body 88 to center the same as shown in FIGURE 4 and to thus release the actuator plate means 92 from the limit switch 104. Release of the limit switch 104 enables the signal S to the main flow control valve solenoid 180 to start the pressurized fluid flowing through the line L1 once again. Such pressurized fluid flow will again act upon the main piston 24 and will cause the same to raise again thereby giving an additional raising movement to the die case 34 and to the cross-plate 54. When the crossplate 54 again contacts the plate 208, the valve 88 will again have been moved to the position of FIGURE 3 and the limit" switch 104 will again have been actuated, thereby deenergizing the solenoid 180. At this time, the secondary positioning of the die case will have been accomplished and further movement of the main piston 24 and of the die case 34 will terminate. Thus, the secondary positioning will have been accomplished through utilization of the secondary control means 200.

After reading the foregoing detailed description, it should be apparent that the objects set forth at the outset of the specification have been successfully achieved by the present invention.

What is claimed is:

1. Stroke limiting mechanism for precisely positioning a movable member in a hydraulically operated machine, said mechanism comprising:

hydraulic operating means for moving said movable member;

flow control means for controlling hydraulic flow to and from said hydraulic operating means;

elongated adjustment means including spaced apart stop means;

said stop means being relatively adjustable in position to selectively vary the spacing therebetween;

an element coupled with said movable member and movable responsively therewith;

said element being movable in said space between said stop means and being operatively engageable with said stop means; said flow control means including signal generating means to at least partially control hydraulic flow;

said hydraulic operating means being operative to move said movable member and to responsively move said element into operative engagement with a stop means whereupon further movement of said element displaces said adjustment means to thereby actuate said signal generating means which, in turn, causes said flow control means to stop said hydraulic operating means with said movable member thus being located precisely at a predetermined position;

said flow control means including valve means and actuator means coupled with said adjustment means and engageable with said signal generating means.

2. Stroke limiting mechanism as defined in claim 1 wherein said valve means includes a valve housing and a movable valve member disposed therewithin and wherein said actuator means is connected with said valve member whereby movement of said adjustment means causes a corresponding movement of said actuator means and said valve member.

3. Stroke limiting mechanism for precisely positioning a movable member in a hydraulically operated machine, said mechanism comprising:

hydraulic operating means for moving said movable member;

elongated adjustment means including spaced apart stop means;

an element coupled with said movable member and movable responsively therewith;

said elongated adjustment means including apair of spaced axially elongated threaded shafts;

said stop means including a stop member mounted on each threaded shaft and selectively movable axially therealong.

4. Stroke limiting mechanism as defined in claim 3 further including means on at least one of said threaded shafts to effect rotation thereof to adjust the axial position of the stop member thereon, to thereby enable selective variation of the axial distance between that stop member and the stop member on the other threaded shaft.

5. Stroke limiting mechanism for precisely positioning a movable member in a hydraulically operated machine, said mechanism comprising:

hydraulic operating means for moving said movable member;

elongated adjustment means including spaced apart stop means;

an element coupled with said movable member and movable responsive therewith;

said element being movable in said space between said stop means and being operatively engageable with said stop means;

said fiow control means including signal generating means to at least partially control hpdraulical flow;

said flow control means including actuator means coupled with said adjustment means and engageable with said signal generating means and also including biasing means acting upon said actuator means and hence acting upon said adjustment means.

6. Stroke limiting mechanism as defined in claim further including an auxiliary stop control means, said auxiliary stop control means including a first portion coupled with one of said stop means and a second portion movable relatively to said first portion, said second portion being at least partially disposed in the space between said stop means whereupon said element contacts said second portion, thus effecting said operative engagement with said one stop means.

7. Stroke limiting mechanism as defined in claim 6 wherein said first portion is a cylinder means and wherein said second portion includes a piston movably mounted in said cylinder means, a piston rod fixed to said piston and projecting beyond said cylinder means, and a plate mounted to said piston rod, with said plate including a portion juxtaposed to said one stop means and interposed in the path of movement of said element.

8. Stroke limiting mechanism as defined in claim 7 wherein said cylinder means includes an adjustable stop member which adjusts the degree of movement of said piston within said cylinder means.

9. Stroke limiting mechanism for precisely positioning a movable member in a hydraulically operated machine, said mechanism comprising:

hydraulic cylinder and piston means adapted to receive a supply of hydraulic fluid for operation thereof; said piston means being coupled with said movable member to effect positioning thereof;

elongated rod means coupled with said movable member;

abutment plate means carried by said elongated rod means whereby said abutment plate means moves responsively with said movable member;

at least one axially elongated threaded shaft means juxtaposed to said elongated rod means;

said threaded shaft means being mounted to permit a limited degree of axial movement;

first and second stop members threadably mounted upon said threaded shaft means in spaced relation;

said threaded shaft means being rotatable to thereby vary the spacing between said first and second stop member;

actuator means mounted upon said threaded shaft means and axially movable therewith; flow control means for controlling hydraulic fluid flow to said hydraulic cylinder and piston means;

said flow control means including valve means coupled with said hydraulic cylinder and piston means and also including signal generating means for controlling hydraulic flow to said valve means;

said valve means including a movable valve member coupled with said actuator means and movable therewith;

said actuator means being engageable with said signal generating means for actuation thereof; biasing means acting upon said actuator means to normally bias the same out of engagement with said signal generating means;

said hydraulic cylinder and piston means being operative to move said movable member and to responsively move said abutment plate means through the space between said stop members until said abutment plate means operatively engages a stop member whereupon further movement of said abutment plate means axially displaces said threaded shaft against the force of said biasing means and hence causes said actuator means to engage said signal generating means and said valve member to change position whereby hydraulic fluid flow to said hydraulic cylinder and piston means is controlled to stop operation thereof and thereby stop movement of said movable member precisely at a predetermined position.

10. Stroke limiting mechanism as defined in claim 9 wherein said biasing means is coupled with and active upon said movable valve member.

11. Stroke limiting mechanism as defined in claim 9 further including an auxiliary stop control means having a pair of telescoping parts, one of which is fixed to said first stop member and the other of which carries a projecting portion juxtaposed to said first stop member whereby said abutment plate means contacts said projecting portion thus effecting an operative engagement with said first stop member.

12. Stroke limiting mechanism as defined in claim 11 wherein said telescoping parts include a cylinder means and a piston means and wherein hydraulic fluid can be selectively supplied to said cylinder means to control the telescoping of the piston means therewithin.

13. Stroke limiting mechanism as defined in claim 12 wherein said cylinder means includes an adjustable member to vary the stroke of said piston means.

References Cited UNITED STATES PATENTS 1,932,976 10/1933 Lams et al. 91-275 2,331,108 10/ 1943 Ganahl. 2,351,956 6/ 1944 Graham.

PAUL E. MASLOUSKY, Primary Examiner.

US. Cl. X.R.