US3407710A

US3407710A - Stroke adjustment means for cylinder and piston assembly

Info

Publication number: US3407710A
Application number: US601791A
Authority: US
Inventors: Adolf F Weiss
Original assignee: ALPHA PRESS Co
Current assignee: ALPHA PRESS Co
Priority date: 1966-12-14
Filing date: 1966-12-14
Publication date: 1968-10-29
Anticipated expiration: 1985-10-29

Description

Oct. 2 9, 19 68: A. F. WEISS 3,407,710

STROKE ADJUSTMENT MEANS FOR CYLINDER AND PISTON ASSEMBLY Filed Dec. 14, 1966 46 e2 48 FIG. I

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INVENTOR 5 m ADOLF F WEISS i I ;QM

ATTORNEY United States Patent 3,407,710 STROKE ADJUSTMENT MEANS FOR CYLINDER AND PISTON ASSEMBLY Adolf F. Weiss, Easton, Pa., assignor to Alpha Press Company, doing business as Alpha Industrial Center, Alpha,

N.J., a corporation of New Jersey Filed Dec. 14, 1966, Ser. No. 601,791 Claims. (CI. 92-13) ABSTRACT OF THE DISCLOSURE A stroke adjusting means for a hydraulic cylinder and piston assembly which includes a casing coupled to the cylinder and communicating with the interior thereof to receive the pressurized hydraulic fluid. A threaded shaft is disposed within the casing and is connected to the piston for movement therewith. A nut is carried by the threaded shaft and a sleeve means is engaged with the nut to normally prevent rotation thereof but to permit the nut to move axially in the casing as the threaded shaft moves. The nut contacts against a stop means to limit the stroke of the cylinder and piston assembly. By rotating the sleeve means, the axial position of the nut along the threaded shaft can be varied to thereby vary the stroke of the assembly.

This invention relates to a stroke adjustment means for a cylinder and piston assembly and more particularly it relates to a positive mechanical stroke stop means whose position can be selectively adjusted to vary the stroke of a hydraulic assembly and of a member operated or moved thereby.

The present invention finds particular utility in hydraulic presses which are used for compacting operations. In a press of this type, either a powder or slurry material is introduced into a die cavity and a pair of cooperating and relatively moving punches or tool members compact the material to form a particular pressed article. A common type of hydraulic press utilizes a bottom punch or tool which is fixed in position and an upper punch or tool which is mounted on a platen which in turn is operated by a hydraulic cylinder and piston assembly. The material to be compacted is introduced into a die cavity between the tools or punches and the upper punch is thereafter lowered through operation of the hydraulic cylinder and piston assembly to properly compact the material in the die cavity and to form the finished article. The degree of movement of the upper tool or punch therefore determines the height of the article being pressed and the amount of density or compaction thereof, and as a result, it is important that this degree of movement be very accurately controlled.

There have, in the prior art, been proposals and attempts to entirely dispense with a stroke adjusting mechanism and to merely use shims or the like to control the height of the article being pressed. This, however, was found to be a rather crude and inaccurate system involving long periods of trial and error. There have also been various suggestions to use some type of a stroke adjusting device for the purpose described hereinabove, but such prior art stroke adjusting devices have not been found to be wholly satisfactory. For example, one suggestion was to place adjustable stop means in the form of elongated screws or the like on the upper platen, but again this was a coarse type of adjustment device and it failed to take into account platen deflection under load. Another example of a prior art stroke adjusting device utilized limit switch signals which controlled a hydraulic flow arrangement to and from the cylinder and piston assembly, but again this system was not accurate enough for precision compacting of articles.

By far the most common type of prior art stroke ad- 3,407,710 Patented Oct. 29, 1968 justing device, and one which has heretofore been used with some success, is a mechanical stop means coupled to the piston itself. That is, in the conventional cylinder and piston assembly, the piston rod extends between the piston and the platen to be moved. To form a mechanical stroke stop for this arrangement, an auxiliary rod would extend from the other face of the piston and would carry a stop nut or the like at the outer end thereof. One disadvantage which has been found with this system is that the length of the auxiliary rod between the piston and the maximum adjusted position of the stop nut must be at least equal to the length of the cylinder. Then, the threaded portion at the outboard end of the auxiliary rod along which the stop nut can be adjusted, must be somewhat substantial in length, and as a result, to use a stop arrangement of this type, the overall assembly was approximately triple the normal cylinder length. Naturally, this meant that if the assembly was mounted on the top of a hydraulic press, extra clearance space had to be provided and the adjustment had to be accomplished quite high above the machine. However, another and perhaps even more serious disadvantage resided in the fact that the provision of the auxiliary rod changed the effective surface area of the piston. That is, the normal piston is circular in crosssection and hence has a circular face of a preselected area upon which the pressure can act to move the piston rod and the attached platen. However, when the auxiliary rod is attached to this circular piston face, the effective surface area thereof is converted from a circular shape to an annular shape. Therefore, to get the same force output acting upon the platen, it is necessary to increase the bore of the cylinder until the surface area of the annulus is the same as the surface area of the circular piston would have been before the auxiliary rod was connected thereto. The larger the bore of a cylinder becomes, the more expensive the cylinder and piston assembly is, and as a result, it is desirable to utilize the minimum cylinder bore consistent with the forces desired to be produced.

As a result of the foregoing consideration, it will be appreciated that prior art attempts to provide an adjustable stop means for limiting the stroke on a hydraulic press have not been altogether satisfactory. One of the principal objects of the present invention is to overcome the difficulties and deficiencies associated with such prior art forms of stroke adjusting devices and to provide in their stead, a new and improved stroke adjusting mechanism. However, it should be appreciated that the principles of the present invention are in no way limited to stroke adjusting devices which are useful on hydraulic presses, but instead, are applicable to any situation wherein the stroke of a hydraulic unit is to be selectively adjusted.

Another object of the present invention is to provide a stroke adjustment mechanism which operates in a simple and efiicient manner and which can be easily controlled, yet which is highly accurate and reliable.

Another object of the present invention is to provide a stroke adjusting device which can readily be adapted to already existing cylinder and piston assemblies without the need for increasing the bore size of the cylinder and without decreasing the effective forces exerted thereby.

Another object of the present invention is to provide a stroke adjusting device which is particularly adapted for use on a hydraulic press for compacting materials and which can very accurately and reliably control the degree of compaction of such materials, while assuring that the tools or punches utilized in such a press cannot inadvertently crush against one another, even in the total absence of a supply of material.

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 thereof.

Referring to the drawings:

FIGURE 1 is a longitudinal sectional view of the stroke adjusting means of the present invention in combination with a conventional hydraulic cylinder and piston assembly; and

FIGURE 2 is a transverse sectional view taken substantially along the line 22 of FIGURE 1.

In accordance with the principles of the present invention, and as shown in FIGURE 1, there is provided a hydraulic unit in the form of a conventional hydraulic cylinder and piston assembly generally designated and a control means or stroke adjusting means generally designated 12 for selectively adjusting the stroke of the assembly 10.

The conventional cylinder and piston assembly 10 includes an elongated cylinder body 14 having a pair of

opposed end members

16 and 18. A series of spaced tie rods 20 extend through the

end members

16 and 18 and when the nuts 22 at the outer ends of these tie rods are tight ened, they tend to draw the

end members

16 and 18 toward one another. Suitable sealing means, such as O-rings 24 or the like, can be utilized to prevent any leakage from occurring between the cylinder body 14 and the end members.

The end member 16 is provided with a hydraulic port 26 and the end member 18 is provided with a similar hydraulic port 28. These hydraulic ports are adapted to be connected through suitable piping or the like which forms no part of the present invention, to a source of prossurized fluid. This pressurized fluid, which can be any suitable form of hydraulic fluid, is introduced through the ports to the interior of the cylinder body 14. Flow through the

ports

26 and 28 is reversible, as indicated by the arrows juxtaposed thereto.

A piston 30 is disposed Within the cylinder and includes a pair of opposed substantially

parallel faces

32 and 34. The maximum position which the piston can be moved is from a position whereat the face 32 contacts the end member 16 to an opposite position whereat the face 34 contacts the end member 18. The total amount of this movement is regarded as the stroke of the assembly 10.

A piston rod 36 is afiixed to the face 34 of the piston and extends or projects beyond the end member 18 through a central opening formed therein. A suitable sealing means, such as a bushing 38 or the like, is mounted in this opening in the end member 18 to prevent the hydraulic fluid in the cylinder from leaking therepast. The piston rod 36 can carry at its outboard end, an enlarged plate or flange 40 which is provided with suitable bolt holes. Thus, any member to be moved can be suitably attached to this plate. As designated in phantom lines in FIGURE 1, a suitable member M in the form of a platen or the like can be attached thereto. It will thus be appreciated that any increment of movement of the piston 30 within the cylinder will cause a corresponding increment of movement of the member M. Hence, as the stroke or degree of movement of the piston 30 is selectively varied, the degree of movement of the member M is likewise varied. When the movement of the piston 30 is stopped, the movement of the member M is likewise stopped.

Referring now to the stroke adjusting means 12, it will be seen that the same includes a casing 42 coupled with the cylinder and piston assembly 10. Specifically, the easing can be attached between the end member 16 and still another end member 44, and suitable tie rod means 46 can be utilized to connect the two together. When the nuts 48 at the end of these tie rods 46 are tightened, the end member 44 is drawn toward the end member 16 and the casing 42 is firmly maintained in position. An enlarged bore 50 and counterbore 52 extend through the end member 16 so that the interior of the cylinder 14 communicates with the interior of the casing 42. Thus, the hydraulic cylinder supply through the port 26 not only flows into the cylinder 14 but also flows into and fills the interior of the casing 42. Suitable sealing means, such as O-rings 54 or the like, are utilized to prevent such fluid from leaking between the casing 42 and the

end members

16 and 44.

A threaded shaft means generally designated 56 is disposed within the casing 42 and is coupled to the face 32 of the piston 30. In the form shown in FIGURE 1, the means 56 includes a small unthreaded stub shaft 58 affixed to the face 32 of the piston and having a threaded recess 60 at the outer end thereof. The threaded shaft itself includes an axially elongated shaft means 62 carrying screw threads 64 on the exterior thereof, and a reduced diameter portion 66 at one end thereof which threads into the recess 60. The opposite end of the shaft 62 can carry a flat end plate 68. The diameter of the stub shaft 58 and the threaded shaft 62 is less than the diameter of the bore 50 so that the same will not interrupt fluid cross flow between the casing 42 and the cylinder 14. However, by providing the expedient of a separate threaded shaft 62 and stub shaft 58, it is possible to use various different types of threaded shafts 62 having different screw threads 64 thereon. In the preferred embodiment of the invention, the screw threads 64 are of the buttress type arranged to transmit power unidirectionally toward the piston 30.

A nut 70 is mounted upon the threaded shaft 62 and is movable axially therealong when such nut and shaft are rotated relatively to one another. That is, as can be seen, the nut 70 is provided with a buttress threaded internal bore which cooperates and meshes in interengagement with the screw threads 64 on the shaft 62. The nut 70 includes at least one opening means therein, and in the illustrated form of invention, as can best be seen in FIGURE 2, is provided with two slots or channels 72 along the periphery thereof.

The control means 12 further includes a nut engaging means disposed Within the casing 42 and generally designated 74. This nut engaging means includes an axially elongated sleeve 76 disposed in surrounding relationship to the threaded shaft 62. The sleeve 76 carries a pair of internal ribs 78 which extend along the length thereof, and as will be seen in FIGURE 2, such ribs 78 fit within the channels 72 in the nut 70. The fit between the channels 72 and the ribs 78 is a relatively loose one which permits the nut to be reciprocated or moved axially relative to the sleeve, but which prevents rotation of the nut 70 relative to the sleeve 76.

The sleeve 76 also includes an end face 80 disposed adjacent the end face 68 on the threaded shaft 62 but in spaced relation thereto. The nut engaging means 74 further includes a projecting portion in the form of a shaft 82 which projects through the end member 44 and beyond. A suitable seal means in the form of a housing 84 having various sealing rings surrounds the shaft 82 as the same extends through the end member 44. In this manner, the hydraulic fluid is prevented from leaking through the end member 44. To assure a complete circulation of hydraulic fluid within the casing 42, both interiorly and exteriorly of the sleeve 76, an air vent 86 is provided in the face 80 of the sleeve, a similar air vent 88 is provided in the end member 44, and an air vent plug 90 is mounted therewithin. Thus, any air trapped within the control means 12 will be expelled.

To continue with the description of the adjusting means portion of the nut engaging means 74, the projecting shaft 82 has a reduced diameter portion upon which a suitable sprocket 92 is mounted. This sprocket is held in position by means of a locking nut 94. Although not shown, this sprocket can be engaged with a conventional chain drive which can be operated by means of a hand wheel or the like. It will, of course, be appreciated that rotation of the sprocket 92 by the chain drive 'will in turn effect a rotation of the sleeve 76. Finally, it will be seen that a collar 96 is mounted on the lower end of the sleeve 76 for the purpose of preventing the sleeve from tilting or otherwise canting within the casing.

With the aforementioned description in mind, the operation of the present invention can now be described. It will, of course, be appreciated that the nut 70 serves as the adjustable stop element. The position of this nut axially along the length of the threaded shaft 62 is adjusted through operation of a nut engaging means. Specifically, the sprocket 92 is suitable rotated to effect a concurrent rotation of the sleeve 76. As the sleeve rotates about the threaded shaft 62, the ribs 78 in engagement with the nut 70 cause the nut to be likewise rotated. Such relative rotation between the nut and the threaded shaft causes the nut to move axially along the shaft, either upwardly or downwardly, as desired. When the nut finally reaches the selected axial location along the threaded shaft 62, rotation of the sprocket 92 is terminated and rotation of the sleeve 76 is likewise terminated. Then, hydraulic fluid can be introduced through the port 26 to move a piston 30 within the cylinder 14. It will be understood and appreciated that the pressure of such hydraulic fluid acts upon the face 32 of the piston which is annular in formation due to the presence of the stub shaft 58, but it 'likewise acts upon the end 68 of the threaded shaft. Hence, the total fluid pressure applied is equal to the cross-sectional area of the piston 30, and as such pressure is applied, the piston starts to move downwardly in the embodiment illustrated in FIGURE 1. As such piston moves downwardly, the threaded shaft 62 moves axially and the nut 70 carried thereby likewise moves axially. Since the only engagement between the nut 70 and the nut engaging means 74 is the rib and channel engagement best illustrated in FIGURE 2, axial movement of the nut is not prevented. Thus, such nut will move downward until it contacts a stop means against which it abuts. In the illustrated form of invention, the stop means is the shoulder 98 of the counterbore 52. When the nut abuts against that surface, further axial movement is prevented, and accordingly, movement of the cylinder and piston assembly is stopped.

It will, of course, be appreciated that other suitable forms of stop means can be utilized. The only purpose for providing the counter-bore 52 is to reduce the total excess height needed for the stop adjusting means 12. If desired, such counterbore can be entirely eliminated so that the nut 70 would abut against the level top surface of the end member 16. :In fact, if desired, an inwardly projecting flange could be provided from the casing 42 itself, with such flange extending beneath the lower end of the sleeve 76. In such event, this flange would serve as the stop means against which the nut 70 abuts. It will also be seen and appreciated that in the preferred form of embodiment of the invention, the piston rod 36, the threaded shaft means 56 and the projecting shaft 82 for the adjusting means are all coaxially aligned.

After reading the foregoing detailed description, it will be apparent that the objects set forth at the outset of the specification have been successfully achieved by the present invention. Accordingly, what is claimed is:

1. In the combination of (1) a hydraulic unit including a cylinder means, a piston movably mounted within said cylinder means and a piston rod coupled with one face of said piston and adapted to be connected with a member to be moved, the movement of said member being controlled by the stroke of said hydraulic unit, and (2) a control means for adjusting the stroke of said hydraulic unit; the improvement in said control means comprising:

a casing coupled with said cylinder means and communicating with the interior thereof whereby hydraulic fluid introduced into said cylinder means will likewise be introduced into said casing;

a threaded shaft disposed within said fluid in said casing and coupled with said piston rod;

said face coupled with said piston rod;

a nut mounted upon said threaded shaft and being movable axially therealong through relative rotation between said nut and said threaded shaft;

nut engaging means disposed within said fluid in said casing and engaged with said nut to normally prevent rotation thereof while permitting axial movement thereof as said threaded shaft is axially moved due to movement of said piston;

said nut engaging means including adjusting means for rotating said nut engaging means and for thereby rotating said nut to adjust the position thereof axially along said threaded shaft; and,

stop means interposed in the path of axial movement of said nut whereby, when said nut abuts thereagainst, further axial movement of said threaded shaft is prevented and hence the movement of said piston and piston rod is terminated;

said abutting of said nut against said stop means thereby limiting the stroke of said hydraulic unit and the axial position of said nut along said threaded shaft serving to adjust said stroke.

2. The improvement defined in claim 1 wherein said nut engaging means includes a sleeve means rotatably mounted within said casing.

3. The improvement defined in claim 2 wherein said sleeve means surrounds said threaded shaft and said nut and includes at least one portion engageable with said nut.

4. The improvement defined in claim 3 wherein said nut includes at least opening means therein and wherein said portion is disposed within said opening means.

5. The improvement defined in claim 4 wherein said opening means is a groove in the periphery of said nut and wherein said portion is a rib extending along the interior of said sleeve means.

6. The improvement defined in claim 1 wherein said nut engaging means includes a projecting portion extending exteriorly of said casing to form at least a part of said adjusting means.

7. The improvement defined in claim 6 further including a collar means mounted upon said projecting portion whereby rotation of said collar means rotates said nut engaging means.

8. The improvement defined in claim 6 wherein said piston rod, said threaded shaft and said projecting portion are coaxially aligned.

9. The improvement defined in claim 1 wherein the end of said threaded shaft remote from said piston is free from contact with said nut engaging means whereby said hydraulic fluid can exert a pressure force thereagainst so that the eifective pressure area of said piston is not reduce-d through coupling of said threaded shaft thereto.

10. The improvement defined in claim 1 wherein said cylinder means includes end members, wherein said casing means abuts against one of said end members and wherein at least a portion of said one end member forms said stop means. 1

References Cited UNITED STATES PATENTS 1,325,006 12/ 1919 Deansley 92-13 1,571,044 1/1926 De Costa 92-13 X 2,346,868 4/1944 Perry 92-13 X 2,640,325 6/ 1953 Haller 9213 2,674,098 4/ 1954 Taylor 9213 X 2,761,424 9/1956 Hopkins 92-13 X 3,136,227 6/1964 Williams 92-63 FOREIGN PATENTS 739,140 10/ 1955 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner. I. C. COHEN, Assistant Examiner.