US3160078A - Power cylinder - Google Patents

Description

Dem 1954 M. J. HIEMSTRA ETAL 3,160,078

POWER CYLINDER :5 Sheets-Sheet 1 Filed April 1, 1963 /////////vfl////////////// r m m 4 0 W W? W JJJ If 7 7V .4 WM ww MA) w 1964 M. J. HIEMSTRA ETAL 3,160,078

POWER CYLINDER Filed April 1, 1963 3 Sheets-Sheet 2 FIG. 5.

INVENTORS fldkI/l/V J. H/EMSTKA ALBEFT J. VM/DEE-SZOOT FIG. 4.

Dec. 8, 1964 M. J. HIEMSTRA ETAL POWERv CYLINDER .3 Sheets-Sheet 3 Filed April 1, 1963 United States Patent Ofiice 3,160,078 POWER CYLINDER Marvin .l. Hiemstra and Albert .5. Vander Sloot, Grand Rapids, and Harry J. Johnson, Kalamazoo, Mich, as-

signors to Mechanical Power Corporation, Grandville,

Mich, a corporation of Michigan Filed Apr. 1, 1963, Ser. No. 269,664 12 Claims. (will. 92-14) This invention relates to a fluid cylinder that is lockable against reverse movement, and especially to a fluid cylinder having locking means cooperable with power amplification means.

There has existed in the fluid cylinder art, a very significant need for a fluid cylinder with automatically actuating, mechanical locking means against reverse movement, until reverse fluid pressure is applied.

Also, it would often be extremely advantageous to be able to effect a multiplied pressure over line pressure at the er1d-of the shaft stroke, .to apply a final greatly increased pressure as the object is contacted. One typical example is to tightly squeeze parts to be resistance welded after the parts have been contacted by the electrode tip on the cylinder and another tip. Most prior cylinders have only a small power amplification, i.e. two or three times normal, and moreover, have no locking means at all to positively lock up the assembly during this amplification stroke.

To provide a force multiplying cylinder that also locks at the end of its stroke, and which would have a long operating life, would be especially desirable.

Two prior devices have been invented which have large amplification, eg, at least thirty to forty times normal, and positive locking against reverse movement. These are shown and claimed in US. Patent 2,625,910, now Reissue 25,334, and US. patent application Serial No. 200,396, filed June 6, 1962. This present invention is an improvement over these prior inventions.

It is the main object of this invention to provide a greatly simplified locking mechanism for a fluid cylinder to automatically lock against reverse movement of the shaft, even when coupled with power amplification mechanism, with reverse movement being possible only by reverse fluid line pressure. The locking mechanism utilizes no special pivots, levers or other complex mechanism with short life, but rather achieves the locking action by a tilting or cocking of a simple annular nut. The greater the pressure applied to the locking nut during amplification, the greater the locking action that occurs. Yet, it remarkably, quickly, and dependably reverses its movement to unlock the mechanism under normal reversed fiuid line pressure, even though releasing a locking pressure many times greater than this line pressure. The locking mechanism can be manufactured at a nominal cost. Moreover, the assembly of the cylinder is simple.

It is another object of this invention to provide such a power amplifying fluid cylinder that has an exceptionally long useful life.

These and many other objects of this invention will be apparent upon studying the following specification in conjunction with the drawings in which:

FIG. 1 is a side elevational sectional view through the fluid cylinder employing the novel locking mechanism in combination with a power amplification mechanism, with the device being shown retracted;

FIG. 2 is an enlarged side elevational view of the special locking nut or ring used in this invention;

FIG. 3 is an enlarged sectional view of a modification of the ring in FIG. 2;

FIG. 4 is an enlarged sectional view of the camming element in the assembly of FIG. 1;

FIG. 5 is a sectional elevational view of the cylinder shown in its extended state after power amplification and with the device locked against reverse movement;

FIG. 6 is a fragmentary sectional enlarged view of a modified cylinder assembly;

FIG. 7 is a sectional enlarged view of the locking not utilized with the assembly of FIG. 6;

FIG. 8 is an end elevational view of the locking nut in FIG. 7; and

FIG. 9 is a fragmentary enlarged perspective view of still another form of the inventive cylinder assembly shown in fragmentary form.

Basically, the inventive cylinder involves a piston and shaft assembly shiftable over a fixed rod, and a cocking lock out or sleeve that tilts and lockingly engages the fixed rod after the shaft has struck an object and applied an amplified pressure.

Referring more specifically to the drawings, the first form of the inventive power cylinder 10 as shown in FIGS. 1 and 5 includes a housing formed by an elongated outer cylinder 12 and a pair of end caps 14 and 16. Within the housing are shiftable, hollow shaft 18, serrated rod 2i) aifixed to end cap 16, a piston 22, a carnming sleeve 24 attached to the piston assembly by threads 25 (FIG. 4), radially shiftable expander rollers 28, a tiltable cocking nut or ring 39, and an intermediate abutment sleeve 26. The combination of shaft 18 and sleeve 26 may be thought of as an axially expandable shaft assembly.

The housing is retained in its assembled relationship by press fitting or screwing cylinder 12 onto the annular shoulder of end cap 16, and attaching end cap 14 on cylinder 12 by an annular deformable key 32.

End cap 16 includes a suitable air pressure inlet 46 and an outlet 44. Both communicate with passageway 48 into the central portion of the cylinder. End cap 14 has an inlet port 4i, and an outlet port (not shown).

Rod 2i has serrations such as threads along its periphery. It is threadably engaged with end cap 16 on the central axis thereof, by a shank 50. 1

Shaft 18 is hollow and is adapted to reciprocate back and forth over rod 20 and out end cap 14 on a bushing 52 in the end cap. The shaft is sealed to the end cap by an O ring 54 or its equivalent. The inner hollow surface 56 of shaft 18 is hexagonal in configuration. It is in sliding contact with the enlarged hexagonal end 58' of serrated rod 20. The end of the shaft protruding from the cylinder includes a threaded socket 69 for attachment of any suitable fitting, depending on the use of the cylinder. The inner end of shaft 18 has an enlargement 62 which projects radially outwardly to form a shoulder. The annular surface 64 on the inner end of this shoulder is tapered to cause a plurality of rolling elements 28 such as balls to be forced radially outwardly when axial force is applied to the shaft 18. On the opposite side of balls 28 is an annular, axially elongated sleeve expander 26 having a hollow interior to move back and forth over serrated rod 20. The front surface 68 of sleeve 26 is tapered in the opposite direction as the facing surface 64 of shaft 18 to cooperate therewith and cause the balls to be biased outwardly. Inward radial pressure on the balls 28 therefore causes axial expansion and spreading of the shaft 18 and sleeve 26. This sleeve 26 constitutes an abutment to activate the cocking nut 30 as will be understood fully hereinafter.

Cooking nut 30 includes a cylindrical central opening enabling the nut to move smoothly back and forth over serrated rod 20. The nut also includes an annular flange which projects radially outwardly to provide a rear surface 70 responsive to line pressure introduced through passage 48. This surface 70 is purposely cupped, i.e. has a radially inward taper, to assure travel of the nut Patented Dec. 8, 1964 i '3 A l a the nut as a pushing element for the piston assembly;

On the front end of the nut, a fulcrum is created between one small portion of the nut and the adjacent rear axial surface of sleeve 25. This fulcrum 72 is preferably created by causing this front segment of'the axial surface of the nut-to project axially forward beyond the remaining portions of that surface 74 of the nut. Thus, this fulcrum point contacts the rear surface of sleeve 26 prior to contact of the remaining portions of axial surface 74 when the nut is axially aligned with the rod. Alternatively, the rear surface of sleeve 26 could be made to project at one portion thereof, to achieve the same result.

Further, any combination of projections can be formed between the two faces as long as a fulcrum point is created causing the nut to tilt when reverse axial force is applied to the nut by sleeve 26, and forward axial force is applied to the nut by air pressure. The inner surface to this nut includes two-beveled portions 89 and 82 respectively, having serrations to interengage serrated rod 29 when the nut is tilted. Portion 8th is on the same side of the nut as the fulcrum but on the opposite end of the nut. Portion 82 is on the opposite side, but on the same end as the fulcrum. ,They are therefore diagonally opposite each other. In FIGS. 2 and 3 the detailed construction of this nut is shown in two variations. In FIG. 2,.the forwardly projecting surface portion 73 forming the fulcrum at 72 is essentially an axial tang especially machined on the forward axial end of nut 30. In FIG. 3,

the fulcrum point of modified nut 30a is formed by tapering the entire axial surface 74 of the nut. Either could be used. Other physical variations of these will also be obvious. Preferably, the angle of taper is approximately 11 but this may be varied to assure optimum looking on both ends of the cocking nut depending upon the size of the cylinder and other factors. The bevel of surfaces 80 and 82 is preferably about 2 /2 The front surface of flange 71 of cocking nut 30 engages the rear inner end of camming sleeve 24. This sleeve, as it slides in the cylinder, is sealed to the inner wall of the cylinder by an O ring 96. This camming sleeve includes an axially-extending, radially-varying, inner peripheral camming surface 92' which tapers from a maximum diameter at its forward end adjacent piston 22 to a minimum diameter at its rearward or opposite end. It includes afiat inner surface portion 94 adjacent the maximum diameter end, and a second flat surface 96 adjacent. the small diameter end. The forward or larger diameter end of the camrning sleeve 24is engaged, preferably threadably, with piston 22.

The piston is sealed to shaft 18 by an O ring seal 98 or its equivalent. Also, the piston is releaseably engaged to the shaft 18 preferably by a plurality of balls 100 biased radially inwardly by spring 102, into engagement with a cooperating groove 104 and the external periphr cry of shaft 18. During normal travel of the piston and camming sleeve therefore, the shaft 18 is also moved therewith. However, upon the occurrence of the shaft strik-. ing an abutment with considerable resistance to move-' ment, the releaseable engagement causes disengagement of the piston from the shaft by outward shifting of the balls ltlttagainst bias of springs 102, allowing the piston to slide over the shaft. Conceivably, the positive engagement formed by these spring biased detents may be eliminated since shaft 18 is forced outwardly by pushing of nut '30 against sleeve 26, balls 28, and the shaft. Return of the shaft from its extended position is by contact of piston 22 on the inner shoulder of the shaft.

Operation During normal operation, when the cylinder is in its retracted state, it assumes the position illustrated in FIG. 1. Upon the introduction of a pressurized fluid such as air into inlet 46 and passageway 48, the air pressure on the cupped face 70 forces nut 39 to travel axially in the cylinder over the fixed serrated rod 20, away from end cap 16 and toward end cap 14. As this nut or ring 39 moves to the right (as illustrated in FIG. 1) it normally stays coaxial with the rod and forces the entire assembly to move with it. Its shoulder pushes the camming sleeve, and its fulcrum point pushes buttress expander sleeve 26. Since the forward end of the camming sleeve is threadably attached to piston 22, piston 22 also shifts to the right. Likewise, the connection at 109 between piston 22 and shaft 18 causes the shaft 18 to move to the right over the hexagonal enlarged head 58 of fixed shaft 20. Part of the shifting force on shaft 18 is applied by sleeve 26 and balls 28. This shifting continues until the outwardly projecting end at 60 of shaft 18 strikes an object shown in phantom at 13in FIG. 5.

Assoon as the object is struck, resistance to further shaft movement occurs, causing the shaft, the balls 28, the sleeve 26 and the nut 30 to stop. Since air pressure continues on cupped face of nut 30, and since nut 39 abuts sleeve 26 on a fulcrum point 72, the nut tilts as shown in FIG. 5 so that it no longer is co-axial with the other elements. Its serrated, beveled, portions and 82 interengage the serrations on rod 20. The air pressure also causes the piston and its attached camming sleeve 24 to continue to move. If balls are used, they move out of the groove 99 on shaft 18 to disengage the piston from the shaft. Movement of cam sleeve 24 causes the radially-varying camming surface 92 to shift the cam follower balls 28 radially inwardly as shown by the arrows in the drawings. This forces shaft 18 and sleeve 26 axially apart to spread them due to the inwardly converging tapered surfaces 64 and 68. Since sleeve 26 is locked against rearward movement by nut 30, shaft 18 must move forwardly against the object 13. The relatively small taper of surface 92 and the large axial movement of sleeve 24 to cause a small amount of balls 28 and a small axial movement of shaft 18 creates a tremendous mechanical advantage with a power amplification of 30, 40, 50 or more times. The specific amount of amplification can be controlled. As soon as the fiat, smaller diameter surface 96 moves over. balls 28 (FIG. 5) maximum power amplification exists. Due to this flat 96, there is no tendency for the sleeve to reverse. It has been found that the cocking nut 30 repeatedly, and without fail, causes a positive locking action even though the power amplification becomes extremely large, and evenafter many thousands of repeated strokes. No matter how large the reverse force on shaft 60 is, this merely locks the nut tighter since it tends to pivot harder around its fulcrum 72 to engage the serrated portions with even greater force. Reverse shifting is caused only by reverse line pressure through inlet 49 in forward end cap 14. Only ordinary line pressure is required to reverse the entire mechanism, even though the applied pressure on the extended shaft is many times greater. Reverse line pressure causes piston 22 to move from the position illustrated in FIG. 5 and back over the shaft 18,'thereby also shifting camming sleeve 24 reversely and allowing the follower balls 28 to be shifted outwardly. When the rear face of camrning sleeve abuts the shoulder of nut 30, it rotates it into its aligned relationship with serrated rod 20, causing disengagement of serrated portions of 80 and 82 therefrom, allowing the nut to shift its original coaxial position illustrated in FIG. 1. The piston engages shaft 18 when it reaches flange 62 to shift the shaft, the balls, sleeve 26, and nut 30 back to their original positions for another stroke.

The novel structure operates extremely rapidly. It has been found to have an extended, useful life with minimal wear occurring since there are no hinges, pivots, or delicate springs to wear out. The heart of the invention, cocking nut 30, is simple to machine, has no moving parts other than its tipping action, has a simple operational characteristic, and is foolproof in operation. The novel cylinder can be used for countless applications where power amplification of many times the original line pressure is needed, and where the unit must be locked in the power amplification stroke until it is desired to reverse it.

The tilting lock ring or nut is preferably .used in combination with the force multiplication mechanism. However, conceivably the nut could be positioned on the serrated rod directly behind the inner rearward end of the hollow shaft, without sleeve 26 and balls 28 in between. Thus the fulcrum point would occur between the nut and the shaft itself to lock the shaft against rearward movement upon abutting object 13 and stopping. Therefore, the broader aspects of this invention include this modification.

Modifications In FIGS. 6 and 8 a modified assembly is illustrated. This modification employs a cocking spring 110 and a cocking cam surface 112 to aid the cocking nut 30 in its tilting action into locking engagement with the fixed rod 20.

The outer cylinder construction is the same, including housing 12 and end caps 14 and 16. Threadably engaged to cap 16 is the centrally positioned, fixed serrated rod 20 over which the piston assembly reciprocates under fluid pressure. Gaseous inlets 48 (and 49) are made to both ends of the cylinder. Piston 22 is releasably engaged with annular hollow shaft 18 either with or without a spring biased ball detent connector 102.

Roller elements 28 are again positioned between the flared end 62 of shaft 18 and intermediate sleeve 26 to spread these elements apart when shaft 18 abuts something and piston 22 with camming sleeve 24 ride forwardly to depress balls 28 radially inwardly.

This modified assembly does not rely upon a cupped rear face on cocking nut 39' to tilt the nut after the rear end of camming sleeve 24 shifts forwardly, but rather employs a combination of two added features. More specifically, as the radially protruding shoulder 114 of sleeve 24 moves forwardly with release of piston 22 from shaft 18, the shoulder 114' slides over sloped camming surface 112 and forcefully tilts the nut. Also, as balls 28 move inwardly and spread shaft 18 and sleeve 26, tension coil spring 110 is expanded since its forward hook end 120 is connected in front of shoulder 62 of shaft 18, and its rear end 122 is secured by a set screw 118. As can be seen the spring extends from passageway 126 in nut 39', through passageway 128 in sleeve 26, and through passageway 130 in shaft 18. Its location on one side of rod 2 1 causes it, when placed in tension, to force nut 30 to tilt about fulcrum 72 between the nut and sleeve. Return of the piston and camming sleeve forcefully aligns the nut again.

It has also been found that the engagement of teeth 80 with serrated rod 20 proceeds very smoothly and without a slamming action when cut- outs 132 and 134 are provided in the interior wall of annular nut 30 adjacent teeth 80. These help prevent any skipping of teeth with interengagement of the nut and rod.

In another modification illustrated in FIG. 9, nut 30 includes a spring biased uncocking means 150. This means include a passageway 152 retaining a first ball 154 biased by compression spring 156 held by set screw 158, and a second ball 160 in a portion of the passageway that emerges at an angle of about 20 to 30 with respect to a plane perpendicular to the axis of the assembly. This second ball protrudes out of nut 30 to contact shoulder 114 of camming sleeve 24. This creates a bias on the sleeve tending to uncock the nut away from rod 20. Thus when the piston is not extended, the nut is biased out of locking engagement. When the piston and camming sleeve shift under air pressure, the

nut is no longer so biased since shoulder 114 is not in contact with ball 160. Upon the return stroke of shoulder 114, the nut is forcefully biased away from rod 20.

It is conceivable that certain other modifications may be made in the structure illustrated, using the inventive principles taught and without departing from the invention. These obvious modifications are deemd to be part of this invention, which is to be limited only by the scope of the appended claims and the reasonably equivalent structures to those defined therein.

We claim:

1. In a fluid cylinder having a housing, a shiftable piston and shaft assembly, and a central rod fixed in the housing, a locking nut having first surface portions responsive to fluid pressure in one end of said housing to shift over said rod under fluid pressure with the piston in one direction, and second surface portions responsive to reversing fluid pressure in the opposite end of said housing to shift in reverse direction; said nut having a fulcrum point on said assembly on one side of said rod to cause said nut to tilt when said assembly stops, and having a grasping surface to engage said rod upon tilting; said nut, when tilted and engaged, preventing reverse movement of the shaft by mechanical force, whereby the piston and shaft assembly are reversed only when reverse fluid pressure is applied.

2. The cylinder in claim 1 wherein at least one of said nut and rod has serrations.

3. The cylinder in claim 1 wherein both said nut and rod are serrated for inter-engagement.

4. In a fluid cylinder having a'housing, a shiftable piston and shaft assembly, and a central rod fixed in the housing, a tiltable locking nut having first surface portions responsive to fluid pressure in one end of said housing to shift over said rod under fluid pressure with the piston in one direction, and second surface portions responsive to reversing fluid pressure in the opposite end of said housing to shift in reverse direction; said nut having a fulcrum point on said assembly on one side of said rod to cause said nut to tilt when said assembly stops; said nut having a central opening to normally slide smoothly over said rod, and having a grasping surfaceon opposite ends of said opening to positively engage said rod upon tilting, thereby locking said assembly against reverse movement except by reverse fluid pressure.

5. The cylinder in claim 4 wherein the rearward axial annular end face of said nut is concave to assure movement of said nut under air pressure.

6. The cylinder in claim 4 wherein a tension spring extends between said nut and said piston and shaft assembly, on the opposite side of said rod from said fulcrum, to exert a tilting bias on said nut.

7. A fluid cylinder comprising: a housing, including end caps; fluid port means in said end caps; a rod fixed centrally in said housing; a piston adapted to reciprocate over said rod under fluid pressure; an axially-extending, camming element adapted to reciprocate with said piston, and including a radially-varying camming surface; a hollow shaft extending through one of said end caps and operably associated with said piston; an annular sleeve adjacent the inner end of said shaft; cooperative tapered surface portions between said sleeve and inner shaft end; radially shiftable cam follower means positioned adjacent said tapered surface portions to spread said sleeve and shaft when shifted radially inwardly by said camming surface; an annular, locking element around and normally out of locking engagement with said rod; and said locking element, when stopped against said sleeve being tiltable to engage said rod and prevent reverse axial movement of said sleeve, whereby further radial shifting of said cam follower means applies amplified forward axial force to said shaft.

8. The cylinder in claim 7 wherein said locking element comprises: a cockable lock ring around said rod and adjacent the rear, inner end of said sleeve, includes '2 an axial extension between said ring and sleeve causing a fulcrum contact therebetween, and includes inner serrations to engage said rod when said ring is tiltably cocked.

9. The cylinder in claim 7 wherein said ring includes a sloping cocking cam engageable by said camming sleeve to forcefully cock said ring into locking engagement with said rod. a

10. The cylinder in claim 7 wherein said ring has an annular concave rearward face responsive to air pressure to shift the piston and shaft assembly forward.

11. The cylinder in claim 8 wherein said ring includes cutout portions against said inner serrations to facilitate a smooth engagement with said rod.

12. A fluid cylinder comprising: a housing including end caps; fluid port means in said end caps; a serrated rod fixed centrally in said housing; a piston adapted to reciprocate over said rod under fluid pressure; an axiallyextending, carnming element adapted to reciprocate with said piston, and including a radially-varying camrning surface; a hollow shaft extending through one of said end caps and operably associated with said piston with a releaseable connecting means; an axially shiftable sleeve adjacent the inner end of said shaft; cooperative tapered surface portions on the facing ends of said sleeve and shaft; radially shiftable rollers positioned between said tapered ends to spread said sleeve and shaft when shifted radially inwardly by said camming surface; an annular locking nut adjacent the end of said sleeve opposite its tapered end and adapted to shift over said rod under fluid pressure with the piston; said out having a fulcrum point on said assembly on one side of said rod to cause said nut to tilt when said assembly stops, and having inner serrations to engage said rod upon tilting, whereby said piston and shaft assembly are locked against return movement until reverse fluid pressure is applied, and said piston and camrning surface adapted to continue moving after said nut has tilted to shift said rollers inwardly and create a power amplification on said shaft by spreading said shaft from said sleeve.

No references cited.

Claims (1)

1. IN A FLUID CYLINDER HAVING A HOUSING, A SHIFTABLE PISTON AND SHAFT ASSEMBLY, AND A CENTRAL ROD FIXED IN THE HOUSING, A LOCKING NUT HAVING FIRST SURFACE PORTIONS RESPONSIVE TO FLUID PRESSURE IN ONE END OF SAID HOUSING TO SHIFT OVER SAID ROD UNDER FLUID PRESSURE WITH THE PISTON IN ONE DIRECTION, AND SECOND SURFACE PORTIONS RESPONSIVE TO REVERSING FLUID PRESSURE IN THE OPPOSITE END OF SAID HOUSING TO SHIFT IN REVERSE DIRECTION; SAIDNUT HAVING A FULCRUM

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