Double Acting Fluid Pressure Operable Cylinder Device

Abstract

A double-acting fluid pressure operable cylinder device including both resilient and needle valve means for cushioning the end of the piston stroke against damaging impact thereof with the cylinder head. The resilient member and needle valve are arranged relative to each other so that the resilient member is engaged somewhat in advance of the end of the piston stroke to commence the cushioning effect but not so to prevent free-flow exhaust of fluid pressure from the cylinder chamber until just before the end of the piston stroke when the resilient member is effective for sealing off the unrestricted exhaust path and limiting final exhaust at a restricted rate via an adjustable needle valve.

Description

BACKGROUND OF THE INVENTION

Other known double-acting cylinder devices are provided with sealing members and adjustable needle valve devices at each end of the cylinder, as above noted, each of said sealing members being intended, just before the end of the piston stroke, to interrupt free or direct exhaust of fluid pressure from the pressure chamber almost simultaneously by sealing on both the piston rod projection sliding therethrough and the groove in which the sealing element is disposed, thereby limiting exhaust through a restricted opening of a needle valve for cushioning the piston impact. Since the transitional stage or change-over from direct exhaust flow to restricted flow is simultaneous in nature, adjustment of the needle valve to provide faster rate of exhaust for accelerating retraction of the piston can result in severe piston impact and resulting damage. Moreover, such damaging results may also occur if the sealing member, due to wear resulting from constant frictional sliding contact with the piston rod projection, loses its sealing effect, whereby effective cushioning, which would be limited to the effects of the needle valve only, is lost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a double-acting cylinder device characterized by cushioning means providing positive protection against damages resulting from piston impact at the end of the stroke, said cushioning means being adjustable, without risking loss of maximum cushioning effect, to compensate for misadjustments and wear of the cylinder components.

The invention comprises a double-acting fluid pressure operable cylinder device having pressure chambers on opposite sides of the piston adjacent respective cylinder heads at opposite ends of the cylinder, each of said chambers being subjectable to fluid pressure and relief thereof alternately and in reverse order relative to each other, depending on direction of stroke movement of the piston. Each of the cylinder heads is provided with a coaxial tapered recess for accommodating, at the end of the piston stroke in one direction or the other, respective coaxial cylindrical portions carried by the piston rod adjacent to and on opposite sides of the piston. A resilient annular sealing member of particular cross-sectional area is disposed, with both axial and radial spacing, in respective particularly cross-sectionally shaped annular grooves surrounding the openings of each of the tapered recesses, said sealing member being engageable by the adjacent cylindrical portion, during final movement of the piston stroke, in advance of the end of said stroke for initiating cushioning effect of the piston. Upon engagement of the sealing member by and sliding movement therethrough of the cylindrical portion, said sealing member is expandingly deformed so as to make sealing contact with the bottom of the groove just prior to the end of the stroke, thereby cutting off free-flow exhaustion of fluid pressure from the pressure chamber and diverting such exhaustion at a restricted rate through an adjustable needle valve, with which the degree of cushioning of the piston can be regulated.

The sealing member has a beveled annular portion part of which projects axially out of the annular groove and into the pressure chamber beyond the inner axial limit of the cylinder head, thus permitting the cylindrical portion of the piston to engage said sealing member and provide cushioning effect ahead of its valve action (seating on the bottom of the groove) before the piston reaches the cylinder head.

The single FIGURE drawing is an axial view, in section, of a double-acting cylinder device embodying the invention.

DESCRIPTION AND OPERATION

In the drawing, a double-acting cylinder device designated 1 comprises a cylinder casing 2 and a pair of cylinder heads 3 and 4 secured at opposite ends of the cylinder casing, respectively. A piston 5 and a piston rod 6 are operably disposed in the cylinder casing 2, said rod slidably extending exteriorly of the cylinder device through a guide bushing 7 coaxially secured in cylinder head 3 and in sealingly sliding relation with a sealing ring 8 coaxially disposed in said cylinder head adjacent the inner end of said guide bushing. A scraper or cleaning ring 9, disposed coaxially in cylinder head 3 adjacent the outer end of guide bushing 7, provides cleaning action for the piston rod 6 as said rod moves reciprocably therethrough in contacting relation therewith.

The items described below with which both cylinder heads 3 and 4 are similarly provided are assigned similar reference numerals and primarily described in connection with cylinder head 3 only, it being understood that the description thereof is applicable equally to cylinder head 4 also.

An adjustable needle valve 10 is mounted in cylinder head 3, forming a variable throttle opening 11 between a radial passageway 12 and axial passageway 13 in cylinder head 3. The piston rod 6 has a pair of enlarged cylindrical portions 14 formed coaxially thereon in juxtaposition to the opposite sides of piston 5, respectively. Coaxial recesses 15 are formed in cylinder heads 3 and for accommodating the cylindrical portions 14, respectively, at the end of the piston strokes. Each of the recesses 15, by being connected to a combined inlet-outlet port 16, provides passage means via which fluid pressure may be admitted to or exhausted from the cylinder device. The radial passageway 12 belonging to needle valve 10 also opens radially into recess 15 between the two ends of the recess, said recess tapering from the open end adjacent piston 5 toward its base adjacent sealing ring 8. Recess 15 is concentrically surrounded at the larger open end thereof facing piston 5 with an annular groove 18. Groove 18 is defined by a cylindrical side wall of greater diameter than the opening of recess 15, an internally beveled annular flange 19 extending radially from the end of said cylindrical side wall adjacent piston 5 and having an inside diameter smaller than said cylindrical side wall but greater than said opening, and an annular flat bottom surface 20 radially disposed between the other end of said cylindrical side wall and the periphery of said opening perpendicularly to the axis thereof. The axial boring 13 belonging to the needle valve 10 also emerges into groove 18 at the bottom surface 20.

It should be mentioned that the cylindrical portions 14 can be independent sleeves or bushings, as shown in the drawing, or formed integrally with the piston rod 6 or the piston 5.

An elastic annular sealing member 21 is normally loosely disposed in groove 18 with a small axial clearance, as indicated at C. Sealing member 21 is characterized by a flat sealing surface 22 complementarily adapted for sealingly engaging bottom surface 20 and cooperating therewith as a valve. Sealing member 21 is also provided with a beveled front surface 23 facing the piston 5 and complementary to the internally beveled flange 19. The beveled front surface 23 joins with a toroidal surface comprising the adjacent internal portion 24 of the sealing member 21 which diminishes diametrally toward the juncture with said toroidal surface, said juncture comprising a smallest diameter 26 substantially smaller than the outer diameter of the cylindrical portion 14 which is provided with a beveled leading end 27. A larger diameter 28 of the conical surface 25 adjacent the bottom 20 of groove 18 is essentially the same or somewhat smaller than the outer diameter of the cylindrical portion 14.

Sealing member 21 is further provided with a plurality of angularly spaced and axially disposed through-passageways 29 connecting a cylinder chamber 30 to the axial passageway 13, associated with needle valve 10, via a common annular V-shaped channel 31 formed in the sealing surface 22 of sealing member 21 and intersecting said passageways 29. Moreover, a sealing edge 32 of sealing member 21 makes annular contact with bottom 20 of groove 18 on a circular area between the through-passageways 29 and annular channel 31 and between the central conical surface 25 of the sealing member 21 and said channel 31. Although for purposes of convience, one of the passageways 29 opening to channel 31 appears to be axially aligned with passageway 13, this is not the actual structure. In the actual construction of the invention, none of the passageways 29, for purposes to become evident hereinafter, is permitted to coincide axially with passageway 13.

The mode of operation of the device is described below with reference to the right side of the double-acting cylinder 1;

In the position shown in the illustration, port 16 of the right cylinder head 3 is being supplied with fluid pressure, while the corresponding port 16 on the opposite cylinder head 4 is exhausted. For purposes of convenience, port 16 in cylinder head 3 will be referred to hereinafter as the right port, while port 16 in cylinder head 4 will be referred to as the left port.

Now if the left port 16 is subjected to fluid pressure and the right port 16 exhausted, then piston 5 is moved toward the right. At this point, the compressed air located in cylinder chamber 30 escapes, at first unthrottled, through the space formed between piston rod 6 and central opening 25 of sealing member 21, recess 15 of cylinder head 3, and the combined inlet and outlet right port 16 to atmosphere. After covering about half of the piston stroke distance, the cylindrical portion 14 on the right side of piston 5 enters into the central conical opening 25 of sealing member 21 while causing sealing member 21 to be expanded radially by means of the front beveled end 27. At this time, sealing member 21 tightly encircles the cylindrical portion 14, especially at the point of the smallest diameter 26 of said sealing member, so that unrestricted flow of fluid pressure medium from the cylinder chamber 30 into recess 15 of cylinder head 3 is interrupted at this point. Thus the compressed air remaining in chamber 30 can only escape through the through-passageways 29 and annular channel 31 of sealing member 21 through the throttle opening 11 into recess 15 adjusted by means of needle valve 10 which is located between passageways 12 and 13 of cylinder head 3. In this way, the piston movement is cushioned or retarded on the last portion of the stroke, with the partially trapped fluid pressure in cylinder chamber 30 being compressed by such piston movement and, therefore, acting, in addition to the friction-contact effect of the cylindrical portion 14 on sealing member 21, to force the sealing surface 22 and the sealing edge 32 of sealing member 21 tightly against bottom surface 20 of groove 18, so that channel 31 is also flattened out against said bottom surface to momentarily seal off passageways 29 from passageway 13, so that no pressure can escape via this route either. This is the reason, as was previously noted, that none of passageways 29 may be in axial alignment with passageways 13.

Shortly before reaching an inner wall 33 of cylinder head 3, piston 5 is elastically caught and braked by the beveled surface 23 of sealing member 21 axially projecting beyond the axial limit of said inner wall into the cylinder chamber 30, the toroidal surface 24 being the first to come into contact with piston 5. In this way, possible damage resulting from a hard metallic contact of piston 5 with inner wall 33 of cylinder head 3, which is normally of metal construction, is avoided, such damage being more apt to occur when throttle opening 11 is adjusted to a relatively large opening of needle valve 10 or a weak initial cushioning of the piston movement is effected.

When piston 5 impinges on the toroidal buffering edge 24 of sealing member 21, the latter is so deformed that it grips the cylindrical portion 14 of piston 5 with an even greater encircling force and intensifies the sealing effect.

Upon renewed venting of left port 16 or supply of fluid pressure to right port 16, sealing memeber 21 is axially displaced leftwardly by the measure of its axial clearance to the point of contact with the internal beveled surface of flange 19 of annular groove 18 as a result of the pressure building up in recess 15 of cylinder head 3 due to the concurrent choking or throttle action of needle valve 10 and the initially slowly retreating piston 5, so that the sealing surface 22 and particularly the sealing edge 32 is loosened from the bottom 20 of annular groove 18. The fluid pressure medium can now enter into cylinder chamber 30 through the communication thus produced, with a slight throttling effect, via annular channel 31 and axial passageways 29 of sealing memeber 21 to strongly act on piston 5. After cylindrical portion 14 has emerged from central opening 25 of sealing member 21, all barriers to unrestricted flow of fluid pressure into chamber 30 are removed so that piston 5 can be acted on by the full fluid pressure.

The design and installation of sealing member 21 represented is especially simple and advantageous with respect to the flow of pressure medium.

In the manner above described, damage to the cylinder device 1, particularly to the piston 5 and cylinder head 3, is avoided so that wear of the sealing member 21 occurring in the course of time on the sealing edges of said sealing member when performing valve functions cannot have a destructive effect on the cylinder device as a result of the weaker initial cushioning of the piston stroke caused by such wear. Moreover, the particular strcture of the invention makes it possible to enlarge the throttle opening 11 by adjustment of the needle valve 10 without risk, when a higher or more rapid rate of piston retraction is desired, since the energy of the more rapid retraction of the piston 5 intended and achieved in this way is also nullified by the final cushioning action of the frontal buffering area of toroidal surface 24.

Advisably, since the toroidal front surface 24 blends into the central conical opening 25 via such a donut-shaped rounding, a satisfactory deformable buffering edge is provided whose deformation also causes an increase in the closing force and thus the sealing of the sealing memeber 21 on the cylindrical portion 14 encircled by said conical opening.

Claims

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a cylinder device having at least one cylinder head in which is formed a combined fluid pressure supply and exhaust cylindrical recess for reciprocably accommodating therein, with radial clearance, an end portion of the piston rod of a piston and rod assembly and a diametrally enlarged portion of the piston rod formed in juxtaposition to the adjacent one side of the piston, in combination:

a. an annular groove formed in said cylinder head coaxially with and adjacent to the opening of said recess, said annular groove being defined by two oppositely facing and spaced apart end walls radially disposed relative to the wall of said recess and joined by a cylindrical surface forming the side wall of said groove;

b. a resilient annular sealing member disposed in said groove for axial movement therein relative to said recess between the limits defined by said spaced apart end walls, said annular sealing member, when in a relaxed state, having an inner diameter larger than said end portion and smaller than said enlarged portion of the piston rod and an outer diameter less than that of said side wall of said annular groove to provide an expansion clearance therebetween;

c. unrestricted passage means comprising said radial clearance between said piston rod and said cylindrical recess and the radial clearance between said inner diameter of said annular sealing member and said end portion of the piston rod for providing unrestricted flow of fluid under pressure to and from a cylinder chamber formed adjacent said one side of the piston during axial movement of said end portion of the piston rod through said unrestricted passage means coinciding with movement of the piston in one direction toward the cylinder head or in the opposite direction away therefrom; and

d. restricted passage means disposed in said cylinder head in parallel relation to said unrestricted passage means with one end opening to said annular groove and the other end opening to said cylindrical recess, said enlarged portion of the piston rod being effective, when moving axially through said sealing member, for cutting off said unrestricted passage means and limiting flow of fluid pressure between said cylinder chamber and said cylindrical recess to a restricted rate through said restricted passage means only,

e. said sealing member having communicating passage means formed therein for communicating said cylinder chamber with said restricted passage means during such time that said unrestricted passage means is cut off and having an annular frontal portion projecting axially out of said groove into said cylinder chamber, said frontal portion being abuttingly engaged by the piston during final movement thereof for providing final cushioning effect on the piston and consequent distortion of the sealing member in said groove against said one end of said restricted passage means for cutting off said communicating passage means from said restricted passage means and, therefore, said restricted flow through the restricted passage means during said final movement of the piston in said one direction.

2. A cylinder device, as set forth in claim 1, wherein the axial dimension of that portion of the sealing member confined within said annular groove is less than the axial distance between said end walls of the groove.

3. A cylinder device, as set forth in claim 1, wherein said frontal portion of said sealing member comprises an annular toroidal surface formed adjacent the inner diameter of the sealing member and in facing relation to the cylinder chamber, said toroidal surface joining at its inner periphery with a tapered concentric opening expanding diametrically toward the cylindrical recess and at its outer periphery with a beveled surface sloping away from the toroidal surface toward said cylindrical recess, the end wall of said annular groove adjacent the cylinder chamber being complementarily beveled and uniformly axially spaced from the beveled surface of the sealing member.

4. A cylinder device, as set forth in claim 1, wherein said communicating passage means in said sealing member comprises a plurality of angularly spaced passageways extending axially therethrough for communicating said cylinder chamber with said restricted passage means for effecting said restricted flow to and from said cylinder chamber during said axial movement of said enlarged portion through said sealing member.

5. A cylinder device, as set forth in claim 4, wherein a communication between said angularly spaced passageways and said one end of said restricted passage means is provided via a common annular channel formed on the side of said sealing member opposite said frontal portion and to which said spaced passageways open, said channel also registering with said one end of said restricted passage means opening to said annular groove.

6. A cylinder device, as set forth in claim 5, wherein distortion of the sealing member resulting from engagement thereof by said piston moving in said one direction causes said annular channel to be compressed against the respective adjacent end wall of said annular groove and cooperating therewith for sealing off said communication between said angularly spaced passageways and said one end of the restricted passage means.