US3858485A - Fluid cylinder - Google Patents

Abstract

A fluid cylinder comprising inner and outer tubular members telescopically joined for relative movement between extended and retracted positions. A piston carried by the outer tubular member is slidably disposed in the inner tubular member and the inner end of the inner tubular member forms a second piston. Ports and passages are provided to selectively direct fluid to the areas on opposite sides of each of the two pistons. Various valving arrangements are employed to regulate fluid flow between the various chambers formed within the cylinder to thereby regulate the speed of extension and retraction.

Description

United States Patent 1 Rosaen et a1.

1 1 Jan.7,1975

1 1 FLUID CYLINDER [76] Inventors: Borje O. Rosaen, 4031 Thornoaks,

Ann Arbor, Mich; Robert L. Firth, 4817 Sunnyslope Rd, Minneapolis, Minn.

[22] Filed: Nov. 16, 1973 [21] Appl. No.: 416,595

Related US. Application Data [60] Continuation-in-purt of Ser. No. 110,062, Jun. 27, 1971, abandoned, which is a division of Ser. No. 797,420, Feb 7, 1969, Pat. No. 3,592,108, which is a continuation-impart of Ser. No. 660,454, Aug. 14,

[52 U.S. Cl 91/436, 91/415, 91/447,

[51] Int. Cl. FlSb 15/17, FlSb 13/042 [58] Field of Search 91/436, 437, 415; 92/108, 92/52 [56] References Cited UNITED STATES PATENTS 3,357,451 12/1967 Tennis 91/436 3,426,649 2/1969 Koppers 92/52 3,452,397 7/1969 Newton 91/436 3,483,798 12/1969 Parrett et a1 92/52 Primary ExaminerPaul E. Maslousky Attorney, Agent, 0r Firm-Hauke, Gifford, Patalidis & Dumont [57} ABSTRACT A fluid cylinder comprising inner and outer tubular members telescopically joined for relative movement between extended and retracted positions. A piston carried by the outer tubular member is slidably disposed in the inner tubular member and the inner end of the inner tubular member forms a second piston. Ports and passages are provided to selectively direct fluid to the areas on opposite sides of each of the two pistons. Various valving arrangements are employed to regulate fluid flow between the various chambers formed within the cylinder to thereby regulate the speed of extension and retraction.

3 Claims, 3 Drawing Figures FLUID CYLINDER CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. Pat. application, Ser. No. 110,062 filed Jan. 27, 1971, now abandoned, which in turn was a divisional U.S. Pat. application of co-pending application Ser. No. 797,420 filed Feb. 7, 1969, now U.S. Pat. No. 3,592,108 dated 7-13-71, which, in turn, was a continuation-in-part of U.S. Pat. application application Ser. No. 660,454 filed Aug. 14, 1967, and is related in substance to U.S. Pat. No. 3,335,642 issued Aug. 15, 1967.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fluid cylinders of the general type disclosed in the aforementioned patent and patent applications, and more particularly to such fluid cylinders in which means are provided for selectively or automatically producing different speeds as between retraction and extension or as between different portions of the extension or retraction strokes.

2. Description of the Prior Art Fluid cylinders are widely employed as a means for converting fluid power into a reciprocating mechanical motion. There are a number of different types of such cylinders but generally they comprise a tubular member having its opposite ends closed; and a piston slidably disposed in the tubular member having a rod extending through one or both of the closed ends. Means are provided for introducing hydraulic fluid under pressure alternately between the opposite sides of the piston to reciprocate the rod relative to the tubular member.

One problem inherent in conventional fluid cylinders has been the difficulty in providing a construction wherein an equal displacement is to be provided on each side of the piston so that an equal line pressure applied to each side of the piston will produce equal thrust. The aforementioned U.S. Pat. No. 3,335,642 provides a construction formed of telescoping tubular members in which the effective area between the tubular members is added to the rod member side of the piston and in this way the effective piston area on each side of the piston is equal.

Co-pending application Ser. No. 660,454 discloses an important improvement on this type of construction wherein the blind end of the inner tubular member is formed into a second piston and the areas on each side of the two pistons are utilized to substantially increase the thrust which can be achieved by a cylinder of a given diameter.

There is yet another problem associated with conventional fluid cylinders. If a fixed fluid delivery rate is supplied to the cylinder, the cylinder rod travel speed can only be varied by varying the piston and rod diameters or by providing a regenerative circuit for transferring oil from the rod end to the blind end during extension. In cylinders having a regenerative circuit the speed can only be increased during extension and it is not possible in either of these types of cylinders to provide multiple speeds in one or both directions.

Further, where the cylinder is constructed to provide a retraction speed substantially greater than the extension speed the exhaust flow rate during retraction will be correspondingly greater requiring larger lines and producing high line losses.

SUMMARY OF THE INVENTION The present invention which will be described subsequently in greater detail includes a number of modifications similar to the constructions described in the aforementioned patent and patent application, but including valve means positioned intermediate the chambers regulating piston movement; or between the ports and such chambers for the purpose of either selectively or automatically regulating the speed of movement of the piston rod.

The construction of the present invention, unlike previous constructions, makes it possible to provide a cylinder in which the cylinder rod travel speed during retraction is greater than that produced upon extension, but in which exhaust flow rates are maintained equal. Further, in some modifications it is possible to provide multiple speeds in either or both directions.

DESCRIPTION OF THE DRAWINGS FIG. 2 is a diagrammatic view illustrating in one operative position a fluid circuit cooperating with the preferred embodiment of the present invention;

FIG. 3 is a diagrammatic view of the fluid circuit of FIG. 2 shown in another operative position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawings for a more detailed description of the present invention which is there shown as being designed to provide two speed operation in both directions.

The cylinder comprises an outer tubular member and an inner tubular member 118 with a cap 112 fixed to the outer tubular member 110 to define a chamber 135. A hollow piston rod 120 is fixed to the cap 1112 and a piston 122 carried by the rod 120 is received by the inner tubular member 118. The rod 120 axially slidably extends through a second piston 128 which closes one end of the inner tubular member 118. The opposite end of the inner tubular member 118 is closed by a mounting member 124.

The inner tubular member 118 defines a chamber 138 between the pistons 122 and 128. A cavity 126 formed in the mounting member 124 defines a chamber 127 on the blind side of the piston 122. A chamber 134 is formed by the outer tubular member 110 intermediate the piston 128 and a flanged member 132 carried by the outer tubular member 110.

An inner tube 137 is carried within the piston rod 120 and extends through the piston 122 to register with the chamber 127. A port 140 and passages 143 and 145 formed in the cap member 112 and the piston rod 120 respectively provide a fluid path through the tube 137 to the chamber 127.

A port 142 and a passage 144 formed in the cap member 112 and an opening 146 and 148 formed in the piston rod 120 provide a fluid path to the chamber 138.

A port 136 formed in the outer tubular member 110 provides a fluid path to the chamber 134.

FIGS. 2 and 3 illustrate schematically a preferred valving arrangement for use with the cylinder illustrated in FIG. 1. The purpose of this valving arrangement is to isolate the chamber 138 from the other chambers and to add and substract its volume to and from that of the other areas to produce the desired variation in speed.

The valving arrangement preferably comprises a speed selector portion 160 and a directional valve portion 162. The speed selector portion 160 comprises a three land spool valve 164 urged by a spring 166 to the position shown in FIG. 2 and movable by fluid pressure sufficient to overcome the spring 166 through a port 168 to the position shown in FIG. 3. Movement of spool valve 164 can be moved by other means, of course, as for instance manually if this is preferred. In the position of the spool valve 164 illustrated in FIG. 2 ports 140 and 142 of the fluid cylinder are connected to each other and through the speed selector portion 160 to a conduit 170. The conduit 170 is connected with a port 172 formed in the directional valve 162. The central land 174 of the spool valve 164 closes communication between the ports 142 and 136 and the port 136 is connected through the speed selector portion 160 and a conduit 176 to a port 178 provided in the directional valve 162.

. Fluid pressure is either automatically or selectively provided to the port 168 from a pump 180 sufficient to overcome the spring 166 moves the spool valve 164 toward the position shown in FIG. 3. In this position the port 140 is isolated from the port 142 by the central land 174 and the ports 142 and 136 are connected to each other and to the conduit 176. The port 140 is connected to the conduit 170.

The directional valve portion 162 comprises a three land spool valve 182 movable between positions wherein the pump 180 is connected to either the port 172 or the port 178. Movement of the spool valve 182 is controlled by alternately providing fluid pressure and exhausting at ports 184 and 186 by manual or automatic means (not shown). The directional valve portion 162 is also provided with passages 188 connecting either the port 178 or the port 172 with a fluid reservoir 190 when the other port 172 or 178 is connected with the pump 180.

In operation the position of the spool valve 182 determines whether the fluid cylinder will extend or retract. In extending the cylinder shown in FIG. 1 the inner tubular member 118, the mounting member 124, and the piston 128 move to the left while the cap 112, the outer tubular member 110, the flanged member 132, the hollow rod 120, and the piston 122 remain stationary. Thus, as the extension proceeds, the volumes of cavities 134 and 138 decrease at rates relating to one another as do their cross-sectional areas while the volumes of cavities 127 and 135 increase. Motions and volume changes reverse upon retraction.

The position of the spool valve 164 determines whether movement of the cylinder, either retracting or extending, will be at fast speed or at slow speed. With the spool valves 164 and 182 positioned as shown in FIG. 2 fluid under pump pressure will be supplied to ports 140 and 142 and exhausted from port 136. Thus, fluid will be exhausted from chamber 134 and delivered to chambers 127 and 138. The effective area of the piston 122 exposed to fluid pressure within the chamber 127 is substantially twice that exposed to pressure within the chamber 138 so the cylinder will be moved toward an extended position. As the cylinder extends chamber 138 contracts and the fluid emptying from this chamber is added to the expanding chamber 127 through the connection provided by the speed selector portion 160 of the valve. Thus the cylinder will extend at a faster rate than it would if it were only being provided with fluid by the pump 180.

When the pressure in chamber 138 has increased to a predetermined value the pressure at port 168 will have increased sufficiently to overcome the spring 166 and to cause the spool valve 174 to shift to the position shown in FIG. 3. In this position the port 142 is exhausted to the reservoir 190 to relieve the pressure in chamber 138. The fluid from chamber 138 will be exhausted to the reservoir 190 rather than being added to the chamber 127 and the result is a substantially onehalf reduction in the speed of cylinder extension.

Retraction of the cylinder is accomplished in substantially the same way except that the spool valve 182 is either automatically or selectively shifted from the position shown in FIG. 2 to the left to connect the port 178 to the pump 180 and the port 172 to the reservoir 190. With the spool valve 182 in this position and the speed selector portion 160 in the position shown in I FIG. 2 the ports 140 and 142 are exhausted to the reservoir and fluid under pressure from the pump 180 is directed through the port into the chamber 134 to retract the cylinder at fast speed. Retraction at slow speed is produced by movement, either selectively or automatically, of the spool valve 164 to the position shown in FIG. 3. This opens chamber 138 to fluid pressure to double the effective piston area and, thus the volume change per change in chamber length, and, assuming a constant pumping volume, to cause a reduction in cylinder speed of substantially one-half.

It is apparent that a fluid cylinder has been disclosed which like those disclosed and claimed in the aforementioned patent and patent applications utilizes a telescoping construction to produce improved means of providing balanced operation and maximum thrust within given diameter limitations. The present invention adds to these improvements a construction which produces, either selectively or automatically, two speed operation. The particular manner of achieving this result maintains substantially equal intake and exhaust flow rates and permits multiple speed retraction, an operation which with conventionally constructed fluid cylinders has been difficult to achieve.

It is also apparent that although we have described only one preferred embodiment of the present invention many changes and modifications can be made therein without departing from the spirit of the invention as expressed by the scope of the appended claims.

We claim:

l. A fluid cylinder comprising a first, inner tubular member; a piston mounted within said first tubular member in a manner allowing reciprocal movement of said first tubular member relative to said piston and dividing the interior of said first tubular member into a first chamber and a second chamber; a rod member having a first end fixed to said piston and a second end extending exteriorly of said second chamber; a second, outer tubular member telescopically received over said first tubular member and radially spaced therefrom to define a third chamber, said second tubular member being connected to said second end of said rod, fixing the axial position of said piston relative to said second tubular member so that axial movement of said first and second tubular embers with respect to each other results in said third chamber contracting upon contraction of said second chamber and said third chamber expanding upon expansion of said second chamber, means closing the ends of said first and second tubular members; means for selectively providing fluid to and exhausting fluid from said first, second, and third chambers; a first valve means disposed intermediate said second and third chambers, said first valve means being normally positioned to allow fluid communication between a constant flow pump and both said first and second chambers while isolating said third chamber which is in fluid communication with a reservoir through said valve means during expansion of said first chamber; said first valve means including pressure sensing means operable to open communication between said second and third chambers while isolating said first chamber to reduce the rate of expansion of said first chamber upon sensing a predetermined pump outlet presure; and second valve means operable to reverse cylinder movement reversingthe pressurization of said first valve means to effect an initial communication between said pump and said third chamber between said reservoir and said first and second chambers.

2. The fluid cylinder defined in claim 1 wherein the effective pressure responsive area of said piston exposed to said first chamber is greater than the effective pressure responsive area of said piston exposed to said second chamber.

3. The fluid cylinder defined in claim 1 wherein the effective pressure responsive area of said piston exposed to said first chamber is at least twice the effective pressure responsive area of said piston exposed to said second chamber.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 858 485 Dated January 1 1215 Inventor) Borje O. Rosaen and Robert L. Firth It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 11 delete "application".

Col. 3, line 31, after 166" insert -and move-; delete "moves".

Col. 4, line 29, after "reservoir" insert Col; 5, line'5, delete "embers" and insert --members--.

Signed and sealed this 11th day of March 1975.

(SEAL) Attest:

' C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 904050 (1M9) USCOMM-DC 60376-P69 i U.5 GOVERNMENT PRINTING OFFICE Z I", -'l-3ll'

Claims (3)

1. A fluid cylinder comprising a first, inner tubular member; a piston mounted within said first tubular member in a manner allowing reciprocal movement of said first tubular member relative to said piston and dividing the interior of said first tubular member into a first chamber and a second chamber; a rod member having a first end fixed to said piston and a second end extending exteriorly of said second chamber; a second, outer tubular member telescopically received over said first tubular member and radially spaced therefrom to define a third chamber, said second tubular member being connected to said second end of said rod, fixing the axial position of said piston relative to said second tubular member so that axial movement of said first and second tubular embers with respect to each other results in said third chamber contracting upon contraction of said second chamber and said third chamber expanding upon expansion of said second chamber, means closing the ends of said first and second tubular members; means for selectively providing fluid to and exhausting fluid from said first, second, and third chambers; a first valve means disposed intermediate said second and third chambers, said first valve means being normally positioned to allow fluid communication between a constant flow pump and both said first and second chambers while isolating said third chamber which is in fluid communication with a reservoir through said valve means during expansion of said first chamber; said first valve means including pressure sensing means operable to open communication between said second and third chambers while isolating said first chamber to reduce the rate of expansion of said first chamber upon sensing a predetermined pump outlet presure; and second valve means operable to reverse cylinder movement reversing the pressurization of said first valve means to effect an initial communication between said pump and said third chamber between said reservoir and said First and second chambers.

2. The fluid cylindem defined in claim 1 wherein the effective pressure responsive area of said piston exposed to said first chamber is greater than the effective pressure responsive area of said piston exposed to said second chamber.

3. The fluid cylinder defined in claim 1 wherein the effective pressure responsive area of said piston exposed to said first chamber is at least twice the effective pressure responsive area of said piston exposed to said second chamber.

Images