Fluid cylinder

Claim 2

A pressure fluid cylinder comprising a tubular casing, a piston with a connected piston rod reciprocable within said casing and defining two pressure chambers one on each side of the piston, brake means interposed between the outer wall of said piston and the inner wall of said casing, and means for operating said brake means mounted on said piston including pressure receiving means operable to engage the brake means against the casing when pressure in both of said pressure chambers is the same and to release the brake means when the pressure in one of said pressure chambers exceeds that in the other, said pressure receiving means including an annular member axially reciprocable within said piston to form a subpressure chamber, said subpressure chamber being connected by a fluid passageway to one of said pressure chambers.

Claim 3

A pressure fluid cylinder according to claim 1, wherein said brake means comprises at least one annular brake band disposed within an annular groove formed in the outer wall of said piston.

Claim 4

The pressure fluid cylinder as claimed in claim 2, wherein said brake band is made of synthetic resin.

Claim 5

A pressure fluid cylinder comprising a tubular casing, a piston with a connected piston rod reciprocable within said casing and defining two pressure chambers one on each side of the piston, brake means interposed between the outer wall of said piston and the inner wall of said casing, and means for operating said brake means mounted on said piston including pressure receiving means operable to engage the brake means against the casing when pressure in both of said pressure chambers is the same and to release the brake means when the pressure in one of said pressure chambers exceeds that in the other, said brake means comprising at least one annular brake band disposed within an annular groove formed in the outer wall of said piston, said annular brake band being resilient and having a radial self-returning force, said brake band having a cut-off portion, and said operating means including means engaging said cut-off portions for outwardly expanding said brake band to frictionally engage the inner wall of said cylinder casing.

Claim 6

A pressure fluid cylinder comprising a tubular casing, a piston with a connected piston rod reciprocable within said casing and defining two pressure chambers one on each side of the piston, brake means interposed between the outer wall of said piston and the inner wall of said casing, and means for operating said brake means mounted on said piston including pressure receiving means operable to engage the brake means against the casing when pressure in both of said pressure chambers is the same and to release the brake means when the pressure in one of said pressure chambers exceeds that in the other, said brake means comprising at least one annular brake band disposed within an annular groove formed in the outer wall of said piston, said annular brake band being resilient and having a radial self-returning force, said brake band having a cut-off portion, and said operating means including means engaging said cut-off portions for outwardly expanding said brake band to frictionally engage the inner wall of said cylinder casing.

Claim 7

A pressure fluid cylinder according to claim 4, wherein said operating means includes a movable plunger coupled to said pressure receiving means and having a neutral position in which said brake is expanded and engaged against said casing, resilient means for normally conditioning said plunger to its neutral position, movement of said plunger from its neutral position causing said operating means to release said brake band.

Claim 8

The pressure fluid cylinder as claimed in claim 5, wherein said means engaging said cut-off portion comprises a ball disposed in a radial bore provided within said piston, said ball being outwardly thrust into said cut-off portion to expand said brake band and being inwardly thrust out of said cut-off portion by the self-returning force of said brake band.

Claim 9

The pressure fluid cylinder as claimed in claim 5, wherein said operating means includes an elliptical cam disposed within the said cut-off portion, said cam being mounted on a rotor rotatable within a radial bore provided in said piston, a pinion gear on said rotor, and a rack on said plunger in mesh with said pinion gear, said cam being rotated to expand said brake band by movement of said plunger.

Claim 10

The pressure fluid cylinder according to claim 6, wherein said cut-off portions of the brake band are outwardly tapered toward one another.

Claim 11

The pressure fluid cylinder as claimed in claim 7, wherein said cut-off portion of the brake band has straight faces disposed approximately radially of the piston.

Claim 12

The pressure fluid cylinder as claimed in claim 8, wherein said plunger has a pair of annular groOves separated by a land, said plunger being axially reciprocable within said piston to thrust said ball outwardly into said cut-off portion by means of said land.

Claim 13

A pressure fluid cylinder as claimed in claim 10, wherein said resilient means for normally conditioning said plunger to its neutral position comprises a pair of coiled springs disposed at the ends of a second plunger reciprocable within said piston parallel to the axis of the piston, said first and second plungers being coupled by said pressure receiving means.

Claim 14

A pressure fluid cylinder comprising a tubular casing, a piston with a connected piston rod reciprocable within said casing and defining two pressure chambers one on each side of the piston, brake means interposed between the outer wall of said piston and the inner wall of said casing, and means for operating said brake means mounted on said piston including pressure receiving means operable to engage the brake means against the casing when pressure in both of said pressure chambers is the same and to release the brake means when the pressure in one of said pressure chambers exceeds that in the other, said brake means comprising a pair of annular brake bands disposed within an annular groove drilled along the outer wall of said piston means, each of said brake bands having a cut-off portion of which the cut-off faces are tapered outwardly toward one another, said cut-off portions being positioned on diametrically opposite sides of the outer wall of said piston, and said operating means being operable to expand and release both of said brake bands.

Claim 15

A pressure fluid cylinder comprising a tubular casing, a piston with a connected piston rod reciprocable within said casing and defining two pressure chambers one on each side of the piston, brake means interposed between the outer wall of said piston and the inner wall of said casing, and means for operating said brake means mounted on said piston including pressure receiving means operable to engage the brake means against the casing when pressure in both of said pressure chambers is the same and to release the brake means when the pressure in one of said pressure chambers exceeds that in the other, said brake means comprising a pair of annular brake bands disposed within an annular groove drilled along the outer wall of said piston means, each of said brake bands having a cut-off portion of which the cut-off faces are tapered outwardly toward one another, said cut-off portions being positioned on diametrically opposite sides of the outer wall of said piston, and said operating means being operable to expand and release both of said brake bands.