Expansible chamber devices – With releasable stop or latch means to prevent movement of... – Engages member coaxial with and rotatable relative to...
Reexamination Certificate
1999-01-04
2001-01-30
Ryznic, John E. (Department: 3745)
Expansible chamber devices
With releasable stop or latch means to prevent movement of...
Engages member coaxial with and rotatable relative to...
C092S0210MR, C092S028000
Reexamination Certificate
active
06178870
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fluid pressure cylinder provided with a lock mechanism which grips a piston rod, thus keeping the rod at rest against fluid pressure.
PRIOR ART
Lock mechanisms have been incorporated in fluid pressure cylinders to stop the piston rod in a certain position. In such a mechanism, a brake shoe is pressed against the piston rod through balls, using a tapered ring whose internal surface is tapered. Using a brake spring, the lock mechanism urges the tapered ring in the direction of braking to lock the piston rod through the balls, thus holding the tapered ring in an unlocking position using a release piston that is driven by lock-release air pressure.
Because a fluid pressure cylinder with such a lock mechanism is driven using air pressure and because its lock mechanism is also deactivated using air pressure, a plurality of air pressure pipe lines with valve control to supply air to the cylinder or discharge it from the cylinder must be connected to the cylinder. If a set of valves controlling many such fluid pressure cylinders are installed and controlled as a unit by a controller, a plurality of air pressure pipe lines are only connected with the fluid pressure cylinders. However, if the cylinders are used separately, if it is necessary to determine which valve corresponds to which fluid pressure cylinder, or if the capacity of the flow channel downstream of a valve needs to be reduced to increase the response of a lock mechanism or the like, the valve should be installed on the fluid pressure cylinder.
However, for a fluid pressure cylinder containing such a lock mechanism as described above, a rod-side cover must be provided with a rod-side cylinder port through which air pressure is supplied or released to drive the piston or with a cushion valve for damping the piston. In addition, the fluid pressure cylinder must be provided with an unlocking port which supplies air pressure to free the piston rod locked by the lock mechanism or with a manual unlocking actuator which is intended to allow the piston rod to be manually unlocked if air pressure for unlocking the piston rod cannot be fed. Furthermore, a bracket must be secured to the cylinder to mount it in an apparatus. Morever, the lock mechanism must be as small as possible. These requirements make it difficult to provide space where the valves can be installed on the rod-side cover of the cylinder with lock mechanism.
SUMMARY OF THE INVENTION
It is an object of the present invention to make it possible to provide space for valves on the rod-side cover of a fluid pressure cylinder with a lock mechanism.
It is another object of the present invention to provide a fluid pressure cylinder with a lock mechanism which features good response and a stable braking force.
To solve the above problems, a fluid pressure cylinder with a lock mechanism according to the present invention is arranged as described below. The cylinder is driven by feeding compressed air through a cylinder port to pressure chambers on both sides of a piston or discharging compressed air from the chambers, and the mechanism locks the piston rod by gripping it.
The lock mechanism is arranged by holding brake shoes inside a lock mechanism cover which stops the piston rod by gripping it, holding a shoe holder which applies a braking force to the brake shoes so that the holder is prevented from moving in the direction of the axis of the piston rod, sliding a release piston into the lock mechanism cover to bring the end surface of a tapered ring located around said shoe holder in contact with the piston surface on the side of the cylinder, making a brake spring act on the release piston around the tapered ring, defining a pressure chamber opposite to the surface of the release piston which is on the side of the cylinder, tapering the internal surface of the tapered ring so that the inner diameter of the ring is larger on the side of the release piston than on the opposite side, disposing many balls, held by a retainer, between the circumference of the shoe holder and the tapered surface, urging the retainer by use of a prepressing spring in such a direction that the balls held by the retainer come in contact with the internal surface of the tapered ring, and providing on the lock mechanism cover a manual opening actuator which presses the release piston from the side of the pressure chamber when operated.
In the fluid pressure cylinder with the lock mechanism, a cylinder port which supplies or discharges compressed air to drive the piston is provided on the cylinder side of the lock mechanism cover, an unlocking port leading to the pressure chamber is disposed opposite to the cylinder side of the lock mechanism cover, the manual opening actuator is installed, and a flat area is ensured around the unlocking port on the lock mechanism cover to install valves which control compressed air fed through the unlocking port.
In a fluid pressure cylinder with a lock mechanism according to the present invention, feeding compressed air through the unlocking port to the pressure chamber on one side of the release piston causes the release piston to be driven against the force of a brake spring by a driving force of compressed air. Thus, the tapered ring does not press the balls, so the brake shoes release the piston rod, thereby freeing the piston rod from the lock mechanism. Discharging compressed air through the unlocking port from the pressure chamber causes the release piston to be returned to the side of the pressure chamber by the force of the brake spring. At the same time, the tapered surface of the tapered spring presses the balls, which in turn press the brake shoes through a shoe holder against the piston rod, thus locking the piston rod.
Since the release piston is provided on the side of the outer end of the lock mechanism cover, as is the pressure chamber that drives the release piston, a cylinder port through which compressed air is fed or discharged to drive the piston and a cushion valve for damping the piston can be disposed near the cylinder on the lock mechanism cover, and the unlocking port through which compressed air is supplied to unlock the piston rod and a manual opening actuator can be installed on the side of the outer end of said cover. This in turn means that the ports can be dispersed on the lock mechanism cover, so that a flat area in the viinity of the unlocking port can be provided for valves that control the cylinder and lock mechanism. This includes an area on the lock mechanism cover near the cylinder port for istalling the valves. As a result, a fluid pressure cylinder with a lock mechanism can be provided wherein it is advantageous if the cylinder is used separately, if it is necessary to determine which valve corresponds to which fluid pressure cylinder, or if the response of the lock mechanism needs to be increased.
In the lock mechanism, the brake shoes and shoe holder are provided inside the lock mechanism cover so that the shoes and holder can slide radially; the tapered ring and retainer are floated radially; many receiving pockets receiving the balls are provided in two rows around the retainer, the receiving pockets on the side of the release piston receiving balls of a large diameter and those on the opposite side receiving balls of a small diameter; and an elastic ring is wound in a V-shaped groove formed on one side of the outer circumference of the two rows of pockets around the retainer to prevent the balls from falling off and urge them in the direction tangential to the outer circumference of the shoe holder, so that a well-balanced, highly responsive, and stable braking force can be applied to the piston rod according to its eccentricity.
Such a fluid pressure cylinder with a lock mechanism according to the present invention makes it possible to ensure on the lock mechanism cover an area for installing valves to control the cylinder and lock mechanism. This configuration is advantageous if the cylinder is used separately, if it is necessary to determine which v
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ryznic John E.
SMC Corporation
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