Work holders – With fluid means – Plural positioning means sequentially operated
Reexamination Certificate
2000-10-12
2002-08-06
Watson, Robert C. (Department: 3723)
Work holders
With fluid means
Plural positioning means sequentially operated
Reexamination Certificate
active
06427992
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a clamping cylinder actuator attached to a fixed member of a machine, such as a base to hold a workpiece fixedly on the fixed member for machining by a machine tool or the like and, more particularly, to a clamping cylinder actuator having a front end cover having a back joining surface to be joined to a fixed member of a machine, such as a base.
2. Description of the Related Art
A first related art clamping cylinder actuator disclosed in JP-B No. Sho 62-5739 (Publication 1) has a cylinder, and a front end cover having a back joining surface and a boss fitted in the bore of the cylinder with an O ring held between the cylinder and the boss of the front end cover. A second related art clamping cylinder actuator disclosed in JP-A No. 10-315083 (Publication 2) has a cylinder, a front end cover formed integrally with the cylinder, and the front end cover has a back joining surface to be joined to a fixed member of a machine, such as a base.
In the first related art clamping cylinder actuator disclosed in Publication 1, the boss of the front end cover needs a longitudinal dimension sufficient to form an annular groove to hold the O ring therein in the boss. Therefore, the length of the cylinder must include a length corresponding to a length in which the boss must be formed to form the annular groove for the O ring therein in addition to a length corresponding to the effective stroke of a piston that moves axially in the cylinder bore and hence the cylinder is inevitably long. The clamping cylinder actuator needs many bolts for fastening the front end cover and a back end cover to the cylinder, which requires troublesome part management and increases assembling work.
Although the second related art clamping cylinder actuator disclosed in Publication 2 does not have such problems, the cylinder and the front end cover cannot be formed of different materials, respectively because the cylinder and the front end cover are formed in an integral unit by forming.
Both the first and the second related art clamping cylinder actuator have the back joining surfaces to be joined to a fixed member of a machine. Since the front end cover is fastened to the fixed member with bolts with the joining surfaces thereof in direct contact with the fixed member, it is possible that the bolts are loosened by vibrations generated by the machine.
In the second related art clamping cylinder actuator disclosed in Publication 2, side ports for a working fluid are formed in a side surface of the front end cover and end ports are formed in the joining surface of the front end cover, and a pipe is connected to either the side ports formed in the side surface or the end ports formed in the joining surface. When the side ports are used and the end ports are not used, O rings are placed between the joining surface and the fixed member so as to surround the end ports to create nonleaking union between the front end cover and the fixed member. Handling the small O rings is troublesome and O rings are often lost.
A known clamping cylinder actuator has a cylinder provided on its outer surface with a position sensor for measuring the position of a piston fitted in the cylinder. Since the position sensor juts out from the outer surface of the cylinder, the clamping cylinder actuator needs a large space for installation, the cylinder needs a long machining time and hence the cylinder is costly.
A front end cover integrally provided with a guide member cannot be used as a part of another clamping cylinder actuator that does not need any guide member.
It is possible that a cutting fluid or a cutting oil leaks into the position sensor and cause the position sensor to malfunction. Therefore, although the position sensor is leak-proofed, it is undesirable, in respect of durability, to use the clamping cylinder actuator in an environment where the position sensor is exposed to the cutting fluid.
Accordingly, it is an object of the present invention to provide a clamping cylinder actuator having a front end cover having a back joining surface to be joined to a fixed member, in which a seal structure is held between the front end cover and a cylindrical member to which the front end cover is joined, and the seal structure prevents the loosening of bolts fastening the front end cover to the fixed member, under vibrations. It is also an object of the present invention to provide a clamping cylinder actuator with side ports and end-ports formed in the front end cover, in which an O ring is not necessary to be used for sealing the end ports.
Another object of the present invention is to reduce the manufacturing cost of a clamping cylinder actuator provided on the outer surface of the cylinder thereof with a magnetic sensor and to improve the appearance of the same.
For a further object, the present invention provides a clamping cylinder actuator requiring a small number of fastening parts necessary for fastening together its components including a front end cover, a cylinder and a back end cover, easy to assembly and satisfactory in appearance. The present invention also provides a clamping cylinder actuator having a front end cover provided with a small number of through holes. Further, the present invention provides a clamping cylinder actuator including a front end cover, a back end cover and a cylinder which can be fastened together in an airtight fashion with bolts. Furthermore, the present invention provides a clamping cylinder actuator having a front end cover available to clamping cylinder actuators of other types and effective in reducing the number of parts, and capable of being manufactured at a low manufacturing cost.
For a still further object, the present invention provides a clamping cylinder actuator having a position sensor for measuring the position of a piston in a cylinder, and a sensor cover capable of satisfactorily covering the position sensor so that the position sensor may not be wetted with a cutting fluid or the like.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a clamping cylinder actuator attached to a fixed member to clamp down a workpiece on the fixed member comprises: a cylindrical member; a front end cover provided with an opening and joined to the front end of the cylindrical member; a piston rod axially slidably extended through the opening of the front end cover; a back end cover disposed at the back end of the cylindrical member; and a gasket held between the cylindrical member and the front end cover to make a sealed joint between the front end of the cylindrical member and the front end cover; wherein the front end cover is attached to the fixed member with a joining surface of the back surface thereof extending outward from a sealing surface of the back surface thereof corresponding to the front end of the cylindrical member in contact with the fixed member, and the gasket covers the sealing surface and the joining surface of the back surface of the front end cover. The joining surface of the front end cover can be partly or entirely covered with the gasket.
Preferably, the cylindrical member includes a cylinder, a back end of which is joined to the back end cover, and the gasket makes a sealed joint between the front end of the cylinder and the back surface of the front end cover. When the cylindrical member includes a cylinder, and a guide member holding member disposed between the cylinder and the front end cover to hold a guide member engaged in a helical guide groove formed in the piston rod, the gasket makes a sealed joint between the front end surface of the guide member holding member and the back surface of the front end cover.
Since the gasket making a sealed joint between the front end cover and the cylindrical member extends over the joining surface, bolts fastening the front end cover to the fixed member will not be loosened by vibrations generated by a machining operation because the gasket is elastic. Since the front end cover and the cylindrical member (or the
Miyata Kanji
Noda Mitsuo
Yonezawa Tsuyoshi
Howa Machinery Ltd.
Ladas & Parry
Watson Robert C.
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