Expansible chamber devices – Piston with rigid axially extending hollow stem – Hollow stem forms axially extending fluid passage
Patent
1986-03-17
1988-02-23
Garrett, Robert E.
Expansible chamber devices
Piston with rigid axially extending hollow stem
Hollow stem forms axially extending fluid passage
92 59, 92117R, 92146, 291565R, F01B 3100
Patent
active
047262834
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a slide cylinder which is provided with pressurized fluid supply/discharge ports at the opposite ends of cylinder block and piston rods and also with fixing means on the cylinder block and cross plates fixed to the opposite ends of the piston rods to facilitate piping of the pressurized fluid ducts to the slide cylinder without being restricted by the condition of an installing place.
BACKGROUND OF THE INVENTION
There have been known in the art the so-called slide cylinders which are constituted by a cylinder block with a couple of juxtaposed cylinders, a piston and a piston rod, reciprocating the piston by supplying and discharging a pressurized fluid to and from drive chambers which are defined in the cylinder block by the piston.
The known slide cylinders, however, are adapted to supply and discharge the pressurized fluid through specific pipe joint ports, so that difficulties are often encountered in connecting the pressurized fluid ducts or pipes depending upon the condition of the place where a slide cylinder is to be installed.
DISCLOSURE OF THE INVENTION
A slide cylinder of the known type, such as the one disclosed in U.S. Pat. No. 3,994,539, comprises a cylinder block having two juxtaposed cylinders, a piston fitted in each cylinder, and a piston rod projecting on both sides of the piston, with each of the piston rods connected to a common cross plate, and is designed to reciprocate the piston rods by means of a pressurized fluid supplied and discharged to and from drive chambers defined by the pistons in the cylinder block.
A slide cylinder of this type is usually placed in such a position that a plane containing the axes of the two piston rods is horizontal, with a load imposed on the cylinder block or the cross plates at both ends of the piston rods. In such instances, the piston rods must have large enough diameters to withstand a bending force working thereon. Preferably, the pressurized fluid should be supplied and discharged through the piston rods, i.e., through a fluid passage provided therein. This also necessitates piston rods of a large outside diameter.
This leads to the design need to reduce the difference between the inside diameter of the cylinders and the outside diameter of the piston rods therein. Then, however, difficulties will be encountered in the fitting of the piston rod to the piston.
To ensure accurate machining and assembling of a piston rod and a piston, the piston rod must comprise a straight continuous bar-like member of a single piece. When a piston rod and a piston are integral, the piston rod portion is formed by machining off considerable metal from a material bar whose outside diameter is at least equal to the outside diameter of the piston. This is a waste of material. So a reasonable alternative is to fasten a separately prepared piston to a straight continuous one-piece piston rod. However, the piston cannot easily be secured free of axial backlash by such means as metal rings adapted to be fitted in grooves provided on each side of the piston mounted on the piston rod. Furthermore, cutting deep grooves on both sides of the piston is by no means preferably because it might reduce the strength of the piston rod.
DISCLOSURE OF THE INVENTION
An object of this invention is to provide means to fasten a piston to a piston rod without causing backlash in a slide cylinder of the known type described above in which the difference between the inside diamter of the cylinder and the outside diameter of the piston rod is relatively small.
Another object of this invention is to allow the piston to be fastened to the piston rod as described above by such means as can be prepared easily and at low cost.
In order to achieve the above objects, a slide cylinder comprises a cylinder block internally defining a plural number of parallel cylinder bores, piston rods extended through said cylinder bores, and pistons fixedly mounted on said piston rods in said cylinder bores, defining first and second drive chambers on the op
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Garrett Robert E.
Shoketsu Kinzoku Kogyo Kabushiki Kaisha
Williamson Mark A.
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