Motors: expansible chamber type – Working member position responsive motive fluid control – Exhaust control
Reexamination Certificate
1999-10-21
2001-08-28
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
Working member position responsive motive fluid control
Exhaust control
C091S409000, C091S443000
Reexamination Certificate
active
06279451
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an air cylinder having a cushion mechanism for absorbing a shock due to the energy of inertia when a piston of the cylinder stops at the stroke terminal end thereof.
DESCRIPTION OF THE RELATED ART
In an air cylinder having a cylinder tube and a piston sliding within the cylinder tube, a cushion mechanism has been well known in which cushioning air is temporarily encupsulated in an air chamber in the exhaust side to be pressurized during the piston operation to thereby decelerate the piston using the exhaust-air pressure, resulting in stopping it in a cushioning manner at the stroke end. In this conventional air cylinder, an air discharge path is blocked by inserting a cushion ring disposed in the piston side into cushion packing within the piston tube before the stroke end so as to lead the discharging air to a throttle valve. Thereby, the back pressure of the piston converts the kinetic energy of the piston to the air compressing energy in accordance with the throttling adjustment of the throttle valve, exerting a decelerating force.
However, in the above-described conventional air cylinder with a cushion mechanism, since it is needed for the structural reason of the cushion mechanism that a required length of the cushion ring be disposed in at least one side of the piston and a long empty room for inserting the cushion ring be disposed in the cylinder tube, a problem that the longitudinal length of the cylinder is inevitably increased is indicated.
SUMMARY OF THE INVENTION
It is a main technical problem to be solved by the present invention to provide an air cylinder with a cushion mechanism which is small-sized, simple in construction, and inexpensive as well by eliminating the long cushion ring and the empty room for inserting thereinto.
It is another technical problem to be solved by the present invention to provide an air cylinder with a cushion mechanism which is simple and rationally designed as well in construction, having only means for restraining discharging air flow in the cylinder tube side and plural numbers of packing for piston-packing and cushion-packing in common disposed in the piston.
In order to solve the above-mentioned problems, an air cylinder with a cushion mechanism according to the present invention including a cylinder tube; a piston sliding within the cylinder tube; and two ports for supplying and discharging compressed air to and from two pressure chambers separated by the piston, respectively, the air cylinder comprises a discharge outlet for communicating with the pressure chamber disposed in a position corresponding to at least one of the two ports in the cylinder tube to be positioned closer to the end of the cylinder tube than the port; speed-regulating means for stopping the piston in a cushioning manner by restraining the flow of discharging air from the pressure chamber, connected to the discharge outlet; and a plurality of piston packing rings for defining the two pressure chambers by touching and sliding on the inner peripheral surface of the cylinder tube, disposed in the outer peripheral surface of the piston, wherein at least a part number of the plurality of piston packing rings serve the function as cushion packing in common by discharging compressed air within the pressure chamber only through the discharge outlet when they pass-through over the port in the discharge side just before the piston reaches the stroke end.
In the air cylinder formed as described above, the piston is driven in the positive and reverse directions by alternately supplying and discharging compressed air through the two ports. The deceleration and stopping of the piston by the cushion mechanism at the stroke end are performed as follows. When the piston is sliding, the compressed air in the pressure chamber in the discharge side is discharged via the port in the beginning. Then, when the piston approaches the stroke end and the piston packing ring serving the function as cushion packing in common passes through over the port in the discharge side, the path between the port and the pressure chamber is intercepted, so that the compressed air in the pressure chamber in the discharge side is discharged in a restraining manner only through the discharge outlet via the speed-regulating means. Thereby, the air pressure in the pressure chamber is increased by the flow control of the speed-regulating means so as to be back-pressure against the piston, such that the piston reaches the terminal end of the stroke while being decelerated.
The above-described air cylinder with a cushion mechanism is not needed to form a long cushion ring and a long empty room for inserting the cushion ring, so that the longitudinal length of the cylinder can be reduced to that extent, resulting in enabling the air cylinder to be miniaturized.
Moreover, since the speed-regulating means for restraining the discharging air flow is disposed in the cylinder tube side and plural packing rings substantially serving the function as piston packing and cushioning packing in common are formed in the piston side, the designed structure thereof can be simplified by reducing the number of parts and rationalized as well to thereby reduce the manufacturing cost of the air cylinder.
In an air cylinder according to the present invention, the discharge outlet may be connected to the corresponding port via the speed-regulating means.
In a specific embodiment of an air cylinder according to the present invention, the speed-regulating means may comprise a throttling mechanism for restraining the flow of discharging air flowing from the discharge outlet toward the port side and a check valve which stops the flow of discharging air flowing from the discharge outlet toward the port side while allows the flow of compressed air in the opposite direction thereto.
In a preferred embodiment of an air cylinder according to the present invention, the speed-regulating means may be assembled in a valve chamber formed in the cylinder tube for communicating with the discharge outlet and the port, by accommodating a valve member having the throttling mechanism therein interposing a lip seal forming the check valve therebetween.
In another embodiment of an air cylinder according to the present invention, the speed-regulating means may be formed of a throttling mechanism for restraining the flow of discharging air flowing from the discharge outlet toward the port side, and wherein a part number of the plurality of piston packing rings serving the function as cushion packing in common may serve the function as a check valve in common which allows the flow of discharging compressed air flowing from the port side toward the discharge outlet side while stops the flow in the opposite direction thereto when they are positioned between the port and the discharge outlet at the stroke end.
In the present invention, in order to stop the piston in a decelerating manner at the both stroke ends in the positive and reverse sides, two sets of the discharge outlet, the speed-regulating means, and the piston packing ring serving the function as cushion packing in common may be disposed corresponding to the two ports.
REFERENCES:
patent: 4207800 (1980-06-01), Homuth
patent: 4393751 (1983-07-01), Kelly
patent: 4397218 (1983-08-01), Spring
patent: 5284083 (1994-02-01), Vaslin
patent: 0 004 483 (1979-10-01), None
patent: 698651 (1953-10-01), None
patent: 1 535 873 (1978-12-01), None
Hirano Akihiro
Nishimata Kenichi
Leslie Michael
Look Edward K.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Corporation
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