Pumps – Expansible chamber type – Valved piston
Patent
1997-12-15
2000-09-19
Freay, Charles G.
Pumps
Expansible chamber type
Valved piston
417545, F04B 3910
Patent
active
061202665
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a piston mechanism. More particularly, the invention relates to a piston for such a mechanism with a flow passage therethrough.
2. Description of the Related Art
Such a piston mechanism allows the sucking in or intake of gaseous medium into the cylinder through the piston without an extra valve in the piston.
BE-A-378.946 describes a compressor with such a piston mechanism. However, the passage in the piston only extends partly thereover, namely from the front side up to an opening in the side which, in the utmost extended position, is not yet situated at the back side of the piston. Consequently, this passage does not open at the back side of the piston.
Gaseous medium is sucked in via chambers situated on the outside of the cylinder and consequently not via the crank chamber which is filled with oil. This oil serves to lubricate the bearings with which the piston rod is connected to the crank shaft and the piston. Hereby, the heating of the bearings is avoided, but traces of oil will be present in the obtained compressed air, which is not desirable for certain applications.
The presence of chambers at the outside of the cylinder and the use of oil to lubricate do not make the construction simple.
The gaseous medium which is sucked in through the passage flows along the wall of the cylinder which may be rather hot during operation, resulting in the heating of the medium, disadvantageously affecting the efficiency of the compressor.
A piston mechanism whereby the piston is provided with a passage which opens at the rear side of the piston and whereby the piston ring forms a valve in the passage is known from CH-A-308,083. However, this piston mechanism is not of the type concerned by the invention because the piston is stiffly connected with the piston rod and a crank chamber is not present. Therefore, such a piston mechanism does not show the problem of heating of the bearings.
SUMMARY OF THE INVENTION
According to the invention, a piston mechanism (for example, a compressor) comprises a cylinder which, at one extremity, is provided with a closable cylinder passage and, at the other extremity, opens into an interior of a crank chamber; a piston, axially movable in the cylinder, which is provided with a closable piston flow passage, and which comprises in its outer circumference a groove in which a piston ring is situated for sealing between the piston and the cylinder; and a movement mechanism to axially move the piston in the cylinder. The movement mechanism comprises a crank shaft positioned in the crank chamber and a crank or piston rod which, on one end, is hingedly connected to the piston by a first bearing, and, on the other end, is hingedly connected to the crank shaft, by a second bearing. The piston ring is positioned with a clearance in an axial direction in the groove and the piston ring forms a valve for closing and opening the piston passage.
The object of the invention is to provide a piston mechanism which does not present the above-mentioned and other disadvantages and which is not only relatively simple in construction and possesses a very good efficiency, but which can also operate without oil lubrication and yet is relatively long-lasting.
According to the invention this aim is achieved in that the piston opens at the rear side of the piston onto the first bearing.
The medium which is sucked in through the piston passage originates from the rear side of the piston and is to a minimal extent in contact with parts of the piston mechanism that are heated during the operation of the piston mechanism.
In a preferred embodiment of the invention, the piston is provided at its rear side with a cavity into which the piston passage opens and in which the first bearing is situated.
Thus, a part of the piston passage extends inwardly through a wall of the piston, whereby the possible heating of the medium sucked in through the piston passage, caused by heated parts, is considerably reduced.
In a particular embodiment
REFERENCES:
patent: 2106236 (1938-01-01), Burke
patent: 3831952 (1974-08-01), Geffroy
patent: 4058104 (1977-11-01), Swoager
patent: 4817390 (1989-04-01), Suganami et al.
patent: 5921755 (1999-07-01), Eldridge
Atlas Copco Airpower, Naamloze vennootschap
Freay Charles G.
Gray Michael K.
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