Pumps – Motor driven – Electric or magnetic motor
Patent
1997-07-10
2000-01-18
Freay, Charles G.
Pumps
Motor driven
Electric or magnetic motor
92131, 92165R, F04B 1704
Patent
active
060152737
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to electromagnetic reciprocating compressors or pumps, particularly compressors for pumping gas such as air. Such devices can also act as vacuum pumps, but the term "compressor" will be used generally in this specification for convenience.
BACKGROUND TO THE INVENTION
International patent applications PCT/GB94/01193, PCT/GB94/01194, PCT/GB94/01195, published as WO 94/28306, WO 94/28307 and WO 94/28308 respectively, and deriving from one of the inventors of the present application, describe a compressor which provides a number of improvements in the art. Reference should be made to these applications, hereinafter called "the earlier applications", for background discussion of such compressors and for details of the compressor described in those applications.
The present invention seeks to provide some modification and improvement of the compressor of the earlier applications. Particularly the present invention is concerned with the problem of reducing wear, particularly uneven wear, of the sliding surfaces of the reciprocating piston. In addition the invention is concerned with improving the ease of manufacture and assembly of the compressor.
It is well known in electromagnetic reciprocating compressors to provide a helical compression spring which causes the return stroke of the piston. In the earlier applications, particularly WO 94/28306, it is described how inherent defects in the compression spring or misalignment in its mounting can cause the spring to apply unsymmetric force to the piston, resulting in uneven wear.
It is known from GB-A-2241287 in a double-acting electromagnetic compressor, in which the piston alternately compresses gas in two opposed working chambers, to mount two compression springs which restore the piston to a neutral position inside the respective working chambers.
It is known from EP-A-509660 to locate a return spring around the piston and partly in the cylinder of the compressor outside the working chamber of the cylinder.
SUMMARY OF THE INVENTION
According to the present invention in one aspect there is provided an electromagnetic reciprocating compressor having a body, a piston reciprocating in the body, and an electromagnetic drive for the piston, the piston having a piston head which slides in a cylinder in the body to effect compression of fluid in the cylinder during operation of the compressor and, axially spaced from the piston head, a piston guide member slidingly movable on a piston guide surface provided by the body, the piston carrying an armature forming part of said electromagnetic drive, the compressor having a compression spring arrangement comprising at least one helical compression spring acting to drive the piston axially, which spring is mounted around the piston and is at least partly located within the cylinder during at least part of the piston stroke but is outside the working volume of fluid undergoing compression, characterised in that, for replacement or maintenance, the piston including the armature and the piston guide member is removable from the body through the end of the cylinder remote from the piston guide surface. Typically therefore the compression spring acts at one end on a surface of the piston which is outside the working chamber, in which the fluid is compressed.
The invention is especially applicable to a single-acting compressor, i.e. one in which there is only one working chamber in which fluid is compressed by the action of the piston and the piston has a single piston head surface which faces the working chamber.
Preferably the compression spring acts at one end upon a rear face of the piston head.
Preferably the or each compression spring is freely rotatable at at least one end relative to the piston. There may be a single compression spring, but preferably two such springs are employed in the spring arrangement, with at least one of the springs being at least partly in the cylinder. Most preferably there are a pair of helical springs of opposite helical coiling sense acting in series
REFERENCES:
patent: 3171585 (1965-03-01), Gauss
patent: 3588291 (1971-06-01), Corwen
patent: 4636150 (1987-01-01), Falk et al.
patent: 5100304 (1992-03-01), Osada
patent: 5275542 (1994-01-01), Terauchi
patent: 5597294 (1997-01-01), McGrath
patent: 5603612 (1997-02-01), McGrath
patent: 5727932 (1998-03-01), McGrath
Hannagan Angus Patrick Douglas
McGrath Michael Alan
Freay Charles G.
Pegasus Airwave Limited
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