Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-09-24
2001-02-20
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S315000, C092S013300
Reexamination Certificate
active
06190137
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention pertains to reversible reciprocating piston machines, and particularly to reversible reciprocating piston compressors.
Reciprocating piston compressors, such as the compressor disclosed in U.S. Pat. No. 5,281,110, which is assigned to the present assignee, the disclosure of which is incorporated herein by reference, are generally of fixed displacement and powered by an rotating driving source which operates in a single direction. Also known in the art are reversible reciprocating piston compressors in which a piston has a first stroke length when driven by a crankshaft rotating in a first, forward direction, and a second stroke length when driven by the crankshaft rotating in a second, reverse direction, through use of an eccentric cam which rotates relative to the crankshaft between stops thereon corresponding to first and second angular cam positions which, in turn, correspond to the first and second stroke lengths. These reversible compressors provide the advantage of having one displacement when the crankshaft is rotated in the forward direction, and another displacement when the crankshaft is rotated in the reverse direction. Typical variable stroke, reversible drive compressors, however, do not provide means for positively maintaining the cam in the angular position corresponding to the greater stroke length during rotation of the crankshaft. If the cam is not continually maintained in this angular position during crankshaft rotation, the reexpansion of gas in the cylinder after the piston reaches top-dead-center (TDC) may force the piston away from its TDC position at such a speed that the cam may rotate relative to the crankshaft, separating the cam and crankshaft stops. The separation of these stops result in their subsequently slamming together as the rotating crankshaft catches up to the cam, causing considerable component stresses, adversely affecting durability, and producing undesirable noise.
U.S. patent application Ser. No. 09/099,013, filed Jun. 17, 1998, now U.S. Pat. No. 5,951,261, which is also assigned to the present assignee, the disclosure of which is also incorporated herein by reference, provides a means of preventing separation of the cam and crankshaft stops by locking the cam to the crankshaft in a particular angular position when the crankshaft rotates in one of two directions. According to that disclosure, under the influence of centrifugal force, a latching member comprising a pin is slidably extended from a radial bore provided in the eccentric crankpin into engagement with a mating bore provided in the cam. While locking the crankshaft and cam together, the latching pin is subjected to substantial shear forces which may lead to partial or complete failure of the pin. A more durable means for locking the cam and crankshaft stops together, to prevent their separation upon the reexpansion of gas in the cylinder after the piston reaches TDC is desirable.
SUMMARY OF THE INVENTION
The present invention addresses the durability concerns associated with the latching pin of the above-mentioned previous reversible, variable displacement compressor. Unlike that latching pin, which is longitudinally extended between the eccentric crankpin and cam interface, and subjected to substantial shear stresses during compressor operation to prevent separation of the cam and crankshaft stops, the present invention provides a latching member which is pivoted into its operative position. The pivoting latching member of the present invention is subjected to compressive stresses in preventing such separation, thereby providing a locking means of improved durability.
The present invention provides a reciprocating piston compressor including at least one cylinder, a reciprocable piston disposed in the cylinder, a crankshaft rotatable in both a forward and a reverse direction and having a cylindrical eccentric portion, a latching member pivotally engaged with the crankshaft, a cam disposed about the crankshaft eccentric portion, the piston operatively connected to the cam, and a spring connected to one of the cam and the crankshaft, the position of the latching member influenced by the spring. The cam is rotatable about the crankshaft eccentric portion between a first cam position corresponding to a first piston stroke length during forward rotation of the crankshaft, and a second cam position corresponding to a second piston stroke length during reverse rotation of the crankshaft. In one of the first and second cam positions, the cam is rotatably locked to the crankshaft eccentric portion by the latching member.
The present invention also provides a reciprocating piston compressor including at least one cylinder, a reciprocable piston disposed in the cylinder, a crankshaft rotatable in both a forward and a reverse direction and having a cylindrical eccentric portion, a latching member, and a cam disposed about the crankshaft eccentric portion, the piston operatively connected to the cam. The cam is rotatable about the crankshaft eccentric portion between a first cam position corresponding to a first piston stroke length during forward rotation of the crankshaft, and a second cam position corresponding to a second piston stroke length during reverse rotation of the crankshaft. Means are provided for placing the latching member under compression between the cam and the crankshaft in one of the first and second cam positions, thereby rotatably locking the cam to the crankshaft.
REFERENCES:
patent: 1556912 (1925-10-01), Canoose
patent: 2035096 (1936-03-01), Schneider
patent: 2612839 (1952-10-01), Denny
patent: 3010339 (1961-11-01), Brock
patent: 3401639 (1968-09-01), Schwertfeger et al.
patent: 3738230 (1973-06-01), Censi
patent: 3796523 (1974-03-01), Albrecht et al.
patent: 4143995 (1979-03-01), Divisi
patent: 4236874 (1980-12-01), Sisk
patent: 4245966 (1981-01-01), Riffe
patent: 4248053 (1981-02-01), Sisk
patent: 4261228 (1981-04-01), Eagan, Sr.
patent: 4479419 (1984-10-01), Wolfe
patent: 4494447 (1985-01-01), Sisk
patent: 4682532 (1987-07-01), Erlandson
patent: 4830589 (1989-05-01), Pareja
patent: 4861236 (1989-08-01), Kustes et al.
patent: 5199857 (1993-04-01), Sanuki
patent: 5366355 (1994-11-01), Patterson
patent: 5560460 (1996-10-01), Ezawa
patent: 5609127 (1997-03-01), Noplis
patent: 6092993 (2000-07-01), Young et al.
patent: 6099259 (2000-08-01), Monk et al.
patent: 0 827 843 (1981-05-01), None
patent: WO 99/09319 (1999-02-01), None
Howell Raymond D.
Robbins Elizabeth A.
Westcott Timothy
Baker & Daniels
Tecumseh Products Company
Thorpe Timothy S.
Tyler Cheryl J.
LandOfFree
Reversible, variable displacement compressor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reversible, variable displacement compressor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reversible, variable displacement compressor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2596651