Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1999-08-24
2001-09-11
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S493000, C277S546000
Reexamination Certificate
active
06286837
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the combination or set of packing rings disposed in a packing cup around a gas compressor piston rod to limit the escape of a compressed gas from a compressor cylinder along its reciprocally movable piston rod during operation of the compressor.
This invention relates to the combination or set of packing rings disposed in a packing cup around a gas compressor piston rod to limit the escape of a compressed gas from a compressor along its reciprocally movable piston rod during operation of the compressor. The term “packing ring” as used herein means a ring which is or can be compressed on and around a gas compressor piston rod to form a seal to limit the escape of gas along the piston rod past the seal during at least a portion of a cycle of the piston rod from commencement of a compression stroke to completion an immediately succeeding return stroke.
Each of the individual rings making up the ring combination of this invention are old and well known in the prior art and have long been used alone or in combination with other types of rings in gas compressors. Nevertheless, the particular combination of ring types to which this invention is directed is believed to be novel and will provide enhanced service life as compared to prior art compressor piston rod packing ring combinations. To enhance the service life of a set of rings used in a packing cup around a piston rod, it would be desirable that different ones or pairs of rings in the combination encounter most of the gas compression loading to compress the rings upon the piston rod, during different portions of the compression and return strokes of the reciprocating compressor rod. No prior art combination of packing rings is believed capable of achieving such a result.
By means of my invention, these and other shortcomings of prior art compressor piston rod packing ring combinations are substantially overcome.
SUMMARY OF THE INVENTION
It is an object of my invention to provide a novel piston rod packing for a gas compressor.
It is a further object of my invention to provide a set of rings for a piston rod packing of a gas compressor wherein different rings within the set incur gas pressure differential loading on a piston rod at different times during each compression stroke of the piston rod, depending on whether the gas cylinder pressure is at a low, intermediate or high value, relatively speaking.
Briefly, in accordance with my invention, there is provided, in a packing ring set for a piston rod of a gas compressor which includes a first split packing ring containing a first plurality of arcuately extending segments arranged to form a first annulus wherein opposing ends of successive pairs of said segments each form a joint. A second split packing ring is included which is disposed next to and on a low pressure side of the first ring as measured during a compression stroke of a piston rod of the compressor. The second ring includes a second plurality of arcuately extending segments arranged to form a second annulus. Opposing end portions of successive pairs of the second segments each form a joint. The first and second rings are both mechanically and pneumatically compressible on the piston rod at cylinder gas pressures of the compressor which are less than a preselected intermediate value. A third uncut packing ring is provided which is disposed next to and on a low pressure side of the second ring as measured during the compression stroke. The third ring is constructed of a non-metallic material. The third ring fits loosely on said piston rod and forms an ineffective seal for all of said cylinder gas pressures which are less than said intermediate value and is compressible against the piston rod to form an effective seal at and above the intermediate value up to a preselected high value. A fourth uncut packing ring is likewise provided and disposed next to and on a low pressure side of the third ring as measured during the compression stroke. The fourth ring is constructed of a material which is relatively less compressible than that of the third ring and is compressible on the piston rod at all cylinder pressures which are equal to and greater than the high value to form an effective seal on the piston rod in combination with the third ring. The first and second rings are only minimally compressible on the piston rod when at least one of the third and fourth rings is compressed on the piston rod to form an effective seal.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and attached drawings upon which, by way of example, only a preferred embodiment of my invention is described and illustrated.
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Delaware Capital Formation Inc.
Knight Anthony
Miller, Jr. Maurice L.
Pickard Alison K.
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