Gas compressor having a variable-volume clearance pocket

Abstract: A compressor (10) has a straight cylinder (12) wholly confined within which are inlet valves (28, 34) and reciprocatable discharge valves (50, 52). One inlet valve (34) is set in place by a centerbolt (32) which can be turned by a wrench (or the like) to move the inlet valve (34) to selected positions relative to a confronting discharge valve (50), whereby the volume of the clearance pocket between these valves is varied; the centerbolt mounted inlet valve (34) serves as a device for selectively varying the clearance pocket volume, thereby obviating any need for special clearance pocket varying devices or components.

Description: This invention pertains to gas compressors, especially those of the reciprocating piston type, and in particular to a gas compressor of the aforesaid type which has a variable-volume clearance pocket, and to means for varying a clearance pocket in such a gas compressor. The clearance volume or clearance pocket of gas compressors is normally varied to alter the capacity of the compressor by extraneous devices and/or components attached to the cylinder head such devices or components being designed to satisfy that very function; vary the volume or pocket obtaining between the piston and the cylinder head. It is an object of this invention to obviate the need for extraneous or special devices and components for varying the volume of the clearance pocket by setting forth a gas compressor devoid of such but which can effect the adjustment in any event and by disclosing , as well, means for varying a clearance pocket in a gas compressor, without resort to the aforesaid special devices and components. The invention is an improvement in the inventions set forth in US-A-5,011,383 and US-A-5,015,158. For an understanding of the nature of the valves and the general assembly of the present gas compressor, reference is directed to the cited patents for such background, both patents are incorporated herein by reference. US-A-5,015,158 discloses a gas compressor according to the preamble of claim 1. The present invention is characterized by the features of the characterizing portion of claim 1. The invention will now be explained in more detail by way of example only in the following non-limitative description to be read in conjunction with the accompanying drawings, in which: FIG. 1 is a perspective illustration of a gas compressor having a variable-volume clearance pocket according to an embodiment of the invention; and FIG. 2 is an exploded view in perspective of the outer head assembly of the compressor of FIG. 1, the same comprising the novel means for selectively varying a clearance pocket. As shown in the figures, the compressor 10 according to an embodiment of the invention, comprises a single straight cylinder 12 having a longitudinal axis 14 and a circumferential wall 16. Inner and outer headers 18 and 20 respectively are secured to opposite axial ends of the cylinder 12 by four tie bolts 22 (only two of which are visible). The inner header 18 has a threaded bore 24 formed centrally therein to receive a hollow inlet valve mounting bolt 26. Bolt 26, of course, secures an inlet valve 28 in place within the cylinder 12. The outer header 20 also has a tapped bore 30 formed centrally therein to receive a centerbolt 32 which similarly secures a second inlet valve 34 in place within the cylinder 12. The outer header 20 also has a larger threaded bore 36, coaxial with bore 30, formed therein for a purpose which is explained in subsequent text. The inlet valves 28 and 34 are so positioned in the cylinder that they are adjacent to, and open to, inlet ports 38 and 39. Outwardly flanged conduits 40 and 42 are fixed in communication with the ports 38 and 39. Another outwardly flanged conduit 44 is fixed to a discharge or outlet port 46 (not visible) which is formed in the wall 16 intermediate the axial ends of the cylinder 12. A piston rod 48 is slidably received in inlet valve 28 mounting bolt 26. It has a first end which projects outwardly from header 18 for coupling thereof to a prime mover (not shown) and a second end which extends inwardly from the header. The second inner end of the rod 48 mounts a pair of discharge valves 50 and 52 thereon, and spaced apart along the rod end. All the valves; inlet valves 28 and 34, and discharge valves 50 and 52, are the same as, or virtually the same as, the valve described in the aforecited US-A-5,011,383 and, accordingly, it is deemed unnecessary to detail the structure thereof here. Too the valves are fixed to their headers 18 and 20, and to the piston rod 48, as detailed in the indicated US-A-5,018,158, and function as described in said patents, with one significant difference. In the aforenoted patents that which corresponds to the outer header 20 had no throughgoing bore. As priorly noted, outer header 20 has the tapped bore 30 in which to receive the centerbolt 32 as a means of fixing the inlet valve 34 in a given relationship to discharge valve 50. Too header 20 also has the larger, untapped bore 36 in which to accommodate an outwardly projecting portion of the centerbolt 32. The outward terminal end of the centerbolt 32 has flats 54 (only one is visible) formed thereon to receive a wrench or like tool threadedly to turn the centerbolt 32 inwardly or outwardly relative to the cylinder 12. By thus turning the centerbolt 32, the clearance volume or pocket which obtains between valve 34 and valve 50 is enlarged or diminished to vary the capacity of the compressor 12. Consequently, it is the inlet valve 34 itself via its mounting centerbolt 32 which offers a selective variable-volume clearance pocket. Bore 36 in header 20 defines an abutment 56 where it joins the bore 30. The same provides a limit stop for the inward travel of the centerbolt 32 in that the latter carries a dowel 58 radially therein with a projecting portion. The projecting portion of the dowel 58 is unobstructed as it traverses the bore 36 but prevents further inward travel of the centerbolt 32 as the projecting portion impinges against the abutment 56 and valve 34 carried by centerbolt 32 is fixed in an innermost setting. An acorn nut 60 is threadedly coupled to the end of the centerbolt 32 and made fast against the header 20. It shields the end of the centerbolt so that once a setting of the variable volume of the clearance pocket is made it will not inadvertently be disturbed. Too the acorn nut 60 has an abutment 62 therewithin for defining an outermost limit of travel of the centerbolt 32. If the acorn nut 60 will thread onto the centerbolt 32 but cannot be made fast up against the header 20 it will clearly indicate that the centerbolt is outwardly turned too far.

Claims: A gas compressor (10) comprising: a single straight cylinder (12) having (a) a longitudinal axis (14), and (b) a circumferential wall (16); and headers (18, 20) secured to opposite, axial ends of said cylinder; a first inlet valve (34) associated with one header (20); wherein the other of said headers (18) has a hole (24) formed centrally therein which opens into said cylinder and which is threadedly tapped; a second inlet valve (e.g. 28) removably secured in said centrally-formed hole in said other header (18); said second inlet valve (28) has a through-going bore formed centrally therein; a piston rod (48) in slidable penetration of said bore in said second inlet valve (28), and having a first end thereof projecting outwardly from, and a second end thereof extending inwardly from, said other header; a pair of discharge valves (50, 52) coupled to said second end of said piston rod (48), and spaced apart along the second end thereof, confined within said cylinder; gas inlet ports, (38, 39) radially formed in said wall (16) adjacent opposite axial ends of said cylinder (12), and opening in proximity to said inlet valves (28, 34); and a gas outlet port (46) formed in said wall (16) intermediate said axial ends of said cylinder (12); characterised in that said one header (20) also has a hole (30) formed centrally therein which opens into said cylinder (12) and is threadedly tapped; said first inlet valve (34), one of said discharge valves (50), and said wall (16) define a clearance pocket at one of said axial ends of said cylinder (12); said first inlet valve (34) has a centerbolt (32) an end of which is threadedly in penetration of said tapped hole in the said one header (20); which end of the centerbolt has a tool-engageable configuration; an acorn nut (60) threadedly engaged with the said end of said centerbolt (32) and made fast against the one header (20); and wherein the nut (60) has an annular abutment (62) and the centerbolt (32) has means extending therefrom, engageable with said abutment (62) such that the nut (60) cannot be made fast up to said one header (20) when the centrebolt (32) is outwardly turned too far. A gas compressor according to claim 1, wherein the said one header (20) and the centerbolt (32) have means (56) cooperative for delimiting a threadedly inward penetration or travel of said centerbolt (32) relative to the header. A gas compressor according to claim 1, wherein the said one header (20) has an annular abutment (56); and the centerbolt (32) has means (58) extending therefrom and engageable with said abutment (56) for delimiting a threadedly inward penetration or travel of the centerbolt relative to the header. A gas compressor according to claim 3, wherein the abutment engageable means of the centerbolt (32) comprises a dowel (58) set in the centerbolt and having an end thereof projecting radially from the centerbolt. A gas compressor according to claim 4, wherein the said one header (20) further has an untapped bore (36), coaxial with its tapped bore (30), and the end of said dowel (58) travels through the said untapped bore, upon the centerbolt (32) being threadedly turned inwardly and outwardly relative to the header. A gas compressor according to any preceding claim including means for reciprocating said discharge valves to compress gas within said cylinder (12).

Inventors: BENNITT ROBERT A, BENNITT, ROBERT A.
Applicants: DRESSER RAND CO, DRESSER-RAND COMPANY
Application year: 1992
Main classification: F04B49
IPC codes: F04B49, F04B3