US3034703A - Compressor construction - Google Patents

Description

y 1962 c. E; FETTER 3,034,703

COMPRESSOR CONSTRUCTION Filed May 16, 1960 mmvrox CARL E. F'ETTER.

HlS ATTORNEY United States Patent 3,634,703 COMPRESSOR CONSTRUCTION Carl E. Fetter, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed May 16, 1960, Ser. No. 29,495 2 Claims. (Cl. 230-238) The present invention relates to a compressor construction and is more particularly concerned with an improved compressor discharge head or muflle box construction for obtaining a gasketless seal between the compressor head and a flat surface of a mating compressor component.

In the manufacture of small hermetic compressors such as those used in the refrigeration industry, difiiculty is frequently encountered in providing a gas-tight seal between the compressor head and the block or cylinder portion of the compressor. The use of the usual soft gasketing materials in such compressors is to be avoided since such materials may not last the life of the compressor under normal operating conditions. For that reason it is desirable that the joint between the compressor head and the cooperating compressor surface be a gasketless one. As a result, the mating surfaces forming the joint are normally machined to close tolerances with the expectation that carefully matched surfaces of sufficient area plus sufficient clamping pressure will provide a gastight seal between these surfaces.

The present invention is based on the discovery that an improved gas-tight seal can be obtained between the discharge head and a mating portion of a small or fractional horsepower compressor by relieving selected areas,

of one of the contacting surfaces with the result that while the total joint or contact area is substantially reduced, a much improved joint seal is obained.

The invention will be particularly described with reference to a reciprocating compressor including a valve plate overlying the one end of the compressor cylinder block and a compressor discharge head or muffle box secured in engagement with the flat upper surface of the valve plate by suitable bolts. Since the discharge cavity in the compressor discharge head contains high pressure gas, it is essential that the joint between the valve plate and the compressor discharge head be gas-tight.

In accordance with the present invention, there is provided a compressor including a cylinder block, a compressor discharge head or closure member and a valve plate between the block and the head and provided with 'a discharge valve through which compressed gas is discharged from the compressor cylinder into a discharge chamber in the head. The valve plate may be separately secured to the cylinder block but for convenience both it and the compressor head are clamped to the compressor block by means of bolts extending through both the head and the valve plate and threadably engaging the block. The valve plate, which in effect forms one wall of the discharge chamber in the compressor head, is provided with a smooth upper surface which is engaged by the compressor head. In order to provide a gas-tight gasketless seal between the plate and the head, the discharge head is so designed that the clamping pressure of the bolts used to secure the head to the compressor block surface of which is provided with a centrally located circular cavity partially forming the compressor discharge chamber. The upper surface of the discharge head includes relieved areas at each of the four corners thereof and a bolt receiving opening in each of these areas extending through the body for receiving the fastening bolts. These openings are positioned so that center lines joining the centers of adjacent bolt openings are substan tially tangent to the circular Wall defining the discharge cavity, or in other words, the cavity has a diameter approximately equal to the distance between the adjacent bolt openings. In order that the clamping pressures provided upon tightening of the bolts at each corner of the head will be distributed over the lower surface of the compressor discharge head and clamp the surface into sealing engagement with the valve plate, the lower surface has certain areas thereof relieved around the bolt openings and between the four corners and the cavity to form recesses extending diagonally across each of the four corners of the discharge head. Each of these recesses intersect adjacent sides of the discharge head body and is defined by an inner curved wall disposed inwardly from the bolt opening encompassed thereby and is formed by an arc of the circle whose diameter is the center of the opening in the opposite corner of the body. The outer wall of each recess extends diagonally across the lower surface of the discharge head body outwardly from the bolt opening to define with the adjacent corner of the lower surface a bearing surface or pad for supporting that corner. In addition, the discharge head body is charge head of the present invention;

FIG. 3 is a perspective view of the discharge head illus trating certain details of construction thereof;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2 and FIG. 5 is a sectional view of a portion of the compressor taken along line 5--5 of FIG. 2.

Referring to the drawing, the compressor as illustrated is sealed within a hermetic casing 1 and comprises a cylinder block 2. supported on a frame 3 and including a cylinder '4. A valve plate 6 and a compressor discharge head 7 are clamped by suitable bolts 8 to the block 2. In the operation of such a compressor in a refrigerating system, refrigerant is drawn into the cylinder 4 through intake ports (not shown) and is compressed by the piston 10. The compressed refrigerant passes through discharge ports 11 shown in FIG. 5 into a discharge chamber or cavity 12 provided in the head 7 from which the compressed refrigerant leaves through a discharge line :14.

In accordance with the present invention the head 7 which is designed to be clamped in sealing engagement with the upper flat surface 15 of the valve plate 6 comprises a substantially square body portion secured to the cylinder block 2 by means of four bolts 8 extending through the four corners of the compressor discharge head 7. The upper surface 17 of the head is relieved at the four corners over areas surrounding the bolt receiving openings 18 in order to recess the heads of the bolts and also for the purpose of thinning these portions of the head for the purposes which will become more apparent hereinafter. Each of these relieved areas is defined in part by a cylindrical Wall or shoulder portion 19 defined by an arc of a circle whose center line is the adjacent head 7 which engages the surface 15 of the valve plate 6 is also relieved adjacent the four corners thereof to form four recesses 23 between the corners 20 of the cylinder head body and the circular peripheral edge or side wall 24 of the cavity 12. The particular shape of these recesses 23 and their spacing and relationship to the side wall 24 of the cavity 12 have been found to provide a gas-tight seal when the head 7 is bolted into engagement with the valve plate 6.

To this end the cylinder head body is so constructed that the diameter of the cavity 12 is approximately the same as the distance between the center lines of the adjacent bolt receiving openings 18 on each side of the compressor head. In other words lines joining the centers of adjacent bolt receiving openings 18 are approximately tangent to the circular side wall 25 of the cavity 12. With this relationship between the bolt holes 18 and the cavity 12, the inner walls 24 of the recesses 23 overlying or surrounding each of the openings 18 are defined by the arc of a circle which has as its center the center line of the opening 18 in the diagonally opposite corner of the head as illustrated by the broken line 27 in FIG. 2. Thus with the bolt receiving openings 18 on lines tangent to the circular edge 24 of the cavity 12 and with the walls 24 of the recesses 23 being of the described arcuate shape, there is formed an annular unrelieved bearing surface 28 between recesses 23 and the cavity 12. This surface is of varying Width and as is illustrated in FIGS. 2 and 3 of the drawing is relatively narrow adjacent each of the bolt holes 18 as indicated by the numeral 29 and is widest at points between adjacent bolt holes as indicated by the numeral 30.

The outer wall 31 of each of the recesses 23 is defined by a line extending diagonally across each corner of the cylinder head outwardly from the adjacent opening 18 to form relatively small pads 33 at each of the four corners, which pads are of the same height as the surface 28 and which engage the upper surface '15 of valve plate to provide means whereby the bolts 8 as they are tightened can impart the proper clamping of the surface 28 in sealing engagement with plate 6. In order that this sealing pressure will be obtained relatively uniformly, it has also been found that the arcuate walls 24 defining the recesses 23 should intersect at points 35 which are on the outer edges of the cylinder head or inwardly therefrom in order to limit the size of these bearing areas remote from the bolts 8. If these areas are too large, it has been found that a fluid-tight seal will not be obtained. For example, it has been found that if the inner walls 24 of the recesses are formed by straight lines running diagonally across each corner of the cylinder head to intersect beyond the respective side edges of the cylinder head, the resultant larger bearing areas between adjacent bolt openings 18 will inter-[ere with the proper sealing of the head and plate at points intermediate adjacent bolt openings.

Likewise the above described shape and configuration of the compressor head has been found to be superior for the formation of a hermetic joint between the head and the plate 6 to other configurations such as that obtained by omitting the relieved areas in the upper surface 17 around the heads of the bolts 8. In fact it appears that a number of factors contribute to the gas-tight seal btainable by a compressor head of the described configuration. For example, while the pads 33 at each corner of the head are deformed or compressed to a slight extent as bolts 8 are tightened, they provide a leverage action whereby the clamping forces of the bolts are distributed through the relatively thin and somewhat flexible sections 38 of the compressor head formed by the overlapping relieved areas on the top and bottom surfaces of the head to the thicker center portions overlying the bearing surface 28. During tightening of each of the bolts these clamping forces first reach the narrower sections 29 of the surface 28 and as the pressures increase these areas may flow to a slight extent. At the same time the clamping forces spread to the more remote and wider portions 30 of the surface 28. These areas 39 are then pressed into gas-tight contact with the plate 6 to form a seal about the entire cavity 12 which is believed to be concentrated along a line at or adjacent the edges of the surface 28 formed by the arcuate walls 24.

While the invention is illustrated in connection with a specific type of a compressor, various modifications thereof will be apparent to those skilled in the art. It is not, therefore, desired that the invention be limited to the specific details illustrated, and is intended by the appended claims to cover all modifications that fall within the spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the 'United States is:

l. A compressor closure member adapted to be secured to a flat surface of a compressor and form a gasketless, gas-tight seal therewith comprising a one-piece substan tially square body having an upper surface including relieved areas at the four corners thereof, an opening in each of said areas extending through said body for receiving fastening bolts to secure said closure member in engagement with said compressor surface, said body comprising a fiat lower surface for engaging said fiat compressor surface and including a circular cavity for receiving pressurized gas from the compressor, said cavity being centrally located with respect to said openings and having a diameter approximately equal to the distance between the adjacent openings, said lower surface also having portions thereof relieved in the area of each of said openings and intermediate each of the four corners of said lower surface and said cavity to form a diagonally extending recess adjacent each corner, each of said recesses intersecting adjacent sides of said body and being defined by an inner curved wall inwardly from the opening in that corner and formed by the arc of a circle whose center is the center of the opening in the opposite corner of said body and an outer wall extending diagonally across said surface outwardly from the opening in that corner to define with the adjacent corner of said surface a bearing surface for supporting said corner, said inner curved walls of adjacent recesses intersecting at least within the area of said surface, said recesses defining with said cavity a substantially annular sealing surface for sealing engagement with said compressor surface.

2. A compressor closure member adapted to be secured to a fiat surface of a compressor and form a gasketless, gas-tight seal therewith comprising a one-piece substantially square body having an upper surface including relieved areas at the four corners thereof, an opening in each of said areas extending through said body for receiving bolts to secure said closure member to said compressor, said body including a lower surface for engaging said fiat compressor surface and including a circular cavity for receiving pressurized gas from the compressor, said cavity being centrally located with respect to said openings and having a diameter approximately equal to the distance between the adjacent bolt receiving openings, said lower surfaces having areas thereof relieved around said openings and between the four corners of said lower surface and said cavity to form recesses adjacent each corner, each of said recesses intersecting adjacent sides of said body and being defined by an inner curved wall inwardly from the opening in that corner and formed by the arc of a circle whose center is the center of the opening in the opposite corner of said body and an outer wall extending diagonally across said surface outwardly from the adjacent openings to define with the adjacent corner of said surface a bearing surface for supporting said corner, said inner curved walls of adjacent recesses intersecting at least within the area of said surface, said recesses defining with said cavity a sealing surface for sealing engagement with said compressor surface.

No references cited.

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