GB2191964A

GB2191964A - Reciprocating piston compressor manufacture

Info

Publication number: GB2191964A
Application number: GB08615635A
Authority: GB
Inventors: Reginald Hennessey
Original assignee: Lec Refrigeration Ltd
Current assignee: Lec Refrigeration Ltd
Priority date: 1986-06-26
Filing date: 1986-06-26
Publication date: 1987-12-31
Also published as: GB8615635D0

Abstract

The body 28 of the compressor has a standard cylinder bore D and can be adapted to anyone of a predetermined range of compressor displacements by milling an over-length end of the cylinder to a required compression height C. A corresponding crankshaft 12, 25 is selected from a range of crank shafts of different throws. Thus, the number of components required for all the compressors in the given range is reduced. <IMAGE>

Description

SPECIFICATION Reciprocating piston compressor This invention relates to a method of manufacturing a motor driven hermetically sealed reciprocating piston compressor and to a compressor made by the method.

Such compressors are required in a range of displacements and this has usually been achieved by varying the piston height and the cross-bore to crown distance. Each different size of compressor has required at least two different components and the problem with which this invention is concerned is reducing the number of different components required to make all the compressors in the range.

This probiem is solved according to the invention by providing a body-casting having a cylinder with an over-length end that can be milled to a required compression height and selecting a crankshaft having a throw appropriate to the intended compressor displacement from a range of crankshafts of different throws.

Accordingly the invention provides a method for manufacturing compressors having a range of displace ments including the steps of: providing body blanks having cylinder blanks and means defining a position of an eventual crankshaft bearing; forming cylinders of constant dimension in the cylinder blanks; removing from an end of the cylinder blank remote from the eventual crankshaft bearing a variable depth of material appropriate to the displacement of the eventual compressor; and fitting into the eventual compressor a crankshaft having a throw appropriate to the intended displacement of the compressor and selected from a range of crankshafts having different throws.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of the compressor with the upper case removed to reveal the working parts; Figure 2 is a sectional view of the compressor on the line A-A of Figure 1 with the upper case fitted; Figures 3 and 4 are longitudinal vertical sections of a body casting forming part of the compressor of Figures 1 and 2 prior to and after machining respectively; Figure 5 is a plan of the machined body casting; and Figure 6 is a fragmentary section of the compressor in the region of a cylinder and connecting rod thereof.

In the drawings, a gas compressor, e.g. for use in a domestic refrigerator or freezer, comprises a case assembly 1 in which a resilient internal suspension 14 mounts a stator assembly 11 of an electrical drive motor having a rotor assembly 13. Rotation of the assembly 13 is imparted to a crankshaft and dipper tube assembly 12 that is supported for rotation in an aluminium loose main bearing 20 that is bolted at 19 to body assembly 3. The crankshaft and dipper tube assembly 12 carries an eccentric 25 that passes through an end of an aluminium connecting rod 7 whose other end is held by gudgeon pin 26 to a piston 27 that is reciprocally slideable in a cylinder 28 forming part of the body 3. The cylinder 28 is closed at its free end by valve plate assembly 4 and by an aluminium cylinder head 6.The use of aluminium for the cylinder head 6, loose main bearing 20 and connecting rod 7 reduces weight and cuts down on noise. As the rotor assembly rotates the piston 27 is reciprocated in cylinder 28 and effects compression of refrigerant vapour in manner known per se.

Low pressure super heated vapour entering the compressor from the interior of case assembly 1 via inlet side 29 is output as refrigerant high pressure super heated vapour in discharge coil 2.

In order to vary the compression capacity without altering the dimensions of the piston 27 the diameter D of the cylinder 28 is maintained constant and instead the compression height C (Figure 6) and the stroke (L or 2X in Figure 6) are altered together with the length Y of the cylinder. Practical dimensions of X, A and Y as marked in Figure 6 for a range of compressors are shown in the table below:: Mode Capacity Stroke Dimension Dimension No CC 2X A Y 1 2.7 0.375" 2.474" 1.305" (9.525mm) (62.840mm) (33.147mm) 2 3.2 0.438" 2.506" 1.337" (11.125mm) (63.652mm) (33.960mm) 3 4.0 0.562" 2.568" 1.399" (14.275mm) (65.227mm) (35.535mm) 4 5.4 0.750" (19.050mm) In the table the stroke 2X is given by twice the distance between the axis of the eccentric 25 and the axis of rotation of the crankshaft and dipper tube assembly 12 and A is the distance from the axis of rotation of the crankshaft to the far end face of the cylinder. With a bore of 0,75a (19.050 mm) the displacement can vary, e.g.

from 2.7 cue to 5.4 cc.

The body casting 3' containing a cylinder blank 28' is shown in Figure 3. The dimension of bore D is standard to the whole range of displacements of the eventual compressors and the distance from the axis of a through-hole 30 to the far end face of the blank 28' is 2.750" (69.850 mm), which is greater than the dimension A for any compressor in the range. The far end of the unmachined blank is simply milled to give the appropriate dimension A as shown in Figure 4. The body may therefore be maintained standard until a late stage in manufacture, and the only component that varies is the crankshaft whose throw is different depending upon the displacement of the compressor being manufactured.

Claims

1. A method for manufacturing compressors having a range of displacements including the steps of: providing body blanks having cylinder blanks and means defining a position of an eventual crankshaft bearing; forming cylinders of constant dimension in the cylinder blanks; removing from an end of the cylinder blank remote from the eventual crankshaft bearing a variable depth of material appropriate to the displacement of the eventual compressor; and fitting into the eventual compressor a crankshaft having a throw appropriate to the intended displacement of the compressor and selected from a range of crankshafts having different throws.

2. A method according to claim Claim 1, wherein a cylinder head, loose main bearing and connecting rod of the compressor are of aluminium.

3. A method for making a compressor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

4. A method for making a compressor including the steps of milling to a standard length on over-length end of a cylinder blank and selecting a crankshaft having a throw appropriate to the intended displacement from a range of crankshafts of different throws.

5. A compressor made by the method of any of Claims 1 to 4.