Compressor section in an easily assembled motor-compressor unit

Abstract: A preferably hermetic motor-compressor unit comprises a usual drive shaft operated by a known electric motor and acting on a compressor section (1) for a fluid, for example a refrigerant fluid, comprising a piston (3) associated with a connecting rod (2) operated by the said shaft, said piston (3) moving within the bore (23) of a corresponding cylinder (4) in which it compresses said fluid. With the connecting rod (2) there are associated means (11) arranged to forcedly cooperate with counter-means (13) associated with the piston (3) so as to connect this latter to the connecting rod (2), retention means (20) being provided to maintain the forced fit between said means and counter-means.

Description: The invention relates to a motor-compressor unit according to the preamble of claim 1. A motor-compressor unit of this kind is known from the document FR-A-2 330 923. In embodiments disclosed by this document the pin, engaged in a recess, is maintained in the recess by retention means constituted by spot welding and/or by deformations of the flanks of the recess. These known solutions require relatively expensive welding and/or cold deformation (upsetting) equipment. The object of the invention is to provide a motor-compressor unit of the kind considered, in which the pin, once fitted in its recess in the piston, can be easily and firmly secured in the recess without the use of expensive equipment. According to the invention this object is attained by a motor-compressor unit as claimed. Thanks to this solution a pin can be firmly secured in its recess in a piston by simply inserting the retention member within the wall of the piston and bringing the retention member to cooperate by interference with the wall of the piston. This may be done with the aid of a simple mechanical tool. The present invention will be more apparent from the accompanying drawing, which is provided by way of non-limiting example and in which: Figure 1 is an exploded view of a part of the compressor section of the motor-compressor unit according to the invention; and Figure 2 is a longitudinal sectional view of that part of the compressor section shown in Figure 1, but in the assembled state. With reference to said figures, a motor-compressor unit, for example of hermetic type for use in a refrigerator, freezer or the like, comprises a section 1 for compressing a refrigerant fluid of known type. The section 1 is indicated for simplicity as a compressor section and comprises a connecting rod 2, a piston 3 and a cylinder, with one end of which there is associated a usual valve plate. The connecting rod 2 comprises an end 7 associated in known manner with a usual rotating shaft driven by a known electric motor (both not shown), an arm 8 extending from said end and terminating in an end 9 comprising an eyelet 10 in which a pin 11 is arranged. The end 9 and the pin 11 are inserted into mutually perpendicular recesses 12 and 13 in a depressed part 15 of the piston 3 bounded by a wall 16 rising from said part. Specifically, the recess 12 contains the eyelet end 9 of the connecting rod 2, and the recess 13 contains the pin 11 as a forced fit. At least this latter recess has a cross-section of broken-line shape (see Figure 2) to facilitate the forced cooperation of the pin with the recess and hence with the depressed part 15 of the piston 3. This forced cooperation secures the piston to the connecting rod 2. In order to improve and ensure the connection an elastic ring 20 is associated with the connecting rod 2, and after inserting the pin 11 into the respective recess 13 is able to cooperate with said pin and with the wall 16 of the piston 3. More specifically, the ring 20 comprises a substantially flat annular part 21 from which portions 22 project radially outwards from the ring in a direction preferably inclined to the annular part, said portions defining a sort of flared interrupted rim, the wall of which (defined by said portions) lies on the lateral wall of a cone with its vertex facing the piston 3. During the construction of the compressor section 1 the connecting rod 2 is connected to the piston 3 by inserting the end 9 into the recess 12 and fitting the pin 11 into the recess 13 in the piston. The ring 20 is then inserted into this latter so that its portions 22 cooperate by interference with the wall 16 which rises from the part 15 of the piston. The ring retains the end 9 and the pin 11 in their respective seats and ensures a reliable connection between the piston and the connecting rod.

Claims: A motor-compressor unit comprising a cylinder, a piston (3) moving within the cylinder for compressing a fluid, a crankshaft operated by an electric motor, a connecting rod (2) operated by the crankshaft, and a pin (11) carried by one end (9) of the connecting rod (2) and connecting the latter to the piston (3), wherein the piston (3) has a depressed part (15) bounded by a wall (16) raising from said depressed part (15), and a recess (13) in the depressed part (15), the pin (11) is engaged in the recess (13) with a forced cooperation, and retention means (20) are provided to maintain the pin (11) in the recess (13), characterised in that said retention means comprise a retention member (20) which is distinct from the piston (3), is installed within the piston (3) with an interference fit with said wall (16) and is in engagement with the pin (11). A motor-compressor unit according to claim 1, characterised in that the retention means are in the form of an elastic ring (20) which cooperates with the piston pin (11) and, with an interference fit, with said wall (16) of the piston (3). A motor-compressor unit according to claim 2, characterised in that the elastic ring (20) comprises a substantially flat annular part (21) and portions (22) projecting radially outwards from the ring (20) and cooperating by interference with the wall (16) of the piston (3). A motor-compressor unit according to claim 3, characterised in that said radially projecting portions (22) project from the ring (20) in an inclined direction with respect to the annular part (21), said portions (22) defining a flared interrupted rim which lies on the lateral wall of a cone with its vertex facing the piston (3). A motor-compressor unit according to any of claims 1 to 4, characterised in that a further recess (12) is provided in said depressed part (15) and said further recess (12) contains the end (9) of the connecting rod (2) which carries the pin (11). A motor-compressor unit according to claim 5, characterised in that said further recess (12) is positioned in the depressed part of the piston (3) in a direction perpendicular to that of the recess (13) with which the pin (11) cooperates. A motor-compressor unit according to any of the preceding claims, characterised in that the recess (13) with which the pin (11) cooperates has a cross-section of broken-line shape.

Inventors: BIANCHI VITTORIO, MAIRONI GIUSEPPE, BIANCHI, VITTORIO, MAIRONI, GIUSEPPE, BIANCHI, VITTORIO, WHIRLPOOL ITALIA S.R.L., MAIRONI, GIUSEPPE, WHIRLPOOL ITALIA S.R.L.
Applicants: WHIRLPOOL EUROP, WHIRLPOOL EUROPE B.V.
Application year: 1993
Main classification: F04B53
IPC codes: F04B39, F04B53, F16J1