GB2171775A - Pivot pin locating means - Google Patents

Abstract

A pivot pin (gudgeon) (8) retainer comprises a bow-shaped length of spring steel wire (11) retained in the pin (8) with bent-over ends (9, 10) providing locating members which extend radially outward of the ends of the pin (8) to hold the latter in place. <IMAGE>

Description

SPECIFICATION Pin locating means This invention relates to pin locating means and relates especially, but not exclusively, to means locating a gudgeon pin in a piston of a piston and cylinder machine.

In a piston and cylinder machine it is usual for a connecting rod between a crankshaft and a piston to be pivotally connected to the piston by means of a gudgeon pin located in relation to the piston either by internal circlips in the lateral bore of the piston in which the gudgeon is fitted or by metal end pads retained by the cylinder walls in the ends of the lateral bore of the piston. Whereas such circlips require machined internal grooves in the piston end pads are susceptible to undesired end-play and also possible rubbing wear in relation to the cylinder walls.

The present invention provides in an assembly of a pivot pin and a receiving bore of a body locating members extending radially away from the axis of the pin and retained at the ends of the pin to restrain the pin against axial movement of the pin relative to the body, said members being conjoined by a reailient member passing through the pin.

In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawing which illustrates a sectional view of a piston of an air compressor.

Referring to the drawing a cast aluminium piston for a piston and cylinder air compressor is denoted by ref. 1 and carries compression rings 2 and 3 and an oil retaining ring 4.

The skirt 5 of the piston is cut away at the sides, namely the areas where there is negligible lateral thrust through the connecting rod 6.

The piston has a hollow gudgeon pin 7 via which it is connected to the connecting rod 6, the gudgeon pin 7 being somewhat shorter than the diameter of the piston by virtue of the aforementioned cut-aways.

The gudgeon pin 7 is a close sliding fit in the lateral bore 8 of the piston and is located centrally in relation to the piston by locating members 9 and 10 at the ends of a resilient self-retaining generally bow-shaped member 11 which bears against the interior of the axial bore of gudgeon pin 7 in a sense to urge the members 9 and 10 radially outwards in relation to the gudgeon pin. Because the member 9 and 10 are so urged radially outwards and extend beyond the diameter of the gudgeon pin they are effective to locate the latter within pre-determined tolerances centrally in relation to the piston. In order to permit a certain amount of lateral movement of the gudgeon pin in the bore of the piston the length of the gudgeon pin can be chosen to be sufficiently longer as shown in inset (a) than the distance between the extremities of the said bore.Alternatively, the gudgeon pin may be chosen to be appropriately shorter as shown in inset (b) in relation to the distance between the extremities of the bore.

Although the members 9 and 10 are shown in the drawing as simply formed of the ends of the resilient bow-shaped member 11, they may be doubled back or otherwise shaped to present more substantial bearing surfaces against the surfaces of the piston and thereby extend the useful life by reducing possible wear.

The combined locating members and resilient means is constructible from spring steel wire and a cheap and easily assembled arrangement is provided in accordance with the invention. Furthermore, such a means may be arranged if required to act as a direct substitute for conventional internal circlips by allowing the locating members to engage in the annular grooves instead of the circlips in a conventional piston.

1. An assembly of a pivot pin and a receiving bore of a body having locating members extending radially outwards away from the axis of the pin and retained at the ends of the pin to restrain the pin against axial movement of the pin relative to the body said members being conjoined by a resilient means passing through the pin.

2. An assembly as claimed in claim 1, said locating members and said resilient means comprising a generally bow-shaped springy element resiliently self retaining in an axial bore of said pin with ends projecting therefrom to provide locating members.

3. An assembly substantially as described herein with reference to the acompanhing drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pin locating means This invention relates to pin locating means and relates especially, but not exclusively, to means locating a gudgeon pin in a piston of a piston and cylinder machine. In a piston and cylinder machine it is usual for a connecting rod between a crankshaft and a piston to be pivotally connected to the piston by means of a gudgeon pin located in relation to the piston either by internal circlips in the lateral bore of the piston in which the gudgeon is fitted or by metal end pads retained by the cylinder walls in the ends of the lateral bore of the piston. Whereas such circlips require machined internal grooves in the piston end pads are susceptible to undesired end-play and also possible rubbing wear in relation to the cylinder walls. The present invention provides in an assembly of a pivot pin and a receiving bore of a body locating members extending radially away from the axis of the pin and retained at the ends of the pin to restrain the pin against axial movement of the pin relative to the body, said members being conjoined by a reailient member passing through the pin. In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawing which illustrates a sectional view of a piston of an air compressor. Referring to the drawing a cast aluminium piston for a piston and cylinder air compressor is denoted by ref. 1 and carries compression rings 2 and 3 and an oil retaining ring 4. The skirt 5 of the piston is cut away at the sides, namely the areas where there is negligible lateral thrust through the connecting rod 6. The piston has a hollow gudgeon pin 7 via which it is connected to the connecting rod 6, the gudgeon pin 7 being somewhat shorter than the diameter of the piston by virtue of the aforementioned cut-aways. The gudgeon pin 7 is a close sliding fit in the lateral bore 8 of the piston and is located centrally in relation to the piston by locating members 9 and 10 at the ends of a resilient self-retaining generally bow-shaped member 11 which bears against the interior of the axial bore of gudgeon pin 7 in a sense to urge the members 9 and 10 radially outwards in relation to the gudgeon pin. Because the member 9 and 10 are so urged radially outwards and extend beyond the diameter of the gudgeon pin they are effective to locate the latter within pre-determined tolerances centrally in relation to the piston. In order to permit a certain amount of lateral movement of the gudgeon pin in the bore of the piston the length of the gudgeon pin can be chosen to be sufficiently longer as shown in inset (a) than the distance between the extremities of the said bore.Alternatively, the gudgeon pin may be chosen to be appropriately shorter as shown in inset (b) in relation to the distance between the extremities of the bore. Although the members 9 and 10 are shown in the drawing as simply formed of the ends of the resilient bow-shaped member 11, they may be doubled back or otherwise shaped to present more substantial bearing surfaces against the surfaces of the piston and thereby extend the useful life by reducing possible wear. The combined locating members and resilient means is constructible from spring steel wire and a cheap and easily assembled arrangement is provided in accordance with the invention. Furthermore, such a means may be arranged if required to act as a direct substitute for conventional internal circlips by allowing the locating members to engage in the annular grooves instead of the circlips in a conventional piston. CLAIMS

1. An assembly of a pivot pin and a receiving bore of a body having locating members extending radially outwards away from the axis of the pin and retained at the ends of the pin to restrain the pin against axial movement of the pin relative to the body said members being conjoined by a resilient means passing through the pin.

2. An assembly as claimed in claim 1, said locating members and said resilient means comprising a generally bow-shaped springy element resiliently self retaining in an axial bore of said pin with ends projecting therefrom to provide locating members.

3. An assembly substantially as described herein with reference to the acompanhing drawing.