GB1602039A

GB1602039A - Pistons for reciprocating machines

Info

Publication number: GB1602039A
Application number: GB24354/78A
Authority: GB
Original assignee: Alcan Aluminiumwerk Nuernberg GmbH; Alcan Aluminiumwerke GmbH
Current assignee: Alcan Aluminiumwerk Nuernberg GmbH; Novelis Deutschland GmbH
Priority date: 1977-12-14
Filing date: 1978-05-30
Publication date: 1981-11-04
Also published as: ES475949A1; AT372763B; ATA826178A; IT1100722B; FR2412011B1; FR2412011A1; EP0002520B1; DE2755739C3; IT7830841A0; DE2755739B2; EP0002520A1; DE2755739A1; DE2860706D1

Description

PATENT SPECIFICATION

( 11) 1 602 039 Application No 24354/78 ( 22) Filed 30 May 1978 Convention Application No 2755739 ( 19) Filed 14 Dec 1977 in Federal Republic of Germany (DE)

Complete Specification published 4 Nov 1981 I

INT CL 3 F 16 J 1/02 Index at acceptance F 2 T 37 A 2 ( 54) IMPROVEMENTS RELATING TO PISTONS FOR RECIPROCATING MACHINES ( 71) We, ALCAN ALUMINIUMWERK NURNBERG GMBH, a German Company of 6000 Frankfurt/Main, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to a piston for reciprocating piston machines.

Since, particularly in internal combustion engines and compressors, the piston, despite differing thermal expansion of the materials of the cylinder and piston, must run efficiently at all operating temperatures without chatter or seizing, measures employed to achieve this situation include the incorporation in the main part of the piston skirt of annular or sleeve-like elements made of a material having a coefficient of thermal expansion differing from that of the basic material of the piston; the purpose of this being to utilize the resultant bi-metal action for ensuring that the outer face of the piston remains in contact with the cylinder wall This measure also reduces the kinetic energy, which accumulates as a result of the piston bearing during its path of travel first at one side of the cylinder wall and then at the other side and which, when the piston impinges against the cylinder, promotes vibrations in the cylinder which cause considerable noise.

Noise-inhibiting effects are also achieved by providing narrow channels or gaps in the outer face of the piston skirt; these channels or gaps absorb oil during operation by their capillary action, so that when the piston encounters the cylinder wall, this oil, acting like a shock-absorber, reduces noise.

However, the oil has a relatively low viscosity, which does not suffice, in all operating conditions, to keep the outer face of the piston spaced from the cylinder wall and therefore to prevent the transfer of energy and vibrations between these two components.

Apart from suffering from the abovementioned disadvantages, the two solutions outlined above also present problems as regards manufacture Complicated moulds are required for producing pistons with inserts cast into them.

In contrast, the object of the present invention is to provide a very smoothrunning piston which is of simple construction and easy to produce.

According to the invention this object is achieved by a piston wherein a metallic skirt of the piston is provided with at least one annular or arcuate metallic, noise-inhibiting element which is bonded to the outer face of the skirt by means of a viscoelastic adhesive, the adhesive providing the sole connection between the metallic noise-inhibiting element and the metallic skirt and isolating the skirt and the element from metallic contact therebetween.

The piston according to this invention is very smooth-running since the viscoelastic adhesive, on the one hand, provides support for the element which has a certain degree of elasticity so that when the piston strikes the cylinder wall, the kinetic energy and therefore the noise-inducing vibrations that occur are reduced, while on the other hand, the layer of adhesive itself forms a noiseinhibiting covering Since the element can be connected to the main part of the skirt by means of a simple bonding operation, the piston of the invention can be produced in a simple and inexpensive manner.

With the element is fitted on the outer face of the skirt, the skirt is effectively spring-supported on the cylinder wall in a particularly effective manner, so that the piston runs extremely smoothly.

It may be advantageous if the element extendsover the entire length of the skirt.

This is advantageous both as regards noisereduction and production procedure.

In accordance with a further feature and for the purpose of providing the piston with suitable load-bearing properties, the outer 0 m me ( 21) ( 31) ( 32) ( 33) ( 44) ( 51) ( 52) 2 1,602,039 2 wall of the element departs from a true cylindrical shape.

As an alternative to the above-mentioned form, it may also be expedient for the axial length of the element to be less than that of the skirt, and for the element to be fitted in a complementary channel in the skirt In this arrangement a plurality of elements can be provided on the outer face of the skirt.

Particular load-bearing properties can also be imparted to the piston in this way.

The element and the skirt may have the same or different wall thickness in the zone where the element is fitted However the wall thickness of the element is preferably smaller than that of the skirt.

The element and the skirt may be made of materials having the same coefficient of thermal expansion, and the piston and element are preferably made of aluminium or an aluminium alloy.

Two specific embodiments of the improved piston of this invention will now be described by reference to the accompanying drawings, in which:Figure 1 is a longitudinal axial section of a first embodiment wherein the element is fitted on the outer face of the piston skirt and extends over the entire length of the skirt, arid Figure 2 is a longitudinal axial section of a second embodiment wherein a plurality of elements are fitted on the outer face of the piston skirt.

In the embodiment illustrated in Figure 1 a piston, designated generally by the numeral 1, has bonded to the outer surface of the main part of the skirt 2 by means of a layer 3 of a viscous and elastic adhesive an element 4 which forms an additional wall part As initially explained, this arrangement results in a piston having extremely good noise-inhibiting properties.

A piston of the illustrated kind has given very good service in a compressor For a cylinder diameter of 88 mm, the bonded element 4 has a wall thickness of 1 4 mm, the wall thickness of the main part of the skirt 2 being approximately 2 5 mm The piston-and the element 4 are both made of aluminium The thickness of the viscoelastic layer 3 of adhesive is about 10 microns The viscous elastic adhesive used may be a high grade ageing-resisting synthetic resin dispersion adhesive based on acrylate, which is able to resist, without difficulty, the service temperatures occurring in the piston The piston used is so constructed that the gudgeon pin is considerably shorter than the diameter of the piston, and the means necessary for securing the pin are disposed in channels which are formed in the pin bore in the main body of the piston at a distance of approximately 10 mm from the outer wall.

Apart from having been found to inhibit noise to a considerable extent, the abovedescribed piston has the additional advantage that previously occurring very considerable damage due to seizing and scoring of the piston when lubrication is defective is avoided since, in the event of great frictional resistance, the element 4 is scored and finally torn off before the piston itself or the cylinder suffer any damage.

In the embodiment illustrated in Figure 2, two elements 4 a and 4 b are provided in the outer face 2 a of the piston skirt Each of these elements 4 a and 4 b is fitted in a complementary channel 2 b and 2 c respectively formed in the outer face 2 a of the skirt and they are bonded therein by means of a layer 3 a and 3 b, respectively of a viscoelastic adhesive.

Claims

WHAT WE CLAIM IS:-

1 A piston for reciprocating piston machines wherein a metallic skirt of the piston is provided with at least one annular or arcuate metallic, noise-inhibiting element which is bonded to the outer face of the skirt by means of a viscoelastic adhesive, the adhesive providing the sole connection between the metallic noise-inhibiting element and the metallic skirt and isolating the skirt and the element from metallic contact therebetween.

2 A piston as claimed in claim I, wherein the element extends over the entire length.

of the skirt.

3 A piston as claimed in claim 2, wherein the outer wall of the element deviates from the true cylindrical shape.

4 A piston as claimed in claim I, wherein the axial length of element is smaller than that of the skirt and the element is arranged in a complementary channel in the skirt.

A piston as claimed in claim 4, wherein a plurality of elements are provided on the outer face of the skirt.

6 A piston as claimed in any preceding claim wherein the or each element and the skirt have different wall thicknesses in the zone where the or each element is arranged.

7 A piston as claimed in any preceding claim, wherein the or each element and the skirt consist of materials with the same thermal expansion coefficient.

8 A piston as claimed in any preceding claim, wherein the piston and the element 1,602,039 1,602,039 or elements, are made of aluminium or an STEVENS, HEWLETT & PERKINS, aluminium alloy Chartered Patent Agents, 9 A piston constructed and arranged 5, Quality Court, substantially as herein-before described Chancery Lane, with reference to Figure 1 or Figure 2 of the London, WC 2.

accompanying drawings.

Printed for Her Maiesty's Stationery Office, by the Courier Press, Leamington Spa, 1981 Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A IAY, from which copies may be obtained.