GB2035438A

GB2035438A - Piston pin securing means

Info

Publication number: GB2035438A
Application number: GB7934480A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1978-10-14
Filing date: 1979-10-04
Publication date: 1980-06-18
Also published as: DE2844839C2; DE2844839A1; FR2438782A1; GB2035438B; FR2438782B3

Abstract

A securing spring is described which enables a piston pin to be secured in a piston in a comparatively easy manner but is less susceptible to breakage, in use, than securing means previously-employed for this purpose. The spring is generally U-shaped with an enlarged head, the arms being stressed to spring apart and being bent outwardly at the ends. The spring is used to secure a piston pin which is in the form of a hollow cylinder and is inserted into the bore of the pin by pressing together the spring arms. When the securing spring is in position, the outwardly- bent ends and the head extend from the piston pin bore and cooperate with the piston to secure the piston pin against axial displacement. The spring arms may be crossed at least once. <IMAGE>

Description

SPECIFICATION Piston pin securing means The invention relates to securing means for securing a piston pin in an engine piston.

The securing of piston pins against displacement in an axial direction has previously been achieved by means of wire snap rings or Seeger rings inserted in grooves in the piston pin bores of pistons. However, it can happen that these securing rings snap when not properly assembled and pieces thereof get between the piston and the cylinder wall, resulting in damage to the running faces of the piston. Moreover, this type of securing means necessitates the cutting of circumferential grooves in piston pin bores which means a machining step involving time and money. In addition, there is the amount of time spent on the assembly operation and the cost of the assembly apparatus required.

The present invention is directed towards the problems of providing a piston pin securing means which can be manufactured at reasonable cost, and which can be assembled more reliably and simply than the arrangements mentioned while being less susceptible to breakages.

The present invention provides piston pin securing means for securing a piston pin in the form of a hollow cylinder against axial displacement in a piston, the securing means being a generally U-shaped spring the arms of which are stressed to spring apart and are bent outwardly at the ends, the ends of the arms being so shaped that, when pressed together they can be passed through the piston pin bore, and the head of the spring being so shaped that it will not pass through the said bore. The spring arms may be crossed at least once.

In a piston having a piston pin secured by means in accordance with the invention, the head and outwardly-bent ends of the spring may co-operate with shoulders formed in a bore in the piston, in which the piston pin is located.

There may be at least one groove in the piston cooperating with the spring to prevent twisting movement of the spring.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a section of a piston with a piston pin and a piston pin securing spring, each arm of the spring illustrating a different embodiment of the invention; Figure 2 shows a securing spring with crossed arms; Figure 3 shows another form of securing spring with crossed arms, and Figure 4 shows a securing spring with arms crossed several times.

Fig. 1 shows a section of a piston 1 with a piston pin 2 secured by a spring 3. The spring 3 is generally U-shaped, having arms which are stressed to spring apart and which are shown in the Figure as having differentlyshaped ends 4,5 for the purpose of illustrating two embodiments of the invention: it will be understood that, in practice, the arms would be similarly-shaped.

The spring 3 is located in a bore in the piston pin 2 with the head 6 of the spring extending from one end of the bore and the ends 4 and 5 of the arms extending from the other: the length of the arms between the head and the outwardly-bent ends corresponds substantially to the length of the piston pin bore. The head 6 of the spring is enlarged so that it has a diameter greater than the distance between the spring arms and secures the spring against axial displacement in one direction in the piston pin bore while the ends 4 and 5 of the spring arms are bent outwardly and secure the spring against axial displacement in one direction. To this end, both ends of the piston bore 7 in which the piston pin 2 is located are enlarged so that shoulders 9 are formed which are engaged by the head 6 and the ends 4,5 of the spring 3 to secure the spring in position.The ends of the piston bore 7 may be enlarged by drilling or, more simply, the bore may be appropriately shaped during the initial casting process.

To insert the securing spring 3 in the piston pin 2 it is necessary only to press the arms of the spring together to an extent sufficient to enable them to be passed through the piston pin bore: the ends 4,5 of the spring must, of course, be suitably-shaped to enable this operation to be carried out. When released, the arms spring apart and assume the position shown in the drawing to secure the piston pin 2 in the piston bore 7.

Figs. 2 and 3 show securing springs with crossed arms, producing a stiffer spring from the same wire thickness. The embodiments differ from each other in the shape of the head of the spring and of the outwardly-bent ends of the arms and it will be understood that these shapings and those of Fig. 1 are interchangeable.

Fig. 4 shows a securing spring in which the arms are crossed several times to produce an even stiffer spring. This Figure also shows other possible shapings for the head and ends of the spring and it will be understood that these are also interchangeable with those of Figs. 1 to 3.

Finally, Fig. 4 illustrates the provision of axial grooves 11 in the piston bore 7 which accomodate the head and ends of the securing spring and prevent the latter from twisting. Similarly grooves could be employed with the securing springs of Figs. 1 to 3.

The securing springs described above are comparatively simple to produce and to use.

The insertion of a securing spring entails only the pressing together of the arms of the spring against the outwardly directed tension.

The risk of a spring breaking is considerably reduced, compared with the previously-employed snap rings, owing to the resilience provided by the longer length, any vibrations occasioned by the length being compensated for by the resilience.

Claims

1. Piston pin securing means for securing a piston pin in the form of a hollow cylinder against axial displacement in a piston, the securing means being a generally U-shaped spring the arms of which are stressed to spring apart and are bent outwardly at the ends, the ends of the arms being so shaped that, when pressed together they can be passed through the piston pin bore, and the head of the spring being so shaped that it will not pass through the said bore.

2. Piston pin securing means according to claim 1, in which the spring arms are crossed at least once.

3. Piston pin securing means according to claim 1 or claim 2, in which the length of the spring arms between the head and the outwardly-bent ends corresponds substantially to the length of the piston pin.

4. Piston pin securing means according to any one of the preceding claims, in which the diameter of the head of the spring is greater than the distance between the spring arms.

5. A piston having a piston pin in the form of a hollow cylinder secured therein by means according to any one of the preceding claims, the spring arms being located in the piston pin bore and the head and outwardlybent ends of the spring extending from the bore to secure the pin against axial displacement.

6. A piston according to claim 5, in which the head and outwardly-bent ends of the spring co-operate with shoulders formed in a bore in the piston, in which the piston pin is located.

7. A piston according to claim 5 or claim 6, in which at least one groove in the piston co-operates with the spring to prevent twisting movement of the spring.

8. Piston pin securing means substantially as described herein with reference to, and as shown in, any one of the Figures of the accompanying drawings.