GB2093948A

GB2093948A - Piston/piston rod assembly

Info

Publication number: GB2093948A
Application number: GB8205127A
Authority: GB
Original assignee: O&K Orenstein and Koppel GmbH
Current assignee: CNH Industrial Baumaschinen GmbH
Priority date: 1981-02-26
Filing date: 1982-02-22
Publication date: 1982-09-08
Also published as: DE3107177C2; FR2500561A1; GB2093948B; DE3107177A1; FR2500561B3

Abstract

This invention relates to a piston/piston rod assembly wherein the piston comprises at least one ring portion which is made up of at least two, preferably sector-like, elements (4a, 4b) held together by cylinder wall 1 and mounted on a part (3) of the rod of reduced diameter. <IMAGE>

Description

SPECIFICATION Improvements in or relating to piston assemblies This invention relates to a piston assembly for use in a hydraulic cylinder.

An object of the present invention is to provide a piston assembly in which the piston (for a hydraulic cylinder) is releasably fastened to the piston rod, the fastening being capable of withstanding impacts or shock-like strains even when forces are applied, in use, to both sides of the piston.

The present invention provides a piston assembly comprising a piston and a piston rod, the piston comprising at least one ring which is made up of at least two, preferably sector-like, elements mounted on the rod, each element defining part of the outer periphery of the ring and that part of the rod receiving the or a respective ring having a diameter smaller than that of the remainder of the rod.

Advantages of the assembly according to the invention, are that it provides a secure and releasable fastening of the piston on the piston rod, the piston being fastened without waste of space, being easy to mount and being capable of withstanding shock-like strains without the security of the fastening being adversely affected.

Advantageously, the piston comprises at least two rings, and, preferably, each ring has a predominant function: either sealing or guiding and/or power transmitting.

The present invention also provides a hydraulic cylinder incorporating a piston assembly according to the invention.

Various piston assemblies constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing in which: Figure 1 (a) is a diagrammatic cross-sectional side elevation of a piston/cylinder assembly; Figure 1 (b) is a cross-section on the line of A A of Fig. 1 showing, diagrammatically, how the piston is mounted on the piston rod; Figure 2 is a cross-sectional side elevation of a piston/cylinder assembly used in practice; Figure 3 is a cross-section of part of a piston/cylinder assembly with a modified sealing ring, and Figure 4 is a cross-section of part of a piston/cylinder assembly with a modified guide/power transmission ring.

Referring to the accompanying drawing, Figs.

1 (a) and (b) illustrate, diagrammatically, a hydraulic cylinder 1 in which is mounted a piston rod 2 carrying a piston 4a, 4b. The piston rod 2 has a section 3 having a smaller diameter than the diameter of the remainder of the rod 2. Held together on the piston rod section 3 by the internal wall of the cylinder are two sector-like pieces 4a and 4b which together make up the piston.

Although only two sector-like pieces are illustrated, the piston can be made up of a larger number of, preferably sector-like, pieces.

Figure 2 shows an arrangement used in practice in which the piston is made up of a plurality of rings. Between two guide and power transmission rings 5a and Sb, there is arranged a sealing ring 6. The ring 6 is a complete ring and is arranged on a part 7 of the piston rod which has a greater diameter than the sections 3a and 3b of the piston rod which receive the rings 5a and Sb.

In this way the ring 6 can be passed over the rod 2 (or 2a) and mounted on the part 7.

In particular, the diameter of the part 7 of the piston rod is arranged to be equal to or greater than the diameter of those parts of the piston rod 2, 2a on each side of the piston (if those parts are equal in diameter) or greater than the diameter of one of those parts of the piston rod (if those parts differ in diameter). If, therefore, the diameter of the right-hand part 2a of the piston rod 2 in Figure 2 is smaller than the diameter of the lefthand part of the piston rod 2, then the diameter of the part 7 is arranged to be greater than the diameter of the part 2a.

The rings 5a and Sb are constructed in a similar way to the ring shown in Figure 1. Each comprises two or more, preferably sector-like, elements which are brought together round the reduced diameter sections 3a and 3b of the rod 2 where they are held in place by the internal wall of the cylinder 1.

A circumferential groove 8 is provided in the part 7 of the piston rod. The groove 8 contains sealing material 9 that seals against the inner periphery of the sealing ring 6. The sealing ring 6 also has a circumferential groove 11 in which sealing material 12 is provided to seal against the wall of the hydraulic cylinder 1.

The sealing material 12 provides a seal in both directions of movement of the piston rod.

In the modification shown in Figure 3 the sealing ring element 10 has two circumferential grooves 1 la and 1 1b in which lip seals 12a and 1 2b, respectively, are provided. Each of the seals 1 2a and 1 2b has a sealing effect in a respective one of the two directions of movement of the piston.

The guide and power transmission ring elements 5a, Sb may consist of a low friction material or of a support coated with such material.

In the modification shown in Figure 4, the guide and power transmission ring comprises a support 14, made up of two or more preferably, sector-like, elements, having a circumferential groove 1 5 in which is mounted a band 13 of low friction material. The band 13 is in the form of a complete ring which, when positioned in the groove 15, serves to hold together the elements forming the support 14. To facilitate mounting of the band 13 over the support 14 and into the recess 13, it is preferably formed with a cut or cuts in one of its sides. In this case the band 13 as well as the internal wall of the cylinder holds the support pieces in position on the piston rod.

Claims

1. A piston assembly comprising a piston and a piston rod, the piston comprising at least one ring which is made up of at least two elements mounted on the rod, each element defining part of the outer periphery of the ring and that part of the rod receiving the or a respective ring having a diameter smaller than that of the remainder of the rod.

2. A piston assembly as claimed in claim 1, in which the piston comprises at least two rings.

3. A piston assembly as claimed in claim 2, in which each ring has a predominant function, either sealing or guiding and/dr power transmitting.

4. A piston assembly as claimed in claim 3, in which two guiding and/or power transmitting rings are provided between which at least one sealing ring is arranged.

5. A piston assembly as claimed in claim 4, in which each guiding and/or power transmitting ring is made up of at least two elements and the sealing ring is a complete ring.

6. A piston assembly as claimed in claim 4 or claim 5, in which the diameter of that part of the rod receiving the sealing ring is greater than the diameter of those parts of the rod receiving the guiding and/or power transmitting rings.

7. A piston assembly as claimed in claim 6, in which the diameter of the said part of the rod receiving the sealing ring is greater than or equal to the diameter of that part of the rod which does not receive the piston.

8. A piston assembly as claimed in claim 6, in which the piston rod extends to both sides of the piston, the diameters of these parts of the rod to each side of the piston being different, and in which the diameter of the said part of the rod receiving the sealing ring is greater than or equal to the diameter of one of the parts of the rod lying outside the piston.

9. A piston assembly as claimed in any one of claims 4 to 8, in which that part of the rod receiving the sealing ring is provided with a circumferential groove.

10. A piston assembly as claimed in claim 9, in which a seal is provided in the groove.

11. A piston assembly as claimed in any one of claims 4 to 10, in which the sealing ring has at least one circumferential groove.

12. A piston assembly as claimed in claim 11, in which a seal is provided in the or a respective sealing ring groove.

13. A piston assembly as claimed in claim 12, in which there is only one seal which has a sealing effect in both directions of movement of the rod.

14. A piston assembly as claimed in claim 11 or claim 12, in which the sealing ring has two circumferential grooves, one seal being effective in one direction of movement of the rod and the other seal being effective in the other direction of movement of the rod.

15. A piston assembly as claimed in any one of claims 1 to 14, in which the or each of the rings made up of two or more elements is made of low friction material or its outer periphery is coated with low friction material.

16. A piston assembly as claimed in any one of claims 1 to 14, in which the or each ring made up of two or more elements forms a support for a ring or an annular band of material, the support having a circumferential recess which accommodates the band.

1 7. A piston assembly as claimed in claim 16, in which the ring or the band is made of, or its outer surface is coated with, low friction material.

1 8. A piston assembly as claimed in claim 16 or 17, in which the inner or outer periphery of the ring or the band is cut to facilitate its assembly to the support.

1 9. A piston assembly as claimed in any one of claims 1 to 18, in which each ring element is a sector-like element.

20. A piston assembly as claimed in any one of claims 1 to 19, in which one or more further pistons, each constructed in the same way as the aforesaid piston, are provided on the rod.

21. Piston arrangement on the piston rod of a hydraulic cylinder wherein there is provided at least one piston that consists of several ring element pieces which are joined together about a piston rod section which has a smaller diameter than the adjacent piston rod.

22. A piston assembly substantially as hereinbefore described with reference to, and as illustrated by, Fig. 1 or Fig. 2 or Fig. 3 or Fig. 4.

23. A hydraulic cylinder incorporating a piston assembly as claimed in any one of claims 1 to 22.