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WO1998022735A1 - Piston and cylinder assembly - Google Patents

Piston and cylinder assembly Download PDF

Info

Publication number
WO1998022735A1
WO1998022735A1 PCT/GB1997/003209 GB9703209W WO9822735A1 WO 1998022735 A1 WO1998022735 A1 WO 1998022735A1 GB 9703209 W GB9703209 W GB 9703209W WO 9822735 A1 WO9822735 A1 WO 9822735A1
Authority
WO
WIPO (PCT)
Prior art keywords
seal
piston
cylinder
end wall
shaft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1997/003209
Other languages
French (fr)
Inventor
Barry John Millard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Adwest Steering Ltd
Original Assignee
Adwest Steering Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Adwest Steering Ltd filed Critical Adwest Steering Ltd
Publication of WO1998022735A1 publication Critical patent/WO1998022735A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/32—Sealings between relatively-moving surfaces with elastic sealings, e.g. O-rings
    • F16J15/3268—Mounting of sealing rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/20—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application
    • B62D5/22—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle specially adapted for particular type of steering gear or particular application for rack-and-pinion type

Definitions

  • the present invention relates to a piston and cylinder assembly, in particular but not exclusively, for use in a rack and pinion power assisted steering mechanism.
  • the present invention also relates to a method of installing an internally located fluid seal in such a piston and cylinder assembly.
  • a method of installing a fluid seal in a piston and cylinder assembly the piston having a piston head mounted upon a piston shaft which extends externally of the cylinder through an end wall of the cylinder, the fluid seal after installation residing in a seal housing formed in said end wall to provide a sealing connection between said shaft and end wall, the method including providing the piston with seal engagement means mounting the seal on the shaft, inserting the piston into said cylinder so that piston shaft extends through said end wall, and moving the piston toward said end wall in order that the seal engagement means engage said seal and press said seal into said seal housing.
  • the piston head is provided with said seal engagement means.
  • limit means are provided so as to limit axial travel of the piston in order to stop the seal engagement means engaging the seal.
  • a piston and cylinder assembly comprising a piston having a piston head slidably received in a piston cylinder, the piston head being mounted upon a piston shaft which extends externally of the cylinder through an axial end wall of said cylinder, a fluid seal mounted internally of the cylinder in a seal housing formed in said end wall, the fluid seal providing a sealing connection between said piston shaft and the end wall, the piston being provided with seal engagement means arranged to engage said seal during installation for pressing the seal into said seal housing.
  • seal engagement means are formed on said piston head.
  • a rack and pinion powered assisted steering mechanism including a piston and cylinder assembly as defined above.
  • Figure 1 is an axial cross-sectional view of a piston and cylinder assembly according to an embodiment of the present invention showing the piston and cylinder assembly during normal use;
  • Figure 2 is an axial section of the piston shown in Figure 1 immediately prior to insertion into the cylinder;
  • Figure 3 is a cross-sectional view similar to Figure 1 shown during a seal installation process;
  • Figure 4 is an enlarged part axial section of the assembly shown in Figure 1 showing the seal after installation;
  • Figure 5 is a view similar to Figure 4 showing a modified end wall.
  • a piston and cylinder assembly 10 according to a preferred embodiment of the invention is illustrated in Figures 1 and 2.
  • the assembly 10 includes a cylinder 12 including a cylindrical piston housing 14 having an end wall 16.
  • the end wall 16 of the cylinder 12 is defined by a sleeve member 18 having an internal through bore 19.
  • the sleeve member 18 is partially housed within the housing 14, a seal 20 preferably being provided therebetween in order to provide a fluid seal.
  • the assembly 10 includes a piston 25 comprising a piston shaft 26 on which is mounted a piston head 27.
  • the piston shaft 26 extends through bore 19 and externally of the cylinder 12.
  • the piston shaft 26 When used in a powered assisted steering mechanism, the piston shaft 26 will normally form an extension of a steering rack and will be provided with rack teeth.
  • seal housing 28 The inner axial end of sleeve member 18 is recessed to define a seal housing 28 in which is located a fluid seal 30 (Figure 1 and 4).
  • Fluid seal 30 acts to provide a fluid sealing connection between shaft 26 and the end wall 16.
  • the housing 28 has an end wall 34 against which the seal sealingly abuts in use and a retaining shoulder 29 which acts to retain the seal 30 against axial movement out of the housing 28.
  • seal housing 28 is located internally of the cylinder 12 and access thereto is difficult due to the axial depth of the cylindrical housing 14.
  • the piston 25 is next inserted longitudinally into the housing 14 such that shaft 26 extends through bore 19. Insertion of the piston 25 is continued until the piston head 27 presses the seal 30 into the seal housing 28. This is illustrated in Figure 3 whereat the piston head 27 is identified as being located at position IP. The piston 25 is next withdrawn away from the end wall 16 leaving the seal 30 housed within seal housing 28.
  • the piston 25 is preferably constrained to reciprocate between limit positions LR and LL; position LL being spaced from position IP so that during normal use the piston head 27 does not contact the seal 30.
  • the seal 30 is a pressure seal of generally U-shaped cross-section such that increases in fluid pressure tend to increase the sealing effect of the seal.
  • the piston head 27 is provided with a seal abutment portion 40 which is generally in the form of an annular axially extending flange and which is locatable within the annular groove 30c formed in the U- shaped seal.
  • seal abutment portion 40 may be a separate component mounted on the shaft 26 and spaced from the piston head 27.
  • the fluid seal 30 may be any conventional fluid seal and is not necessarily of U-shaped cross- section.
  • the seal 30 has an outer annular limb 30a having an outer seal surface 30b which sealingly engages the circumferential wall 28a of the seal housing 28. It will be appreciated that increases in fluid pressure will tend to urge limb 30a radially outwardly and thereby enhance the sealing engagement between surface
  • outer limb 30a may be deflected relatively easily radially inwardly during the installation process so as to ride over the retaining shoulder 29 without damage and also without causing undesirable twisting of the seal. After clearing shoulder 29, the resilience of the seal 30 causes limb 30a to move radially outwardly into contact with wall 28a.
  • limb 30a has an inclined surface 30d for facilitating entry of the seal into chamber 28.
  • the sleeve 18 is provided with a chamfered wall 28d which acts to facilitate radial inward deflection of the seal 30 during installation.
  • the wall 28a of chamber 28 is cylindrical.
  • a modification is shown in Figure 5 wherein the wall 28a is contoured to the same shape and size as the outer surface of the seal 30.
  • This arrangement has the advantage of providing support to the seal during use.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Sealing With Elastic Sealing Lips (AREA)

Abstract

A method of installing a fluid seal (30) in a piston and cylinder assembly (10), the piston (25) having a piston head (27) mounted upon a piston shaft (26) which extends externally of the cylinder (12) through an end wall (16) of the cylinder (12), the fluid seal (30) after installation residing in a seal housing (28) formed in said end wall (16) to provide a sealing connection between said shaft (26) and end wall (16), the method including providing the piston (25) with seal engagement means (40) mounting the seal (30) on the shaft (26), inserting the piston (25) into said cylinder (12) so that the piston shaft (26) extends through said end wall (16), and moving the piston (25) toward said end wall (16) in order that the seal engagement means (40) engage said seal (30) and press said seal (30) into said seal housing (28).

Description

PISTON AND CYLINDER ASSEMBLY
The present invention relates to a piston and cylinder assembly, in particular but not exclusively, for use in a rack and pinion power assisted steering mechanism.
The present invention also relates to a method of installing an internally located fluid seal in such a piston and cylinder assembly.
According to one aspect of the present invention there is provided a method of installing a fluid seal in a piston and cylinder assembly, the piston having a piston head mounted upon a piston shaft which extends externally of the cylinder through an end wall of the cylinder, the fluid seal after installation residing in a seal housing formed in said end wall to provide a sealing connection between said shaft and end wall, the method including providing the piston with seal engagement means mounting the seal on the shaft, inserting the piston into said cylinder so that piston shaft extends through said end wall, and moving the piston toward said end wall in order that the seal engagement means engage said seal and press said seal into said seal housing.
Preferably the piston head is provided with said seal engagement means. Preferably after installation of the seal into said seal housing, limit means are provided so as to limit axial travel of the piston in order to stop the seal engagement means engaging the seal.
According to another aspect of the present invention there is provided a piston and cylinder assembly comprising a piston having a piston head slidably received in a piston cylinder, the piston head being mounted upon a piston shaft which extends externally of the cylinder through an axial end wall of said cylinder, a fluid seal mounted internally of the cylinder in a seal housing formed in said end wall, the fluid seal providing a sealing connection between said piston shaft and the end wall, the piston being provided with seal engagement means arranged to engage said seal during installation for pressing the seal into said seal housing.
Preferably the seal engagement means are formed on said piston head.
According to another aspect of the invention there is provided a rack and pinion powered assisted steering mechanism including a piston and cylinder assembly as defined above.
Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which :-
Figure 1 is an axial cross-sectional view of a piston and cylinder assembly according to an embodiment of the present invention showing the piston and cylinder assembly during normal use;
Figure 2 is an axial section of the piston shown in Figure 1 immediately prior to insertion into the cylinder;
Figure 3 is a cross-sectional view similar to Figure 1 shown during a seal installation process; Figure 4 is an enlarged part axial section of the assembly shown in Figure 1 showing the seal after installation;
Figure 5 is a view similar to Figure 4 showing a modified end wall. A piston and cylinder assembly 10 according to a preferred embodiment of the invention is illustrated in Figures 1 and 2.
The assembly 10 includes a cylinder 12 including a cylindrical piston housing 14 having an end wall 16. The end wall 16 of the cylinder 12 is defined by a sleeve member 18 having an internal through bore 19. The sleeve member 18 is partially housed within the housing 14, a seal 20 preferably being provided therebetween in order to provide a fluid seal.
The assembly 10 includes a piston 25 comprising a piston shaft 26 on which is mounted a piston head 27. The piston shaft 26 extends through bore 19 and externally of the cylinder 12.
When used in a powered assisted steering mechanism, the piston shaft 26 will normally form an extension of a steering rack and will be provided with rack teeth.
The inner axial end of sleeve member 18 is recessed to define a seal housing 28 in which is located a fluid seal 30 (Figure 1 and 4). Fluid seal 30 acts to provide a fluid sealing connection between shaft 26 and the end wall 16. The housing 28 has an end wall 34 against which the seal sealingly abuts in use and a retaining shoulder 29 which acts to retain the seal 30 against axial movement out of the housing 28. As seen in Figure 1 , seal housing 28 is located internally of the cylinder 12 and access thereto is difficult due to the axial depth of the cylindrical housing 14.
Installation of the fluid seal 30 into the seal housing 28 is achieved by initially sliding seal 30 onto shaft 26 and preferably moving the seal 30 so as to abut the piston head 27. This is illustrated in Figure
2.
The piston 25 is next inserted longitudinally into the housing 14 such that shaft 26 extends through bore 19. Insertion of the piston 25 is continued until the piston head 27 presses the seal 30 into the seal housing 28. This is illustrated in Figure 3 whereat the piston head 27 is identified as being located at position IP. The piston 25 is next withdrawn away from the end wall 16 leaving the seal 30 housed within seal housing 28.
In use, the piston 25 is preferably constrained to reciprocate between limit positions LR and LL; position LL being spaced from position IP so that during normal use the piston head 27 does not contact the seal 30.
Preferably, the seal 30 is a pressure seal of generally U-shaped cross-section such that increases in fluid pressure tend to increase the sealing effect of the seal.
Preferably in order to facilitate insertion of the seal 30 into the seal housing, the piston head 27 is provided with a seal abutment portion 40 which is generally in the form of an annular axially extending flange and which is locatable within the annular groove 30c formed in the U- shaped seal. It is to be appreciated that the seal abutment portion 40 may be a separate component mounted on the shaft 26 and spaced from the piston head 27. It is also to be appreciated that the fluid seal 30 may be any conventional fluid seal and is not necessarily of U-shaped cross- section.
As more clearly seen in Figure 4, the seal 30 has an outer annular limb 30a having an outer seal surface 30b which sealingly engages the circumferential wall 28a of the seal housing 28. It will be appreciated that increases in fluid pressure will tend to urge limb 30a radially outwardly and thereby enhance the sealing engagement between surface
30b and wall 28a. In addition, due to the annular gap 30c between the inner and outer limbs of the seal 30, outer limb 30a may be deflected relatively easily radially inwardly during the installation process so as to ride over the retaining shoulder 29 without damage and also without causing undesirable twisting of the seal. After clearing shoulder 29, the resilience of the seal 30 causes limb 30a to move radially outwardly into contact with wall 28a. Preferably limb 30a has an inclined surface 30d for facilitating entry of the seal into chamber 28.
Preferably the sleeve 18 is provided with a chamfered wall 28d which acts to facilitate radial inward deflection of the seal 30 during installation.
As seen in Figure 4, the wall 28a of chamber 28 is cylindrical. A modification is shown in Figure 5 wherein the wall 28a is contoured to the same shape and size as the outer surface of the seal 30.
Accordingly, the outer surface of the seal 30 is in contact with the wall
28a along its entire axial extent. This arrangement has the advantage of providing support to the seal during use.

Claims

1. A method of installing a fluid seal in a piston and cylinder assembly, the piston having a piston head mounted upon a piston shaft which extends externally of the cylinder through an end wall of the cylinder, the fluid seal after installation residing in a seal housing formed in said end wall to provide a sealing connection between said shaft and end wall, the method including providing the piston with seal engagement means mounting the seal on the shaft, inserting the piston into said cylinder so that piston shaft extends through said end wall, and moving the piston toward said end wall in order that the seal engagement means engage said seal and press said seal into said seal housing.
2. A method according to Claim 1 wherein the piston head is provided with said seal engagement means.
3. A method according to Claim 1 or 2 wherein after installation of the seal into said seal housing, limit means are provided so as to limit axial travel of the piston in order to stop the seal engagement means engaging the seal.
4. A piston and cylinder assembly comprising a piston having a piston head slidably received in a piston cylinder, the piston head being mounted upon a piston shaft which extends externally of the cylinder through an axial end wall of said cylinder, a fluid seal mounted internally of the cylinder in a seal housing formed in said end wall, the fluid seal providing a sealing connection between said piston shaft and the end wall, the piston being provided with seal engagement means arranged to engage said seal during installation for pressing the seal into said seal housing.
5. An assembly according to Claim 4 wherein the seal engagement means are formed on the piston head.
6. An assembly according to Claim 5 wherein the seal has a U- shaped cross-section which defines an annular groove which in use faces said piston head, the seal engagement means being in the form of an annular axially extending flange which is locatable within said annular groove.
7. An assembly according to any of Claims 4 to 6 wherein said seal housing includes a retaining shoulder for retaining the seal within the housing after installation.
8. A rack and pinion powered assisted steering mechanism including a piston and cylinder assembly as defined above.
PCT/GB1997/003209 1996-11-22 1997-11-21 Piston and cylinder assembly Ceased WO1998022735A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9624353.0 1996-11-22
GBGB9624353.0A GB9624353D0 (en) 1996-11-22 1996-11-22 Piston and cylinder assembly

Publications (1)

Publication Number Publication Date
WO1998022735A1 true WO1998022735A1 (en) 1998-05-28

Family

ID=10803356

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1997/003209 Ceased WO1998022735A1 (en) 1996-11-22 1997-11-21 Piston and cylinder assembly

Country Status (2)

Country Link
GB (1) GB9624353D0 (en)
WO (1) WO1998022735A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1008657A (en) * 1962-05-18 1965-11-03 Walker & Co James Ltd Improvements in and relating to scraper rings for hydraulic rams
JPS59102658A (en) * 1982-12-06 1984-06-13 Atsugi Motor Parts Co Ltd Manufacturing method for rack and pinion power steering device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1008657A (en) * 1962-05-18 1965-11-03 Walker & Co James Ltd Improvements in and relating to scraper rings for hydraulic rams
JPS59102658A (en) * 1982-12-06 1984-06-13 Atsugi Motor Parts Co Ltd Manufacturing method for rack and pinion power steering device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 8, no. 220 (M - 330) 6 October 1984 (1984-10-06) *

Also Published As

Publication number Publication date
GB9624353D0 (en) 1997-01-08

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