GB2091822A

GB2091822A - Seal for a bleed nipple

Info

Publication number: GB2091822A
Application number: GB8136033A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-11-28
Filing date: 1981-11-30
Publication date: 1982-08-04
Also published as: GB2091822B

Abstract

A seal for a bleed nipple comprises a resilient sealing member adapted to surround a bleed nipple (10) between a nut like annulus (15) provided for actuation of the nipple (10) and the slave cylinder (11), the sealing member being adapted to seat around the main part (12) with its outer surface providing a first sealing surface against the rim (22) of the nut like annulus (15), the opposite end of the sealing member forming a second sealing surface for engaging the surface 21 of the body of the slave cylinder (11) and an additional sealing surface provided by an "O"-ring 8 is provided within the sealing member to form a third sealing surface between the body (12) of the bleed nipple (10) and the slave cylinder (11) where the two are connected, the resilience of the sealing member being such as to retain the three sealing surfaces against the said parts of the bleed nipple (10) and slave cylinder (11) during limited axial movement of the bleed nipple (10). As an alternative to the "O"-ring 8 a sealing portion may be integrally formed with the resilient sealing member. <IMAGE>

Description

SPECIFICATION Seal for a bleed nipple This invention relates to a seal for bleed nipple, for brakes, clutches and the like.

In the brake bleeding art, particularly in the use of one man brake bleeding systems, in which, due to a valve provided in the bleeding arrangement, it is not necessary for the brake system to be maintained under pressure while the bleed nipple is being done up, some difficulty has been experienced due to bleed back of air between the screw threads of the brake nipple itself and the wheel cylinder. This can occur as a result either of the nipple used having a screw thread which, as the result of manufacturing tolerances, is not as tight as is necessary to provide a complete seal and also due to the possibility of the operator undoing the bleed nipple too far so that insufficient threads remain in contact to provide the necessary seal.

In my prior patent No. 1568880,1 have described and claimed a brake bleed nipple seal which comprises a resilient bell shaped sealing member adapted to surround the bleed nipple between a nut-like annulus provided for actuation of the nipple and the brake cylinder, the narrow end of the bell being apertured and adapted to seat around the main part of the bleed nipple with its outer surface providing a first sealing surface against the rim of the nut-like annulus of the bleed nipple, the wide end of the bell forming a second sealing surface for engaging the body of the brake cylinder, the resilience of the sealing member being such as to retain the two sealing surfaces against the said parts of the bleed nipple and brake cylinder during limited axial movement of the bleed nipple.

While the above seal has been found in practice to be very effective in normal use, due to certain developments in brake bleeding techniques, it has been found that, with some brake bleeding systems, the pressure required to carry out adequate bleeding has sometimes caused brake fluid to lead around the screw threads of the bleed nipple and still have sufficient pressure to slightly overcome the seal provided, causing a small amount of leakage of brake fluid around the edges of the bleed nipple seal.

It should be emphasised at this point, that at no time is there any back leakage of air into the brake system, since the reduction of the pressure on the brake foot-pedal after a bleeding stroke produces no greater suction a normal and therefore there is no danger whatsoever of any malfunction of the brakes.

However, the leakage of brake fluid is undesirable since it has undesirable effects on certain parts of the vehicle if sufficient leakage occurs that the fluid can reach these parts, for example the tyres of the vehicle.

The present invention therefore seeks to provide an arrangement for sealing the brake nipple even during the use of high pressure brake bleeding.

According to the invention, there is provided a seal for a brake bleed nipple comprising a resilient sealing member adapted to surround a bleed nipple between a nut like annulus provided for actuation of the nipple and the slave cylinder, wherein the sealing member is adapted to seat around the body of the bleed nipple with its outer surface providing a first sealing surface against the rim of the nut like annulus of the bleed nipple, the opposite end of the sealing member forms a second sealing surface for engaging the body of the slave cylinder and an additional sealing surface is provided within the sealing member to provide a third sealing surface acting between the body of the bleed nipple and the slave cylinder at the point where the two are connected, the resilience of the sealing member being such as to retain the three sealing surfaces against the said parts of the bleed nipple and the slave cylinder during limited axial movement of the bleed nipple.

Preferably the sealing member is generally bell shaped with an aperture at its narrow end for seating around the main part of the bleed nipple, the second sealing surface being provided by the wide end of the bell.

The third sealing surface may be provided by a simple "O"-ring seal located within the bell or may be provided by a sealing surface moulded integrally with the bell.

With this type of seal, it should be so dimensioned that when the bleed nipple is unscrewed to the maximum extent likely under a brake bleeding operation, for example, three turns of the bleed nipple, then the whole of the sealing arrangement remains under compression.

The seal may be provided with a cap member adapted to seat over the outer end of the bleed nipple and attached to the sealing member by a strap. Suitably the main body of the cap member, the strap and the sealing member may be produced from a single piece plastics moulding. The cap member may if desired be a two part construction one part of which comprises a transparent base portion, the parts being separable for insertion of an indication, for example the order of bleeding of the slave cylinders, between the parts so as to be visible through the transparent portion.

The invention will now be described in greater detail by way of example with reference to the drawings, in which: Figure 1 is a perspective exploded view of a sealing arrangement in accordance with the invention; Figure 2 is a sectional view through a bleed nipple and its associated cylinder showing the position of the sealing arrangement of Figure 1 when the bleed nipple is fully screwed home, Figure 3 is a view similar to Figure 2 showing the bleed nipple unscrewed ready for a bleeding operation with the cap portion of the sealing arrangement removed from the end of the bleed nipple, and Figure 4 is a view similar to Figure 3 showing the position of an integral additional sealing member.

Referring first of all to Figure 1, the sealing arrangement comprises a bell shaped sealing member 1 having a first sealing surface 2 at its narrow end at the top of the bell and a second sealing surface 3 at the lower or wider end of the bell. The centre of the narrow end of the bell has an aperture 4 forfitting around the bleed nipple as will be described. A suitably dimensioned "O"-ring seal 8 is located within the bell shaped sealing member 1.

Attached to the bell shaped sealing member 1 is a strap 5 which is connected at its outer end to a cap 6 intended for use as a dust cap for covering the end of the bleed nipple to which the tube of the brake bleeding equipment is to be attached. The cap 6 may be provided in one piece or may have a detachable top or base portion 7 which is of transparent material and beneath which can be inserted an indication as desired, for example, an indication of the order in which the various brake cylinders should be bled.

The parts of the sealing arrangement are suitably produced from a synthetic rubber such as neoprene or a flexible plastics material.

Referring now to Figure 2, there is shown the way in which the sealing arrangement is provided on the brake bleed nipple itself. In this Figure the bleed nipple is given the reference numeral 10 and the brake (or slave) cylinder is given the reference numeral 11.

As shown in Figure 2, the arrangement of the nipple and the cylinder is of standard form. The nipple comprises a main screw threaded body 12 which terminates at one end in a conical seating arrangement 13 and at the other end in a straight portion 14 bounded by an annular projection 15 with which is hexagonal for actuation by a spanner. The bleed nipple 10 extends in an outward direction and ends in a further annular projection 16 which seats and stretches a flexible tube of brake bleeding equipment (not shown). The nipple has a central bore 17 which extends through most of its length and is connected to a radial bore 18 which provides for access of brake fluid when the conical seating portion 13 is parted from its seat, here indicated at 19. As can be seen the threaded portion 12 screws into a threaded part 20 of the cylinder.

The sealing arrangement of this invention is situated between the hexagonal annular projection 15 and the outer face 21 of the brake cylinder.

In order to position the sealing arrangement on the bleed nipple, the separated bleed nipple is used (i.e. removed from the brake cylinder or prior to its insertion in the brake cylinder) and the bell shaped sealing member 1 is first placed thereon. To achieve this, the bleed nipple is pushed by its end with the conical sealing arrangement 13 through the aperture 4 of the bell shaped sealing member 1 until the sealing member is located with its sealing surface 2 against the axially directed surface or rim 22 of the hexagonal annulus 15. The aperture 4 will normally be increased in size to allow it to pass the threads of the portion 12. The cap 6 may then be pressed onto the nipple in the position shown in Figure 2 so that it is retained by the projection 16.The "O"-ring 8 is then pushed onto the bleed nipple from the same end as the sealing member 1 and pushed up until it seats within the bell shaped sealing member 1. Once the "O"-ring is in place the nipple 10 is screwed into the wheel cylinder until it takes up the position shown in Figure 2. In this position itwill be seen that the "O"-ring seal 8 is compressed out of its own shape and seats closely around the bleed nipple so as to provide a seal at the connection of the bleed nipple 10 and the outer surface of the wheel cylinder 11. It is to be noted that, in certain circumstances, screwing in of the bleed nipple may be better achieved by leaving the cap 6 off until screwing in has taken place to provide a greater angle of purchase on the hexagonal portion 15 of the nipple.

As can be seen from Figure 2, once the bleed nipple is screwed in, the three sealing surfaces are fully operative, the area around the aperture 4 providing a seal with the hexagonal portion 15 of the bleed nipple the "O"-ring 8 providing a seal between the bleed nipple 10 and the surface 21 of the wheel cylinder 11 as above stated, and the surface 3 providing a seal between the sealing member 1 and the outer surface 21 of the wheel cylinder 11 adjacent to the "0-ring 8.

When it is required to carry out a bleeding operation the cap 6 is first removed from the end of the bleed nipple 10 and the necessary tube for the brake bleeding equipment (not shown) is inserted over the end of the nipple in place of the cap 6. Then the bleed nipple 10 is undone using a spanner on the hexagonal projection portion 15 until the seat part 13 of the bleed nipple 10 is raised from the seat 19 of the wheel cylinder 11. This will normally take place after about half a turn. However, as shown in Figure 3, it is possible for the bleed nipple 10 to be undone considerably more than is necessary, for example three turns, with the sealing member 1 and the "O"-ring seal 8 still under compression so as to continue to provide the necessary seal.Furthermore this ability to unscrew the nipple 10 to a large extent enables the passage from the brake cylinder 11 to be increased thus assisting in the removal of awkward air bubbles or foreign material.

Once the bleeding operation has been completed, the nipple 10 is again screwed back into the cylinder 11, further compressing the sealing member 1 and the "O"-ring 8. The cap 6 is replaced after removal of the brake bleeding tube.

As far as materials go, the whole of the sealing arrangement can be constructed of a suitable plastics material such as polypropylene or polyethylene.

However, advantages accrue in relation to the eventual life of the device if the "O"-ring is made of rubber or rubber like material while the remainder of the arrangement is constructed of plastics as aforesaid.

Instead of the provision of a separate "O"-ring seal within the seal member 1, it is possible, as Figure 4 shows, to provide an integrally moulded portion 25 on the sealing member 1 itself. The Figure shows one such integral moulding, but it will be appreciated that various suitale shapes may be used.

It is to be understood that various modifications may be made to the above described embodiment without departing from the scope of the invention.

For example, it is not necessary for sealing purposes that the cap 6 and its associated strap 5 be provided. Thus the bell shaped seal could be used on its own, without the cap, but together with the additional seal 8 or 25. Furthermore the exact shape of the sealing member 1 could be varied and could, for example, be frusto conical or even, with suitable construction of the sealing surface areas, of generally cylindrical shape. In this latter circumstances the seal member 1 could be arranged to maintain its position at its two ends and to bow outwards, or even inwards, between these two ends when the nipple is screwed in. The cross section of the seal provided within the bell shaped seal member 1 is not necessarily of circular form.It could have, for example, a rectangular or square cross-section or could be specially shaped so as to correspond with the shape of the inner side of the bell shaped sealing member 1.

Furthermore the seal could be provided of a material having sufficient resilience and flexibility that it could slide over the hexagonal annulus thus enabling assembly without removing the nipple 10 entirely from the wheel cylinder 11. The indications provided by the two piece construction of the cap 6 could be provided by moulding on a single piece moulding.

The construction shown with the strap 5 connected at the larger end of the bell could be replaced by a construction in which the strap is connected to the smaller end of the bell.

Where the provision of a non-integral second seal member is provided, means could be provided in the bell shaped seal member 1 for retaining the additional ring therein so that the two seal members could be slid onto the nipple in a single operation.

From the above described embodiment it will be seen that the sealing arrangement of the present invention provides for a good airtight seal between the bleed nipple and the wheel cylinder so as to prevent any spillage of brake fluid even with the use of high pressure brake bleeding systems and even when the nipple is undone to a larger extent than is normally necessary for brake bleeding purposes. It will of course additionally provide the usual good air-tight seal between the bleed nipple and the wheel cylinder to avoid the inrush of air along the screw thread of the nipple.

It will also be seen that the sealing arrangement of the present invention has the additional advantage of maintaining the parts where the nipple and cylinder join together clean so as to avoid to a large extent corrosion and to prevent foreign materials jamming the nipple thread which could result in stripping of the threads necessitating replacement of the complete wheel cylinder.

It is to be noted, that while the described embodiments relate to a seal for brake bleed nipples, it is also applicable to other devices needing bleeding, such as automotive hydraulic clutches.

Claims

1. A seal for a bleed nipple comprising a resilient sealing member adapted to surround a bleed nipple between a nut like annulus provided for actuation of the nipple and the slave cylinder, wherein the sealing member is adapted to seat around the body of the bleed nipple with its outer surface providing a first sealing surface against the rim of the nut like annulus of the bleed nipple, the opposite end of the sealing member forms a second sealing surface for engaging the body of the slave cylinder and an additional sealing surface is provided within the sealing member to provide a third sealing surface acting between the body of the bleed nipple and the slave cylinder at the point where the two are connected, the resilience of the sealing member being such as to retain the three sealing surfaces against the said parts of the bleed nipple and the slave cylinder during limited axial movement of the bleed nipple.

2. A seal as claimed in claim 1, wherein the sealing member is generally bell shaped with an aperture at its narrow end for seating around the main part of the bleed nipple, the second sealing surface being provided by the wide end of the bell.

3. A seal as claimed in claim 2, wherein the third sealing surface comprises an "0"-ring seal located within the bell.

4. A seal as claimed in claim 2, wherein the third sealing surface comprises a sealing surface moulded integrally with the bell.

5. A seal as claimed in any of claims 1 to 4, wherein a cap member adapted to seat over the outer end of the bleed nipple is attached to the sealing member by a strap.

6. A seal as claimed in claim 5, wherein the cap member strap and sealing are produced from a single piece plastics moulding.

7. A seal as claimed in claim 5, wherein the cap member is provided in two parts with a transparent base portion, the parts being separable for the insertion of an indication therebetween, visible through the transparent base portion.

8. A seal for a bleed nipple substantially as described herein with reference to the drawings.