GB1568880A

GB1568880A - Brake bleed nipple seal

Info

Publication number: GB1568880A
Application number: GB2861777A
Authority: GB
Original assignee: Witt J E
Current assignee: Witt J E
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1980-06-11

Description

(54) BRAKE BLEED NIPPLE SEAL (71) 1, JOHN EDWARD WITT of "Cross Trees" Oakcroft Road, West Byfleet, Surrey, formerly of 12 Manor Gardens, Hampton Hill, Middlesex, a British Subject, do hereby declare this invention, for which I pray that a Patent may be granted to me, 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 brake bleed nipple seal.

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 brake cylinder housing. 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.

It is to be noted at this point that this difficulty cannot arise when the bleed nipple is screwed home because, in these circumstances, sealing of the brake system does not depend on the screw thread but on a seating provided in the brake cylinder which cooperates with a suitable surface provided e n the bleed nipple.

The present invention seeks to provide an arrangement for sealing the brake nipple even when undone to a relatively large extent, thus substantialy removing the danger of air inflow around the threads of the nipple.

According to the invention, there is provided a seal for a brake bleed nipple com- prising a resilient bell shaped sealing member adapted to surround a 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.

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

Referring first of all to Figure 1, the sealing arrangement comprises a bell shaped sealing member 1 having a 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 for fitting around a bleed nipple as will be described.

Attached to the bell shaped sealing member 1 is a strap 5 which is connected at its other end to a cap 6 intended for use as a dust cap for covering the end of a bleed nipple to which the tube of the brake bleeding equipment is 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 bleeding nipple itself. In this figure the bleed nipple is given the reference numeral 10 and the brake cylinder is given the reference numeral 11.

As is shown in Figure 2, the arrangement of the nipple and the cylinder is - of standard form, the nipple comprising a main screw threaded body 12 which terminates at one end in a conical seating arangement 13 and at the other end in a straight portion 14 bounded by an annular projection 15 which has a hexagonal face 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 the brake bleeding equipment. 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 seal portion 13 is parted from its seat, here indicated at 19. As can be seen, the threaded portion 12 screws into a thread 20 in the cylinder.

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

In order to position the bell shaped seal 1 on the bleed nipple, the bleed nipple is pushed through the aperture 4 of the bell shaped seal member 1 until it is located with its sealing surface 2 against the axially directed surface 22 of the hexagonal annulus 15. The aperture 4 will normally be increased in size to allow it to pass over the threads of the portion 12. The cap 6 may then be pressed onto the end of the nipple in the position shown in Figure 2 so that it is retained by the projection 16 and the nipple 10 is then screwed in to the wheel cylinder until it takes up the position shown in Figure 2. In certain circumstances it may be adbisable to leave the cap off when screwing in the nipple to provide a greater angle of purchase on the hexagonal portion.

As can be seen from FigUre 2, once the bleed nipple is screwed in, the sealing surface 3 engages the surface 21 of the brake cylinder and in the fully screwed in state, is relatively highly compressed as indicated by the shape taken on by the sealing member itself.

When it is required to carry out a bleeding operation, the cap is first removed from the end of the bleed nipple and the necessary tube for the brake bleeding equipment (not shown) is inserted over the end of the nipple in place of the cap. Then the bleed nipple is undone using a spanner on the hexagonal projection portion 15 until the seat part of the bleed nipple is raised from the seat 19 of the wheel cylinder. This will normally take place after about half a turn.

However, as Figure 3 shows, it is possible for the bleed nipple to be undone considerably more than is necessary for example, three turns, with the sealing member 1 still under compression so as to continue to provide the necessary seal. Furthermore this ability to unscrew the nipple to a larger extent enables the passage from the brake cylinder to be increased thus assisting in the removal of awkward air bubbles or foreign material.

Once the bleeding operation has been completed, the nipple is again screwed back into the cylinder, further compressing the sealing member 1, and the base cap 16 is replaced after removal of the brake bleeding tube.

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.

Furthermore the exact shape of the sealing member 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 circumstance the seal 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. Furthermore the seal may be provided of material having sufficient resilience and flexibility that it can slide over the hexagonal annulus, thus enabling assembly without removing the nipple completely. The indications provided by the two piece construction of the cap 16 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.

From the above described embodiments 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 avoid the inrush of air along the screw thread of the nipple cylinder and maintains its scaling properties even when the nipple is undone to a larger extent than is normally necessary for brake bleeding purposes. 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 threads, which could result in stripping of the threads, necessitating replacement of the complete wheel cylinder.

WHAT I CLAIM IS: 1. A seal for a brake bleed nipple comprising a resilient bell shaped sealing member adapted to surround a bleed nipple between a nut-like annul us provided for actuation of the nipple and the brakecylinder, 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.

2. A seal as claimed in claim 1 wherein a cap member, adapted to seat over the outer end of the bleed nipple is attached to the sealing member by means of a strap.

3. A seal as claimed in claim 2, wherein the cap member, sealing member and strap comprises a one piece plastics moulding.

4. A seal as claimed in claim 2 wherein the cap member is a two part construction, one part of which comprises a transparent base portion, the parts being separable for insertion of an indiaction between the parts so as to be visible through the transparent portion.

5. A seal as claimed in claim 4 wherein the other part of the cap member, the sealing member and the strap comprise a one piece plastics moulding.

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

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. areas, of generally cylindrical shape. In this latter circumstance the seal 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. Furthermore the seal may be provided of material having sufficient resilience and flexibility that it can slide over the hexagonal annulus, thus enabling assembly without removing the nipple completely. The indications provided by the two piece construction of the cap 16 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. From the above described embodiments 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 avoid the inrush of air along the screw thread of the nipple cylinder and maintains its scaling properties even when the nipple is undone to a larger extent than is normally necessary for brake bleeding purposes. 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 threads, which could result in stripping of the threads, necessitating replacement of the complete wheel cylinder. WHAT I CLAIM IS:

1. A seal for a brake bleed nipple comprising a resilient bell shaped sealing member adapted to surround a bleed nipple between a nut-like annul us provided for actuation of the nipple and the brakecylinder, 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.