GB2122310A

GB2122310A - Pressure cap

Info

Publication number: GB2122310A
Application number: GB08217975A
Authority: GB
Inventors: Henry Clifford Rees Price; Graham Gerald Lardner
Original assignee: Unipart Group Ltd
Current assignee: Unipart Group Ltd
Priority date: 1982-06-22
Filing date: 1982-06-22
Publication date: 1984-01-11
Also published as: EP0097443A1; GB2122310B

Description

1 GB 2 122 310 A 1

SPECIFICATION

Pressure cap This invention relates to pressure caps, and particularly but not exclusively to pressure caps for use with vehicle cooling systems.

It is normal practise for vehicles incorporating liquid-cooled internal combustion engines to em- ploy a pressure cap which is usually located on a filler neck either on the radiator or on an expansion tank. Such pressure caps commonly employ pressure relief valves which permit the passage of fluid, for example air or water vapour, when the pressure exceeds a given under- or a given over-pressure. In this way, the cooling system is maintained in sealed condition while the system pressure is within its normal limits.

It is further known to employ predominantly plastics materials in the construction of such caps, and to employ a screw thread connection between the pressure cap and the filler neck. The valve elements are sometimes retained by a container member which carries the seal with the filler neck and which is ultrasonically welded to the part of the cap which is gripped in use. The necessity of joining the plastics components by means of welding is undesirable in so far as it complicates and thus increases the cost of manufacture.

Moreover, it is known to include in the cap means for venting the underor over-pressure in the systems. One known means employs a twist action cam which acts on the over-pressure valve to lift it clear of its seat, thus breaking the seal. Because of the typical strength of springs employed in such over-pressure valves, the means provided for venting the system has necessarily been quite complex and massive, and has moreover required substantial operating force.

Furthermore, in such pressure caps which employ 105 both under- and overpressure valves, it has been common practise to provide each valve with a seat and a sealing member.

The present invention, viewed from one aspect, relates to a pressure cap including means for venting 110 the system with which it is associated byway of means acting upon the under-pressure valve.

Viewed from another aspect, the invention relates to a pressure cap which has a container member which carries the seal between the cap and a neck with which it is to be associated, the container member being retained in the cap by mechanical means employing a continuation of the screw thread which is used to retain the cap on a filler neck.

Viewed from a third aspect, the invention provides 120 a pressure cap which employs a common seal member for an under-pressure valve and for an over-pressure valve.

An embodiment of the invention will be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a pressure cap in accordance with the invention; and Figure 2 is a cross section taken on the line 11-11 of Figure 1 and Figure 3 is a side view of the cap member.

The drawings show a pressure cap for use, for example, on the coolant radiator or the coolant expansion tank of a motor vehicle, constructed in accordance with the invention. The cap is made largely out of plastics, and consists of a cap member 11, a container member 12, and a number of components concerned with sealing the cap assembly to a filler neck (not shown) and with breaking the seal when the under- or over-pressures within the sea] system exceed predetermined values.

The cap member 11 is screw threaded internally to engage with a corresponding external thread on the filler neck. The cap member has four lobes 13 whose external shape enables the cap to be more readily gripped, and whose internal shap constitutes a break in the screw thread to permit flow of gas or vapour through the cap in circumstances to be described hereinafter. Container member 12 has an external thread similar to that of the filler neck and which likewise engages the internal thread of the pressure cap 11. The thread on the container member 12 is broken at points corresponding to the positions of the lobes 13 to permit a continuation of the internal passages defined by the lobes. The container member is assembled to the cap member by screwing it into the cap until an annular surface 14 on the container member engages a corresponding annular surface 15 on the cap member. Surfaces 14 and 15 each have complementary sloped teeth 16 which permit the container to be screwed into the cap member but prevent dissassembly, thus providing a totally mechanical joining of the components.

The annular surface 14 on the cap is interrupted at intervals by cut-outs 17 at locations corresponding to the breaks in the screw thread, to permit communication with the interior of the chamber 18 defined by the cap and container. Communication between the chamber 18 and the interior of the filler neck is normally prevented by a seal member 19. Seal member 19 constitutes a common seal member for both a valve having a seat 20 for the relief of over-pressure in the filler neck and a vent valve 21 for permitting the inflow of air to the filler neck in the event of an excessive under-pressure in the cooling system. In its role as an over-pressure valve, the common seal 19 lifts off the valve seat 20 against the action of a coil spring 22 acting on a spring plate 13. Vent valve 21 is biased into its closed position by a conical compression spring 24 which acts between spring plate 23 and a flange 25 on a rivet 26which retains the vent valve 21.

A release button 27 is located in a recess in the upper surface of the cap member 11. The release button is biased upwardly by an elastomeric washer 28 which also constitutes a seal against the escape of gas or vapour attempting to pass through a hole 29 in the cap through which the release button extends. The release button is retained in place by a projec- tion 30 from the shaft of the release button, which projection is resiliently biased radially outwardly of the shaft and which is so shaped that upon assembly of the button to the cap it automatically retracts into the shaft until it has passed through the hole 29, at which point it springs outwardly to prevent dissas- 2 GB 2 122 310 A 2 sembly of the button from the cap.

In use of the cap, the spring forces are arranged to ensure that the cap maintains a suitable seal on the filler neck over a pre-determined range of working pressures of the cooling system. Prior to removing the cap at any given time it is desirable to ensure that the pressure in the filler neck is the same as atmospheric pressure to ensure that there will be no uncontrolled release of hot vapour and coolant liquid. The cooling system may be vented by the illustrated cap by depressing the release button 27. This unseats the vent valve 21 communicating the interior of the filler neck with the chamber 18 and thus by way of the lobes 13 to atmosphere. Any escaping vapour or liquid is thus deflected downwardly through the lobes away from the users hand which need only be in contact with the release button. Owing to the relatively small size of the vent valve it is readily possible for the user to lift it from its seat against any Overpressure in the filler neck.

It will be appreciated that there has been described and illustrated a pressure cap which is simple, and therefore cheap, to produce, and which provides a readily usable means for venting the cooling system prior to removal of the pressure cap. The use of a common seal member reduces the number of components present and simplifies assembly.

It will be appreciated however, that numerous modifications to the illustrated cap are possible within the scope of the invention. For example, the release button could be replaced by other suitable external means which are operable on the vacuum relief valve of the cap to vent the cooling system. For example the cap could be provided with a deform- able top which could be pressed inwardly to engage the rivet 26 and displace the vent valve. While it is regarded as desirable for both simplicity and ease of operation that a simple linear movement be required to vent the cooling system (which is rendered possible by the low forces involved), it would be possible to arrange for a rotary knob to be provided with such as a cam to deflect the vacuum relief valve.

Moreover, while the container member 12 effects a multiple role in so far as it acts as a housing for the components of the cap, as a seat for the overpressure relief valve, and as a seat for the seal onto the filler neck, it need not provide all of these functions to gain benefit from its mode of retention by the screw threads of the cap member 11, and by its mechanical retention against dissassembly.

Claims

1. A pressure cap which employs a common seal member for an under-pressure valve and an overpressure valve.

2. A pressure cap as claimed in claim 1, wherein a release member is provided for manually releasing the common seal member to enable the system pressure and atmospheric pressure to be equalided.

3. A pressure cap including means for venting the system with thich it is associated byway of means acting upon the under-pressure valve.

4. A pressure cap which has a container which carries the seal between the cap and a neck with which jt is to be associated, the container being retained in the cap by mechanical means employing a continuation of the screw thread which is used to retain the cap on a filler neck.

5. A pressure cap substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited. Croydon, Surrey, 1984. Published byThe Patent Office. 25 Southampton Buildings. London, WC2A lAY, from which copies may be obtained.

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