GB2174797A - Pressure relief/sealing caps - Google Patents

Abstract

A pressure relief/sealing cap comprises a generally cylindrical outer member (2) open at one end and internally threaded (3) at the open end for screwing on to and off the threaded neck of a vessel e.g. a vehicle radiator or an overflow vessel therefor, an inner member (9) attachable to the outer member and defining therewith a chamber, a pressure relief valve (23) and a vacuum relief valve (24) mounted within the chamber, and means (21, 22; 7, 8) provided on the inner and outer members, which means are cooperable to attach the inner member to the outer member, the attachment being effected by first moving the inner member generally axially and freely within the outer member and then effecting relative rotation between the members to engage said means, whereby the inner member is attached to the outer member. <IMAGE>

Description

SPECIFICATION Pressure relief/sealing caps This invention relates to pressure relief/sealing caps forvessels or systems containing a pressurisedfluid and more particularly, but not exclusively, to caps for the cooling systems of automotive vehicles.

For many years, radiators of automotive vehicles have been formed with a filler opening surrounded by a neck,thefiller opening being closeable by a cap which serves basically to seal the pressurised cooling system of thevehicle, ofwhich the radiatorforms part, but is fitted with a pressure relief valve which operates to vent the system if the pressure therein rises above a predetermined value. Such a radiator cap has been of the bayonet type in which at least two opposed lugs on the cap engage corresponding slots of cut-outs in a flange on the filler neck, subsequent rotation of the caps serving to pull it into pressure sealing engagement with the neck.

In more recent times, there has been a move away from the provision of a filler opening and neck on a radiatorforthe cooling system of an automotive vehicle to the use of an overflowvessel connected to the radiator and having an externally threaded neck surrounding a filler opening, to which necka pressure relief/sealing cap is fitted. The overflow vessel is normally of a synthetic plastics material, whereby it is readily formed with such a filler neck, compared with the manufacturing technique required to provide the filler neck on a metallic radiator.

The overflow vessel is fitted with a screw cap embodying a pressure relief valve which operates to ventthe cooling system if a predetermined pressure is exceeded, as before, and a vacuum relief valve which operates to allow airto enterthe overflow vessel if the pressure therein falls below a predetermined value due to fluid being sucked back into the radiator, again as before.

Known screw caps of this type involve a relatively complex, and hence expensive, assembly procedure involving welding,forexample, and this isto be avoided. In British Patent Specification No. 2,128,595 there is disclosed a pressure cap which does not involve welding together any of the components but it suffers from other disadvantages. The cap comprises inner and outer members which are assembled together by being locked mechanically such that, once assembled, the two components are not readilyseparated. Tothis end,the inner orouter member is formed with a tag which is resiliently deflected when the inner member is inserted into the outer member but springs back on relative rotation in one direction of the inner and outermembersto engage the other memberto prevent relative rotation in the reverse direction.The disadvantages ofthis arrangement are that the insertion ofthe inner memberwithin the outer member requires a certain force to overcome the interference between the inner and outer members resulting from the deflection of the tag, and there is a danger of the tag being broken as a result ofthis interference if tight manufacturing tolerances are not maintained, and/or ifthe inner and outer members are misaligned when brought together, whereby the tag fouls a partofthe other member not dimensioned to permit the tag to pass thereby.

According to one aspect of the present invention there is provided a pressure relief/sealing cap comprising a generally cylindrical outer member open atone end and internally threaded at the open end for screwing on to and offthethreaded neck a vessel, an inner member attachable to the outer member and defining therewith a chamber, a pressure relief valve and a vacuum reliefvalve mounted within the chamber, and means provided on the inner and outer members, which means are cooperableto attach the inner memberto the outer member, the attachment being effected byfirst moving the inner member generally axially and freely within the outer member and then effecting relative rotation between the members to engage said means, whereby the inner member is attached to the outer member.

The inner member may have a peripheral flange and said means may be in the form of at least two, but preferably four, equispaced projections extending from the flange, and the outer member may be provided with slot means which, on relative rotation ofthe inner and outer members, receive the respective projections of the inner member and are provided with means for holding captive those projections. Each projection may be formed with a portion normally lying outofthe plane ofthe projection but capable of being sprung into that planewhen the projection engagesthe slot means, the portion springing backto its normal position when aligned with a recess in the slot means, whereby the inner member is held captive within the outer member.

The slot means maycomprise individual slotsfor each projection and may be closed atone end to limit the relative rotation between the inner and outer members. The slots may open from passageways in the outer member which extend generally parallel to the axis thereof and which may interruptthe threads ofthe outer member, these passageways forming part of pressure relief paths serving to vent the vessel, when the cap is fitted thereto, when the pressure relief valve opens, and to allow air to be drawn into the vessel when the vacuum reliefvalve opens.

The inner member may be a generally circular, dished plate having a central aperture formed to receive means to effect the relative rotation between the inner and outer members on assembly thereof.

According to another aspect of the present invention there is provided a method of assembling a pressure relief/sealing cap comprising a generally cylindrical outer member open at one end and internallythreaded at the open end for screwing on to and offthe threaded neck of a vessel, an inner member attachable to the outer member and defining therewith a chamber, a pressure reliefvalve and a vacuum reliefvalve mounted within the chamber, and means provided on the inner and outer members, which means are cooperable to attach the inner memberto the outer member, the method comprising the steps offirst moving the inner member generally axially and freelywithin the outer member, and then effecting relative rotation between the members to engage said means, whereby the inner member is attached to the outer member.

A pressure relief/sealing capforthecooling system of an automotive vehicle and constructed and assembled in accordance with the present invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which Figure 1 is an exploded view of the cap, Figure 2 is a plan viewfrom below ofthe assembled cap, Figure 3 is a section,to a larger scale, on the line 111- 111 of Figure 1 but showing the cap fitted to the neck of a vessel, and Figures 4 and 5are scrap sections showing certain details of the cap.

Referring to the drawings, the pressure relief/sealing cap illustrated is designed for a cooling system of an automotive vehicle and fits either onto the neck of an overflow vessel or bottle, partially indicated at 1 in Figure 3, which is connected to the radiator (not shown) forming part of the cooling system, or directly onto the radiator.

As seen most clearly in Figure 1, the cap comprises an outer member 2 which is generally cylindrical, being open at one end and internallythreaded at 3 at that open end. The outer member2 is formed with four equispaced, radially-extending recesses which form slots or passageways 4 generally parallel to the axis ofthe outer member. The passageways 4 interruptthe screwthreads 3 as well as what is, in effect,an annular rib 5.Aslot7 is provided in each discrete portion ofthe rib 5, the slot being open to one side of the adjacent passageway 4 but closed at the other end 10. Each slot7 has a recess 8formed in one side thereof, the recess extending into the base, or a raised portion thereof, ofthe outer member 2 in a generally radial direction.The outer member 2 is mouldedfrom a heatstabilised, glassfibre reinforced polyamide and the external surfaces of the passageways4 provide convenient gripping areastoeffectscrewing and unscrewing ofthecap relative to the neck of the bottle 1, or the radiator (not shown). It will be appreciated that a greater number of gripping areas may be provided if required.

The cap further comprises a circular inner member 9 which is moulded from similar material to that of the outer member 2 and is in the form of a dished plate which, when assembled into the outer member, defines a chamber 11 (Figure 3) with the closed end ortop ofthe latter. More specifically, the inner member 9 has a peripheral flange 12 and the dished portion isstepped at13and 14to providea portion 15 ofsmaller diameter which has a central aperture 16 formed with four equispaced slots or recesses 17 for a purpose to be described. An upstanding flange 18 surroundsthe aperture 16 and extendstowardsthe closed end ofthe outer member 2, the flange being chamfered at 20 for a purpose to be described.

The peripheral flange 12 of the inner member 9 has four equispaced, radially-extending projections 21 of a width slightly smaller than that of the passageways 4 in the outer member 2. Each projection 21 has a central portion 22 which normally lies out ofthe plane of the projection but which is capable of being sprung into that plane as will be discussed hereinafter.

In the chamber 11 defined between the inner and outer members 9 and 2 there are mounted a pressure reliefvalve 23 and a vacuum reliefvalve 24, both of conventional form (Figure 3). The pressure relief valve 23 comprises a valve member in the form of a cup 25 having a peripheral flange 26 which has a slight curvature to present a convex seatfor cooperation with a ring seal 27 which, togetherwith the cup 25, is located by, and retained within,the portion 15 of the inner member 9. The inner diameter ofthe seal 27 is generally located by the upstanding flange 18 surrounding the central aperture 16.A valve spring 28 retains the pressure relief valve 23 in the normally closed position, the compression spring acting between the flange 26 of the cup 25 and the closed end ofthe outer member 2.The spring 28 is located at one end in a recess 29 in the end ofthe outer member 2, and by the body of the cup 25 which it encircles atthe other end.

The vacuum relief valve 24 is mounted on the cup 25 ofthe pressure reliefvalve and comprises avalve member in the form of a disc 31 having an annular rib 32 to provide a seating against a seal 33, and a poppet 34 attached to the valve member 31 at one end and acted upon atthe other end by a compression spring 35 which engages the head 36 ofthe poppet at one end and the base ofthe cup 25 atthe other.

The cap is assembled byfirst placing the pressure reliefvalve 23 and the vacuum valve 24 in position on the inner member 9 or outer member 2, the chamfer 20 on the flange 17 facilitating the placement ofthe seal 27 within thye inner member. The spring 28 is then placed in position either in the outer member 2 oroverthe cup 25 and the inner and outer members 9 and 2then broughttogetherwith the projections 21 being in alignment with the passageways 4 that the inner memberfirst moves freely and axially within the outer member until the projections are in line with the respective slots 7, this movement serving to compress the spring 28.The inner and outer members 9 and 2 are then relatively rotated so thatthe projections 21 enterthe respective slots 7, whereby the portions 22 are sprung generally into the plane ofthe projections from their normal positions. Continued relative rotation of the inner and outer members 9 and 2 results in the central portions 22 ofthe projections 21 becoming aligned with the respective recesses 8 in the slots 7, whereby these portions spring backto their normal positions and engage the recesses so thatthe outer member 2 holds captive the inner member 9. This relative rotation ofthe inner and outer members 9 and 2 is preferably effected by engaging driving dogs (not shown) in the recesses 17 in the central aperture 16 in the portion 15 ofthe inner member9. Itwill be appreciated thatthis feature facilitates automatic assembly ofthe cap which may be accomplished by employing cam means which will serve to effect the relative rotation ofthe inner and outer members 9,2 5 10 15 20 25 30 35 40 45 50 55 60 65 following the initial relative axial movementwhilst utilising only a linearassemblystroke.

To assist the assembly step of rotating the inner and outer members 9,2 relative to each other, the leading projections 21 may be tapered or chamfered, as seen in plan view, to provide a lead-in. Equally, the portions 22 may be tapered in thickness to provide a lead-in portion atthe leading edge thereof, as seen in the direction of assembly rotation ofthe inner member 9 relative to the outer member 2, to the respective slots7. Thetaper may extend the full width of each portion 22 or may terminate short of the trailing edge (relative to the direction of rotation ofthe inner member 9 within the outer member2, with the remaining partthus having a portion of substantially uniform thickness. Each portion 22 is also tapered radially ofthe inner member9 towards the centre thereof.

Once the assembled cap is screwed onto the neck ofthe overflow bottle 1 orthe radiator(notshown), the system is sealed by a seal 37 and the operating pressure of the cooling system is determined bythe strength ofthe spring 28 and when this pressure is exceeded,thevalve member 25 is lifted offtheseal 27 againstthe action ofthe spring and the cooling fluid is vented to atmosphere through relief paths made up ofthe chamber 11 and the slots or passageways 4.

These same paths serve to allowairto enterthe overflow bottle 1 or radiator if the pressure (vacuum) therein reaches a value atwhich thevalve member31 ofthevacuum reliefvalve 24 is pulled off its seat on the seal 33 against the action ofthe spring 35.

Itwill be seen that a pressure relief/sealing cap according to the present invention affords the necessary pressure and vacuum relief and yet is much simple to assemblethan known caps in which the inner and outer members are utltrasonically welded together with the attendant difficulty of holding these components together during welding.

In contrastto the arrangement of British Patent Specification No.2,218,595, the free relative movement ofthe inner and outer members 9,11 during the first part ofthe assembly requires no force so that damage during this step, or in general, to the mechanism locking thetwo componentstogether is minimised ifnotobviated.

The recess 29 in the base of the outer member2 may be omitted and alternative spring locating means employed such as, for example, a plurality of protrusions from the base ofthe inner member and extending generally parallel to the axis thereof and located so asto be disposed within the end turn of --t#spr{ng 28 adjacent the base. In a further alternative arrangement, the pips may be employed in addition to the recess 29.

It will beappreciated that the cap can be made from any desired material which may be metallic or a sWntiiic plastics material, for example.

Claims (14)

1. A pressure relief/sealing cap comprising a generally cylindrical outer member open at one end and interna l ly th readed at the open end for screwing on to and offthethreaded neck of a vessel, an inner member attachableto the outer member and defining therewith a chamber, a pressure relief valve and a vacuum relief valve mounted within the chamber, and means provided onthe inner and outer members, which means are cooperableto attachthe inner memberto the outer member, the attachment being effected by first moving the inner member generally axially and freely within the outer member and then effecting relative rotation between the membersto engage said means,wherebytheinner member is attached to the outer member.

2. Acapaccordingto claim 1,wherein the inner member has a peripheral flange and the attachment means comprise a plurality of equispaced projections extending from the flange, with the outer member provided with slot meanswhich, on relative rotation of the inner and outer members, receive the respective projections and are provided with means for holding captive those projections.

3. A cap according to claim 2,wherein each projection is formed with a portion normally lying out ofthe plane of the projection but capable of being sprung into that plane when the projection engages the associated slot means, said portion springing back to its normal position when aligned with a recess in the slot means, whereby the inner member is held captive within the outer member.

4. Acapaccording to claim 3, wherein the slot means comprise individual slots for each projection, each slot being closed atone end to limittherelative rotation between the inner and outer members.

5. A cap according to claim 4, wherein the slots open from passageways in the outer member which extend parallel to the axis thereof and which interruptthethreads of the outer members, the passageways forming part of pressure relief paths.

6. Acap according to any of 2to 5,whereinthe projections are chamfered to provide lead-in portions attheir leading edges as seen inthe direction of assembly rotation ofthe inner member relative to the outer member, whereby entry into the slot means is facilitated.

7. Acap according to any of claims 2 to 6, wherein each said portion of each projection is tapered in thickness to provide a lead-in portion at the leading edge thereof as seen in the direction of assembly rotation ofthe inner member relative to the outer member, whereby entry into the slot means is facilitated.

8. A cap according to claim 7,whereinthetaper on each said projection stops short of the trailing edge thereof so as to provide a portion of substantially uniform thickness.

9. A cap according to claim 7 or 8, wherein each said portiontapers radially ofthe inner member towards the centre thereof.

10. A cap according to any ofthe preceding claims, wherein the inner member is a generally circular, dished plate having a central aperture formed to receive means to effect relative rotation between the inner and outer members on assembly thereof.

11. A method of assembling a pressure relief/sealing cap comprising a generally cylindrical outer member open at one end and internally threaded atthe open endforscrewing on to and off the threaded neck of a vessel, an inner member attachable to the outer member and defining therewith a chamber, a pressure reliefvalve and a vacuum relief valve mounted within the chamber, and means provided on the inner and outer members, which means are cooperableto attach the inner memberto the outer member,the method comprising the steps of first moving the inner member generally axially and freely within the outer member, and then effecting relative rotation between the members to engage said means, whereby the inner member is attached to the outer member.

12. A method according to claim 11, wherein the steps of moving the inner member generally axially within the outer member and then effecting relative rotation between the inner and outer members are accomplished by employing a linear assembly stroke in conjunction with rotarycam means,thelatter imparting the relative rotation on completion ofthe axial movement step.

13. A pressure relief/sealing cap substantially as herein particularly described with reference to the accompanying drawings.

14. Avehicle cooling system comprising a pressure relief/sealing cap in accordance with any of the preceding claims.