GB2303670A

GB2303670A - Compressed triple '0' ring seal

Info

Publication number: GB2303670A
Application number: GB9515157A
Authority: GB
Inventors: Norman Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-07-24
Filing date: 1995-07-24
Publication date: 1997-02-26
Also published as: GB9515157D0

Abstract

A triple 'O' ring 5 and grease layered seal compressed into a cylindrical housing by a compression spring 8 bearing on to a load spreading washer 7 which takes the role of "the lid of the box". The resultant pack presses outward onto all faces of the housing and of the rod running through. The seal needs no adjustment or servicing during its life and can be confidently placed in an inaccessible internal position to separate two interactive materials as found on a P.U. foam dispenser.

Description

COMPRESSED TRIPLE 'O' RING SEAL DESCRIPTION 1) This invention relates to the rear seal of one component polyurethane foam dispensing guns, pistols or implements.

2) P.U. Foam Dispensing Guns/pistols have been in common use for decades. They differ very little in their basic design and operation:- A rod runs through a tight fitting adjustable PTFE cone seal into the pressurized foam chamber on the way to the front dispensing nozzle.

3) The P.T.F.E. cone in the seal shrinks under constant compressive pressure and begins to leak. The adjuster nut must be located and tightened to stop the leak. Over tighten and seizure occurs, insufficient tightening, the leaking persists.

The indication is that an expensive overhaul is required.

4) The whole gun is therefore built so that it is strong and heavy to make it withstand rough treatment - persistent scraping and repeated stripping and repair, with parts replaced. This has been the way for so long it is considered to be normal.

5) What will stop the cycle is a light-weight gun that does not embody a P.T,F.E. cone in its rear seal but does have an inexpensive reliable non-leaking, self adjusting seal located inside the main housing. One that does not fail, leak or require any sort of servicing.

6)The Triple '0' ring seal has been developed to fulfil the requirements as described in the previous paragraph.

7) The seal in its housing is referred to in fig.l.

8) The body 1 . of the foam dispensing gun, pistol or implement, provides the outer dimensions of the foam chamber 2 , the seal housing 3 , and the rod guide 4 9) Three (or more) heavy duty flexible rubber type '0' rings 5. are packed with grease and placed in the seal housing 3 The control rod 6. is pushed through the rod guide 4. and through the centre of the triple '0' rings 5 . A load spreading plain washer 7. is put into place around the control rod 6. and in contact with the '0' rings 5. A control rod return spring 8. is placed behind the washer 7. The opposite end of the spring 8. abuts against the spring stop 9. on the control rod.

10) When the dispenser is assembled all the parts of the seal come together. The spring 8. pushes the washer 7. and the '0' rings 5. into the bottom of the housing 3. Further movement of the washer 7. compresses the '0' rings 5. until they take up their working shape with a trapped amount of grease between them.

11) The pressure within the seal '0' rings is set and maintained by the force obtained from the pre-set trigger return spring. The spring pressure remains consistent due to one spring being common to all and the pre-load is set by a trigger pull of check and once set is non variable.

12) The composite triple seal is situated at the rear of the dispenser where the round section control rod enters the foam chambers on route to the front discharge nozzle, 13) The fluid contained inside the dispenser housing is a moisture curing chemical mixture which must not be allowed to come in contact with moisture laden air until it has been released by the discharge nozzle.

14) The rear seal has therefore to prevent even the smallest leak of internal material to the outside and prevent entry of air from the outside into the material on the inside.

15) The rear seal has also to maintain a smooth sliding and rotating action whilst preventing the formation of cured deposits within the seal that could damage the seal and impair its effectiveness and reliability.

16) Use of single '0' rings has been tried but a film of internal material coats the rod during the sliding action and when in contact with air the build up of hard cured particles tears the softer material of the '0' ring.

17) Use of double '0' rings has been tried but the two interactive materials come together in the space between the '0' rings and a build up of hard cured particles take place inside the seal which quickly ruins the seal.

18) A triple pack of heavy duty '0' rings, grease packed and under a consistent compressive pressure inside a tight housing reliably contains one material to one side of the triple pack, whilst the other material is likewise confined to the other side.

19) Any migrant material gaining entry between the outer '0' rings is kept apart by the centre '0' ring and no interaction can take place.

20) The inclusion of packed grease is essential to the effectiveness of Triple '0' ring seals. Dry seals (no grease) have been tested and in all cases failure of the seal ensued.

Grease packing plays a major part in the exclusion of any material entering the seal. The grease inside the 'O'rings does not dry out, leach or escape. It maintains the smooth operation of the seal and rod throughout its life.

21) The consistent internal pressure of all parts of the Triple Seal is maintained throughout its life by a basic simple setting of a spring pre-load providing automatic compensation for any deviations.

22) The load spreading washer is a close fit onto the rod and in the seal housing it ensures that no large particles pass into the internal parts of the Triple Seal which could damage the '0' rings.

23) With a compressed Triple Seal fitted it is possible to confidently place trigger return mechanism and rear seal inside the body of the foam dispenser thereby reducing gun size, weight and costs considerably.

24) Referring to the drawing No.l it can be seen that the dispenser body 1. provides the outside dimensions of the Control Rod Guide 4, the seal housing 3. and the foam chamber 2.

25) The control rod 6. passes through the rod guide 4, the triple '0' rings 5, the load spreading washer 7. and the control rod return spring 8. The position of the return spring stop 9.

determines the basic spring pre-load.

Claims

1) A Triple rubber type '0' ring seal sited internally in a close fitting housing,each ring surrounded and separated by grease. A sliding rod runs through the ring centres, through the centre of the metal washer and on through the core of the compression spring. A double notch on the rod sets the position of the spring stop. When the dispenser is fully assembled the spring takes up a pre-determined position which applies a compression load onto the pack of '0' rings via the load spreading washer. The three '0' rings and the grease are constrained into a cylindrical pack which is in contact with the control rod and all faces of the housing taking up any small deviations created in manufacture.

The composition of the seal ensures that no leaks will occur, neither inward nor outward, nore as an interface inside the seal itself.

2) A seal as described in 1) but with more than 3 rings.

3) A seal as described in l)but with plastic type '0' rings.

4) A seal as described in 1) but with plastic coated rubber '0' rings.

5) A seal as described in 1) bur with rubber coated plastic '0' rings.

6) A seal as described in 1) but with combined Plastic on Plastic '0' rings.

7) A seal as described in 1) but with any combination of 1, 2, 3, 4, 5 and 6 together.

8) A seal as described in 1, 2, 3, 4, 5, 6, 7, but with a circlip spring stop.