AP30A

AP30A - Improvements relating to pinch type valves.

Info

Publication number: AP30A
Application number: APAP/P/1987/000062A
Authority: AP
Inventors: Baarrett Morley Musgrave
Original assignee: Zimbabwe Valves Private Ltd
Priority date: 1986-06-30
Filing date: 1987-04-30
Publication date: 1989-01-11
Also published as: EP0251261A2; EP0251261A3; DE3770343D1; CA1301139C; ES2023381B3; ATE63986T1; AU7491887A; EP0251261B1; JPS6388382A; AP8700062A0; ZA874672B; US4781356A; AU598559B2

Abstract

The invention is concerned with valves with the type known as pinch valves being those valves which are closed or opened by the action of pinching or releasing a resiliently deformable sleeve. The invention is characterised principally in having a light weight open-sided box section valve housing combined with a pair of substantially cylindrical sleeve supports which allow the use of a resilient sleeve which incorporates no internal bracing.

Description

IMPROVEMENTS RELATING TO PINCH TYPE VALVES

This invention is concerned with valves generally and more particularly with valves of the type known as pinch valves, being those which are closed and opened by the action of pinching or releasing a resiliently deformable sleeve.

Valves of this kind are commonly used in particularly, the mining industry, although they are found in practically any application where abrasive or corrosive substances are being pumped. In such aforementioned applications it is also not uncommon to find the well known diaphram type valve.

Principle amongst the reasons for using such valves is that the abrasive/corrosive nature of substances being pumped would soon destroy the close tolerances found in the more common gate valve, thus rendering such valves unservicable in a short period of time. It has been found that the pinch type valve is the most suitable in such applications as the sleeves are generally made from a heavily reinforced rubber compound which is resistent to wear/oorrosion .

flAD ORIGINAL

The nature of presently known and used pinch valves is such that they suffer from a number ci diadvantages, not least cf which is their extremely high cost, dictated largely by the flanged sleeves which are of necessity hand made, requiring intricate reinforcing to be able to withstand high internal fluid pressures as well as the repeated operations of opening and closing.

As these sleeves are so heavily reinforced, heavy and expensive closure mechanisms are needed in order to overcome firstly the resilience of the sleeve itself and secondly the large internal area of opposing forces present within the sleeve even at modest fluid pressures. In addition to the above, the action of closing the valve by pinching the

I sleeve imposes enormous localised strain on the reinforcing fibres of the sleeve, rapidly causing delamination of the fibres which in turn weakens the sleeve until it ultimately fails.

As a result of the combined aforementioned disadvantages, the sleeves currently employed do not enjoy a long working life and on average require replacing within a period cf betwee: eighteen months and two years.

By way of comparison, diaphram valves also suffer from a number of significant disadvantages. By and large, such valves are generally less expensive than their pinch type counterparts but they are not able to withstand the same high fluid pressures.

AP 0 0 0 0 3 0

BAD ORIGINAL

As will be generally known, diaphram valves operate on a princple of inducing a flexible diaphram into sealing abutment with a seating arrangement, usually cf metal.

The diaphram rubber is generally comparatively thin in section and sometimes rather hard. This latter restriction is determined more by the requirement to ensure an adequate seal between the valve body and the spindle housing than the need for a hard wearing long life diaphram.

Because of the relatively large surface area of the average diaphram, very high forces are required in order to overcome the internal fluid pressures when attempting to close the valve. This once again necessitates the use of elaborate costly closure means which in some instances involve the use of mechanical assistance in the form of gearboxes or even hydrau1ic/pnematic assistance. It is mainly for this reason that such valves are not suitable for high pressure applications.

At the moment just prior to final closure, any particals in the fluid tend to become trapped and rapidly build up between the diaphram and the seating arrangement, largely as a result of the wedge shaped lead into the closing gap.

As high clamping forces are required to effect a proper seal, the tendency is for such particals to become impregnated into the rubber diaphram which causes rapid deterioration and premature failure.

BAD ORIGINAL

1+ wi 1 I be epprec i a.ted from the aforamentioned diicours<? that there is 3 need to improve m?riy aipects of valve techno Ιο··-Ίν arid it is with this in mind that the inventor has devised what is believed to be a novel pinch type vab>e which encompasses a number of significant advantages and which it is believed will be readi ly suitable as a substitute for present ly known and used valves in most applications.

Therefore, according to the invention, a valve comprising in working combination a housing; means adapted to open or close the valve by inducing pinching formations into open or closed relationship about a. flexible sleeve; m* ans to couple the housing to one or more corresponding f large faces at each opposite end; the valve being principally characterised by the incorporation of a pair of generally cylindrical sleeve supports, said supports being interposed between two opposite sides of the housing in spaced apart substantia Ily parallel

I alignment with one another and further incorporating belled or flared formations at their respective opposing ends and being adapted so as to receive and retain in a sealed manner

AP 0 0 0 0 3 0 a resiliently deformable sleeve.

Further according to the invention, a valve as aforementioned further characterised in that the valve housing comprises an open-sided box formation of relatively light gauge material, strength being inherent in the housing because of the box shape.

In order to facilitate the further under standi ng of the invention, one or mor'e preferred embodiments will now be described in detai I with reference to the accompanying drainings taut without limitation of the basic inventive o'lfcept of the invention.

BAD ORIGINS rig. 1 represents a schematic isometric projection of a valve housing according to the invention;

Fig. 2 represents a schematic cross-sectioned side elevation cf the housing shown in Fig. 1 ;

Fig. 3 represents a schematic cross-sectional end elevation of the housing of Fig. 1 ;

Fig. 4 represents a schematic cross-sectional end elevation of the housing of Fig. 1 showing one method of actuating the va1ve;

Fig. 5 represents a schematic cross-section shewing part of the valve housing of the invention and one method of couoli.cc to a conventional pipe flange; and

Fig. 6 showes a schematic sectioned view of the valve in a closed configuration.

In the ensuing description, like reference numerals will refer

I to the same parts throughout.

Referring firstly to Fig. 1 the general idea of the valve housing can be seen with its box-section 10 comprising the principle structure. The sleeve supports 12 and 12a can be seen with flexible sleeve 14 in place. Holes 16 may either be provided at the time of principal manufacture or may be subsequently drilled to accept all flange table drillings. These holes 16 then provide a means for coupling the valve to any conventional pipe flange or pipe fitting (not shown). The flared portions 18 and 18a of the sleeve supports 12 and 12a can also be clearly seer.. These flared portions 18 and 18a are necessary to allow for the distortion of the sleeve v;h>?n it is in the r ·'n··'-.··^ cl--sec ocsition.

^£3AD ORIGINAL

Referring to Fig. 2, the respective .arrangements of the various components can be more clearly seen. The sleeve 14 can be made from any suitable flexible material and does net require reinforcing as is the case with the prior art.

The sleeve 14 can generally be made from a relatively thick section soft rubber compound which will allow a long working life but which allows the gap 15 between the sleeve supports 12 to be reduced to a minimum. Because the sleeves remain relatively flexible, thin section pinch plates may be usee without inflicting damage to the flexible sleeve 14. This view of the invention clearly illustrates the method by which the flexible sleeve 14 is externally braced by the sleeve supports 12 and 12a. This external bracing allows one to dispense with the very costly hand made sleeves which are .a. feature of the presently known and used pinah valves.

In practice the sleeve 14 will generally be either bonded to the sleeve supports 12 and 12a where they contact same and this will generally ensure a watertight seal. As pressure is increased within the pipeline; the sealing is assisted by the action of the fluid pressure acting upon the internal surfaces of the sleeve 14 thus creating a lip-seal effect between the sleeve 14 and the external bracing 12 and 12a. An alternative method which also provides a flange seal between the valve housing and any correspond!ng pipe flange is illustrated in Fig. 2 where the flexible sleeve 14 may be flanged as illustrated

AP 0 0 0 0 3 0 bad ORIGINAL

In addition to the aforementioned advantages, the elastic nature of the sleeve 14 permits a substantial thickness cf rubber to be pulled or drawn by the pinch plates to where it is needed, that is at the closure faces. It will be readily apparent that it will be an easy matter to effect replacement of the sleeve when this becomes necessary. Also illustrated in Fig. 2 is the relationship between the housing 10 and a conventional type flange 20. A more detailed view of the actual coupling can be seen in Fig. 5 where a gasket 22 is incorporate between the two abutting surfaces.

The view shewn in Fig. 3 clearly shows the flared portions 13 and 18a of the sleeve supports 12. This flared portion 18 is necessary to allow the sleeve 14 to be distorted sufficiently to cut off the flow of whatever is being passed through the valve when the valve is closed. Fig. 4 indicates one method by which the sleeve 14 may be pinched closed, in this instance utilizing a 'G' clamp 24. One could of course use any suitable conventional method but the elastic nature of the sleeve 14 ensures that when under internal pressure it fills every contour including the contour of the pinch plates, thus the total area of displacement on closure is kept to a minimum and thus greatly reducing the closing forces needed and thus enabling one to dispense with the costly and elaborate arrangemen which are a feature of the prior art.

The box section design of the housing 1Π is a significant feature o^c the invention as the box s’n.ap- imparts a considerabi inherent strencth to the unit which enables it to be manufactur

art which in the main, require valve housings to be expensively cast frcm either bronze or iron.

Investigations have shown that the valve housing of the invention particularly when forming part of a pipe line, is capable of withstanding considerable internal pressures and tests have been conducted to as high as 400 pounds per square inch without causing permanent damage to the valve. However, in normal use the valve of the invention will be intended to be used at pressures up to 150 pounds per square inch and at such pressures, it has been found that the box section design is well able to withstand the sort of shock loadings which may be encountered in pipeline engineering.

In Fig. 2 it is clearly illustrated that the outer ends of the sleeve supports 12 and 12a are welded to the inner side of the open box housingj10, the weld being effected in the . I closest practical proximity of the pitch circle diameter of the flange drillings 16. This is done deliberately in order to provide a substantial reinforced back-up to the basic box shaped housing 10 and prevents the high internal fluid pressure from blowing through or deforming the thin wall of the flange housing 10 when same is bolted together with corresponding flange 20.

In the closed position, the pressurized fluid within the resilient sleeve 16 will result in considerable forces being imparted against the pinching mechanisim, which in turn will be forced against the down stream portions of the sleeve supports 12 which in turn will transmit these forces against the flange plate of the valve housin'?. I'’, “h·- forces thus trans^-; cr·· ΰ

c

BAD ORIG^,naL fiance 20 when same is bolted to the housing 10 and secondly, forces are transferred via the structure cf the housing 10 to the up-stream corresponding pipe flange (not shewn). Although as previously stated, the valve of the invention can stand considerable internal pressures without suffering structural failure, presently recognized international specifications require specific flange thicknesses depending upon working pressure requirements. In order to comply with such international specifications, the valve of the invention may optionally be provided with back-up split flange rises 21 as seen in Fig. 2 .

Furthermore, the valve of the invention may be adapted to accept a full range of standard threaded ports by simply bolting on any number of standard screwed flanges. These embodiments are not shown in the various drawings as they are'standard features well known by any person familiar with this field of the art.

In Fig. 6, a valve in accordance with the invention can be see in the closed configuration. The arrowed areas 26 indicate the lip seal effect previously mentioned which occures when the sleeve 14 is under internal fluid pressure, whilst the arrows 23 indicate the tendency of the flexible sleeve 14 to conform closely to the contour within the closed valve. In this configuration, the flanged sleeve 14 is also bended in the areas ;. leaves the sleeve 14 free to stretch and slide over the ur.-bonded areas 32. It can be seen that because of the ·;'. :ii: .· n.-tur·.· of th-· s', oev-· 14, a fairly large seal 3 J :.-

Il will be apparent to persons skilled in this field of the art that the valve of the invention provides a number of s ig.ni f i rant advantages by comparison to the valves which are currently being used in many industrial and agricultural applications .

Claims

1. A value compr ising in working comb inaction a housing;

means adapted to open or close the ualoe by indueing pinching formations into open or closed relationship about •a -flexible sleeve; means to couple the housing to one or more corresponding flange -faces at each opposite end; the value being principally characterised by the incorporation of a. pair of generally cylindrical sleeve supports, said supports being interposed between two opposit sides of the housing in spaced apart substantia I ly parallel alignment with one another and further- incorporating belled or flared formations at their respective opposing erids and being adapted so as to receive and retain in a sealed manner a. resiliently deformable sleeve.

i

2. fl value as claimed in Claim 1 characterised in that the housing takes the form of an open-sided box formation.

3. A value as claimed in either Claim 1 or Claim 2 wherein the resilient flexible sleeve includes no integral reinforcing of its own but relies upon bracing from the sieve supports to withstand high internal fluid pressures.

4. A valve as claimed in any one of Claims 1 to 3 when* the sleeve supports are welded to the inner side of the housing such that the sleeve supports are in the closespracticable proximity to the pinch circle diameter of the fls.nge drillings.