GB2115524A - Improvements in or relating to pressure control valve assemblies - Google Patents

Abstract

A pressure control valve assembly for a pressure cooker which includes a vent pipe (1) which extends through an aperture in and is secured to the lid (5) of the pressure cooker. A resiliently biassed spindle (2) is movable to close the vent pipe (1). The spindle (2) fits into a bore of the vent pipe (1) and its starting position along the bore is adjustable by means of a rotatable control member (3) to control the pressure at which the spindle opens the vent pipe. The pressure inside the cooker acts on the spindle (2) to push it along the bore against the resilient bias to open the vent pipe, the displacement of the spindle (2) from its starting position being an indication of the internal pressure of the vessel. <IMAGE>

Description

SPECIFICATION Improvements in or relating to pressure control valve assemblies This invention relates to pressure control valve assemblies for pressure cookers particularly domestic pressure cookers.

The thermal input to a domestic pressure cooker should be set in accordance with the required operating pressure in order to achieve efficiency in terms of thermal input, cooking and cooking time.

The setting of thermal input may be facilitated by a knowledge of the actual pressure in the vessel during a cooking cycle, and it is therefore desirable to have a control valve assembly which provides some indication of the pressure in a pressure cooker to which the assembly is fitted.

The present invention provides a pressure control valve assembly for a pressure cooker, the assembly being capable of indicating the operating pressure in a vessel to which the valve is fitted and which is easily set to a required operating pressure and is of simple construction.

According to the invention a unitary pressure control valve assembly for a pressure cooker comprises a vent pipe for venting the interior of the cooker to atmosphere, a pressure responsive spindle movable longitudinally along the vent pipe in response to changes in pressure inside the cooker between one or more different longitudinal positions in which the vent pipe is closed and another position in which the vent pipe is open, and means for adjusting the longitudinal position of the spindle relatively to the vent pipe.

Movement of the spindle towards the other position may be opposed by resilient biassing means.

The arrangement may be such that the spindle, in moving towards the other position projects from the assembly by an amount that indicates the extent of the movement of the spindle.

The adjusting means may also be capable of moving the spindle into a longitudinal position relatively to the vent pipe in which it does not close the latter.

The spindle may have a cylindrical part that is movable into a complementary portion of the vent pipe to close the latter.

The resilient biassing means may be a single helical spring which may act between the spindle and the adjusting means.

Adjustment of the longitudinal position of the spindle relatively to the vent pipe may be effected by rotation of the adjusting means The vent pipe may have an externally threaded portion and in which the adjusting means is in screwed engagement with the threaded portion.

The vent pipe and the adjusting means may be in nested relationship, the adjusting means being apertured to permit longitudinal movement of the spindle in response to pressure changes in the cooker.

By way of example only, an embodiment of the invention suitable for a domestic pressure cooker will now be described in greater detail with reference to the accompanying drawings of which: Figs. 1, 2, 3 and 4 are, respectively, sections on a vertical plane, of the assembly fitted to the lid of the pressure cooker and in first, second, third and fourth pressure settings.

Fig. 5 is a plan view of the valve assembly alid part of the lid, and Figs. 6, 7 and 8 are elevations of part of the assembly in use and under different pressure settings.

Referring first to Fig. 1, it can be seen that the unitary valve assembly comprises a vent tube 1, a pressure relieving spindle 2 movable within the vent pipe 1, a pressure adjuster 3 and a coil spring 4 that loads the spindle 2.

The assembly is shown mounted on the lid 5 (part only of which is shown) of a pressure cooker, the vent pipe 1 extending through an aperture 6 in the lid 5 and being secured in position by a nut 7 screwed over an externally threaded portion 8 of the vent pipe. The assembly is sealed to the lid by means of a sealing ring 9 located between the surface ofthe lid 5 round the aperture 6 and an external shoulder 10 of the vent pipe 1.

The vent pipe 1 has a bore of circular transverse cross-section and open at both ends, the pipe 1 adjacent the lower end (as seen in Fig. 1), being apertured at 11. Alternatively, the design may be such that the nut 7 is extended downwardly, the apertures 11 then being located within the extension and register with holes in the extended portion. The bore has internal shoulders 12 and 13 bounding a portion 14 whose diameter is reduced as compared with that of the bore in the vicinity of the apertures 11 and that of a portion 1 5 lying between shoulder 1 3 and a further inciined shoulder 16. Above the shoulder 16 the bore increases in diameter again.

Externally, the vent pipe 1 is formed with the shoulder 10 referred to above and with an upper portion having an external thread 17.

Approximately midway of its ends, the vent pipe 1 has holes 18 in its wall, the holes communicating with the portion 15 of the bore in the vent pipe.

The pressure relieving spindle 2 is of generally cylindrical fsrm with "flats" 1 9 separated by a shoulder 20 from a portion 21 whose diameter approximates closely to the internal diameter of the portion 14 of the vent pipe bore. The portion 21 is bounded at its upper end by a stepped shoulder 22 which forms a seating for one end of the spring 4 that encircles the upper part of the spindle above the shoulder 22. Secured to the upper end of the spindle is a cap 23. Immediately below the cap 23, the upper part of the spindle carries three spaced, parallel circumferential lines 24, 25, 26 whose purpose is described below.

As can be seen from Fig. 1, the spindle extends through an aperture 27 in the wall 28 of the pressure adjuster 3 which is of inverted, cupshaped form with an internal screw thread 29 in mesh with the thread on the portion 17 of the vent pipe. The adjuster 3 and the vent pipe being thus in a nested relationship. The lower surface 30 of the wall 28 has a seating 31 for the other end of the loading spring 4.

The "free" length of the spring 4 - that is to say, the no load length - is selected so that when the spring is in position as shown in Fig. 1, there is a downward force acting on the spindle 2 via the shoulder 22 which maintains the cap 23 in contact with the upper surface of the wall 28.

When the valve assembly is secured to the lid 5 as shown in Fig. 1, it will be appreciated that rotation of the adjuster 3 will raise or lower the spindle 2 relatively to the position occupied by the spindle 2 in Fig. 1 in accordance with the direction of rotation of the adjuster 3. Rotation of the adjuster 3 in one direction raises the latter relatively to the vent pipe 1 and, acting through the cap 23, raises the spindle 2 from the Fig. 1 position. Rotation of the adjuster 3 in the other direction will, because of the loaded condition of spring 4, allow the spindle 2 to follow the downward movement of the adjuster 3 relatively to the vent pipe 1 so the spindle 2 moves downwardly. Thus, it is possible to preset the extent, if any, to which the portion 21 of the spindle 2 projects into the portion 14 of the bore in the vent pipe 1.

The limit of downward movement of the spindle 2 occurs when the upper edge 32 of the vent pipe 1 contacts the lower face 30 of the wall 28 and when that happens the shoulder 22 seats on the shoulder 13 as shown in Fig. 2. In that position of the spindle 2, the portion 21 thereof extends into and slightly beyond the portion 14 of the bore in the vent pipe 1.

The limit of upward movement of the spindle 2 occurs when rotation of adjuster 3 in the one direction is prevented by a stop (not shown). This position is shown in Fig. 3 and it will be observed that the portion 21 of the spindle 2 is clear of the portion 14 of the bore in the vent pipe 1.

Fig. 4 shows the spindle 2 in a position intermediate the positions shown in Figs. 1 and 2.

Thus, it will be appreciated that when the pressure cooker is in use, the pressure generated within the cooker will act on the lower faces of the portion 19 and of the shoulder 20 because of the relatively close fit of the portion 21 in the portion 14 and, if sufficient, will lift the spindle 2 against the loading of the spring 4. Continuing increase in the pressure within the cooker will continue to lift the spindle 2 until, when the portion 21 thereof clears the portion 14 of the vent pipe 1 , the interior of the cooker will be vented to atmosphere via the holes 11 and the pressure within the cooker will drop and the spring 4 will cause the spindle 2 to move downwardly and the portion 20 to re-enter the portion 14 of the vent pipe 1 so closing the interior of the pressure cooker from atmosphere.If the heat input to the cooker is unchanged, the process just described will be repeated.

The pressure within the cooker at which venting occurs will depend upon loading of the spindle 2 by the spring 4 and upon the position of the portion 21 of the spindle relative to the portion 14 of the vent pipe 1.

The loading of the spindle 2 by the spring 4 is preset and fixed but adjustment of the vertical position of the spindle 2, and thus of the portion 21 thereof relative to the portion 14, is adjustable by rotation of the adjuster 3.

The assembly is so arranged and dimensioned that with the spindle 2 in the Fig. 2 position venting occurs at an internal cooker pressure of 1 5 Ib/in2, whilst the internal pressures at the spindle settings shown in Figs. 1 and 4 are 5 and 1 0 Ib/in2 respectively. In the Fig. 3 position of the spindle 2, the interior of the cooker is vented to atmosphere ab initio and pressure build up within the cooker does not occur, the internal pressure thus being atmospheric.

As can be seen from Fig. 5, the upper surface of the wall 28 carries an engraved pointer 32 at the surface of the lid 5 immediately below the valve assembly has marks 33, 34, 35 and 36 indicating the rotational positions of the adjuster 3 corresponding respectively with zero pressure, 5 Ib/in2, 10 Ib/in2 and 1 5 ibiin2 internal pressures.

The adjuster 3 is constrained by the stop referred to above to rotate from the mark 36 past marks 35, 34 to mark 33 and back. The position of each mark may be indexed by some suitable mechanism which may emit an audible "click" or other noise as the adjuster moves into the position indicated by a mark. The mechanism prevents the adjuster readily moving from a set position when the pressure cooker is in use.

Furthermore, as the spindle lifts on increasing pressure within the cooker when in use, the upper end of the spindle 2 starts to project above the wall 28 of the adjuster 3 and exposes one or more of the lines 24,25, 26.

To use the cooker, a user first adjusts the rotary position of the adjuster 3 to the required cooking pressure by aligning the arrow 32 with that one of the marks 34, 35 or 36 indicating the required pressure or with the mark 33 if a "steaming" procedure is required. The pressure cooker lid is then locked in position and the contents of the cooker are then heated either by placing the cooker on a source of heat or, where the cooker includes a built-in heater, by energising the latter.

As pressure within the cooker builds up, the upper part of the spindle 2 starts to move out of the adjuster and, when the movement of the spindle is sufficient to allow the portion 21 thereof to clear the portion 14 of the bore in the vent pipe, that one of the lines 24, 25, 26 corresponding with the pressure setting of the adjuster 3 is aligned with the upper surface of the wall 28 thereof. The user then reduces the rates of heat input to a level which maintains the appropriate line at or about the aligned position.

Figs. 6, 7 and 8 show the spindle positions attained at the operating pressures of 1 5, 10 and 5 ib/in2 respectively.

The valve assembly described is of relatively simple and economic unitary construction and is easy to use. The spring 4 prevents undue movement of the spindle 2 when the cooker is in use so that the user is not startled by the sudden venting of the cooker if the latter is subjected to vibration or movement. The spring 4 is totally located within the valve assembly and cannot be stretched by a user and possibly damaged.

It will be appreciated that the spindle may have only one pressure position and a steaming position or it may have only two or more different pressure positions.

Claims (1)

1. A unitary pressure control valve assembly for a pressure cooker comprising a vent pipe for venting the interior of the cooker to atmosphere, a pressure responsive spindle movable longitudinally along the vent pipe in response to changes in pressure inside the cooker between one or more different longitudinal positions in which the vent pipe is closed and another position in which the vent pipe is closed and another position in which the vent pipe is open, and means for adjusting the longitudinal position of the spindle relatively to the vent pipe.

2. An assembly as claimed in claim 1 in which movement of the spindle towards the other position is opposed by resilient biassing means.

3. An assembly as claimed in claim 1 or 2 in which the arrangement is such that the spindle, in moving towards the other position projects from the assembly by an amount that indicates the extent of the movement of the spindle.

4. An assembly as claimed in any one of claims 1,2 or 3 wherein the adjusting means is adapted to move the spindle to a longitudinal position at which it does not close the vent pipe.

5. An assembly as claimed in any one of claims 1 to 4, wherein the spindle has a cylindrical part that is movable into a compiementary portion of the vent pipe to close the latter.

6. An assembly as claimed in any one of claims 2-5, wherein the resilient means is a single helical spring.

7. An assembly as claimed in claim 6 in which the resilient biassing means acts between the spindle and the adjustment means.

8. An assembly as claimed in any one of claims 1 to 7, wherein the longitudinal position of the spindle is adjustable by rotation of the adjusting means.

9. An assembly as claimed in any one of claims 1-8, in which the vent pipe has an externally threaded portion and in which the adjusting means is in screwed engagement with the threaded portion.

lOAn assembly as claimed in claim 9 in which the vent pipe and the adjusting means are in nested relationship, the adjusting means being apertured to permit longitudinal movement of the spindle in response to pressure changes in the cooker.

11. A pressure control valve assembly substantially as herein described with reference to and as illustrated by the accompanying drawings.

12. A domestic pressure cooker including a pressure control valve assembly as claimed in any one of claims 1 to 11.