This invention relates to the field of waste outlet fittings, in particular to such fittings normally used with sinks, hand basins, shower trays, baths, bidets and the like, which for convenience are commonly referred to herein as "basins". Known waste outlet fittings comprise a flange which is located within the bowl of the basin and defines a seat for co-operation with a plug to close the outlet. In some cases the plug is incorporated in the fitting which also includes means for raising and lowering the plug, such fittings being known as "pop-up waste" fittings. At the lower end the fittings comprise externally threaded tubular parts for connection to further pipework leading to the drains.

Safety regulations require that waste outlets should be fitted with a water trap for preventing flow of unpleasant smelling gases back up through the pipes from the drains. The water trap, often in the form of a ϋ bend, is generally connected to the waste outlet by a threaded connection. The water trapped in the bend acts as a seal to prevent the flow of gases, but flow of soiled water through the trap is substantially unimpeded. The need for a water trap is often inconvenient, especially where space is restricted. Thus, shower trays must

frequently be raised to accommodate the traps beneath them. In addition, water traps are not normally easily accessible for maintenance, e.g. to unblock the trap should it become blocked, which is apt to occur from time-to-time. Such operations are especially inconvenient and costly when a trap is concealed by tiling or other permanent fixtures.

According to the present invention there is provided a waste outlet fitting comprising a generally tubular body and a discharge channel extending through the body, characterised in that a support member is mounted within the body, and a diaphragm carried on the support member defines a skirt flaring outwardly in the downstream direction and having a free peripheral edge for sealing engagement with the wall of the channel thereby to form a valve to prevent reverse flow of fluid through the channel.

The diaphragm acts as a valve member which co-operates with the channel wall to define a check valve which allows essentially unrestricted flow of waste water out through the fitting but which prevents flow of gases in the reverse direction. The diaphragm can be accommodated within a waste fitting without having to increase significantly the length of the body, and as the diaphragm valve obviates the need for a water trap a substantial space saving is achieved. A waste outlet fitting with such a valve has the further advantage that it can preclude the need for a separate air admittance valve for allowing air to enter a stack pipe.

The pressure of the water leaving the basin via the outlet causes the diaphragm to deflect downwardly and inwardly, so that the water passes

between the free edge of the diaphragm and the channel wall. When the basin has been emptied the diaphragm under its own resilience returns to its original position, thus sealing the discharge channel from any back flow of gases or water. Any pressure from below only acts to enhance the sealing pressure between the edge of the diaphragm and the wall of the discharge channel. A small volume of water may be retained above the diaphragm when it closes but will not have any adverse effect on the valve operation.

Preferably the diaphragm is accessible, and in particular can be removed from the fitting through the inlet or upstream end of the body, whereby maintenance operations are simplified as the valve can be reached from within the basin.

In an especially convenient embodiment the diaphragm support member is fixed to a cylinder which has a sliding fit in the tubular body and defines the channel wall portion against which the skirt seals. In this way the diaphragm, support member and cylinder can be preasse bled to be inserted and subsequently removed from, the tubular body as a unit, to facilitate manufacture and maintenance.

In order to ensure a reliable seal between the diaphragm and the discharge channel with only light sealing pressure, it is preferable that the elastomeric skirt is substantially conical and inclined at an angle not greater than about 60° to the axis of the tubular body. Tests have shown good results are obtained with an angle in the range of 20° to 60°, more particularly 30° to 40°. The diaphragm may also be provided with support ribs on the underside of the skirt to enhance its stiffness or resilience and/or with annulated ribs on the upper

face of the skirt to enhance the seal with the inner wall of the channel. At its peripheral edge portion the skirt may have a dome-shape so that the channel wall is substantially tangential to the skirt at the sealing location.

According to a preferred feature the channel wall against which the diaphragm seals is lined with a material with which the diaphragm has an enhanced sealing affinity. The channel wall may be coated with an appropriate sealing material, such as PTFE, or a sleeve of elastomeric material may be fitted within the channel wall. When the sleeve is fitted within a cylinder inserted into the tubular body as mentioned above it can also serve to seal the cylinder to the tubular body.

The diaphragm can be clamped to the support member, such as by a screw and washer engaged with the support, but in a preferred embodiment an inner edge of the diaphragm is engaged in a groove provided in the support member to secure the diaphragm in place.

To assist a clear understanding of the invention a more detailed description of some embodiments is given below with reference to the accompanying drawings, in which:-

Fig. 1 is an axial section through a fitting in accordance with the invention;

Fig. 2 is an axial section through another fitting in accordance with the invention.

Fig. 3 is an axial section through a pop-Up waste fitting embodying the invention and

Fig. 4 is an enlarged view of the detail A in Figure 2.

The waste outlet fitting 1 as shown in Figure 1, comprises a generally tubular body 2 which

defines a discharge channel, a strainer 3, a support member 4 in the form of an axial stem integral with the strainer 3, and a diaphragm 6. The tubular body 2 has a flange 8 at its upper end forming a seat for cooperation with a standard plug and adapted to extend around the outlet orifice of a basin, or the like, in conventional manner. The external surface of the body 2 is provided with a screwthread 10 for connection to pipework which connects the outlet fitting to the drains. An aperture 5 is formed in the body for connection with an overflow of the basin, as well known in the art.

The strainer 3 is detachably mounted in the body 2 a short distance below the flange by a bayonet type connection which allows quick release of the strainer, although screw or snap fit connections may be used, or a combination of all three. The bayonet connection comprises projections 7 within the body and segments on the underside of the strainer with grooves for engagement with the projections to allow the strainer to be locked in place and released for removal through the upper end of the body by rotation of the strainer through a small angle.

The stem 4 projects axially downwards from a central hub 9 of the strainer and at its lower end carries the diaphragm 6.

The diaphragm 6 is made of elastomeric material and is substantially conical in shape. It has a central aperture, the edge of which is engaged in a peripheral groove formed in the stem near its lower end. The skirt of the diaphragm is inclined and meets the inner wall of the tubular body at an angle of 10°-40°. With the outer edge of the diaphragm

being curved and upon the skirt being deformed slightly upon insertion into the body 2, the angle of contact may be very small. The free edge 12 of the skirt bears against the inner wall 13 of the tubular body 2 under light pressure due to its own resilience for normally closing off the discharge channel.

The strainer 3, stem 4 and diaphragm 6 form a sub-assembly for insertion into and removal from the fitting body 2.

When the fitting is in use, waste water draining from the basin passes through the strainer 3 and down through the tubular body. The pressure of the water causes the skirt of the diaphragm to deflect inwards. The free edge 12 of the diaphragm is displaced from the inner wall of the body and water flows down the pipe. When the pressure drops the diaphragm returns to its normal position, as shown, and again seals the bore of the tubular body. A small amount of water may remain above the diaphragm. Any gases or liquid forced back up towards the basin are stopped by the diaphragm, the pressure of the gas or liquid pushing the free edge i2 more tightly against the inner wall. No unpleasant smells can therefore return up the outlet pipe from the drains.

An alternative embodiment of the invention is shown in Figure 2, in which the same reference numerals have been used to designate corresponding parts to those appearing in Figure 1. In this embodiment the upper end of the tubular body (2) is counterbored and receives a cylinder 25 with which the strainer 3 and support stem 4 are integral, the discharge channel being defined within the cylinder which defines the channel wall against which the

peripheral sealing edge of the diaphragm bears. To improve the sealing performance of the diaphragm 6 a sleeve 23 of elastomeric material is set into the lower end of the cylinder 25 to line the channel wall portion against which the skirt of the diaphragm 6 bears. Instead of the sleeve 23, the inner surface of the cylinder may be coated with a sealing material such as PTFE. As shown in Fig. 4, the diaphragm 6 is provided with an annulated rib 26 which contacts and seals against the sleeve 23. The lower end of the cylinder 25 is sealed to the upwardly facing shoulder 22 of the tubular body 2 by means of an out-turned flange portion of the sealing sleeve 23. The cylinder 25, support stem 4, diaphragm 6 and sealing sleeve 23 are pre-assembled for insertion into, and subsequent removal from, the tubular body 2 as a unit. This unit or cartridge is held in place by a spring ring 24 received in a circumferential groove 27 in the cylinder 25 and adapted to engage with a snap action in an annular groove formed in the tubular body.

The valve defined by the diaphragm in the fitting of Fig. 2 operates in the same way as described above for the Figure 1 embodiment.

Figure 3 shows the modified version of the fitting of Fig. 2 and intended for a waste outlet of the kind having a pop-up plug. In this embodiment the stem 4 has an axial bore 15. Located inside the bore 15 is the stem 16 of the plug member 14, and the upper end of an actuator rod 17. The rod 17 can be raised and lowered for operating the plug by any known mechanism. The actuator rod is sealed to the stem by an '0' ring 21 which surrounds the rod within the bore 15, but other seal arrangements are possible. The diaphragm is fitted onto the stem 4 in the same manner

as that in the embodiment of Figure 1. Above the diaphragm the stem 4 has a radial hole 18 out through which any water passing down through the bore 15 can escape to the main channel around the stem 4.

The diaphragm 6 defines a check valve which functions in the same way as in the embodiments of Figure 1 and 2. Gases are prevented from passing upwardly through the fitting by the diaphragm, by the ^• 0' ring 21 and by the seal provided by sleeve 23 between the cylinder 25 and the tubular body.

In all the described embodiments valve maintenance is easy. For example, to replace a damaged or worn diaphragm in the Figure 1 embodiment, the strainer is released and the sub-assembly of strainer, support stem and diaphragm can be withdrawn axially out of the body from within the basin. After detaching the old diaphragm and fitting the new one the sub-assembly is re-inserted and the strainer locked in place. In the Figure 2 embodiment the cartridge is withdrawn as a unit allowing easy replacement of the diaphragm 6 and/or sleeve 23. Of course, with the pop-up waste fitting the plug must be lifted out first, and it may be necessary to disconnect the actuating rod from its operating mechanism.