GB2212560A

GB2212560A - Water supply apparatus

Info

Publication number: GB2212560A
Application number: GB8727098A
Authority: GB
Inventors: Peter Briggs
Original assignee: Stuart Turner Ltd
Current assignee: Stuart Turner Ltd
Priority date: 1987-11-19
Filing date: 1987-11-19
Publication date: 1989-07-26
Anticipated expiration: 2007-11-19
Also published as: GB8727098D0; GB2212560B

Abstract

Apparatus for supplying water under pressure to two outlets comprises two pumps 1, 2, a shuttle valve 6 connected between the outlet ducts 5 of the pumps, a pressure operated switch 15, and a diaphragm tank 18. The shuttle valve is responsive to fluid pressures in the outlet ducts to isolate the pressure operated switch and the diaphragm tank from the outlet duct of one of the pumps when the fluid pressure in that outlet duct is greater than the fluid pressure in the other outlet duct. Thus when one or both of the outlet ducts is supplying water the pressure operated switch will maintain the motor in operation. Two motors may be provided to drive the pumps, both motors being connected to a single pressure switch. <IMAGE>

Description

WATER SUPPLY APPARATUS The invention relates to apparatus for supplying water under pressure to two outlets such as respective hot and cold taps.

The apparatus is particularly useful where a head of water is not available such as in a loft. In such circumstances it is known to provide apparatus comprising a motor driving two pumps for the hot and cold outlets respectively. In known apparatus it is necessary to provide two pressure operated switches controlling the operation of the motor.

The present invention provides apparatus whereby only a single pressure-operated switch need be employed.

Accordingly the invention provides apparatus for supplying water under pressure to two outlets comprising a first pump connected to a water source and through an outlet duct to one of the outlets, a second pump connected to a water source and through an outlet duct to the other outlet, a motor for driving the pumps, a pressure-operated switch for controlling operation of the motor, and a valve arrangement connected between the outlet ducts of the first and second pumps1 wherein the pressure-operated switch is connected to the valve arrangement to be in fluid communication with the outlet duct of one or other or both of the pumps at any given time.

Where diaphragm tanks are employed to maintain the system pressure it has previously been necessary to provide a tank in communication with each outlet. The present invention makes it possible for a single diaphragm tank (or similar pressure device) to be provided in communication with the valve arrangement.

An embodiment of the invention is described below with reference to the accompanying drawings in which: FIGURE 1 is a side view, partially sectioned, of apparatus according to the invention; and FIGURE 2 is a view along arrow A of Figure 1.

The apparatus shown consists of a first pump 1 for cold water and a second pump 2 for hot water. The pumps 1 and 2 are shown mounted on either end of a single electric motor 3 and are therefore always driven together at the same speed.

Each pump has an inlet duct 4 and an outlet duct 5. A check valve is provided in each inlet duct to prevent pressure leaking back to the supply side of the pump. The outlet ducts will of course be connected through piping to the outlets (not shown) which are to be supplied.

A valve arrangement in the form of a shuttle valve 6 is connected between the outlet ducts 5 of the pumps 1 and 2.

The shuttle valve consists of a substantially cylindrical body 7 which has open ends internally screw-threaded for connection to pipe coupling units 51. The open ends of the body 7 provide chambers 8 and 9 which are connected by means of an axial bore 10. Pistons 11 and 12 are mounted for axial movement in the chambers 8 and 9 with a slight clearance and are connected by a rod 13 which passes through the bore 10 with a relatively large clearance.

A first radial bore 14 through the wall of the body 7 communicates with the axial bore 10. An adjustable pressure-operated switch 15 can be fitted directly into the bore 14 or may be connected thereto by means of a suitable conduit as shown by dot-dash line 16.

A second radial bore 17 through the wall of the body 7 also communicates with the axial bore 10. A diaphragm tank 18 can be connected directly to the bore 17 or may be connected thereto by means of a suitable conduit as shown by dot-dash line 19. The diaphragm tank consists of a cylindrical body divided internally into two separate chambers 21, 22 by a rubber diaphragm (not shown). The first of the chambers 21 is in fluid communication with the bore 10 and is thus filled with water. The chamber 22 is isolated from the water in chamber 21 by the rubber diaphragm and contains only air. The purpose of the diaphragm tank is explained below.

Valve seats 25, 26 are provided at the ends of the bore 10 for co-operation with the pistons 11 and 12 which when held by water pressure against a respective seat isolate a respective pump 1 or 2 from the bore 10.

Operation of the apparatus is as follows. After installation of the apparatus and connection of electrical power to the motor 3, the motor will be operated to build up pressure in the system until a pressure level is reached at which the pressure switch 15 is operative to switch off the motor.

Whilst both hot and cold outlets are closed, the pressure in the system is maintained by the diaphragm tank so that the pressure switch continues to prevent operation of the motor.

When, for example, the cold outlet is turned on, pressure in the cold outlet duct will drop and water in the diaphragm tank will be expelled by the rubber diaphragm through line 19, bore 17, bore 10, through chamber 8 past the piston 11, and ultimately to the cold outlet duct. When the pressure in the system has been reduced below the level at which the pressure switch 15 has been set to operate, the switch will be activated to turn on the motor 3; the pumps 1 and 2 thus being activated. If the hot outlet remains closed, pressure will build up in the hot outlet duct and will act on the piston 12 to move it into engagement with the valve seat 26 thus isolating the bore 10, and thus the pressure switch 15, from the pressure generated by the pump 2. This is the condition shown in Figure 1.When the cold outlet is closed, the motor will continue to drive the pumps 1 and 2 until the pressure in the system (leaking past piston 11 (is sufficiently high to activate the pressure switch 15 to turn off the motor 3. This pressure is then maintained in the system by the diaphragm tank. Naturally the apparatus will operate in a similar manner if the hot water outlet is turned on except that in this case the pressure generated by pump 1 will become isolated from the pressure switch 15.

When both hot and cold outlets are turned on the rod 13 and pistons 11 and 12 will drift within the shuttle valve according to the pressures obtaining in the respective outlet ducts.

As will be understood from the above, the purpose of the diaphragm pump is to maintain pressure in the system at a level at which the pressure switch keeps the motor switched off whilst both outlets are closed. The provision of the diaphragm pump prevents constant 'hunting' operation of the motor such as when one or other of the hot or cold outlets has a dripping leak.

The operating pressure for the pressure switch is set at a level above that which will be obtained in an outlet duct when the respective outlet is opened, but below that which could be generated by the pump when the outlet is closed. It will be appreciated that the pumps cannot be of a positive displacement type in the described arrangement since the pressure in, say, the hot outlet duct would continue to rise when only the cold outlet was opened. The pumps should thus be regenerative or centrifugal pumps which have a maximum pressure which will be generated even in a closed system.

Although in the described apparatus a single motor is employed to drive both pumps, two motors can be provided where circumstances, such as the need for greater output, require it. In this case both motors can still be connected to the single pressure switch to be operated thereby.

Whilst the provision of the diaphragm tank is preferred, it is nevertheless possible for the apparatus to operate without this feature.

Claims

Claims:

1. Apparatus for supplying water under pressure to two outlets comprising a first pump connected to a water source and through an outlet duct to one of the outlets, a second pump connected to a water source and through an outlet duct to the other outlet, a motor for driving the pumps, a pressure-operated switch for controlling operation of the motor, and a valve arrangement connected between the outlet ducts of the first and second pumps, wherein the pressure-operated switch is connected to the valve arrangement to be in fluid communication with the outlet duct of one or other or both of the pumps at any given time.

2. Apparatus according to claim 1 wherein the valve arrangement comprises a shuttle valve operable in response to fluid pressures to isolate the pressure operated switch from the outlet duct of one of the pumps when the fluid pressure in that outlet duct is greater than the fluid pressure in the other outlet duct.

3. Apparatus according to claim 2 further comprising a diaphragm tank connected in fluid communication with the pressure operated switch and with the outlet ducts of the pumps via the shuttle valve and being isolated, along with the pressure operated switch, from one or other of the outlet ducts by operation of the shuttle valve.

4. Apparatus according to claim 3 wherein the shuttle valve comprises a cylindrical body having open ends for connection to the outlet ducts; the open ends defining respective chambers connected by an axial bore, pistons mounted for movement in the chambers with slight clearance and connected together by a rod passing through the bore with relatively large clearance, and valve seats at each end of the bore for cooperation with the pistons; the pressure operated switch and the diaphragm tank being in fluid communication with the bore between its ends.

5. Apparatus according to any preceding claim wherein the pumps are driven from a single electric motor.

6. Apparatus according to any preceding claim wherein the pumps are regenerative or centrifugal pumps.

7. Apparatus for supplying water under pressure to two outlets substantially as described herein with reference to the accompanying drawings.