Patent GB-1274259-A (GB)
Title: Improvements in or relating to control devices, especially for water treatment apparatus
IPC: H01H36/00
Filed: 1969-11-19
Abstract: 1,274,259. Ion exchange apparatus. HONEYWELL Inc. 19 Nov., 1969 [23 Dec., 1968], No. 56679/69. Heading B1J. [Also in Division H1] A control device for water softening apparatus comprises a sensing element which is susceptible to a reversible change in dimension depending upon the ions to which the element is exposed, i.e. to the ionic content of the water contacting the element, a magnet connected to a sensing element in a manner such as to be displaced thereby between a first position and a second position when the element undergoes a change in dimension, and a read switch having a pair of magneticallyoperable electrical contacts positioned with respect to the magnet in a manner such that they are open when the magnet is in the first position and closed when the magnet is in the second position. The sensing element may comprise a body of ion-exchange material; the magnet may be made of ceramic material, for example barium carbonate and iron oxide, which has been processed to provide desired magnetic characteristics. The control device illustrated in Figures 1 and 2 comprises a cylindrical housing 10 having end portions 11 and 12 threadably connected to a centre portion 13. End portion 11 is provided with an external thread 14 for mounting the device in water softening apparatus and with an opening 17 to permit entry of water into the interior of the housing; end portion 12 is provided with an opening 18 to permit exit of water from the interior of the housing and with a cylindrical axial extension 22 which mounts a reed switch 26 encapsulated in a glass container 29 which in turn is encapsulated in double-walled heat-shrinkable tubing 30 made for example of polyolefinic material, the contacts 27 and 28 of the switch being connected to electrical leads 16 extending to mechanism of known type, for example a timer, for effecting interchange of the function of the water softening apparatus. Openings 17 and 18 are provided with respective screens 19 and 20, the mesh of inlet screen 19 preferably being finer than the mesh of outlet screen 20. Mounted in the housing by means of a pressure fit ring 32 is a sensing element 34 which is in the form of a split tubular sheet of ion exchange material, for example of the type described in United States Specification 3,250,392, and which is connected, by means of a spring clip 38, to a bushing 36 which in turn is connected to an apertured annular ceramic magnet 40 which surrounds the reed switch. Change in the axial dimension of the sensing element will effect corresponding axial movement of the magnet relative to the reed switch in the direction towards the contacts of the switch thereby to close the contacts which normally are open by reason of a spring 42 which biases the magnet to the position shown relative to the contacts. In alternative embodiments, the contacts are closed by axial movement of the magnet away from, rather than towards, the contacts. Provision of a housing in three threadably interconnected and mutually adjustable portions enables correct initial positioning of the reed switch relative to the magnet to be effected; alternatively, the housing may be in the form of a single integral part.