Patent GB-708723-A (GB)
Title: Improvements in and relating to apparatus for controlling the angular rotation of electric motors
Inventor: JEFFERSON HAROLD FEARNSIDE
IPC: G05D11/13
Filed: 1951-03-06
Abstract: 708,723. Mixing appliances. BRITISH THOMSON-HOUSTON CO.. Ltd. April 10. 1952 [March 6, 1951], No. 5408/51. Class 86 [Also in Group XXXVII] Materials for road-making are mixed in different predetermined proportions by extracting the required amounts of each material from different bins. As shown, each bin B has its outlet regulated by a paddle P which is driven by an electric motor M, the paddle-shaft being extended to drive a switch IS which is closed once in a prescribed angle of rotation of the paddle. A contactor having coil C and contacts CC controls the motor, the regulating circuit of which also comprises a manually operated selector switch CSS having change-over camoperated contacts arranged to be actuated in different combinations. A uniselector switch SA of the Post Office type has four banks of contacts which are swept over by wipers in unison. self-stepping action of the wipers being provided by an interrupter contact aA and a stepping magnet coil SIA. A uniselector switch SB is operated in series with the switch SA in order to provide the necessary number of working contacts. To deliver a given amount of material from the drum. the contacts C1, C4, C16 of the selector switch CSS are changed over, for example, and a pushbutton PB is pressed and released. This momentarily energizes the stepping magnet coil SIA and the wipers of switch SA are stepped from their "home" contacts on to the first working contact of each bank. This action operates the contactor C to energize the motor M, and the paddle is driven until contact IS closes momentarily to re-energize the stepping magnet coil SIA and to de-energize the motor. The wipers of the switch SA continue to step on, however, until the wiper eA arrives at its fourth contact and the motor circuit is re-established The wipers remain on the fourth set of working contacts until they are stepped once ,more by the closing and opening of switch IS. Thus the wipers of the uniselector switch are stepped rapidly by the self-stepping mechanism of the switch, or slowly, once on every rotation through a unit angle of the paddle, until the wipers of the switch SA return to their "home" position whereupon the wipers of the switch SB step on to their first set of working contacts. The position of contacts CI6 of the switch CSS provides a circuit which enables the contactor C to be operated, causing the motor to run, the paddle to rotate and the contact IS to close intermittently thereby stepping on the wipers of the switch SB until they reach a predetermined set of working contacts on the uniselector. The selfstepping action of the switch SB then returns the wipers to the "home" position whereupon the selector stops. The selector SB may start the selectors associated with another bin, the operation of which is prescribed by a switch similar to the switch CSS. This. and any subsequent bin delivers predetermined quantities of material until the required mixture has been obtained, the whole cycle being re-started either manually or automatically. If a conveyer associated with the bins is sufficiently large, the bins may be adapted to discharge simultaneously instead of in sequence.