Patent GB-450446-A (GB)
Title: Improvements in electric switch apparatus for the automatic control of temperature or fluid pressure
IPC: F22G5/00
Filed: 1934-12-11
Abstract: 450,446. Automatic control systems. JONES, C. E., Victory Works, East Parade, Bradford. Dec. 11, 1934, No. 35516. [Class 38 (iv)] Temperature. ; fluid pressure.-Relates to electric switch apparatus for the automatic control of temperature or fluid pressure in which a continuously reciprocated part or pulsator effects the periodic closure of one or other of two switches according as the pressure or temperature is above or below the normal, each period of closure being proportional to the deviation from normal, and in which a member interposed between the pulsator and the switchgear is moved at right angles to the path of the pulsator by a device or actuating part subject to the pressure or temperature controlled, while cams carried by the switches or by the pulsator determine which of the switches is to be closed and the period of closure. In order that the gear may not be strained when the pressure or temperature falls greatly, as when the apparatus to be controlled is taken out of service, the interposed part is connected to the actuating part, operated by variation of pressure or temperature, through an abutting, pin-and-slot or equivalent lost motion connection providing for positive actuation in one direction whereas a spring, weight or equivalent resists this motion and moves the interposed part in the opposite direction. Two constructions are described. As shown in Figs. 2, 3 and 4, the interposed part p1, p2 is mounted on a bell-crank lever 32, 33 moving angularly at right angles to the pulsator, (which is actuated by a motor driven cam 51), about a fixed pivot 34. The crank arm 33 abuts against an intermediate bell-crank lever 36, 37 pivoted upon a sliding bracket 39 and connected by a pin-and-slot 50 to a link 40 actuated by a Bourdon tube B. A spring 32a is connected to the lever 32 and maintains engagement between the lever arms 33, 36 whilst the slot permits the Bourdon tube to contract beyond the normal range of variation of pressure or temperature without actuating the lever 32, 33. A registering pointer T is connected to the link 40 and a setting pointer T2 is connected to the carriage 39, which is adjustable by means of a screw on a spindle 44 engaging the carriage. The lever 32, 33 comprises an arm 32 carrying a member 31 which is flexible in the direction of the pulsator movement and carries stepped pallets P1, P2 which may engage parts 8 of hinged brackets carrying tilting mercury switches. The cam 51 engages a roller 52 on a counterweighted lever 53 which engages the pallets p1, p2. In a modification, Figs. 5 and 6, the pallets p1, p2 are mutually displaced along the flexible arm 73 so as to engage with parts s disposed in line, and the pulsator cam 95 operates a counterweighted bellcrank comprising a pusher 92 engaging the arm 73. The arm 73 is pivoted to a carriage 75 to which a bell-crank 69, 70 is also pivoted. This bell crank is connected by a link to the arm 73 and abuts a pin on a counterweighted three-armed lever 65, 67 also pivoted on the carriage 75 and carrying a pin 65a which lies in a slot in a link 63 coupled to the Bourdon tubes B. The switch mechanism including the pallets s is mounted in a carriage 85 and the carriages 75, 85 are simultaneously adjustable on screwed rods 76, 86, geared together to set the mechanism to maintain a desired temperature or pressure. An indicating pointer T2 and a setting pointer T1 are pivoted on a fixed bracket at 104 and coupled respectively to the pin 65a and the carriage 75. The actuating device sensitive to pressure or temperature may be a spring-controlled piston or diaphragm, a Bourdon tube connected by a pipe to a bulb with mercury filling, a metallic or bi-metallic strip or an electromagnet energized from a thermopile. The coupling means for a Bourdon tube may comprise a pivoted sleeve connected to its inner convolution with the actuating lever journallod on the sleeve and connected to it by a pin-and-slot device. Specification 450,512 is referred to. The Provisional Specification refers to Specifications 344,013 and 344,060, [both in Group XXIX].