Patent GB-753180-A (GB)
Title: Priming arrangements for centrifugal pumps
Inventor: HILL ROBERT ALLAN
IPC: F04D9/04
Filed: 1954-06-29
Abstract: 753,180. Centrifugal pumps. WATEROUS CO. June 29, 1954, No. 19050/54. Class 110(1) [Also in Group XXXI] A priming arrangement for a centrifugal pump comprises an impeller shaft connected to gear means selectively engaged by a drive gear on a drive shaft connectible tn a power source, the drive gear being engageable in one position with a priming pump gear which is connected by a freewheel to a priming pump, and an electric motor connected to the priming pump, the freewheel acting to disengage the priming pump gear from the priming pump when the rotational speed of the electric motor is greater than that of the priming pump gear. A centrifugal pump for use in fire fighting comprises two impellers 12, 13, Fig. 1, which can be connected in series or in parallel by suitable valves (not shown). A drive shaft 26 connected to the vehicle engine carries a slidably mounted gear 25 which, when in the position shown in Fig. 1, drives the centrifugal pump through gears 22, 23. The gear 25 can be moved by a manually-operable selector rod 60 and fork 59 into the position shown in Fig. 2, in which it engages a gear 32 to drive a rotary priming pump 34 having meshing rotors or gears 45, 46. A freewheel of the roller and wedge type is interposed between the gear 32 and the shaft 33 of the priming pump 34. The priming pump 34 can alternatively be driven by an electric motor 54, which is directly connected to the shaft 33; the freewheel allows the motor 54 to drive the shaft 33 while gear 25 is still engaged with gear 32. Gear 25 can be moved further to the right from the position shown in Fig. 2 into a neutral position, and can be moved still further to engage a toothed member 30 by means of internal teeth 29 so as to connect the drive shaft 26 to the vehicle wheels through a shaft 31. The selector rod 60 is retained in its four positions by detents 65. Preferably, a sleeve 63 and cap 64 are provided to enclose the end 62 of the rod 60. The motor 54 is controlled by a relay 74 which can be energized through either one of two circuits selectable manually by a switch 86. When switch 86 is in the left-hand position, the relay 74 is energized throught a normally-closed pressure-actuated switch 92 and a switch 82 which is closed by engagement of the selector rod 60 with a blade 89 when the gear 25 is in the position shown in Fig. 1. The motor 54 then drives the priming pump 34 to prime the centrifugal pump, and when the discharge pressure of the latter has risen sufficiently, it actuates the switch 92 into the open position, thereby stopping the motor 54. Priming automatically recommences if the discharge pressure of the centrifugal pump falls below the value at which the switch 92 is held open. When switch 86 is in the right-hand position, and the gear 25 is in the neutral position, the relay 74 is energized through a switch 80 which is closed by the engagement of a lug 95 in a recess 96. The priming pump 34 is then driven by the motor 54 until either the switch 86 is opened or the gear 25 is moved from the neutral position. The above-described circuits may be replaced by a simplified circuit comprising a manually-operable switch which energizes the motor 54 through a relay. In a, modified construction, the electric motor is connected to the opposite end of the priming pump drive shaft.