PURPOSE: To prevent occurrence of pressure change in changing the number of operating pumps, by effecting change in the number of operating pumps after lowering a setting pressure to a tolerable pressure in increasing the number of operating pumps and after raising the setting pressure to a tolerable pressure in decreasing the number of operating pumps.
CONSTITUTION: A pressure setting means 9, a setting pressure raising compensator 10 and a setting pressure lowering compensator 11 are connected via contacts 10a, 11a to a pressure regulator 12 and a means 13 for controlling the number of operating pumps. In increasing the number of operating pumps, changing in the number of operating pumps is effected after lowering the revolutional speed of a variable- speed pump 1 by closing the contact 11a and lowering the setting pressure to a tolerable level. In case of decreasing the number of operating pumps, on the other hand, changing in the number of operating pumps is effected after raising the revolutional speed of the variable-speed pump 1 by closing the contact 10a and raising the setting pressure to a tolerable level. With such an arrangement, it is enabled to prevent occurrence of pressure change in changing the number of operating pumps.
FUJITA SHINJI
HARAGUCHI MASARU
TAKAYAMA KOUICHIROU
| JPS5248316U | 1977-04-06 | |||
| JPS5490601A | 1979-07-18 |
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