GB1167722A - A device for measuring the level of a liquid - Google Patents

Abstract

1,167,722. Liquid level indication. CASTROL Ltd. Dec.20, 1966 [Sept. 21, 1965], No.40204/65. Heading G1H. A device for measuring the level of a liquid in a vessel, such as the level of oil in the engine sump of a motor vehicle, comprises a tubular probe 6 with a restricted opening 16, the probe being so positioned that the opening is just submerged by the liquid when the liquid is at the desired level in the vessel, the probe also having a piston 15 slidable in the probe, a solenoid 1 for moving the piston within the probe so that gas or the liquid may be drawn into or expelled from the probe through the restricted opening, and means in the form of two switches 8, 9 for sensing the rate of movement of the piston so as to determine whether a gas or the liquid is passing through the constricted opening. In the embodiment described the restricted opening is provided by a ball valve 16 having a leak at its seating. In use the probe is inserted into the hole normally occupied by the dipstick in a motor vehicle with the side arm 7 outside the sump. The solenoid 1 is energized to raise a solenoid plunger 2, the piston 15 and a dash-pot plunger 11 Fig. 2 (not shown). Switch 8 is closed and switch 9 opened. If the level is low air will have been sucked into the probe so that when the solenoid is de-energized the piston returns to its lower rest position rapidly and switch 9 is closed by the solenoid plunger 2 returning to its lower position whereas switch 8 is still closed due to delay effected by the dash-pot. Since the switches are in circuit a signal is passed to operate the dispensing device to feed oil through tube 7, probe 6 and an opening 14 into the sump. When oil is drawn into the probe by raising the piston, the piston returns slowly to its rest position and switch 8 then opens before switch 9 is closed and a signal is sent to indicate that the oil is not below its correct level.