Patent GB-905228-A (GB)
Title: Improvements in or relating to apparatus operable in accordance with a fluid pressure or head
Inventor: PRYKE FORDHAM
IPC: G01L9/00
Filed: 1958-03-14
Abstract: 905,228. Automatic fluid level and pressurecontrol systems. PYNFORD Ltd. March 13, 1959 [March 14, 1958], No. 8271/58. Class 83 (4). [Also in Groups XVIII and XIX] In apparatus for indicating and controlling the pressure head of a conducting or semiconducting working fluid B<SP>1</SP> of the kind comprising an electric circuit with a fluid contact element D<SP>1</SP>, the latter is arranged to dip into a second measuring liquid A<SP>1</SP> which is separately contained in a vertical tube A and does not interfere with the electrical properties of the contact D<SP>1</SP>. The tube A is sealed at its lower end by an unstretched flexible envelope C which readily transmits the pressure from the fluid B<SP>1</SP> to the fluid A<SP>1</SP>. A U-shaped tube A is used when the specific gravity of the liquid A<SP>1</SP> is less than that of the liquid B<SP>1</SP>. The leads from the contact D<SP>1</SP> and from an earthed electrode D<SP>2</SP> immersed in the liquid A<SP>1</SP> preferably extend through a sealing plug in the upper end of the tube A which has a branch tube fitted with a flexible envelope to maintain atmospheric pressure in the tube A above the liquid A<SP>1</SP>. If the working fluid container B is sealed the branch pipe is led to the space above the working fluid. As shown in Fig. 3, the indicating and control device comprises an electronic triode valve E which is normally rendered non-conducting by a bias battery G. When the free surface A<SP>2</SP> of the liquid A<SP>1</SP> rises and meets the contact D<SP>1</SP>, in response to a rise in the liquid B<SP>1</SP>, the negative potential on the control grid of the valve is reduced and the valve E conducts to illuminate an alarm lamp H. This device can also be adapted to give an indication if the liquid B<SP>2</SP> falls below a danger level. In a modification, in which the tube A is earthed and the earthed electrode D<SP>2</SP> is omitted, a relay in the anode circuit of the valve brings a second contact into circuit when the first contact D<SP>1</SP> meets the liquid A<SP>1</SP>, the second contact being located in the tube A slightly below the first contact D<SP>1</SP> to hold the valve E conducting, and thus the indicating and control mechanisms operative, until the liquid has fallen below the second contact. In an arrangement, Fig. 7, for controlling the level B<SP>2</SP> of glue B<SP>1</SP> in a container B when the level A<SP>2</SP> of the liquid A<SP>1</SP> reaches the electrode D<SP>1</SP>, a relay M in a valve E<SP>1</SP> closes contacts M<SP>2</SP> for a holding contact D<SP>3</SP> and also contacts M<SP>4</SP> for closing a drip feed device N, a relay M<SP>1</SP> in the anode of a second valve E<SP>2</SP>, which is non-conducting due to the contact between the fluid A<SP>1</SP> and the electrode D<SP>3</SP>, and has closed contacts M<SP>3</SP> for a holding contact D<SP>4</SP> and closed contacts M<SP>5</SP> which maintain an additional glue feed closed. When the level A<SP>2</SP> of the liquid A<SP>1</SP> falls below the contact D<SP>3</SP> the normal drip feed recommences and if it falls below the contact D<SP>4</SP> the additional glue feed is started, the relay M<SP>1</SP> being energized. Fig. 8 shows an arrangement for delivering measured quantities of liquid B<SP>1</SP>. When a mercury cap R floating on the liquid A<SP>1</SP> meets a rod S carried by an armature S of a relay coil T the latter is energized by a battery V so that the armature descends to close contacts U<SP>1</SP>, U<SP>2</SP> which open a stop cock W and interrupt a supply valve W<SP>1</SP> respectively. Specification 839,192 is referred to.