Abstract: A well downhole liquid dispenser is disclosed in which an inlet/discharge port assembly is provided having an inlet port in fluid communication with the shoulders of a conical piston. The point of the conical piston is in physical contact with the discharge channel leading from the center of the inlet/discharge port assembly to the discharge ports on the exterior of the inlet/discharge port assembly. The piston is held in place by an adjustable tensioning mechanism by which the pressure required to depress the piston may be varied to match the hydrostatic column pressure of a liquid column connected to the inlet port of the dispenser such that when the hydrostatic column pressure reaches a desired level, the piston is depressed, allowing fluid to flow from the liquid column regardless of the exterior downhole pressure exerted on the point of the piston through the discharge ports.

Abstract: A method of measuring the distance between vehicles comprising the steps of; emitting light (14) from a first vehicle to define first and second light positions spaced apart a predetermined light distance (L), passing the emitted light through a lens (20) mounted on a second vehicle and having a focal length (f) to present an image (I) of the predetermined light distance (L) at the focal length (f) from the lens, sensing (22) the image (I) at the focal length, producing a signal representing the length of the image (I), storing a scale (28) on the second vehicle which is proportional to the predetermined light distance (L), comparing (26) the length of the image (I) with the scale to produce a signal representing the distance (D) between the vehicles. The method and apparatus is characterized by establishing the predetermined light distance (L) as a constant and fixed length from vehicle to vehicle by using the standard license plate or license plate holder on the first vehicle.