Method and apparatus related to the testing of hydraulic circuits

Claim 2

In a method of testing a hydraulic circuit coupled to an auxiliary hydraulic circuit of a testing stand, said auxiliary circuit including a tank into which hydraulic liquid is introduced and from which hydraulic liquid is withdrawn during the course of liquid circulation in said circuits, the improvement comprising the steps of A. continuously effecting a coarse balancing of the flow rates into and out of said tank and B. intermittently effecting a fine balancing of said flow rates in response to those volume variations of the hydraulic liquid in said tank which are greater than the volume variations for the entire auxiliary circuit due solely to the temperature variations of said liquid during normal operation.

Claim 3

In a testing stand for examining a hydraulic circuit, said testing stand including an auxiliary hydraulic circuit having (a) a tank, (b) first conduit means leading to said tank, (c) second conduit means leading from said tank, (d) a variable output high-pressure pump in said second conduit means, (e) a return valve in said first conduit means, (f) a nozzle contained in said second conduit means downstream of said pump, (g) coupling means provided in said first and second conduit means for connecting said auxiliary hydraulic circuit to the hydraulic circuit to be tested, the improvement comprising A. first control means associated with at least one of said conduit means for effecting a continuous coarse balancing of the flow rates of hydraulic liquid entering and leaving said tank through said first and second conduit means, respectively, B. second control means connected with said return valve to operate the latter as a function of the liquid level in said tank related to a reference value and C. means connected to said second control means for varying said reference value as a function of the temperature of said hydraulic liquid in said auxiliary circuit, said second control means and said means connected to said second control means effecting an intermittent fine balancing of said flow rates.

Claim 4

In a testing stand for examining a hydraulic circuit, said testing stand including an auxiliary hydraulic circuit having (a) a tank, (b) first conduit means leading to said tank, (c) second conduit means leading from said tank, (d) a variable output high-pressure pump in said second conduit means, (e) a return valve in said first conduit means, (f) a nozzle contained in said second conduit means downstream of said pump, (g) coupling means provided in said first and second conduit means for connecting said auxiliary hydraulic circuit to the hydraulic circuit to be tested, the improvement comprising A. first control means associated with at least one of said conduit means for effecting a continuous coarse balancing of the flow rates of hydraulic liquid entering and leaving said tank through said first and second conduit means, respectively, B. second control means connected with said return valve to operate the latter as a function of the liquid level in said tank related to a reference value and C. means connected to said second control means for varying said reference value as a function of the temperature of said hydraulic liquid in said auxiliary circuit, said second control means and said means connected to said second control means effecting an intermittent fine balancing of said flow rates.

Claim 5

An improvement as defined in claim 2, said first control means being formed of a balanced valve disposed in said first conduit means, said balanced valve including A. third and fourth conduit means connecting said balanced valve with said second conduit means upstream and downstream of said nozzle, B. a movable valving member for determining the flow rate of hydraulic liquid in said first conduit means, C. a movable abutment limiting the closing move-ment of said movable valving member and D. means positioning said movable abutment as a function of the pressure difference upstream and downstream of said nozzle.

Claim 6

An improvement as defined in claim 3, said balanced valve being disposed in said first conduit means upstream of said return valve.

Claim 7

An improvement as defined in claim 3, said return valve and said balancing valve being combined into a unitary valve structure including A. a first diaphragm having one face exposed through said third conduit means to the liquid pressure upstream of said nozzle and another, opposite face exposed through said fourth conduit means to the liquid pressure downstream of said nozzle, B. means affixing said movable abutment to said first diaphragm, C. a second diaphragm having one face exposed to the liquid pressure in said first conduit, and another, opposite face exposed to atmospheric pressure, D. a third diaphragm, having one face exposed to a pressure signal transmitted by said valve control means as a function of the liquid level in said tank, and another face exposed to a fixed pressure signal, E. a fourth diaphragm disposed between said second and third diaphragms and having one face exposed to said fixed pressure signal and another, opposite face exposed to said atmospheric pressure and F. means affixing said second, third and fourth diaphragms to said movable valving member.

Claim 8

An improvement as defined in claim 2, said first control means including A. a first additional constant output pump disposed in said second conduit means upstream of said variable output pump and operating codirectionally therewith, B. a second additional constant output pump having a slightly lesser output than said first additional pump and being disposed in said first conduit means for driving hydraulic liquid towards said tank, C. a first branch conduit connecting said first conduit means at a location upstream of said second additional pump with said second conduit means at a location between said variable output pump and said first additional pump and D. second branch conduit connecting said tank with said second conduit means at a location between said variable output pump and said first additional pump, said second branch conduit forming part of said first conduit means and containing said return valve.

Claim 9

An improvement as defined in claim 2, said means connected to said second control means for varying said reference value including A. an auxilary reservoir containing hydraulic liquid having a reference level, said auxiliary reservoir being separate from said tank, B. means for varying said reference level as a function of the liquid temperature in said auxiliary hydraulic circuit and C. means for varying said reference value in said second control means as a function of the variation in the reference level of the liquid in said auxiliary reservoir.

Claim 10

An improvement as defined in claim 7, including A. means for vertically movably supporting said auxiliary reservoir, B. hose means for maintaining continuous communication between said tank and said auxiliary reservoir, C. heat expandable means submerged in the hydraulic liquid contained in said tank and D. mechanical means for vertically moving said auxiliary reservoir in response to the extent of expansion of said heat expandable means.