Apparatus for measuring time lapse between brake demand and application

Claim 2

Test apparatus for determining the time required for a brake system to develop a critical brake pressure predicated on a predetermined percentage of the maximum fluid brake pressure to which the brake actuator devices of said system are charged in accordance with operation of a control valve device thereof, said apparatus comprising: a. first means for providing an output signal representative of brake pressure effective at said actuator devices; b. an automatic calibrating unit subject to the output of said first means comprising: i. compensating means for modifying the output of said first means in accordance with a correction factor selected to provide a signal representative of said critical brake pressure when said control valve device is operated to provide said maximum brake pressure; and ii. comparator means subject to the output of said first means and said critical brake pressure signal for providing an output signal when correspondence therebetween occurs in accordance with said maximum brake pressure being released and subsequently reapplied; and c. timer means including start means operable concurrent with operation of said control valve device to initiate a timing period and stop means operable responsive to said comparator output signal to terminate said timing period when said critical brake pressure is attained.

Claim 3

Test apparatus, as recited in claim 1, wherein said compensating means comprises a potentiometer adjustable in accordance with said correction factor to provide said critical brake pressure signal.

Claim 4

Test apparatus, as recited in claim 1, wherein said calibrating unit further comprises: a. an electronic storage component subject to a first voltage signal corresponding to the output of said first means for storing a charge corresponding to the maximum brake pressure produced in accordance with initial operation of said control valve device; and b. a diode via which current flows to charge said storage component, said diode preventing loss of charge on said storage component when said first signal is dissipated during release of said brake pressure produced in accordance with initial operation of said control valve.

Claim 5

Test apparatus, as recited in claim 3, wherein said compensating means further comprises: a. a first amplifier operative responsive to the level of charge of said storage component to establish an output signal accordingly; and b. a potentiometer subject to the output of said first amplifier, said potentiometer being adjusted to provide an output which reflects the level of charge of said storage component as modified by said correction factor.

Claim 6

Test apparatus, as recited in claim 4, further characterized in that said first amplifier is a field-effect transistor in circuit with said storage component to provide a high impedance load for maintaining the level of charge of said storage component for an extended duration.

Claim 7

Test apparatus, as recited in claim 3, wherein said calibrating unit further comprises a manually activated transistor device in parallel with said storage component to provide a discharge path therefor.

Claim 8

A test circuit for determining the time required for a brake system to develop a critical brake pressure predicated on a predetermined percentage of the maximum fluid brake pressure to which the brake actuator devices of said system are charged in accordance with operation of a control valve device thereof, said apparatus comprising: a. transducer means for providing an output signal representative of brake pressure effective at said actuator devices; b. signal calibrating means in a first branch of said circuit comprising: i. a capacitor subject to the output signal of said transducer for storing a signal corresponding to the maximum brake pressure developed; ii. signal compensating means subject to said stored signal for modification thereof in accordance with a correction factor selected to produce a signal representative of said critical brake pressure when said control valve device is initially operated to provide said maximum brake pressure; c. comparator means having a first input for registering said critical brake pressure signal and a second input subject to the output signal of said transducer via a second branch of said circuit whereby said comparator means provides an output signal when said brake pressure reaches said critical brake pressure in accoRdance with a reapplication of brake pressure following release of said initial application of brake pressure; and d. timer means including start contacts engageable concurrent with operation of said control valve incident to said reapplication of said brake pressure to initiate a timing period and stop contacts engageable responsive to said comparator output signal to terminate said timing period when said critical brake pressure is attained.

Claim 9

A test circuit for determining the time required for a brake system to develop a critical brake pressure predicated on a predetermined percentage of the maximum fluid brake pressure to which the brake actuator devices of said system are charged in accordance with operation of a control valve device thereof, said apparatus comprising: a. transducer means for providing an output signal representative of brake pressure effective at said actuator devices; b. signal calibrating means in a first branch of said circuit comprising: i. a capacitor subject to the output signal of said transducer for storing a signal corresponding to the maximum brake pressure developed; ii. signal compensating means subject to said stored signal for modification thereof in accordance with a correction factor selected to produce a signal representative of said critical brake pressure when said control valve device is initially operated to provide said maximum brake pressure; c. comparator means having a first input for registering said critical brake pressure signal and a second input subject to the output signal of said transducer via a second branch of said circuit whereby said comparator means provides an output signal when said brake pressure reaches said critical brake pressure in accoRdance with a reapplication of brake pressure following release of said initial application of brake pressure; and d. timer means including start contacts engageable concurrent with operation of said control valve incident to said reapplication of said brake pressure to initiate a timing period and stop contacts engageable responsive to said comparator output signal to terminate said timing period when said critical brake pressure is attained.