Caliper gauge

Claim 2

A caliper gauge for measuring the thickness of moving sheet material comprising: a. a reference plate over which sheet material is transported; b. a pivotally supported sensing head facing said plate such that said sheet material passes therebetween; c. a pneumatic nozzle in said sensing head facing said plate; d. a pneumatic feedback control system driving a pneumatic piston responsive to backpressure on said nozzle to move said sensing head maintaining said head a predetermined space from said sheet material; e. a pneumatic line, said line being closed by said sensing head in its normal pivotal position and opened by said sensing head being moved to an abnormal pivotal position; f. a pressure sensor, said pressure sensor being responsive to increased flow in said line to cause retraction of said piston; and g. means for continuously monitoring the spacing between said sensing head and said plate.

Claim 3

A caliper gauge according to claim 1 wherein said pressure sensor is a pressure sensitive switch connected pneumatically across a constriction in said line and electrically to a solenoid operated valve operable to release drive from said piston.

Claim 4

In a thickness gauge in which a sensing head is positioned a predetermined distance above the layer to be measured by a closed loop pneumatic system said closed loop pneumatic system comprising: a. A source of gas under pressure; b. A gas operated piston connected to said sensing head; c. A cyclinder enclosing said piston and having an upper end normally above said piston and a lower end normally below said piston; d. A pNeumatic connection between said upper end and the output of a pneumatic control amplifier; e. A connection from said source of gas to a supply input of said control amplifier; f. A first nozzle in said sensing head positioned to face a layer to be measured; g. A pneumatic connection from said firt nozzle to a firt plenum chamber; h. A pneumatic connection from said first plenum chamber to said source of gas said connection containing an isolating constriction; i. A pneumatic connection from said first plenum chamber to a ''''controlled variable'''' input of said control amplifier; j. A second plenum chamber connected to a second nozzle; k. A surface facing said second nozzle at a predetermined fixed spacing; l. A pneumatic connection from said second plenum chamber to said source of gas containing a second isolating constriction; m. A pneumatic connection from said second plenum chamber to a ''''set point'''' input of said control amplifier; and n. Resilient means in said cylinder continuously urging said piston toward a retracted position in opposition to gas pressure from said control amplifier whereby the output of said control amplifier drives said piston and said sensing head in the direction of a layer to be measured until the spacing of said first nozzle from said layer reaches a predetermined relation with the spacing of said second nozzle from said surface.

Claim 5

In a thickness gauge in which a sensing head is positioned a predetermined distance above the layer to be measured by a closed loop pneumatic system said closed loop pneumatic system comprising: a. A source of gas under pressure; b. A gas operated piston connected to said sensing head; c. A cyclinder enclosing said piston and having an upper end normally above said piston and a lower end normally below said piston; d. A pNeumatic connection between said upper end and the output of a pneumatic control amplifier; e. A connection from said source of gas to a supply input of said control amplifier; f. A first nozzle in said sensing head positioned to face a layer to be measured; g. A pneumatic connection from said firt nozzle to a firt plenum chamber; h. A pneumatic connection from said first plenum chamber to said source of gas said connection containing an isolating constriction; i. A pneumatic connection from said first plenum chamber to a ''''controlled variable'''' input of said control amplifier; j. A second plenum chamber connected to a second nozzle; k. A surface facing said second nozzle at a predetermined fixed spacing; l. A pneumatic connection from said second plenum chamber to said source of gas containing a second isolating constriction; m. A pneumatic connection from said second plenum chamber to a ''''set point'''' input of said control amplifier; and n. Resilient means in said cylinder continuously urging said piston toward a retracted position in opposition to gas pressure from said control amplifier whereby the output of said control amplifier drives said piston and said sensing head in the direction of a layer to be measured until the spacing of said first nozzle from said layer reaches a predetermined relation with the spacing of said second nozzle from said surface.

Claim 6

Apparatus according to claim 3 wherein the lower portion of said cylinder is connected to said first plenum chamber by a pneumatic connection providing negative velocity feedback.

Claim 7

Apparatus according to claim 3 further comprising a pressure switch connected between said first plenum and said second plenum operative to disenable sense signals when the pressure in the said first plenum chamber is substantially less than the pressure in said second plenum chamber.

Claim 8

Apparatus according to claim 3 wherein said first plenum chamber, said second plenum chamber, said second nozzle, a plate carrying the surface facing second nozzle and said constrictive isolators are integral in a unitary manifold assembly connecting said source of gas to said control amlifier and said first nozzle.

Claim 9

A caliper gauge for measuring the thickness of moving sheet material comprising: a. a reference plate over which sheet material is transported; b. a sensing head supported facing said plate such that said sheet material passes therebetween; c. a pneumatic nozzle in said sensing head facing said plate; d. a pneumatic feedback control system driving a pneumatic piston responsive to backpressure on said nozzle to move said sensing head maintaining said head a predetermined space from said sheet material; e. said control system including a control amplifier and a connection from below said pneumatic piston to provide velociity feedback to said amplifier such that the drive to said amplifier is reduced as a function of piston velocity; and f. means for continuously monitoring the spacing between said sensing head and said plate.

Claim 10

A caliper gauge for measuring the thickness of moving sheet material comprising: a. a reference plate over which sheet material is transported; b. a sensing head supported facing said plate such that said sheet material passes therebetween; c. a pneumatic nozzle in said sensing head facing said plate; d. a pneumatic feedback control system driving a pneumatic piston responsive to backpressure on said nozzle to move said sensing head maintaining said head a predetermined space from said sheet material; e. said control system including a control amplifier and a connection from below said pneumatic piston to provide velociity feedback to said amplifier such that the drive to said amplifier is reduced as a function of piston velocity; and f. means for continuously monitoring the spacing between said sensing head and said plate.

Claim 11

Thickness measuring apparatus for continuously measuring the thickness of a moving layer of material comprising: a. a sensing head; b. a first pneumatic nozzle in said sensing head facing a layer of material to be measured; c. a second pneumatic nozzle facing a first reference surface at a predetermined fixed spacing; d. a pneumatic control amplifier connected to said first and said second pneumatic nozzle and driving a pneumatic piston responsive to backpressure differences between said first and said second pneumatic nozzle to move said sensing head keeping said backpressure in equilibrium and thereby maintaining said first nozzle at a constant space from said layer of material related to said predetermined fixed spacing; e. said pneumatic piston being contained in a pneumatic cylinder and connected by a piston rod to said sensing head, the portion of said piSton rod inside said cylinder being surrounded by a compression spring for urging said piston in a first direction, the end of said cylinder in said first direction containing a pneumatic inlet for gaseous pressure to drive said piston in a second direction against the force of said spring, the end of said cylinder in said second direction having a connection connecting said cylinder to the input of said control amplifier to provide velocity feedback; and f. means to continuously monitor the distance from said sensing head to a second reference underlying said layer of material.

Claim 12

Thickness measuring apparatus for continuously measuring the thickness of a moving layer of material comprising: a. a sensing head; b. a first pneumatic nozzle in said sensing head facing a layer of material to be measured; c. a second pneumatic nozzle facing a first reference surface at a predetermined fixed spacing; d. a pneumatic control amplifier connected to said first and said second pneumatic nozzle and driving a pneumatic piston responsive to backpressure differences between said first and said second pneumatic nozzle to move said sensing head keeping said backpressure in equilibrium and thereby maintaining said first nozzle at a constant space from said layer of material related to said predetermined fixed spacing; e. said pneumatic piston being contained in a pneumatic cylinder and connected by a piston rod to said sensing head, the portion of said piSton rod inside said cylinder being surrounded by a compression spring for urging said piston in a first direction, the end of said cylinder in said first direction containing a pneumatic inlet for gaseous pressure to drive said piston in a second direction against the force of said spring, the end of said cylinder in said second direction having a connection connecting said cylinder to the input of said control amplifier to provide velocity feedback; and f. means to continuously monitor the distance from said sensing head to a second reference underlying said layer of material.