Tachometer mechanism

Claim 1

A TACHOMETER FOR INDICATING A PROPER SPEED OF OPERATION OF A FILM DEVELOPING PROCESS SUBJECT TO PREDICTABLE FILM VELOCITY INCREASES AS A FUNCTION OF TEMPERTURE INCREASES, COMPRISING: A CASING DEFINING A CYLINDRICAL CHAMBER; CRANKING MEANS FOR DRIVING A FILM THROUGH THE DEVELOPING PROCESS AT CONTINUOUSLY VARIABLE VELOCITIES AND FOR SIMULTANEOUSLY ROTATING SAID CASING AT CORRESPONDING VELOCITIES; INDICATOR MEANS ROTATABLE WITHIN THE CHAMBER AND DETECTABLE THROUGH SAID CASING TO PROVIDE A ZERO INDICATION AT THE ZERO ROTATION OF SAID CASING AND CORRESPONDINGLY HIGHER INDICATIONS AS SAID CASING IS ROTATED; A HYDRAULIC FLUID WITHIN THE CHAMBER SUTIABLE FOR PROVIDING A FLUID COUPLING BETWEEN SAID CASING AND SAID INDICATOR MEANS IN ACCORDANCE WITH THE EFFECTIVE VISCOSITY THEREOF; AND MEANS FOR THERMALLY COUPLING SAID FLUID TO A CHEMICAL OF THE DEVELOPING PROCESS TO VARY THE VISCOSITY OF SAID FLUID IN ACCORDANCE WITH THE CHANGE OF PROCESS SPEED OF THE CHEMICAL WHEREBY OPERATION AT A PARTICULAR INDICATION WILL PROVIDE PROPER OPERATION OF THE PROCESS SPEED OVER A RANGE OF TEMPERATURES.