Temperature-control apparatus for a printing machine

A temperature-control apparatus for a printing machine, the apparatus comprising:

• a load which is to be kept at a temperature that is controlled or which includes an element having a temperature to be controlled;
• a pump for pumping temperature control fluid, the pump having a suction side which receives fluid and having a pressure side from which fluid is pumped;
• a source of temperature-control fluid;
• a temperature-control fluid circuit including the pump and the load therein;
• a fluid inlet to the circuit, the inlet to the circuit being at a first connection point located between the suction side of the pump and the load;
• a fluid feed line connected from the fluid source to the inlet to the circuit;
• a fluid outlet from the circuit at a second connection point upstream in flow through the circuit from the first connection point and located between the suction side of the pump and the load;
• a fluid return line connected from the outlet of the circuit to the temperature-control fluid source;
• a temperature sensor in the temperature-control circuit;
• a controllable flow valve in the fluid return line;
• an electronic control circuit connected with the temperature sensor and the controllable flow valve for controlling the valve to control the fluid flow through the valve on the basis of the actual temperature value measured in the circuit by the temperature sensor and for adjusting the valve to maintain a desired temperature value in the load by selectively altering the volume of liquid in the circuit which is pumped by the pump to the load with respect to the volume of liquid that is pumped through the valve to the fluid return line;
• and
• a flow resistance in the temperature-control fluid circuit between the first connection point and the second connection point for generating a back pressure in the circuit such that when the valve is opened, some temperature control fluid can flow from the load through the valve to the temperature-control fluid source.