Control for a pumping system used in association with a machine tool fluid circuit

Abstract

Output of a fluid supply unit in a fluid circuit associated with a machine tool is controlled by operating a pump motor at a constant speed, maximum in the preferred form of the invention, during the entire fluid supply operation and varying the connection between the motor and a pump to vary the flow conditions, such as flow rate, pressure or the like of fluid being supplied. Pump output is directly related to the degree of coupling in one form of the invention. Accuracy of fluid output response is improved over prior art systems by locating a flow characteristic sensor immediately adjacent to the output of the pump and controlling volume adjacent to the pump output and the flow characteristic sensor so changes in flow conditions are rapidly located adjacent to the flow characteristic sensor.

What is claimed and desired to be secured by Letters Patent is as follows:  
     
         1 . A variable volume and pressure fluid supply system for use with a machine tool comprising: 
 a motor which operates at a constant speed;    a pump fluidically connected to a fluid circuit of machining fluid used in a machine tool;    a controlled coupling connecting said motor to said pump, said coupling including 
 a first element connected to said motor to be operated by said motor at the speed of the motor,  
 a second element connected to said pump to operate said pump, and  
 a coupling means movable between a coupling position coupling said first element to said second element in a manner that drives said second element at a speed that essentially matches the speed of said motor and an uncoupled position at which said first and second elements are de-coupled from each other, said coupling means having means for varying the degree of coupling between said first and second elements so the speed of operation of said pump is a function of the degree of coupling between said first and second elements.  
   
     
     
         2 . The fluid supply system defined in  claim 1  wherein said coupling means includes a magnetic element that is controlled by a magnetic field associated with said magnetic element with an increase in magnetic field strength increasing the speed of the pump toward the speed of the motor.  
     
     
         3 . The fluid supply system defined in  claim 1  wherein said coupling means includes a hydraulic motor and a hydraulic pump with an increase in hydraulic pump pressure increasing the speed of said pump toward the speed of said motor.  
     
     
         4 . The fluid supply system defined in  claim 1  further including a fluid pressure sensor positioned in the output line of said pump.  
     
     
         5 . The fluid supply system defined in  claim 4  further including a fluid flow control element positioned in the output line of said pump upstream of a fluidic connection between said pump and the fluid circuit.  
     
     
         6 . The fluid supply system defined in  claim 5  wherein said fluid flow control element includes a flow orifice.  
     
     
         7 . A method of supplying machining fluid to a machine tool comprising: 
 using a pump, pumping machining fluid to a machine tool based on demand of the machine tool;    driving the pump using a motor;    operating the motor at maximum speed for essentially the entire pumping step;    variably coupling the motor to the pump; and    varying the coupling between the pump and the motor to vary the flow of the machining fluid to the machine tool.    
     
     
         8 . The method defined in  claim 7  wherein the step of varying the coupling between the pump and the motor includes varying the a magnetic force associated with the coupling.  
     
     
         9 . The method defined in  claim 7  further including a step of using an orifice to control flow out of the pump.  
     
     
         10 . The method defined in  claim 9  further including positioning a flow sensor immediately adjacent to the outlet of the pump and immediately adjacent to the orifice.