Adjustable constant pressure caulk gun

An adjustable, constant pressure gun for dispensing viscous materials such as caulk and adhesive, including:

• a housing including a handle and an operator-actuated trigger;
• power supply terminals for receiving a source of electrical power;
• a motor mounted within the housing to drive a dispensing mechanism;
• an electronic switch mounted within the housing and connected between the power supply terminals and motor, for controlling the flow of current through the motor;
• an operator-adjustable pressure control mounted within the housing and connected to the power supply terminals, for providing a set-point pressure signal representative of a desired dispensing pressure;
• a load monitor circuit mounted within the housing and coupled to the motor, for providing a feedback pressure signal representative of the actual dispensing pressure as a function of the load on the motor;
• a comparator mounted within the housing and connected to the switch, pressure control and load monitor circuit, for comparing the feedback pressure signal to the set-point pressure signal and controlling the switch as a function of the comparison to maintain the actual dispensing pressure within a predetermined operating pressure band of the desired dispensing pressure.

An adjustable, battery-powered, constant pressure gun for dispensing viscous materials such as caulk and adhesive, including:

• a gun housing including a handle and an operator-actuated trigger;
• a trigger switch mounted within the housing and responsive to actuation of the trigger;
• a battery compartment and power supply terminals in the housing, adapted for receiving batteries to power the gun;
• a motor mounted within the housing to drive a dispensing mechanism;
• an electronic switch mounted within the housing and connected between the power supply terminals and motor, for controlling the flow of current through the motor;
• an operator-adjustable pressure control mounted within the housing and coupled to the power supply terminals, for providing a set-point voltage signal representative of a desired dispensing pressure;
• a current-to-voltage converter including a low-pass filter mounted within the housing and coupled to the motor, for providing a feedback pressure signal representative of the actual dispensing pressure as a function of the current drawn by the motor;
• a hysteresis comparator mounted within the housing and connected to the switch, pressure control and current-to-voltage converter, for comparing the feedback pressure signal to the set-point signal when the trigger switch is actuated by the trigger, and for controlling the switch as a function of the comparison to maintain the actual dispensing pressure within a predetermined operating band of the desired dispensing pressure.