A dispenser and related methods of dispensing material, in particular viscous materials, from a container and through a nozzle. The dispenser includes a body portion for holding the container in a fixed relationship with the body portion, a plunger movable to advance with respect to the container to urge material from the container through the nozzle, a motor arranged to move the plunger and a controller arranged to control the motor. The motor is controlled according to a distance traveled by the plunger, for example a dispensing distance or a distance the plunger is retracted away from the nozzle, or the motor is controlled according to a speed of the plunger.
1. A dispenser for dispensing a material from a container through a nozzle, the dispenser comprising:
a body portion for holding the container in a fixed relationship with the body portion;
a plunger moveable to advance with respect to the container to urge material from the container through the nozzle;
a motor arranged to move the plunger; and
a controller arranged to control the motor;
wherein the controller is configured to calculate a back-EMF of the motor from a motor current, and use the back-EMF to calculate an actual motor speed, and configured to compare a desired motor speed and the actual motor speed and is arranged to act to minimize a difference between the desired motor speed and the actual motor speed and thereby to control the motor based on a speed at which the plunger moves,
wherein the controller is further configured to determine a dosing amount of material to be dispensed from the dispenser and to control the motor such that the plunger is advanced a dispensing distance such that the dosing amount is dispensed,
wherein the dispensing distance to be traveled by the plunger is determined as a stand-alone calculation for each dose of material dispensed.
2. The dispenser of claim 1 , wherein the controller comprises an integrator configured to calculate the distance travelled by the plunger, wherein the integrator is reset prior to each dispensing stroke.
3. The dispenser of claim 1 , further comprising a user input arrangement such that the dosing amount can be selected using a dial.
4. The dispenser of claim 1 , wherein, the controller causes the motor to reverse once the plunger has travelled the dispensing distance such that the plunger is retracted from the nozzle.
5. The dispenser of claim 1 , wherein the controller is further configured such that, once a desired amount of material has been dispensed, the motor is reversed to retract the plunger a distance away from the nozzle.
6. The dispenser according to claim 5 , wherein control of the reversing of the motor is based on a distance travelled by the plunger.
7. The dispenser of claim 5 , wherein the distance to be retracted by the plunger is determined as either a function of the distance advanced by the plunger to dispense the desired amount of material or a predetermined distance.
8. The dispenser of claim 1 , wherein the controller is configured to determine the distance travelled by the plunger based on the actual motor speed of the motor.
9. The dispenser of claim 1 , further comprising: a trigger arranged such that depressing the trigger causes rotation of the motor.
10. The dispenser of claim 9 , wherein a degree to which the trigger is depressed directs a speed of rotation of the motor.
11. The dispenser of claim 1 , wherein the body portion holds a plurality of containers and wherein the controller is arranged to dispense material such that a first material dispensed from a first container mixes with a second material dispensed from a second container.