Dental syringe

In a hygienic device which includes a supply of liquid, a pump for propelling said liquid in pulses of flow, a motor having a rotor for driving said pump, a switch for supplying electrical power to said motor, means for delivering the propelled liquid to a point of use and a control for adjusting the pressure of the delivered liquid, the improved combination comprising:

• a structure in said motor for concentrating a magnetic field delivering energy to said rotor;
• an electrical winding on said structure having electrical terminals and responsive to said electrical power for inducing said magnetic field;
• a contact element included in said switch and moveable for selectively conductively bridging said terminals;
• an insulated carrier of said contact element for enabling movement of said element into and out of bridging connection;
• an insulated housing receptive of said carrier and fixedly related to said winding;
• means for effecting an hermetic sealing entirely of said winding and said housing;
• means for moving said carrier to effect movement of said element;
• said pump including a cylinder, a piston reciprocating within said cylinder and a piston rod for driving said piston in reciprocation;
• one end portion of said piston defining an outwardly opening internal recess the walls of which internally define a resilient spherical seat;
• a spherical bearing formed on one end of said piston rod and matingly received within said spherical seat;
• said control including a passage through which said liquid is propelled by action of said pump, a bypass for said passage and a valve for adjustably throttling the amount of said liquid conducted in said bypass;
• said valve including a rotatable stem carried within a sleeve having means defining a pair of stops circumferentially displaced around the axis of said sleeve and said stem having a cylindrical surface concentric with said axis;
• a control knob having a pair of radial abutments respectively cooperative with said stops to limit rotation of said knob around said axis between corresponding positions of high and low pressure of the propelled liquid outletting said pump, said knob also including a tube engageable with said cylindrical surface and fixedly secured thereto during assembly when one of said stops is engaged with one of said abutments while said stem is at one limit of rotation;
• said motor including a cylindrical rotor having a bore with circumferentially-spaced longitudinal lugs projecting radially inward thereof;
• and a cylindrical bearing member having circumferentially-spaced longitudinal ribs projecting radially outward thereof, said lugs and ribs interfitting circumferentially and being of a radial extent enabling a secure press fit of said bearing member within said bore.