Injection molding machine

An injection molding machine for synthetic resins, including

• a clamping mechanism which comprises a machine bed, a fixed plate provided on said machine bed, a movable plate disposed to be moved toward and away from said fixed plate and a guide member for guiding said movable plate toward and away from said fixed plate;
• molds mounted on opposed surfaces of and between said fixed plate and said movable plate, a clamping plunger connected to said movable plate and extending from said movable plate away from said fixed plate and said plunger being formed with threads in the periphery thereof, a rotary member internally threadedly engaged with said threaded plunger for moving said plunger in an axial direction as said rotary member rotates;
• and a fixed member fixed with respect to said machine bed and located at the rear of said movable plate away from said fixed plate for retaining said rotary member;
• and
• an injection mechanism which comprises a housing near to said clamping mechanism and on said machine bed, and an injection heating cylinder mounted and positioned on the side of said housing facing toward said clamping mechanism, said injection molding machine further comprising transmission means comprising transmission means shaft extending past said clamping mechanism and said injection mechanism, and first gear means rotatably connected with said transmission means shaft in said clamping mechanism for transmitting rotation of said first gear means caused by said transmission shaft means to said rotary member,
• an injection screw advanceable through said injection heating cylinder, and also rotatable in said injection heating cylinder for being rotated to advance material through that said cylinder, a rotary shaft for rotating said injection screw and a second gear for rotating said rotary shaft;
• means for rotating said injection screw by said rotary shaft through said second gear and these means being provided within said housing, said transmission means shaft in said housing supporting a third gear meshed with said second gear of said means for advancing and rotating said injection screw,
• a first electromagnetically-operated clutch mechanism for selectively connecting said transmission means shaft with said third gear, an electric servo-motor as a driving source for driving said transmission means shaft to rotate, a second electromagnetically-operated clutch mechanism disengageable for temporarily stopping and engageable for thereafter starting the application of a turning force of said servo-motor to said clamping mechanism first gear, and a force retaining device comprising an electromagnetically-operated brake for retaining a clamping force on said clamping gear during said temporary stoppage.