Cyclic drilling machine

A drilling machine comprising:

• a frame;
• a quill reciprocably mounted in the frame;
• a spindle rotatably mounted in the quill and having a tool at one end thereof;
• a motor operatively connected with the spindle for rotating the same;
• pneumatic feed means for reciprocating the quill in forward and backward directions;
• feed control means for controlling feed speed of the quill, including;
• (a) a hydraulic cylinder having a housing disposed in parallel with the axis of the quill and connected to a liquid tank at one end thereof through a liquid passage, and a ram disposed within the housing and having a portion projecting from the other end of the housing,
• (b) means for biasing the ram in backward direction,
• (c) flow regulating means disposed in the liquid passage for regulating flow of liquid from the hydraulic cylinder to the liquid tank and allowing free-flow of the liquid from the liquid tank to the hydraulic cylinder, and
• (d) engaging means for engaging the quill with the projecting portion of the ram when the quill arrives at a desired position in the forward movement thereof,
• whereby the quill is moved at a rapid speed by the pneumatic feed means until it engages with the projecting portion of the ram and then is moved at a slow speed controlled by the flow regulating means,
• position sensing means for generating a sensing signal when the quill has been moved to the most forward position;
• a slidable member mounted on the frame for movement within a predetermined distance in movement direction of the projecting portion of the ram;
• coupling means mounted on the slidable member for coupling the slidable member to the ram to move the slidable member with the ram by the predetermined distance when the ram moves in forward direction of the quill and thereafter for permitting the ram to forwardly move relatively to the slide member, said coupling means having means to couple said slidable member to the ram to move the former with the latter by the predetermined distance when the ram moves in backward direction by the biasing means and then to stop backward movement of the ram;
• and
• operation control means for controlling the pneumatic feed means to make the quill repeat a drilling cycle wherein the quill once returns on the way of drilling operation and advances again for resuming the drilling operation, and then returns the quill to the most backward position in response to the sensing signal from the position sensing means, said coupling means being adapted to release the stop operation for permitting backward movement of the ram after the position sensing means generates the sensing signal.