Control system for peck drilling tool

In a drill system where a drill bit mounted on a main feed piston is advanced for stepwise penetration into a work piece under the control of a feed rate control unit, and retracted between each penetration step for removal of cuttings, the combination which comprises:

• (a) spring means for applying a retraction force to said control unit upon the completion of each said penetration,
• (b) means responsive to initiation of each drill bit retraction for applying an arresting force to said control unit in opposition to said retraction force before the drill bit is fully retracted, the retraction force and arresting force being operable to dispose said control unit in a retracted position.

In a peck drilling tool where a drill bit is advanced stepwise with successively increasing penetrations into a work piece, then rapidly retracted between penetrations for removal of cuttings and thereafter rapidly advanced towards each of the successively machined work faces in the work piece, the combination which comprises:

• (a) feed rate control means for controlling the rate of advance of said drill bit,
• (b) follower means for advancing and retracting in unison with said drill bit and for periodically engaging said control means, and
• (c) force generating means for selectively maintaining said rate control means in contact with said follower means during drill bit retraction and for limiting each retraction travel of said control means, said rate control means being operable to arrest each rapid advance of said drill bit beginning when said drill bit is within a predetermined distance from each successive work face.

In a drill system including a drill bit and a feed mechanism for stepwise advancing the drill bit for successively increasing penetrations into a work piece to machine successive work faces therein and for rapidly retracting the drill bit between penetrations for cuttings removal and thereafter rapidly advancing the drill bit towards the work face, the improvement comprising:

• (a) an advance feed rate control mechanism adapted to be added to the drill system and including first means for mechanically engaging the feed mechanism to control the advance rate of the drill bit when the drill bit is within a predetermined distance of each successive work face, said first means being mechanically biased to retract away from the work piece upon the retraction of the drill bit, and (b) modifying means for limiting each retraction of said first means to a predetermined travel to dispose said first means in position for engaging the feed mechanism when the drill bit is advanced to within the predetermined distance from each successive work face machined in the work piece.

In a drill where a tool is advanced and retracted under control of a hydraulically actuated main piston, an add on control unit for use in peck drilling operations which comprises:

• (a) a follower coupled to said piston for advancing and retracting in unison with said tool,
• (b) a hydraulic regulator mounted in the path of said follower for controlling the advance of said tool and including a spring mounted therein to oppose advance movements of said follower, said hydraulic regulator being spring biased to follow the retractive motion of said main piston and said follower,
• (c) a hydraulically actuated control piston having a toe member in said path between said follower and said regulator, and (d) means operable upon each retraction of said main piston to cause said control piston to limit the spring actuated retractive motion of said regulator to a predetermined traverse whereby following each retraction of said tool, said main piston rapidly may advance said tool to the point that said follower engages said toe and thereafter advance said predetermined traverse at a rate controlled by said regulator.