Patent GB-327786-A (GB)
Title: Improvements in or relating to feed motions for drilling machines
IPC: B23B47/18
Filed: 1929-01-29
Abstract: 327,786. Swift & Sons, Ltd., G., and Carter, J. Jan. 29, 1929. Drilling.-In a drilling-machine having a hand feed for the spindle which is automatically changed to a friction power feed on encountering resistance, the hand feed incorporates a spring- pressed plunger which, when actuated in the feeding direction, may ride out of its recess to institute the power feed but which, when actuated in the reverse direction, causes a positive withdrawal of the drill. In one form the hand feeding wheel or lever c<1>, Fig. 1. rotates a boss c which screws on the exterior of a sleeve b which carries the pinion b<3> for feeding the drill spindle. For hand feed the boss is cluched to the sleeve by the spring plunger j engaging a recess in a ring i attached to a plate h<2> keyed to the sleeve of a plate h which is keyed at h<1> to the sleeve b. The plunger j has an inclined end so that when the drill is fed against the work the plunger slips out of its recess and allows the boss c to screw on the sleeve, thus giving axial movement to a sleeve d having a bevelled end d<1> which forces outwards a plunger e tapered at e<1> so as to expand a friction ring f into contact with a power driven worm wheel g and feed the drill by power. The tongue d' on the sleeve d passes through a. slot in the plate h to prevent its rotation therein. To disconnect the power feed the boss c is rotated in the reverse direction, first causing the friction clutch f, g to slip and then allowing the plunger j to slip into its recess to disengage the clutch f , whereupon the angular side of the plunger rotates the sleeve b positively to withdraw the drill. In order to render the power feed ineffective a cap k<3> may be rotated through 90‹ from the position shown, thus causing a tongue k<1> thereon to lie across a slot j<2> in the plunger j and prevent it from leaving its recess in the ring i. To produce a power feed in the reverse direction, e.g. for reaming or boring upwardly, the sleeve b is held stationary during rotation of the boss c, by means of clutch teeth b<2> on the sleeve and similar teeth a' on a boss a<3> freely rotatable on a shaft a passing through the sleeve. The boss a<3> is manipulated by handles a<2> and carries further clutch teeth a<4> which are normally engaged, by a spring a<5>, with teeth on a collar a<6> secured to the shaft so that the latter may be rotated to traverse the drill head by means of a pinion a<1> and gearing (not shown). In a modification, the power driven worm wheel g, Fig. 2, is freely rotatable on the sleeve b between flanges m, h, the former of which is secured to the sleeve and the latter slidably keyed thereto at h<3>. The boss c has internal screw threads b<1> engaging the sleeve and external threads c<2> engaging the boss of the flange h, the pitches of the screws being so arranged that when the drill encounters the work and the plunger j rides out of its recess in the plate h<2> keyed to the flange h, the relative rotation of the flange and boss c causes axial movement of the flange whereupon the worm wheel .is gripped against the flange m and imparts a power feed to the drill, axial movement of the boss c in the reverse direction being prevented by a collar on the spindle a. The plunger j has a conical end and when the boss c is rotated in the reverse direction to stop the power feed is caused to come against a pin n in the plate h<2> to effect a positive withdrawal of the drill. The plunger j shown in Fig. 1 may be substituted for that shown in Fig. 2 and in each modification the friction clutch g &c. is arranged to slip on overload. A graduated disc h<4> attached to the plate h<2> by a screw and nut h<6> co-operates with a pointer (not shown) to indicate the depth of feed and the nut is adapted to engage a trip-lever (not shown) to disengage the power feed at a predetermined depth.