Patent GB-601253-A (GB)
Title: Improvements in drilling and like machine tools
IPC: B23B47/22
Filed: 1945-02-14
Abstract: 601,253. Drilling, tapping &c. machines. BURGESS, A. F. (Barnes Drill Co.). Feb. 14, 1945, No. 3710. [Class 83 (iii)] [Also in Group XXIX] In a drilling, tapping &c. machine, the tool and work supports are movable relatively to each other and the tool is movable relatively to its support in order to give the effect of a hand feed for the spindle with a power followup for the movable support. The feed may be further controlled by a push-rod having a cam operating a valve stem, and can be held in position by contact with further cam surfaces until a cycle of operations is completed. As applied to a hand feed, the machine comprises a column 12 terminating at its upper end in a forwardly projecting head 14 containing the driving motor, which is in splined connection with the spindle 30, journalled in a carrier 10 arranged for axial movement in guides 23, 25 of a tool-head 9 sliding on ways 15 above a work table vertically adjustable on the column. The carrier movement is limited by collars 26, 27 and restrained by spring plungers 28 that normally maintain the carrier in a central position. Manual control is provided by a lever 37 rotating a headed stud 35, Fig. 5, having an eccentric pin 36 located in a slot in the periphery of the carrier. Movements of the carrier are utilized to control the head bv power means comprising a fluid pressure cylinder 40 movable with the head 9 and having a piston 41 anchored to the frame at 42. Fluid is supplied at 46 to a valve V controlling the piston which may be further influenced by auxiliary valves V1 and V2. The valve V has  a stem 53 supported in an extension 54 of the collar 27 and yieldably anchored by a stop nut  55 and a spring 56 so that the valve normally  follows the movement of the carrier. In the neutral position, there is a slight leakage of pressure fluid through both sides of the valve to exhaust and the resulting pressures on the two ends of the cylinder are such as just to balance the weight of the tool-head. Hand feed in either direction takes place as long as pressure is maintained in the corresponding direction on the lever 37 and at a rate depending on the amount of pressure. For automatic power operation, a rod 60, Fig. 5, having cam surfaces 62<SP>1</SP>, 62<SP>11</SP> is moved transversely of the tool-head so that the cam surface 62<SP>1</SP> coacts with a roller 63 to depress the valve stem 53 and the tool-head is fed rapidly downwards. A roller 74 engages behind a bar 75 and maintains the feed until a cam 77 displaces the rod 60 further, causing the cam 621 to engage the roller 68 also. This closes a byepass valve V2 and feed then continues, at a slower rate as controlled by a metering valve V1, until the roller 74 leaves the lower end of the bar 76 when the spring 63<SP>1</SP> returns the rod 60 and feed ceases. If automatic return to complete a cycle is desired, a screw 79 is adjusted to compress a spring 78 mounted between the collar 27 and tool-head. This additional pressure causes the valve stem 53 to rise and rapid return of the tool-head continues until the end of the stem strikes a stop 80 causing the valve to return to its neutral position. To feed by power without an automatic cycle, pressure on the spring 78 is relieved and the rod 60 is pulled forwardly, the cam 62<SP>11</SP> becoming operative. In this case, the byepass valve is first closed and movement continues at the lower feeding rate as long as the rod is held. In a modification, the cams 62<SP>1</SP>, 62<SP>11</SP> are spring mounted on the rod 60 in such manner as to permit movement by a handle to stop the feed at any time in spite of the bars 75, 76. The handle 37 may then be operated to cause reversal of feed, if desired.