GB2031309A - Improvements in a machine tool - Google Patents

Abstract

A machine tool (10) such as a gun drill has a trip bar (14) which carries at least one trip (14A, B, C) for use in a drilling operation and has a trip bar (14) that is slidable and is adapted to be locked into a setting position for a predetermined drilling depth by using the drill to be employed (D) as a length gauge; which setting may be changed to maintain said predetermined drilling depth by subsequent appeal to the reduced length of the drill (D) if re- sharpened. <IMAGE>

Description

SPECIFICATION Improvements in a machine tool This invention relates to an improvement in a machine tool of the kind (hereinafter referred to as of the kind set forth) that has a trip bar that carries at least one trip for use in a drilling operation and is especially useful,forexample, in a gun drilling machine or the like.

It is known in gun drilling machines, used for the production of precision holes of widely varying depths, to set trips to actuate switches that control the cutting and operating cycles.

Difficulties arise, however, especially when such machines are engaged in long production runs since the natural blunting of the tools and the subsequent resharpening of them for example, or the simple change of one tool for another in a repetitive cycle, may cause the trips to require constant attention and re-setting with a consequent loss of both time and money.

According to the present invention these difficulties are overcome by the provision of a machine tool of the kind set forth in which the trip bar is slidable and is adapted to be locked into a position ab initio of a machine cycle of operations by the length per sue of the drill to give a predetermined drilling depth which position is changed to maintain said predetermined drilling depth by subsequent appeal to the reduced length perse of the said drill when re-sharpened or the length per sue of a drill that is exchanged for said drill.

By the term drill is herein meant any drilling tool with or without associated parts such as shanks, sleeves and the like that constitute the drilling means when fitted to the movable head for a drilling operation of a given length and depth in a machine tool.

The invention will be more fully understood from the following description given by way of example only in relation to the Figures of the accompanying drawings in which: Figure 1 shows a gun drilling machine in oblique prespective.

Figure 2 is a schematic side elevation of a machine similar to Figure 1.

Figure 2A is an enlarged view of part of Figure 2.

Figure 3 is a side elevation of a sliding trip bar and associated parts.

Figure 3A is a section on section station AA of Figure 3.

Figure 3B is a section on section station BB of Figure 3.

Figure 3C is a section on section station CC of Figure 3.

Figure 3D is a section on section station DD of Figure 3.

Figure 4 is a schematic showing the operation of a sliding trip bar of the invention with a drill of a given length ab initio of a drilling cycle and said drill when reduced in length by resharpening.

Referring now to the Figures of the drawings: In Figures 1 and 2 a machine tool in the form of a gun drilling machine shown generally at 10 comprises a bed plate 11, chip box 12, moving power head 13 and sliding trip bar 14.

In Figure 2 the trip bar 14 is seen to be fitted along the side of the machine slideways. Sliding trips 14A, 14B, 14C are clamped to the trip bar 14 to actuate cycle switches that control movements of the moving head 13. These trips 1 4A, 1 4B, 1 4C are set according to the required hole depth to be drilled and drill length to provide respectively a start drilling position (14A), a drilling depth position (14B), and a retracted position (14C) for changing the drill.

The trip bar 14 is mounted so as to provide lengthwise movement /, of twice that necessary to allow for the resharpened life of drill D (Figure 2, Figure 3). Movement of the trip bar 14 is effected by the rotation of an actuator assembly shown generally at A (Figure 2A) fixed to the slideway base. A pin 1 5 in the trip bar 14 engages with a slot 16, not shown in Figure 2A, in a rotary actuator bobbin 1 7.

The trip bar 14 is clamped by tightening a ring nut 1 8. The position of the trip bar 14 and its attendant trips is determined by using the drill D as a length gauge d, as shown in Figure 2A. A Vee-shaped cradle for the drill D is provided in an adjustable support 14D able to be clamped to the trip bar 14 in which the shank of the drill D is rested and by a Vee groove machine in the actuator bobbin 17 that accepts the cutting end 1 9 of the drill D. A fixed end stop 20 is positioned adjacent to the actuator bobbin 1 7 and the distance d, is from an end face of 20f of fixed end stop 20 to an end face 14f of adjustable support 14D.Once the trip bar 14 is set by means of the drill D in use with the two faces 20F and 14F the cycle trips 1 4A, 1 4B, 1 4C are positioned as required along the trip bar 14, to give the preselected drilling cycle.

The drill D is now placed in the moving head 13 and setting is complete and the machine ready for drilling. After drilling a tool change may be required, or the drill may require sharpening, to this end the trip barring nut 18 is slackened and a new drill E placed in the cradle of adjustable support 14D and in the groove in the actuator bobbin 17 which is then rotated to bring the point 1 9, of the re-sharpened or the new drill into contact with the face 20f of the fixed stop 20, thus at one step re-setting the trip bar 14 with all of its associated trips 14A, B, C to suit the new drill length (Figure 4).

The trip bar 14 is now re-clamped and the drill that is to say either drill D sharpened or a new drill D2 placed in the moving head 13 for the drilling operation to be effected.

A preferred trip bar and associated parts are shown in Figures 3, 3A, 3B, 3C and 3D. A sliding trip bar 141 is able to slide a distance determined by the width of a slot 21 and a stop pin 22, fixed to the gun drilling machine (not shown) by a bracket 23 and holes 23i, 232. End stop 201 having end face 2fixed to the machine but is able to enjoy an adjustment provided by locking pin 24 and its associated slot 25 in guide bar 26 slidable in block 27 which is fixed to the machine body.Trips 1 4E, 1 4F are locked on to trip bar 14, by screws 1 4E1, 1 4F,. A slide bracket 28 is attached to the machine bed by holes 28,, 282 and a plate 29 retains bar 14, and is screwed to the bracket 28 by screws 291,292.

Adjustable support 1 4D includes a cradle 1 4D1 having an adjustable stop pin 30 with end face 1 4 and a lock pin 31. The cradle is held in position on the trip bar 14, by screw 32. The cradle has a Vee groove 33 at a distance d2 (Fig. 3C) from the front face 1 4F of the trip bar 141, it is this cradle that accepts one end part of the drill D. An actuator assembly A1 (similar to A of Figure 2A), is seen to advantage in Figures 3 and 3A. An actuator bobbin 17i has a Vee groove distance d2 from the front face 1 4F of trip bar 14, it is this groove that accepts the other end part of the drill D. A pin 15 engages with a slot 16 in the bobbin 171 provided with handle 172. A ring nut 18, has a handle 1 82.

A bracket 34 holds the assembly to the machine by holes 341 342 for suitable screws (not shown).

A pin 35 retains ring nut 18, on its threaded end 35,. The drill D is shown dotted in Figure 3A.

Assume the parts of Figure 3 to be in position for drill D of length d1 of Figures 2, 2A. Then the distance d1 is as shown in Figure 3.

The setting ab initio of a drilling cycle provided by the length per se d1 of the drill D is more fully appreciated from Figure 4. A drill D of length d1 is used by means of fixed end face 20f and end face 1 4f to set trip switches 1 4A, 1 4B, 1 4C on sliding trip bar 14 (POSITION A). The drill D length dr is then placed in sliding head 13 and will drill as required to a depth decided by one of the trips.

Drill D is now resharpened to a reduced length ds (drill D2) and a difference of df is found between d1 and ds df = (d1 - ds).

The resharpened drill of length d8 is now used by means of fixed end face 2wand end face 1 4 to move the trip bar 14 to a new position (POSITION B) through a distance df and this ensures the automatic correct placement of trips 1 4A, 1 4B, 14C at new positions 1 4A2. 1 4B2, 1 4C2 to effect an identical drilling depth for the resharpened drill of reduced length do to that effected with the new drill of length d, as used ab initio of the drilling cycle.

Claims (8)

1. A machine tool of the kind set forth in which the trip bar is slidable and is adapted to be locked into a position ab initio of a machine cycle of operations by the length perse of the drill to give a predetermined drilling depth which position is changed to maintain said predetermined drilling depth by subsequent appeal to the reduced length perse of the said drill when re-sharpened or the lengthperse of a drill that is exchanged for said drill.

2. The machine tool according to Claim 1, wherein the said length of the drill is taken between two opposed flat faces of two spaced apart members of which one is on the trip bar.

3. The machine tool according to Claim 2, wherein each of said flat faces is individually adjustable lengthwise of the machine tool.

4. The machine tool according to any preceding claim, wherein the drill is supported by Vee grooves when its length per se is used to position said slidable trip bar.

5. The machine tool according to any preceding claim, wherein the trip bar can be positioned by the drill over a lengthwise movement substantially equal to twice that necessary to allow for the resharpened life of the drill.

6. The machine tool according to any preceding claim, wherein it is a gun drill.

7. A gun drill constructed and arranged substantially as hereinbefore described and as shown in the Figures of the accompanying drawings.

8. The machine tool according to Claim 1 when operated as hereinbefore described with particular reference to Figure 4 of the accompanying drawings.