US2108699A

US2108699A - Boring bar

Info

Publication number: US2108699A
Authority: US
Publication date: 1938-02-15
Anticipated expiration: 1955-02-15

Description

F. WALTHER Feb. 15, 1938.

BORING BAR Filed July 3l, 1935 Patented Feb. l5, 1933 UNITED STAT ATET GFFEQE Application July 31, 1935, Serial No. 34,086 In Germany August 11, 1934 fi Claims.

This invention relates to a boring bar.

In known boring bars disposed between centers and intended for fine work the portion carrying the tool can be moved by its own weight at a certain position of the tool edge, after elimination of the centering action aiecting it, so as to bring the edge out of contact with the bored surface. If, however, the edge is not in highest position, it cannot be retracted from the bored 10 surface but is pressed thereon by the weight of the boring bar which cannot be removed without injuring the bored surface or the edge itself.

It has been proposed to overcome these drawbacks by providing the two portions of the boring bar for mutual .centering with cooperating annular guides and making use of avtension member which will rigidly co-nnect both portions and if released permit the tool carrying portion to swing out. This construction is, however, open tothe objection that prior to the withdrawal of the bar from the bore the tensio-n member connecting both portions has to be released to permit the bar to be swung back by the action of a spring.

The invention eliminates these defects of the knowntypes of boring bars and makes possible automatic and positive retraction of the tool edge from the bored surface at any position of the edge, by providing in a central longitudinal bore of the bar a slide member subjected to the 3 action of a spring to abut against the center point of the driver, which member by means of a cone or an inclined surface and the radial displacement of a thrust pin causes the tool to be lifted off from the working surface at any position of the edge.

One form of the invention is illustrated by way of example only in the accompanying drawing, in which a boring bar according to the invention is shown, partly in longitudinal section.

In the drawing:-

Figure 1 shows an elevation partly in section of a boring bar and associated parts embodying the invention;

Fig. 2 is a cross section taken on line II-II of Fig. l, on a larger scale; and

Fig. 3 is a cross section taken on line III-III of Fig. 1, also on a larger scale.

Referring to the drawing, I is a non-pivotal part of the boring bar and 2 the pivotable part thereof which at its: ends is arranged between the centers 3 and 4. The center 3 has a flattened conical end which extends into a bore 5 of the part 2 and engages a slide member 6, longitudinally displaceable in the bore 5 against the action of a compression spring 8. The center 3 also (Cl. 'T7-56) engages a conical seating I9 on the mouth 'of the bore in the boring bar 2, to center said end during operation.

The slide member 6 has an inclined surface l cooperating in a manner described hereinafter 5 with a thrust pin I2 iixed in the pivotable part 2 near its end. The part 2 is pivoted in the part I by means of a universal joint comprising pivot pins I3, I5 and an elastic ring Ill, the part 2 being jointed to the ring I4 by the pivot pin I3, and 10 the ring I ll jointed to the part I by the pivot pin I5. The pivot pin I5 traverses a bore in the ring I4 which is large enough to permit limited axial movement of the part I relatively to the nonpivoting part l.

If after completion of the boring operation carried out'by the tools 9 and I0 the boring bar l, 2 is withdrawn from the centering abutment II, the spring 8 will cause displacement of the slide member .Ii relatively to the part 2 and the 2O thrust pin I2 will co-operate with the inclined surface 'I to lower the left hand end of the part 2. Consequently, the part 2 will be swung about the shaft I3 of the joint M, I5 connecting the driving part I with the pivotable part k2, 25 this movement being possible owing to the flattened point of the conical end sliding on the flat end of the member 6 in such a way that the. tools 9 and I0 will be retracted from the working surfaces and the boring bar I, 2 can be with- 30 drawn from the bore without being damaged.

The elasticity of the ring also prevents transmission of vibration from the drive to the tool.

In the construction shown the attachment of the boring bar to the spindle of the drilling ma- 35 chine is: particularly simplied by providing a sleeve IG carrying the center 3, with a Morse taper on its outer face I'I. To obtain vibrationless driving of the spindle it is advisable to arrange the center 3 within the bearing I8 of the drive.

The operation of the present invention is as follows:

The center point of the member 3 is somewhat flattened and merely engages or abuts the end surface of the slide G in such a manner that this end can move transversely to the center 3. Upon withdrawing the center support II, the tool bar 2, under the action of the spring 8, and utilizing the axial plan of the universal joint I4, I5, is forced to the right carrying with it the thrust pin I2, while the slide 6 remains held by the spring 8 against the flat point of the center 3. The conical seat I9 at left-hand end of the tool bar 2 thus separates from the center 3 and the 55 movement; of the thrust pin I2, which is mounted with play in the Wall of the bore 5 and of which the outer end bears against the inner surface of the bushing I6, causes the slide member and with it the left-hand end ofthe tool bar to move upwardly.

From the foregoing, the importance of the universal joint I4, I5 is evident. This joint allows the tilting movement of the tool bar 2, by means of the pressure on the thrust pin I2 and the spring 8, to withdraw the cutters from the work. The tool bar obviously can move only in one Vdirection which is imposed upon it by the movement of the thrust pin I2 against the slide E. Another purpose of the universal joint isl to transmit the drive of the driving member I to the tool bar 2 without vibration and bending action.

Obviously the universal joint supports the tool bar after withdrawing of the support I I, and the tool bar tilts about the axis I3. The universal joint therefore cannot be omittedV as otherwise the tool bar would not be driven bythe driving member I, nor could it tilt about the pin I3.

I claim:-

1. A boring bar foroperation between two centers comprising a driving member, a tool carrying member having an axial bore at one end in which one of the centers engages a slide member in said bore, said slide member having an inclined side face and abutting at one end against a attened point of said center, a spring operative between the slide member and the tool carrying member, joint means connecting the tool carrying member with the driving member and enabling the tool carrying member to pivot in the driving member in any direction trans' verse to their common axis,A said joint means providing for limited axial movement between said driving and tool carrying members, and a thrust pin in the wall of said bore and cooperating with the inclined surface of the slide member to pivot the tool carrying member about the joint as a result of said limited axial movement.

2. A boring bar for operation between two centers, comprising a driving part, a tool-carrying part, means jointedly connecting said parts including a pivot pin about which the tool-carrying part can swing transversely to its axis, a slide member longitudinally displaceable in an axial bore in one end of the tool-carrying part and slidably abutting at one end against one of the centers which extends into said bore, said slide member having an inclined face, a compression spring o-perating between the tool-carrying part and the other end of said slide member, said spring being coaxial with said tool-carrying part, and a thrust pin cooperating with the inclined face of said slide member and adapted to be radially moved by axial displacement of the said slide member by said spring on retraction of the other center from the boring bar, the joint means being adapted to allow a limited axial movement of the tool-carrying part relatively to the driving part.

3. A boring bar for operation between two centers comprising a driving member, a tool carrying member having an axial bore at one end in which one of the centers engages a, slide member in said bore, said slide member having an inclined side face and abutting at one end against a attened point of said center, a spring i operative between the slide member and the tool carrying member, joint means connecting the tool carrying member with the driving member and enabling the tool carrying member to pivot in therdriving member in any direction transverse toV their common axis, said joint means providing for limited axial movement between said driving and tool carrying members, and a thrust pin in the wall of said bore and cooperating with the inclined surface of the slide member to pivot Y the tool carrying member about the joint as a result of said limited axial movement, said joint means comprisingV a universal joint having one of its parts of elastic material.

4. A boring bar for operation between two centers, comprising a driving part, a tool-carrying part, means jointedly connecting said parts including a pivot pin about which the tool-carrying part can swing transversely to its axis, a slide member Ylongitudinally displaceable in an axial bore in one end of Vthe too-l-carrying part Vand slidably abutting at one end against one of the centers which extends into said bore, said slide memberV having an inclined face, a compression spring operating between the tool-carrying partv and the other end of said slide member, said spring being coaxial with said tool-carrying part, and a thrust pin cooperating with the inclined face of said slide member and adapted to be radially moved by axial displacement of the said slide member by said spring on retraction of the other center from the boring bar, the joint means being adapted to allow a limited axial movement of the vtool-carrying part relatively to the driving part, and comprising a universal joint having one ofV its parts of elastic material. Y

FRITZ WALTHER.