This invention relates to a method and an apparatus for the machining, especially boring, of machine parts, for example of forestry machines, power shovels etc.

In the case of damages occurring on forestry machines, power shovels etc. it is, of course, desired to be able to repair these damages in situ, in order not to have to transport the machine or parts thereof, for example to a. repair shop. Besides, when the repair can be carried out in situ, the. downtime normally can be reduced.

When, for example, on crane ibs, power shovel jibs and on hinges/bearing seats of other kind damages have occurr¬ ed which are of the type requiring boring operation, it was heretofore necessary to dismantle the damaged machine part and _. trnasport it to a repair shop for machin¬ ing. Aside from the fact that the dismantling work proper of the damaged machine part can be extremely troublesome and time-consuming, also the transport to and from the repair shop can require much time, especially when the damage has occurred in a rugged area. There may also be waiting times in the repair shop when it is highly occup¬ ied just when the damaged machine part is in need of repair

It should be pointed out, too, that boring machines norm¬ ally are available only in ^* workshops equipped with relat¬ ively extensive machinery. This may imply that the damaged machine part must be transported through a still greater distance.

The boring apparatus according to the invention, in addit¬ ion to being intended for use out of doors in the field, also opens the possibility to small workshops to procure boring equipment and thereby to broaden their offering of workshop services.

The present invention has the object of providing a method

and an apparatus to be used primarily for carrying out boring operation out of doors in the field on damaged machine parts, for example o,f forestry machines and power shovels. A further object of the boring apparatus accord¬ ing to the invention is its stationary employment in small workshops. Nothing objects, however, to using the same equipment both in a mobile and in a stationary manner.

The ohject of the invention is realized in that the method and apparatus according to the invention have been given the characterizing features defined in the attached claims .

An embodiment of the invention is described in the follow¬ ing, with reference to the accompanying drawings, in which Fig. 1 is a lateral view of a boring apparatus according to the present invention, Fig. 2 shows how parts of the boring apparatus are mounted on a crane jib -in correct position for machining the. crane jib, Fig. 3 shows parts of the borir.g apparatus attached temporarily on the crane jib, Fig. 4 shows the boring apparatus in operation, and Fig. 5 is a section through a centering device at the boring apparatus .

The mobile boring apparatus shown in Fig. 1 comprises a column 1, wgich carries two guide plates 2.

The column 1 includes a longitu inal groove 3 (see Fig. 2), which is intended to receive a key 4 (see Fig. 2) at each of the guide plates 2.

Upon movement of the guide plates 2 along the column 1, .the groove 3 and key 4 co-operate in such a manner, that the guide plate 2 does not rotate relative to the column 1.

When the guide plates 2 are to be fixed in longitudinal direction of the column 1, the tension screw 5 is tight¬ ened. The column 1 further carries a spindle housing 6, which is

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provided with a key 7 for co-operation with the groove 3 of the column 1. The fixing of the spindle housing 6 in longitudinal direction of the column 1 is effected by means of tension screws 8.

The spindle housing carries a spindle axle 9, which is mounted rotatably in the spindle housing 6. The spindle axle 9.is coupled together with a boring machine 13 via a gearbox 10,a.-jniter gear 11 and a rubber cross-connect¬ ion 12.

In the spindle housing 6, furthermore, a guide column l4a and a feed screw 14b (concealed in Fig. 1, see Fig. 4) are provided, which can be driven manually via a crank wheel 15 or automatically from the boring machine 13 via the gearbox 10.

At the machining of through holes on a crane jib, the mode of operation, for example, is as described below, where reference is made to Figs; 2-4.

As appears from Fig. 2, on the remote sides of the guide • plates 2 centering devices 16 are attached which are fixed relative to the guide plates 2 by means of a bolt 17 with a handle which is received in a threaded hole in the guide ^' plates 2. In order to ensure that the centering devices 15 do not rotate, about the bolt 17, the devices preferably are provided with guide pins 18, which are received in depressions in the guide plates 2 corresponding to the pins 18.

On each guide plate 2, furthermore, so-called welding discs 19 are attached which include eccentrically located -threaded holes 20.

The welding discs 19 are fixed on the guide plates 2 by means of bolts 21, which pass through holes in the guide plates 2 and engage with the threaded holes 20 of the welding discs 19.

When the centering devices iβ and welding discs are fixed on the guide plates 2, the column 1 with guide plates is

mounted on the object to be machined, at this embodiment a crane jib 22. In this. hase the spindle housing 6 has been removed from the column 1.

At the mounting of the column 1 with the guide plates 2 on the crane jib 22, the guide plates 2 are moved along the column 1, whereby the expanding pins 23 of the centering devices Iβ are inserted into through holes 24 on the crane jib 22. The guide plates 2 are thereafter fixed against movement along the column 1 by tightening the tension screws 5-

By tightening the wing nut 25, the expanding pins 23 are moved in radial direction so as to a±αrt the periphery of the hole 24.

In Fig. 5 the centering device Iβ is shown in greater - detail. It appears from this Figure that upon rotation of the wing nut 25 in such a direction that the screw 26 is moved into the centering device 16, a plunger 27 is moved downwards in Fig. 5, whereby the expanding pins 23 are pivoted outward in radial direction by rotation about their attachment points 28. An 0-ring 29 encloses the expanding pins 23 and applies to them a returning force when they are pivoted outward from the position shown .in Fig. 5.

In connection with the anchoring of the centering devices lβ in the holes 24 on the crane jib 22, it is to be ob¬ served t.hat the welding discs 19 abut the crane jib 22 with a certain overlapping. If this is not the case, the bolts 21 are to be loosened and the welding discs 19 be turned. Thereafter the centering devices Iβ can be anch¬ ored in the holes 24 by tightening the wing nut 25-

As indicated in Fig. 2, the welding discs 19 are connect¬ ed to ^he crane jib 22 by welding. When all four welding discs 19 are secured by welding on the crane jib 22, the guide elates 2 and column 1 are fixed in position relative to .the crane jib 22.

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The internally threaded holes 20 of the welding discs are located eccentrically in the welding discs 19. It is here¬ by achieved that the discs have a greater "reach" than they would have if the holes were located centrally.

After the welding discs 19 have been connected to the crane jib 22 by welds 30, the centering devices l ^β are removed, see Fig. 3, in that the expanding pins 23 are returned to the position according to Fig. 5 , and the engagement of the handle bolt 17 with the guide plate 2 is abolished.

At the phase shown in Fig. 3, the column, thus, has been positioned in a direction which is in parallel with a line through the centres of the holes 24. The aligning, thus, is completed and the boring operation can be comm¬ enced. As appears from Fig. 3 _. the spindle housing 6 can be pushed on the column 1 from any side, and in addition the advantage is gained that in the case when boring is -carried out from two diametrically opposed directions, the machining tool all the time will have its centre along the same straight line.

In Fig. 4 is shown how the spindle housing 6 is pushed onto the column 1 from one side thereof. Thereby the key 7j t>y co-operation with the groove 3 _} ensures that the spindle housing 6 is given correct position relative to the workpiece, i.e. the crane jib 22.

When the spindle housing has been pushed onto the -column 1 through a suitable distance, the spindle housing 6 is fixed in longitudinal direction of the column 1 by tighten¬ ing the tension screws 8.

On the spindle axle 9 a suitable machining tool 31, for example a cutting bit, is attached.

By starting the boring machine 13, the machining tool 31 and the spindle axle 9 will be rotated via the cross connection 12, miter 11 and gearbox 10.The feed of the machining tool is effected by rotation of the feed screw l4b. The feed, thus, can take place manually or automat- _

ically via the gearbox 10. It is possible in this way to machine the holes 24 with, for example, one bore.

When the machining tool 31 does not extend all the way to the left-hand hole 24 in Fig. 4, the spindle housing β, thus, can be pushed onto the column 1 from its opposed end. The rotation centre of the machining tool 31, how¬ ever, will be located along the same line as at the pos¬ ition according to Fig. 4.

When the machining of the workpiece is completed, the spindle housing 6 is removed from the column 1 in that the tension screws 8 are loosened and the spindle housing ^β is drawn off from the column 1.

For dismantling also the column with guide plates 2 and welding discs 19 from the crane jib 22, the weld joint between the crane jib 22 and the welding discs 19 must be removed. This is most simply carried out, for example, by knocking off the welds 0 with a hammer.

The boring operation thereby is completed and the crane jib 22 is repaired.

It is, thus, possible by the method described above to carry out in situ relatively qualified machining of heavy machine parts, which otherwise had to be transported to a workshop.

What is required in addition to the equipment shown, is a welding unit and- a power source for driving the bore machine 13•

When the apparatus according to the invention is to be used stationary, one end of the column 1 can be retained in a stand or the like.

The invention is not restricted to the embodiment set farth above, but can freely be varied within the scope of the attached claims.