Field of invention and prior art.

This invention relates to a milling machine and to a method of cutting a keyway in a shaft while the shaft is in a machine on site.

In machines with heavy shafts, for example steel rolling mills and paper mills, the keyways of the rolls are subject to wear and need to be renewed regularly. One can repair them by cutting them somewhat wider and then use wider keys. The keys and the milling heads are available in standard widths. Alternatively, one can add a weld seam to a keyway and then cut the keyway to the original width.

The US patent 3,466,972 shows and describes a portable milling machine which can be used on a shaft without the shaft being dismounted from a machine. The milling machine has a guideway that is to be clamped on the shaft and a cutting unit with a milling head that can be moved along the guideway. The milling head cuts the entire width of the keyway in one sweep. The transverse forces will be great and can jeopardise the precision by causing lateral movement. Therefore, the machine must be comparatively heavy and the accessibility in narrow places will be reduced.

Object of Invention and brief description of the invention.

It is an object of the invention to provide for a comparatively small machine that is low in weight and power and has a better accessibility than prior art machines but still has the same precision or even better precision than prior art machines.

This is achieved in principle by a machine that has a cutting unit that is laterally displaceable. A milling head with a diameter smaller than the keyway is used and the keyway is cut in more than one sweep. The invention is defined by the claims.

Brief description of the drawings and description of a preferred embodiment.

Figure 1 is a perspective view of a preferred embodiment of a milling machine according to the invention.

Figure 2 is a fragmentary section through a part of the machine shown in Figure 1.

Figure 3 is a fragmentary section through another part of the machine shown in Figure 1. Figure 4 is a section corresponding to Figure 2 but showing an alternative design of some elements.

In Figure 1, a shaft 11 is shown in which a keyway 12 is cut by means of a milling head 13. A guiding base 14 is clamped to the shaft by means of a clamping device that includes a chain 15 around the shaft. The base 14 has two oblique flat surfaces 16 so that it can be mounted on shafts with various diameters and always be parallel with the shaft independently of the diameter of the shaft. It has a dovetail guideway 17 and a guided base 18 is mounted on the guideway 17 to slide thereon. The guided base 18 has an upstanding circular cylinder 20 of large diameter, which is fixed to the base 18 by means of four rigid screws 21. A sleeve 22 is mounted on the cylinder 20 with a tight fit and it is fixed by being clamped to the base 18 by means of a plate 23 and a screw 24 screwed into the cylinder 20. The screw 24 and the cylinder 20 are coaxial. An outer sleeve 25 is mounted on the sleeve 22. It has a longitudinal slot and it is clamped on the inner sleeve 22 by means of four screws 28 so that it is held fix by friction forces. The sleeve 25 has two brackets 29,30 that carry a cutting unit 31 with the milling had 13. The guideway 17 has its one end bifurcated so that the milling head 13 can move between the two arms of the guideway as shown.

The cylinder 20 has a transverse slot 33 at its bottom and the base 18 has an upstanding cylinder 34 on which a control arm 35 is journaled (Fig 2). The two sleeves 22,25 have recesses at their bottoms too in order to make place for the control arm 35, and the control arm has a tight fit to the recess 36 in the outer sleeve 25 so that any turning of the arm 35 will also turn the sleeves 22,25. A control block 37 has two control screws 38,39 by which the control arm 35 can be turned into a desired precise position of turning when the screw 24 is somewhat loosened. Then, when the screw 24 is again tightened, the two sleeves 22,25 will be secured in the new position of turning.

A block 45 is fixed to the outer sleeve 25 and it has a threaded through bore for an adjusting screw 46 that extends through a hole in an extended part 48 of the plate 23 (Figs 1 and 3). The block 45 has a guide pin 47 that is slideable with a tight fit in a groove 49 in the inner sleeve 22 so that the two sleeves 22,25 are angularly in fixed position to each other. As an alternative to the pin 47, the two sleeves 22,25 can be splined together. The adjusting screw 46 can preferably be provided with a vernier scale in order to provide for fine adjustment.

For setting the depth of the milling head 13, one loosens the screws 28 somewhat so that the outer sleeve 25 can slide on the inner sleeve 22. Then, one adjusts the longitudinal position of the outer sleeve 25 on the inner sleeve 22 by turning the adjusting screw 46.

The screws 28 are then tightened to lock the two sleeves 22,25 together.

For adjusting the transverse position of the milling head 13, one loosens the screw 24 somewhat so that the two sleeves will be turnable together as a unit. Then, one adjusts the angular position of the two sleeves 22,25 by means of the two control screws 38,39 until the milling head 13 is in the desired position. Finally, the screw 24 is tightened so that the inner sleeve 22 is again clamped to the base 18 and held fixed by friction forces.

When a new keyway is to be cut in a shaft, one starts by cutting a narrow groove with a small diameter milling head. One may start from a blind predrilled bore or one may use a self drilling milling head and start drilling the bore by using the milling head. The screw 46 is used for the feeding during the drilling. (Thus, the machine can also be used for drilling holes in shafts on places otherwise difficult to access.) After the first sweep, one adjusts the transverse position of the milling head by moving the arm 35 as described while the milling head 13 is in operation and widens the groove in another sweep. Even very wide keyways can be cut in this way in a number of cutting sweeps when a small diameter milling head is used.

By cutting in two or more sweeps, the transverse forces will be comparatively small and a comparatively small machine can be used for cutting large as well as small keyways with the same high precision.

The guided base 18 can be manually fed but a power feeding can also be provided.

Suitably, a feeding device can be arranged that is powered by a frequency controlled hand drill. Any feeding device is, however, not illustrated.

The machine can be used not only for cutting keyways but also for other machining operations, for example drilling holes in a shaft and milling a flat on a shaft. Milling a flat is done in several sweeps in the same way as the cutting of a keyway.

Figure 4 corresponds to figure 2 but it shows an alternative embodiment of the device for transverse adjustment. The outer sleeve 25 and a screw 52 form a worm gear by which the two sleeves 22,25 can be turned when the screw 24 has been loosened. The machine can also be modified in other ways within the scope of the claims. The movement of the cutting unit 31 along a transverse guideway instead of the turning of the sleeves 22,25 as described can for example carry out the transverse movement of the milling head 13.