This invention relates to machine tools and, in particular but not exclusively to woodworking machine tools such as planer/thicknessers.

In machine tools generally and in planer/thicknessers in particular, adjustment of the depth of working of a workpiece by the work tool of the machine is conventionally achieved either by movement of the work tool towards and away from the v/orkpiece or by movement of the workpiece bodily (with any carriage on which the workpiece is mounted) towards and away from the work tool. With planer/thicknnessers, a two-part bed is conventionally used one part leading and the other trailing relative to the work tool in the direction of feed of the v/orkpiece past the work tool, both parts needing to be adjusted dependent upon the depth of cut being made in the workpiece and the initial thickness of the workpiece. All such constructions require a relatively complicated (and, therefore, expensive) mechanism manufactured to a high degree of accuracy.

The present invention provides a relatively simple (and, therefore, cheap) way of adjusting the depth of the working of the workpiece and of accommodating varying thicknesses of workpieces.

Accordingly, the present invention provides a machine tool comprising a work tool mounted at a predetermined station and a bed over which a workpiece can be fed past the work tool in a defined direction to effect working of the workpiece by the work tool, the bed being mounted relative to the station for pivotal movement about an axis which is remote from the station

and which extends transversely to said direction to effect feed of the workpiece towards and away from the work tool thereby to determine the depth of working carried out on the workpiece by the work tool.

The machine tool may be a woodworking machine and, in particular, may be a planer/thicknesser of which the work tool is a cutter block having cutting blades projecting radially outwardly from the cutter block from an axis about which the block is rotatable, the axis of rotation of the cutter block extending transversely of the direction on which a workpiece can be fed past the work tool.

There may be provided a v/orkpiece carriage to-which a workpiece can be secured, means being provided on both the carriage and the bed by which movement of the carriage is restrained to restrain movement of a workpiece secured to the carriage to the defined direction. The means provided on the bed may be recesses one in each of the sides of the bed extending longitudinally of the bed in said direction and the means provided on the carriage may then be flanges one of each of which locates in the corresponding recess. The carriage may be provided with securing means by which the workpiece can be secured to the carriage. For relatively soft workpieces (e.g. for wood), the securing means may comprise end clamps at least one of which is slidably mounted on the carriage for movement relative thereto in the direction in which the workpiece can be fed past the work tool. In this case, the end clamps may each have a plurality of projections each extending in said direction and each having a sharp termination at its free end which, upon the end clamps being pushed one towards the other, are caused

to penetrate into the workpiece and thereby secure the workpiece to the carriage. The projections may each comprise a pin terminating at its free end in a point or a blade terminating at its free end in a knife-edge, the blades each being orientated relative to the workpiece such that its knife-edge extends in the direction of the longer of the dimensions of the cross-section of the workpiece. In any case, the securing means may be adjustable in a direction towards and away from the carriage.

If desired, the work tool can be mounted for movement at the station relative to a workpiece fed past the work tool.

Jacking means may be provided by which the pivotal position of the bed about its axis can be adjusted to be secured in that position. These jacking means may comprise either a screw rotatable by a manually-adjustable hand wheel or they may be hydraulically operated.

In one form, the axis about which the bed is pivotable is adjustable in the plane in which the bed is pivotable in a direction to move a v/orkpiece towards and away from the work tool.

There may be provided a fence against which a workpiece mounted on edge for feeding past the work tool can be retained at a pre-determined angle in its edge-mounted position. The fence may be mounted on the carriage, on the bed or at the work station.

Resiliently-loaded rollers or bars may be mounted on the same side of the direction of feed of the workpiece

past the work tool as is the work tool so that the workpiece is restrained against movement in a direction towards the work tool.

Embodiments of the present invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings of which:-

Fig. 1 shov/s a diagrammatic side view of the machine tool.

Fig. 2 shov/s a diagrammatic perspective view of the workpiece carriage.

Fig. 3 shows alternative shapes of the projections of the end clamps of the v/orkpiece securing means, and

Fig. 4 shows extension pieces for the end clamps.

The drav/ings illustrate a woodworking planer/thicknesser although it is to be understood that the invention is equally applicable to other woodworking machines such as routers,spindle moulders or circular saws and, indeed, to machine tools for v/orking other materials such as metal or synthetic plastics.

Referring to the drawings, the planer/thicknesser comprises a stand 1 v/hich may be adapted for bench-mounting or for floor-mounting. Mounted relative to the stand 1 at a work station 2 is a work tool 3 which, as is conventional in a planer/thicknesser, comprises a powered cutter block 4 rotatable about its longitudinal axis 5 having cutting blades 6 which project from the cutter block 4 radially outwardly from

the rotation axis 5. Thus, when the cutter block 3 is rotated in the clockwise direction of arrow A and a workpiece is fed past the cutter block 3, the blades 6 Will cut material from the top surface of the workpiece.

As so far described, the planer/thicknesser is of conventional construction.

The stand 1 has secured to it at the left-hand end as viewed in Fig. 1, a pair of hinge brackets 10 of which one only can be seen in Fig. 1. The hinge brackets 10 serve to locate a pivot pin 11 which passes through the left-hand end of a bed 12 of the machine tool. Thus, the bed 12 is pivotable on the stand 1 about the axis 13 defined by the pivot pin 11.

Towards the right-hand end of the machine tool as viewed in Fig. 1, is a screw-jack 14 of which the screw 15 is pivotally secured to the bed 12 at 16 and the nut 17 is pivotally secured to the stand 1 and 18. Relative rotation of the screw 15 and the nut 17 is effected by a handwheel 19. From this arrangement, it will be clear that the bed 12 can be pivotted about the axis 13 by rotation of the handwheel 19 in the direction of arrow B.

The bed 12 may be of any suitable construction which affords the bed 12 sufficient rigidity to withstand the operational forces which will be generated on it. It may, for example, be of a box construction stiffened internally as necessary by reinforcing members. Alternatively, the bed 12 may be constructed from a channel-shaped girder or space frame.

The bed 12 has slidable on it in the direction of arrow C a carriage 20 the construction of which is shov/n in more detail in Fig. 2.

The bed 12 has, along its top edges, recesses 21 engaged by flanges 22 dependent from the carriage 20. By this flange/recess configuration, the carriage 20 is restrained for movement on the bed 12 only in the direction of arrow C.

The carriage 20 is provided with means for securing a workpiece (23 in Fig. 1) to the carriage 20. These means are a pair of end clamps 24. The end clamps 24 are each slidable longitudinally of the carriage 20 in the direction of arrow C in a channel 25 provided in- the carriage 20. The end clamps 24 have, extending in a direction tov/ards each other, a plurality of projections 26 each having a sharp termination at their free ends.

The projections 26, alternative forms of v/hich are shown in Fig. 3, may be pin-shaped as shown in the middle row of Fig. 3 or may be blade-like as shown in the upper and lower rows of Fig. 3 each terminating in a knife-edge. As shov/n in the top row of Fig. 3, the blades may be a series of discrete small blades or may be a single blade extending the v/idth of the end clamps 24. In the preferred embodiment, the discrete blades are used each being about 1/16" long and projecting out of the face of the end clamp 24 a distance of about 1/4".

The workpiece 23 is secured to the carriage 20 by laying it on the upper surface 27 of the carriage 20 and then moving the end clamps 24 so that their

projections 26 drive into the end faces of the v/orkpiece. Given that the v/orkpiece is substantially planar in shape and that it is laid on the carriage 20 with one of its major surfaces adjacent the upper surface 27 of the carriage 20 and that the projections are in the form of blades, it will be seen that the blades will extend in the longer direction of the cross-section of the v/orkpiece 23. When so positioned, the end clamps 24 are then locked to the carriage 20.

Returning now to Fig. 1, the woodworking planer/thicknesser is operated as follo s:-

Fro the above description, it v/ill be appreciated that the workpiece can manually be fed under and past the cutter block 3 being restrained for movement in the direction of arrow C. By adjustment of the screw-jack 14, the bed 12 v/ill be pivotted about the axis 13 so that the region of the bed 12 adjacent the work station 2 will be moved in the direction of arrow D towards and away from the cutter block 3. Thus, by suitable adjustment of the screw-jack 14, the position of the workpiece 23 relative to the cutter block 3 can be adjusted both to engage the blades 6 of the cutter block 3 with the workpiece 23 and to determine the depth of the cut made in the v/orkpiece by the blades 6.

It v/ill be seen from the above description that the present invention, by the pivot 11 and the jack-screw 1 , provides a particularly simple mechanism requiring few precision-made parts to effect precise control of the machining of the workpiece 23.

As so far described, the planer/thicknesser has been described for machining the major surfaces of a planar

v/orkpiece. Should it be required to plane the edges of such a workpiece, it will be necessary for the workpiece to be mounted upright on one of its edges on the carriage 20. To effect this, there may be provided a suitable adjustable fence removably mounted on the carriage, the bed 12 or the stand 1 against which the workpiece can be secured. For so securing the workpiece, there may be provided one or other of the accessories shov/n in Fig. 4.

Considering, first, the accessory30 shown on the left-hand side of Fig. 4, this accessory comprises a block 31 having on its lower face 32 protuberances 33 v/hich are designed to lock into recesses 34 (Fig. 2) in the top surfaces 35 of the end clamps 24. When so locked, it will be seen that blades 36 on the face of the accessory 30 v/ill extend in the direction of the longer dimension of the cross-section of the v/orkpiece 23 when it is mounted on one of its edges on the carriage 20. Whilst, in Fig. 4, the blades 36 are shown as continuous, this may (and, preferably, would) be comprised by a series of discrete blades or pins such as is shown in the upper and middle rows of Fig. 3.

The accessory 30 has, in its upper face 37, recesses 38 similar to recesses 34 in the end clamps 24. Thus a series of such accessories 30 can be mounted one on top of the other to provide a sufficient height of clamping of the workpiece as to ensure its safe securing to the carriage 20.

The accessory 40 of Fig. 4 is for the same purpose as that of accessory 30 but, in this case, the accessory 40 is designed for height adjustability relative to the

end clamps 24. To this end, the accessory 40 has a top block 41 v/hich carries the blades 36 and dependent side pieces 42 which span -the width of the end clamps 24. Means (not shown) are provided for securing the accessories one to each of the end cStemps 24 with the top blocks 41 at an appropriate height above the carriage 20.

Whilst, in the above described embodiments, the carriage 20 with the workpiece 23 are described as being manually fed past the work tool (cutter block 3), some form of powered feed could obviously be used.

Again, the means for pivotally positioning the bed 12 about its acis 13 is shov/n as the screw-jack 14. Clearly, alternative means could be provided; for example, a hydraulic jack, a rack-and-pinion. ^' Or, the jack could be power-operated.

The guiding of the carriage 20 on the bed 12 could be by virtue of a T-slot in one of these, the slot being engaged by a complementary-shaped protrusion on the other.

in the planer/thicknesser above described, the workpiece is constrained for movement only in the direction of arrow C. In a router, spindle moulder or circular saw, provision would need to be made for movement of the workpiece also in a direction at right angles to arrow C in the same plane.

Further control of the vertical position of the workpiece could also be provided by allowing for vertical adjustment of the position of axis 13 in addition to the pivotal adjustment of the bed 12 about

axis 13.

Whilst, as above described, the end clamps 24 are each slidable longitudinally of the carriage 20, one of the clamps 24 only may be so slidable the other being fixed to the carriage.