SAWING MACHINE

Abstract: In a sawing chine having a saw table (6) for carrying a workpiece (7) up to a saw blade (3), the saw table carries a workpiece feeding device for moving the workpiece incrementally into abutment with a fence (4). The workpiece feeding device includes a pusher head which contracts the workpiece. After the pusher head (4) has pushed the workpiece into abutment with the fence, a clamp (8) is operated to clamp the workpiece to the saw table. When the workpiece has become clamped, the pusher head backs off so as not to exert force on the workpiece during the cutting stroke and return stroke of the saw table. A clamp for use in clamping the workpiece to the saw table has an elongated beam (39) running in the direction of movement of the saw table, and a plurality of individual thrust devices which can be adjusted along the beam. For ensuring that the workpiece is presented squarely to the fence by the pusher head, the feeding device has a table with rollers (24) to support the workpiece, the rollers being inclined to direct the workpiece towards an alignment fence (26) at one side of the table, and to facilitate the movement of the workpiece towards the alignment fence, the pusher head has rollers (35, 36) for contracting the workpiece.

Description: "SAWING MACHINE" This invention relates to a sawing machine of the kind which has a moving saw blade, and a saw table on which a workpiece is held, the saw table being movable parallel to the plane of the saw blade to carry the workpiece to the saw blade for effecting a saw cut. Where repeated cuts are to be made from a same workpiece, it is known to have a releasable clamping means on the saw table, and a feeding means on the saw table for moving the workpiece transversely with respect to the plane of the saw cut, so as to bring the workpiece into position for the next cut. After a cut has been made, the saw table is brought back to an initial position, the clamping means is temporarily released, and the feeding means is operated to shift the workpiece by the width of the next portion of workpiece to be cut off. Conveniently, the feeding means shifts the workpiece until it abuts against a fence on the saw table, whereafter the clamping means operates to hold the workpiece to the saw table. If the feeding means continues to apply pressure against the workpiece after clamping of the workpiece to the saw table, and during the run-up and return movements of the saw table, there is a risk ' of distortion of the workpiece out of its unconstrained shape, considered in the plane normal to the plane of the cut, and also a risk of so-called "back-cutting" occurring during the return movement of the saw table. It is accordingly the first object of the present invention to provide an arrangement of workpiece feeding means, for use on a saw table, whereby no, or substantially negligible, force is exerted by the feeding means on the clamped workpiece during the cutting operation and during at least sufficient return movement of the saw table to move the workpiece clear of the saw blade. A workpiece to be sawn may be of considerable length in the direction parallel to the saw cut. It is desirable to be able to clamp the workpiece at two or more positions spaced along its length, and it is desirable to be able to change those positions in a quick and simple manner, e.g. for successive different workpieces. It is also desirable that the clamping at each of those positions shall be obtained with the use of a respective clamp device rather than a single elongated clamp device especially for the reasons (i) that the workpiece may vary in height along its length, that is to say height above the saw table, and (ii) that a workpiece may have different profiles presented towards the clamping means at different positions along its length, so that the fitting of respective clamp pads of corresponding c unterprofiles then becomes useful. It is a second object of the present invention to provide a clamping means which fulfils these desiderata. According to a first aspect of the present invention a workpiece feeding arrangement, for use on a saw table of a sawing maching comprises a stop, a power-operable workpiece feeding means including an actuator and a pusher head movable by the actuator towards and away from the stop in the feed direction, and control means for the actuator which cause the pusher head to be moved towards the stop thereby to apply force on the workpiece and move it until the workpiece is butted against the stop, whereafter the pusher head ceases to apply force to the workpiece. The workpiece may thus be clamped to the wαrktable, but without being subjected to force exerted o it in the feed direction during the movement of the saw table to effect the saw cut, or during the return movement of the workpiece clear of the saw blade. In a preferred construction, the control means controls the actuator such that the pusher head backs off from the workpiece after ceasing to apply force to the workpiece. A Kinetic connection between the actuator and the pusher head may be resiliently deformable, for example for the purpose of avoiding direct and unyielding connection between the actuator and the pusher head. Advantageously, "the resistance to resilient deformation, of that kinetic connection, is made variable, for example so as to permit adaption of the pusing force of the pusher head to the inherent strength of different workpiece materials. Where such a*resiliently deformable connection is provided, the control means may include a limit control adapted to operated, by continuing movement of the actuator in the feed direction after the workpiece has become butted against the stop, to cause the pusher head to cease to apply force to the workpiece. For example, the actuator may be a fluid-operable ram coupled to the pusher head, the arrangement being such that during the feed movement fluid under relatively greater pressure is applied to o-ne chamber of the ram cylinder than to the other chamber thereof, whereas after operation of the limit control the pressure in both of the chambers of the ram is equalized. Where the feeding arrangement is operated in association with a workpiece clamping means, the limit control may serve to cause firstly actuation of the clamping means and thereafter cause the pusher head to cease to apply force to the workpiece. According to a second aspect of the present invention, a clamping means for clamping a workpiece to a saw table comprises a carrier for securing on the structure of a sawing machine at a spacing from a saw table of the machine, the carrier being elongated in the direction of movement of the saw table relative to a saw • blade of the machine,, and a plurality of extensible and retractable thrust devices mounted on the carrier and individually- movable along the carrier in the direction of its elongation, the thrust devices projecting from the carrier such that, when the clamping means is in use, they extend towards the saw table. The carrier may be a beam having opposed walls, the thrust devices being disposed between the walls and being secured at one end to one such wall and extending through the other such wall. In a preferred arrangement, the thrust devices are coupled to a common clamping member elongated in * the direction of elongation of the carrier. Resiliently deformable loading means may be disposed to act between the thrust devices and the common clamping member. In a preferred construction, the thrust devices each include a thrust pad, and resilient loading means are disposed to act between the thrust pad and the common clamping member. Advantageously the clamping means includes means for mounting the carrier adjustably on the structure of a sawing machine at any desired one of a number of predetermined spacings from a saw table. Such mounting means may comprise, for example, a plurality of lugs for securing on the sawing maching structure, and a ' SmlE OMPI corresponding plurality of apertures on the carrier each receiving a respective lug, the apertures having portions stepped at different positions in the direction towards and away from- the saw table, whereby the lugs can each be engaged into the corresponding stepped portion of its aperture for pre-setting of the carrier. Preferably, the extent of movement between each adjacent pair of stepped portions is less than the stroke of the thrust devices. There may be provided, in combination with the workpiece feeding arrangements, a workpiece support comprising a plurality of rotatable members on which the workpiece rests during its movement of feeding towards the stop, said members having their respective axes of rotation " inclined to the normal to the-direction of movement of the pusher head, and an aligning stop means disposed laterally of the rotatable members and having its stop surface normal to the line of cut of the saw blade. With such an arrangement, actuation of the pusher head causes movement of the workpiece along the rollers, and the rotation of the rollers tends to move the workpiece into proper alignment with and abutment against the aligning stop means. Such operation requires relative movement of the workpiece with respect to the pusher head, normal to the direction of movement of the pusher head, and to facilitate that movement the pusher head may comprise roller means for abutting the workpiece, said roller means having their axis normal to the direction of movement of the workpiece towards the alignment stop. Preferred embodiments of the present invention are hereinafter particularly described with reference to the accompanying drawings, wherein:- Fig. 1 is a plan view of an attachment to a sawing machine, together with parts of the sawing machine, Fig. 2 is a fragmentary section taken along the plane II-II of Fig. 1; . Fig. 3 is a perspective view, on an enlarged scale, of a pusher head forming part of the saw attachment of Fig. 1; Figs. 4 and 5 are fragmentary views, respectively in elevation and in part-section and part-elevation, of the pusher head of Fig. 3; Fig. 6 is a schematic front elevation of a workpiece clamping mechanism; Fig. 7 is an end elevation of the clamping mechanism shown in Fig. 6; Fig. 8 is a part-elevational part-sectional view taken along the plane VIII-VIII in Fig. 6. Fig. 9 is an elevation viewed in the direction shown by the arrow "A" in fig. 1; Fig. 10 is a longitudinal central vertical section, to a larger scale, of part of the workpiece feed mechanism; Fig. 11 is an end elevation viewed in the direction shown by the arrow "B" in fig. 1. Referring first to Figs. 1 and 2 of the accompanying drawings, there is shown an attachment 1 for a sawing machine having a housing 2 containing an electric motor (not shown) for driving a rotary saw blade 3 which is stationarily i.e. positionally fixed. A workpiece fence 4 is fixed on the machine. The fence 4 is adjustable in position, normal to the plane of the saw cut, by means of a known rack and pinion device, for enabling the position of the fence 4 to be adjusted with great accuracy so as to maintain parallelism between the fence 4 and the plane of the saw c-ut. The front or work-engaging face of the fence 4 is provided with a recess 4a_ where it runs behind the saw blade, thereby to provide a small clearance 4b_ which will serve to prevent material from jamming between the saw blade 3 and the fence 4. The fence 4 also carries an adjustable and clarapable support 5 to help prevent sag of larger pieces of material not supported elsewhere. A saw table 6 is reciprocable towards and away from the saw blade 3, i.e. along the plane of the saw blade for carrying a workpiece (shown in chain-dotted lines at 7) towards and away from the rotary blade 3. The attachment 1 further includes a clamp unit 8 ' mounted on the saw table 6 and described in greater detail below with reference to Figs. 6 to 8. The saw table 6 is normally part of a pre-existing machine but is modified by the pro-vision of the clamp unit 8 thereon. The attachment 1 also includes a feed carriage 9 secured in releasable manner to the saw table 6 so as to move therewith, and a pusher head which is relatively movable for shifting the workpiece 7 transversely, i.e. normal to the plane of the saw blade 3. The reciprocable saw table 6 carries the clamp unit 8 -and in this embodiment the reciprocating movement is effected by a pneumatic cable cylinder 10 which, in known manner, has a pair of pulleys 11 around which a cable 12 is strained.. The cable 12 is fixed at 13 to the saw table 6. The cylinder 10 carries adjustably positioned limit switches for determining the length of movement. The feed carriage 9 will now be described in greater detail. The carriage 9 is provided with a pneumatic cable cylinder 15 similar to the cylinder 10 having a cable 16 secured to a bracket 17 to which is secured one of two essentially H-shaped frame members 18, 19 together constituting a feeding ram having a push head 20 to be described below with reference to Figs. 3 to 5. A coil spring 21 connects the frame members 18, 19 together to allow relative movement therebetween. The tension of the spring 21 is adjustable by means of a knob 22 to cater for greater or less strengths of workpieces. The frame members 18, 19 are adapted to move relatively to the table of the feed carriage 9 in rails and channels which are not shown in detail. At the back of the feed carriage 9 a backstop limit switch 9b_ is provided. Part of frame member 18 is adapted during forward travel to abut and actuate a limit switch 9a_ positionally adjustably mounted on the casing of the cable cylinder to stop forward feed movement. The top surface of the feed carriage 9 is provided on each side of the feed cylinder with a series of freely rotatable rollers 24 the axes of rotation of which are mutually parallel but slightly inclined to the perpendicular drawn to the direction of pushing movement. As may be seen in Fig. 2, the rollers 24 project by a slight clearance 24a. above the surface of the feed carriage 9. Fig. 2 also shows that the movable portion of the feed carriage 9 is supported by rollers 25 mounted on the reciprocating saw table 6. In this way, a panel or board workpiece 7 laid on the rollers 24 will tend to slide towards the left-hand edge of the feed carriage 9. At that edge, however, an alignment fence 26 is rigidly secured to the feed carriage 9 so as to provide lateral support and alignment to the workpiece 7 being cut. The alignment fence 26 extends perpendicularly to the plane of the cut (the plane in which the saw blade 3 rotates) OMPI and in parallel with the movement of the workpiece 7 towards that plane. The carriage frame member 18 carries the limit switch 9a_ and a pivoted roller 28. When the pusher head 20 has pushed the* workpiece 7 into abutment with the fence 4 and is thus stopped, the frame member 18 continues its forward travel under the influence of the cylinder 15 and against the bias of the spring 21, until the roller 28 abuts against a surface 29 of a frame member 19. As the roller 28 pivots, it actuates the limit switch 9a which in turn causes actuation of the clamp unit 8 and causes a clamp channel member 31 (see fig. 8) to descend and clamp the workpiece 7 whereupon the saw tabXe 6 begins its travel towards the rotary saw blade 3. As soon as the workpiece 7 is clamped, air under pressure enters the exhaust side of the cylinder 15, and serves to equalise the pressure on each side of the piston in the cylinder 15, causing it to stop and reverse through a small distance. The pusher head 20 is thus caused to "back-off". As a result of this, there is no continued forward feed pressure on the workpiece 7 during sawing or during the return stroke of the saw table 6 so that any possibility of "back-cutting" on the return movement of the saw table 6, which would be undesirable and potentially damaging to the saw blade 3, is reliably avoided. Although the pusher head 20 retracts or backs off, the workpiece 7 remains firmly clamped by the clamp unit 8. It will be appreciated from the description given so far herein that the saw blade 3 is fixed in position, i.e. does not move, and that the pusher head 20 moves towards the blade 3, with the fence 4 being on the side of the cutting plane opposite to that of the direction of forward feed of the pusher head. In this way, it is ensured that the saw blade 3 (or the cutting plane) remains parallel to the fence 4 and great precision is achieved thereby. On operating a main push-button switch (not shown) , the cycle begins*, namely the correctly-sequenced operations of. forward feed by the pusher head, clamping, backing off, feeding of the saw table 6 to cut, return of the saw table 6, and so on. When there is no longer a sufficient length of workpiece 7 to be cut, i.e. the length of the piece of wood between the fence 4 and the position of the clamp unit 8 is insufficient, a microswitch is actuated and the carriage frame members 18, 19 are moved back to their fully retracted position. Referring now to Figs. 3 to 5, it will be seen that the push head 20 comprises a C-section metal member 32 secured to the frame member 19 and open towards the direction of pushing movement. The free ends of the limbs 33, 34 of the £ are spanned by four coaxial rollers, mounted for free rotation about a vertical axis of which the two outer rollers are designated by 35 and the two inner- rollers are designated 36. The bottom lim 33 of the C-shaped member 32 is cut away to form a central recess 37 into which the two inner rollers 36 project. A portion of the base of the £ is struck inwardly to form a flange 38 spacedly overlying the recess 37. The two inner rollers 36 are arranged as respective lower and upper roller pairs 36a_ and 36b_. In each pair, the lower end of the upper roller 36b_ terminates adjacent the flange 38 and the lower roller 36a_ is suspended below the flange 38. The cylindrical surfaces of 'the rollers 35, 36 project forwardly of the ends of the limbs 33, 34 and of the flange 38. The bo ' ttom end surfaces of the rollers 36<a are coplanar with the bottom surface of the limb 33 of the C-shaped member 32. When in use this push head 20 engages the rear edge of a board or panel workpiece 7 to be cut, and the freely rotatable rollers 34, 35 will turn as necessary to ensure that the panel or board is pushed "squarely" forward. The two outer rollers 35 will prevent any projecting portion of a panel from entering into the gap between the upper and lower sections of the inner rollers 36 and the fact that the latter are in two portions ensures that workpieces thinner than the thickness of the bottom limb 33 are also aligned accurately. The clamp unit 8 shown in Figs. 6 to 8 will now be described in greater detail. It essentially comprises a carrier beam 39 formed from a pair of channel members 40, 41, carrying between them a plurality, e.g. three, of pneumatic thrust or clamp cylinders 42. The height of the clamp beam 39 in relation to the saw table 6 may be adjusted by means of a pair of "reverse-E" shaped slots 43 in which lugs 44 mounted on quick-release locking handles 45 are engaged. The distance between adjacent locating portions of the slots 43 is less than the stroke of the cylinders 42. In this way, by operating the quick-release handles 45 the clamp beam 39 may be moved vertically with respect to the structure of the machine. Fig. 6 shows flexible pneumatic input and output lines 46 to the cylinders 42, and a pipe support cable 47. Fig. 7 shows in clearer detail the supports 48 on which the beam 39 is mounted on the machine structure. It also shows spacers 49 for keeping the channel members 40, 41 apart. An important feature is that the clamp cylinders 42 may be positioned at any desired position along the length of the beam 39 in a manner now to be described. Each cylinder 42 is of cylindrical shape provided with end caps 50 connected by tie rods (not shown) to give, overall, a rectangular contour. A piston rod 51 extends downwardly from each cylinder 42, and a spigot 52 projects upwardly from the end cap 50. A clamp nut 53, which is readily releasable, clamps a generally C-section angle member 54 to the top of the cylinder so as to sandwich the inwardly facing flanges 55 of the channel members 40, 41. The angle member 54 forms part of a structure that includes inlet and outlet pipes to the cylinders 42 and a coupling clamp 57 within a housing 58. To release, re-position and re-secure a cylinder 42 at any desired position along the beam 39, all that is necessary is to release the clamp nut 53 to free the cylinder, move it along and re-tighten the nut. In this way, operation of the cylinders produces no deformation forces on the whole of the beam 39 but only on portions thereof adjacent to the cylinders, the lower free ends 59 of the channel members 40, 41, being free to be displaced in the space between the lower end cap 50 and a cup 60 secured around the the piston rod 51. The work is engaged by the common clamp channel 31 in which is mounted a clamp pad 61 secured to the end of the piston rod 51 by a lock nut. In order to allow for possible unequal pushing pressure and retraction of the clamping cylinders, a plurality of balls 62 biassed by springs 63 are disposed in bores 64 in the clamp pad 61 f OMPI so that the force of the piston is transmitted to the clamp channel member 31 by way of the sprung balls 62. The operation is as follows: Once the- pusher head 20 of the feed carriage 9 has pushed the workpiece 7 against the fence 4, air under pressure is passed to the clamping cylinders 42 of the clamp unit 8, causing them to extend and clamp the workpiece. Pressure is then equalised on each side of the piston in the feeding ram cylinder, causing the pusher head 20 to "back off. Air under pressure is then fed to the cylinder 10 of the saw table 6, to cause the « table to move and carry the workpiece 7 to the saw blade 3. The length of the cutting stroke may be determined by a- limit switch, whereafter cylinder 10 reverses its direction of movement. When the cylinder 10 has returned t to " its start position, clamping cylinders 42 are retracted to unclamp the workpiece 7. - This sequence can then be continued until all material has been cut.

Claims: CLAIMS .1. A workpiece feeding arrangement, for use on a saw table of a sawing machine, comprising a stop, a power-operable workpiece feeding means including an actuator and a * pusher head movable by the actuator towards and away from the stop in the feed direction, an control means for the actuator which cause the pusher head to be moved towards the stop thereby to apply force on the workpiece and move it until the workpiece is butted against the stop, whereafter the pusher head -"ceases to apply force to the workpiece. 2. A workpiece feeding arrangement, as claimed in clai 1, wherein the control means controls the actuator such . that the -pusher head backs off from the workpiece a ter ceasing to apply force to the workpiece. -3. A workpiece, feeding arrangement, as claimed in claim 1, wherein a kinetic connection between the actuator and the pusher head*is resiliently deformable. 4. A workpiece feeding arrangement, as claimed in claim 3, wherein the control means include a limit control adapted to be operated, by continuing movement of the actuator in the feed direction after the workpiece has become butted against the stop, to cause the pusher <<* ^_ head to cease to apply force to the workpiece. 5. A workpiece feeding arrangement, as claimed in claim ' 4, wherein the actuator is a fluid-operable ram coupled to the pusher head, and wherein during the feed movement fluid under relatively greater pressure is applied to on chamber of the ram cylinder than to the other chamber thereof, whereas after operation of the limit control th pressure in both of the chambers of the ram is equalized. 6. A workpiece feeding arrangement, .s claimed in clai 5, in combination with a workpiece clamping means, said limit control serving to firstly cause actuation of said clamping means and thereafter to cause the pusher head t cease to apply force to the workpiece. 7. A clamping means, for clamping a workpiece to a saw table, comprising a carrier for securing on the structur of a sawing machine at a spacing from a saw table of the ^machine, the carrier being elongated in the direction of movement of the saw table relative to a saw blade of the machine, and a plurality of. extensible and retractable thrust devices mounted on the carrier and individually movable along the carrier in the direction of its elongation, the thrust devices projecting from the carrier such that, when the clamping means is in use, _they extend towards the saw table. ;S. A clamping means, as claimed in claim 7, wherein th carrier is a beam having opposed walls, the thrust devices being disposed between the walls and secured at one end to one such wall and extending through the other such wall. 9. A clamping means , as claimed in claim 7 , wherein th * thrust devices are coupled to a common clamping member elongated in the direction of elongation of the carrier. 10. A clamping means, as claimed in claims 7, including means for mounting the carrier adjustably on the structure of a sawing machine at any desired one of a number of predetermined spacings from a saw table. 11. In combination, a workpiece feeding arrangement as claimed in claim 1 or 7, and a workpiece support icomprising a plurality of rotatable members on which the workpiece rests during its movement of feeding towards the stop, said members having " their respective axes of rotation inclined to the normal to the direction of »movement of the pusher head, and an aligning stop means ' disposed laterally of the rotatable members and having its stop surface normal to the line of cut of the saw blade. 12. The combination of claim 11 wherein the pusher head comprises roller means for abutting the workpiece, said roller means having their axis normal to the direction of novement of the workpiece towards the alignment stop. OMPI

Inventors: JOHNSON D
Applicants: DUALCLASS LTD, JOHNSON D
Application year: 1981
Main classification: B27B5
IPC codes: B27B5, B27B27, B27B31