PLANING TOOL FOR A WOODWORKING MACHINE

Abstract: Worked into the surface of a head (1), uniformly distributed over the circumference, are helical grooves (2) of dovetail-shaped cross-­ section. Wedging devices (6) and knives (5) resting thereon are insert­ able sideways into the grooves (2). Disposed in each wedging device (6) is a securing means (7), through actuation of which the associated wedg­ ing device with the adjoining knife (5) is pressed against the sidewalls (17, 18), tapering outwardly of the head (1), of the respective groove (2) and held fast. Each of the knives (5) has two opposite cutting edges (19, 20), each of which can be brought into operating position by revers­ ing the knife (5). A second groove (16) runs parallel to each first groove (2). The grooves (16) serve to receive a guide component of a knife-aligning device. Owing to the helical configuration of the grooves (2) and the prec­ isely aligned cutting edges (20) of the reusable knives (5) disposed in the grooves (2), vibration-free machining of workpieces with planing widths of up to more than two meters is possible.

Description: The present invention relates to a planing tool for a woodworking machine, having a substantially cylindrical head with at least one helical groove extending from one head end to the other head end and having a bottom surface and two sidewalls, and a plurality of wedging devices and a corresponding plurality of knives disposed therein. Planing tools for woodworking machines having cylindrical heads with several grooves in their surfaces and interchangeable cutting inserts disposed therein are known and in use in conventional planing machines nowadays. In another planing tool design, bores disposed in a pattern and distributed over the entire outer surface of a cylindrical head are provided for receiving insertable cutters. In most cases, the cutting inserts are either made in one piece or consist of carriers with knives welded on and are either bothersome to resharpen or expensive to replace. Furthermore, a design of cutting inserts is known in which interchangeable knives, each provided with several cutting edges, are wedgable in the aforementioned planer-head bores by means of a wedging device. By rotating the knives, the individual cutting edges can be brought into operating position. In this last design, one knife after the other engages the machining surface of the workplace through rotation of the planing tool. Especially in the case of tools intended for a large planing width, the pulsating stress on the knives results in uneven running of the tool. This has a negative effect on the quality of the planed surfaces of workpieces in that undulating traces of planing are perceivable there. Furthermore, it is difficult and troublesome in the case of planing tools designed for large planing widths to align all the knives distributed over the head and to secure them so that they project uniformly. Poorly inserted knives bring about an inferior quality of the machined workpiece surface, as described above. The document US-A-3 785 417 discloses a rotary cutting tool for cutting material surfaces such as wood or metal. The cutting edges comprise a plurality of replaceable inserts held in place by a clamping mechanism. In an extended length version such as would be used for finishing a wide surface, a plurality of straight inserts are mounted side by side in an approximation of a helical pattern. Each insert consists essentially of a cutting blade and a blade-locking wedge. The blade is provided with a circular hole, an elongated hole and two cutting edges. The blade is mounted in place via the said holes on cams which are eccentrically mounted on the ends of screws disposed in bores of the body of the cutting tool. The blade is retained in place by the blade-locking wedge. The cams are smaller in diameter than the holes, and as screws are adjusted, the cams raise and lower the respective ends of the blade until it is accurately positioned. Once the wedge is accurately aligned, lock screws are threaded into the said bores to secure the said screws against further movement. Each individual cutting blade must be aligned to the required setting in a costly and time-consuming adjustment process. It is the object of the present invention to provide an improved planing tool for woodworking machines which is designed for large planing widths, which does not have the above-mentioned detrimental effects, and in which the knives are reusable, simple to exchange, and uncomplicated to align. The present invention achieves this object according to the characterizing features of the patent claims. Because there are a number of helical grooves on the surface of the head of the inventive planing tool, extending from one end of the head to the other and regularly distributed over its circumference, any pulsating stress on the knives secured in the grooves is avoided. Instead of a single knife disposed in each of the grooves and extending over the entire length of the groove, there are a number of small, adjacent, continuous, individually secured knives in each of the grooves. Second grooves disposed parallel to the first grooves are provided for receiving a guide component of a knife-aligning device. The cutting levels of the individual knives can thereby be equalized with one another and identically adjusted without any great expenditure of energy. The individual knives of two neighbouring gooves are mutually offset by half a knife-width. Owing to these features of the inventive planing tool, smooth running of the tool, and consequently a high-quality, immaculate surface of the machined workpiece, is achieved even with operating widths of over two meters. A further advantage of the invention is that the small knives take the form of double-edged disposable blades, thus eliminating costly resharpening. Moreover, cemented-carbide knives, e.g., of tungsten carbide, or diamond knives can be utilized. The invention is explained in more detail below, by way of example, with the aid of drawings. Fig. 1 shows the tool according to the invention in a perspective view, without the knives and wedging devices inserted, and Fig. 2 shows a side view of the planing tool with knives and wedging devices disposed in the grooves and with the second grooves for guiding the knife-aligning device, Fig. 3 shows as an exploded drawing and in a perspective view a single wedging device with an associated knife, Fig. 4 shows the tool according to the invention with a knife-aligning device positioned thereon, and Fig. 5 shows the lateral offset of the individual knives disposed in adjacent grooves. Fig. 1 shows the substantially cylindrical head 1 of the inventive planing tool. At each of the ends 3, 4 of the head 1 there are concentric journals 21, 22, the purpose of which is to mount the planing tool rotatingly in bearing means (not shown). Uniformly distributed over the peripheral surface of the head 1 are grooves 2, each of which has a substantially dovetail cross-section, two sidewalls 17, 18, and a bottom 9 including blind holes 10 spaced from one another at intervals A along the groove 2. The holes 10 are used for positioning and immobilizing wedging devices not shown in this drawing figure. Running parallel to each groove 2 is a second groove 16 of substantially rectangular cross- section intended to receive a guide component 26 of a knife-aligning device (Fig. 4). In Fig. 2, the inventive planing tool is seen in an end-on elevation. Secured in the grooves 2 by means of wedging devices 6 and securing means 7 are knives 5. The wedging device 6 has for this purpose a central bore 11, provided in the embodiment illustrated with an internal thread, in which a securing means is disposed, e.g., a headless screw 7 with a shoulder affixed at one end. The shoulder is designed to fit into one of the blind holes 10 in the bottom 9 of the groove 2. By turning the screw 7 clockwise, the wedging device 6, with the knife 5 resting against a contact surface 14, is pressed against the outwardly tapering sidewalls 17, 18 of the dovetail groove 2 and held fast. In order that the shavings produced during the planing of workpieces may be optimally removed, the wedging device 6 has on the side remote from the bottom 9 of groove 2 a depression 15. Bordering on a cutting edge 20 of the knife 5, the depression 15 has essentially a rounded shape with a radius R. This ensures excellent lifting and guidance of the shavings during machining of a workpiece. The wedging device 6 shown in Fig. 3 includes two parallel bores 13 running at right angles to the contact surface 14 of the knife 5. In each of the bores 13 is a pin 8 projecting beyond the contact surface 14 by no more than the thickness of the knife 5. The knife 5, preferably of steel, tungsten carbide, or diamond, is lamella-shaped and has two opposite cutting edges 19, 20 and two continuous holes 12 in the flat. The holes 12 are spaced from one another by the same distance B as the pins 8 pressed into the bores 13 of the wedging device 6. The diameter of the holes 12 is slightly greater than that of the pins 8. For positioning the knife 5 roughly, its holes 12 are fitted on the protruding pins 8 so that one flat side of the knife 5 rests against the contact surface 14 of the wedging device 6. The knife-and-wedging device assembly thus formed is pushed, with the screw 7 slightly unscrewed, into one of the grooves 2 from one of the ends 3 or 4 and, as described earlier, braced against the sidewalls 17, 18 by driving in the screw 7. Each of the grooves 2 is fully outfitted by lining up such assemblies of wedging devices 6 and knives 5. In the embodiment illustrated, the knife 5 has two opposite cutting edges 19, 20. By rotating the knife 180 degrees, either the one edge 20 or the other 19 may be brought into operating position. As a modification, disposable knives 5 may be used. Expensive and time-consuming resharpening is thereby avoided. Positioned on the planing tool depicted in Fig. 4 is a knife-aligning device 25 used to align the individual knives 5 in such a way that the cutting edges 20 all project evenly and by the same amount beyond the surface of the head 1. The device 25 comprises two brackets 30 (only one being shown in Fig. 4). One end of each bracket 30 is rotatingly connected to one of the journals 22, while a spindle 28 is rotatingly mounted between the other ends of the brackets 30. At one end of the spindle 28 is a handle 29 for turning it. One end of a guide component 26 engages a helical groove 31 running the length of the spindle 28, while the other, spatula-shaped end of the guide component 26 fits into one of the second grooves 16. Thus, when the spindle 28 is rotated, the guide component 26 moves along the length of the head 1 of the planing tool. An aligning wheel 27, rotatingly connected to the guide component 26 in a manner not visible in detail, aligns the individual knives 5 disposed in one of the grooves 2 with respect to the protrusion of the cutting edges 20 beyond the surface of the head 1. Fig. 5 illustrates the manner in which the blind holes 10 in the bottoms 9 of two adjacent grooves 2 are staggered by half of the interval A. It is thereby achieved that the ends of the cutting edges of each of the knives ranged side by side are offset relative to one another in neighboring grooves 2. Owing to such offsetting, no traces of the individual knives are visible on the machined surface of a workpiece.

Claims: A planing tool for a woodworking machine, having a substantially cylindrical head (1) with at least one helical groove (2) extending from one head end (3) to the other head end (4) and having a bottom surface (9) and two sidewalls (17, 18), and a plurality of wedging devices (6) and a corresponding plurality of knives (5) disposed therein, characterized in that the helical groove has a dovetail cross-section for holding the correspondingly shaped wedging devices (6) against radial separation, that there are blind holes (10) spaced from one another at intervals (A) in the bottom surface (9) in the longitudinal direction of the groove (2), in that each of said wedging devices (6) has a central bore (11) with a securing means (7) disposed in it, whereas each of the securing means (7) is engaged with one of the said blind holes (10) for wedging the wedging device (6) into the groove, and that the knife (5) has two continuous holes (12) disposed on its flat side for receiving two pins (8) projecting on a contact surface (14) of the wedging device (6) for positioning the knife (5). A planing tool according to claim 1, characterized in that in the wedging device (6) there are two bores (13) running parallel to one another and disposed at right angles to the said contact surface (14), and in that the said pins (8) projecting on the said contact surface (14) are disposed in the said two bores (13). A planing tool according to claim 1 or 2, characterized in that the side of the wedging device (6) facing away from the bottom surface (9) of the first groove (2) has a depression (15) for carrying off shavings. A planing tool according to one of the claims 1 to 3, characterized In that the knife (5) has two opposite cutting edges (19, 20), and that the knife is so disposable on the wedging device (6) that either the one cutting edge (20) or the other cutting edge (19) projects in the groove (2) for machining a workpiece. A planing tool according to one of the claims 1 to 4, characterized in that the knife (5) is made of diamond. A planing tool according to claim 1 to 4, characterized in that the knife (5) is made of tungsten carbide. A planing tool according to claim 1 to 4, characterized in that the knife (5) is made of steel. A planing tool according to one of the claims 1 to 7, characterized in that the central bore (11) of the wedging device (6) has a thread, and that the securing means comprises a headless screw (7) provided with a shoulder for penetrating Into the blind hole (10). A planing tool according to one of the claims 1 to 8, characterized In that there is a second groove (16) running parallel to the groove (2) for receiving a guide component (26) of a knife-aligning device. A planing tool according to one of the claims 1 to 9, characterized in that the knives (5) disposed In two adjacent grooves (2) are offset relative to one another by a distance (A/2).

Inventors: DE ABREU, ALFREDO FERREIRA
Applicants: MIDA - MAQUINAS INDUSTRIAIS DO AVE, LDA.
Application year: 1988
Main classification: B27G13
IPC codes: B27G13, B24B3