EP0038763A1 - Machine for grinding rounded angles - Google Patents

Abstract

1. Machine making it possible to produce convex, rounded, quarter-circular profiles, irrespective of their radius, by an abrasion technique using an endless abrasive belt (2) running for part of its trajectory over a shoe (1), characterised in that the active face of the shoe (1), corresponding to the region in which the abrasive belt (2) acts on the workpiece to be abraded, is a helicoid portion of which the length which is necessary is sufficient to effect the said abrasion in a single pass of the workpiece to be abraded on the machine and limited to a quarter of the pitch of the said helicoid, the extreme, entry and exit edges of which are located in mutually perpendicular planes, the one being horizontal and the other vertical, in that the shoe is machined in such a way that the abrasive belt engages obliquely with the workpiece to be abraded, in that the active region of the abrasive belt moves in the dihedron formed by the horizontal working surface of the machine and the vertical face of a longitudinal guide, in that the position of the shoe is adjustable, irrespective of the radius of the rounded profile to be produced by abrasion, relative to the two reference planes formed by the working surface and the guide, in that the shoe can be adjusted to match the size of the rounded profile to be produced by abrasion, and in that the shoe includes means making it possible to reduce the effects of the rubbing of the belt on the shoe.

Description

The present invention relates to machines for sanding convex rounded angles, in particular in the field of furniture manufacturing.

Certain pieces of furniture, such as chairs, for example, require the execution of a sanding operation over several tens of linear meters, of constituent elements comprising, obtained with a router, rounds of more or less large radii. The machines hitherto used are generally of two types: machines with continuous belts and machines with discs. The first named use abrasive bands: sanding is carried out by a pad corresponding to the counter-shape of the rounding to be sanded and acting directly on the abrasive band; in certain cases, this pad is perforated and milled, this in order to diffuse compressed air at constant pressure, so as to constitute a sort of air cushion between the strip and the pad allowing the strip to float and .a continuous cooling thereof. Pre-shaping pulleys allow, on the other hand, the adhesion of the strip to the pad. These machines have the following drawbacks. Necessity of having a range of pads corresponding to the rounded edges to be sanded; use of the strip over only part of its width, resulting in faster localized fouling and wear thereof. The disc machines use as an abrasive disc or grinding wheel of form whose active face corresponds to the counter-profile of the rounding to be sanded. These discs may consist of a base disc on which are mounted a flexible profiled ring and an external flexible support, the abrasive element proper conforming to the shape of the profiled ring. Other flexible disc wheels are obtained from a polyurethane binder in which abrasives of the corundum or silicon carbide type are incorporated. They can also be constituted by a system of nonwoven nylon threads in which the abrasive grains are distributed and fixed by synthetic resins. The use of machines of this kind requires the user to have as many tools as there are types of rounding to be sanded. Some machines use special discs or pads, which are shaped at the time of use according to the molding of the workpiece. All of these solutions, which are expensive due to the diversity of tools and the idle times allocated to the installation and replacement of the tools on the machine, all have the following drawback: the abrasive tool used, whether it is a strip or a grinding wheel, frontal attack on the flare over its entire profile, causing rapid fouling of the tool and burning of the wood by the difficulty of removing chips; moreover, the rotary sanding obtained using the grinding wheels does not allow to reach the quality of the long sanding.

The machine according to the invention makes it possible, using a single tool, to sand convex quarter round convex rounds, whatever their radius, using a standardized abrasive strip throughout its width, without risk of d fouling thereof, or burning of the sanded material, the sanding carried out by said machine being of the enveloping type assimilating to long sanding quality carried out manually, the attack of the abrasive strip being effected tangentially to the one of the plane surfaces previously sanded taken as face and acting progressively on the continuation of the quarter-round profile as the workpiece to be sanded advances on the machine, to end, at the end of sanding, tangentially to a second plane reference face previously sanded perpendicular to the first reference face, the part of the part to be sanded having to cover the entire length of the pad to obtain the complete sanding of the flare, the sanding station itself being able to be integrated into the assembly of a multiple shaping machine.

The machine, object of the invention, is mainly characterized in that it comprises a pad of helical shape on the surface of which circulates a continuous abrasive band driven by a pulley-motor assembly, the active zone of the band evolving in the dihedron. formed by a horizontal work table and the vertical face of a longitudinal guide, which shoe is on the one hand adjustable in position whatever the radius of the rounding to be sanded, according to the two reference planes constituted by the table and the guide and on the other hand adjustable to adapt to the value of the rounding to be sanded. The active face of the pad is a portion of helicoid limited in length to a quarter of the pitch so that the theoretical edges of the end of the pad are in orthogonal planes, the angle of torsion of the abrasive strip remaining compatible with its mechanical characteristics ; this active face of the pad is covered with a kind of thin mattress made of graphite material improving the conditions of friction of the back of the abrasive strip during its passage over the pad. These frictions are also attenuated by the presence, at each end of the shoe, of cylindrical rollers ball avoiding overheating and wear of the band in contact with the edges limiting the shoe in its length. To ensure proper chip clearance, the band attacks the piece of wood to be sanded not frontally but at a certain angle; for this purpose the machining of the pad is carried out in such a way that the axis of the strip and the axis of the pad form a certain angle.

• - en figure 1, une vue d'ensemble d'une machine multiple comportant le dispositif de ponçage,
• - en figure 2, une vue en perspective cavalière montrant le détail du patin et la trajectoire de la bande abrasive sur ce patin,
• - en figures 3 et 4, les vues en élévation et en bout du profil théorique du patin,
• - en figures 5, 6, 7 et 8, des vues différentes de l'hélicoïde théorique constituant la face active du patin au cours du pivotement de celui-ci autour de l'axe XX',
• - en figures 9 et 10, des vues longitudinales du patin montrant les usinages d'extrémité du patin et la trajectoire de l'axe de la bande abrasive par rapport à l'axe longitudinal du patin,
• - en figures 11 à 16, les différentes formes d'arrondis pouvant être traités avec le dispositif de ponçage,
• - en figure 17, une vue en perspective des moyens d'ajustage et de réglage du patin.

The accompanying drawings illustrate, by way of example, an embodiment of the machine according to the present invention. These represent:

• - in FIG. 1, an overall view of a multiple machine comprising the sanding device,
• in FIG. 2, a perspective view showing the detail of the pad and the trajectory of the abrasive belt on this pad,
• - in Figures 3 and 4, the elevation and end views of the theoretical profile of the skate,
• - in FIGS. 5, 6, 7 and 8, different views of the theoretical helicoid constituting the active face of the pad during the pivoting of the latter around the axis XX ′,
• - in FIGS. 9 and 10, longitudinal views of the pad showing the end machining of the pad and the trajectory of the axis of the abrasive belt with respect to the longitudinal axis of the pad,
• - in FIGS. 11 to 16, the different forms of rounding which can be treated with the sanding device,
• - In Figure 17, a perspective view of the means for adjusting and adjusting the pad.

The sanding device, the main characterizing element of the machine, consists of a pad 1 whose active face of helical shape serves as a sliding path for an abrasive belt. continuous 2 driven in translation along a substantially triangular path at the top of which the shoe is located, the other angles respectively comprising a deflection pulley 3 and a drive driving pulley 4 wedged on the shaft of an electric motor 5, the tension of the strands of the strip being ensured by the tilting mounting of said motor on the frame of the machine. The active face of the skate is similar to a portion of helicoid, surface generated by the displacement of the diameter of a cylinder resting on the axis of the latter and on a propeller drawn on the periphery of the cylinder, the helical resembling a screw with a thread of axis coincident with that of said helical, of depth equal to the radius, of width equal to the diameter of the generator cylinder. The length of this portion of helicoid is limited to the value of a quarter of a step so that the end edges are arranged perpendicular to one another; for an observer placed, as shown in FIG. 3, in alignment with the axis 00 ′ of the helicoid, the exit edge AA ′ of the shoe forms a right angle with the entry edge BB ′. The pivoting of the shoe around the axis XX 'perpendicular to the generator of the helicoid passing through the point W located in the middle of 00', makes appear for the same observer, a rounded connection between AA 'and BB' whose radius increases with said pivoting. Figures 5 to 8 show the many possibilities of obtaining rounding of all radii that the machine allows from the simple wiping of the edge to the large rounding.

In the example shown in Figure 1, the pad 1 is connected to the machine frame by means of means for adjusting the abrasive face of the strip at the entry and exit of the shoe with respect to reference planes corresponding respectively to the horizontal plane of the machine table and to the vertical plane containing the longitudinal guide of the work to be sanded and by means allowing adjust the value of the rounding to adapt it to that of the workpiece. To improve the sliding of said abrasive strip on the pad, the helical face of the latter is lined with a sort of mattress consisting of a strip 6 of flexible graphite material. This mattress constitutes an easily interchangeable wearing part. The risks of wear and overheating of the abrasive belt on the entry and exit edges of the pad are also mitigated by the presence of cylindrical rollers 7 and 8 mounted on ball bearings, said rollers being slightly set back by compared to the upper face of the graphite strip. In order to avoid a frontal attack of the piece to be sanded by the abrasive band, in order to obtain a good clearance - of the chips, avoiding any risk of fouling of the band, the pad is machined so that the generator of the helicoid is no longer strictly perpendicular to the longitudinal axis of the skate but forms with it an angle equal to 90 ° -â, â being the angle formed by the axis of the strip and the axis of the skate (Figures 9 and 10).

The abrasive face of the belt is adjusted at the input roller 7 relative to the horizontal reference plane formed by the machine table by acting on a screw 9 for controlling the front part in vertical translation skate support; the adjustment of said abrasive face of the belt at the output roller 8 with respect to the vertical reference plane constituted by the longitudinal guide is effected by acting on a screw 10 for controlling in horizontal translation the rear part of the pad support. These two possibilities of adjusting the abrasive belt with respect to these two reference planes allow a perfect tangential connection of the sanding of the rounding with the prior sanding of the adjoining planar faces.

The setting of the value of the radius of the rounding is obtained by a combined action on a control screw 11 in horizontal translation of the front part of the pad support at the input roller 7 and on a control screw 12 in vertical translation of the rear part of the pad support at the output roller 8. A cut 13 made both in the table and in the longitudinal guide allows the passage of the abrasive strip 2 in the angle of the dihedron formed by these two parts of the machine.

According to this set of provisions, the machine performs an enveloping type sanding similar to long quality sanding done manually, the attack of the workpiece by the abrasive strip taking place tangentially to one of the flat faces, that which is supported on the machine table for example, previously sanded, taken as a reference face, which abrasive strip acts progressively on the rest of the quarter-round profile as the workpiece is advanced on the machine to end, for example, at the end of sanding, tangentially to a second reference face also previously sanded, perpendicular to the first reference face, that which is in abutment on the longitudinal guide by example.

The action on the two screws 11 and 12 allows sanding of all types of rounded convex shapes as shown without limitation in Figures 11 to 16, from the simple blowing of the edge (Figure 11) until the rounding of a semicircle tangentially connecting the two opposite flat faces of the piece of wood (figure 16). FIG. 12 illustrates the case of the rounding of a quarter of a circle tangentially connecting two orthogonal faces; FIG. 13 shows a rounding of radius substantially equal to the thickness of the piece of wood tangent to one of the faces leading to the opposite face of the latter by a second rounding of very small radius; FIG. 14 illustrates the case where a rounding tangent to one of the faces of the part ends in secant on the contiguous face, finally according to FIG. 15, a rounding may not be sanded which does not end tangentially on the two adjoining flat faces. In the case of FIG. 16, the sanding of the semicircle is obtained by two successive passes with turning of the piece to be sanded; the same is true in the case of FIG. 13. The rounding, whatever the case, always corresponds to a quarter of a circle.

FIG. 17 shows the detail of the fastenings of the support plate 14 of the shoe 1, on which plate the cylindrical rollers 7 and 8 are also fixed. On the screw 11 serving for adjustment as a function of the value of the rounding to be sanded mounted a handle 11a forming a nut, the screwing of which on the screw pushes along a nut 15 by compressing an antagonist spring 16 interposed between said nut and the plate 17 fixing the screw on the frame, which spring ensures the translation of the translation of the nuts when you unscrew the handle lla. This screw is crossed by the screw 9 for adjusting the roller 7 relative to the table, which screw is extended at the top by a smooth part 9a which is housed in an oblong groove 18 executed in the longitudinal axis of the support plate 14 a compression spring 19 is interposed between the underside of the nut and a control handle 9b secured to the screw 9, the purpose of this spring being to avoid loosening of the screw under the effect of possible vibrations of the machine, by the contact pressures thus exerted on the threads of the screw. The vertical line of action of the screw 9 is located substantially perpendicular to the axis of the cylindrical roller 7. Similarly, on the screw 10 used for adjusting the roller relative to the longitudinal guide of the machine, is mounted a handle 10a, forming a nut, the screwing of which on the screw pushes along a nut 20 by compressing an opposing spring 21 interposed between said nut and the plate 22 fixing the screw to the frame, said spring ensuring the translation reversal nuts when you unscrew the handle 10a. The nut 20 is crossed by the adjustment screw 12 according to the value of the rounding to be sanded: this screw is the extension of the axis of the roller 8, the smooth part 12a of which crosses the nut, the threaded part being limited to the lower part for receiving a handle 12b forming a nut, the screwing of which ensures the vertical translation of the nut by pushing it, following f "by compressing an opposing spring 23. By these different methods of fixing the shoe, the operation of the screws 11 and 12 for carrying out the adjustment of the rounding can be carried out while keeping the rollers 7 and 8 respectively in a horizontal plane and a vertical plane.

The sanding unit according to the invention can be integrated as a terminal station in the assembly of a multiple machine carrying out the various machining phases preliminary to the sanding operation for rounding. Such a machine can also include in line two or more sanding units intervening successively on the lower and upper edges of the part to be treated, so as to carry out for a single passage of the part on the machine, all of the sanding its rectilinear edges, which sanding units intervene on one and / or the other or the other edges of said part. The quality of the sanding obtained using the device involves running the workpiece at constant speed, hence the need for it to be taken over by a drive device. Similarly, it is recommended to obtain this result, simultaneous routing and sanding operations.

In the example described, the positioning of the pad is adjusted relative to the horizontal and vertical reference surfaces which constitute the work table and the longitudinal guide respectively. According to a known technique, the positioning of the pad can be determined using feeler devices by taking as reference two orthogonal faces of the piece to be sanded, the pad then being mounted on a floating head.

The invention is in no way limited to the embodiment of its various specially indicated parts, but on the contrary embraces all possible variants provided that these are not in contradiction with the subject of each of the claims annexed to the present description.

The machine equipped with the sanding device, object of the invention, can be used for all rounding sanding operations carried out on parts of solid wood, chipboard, plastic or other materials, and more particularly in the field of furniture. , chaisery, woodwork or any other delicate work.

Claims (10)

1. Machine making it possible to sand convex quarter-round convex rounds whatever their radius, using for one and only tool a continuous abrasive strip of standardized width without risk of fouling thereof, or of burning the sanded material, characterized in that it comprises a pad (1) placed on the circuit traversed by the abrasive strip (2) and on the surface of which pad said strip passes from a horizontal plane to a vertical plane, attacking the rounded to be sanded tangentially to one of the flat faces of the previously sanded part taken as the reference face and acting progressively on the quarter-round profile as the workpiece is advanced on the machine, to reach the end of sanding tangentially to a second flat reference face previously sanded, perpendicular to the first reference face, the part of the part to be sanded having to cover the entire length of the pad to obtain sanding to tal of the rounding, the positioning of said pad being adjustable relative to the two reference surfaces and adjustable as a function of the value of the rounding to be sanded. 2. Machine according to claim 1, characterized in that the active face of the pad on which the abrasive belt circulates is a portion of helicolde limited in length to a quarter of the pitch so that its inlet end edges and of exit are in orthogonal planes, one horizontal, the other vertical. 3. Machine according to claims 1 and 2, characterized in that the active face of the shoe is machined in such a way that the generator of the heli-cold is not strictly perpendicular to the longitudinal axis of the pad but forms with it an angle equal to 90-o-â, _' â being the angle formed by the axis of the strip and the axis of the pad, this angular offset ensuring good clearance shavings preventing rapid contamination of the abrasive belt. 4. Machine according to claims 1, 2 and 3, taken together, characterized in that the active face of the pad is lined with a mattress consisting of a strip (6) of flexible graphite material favoring the sliding of the abrasive strip on the pad, which mattress forming a wearing part is easily interchangeable. 5. Machine according to claims 1, 2, 3 and 4, taken together, characterized in that parallel to the entry and exit edges of the active face of the shoe and tangentially thereto are arranged cylindrical rollers (7, 8) located slightly behind the upper face of the graphite strip in order to limit the risk of wear and overheating of the abrasive strip on said entry and exit edges of the pad. 6. Machine according to claim 1, characterized in that the adjustment of the abrasive face of the belt at the input roller relative to the horizontal reference plane formed by the machine table is effected by vertical translation of the front part of the pad support, the adjustment of said abrasive face of the strip at the output roller with respect to the vertical reference plane constituted by the longitudinal guide being effected by horizontal translation of the rear part of the pad, these adjustments of the abrasive belt with respect to these two reference planes allowing a tangential connection perfect sanding of the rounding with the prior sanding of the adjoining planar faces, whatever the radius of the rounding. 7. Machine according to claim 1, characterized in that the positioning adjustment of the abrasive face of the belt as a function of the value of the radius of the rounding to be sanded is obtained by horizontal translation of the front part of the pad support at the input roller and by vertical translation of the rear part of the pad support at the output roller. 8. Machine according to claims 6 and 7, taken together, characterized in that the pad support consists of a plate (14) on which the pad and the inlet and outlet rollers are fixed, which plate comprises, executed in its longitudinal axis, an oblong buttonhole (18) in which engages directly with the input roller (7), the upper end of a screw (9) for controlling the front part in vertical translation of the support, screwing into a nut (15) by compressing an opposing spring (19) ensuring stability of the vertical adjustment of the input roller relative to the horizontal reference plane, which nut is movable in horizontal translation on a screw control whose end swivels in a plate fixed to the frame of the machine, which screw associated with a compression spring allows the adjustment of the positioning of the abrasive face of the strip according to the value of the radius of the rounding to sand, which setting is obtained naked in conjugation with a second control screw in vertical translation constituted by the extension of the axis of the output roller associated with a compression spring and screwed into a movable nut in translation horizontal on a control screw, the end of which turns in a plate fixed to the frame of the machine, which screw allows the adjustment of the output roller relative to the vertical reference plane. 9. Machine according to claim 1, characterized in that the shoe is mounted on a floating head, the adjustment of the shoe being effected using feeler devices taking as reference two orthogonal faces of the workpiece. 10. Multiple shaping machine in which is integrated as terminal post at least one rounding sanding unit according to claim 1, these units intervening successively on the upper and lower edges of the workpiece to be produced so as to single pass of it on the machine, the whole sanding of its rectilinear edges.

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