SANDING MACHINE WITH TRANSVERSAL BELT

Abstract

A sanding machine, in particular for processing wood surfaces, includes a support and transport plane for the forwarding of the workpieces to be processed; and a belt sanding unit with a transverse abrasive belt inside which a pressure pad is arranged obliquely. The pressure pad is divided into a plurality of pressure elements which can be actuated individually and are controlled by respective sensors that constitute a control beam, Methods are described for compensating the different distances between sensor and respective pressure elements that avoid adaptations of the position of the workpiece to be processed, in particular if the machine contains further non inclined processing units. The sanding machine is particularly suitable even for the processing of large workpieces.

Claims

1-10. (canceled)

11. A sanding machine, comprising: (a) a support and transport plane for forwarding workpieces to be processed; (b) a frame which supports at least one belt sanding unit, wherein (b-1) the sanding unit comprises an abrasive belt which extends, and during operation, rotates transversally, with respect to the feed direction of said support and transport plane, (b-2) inside said abrasive belt is arranged a pressure pad which is arranged with an inclination with respect to the extent of said abrasive belt and which is suitable to press the belt against the workpiece to be processed; wherein said pressure pad is divided into a plurality of pressure elements which can be actuated individually; wherein said sanding machine further comprises: (i) as a control beam a series of sensors, at least one sensor for each pressure element of the pressure pad wherein said control beam is arranged parallel to said abrasive belt; and (ii) a control unit adapted to control the operation of the single pressure elements on the basis of information received from the sensors compensating the different distances between sensor and corresponding pressure element across the working width, and wherein (A) the compensation of different distances between the sensor and the respective pressure element in the control unit occurs by defining: (I) the distance between the centre of the control beam and the centre of the pressure pad as zero point; (II) distances smaller than said distance according to point as value to be subtracted; and (III) distances greater than said distance according to point as value to be added; or (B) the compensation of different distances between sensor and corresponding pressure element in the control unit takes place starting from one end of the control beam or of the pressure pad and considering consecutively the angulation or inclination angle (a) which is formed between a base line that starts in the pressure element closer to the control beam and extends parallel to the extent of the latter and a line passing through all the centres of all the pressure elements while determining the distances between sensor and corresponding pressure element towards the other end wherein the relative distance (yn) of the pressure element from the base line, with respect to which the pad is inclined with the angle (α), is calculated with the formula yn=f.Math.n.Math.sen α with f being the centre distance of the centres of the pressure elements and n being the number of the respective pressure element to be considered with respect to the pressure element closer to the control beam; or (C) the compensation for the unequal distances between the sensor and the corresponding pressure element along the working width is done directly determining by distance measuring devices the distance between the sensor and the pressure element.

12. The sanding machine according to claim 11, wherein the angle of said inclination which is comprised between the leg formed by the extent of the abrasive belt and the leg formed by the extent of the pressure pad opens to the right or to the left.

13. The sanding machine according to claim 12, wherein said inclination is invertible between the position which opens to the right and the position which opens to the left.

14. The sanding machine according to claim 12, wherein in the (A) variant with the inversion of said inclination the sign of the values according to points (II) and (III) is inverted.

15. The sanding machine according to claim 11, wherein said pressure elements are actuated when the workpiece to be processed or its edge is located behind the frontal edge of said pressure element, defining as a frontal edge the edge facing the workpiece to be processed entering under the abrasive belt and as a centre of said pressure element the midpoint of the extent of the pressure element in the direction of the depth of the pad.

16. The sanding machine according to claim 11, wherein between said abrasive belt and said pressure pad is arranged a pressure belt with projections on the surface.

17. The sanding machine according to claim 11, wherein said sanding machine further comprises other processing units wherein are foreseen segmented elements wherein to each segment is attributed one of said sensors.

18. The sanding machine according to claim 11, wherein the pressure elements are movable only in the direction of their height, thus approaching or moving them away from the workpiece to be processed, but they cannot be rotated around the lifting and lowering axis.

19. The sanding machine according to claim 11, wherein the control beam is fixed and is not movable along its longitudinal extent, thus the extent covering the working width, and cannot be inclined.

20. A method comprising using the sanding machine according to claim 11, wherein the frontal edge of said workpiece to be processed enters parallely to the extent of the abrasive belt under said abrasive belt.

21. The sanding machine according to claim 13, wherein in the (A) variant with the inversion of said inclination the sign of the values according to points (II) and (III) is inverted.

22. The sanding machine according to claim 12, wherein said pressure elements are actuated when the workpiece to be processed or its edge is located behind the frontal edge of said pressure element, defining as a frontal edge the edge facing the workpiece to be processed entering under the abrasive belt and as a centre of said pressure element the midpoint of the extent of the pressure element in the direction of the depth of the pad.

23. The sanding machine according to claim 13, wherein said pressure elements are actuated when the workpiece to be processed or its edge is located behind the frontal edge of said pressure element, defining as a frontal edge the edge facing the workpiece to be processed entering under the abrasive belt and as a centre of said pressure element the midpoint of the extent of the pressure element in the direction of the depth of the pad.

24. The sanding machine according to claim 14, wherein said pressure elements are actuated when the workpiece to be processed or its edge is located behind the frontal edge of said pressure element, defining as a frontal edge the edge facing the workpiece to be processed entering under the abrasive belt and as a centre of said pressure element the midpoint of the extent of the pressure element in the direction of the depth of the pad.

25. The sanding machine according to claim 12, wherein between said abrasive belt and said pressure pad is arranged a pressure belt with projections on the surface.

26. The sanding machine according to claim 13, wherein between said abrasive belt and said pressure pad is arranged a pressure belt with projections on the surface.

27. The sanding machine according to claim 14, wherein between said abrasive belt and said pressure pad is arranged a pressure belt with projections on the surface.

28. The sanding machine according to claim 15, wherein between said abrasive belt and said pressure pad is arranged a pressure belt with projections on the surface.

29. The sanding machine according to claim 12, wherein said sanding machine further comprises other processing units wherein are foreseen segmented elements wherein to each segment is attributed one of said sensors.

30. The sanding machine according to claim 13, wherein said sanding machine further comprises other processing units wherein are foreseen segmented elements wherein to each segment is attributed one of said sensors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1a illustrates in a top view the succession of two transverse belts and the relative control beam of an exemplary embodiment of the sanding machine according to the invention.

[0046] FIG. 1b illustrates the configuration of figure la in a front view in the feed direction of the workpieces to be processed.

[0047] FIG. 2 depicts in a top view the sectioning of the pressure pads of the configuration according to FIG. 1 and the distance of the individual pressure elements with respect to the control beam.

[0048] FIG. 3 shows the detail X of FIG. 2 which illustrates the variation of the distance of the pressure elements with respect to a base line which corresponds to the non-inclined position.

[0049] FIG. 4 shows in another exemplary embodiment of the sanding machine according to the invention the integration of transverse belts with inclined pressure pads with other processing units.

[0050] FIG. 5 shows in a perspective view a transverse belt with a pressure pad and a belt interposed according to the state of the art.

[0051] FIG. 6 shows in a top view a comparison between a transverse abrasive belt with a parallel pad and a transverse abrasive belt with an oblique or inclined pad.

[0052] FIG. 7 shows in a perspective view a transverse abrasive belt with an inclined sectioned pad and the corresponding control beam parallel to the belt.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

[0053] With reference to FIG. 1a, the succession of two transverse abrasive belts 2 and 4 and a relative control beam 6 can be seen. The belts 2 and 4 extend transversely to the feed direction (arrow a) of the workpieces to be processed and are realized as continuous belts operated (with a motor not depicted) and tensioned by the rollers 8. The control beam 6 comprises a series of sensors 10 (not all of them depicted) whose operation will be explained further on. In each belt 2, 4 a pressure pad 12 and 14, respectively, is arranged, which is visible in the figure by eliminating a piece of the belt. The pads 12, 14 are inclined with respect to the transverse extent of the belt 2, 4 having in the case of the belt 2 an inclination angle α.sub.1 which opens to the left and in the case of the belt 4 an inclination angle α.sub.2 which opens to the right.

[0054] The person skilled in the art easily identifies a suitable angulation.

[0055] FIG. 1b illustrates the configuration of figure la in a front view in the feed direction of the workpieces to be processed. The control beam 6 is in front of the pressure pads 12, 14.

[0056] FIG. 2 depicts in a top view the sectioning of the pressure pads 12, 14 of the configuration according to FIG. 1 and the distance of the individual pressure elements 10 (not all depicted) with respect to the control beam 6 which is arranged perpendicular to the feed direction (arrow a) of the workpieces to be processed. Each pad 12, 14 comprises a series of individual adjacent pressure elements represented by their respective centre 16 (central points of the width and depth of the pressure element). The distance b indicates the centre distance between two sensors 10 made as small wheels (e.g. 34 mm wide). With c1 and c2 two halves (e.g. 1105 mm) of the centre distance between the extreme sensors d (e.g. 2210 mm) are designated. For each pressure element 16 there is an opposite sensor 10. The distance between the centre of a pressure element 16 and its sensor 10 decreases from left to right, starting from a maximum distance e.sub.max and arriving at a minimum distance e.sub.min. The difference between the maximum distance e.sub.max and the minimum distance e.sub.min is represented by Δe (here 115.6 mm). The centre distance f of the centres of the pressure elements 16 (corresponds to the centre distance of the pistons to which the pressure elements are connected to exert a pressure) corresponds to the centre distance b (34 mm). The two halves g1 and g2 of the projection (on a line parallel to the base line i) of the centre distance k (here 2210 mm) between the pressure elements (i.e. their centres) extremes correspond in the exemplary embodiment shown to 1103.5 mm. The midpoint, i.e. the zero point where there is the average distance between the pressure element 16 and the sensor 10, is represented by the line h. The inclination of the pad 12 with respect to a base line i parallel to the extent of the control beam 6 is represented by the angle α which also manifests with respect to the line h. With m the distance between pads 12 and 14 is indicated.

[0057] FIG. 3 shows the detail X of FIG. 2 which illustrates the variation of the distance of the centre of each pressure element 16 from the control beam (not depicted). With p a line passing through all the centres of all the pressure elements 16 is designated, whose centre distance is indicated, correspondingly to FIG. 2, with f. The centres are equidistant between each other. A line o starts in the pressure element closer to the control beam 16.0 and extends parallel to the extent of the latter. With y1, y2, y3, y4, . . . yn the distances of the individual pressure elements from the line o are indicated. With s the centre distance between the first pressure element 16.0 and the umpteenth pressure element 16.n is designated. The centre distance is generally calculated by multiplying the centre distance f with the number n of the respective pressure element to be considered with respect to the pressure element 16.0. The relative distance yn of the pressure element 16.n from the base line o, with respect to which the pad 12 is inclined with the angle α (here 3°), is calculated with the formula (1):

yn=f.Math.n.Math.sen α  (1),

for visibility reasons each yn is drawn slightly shifted with respect to the real position at the height of the centre 16.n.

[0058] FIG. 4 shows in another exemplary embodiment of the sanding machine according to the invention the integration of transverse belts with inclined pressure pads with other processing units. One or more transverse belts with an inclined pad according to the invention can be integrated into sanding machines which also comprise other processing units. In exemplary form, FIG. 4 has in the feed direction aa workpieces to be sanded 118 arranged on a conveyor belt 120, a first transverse belt 104a with an inclined pressure pad 114a, two longitudinal belts 122, 124 arranged (as well as their sectioned pressure pads 126, 128) perpendicular to the feed direction aa, a second transverse belt 104b with an inclined pressure pad 114b and at a greater distance than the distances between the units described so far a third transverse belt 104c with an inclined pressure pad 114c, a unit of transverse strap brushes 130 for transverse cleaning and finally a blower 132 to eliminate the last traces of dust. The longitudinal belts 122 and 124 rotate in the opposite direction with respect to the feed direction aa of the conveyor belt 120, as indicated by the arrows bb. The rotation directions of the transverse belts 104a, 104b, 104c alternate between clockwise direction (arrows cc) and counter clockwise direction (arrow dd) with respect to the feed direction aa of the workpieces 118 to be processed. Obviously, other combinations of processing units are possible which are easily identified by the person skilled in the art according to the desired processing.

[0059] All the pads shown 114a, 126, 128, 114b, 114c are sectioned with the same number of pressure elements, all of which can be managed by the same sensor bar (not shown) parallel to the pads 126 and 128. A relative pressure element corresponds to each sensor in each pad. According to the invention, it is possible to control working elements inclined or not within the same sanding machine without having to provide control beams for each work unit, without having to adapt the position of the control beam and without having to correct the position of the workpiece to be processed between the individual processing units.

[0060] FIG. 5 shows in a perspective view a transverse abrasive belt 240 with a pressure pad 214.1 and an interposed belt 242 according to the state of the art. The belts 240 and 242 are rotated and tensioned by respective rollers 244 and 246 respectively. The interposed belt 242 has shaped projections 248 which make sure that not all the grains of the belt portion pressed by the pad 214.1 undergo the same force. This double tape principle and the use of a pressure pad, known with its advantages by the state of the art, can also be applied on transverse belts with inclined pads according to the invention. The interposed belt here is parallel to the extent of the pressure pad.

[0061] FIG. 6 shows in a top view a comparison between a transverse abrasive belt 240 with a parallel pad 214.1 and a transverse abrasive belt 204 with an oblique or inclined pad 214.2. For both belts 204 and 240 the same type of pad can be used, only its position (214.1 or 214.2) changes with respect to the tape extent. In case of the belt 204 with inclined pad 214.2, the tape has a width greater with respect to the belt 240 with a parallel pad 214.1. The width of the belt is also defined by the degree of inclination of the pad. With the inclined pad 214.2, the abrasive surface and, of course, the area sanded in a period of time, hinted at by areas 218.1 and 218.2 which are being processed under the respective belts 240 and 204, increases.

[0062] Finally, FIG. 7 shows in a more detailed perspective view the transverse abrasive belt 204 of FIG. 6 with an inclined sectioned pad 214.2 and the relative control beam 206 parallel to the belt 204. The pad is composed of a plurality of pressure elements 216 with relative pistons 217 for exerting pressure on the pressure elements 216. The belt 204 is operated and tensioned between two rollers 208. The control beam 206 is composed of a series of sensors 210 whose number corresponds to the number of the pressure elements 216. Between the pad 214.2 and the abrasive belt 204 a belt 205 with projections 207 is interposed with the above function and is tensioned and operated by two rollers 209. The sanding unit 201 composed of a transverse belt 204, an interposed belt 205 and a pressure pad 214.2 processes a workpiece 218.

[0063] The present invention solves the aforementioned problems and has provided a transverse belt sanding machine which allows the processing of large workpieces, in particular with working widths equal to or greater than 1,350 mm, preferably equal to or greater than 2,200 mm, reducing the support pressure area and thus reducing wear of the abrasive belt. The invention allows the automatic management of an inclined pad compensating for variations in the distance between the control beam and the pad and avoids corrections of the positions of the control beam or even of the workpiece to be processed, regardless of the processing units present in the sanding machine.

[0064] During the implementation stage, the sanding machine and its use, object of the invention, further modifications or embodiments not described and not shown in the attached tables may be carried out. If such modifications or such variants should fall within the scope of the following claims, they should all be considered protected by the present patent.