CH619884A5 - Disc-shaped plate for a sanding machine with suction - Google Patents

Abstract

The plate comprises a rigid upper part on the lower face of which there is bonded a flexible sole plate (9). Recesses (8) made in the upper face and separated by radial ribs constitute depression chambers communicating with the suction end fitting of the sanding machine. These chambers furthermore communicate on the one hand with openings (6) passing through the plate on its thickness and, on the other hand, with openings (7) opening out on the conical periphery of the plate. An abrasive disc, clamped on the plate by means of an elastic ring housed in a peripheral groove of the upper part, is perforated opposite the various openings of the plate. Thus, the dust is sucked directly through the abrasive disc and the plate without the sanding machine having to have cumbersome projecting parts. <IMAGE>

Description

The present invention relates to a disc-shaped plate for a dust suction sander.

The sanders are widely used in various industrial operations. For example, in the automotive industry, bodies are generally sanded before receiving one or more coats of primer and one or more coats of paint. In addition, it is often the case that the intermediate layers are sanded or touched up to soften the corners and eliminate certain imperfections before applying the final layer of paint.

To solve the problems posed by dry sanding, the Canadian patent application N ° 148535 proposes a very effective system of suction of the dust produced by a sander. This system uses a vacuum chamber surrounding the sanding pad and the abrasive disc. The chamber has several orifices distributed around the periphery of the circular abrasive disc of the sander. The suction ports which are very close to the area attacked by the abrasive suck up almost all of the dust released.

Despite its efficiency in evacuating dust, this suction system has two drawbacks. On the one hand, the vacuum chamber hides the abrasive disc and the sanding plate from the view of the worker who cannot therefore see the edge of the disc and the effect of sanding on the workpiece. It is known that a large part of the sanding work is done in particular areas using the edge of the abrasive disc and, to execute the operation properly, the worker always prefers to see the surface that he is sanding. . This is not possible when the vacuum chamber of the sander hides the periphery of the abrasive disc.

The second drawback of such a system is also linked to the presence of the vacuum chamber which forms a kind of bead around the periphery of the abrasive disc and which prevents sanding to the edge of a part having a rim or a any projection. These parts of the part must be sanded using a conventional sander without vacuum chamber, which lengthens the operation and produces a certain amount of dust which tends to settle on the other parts of the part.

To solve these problems, the invention provides the suction sander plate, defined in claim 1, making it possible to directly vacuum the dust at the surface which is being sanded, through the abrasive disc and the 5 turntable.

The advantage of this tray lies in the fact that the suction ports on the tray create localized suction effects which attract almost all of the particles removed by the abrasive. This surprising result is probably due to the fact that, in industrial pneumatic sanders, the plate and the abrasive disc are driven not only by a rotational movement, but also by a vibratory movement. These relatively high frequency vibrations cause the abrasive disc to deviate slightly from the workpiece surface periodically. It is likely that the particles torn from the surface of the part are free to move inward or outward under the effect of air currents during the periods of the vibratory cycles when the disc is slightly away from the workpiece surface. Thanks to this intermittent migration, practically all of the particles are sucked in through the orifices of the abrasive disc and of the plate.

This suction device is so effective that it even removes particles sticking to the surface by electrostatic attraction. This point is of considerable interest in industrial applications, since it becomes practically unnecessary to wipe the surface after sanding for other operations such as painting. The implantation of the suction orifices in the central part and at the periphery of the plate facilitates the entrainment of the particles which adhere to the surface of the part by electrostatic attraction.

Another advantage is that the suction of the central orifices 30 tends to press the abrasive disc against the surface of the workpiece. The operator therefore does not have to press the sander strongly against the surface of the workpiece, which is particularly convenient for sanding a surface from below.

Another advantage of the tray is that it extends the life of the abrasive discs. This effect is undoubtedly due to the fact that the particles torn away by the abrasive grains are immediately entrained by the suction device instead of being ground by the rotation of the disc. Thus, the cutting edges of the abrasive grains are always available to attack the surface of the piece. In addition, the immediate entrainment of the particles torn off from the surface of the part prevents fouling of the disc by accumulation of dust between the abrasive grains.

Another advantage inherent in this plate is that it produces a constant air flow which cools the abrasive disc, the plate and the bearings of the sander, whose longevity is improved. This cooling effect makes it possible to sand continuously while, until now, the sanding operation had to be periodically interrupted to avoid overheating of the disc and the plate. This translates into increased productivity.

n / a In the case of a large diameter plate (for example 200 mm), experience has shown that it is advantageous to arrange the peripheral suction passages not radially, but oriented in the direction of rotation in the disc plan. This configuration of the orifices and suction passages ensures a certain scooping effect of the peripheral air which is added to the suction created by the vacuum. If the passages were radial or oriented rearwards, the rotation of the plate would have no influence on the air suction capacity. The peripheral and central suction passages meet in the thickness of the disc 60 to open into the central part of its rear face in common orifices. This configuration makes it possible to reduce the diameter of the vacuum chamber which should preferably not exceed the periphery of the plate for the reasons indicated above.

65 The choice of dimensions and configuration of the central suction ports must be carefully studied. There must be sufficient passage sections for the central holes to ensure effective dust extraction. The

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central holes must be relatively far apart to distribute the suction power, but if several holes are drilled on a concentric circle, they should not be too far from the center to avoid the formation of an air stagnation zone allowing the accumulation of dust in the center of the disc.

The sanding plate can consist of a semi-rigid circular disc lined on its front face with a flexible sponge sole of the same diameter. It is desirable that the backing disc is not completely rigid, since a slight flexibility makes it easier to work with the edge of the abrasive disc in regions that are difficult to sand like concave parts, fillets, etc.

In some cases, the vacuum chamber of the sander can have a diameter close to that of the plate to cover its entire rear face. It is however preferable to reduce the diameter of the chamber to minimize the size of the sander. In this case, a flexible cover can be used covering the rear face of the tray, particularly for small diameters. This cover cooperates with the vacuum chamber to channel the air which is sucked in through the passages of the tray. The rigidity of this cover must be adapted to that of the semi-rigid support disc of the plate, so as to conform to its deformations when the operator works with the edge of the disc.

Excellent results have been obtained with a support disc and a cover molded from a hard plastic material such as nylon. The flexible sole can be made of foam rubber, flexible or semi-flexible polyurethane foam, or any other suitable material. The combination of a sponge sole with a semi-rigid support disc and cover gives a sanding plate covering a wide range of applications.

The suction passages can be drilled obliquely between the rear face of the support disc and its circumferential surface or the edge of its working face furnished with the flexible sole. The central suction passages are drilled more or less vertically in the central part of the support disc and open into the central part of the flexible sole. The cover, when it exists, also includes several suction holes drilled in a concentric circle approximately at mid-radius. The interior of the cover thus communicates with the vacuum chamber which is connected to a vacuum source, so as to produce a suction at the orifices of the tray.

The support disc can take different configurations to meet specific requirements. The first of these requirements is obviously a good distribution of the suction between the peripheral and central orifices, when they coexist. These two types of ports must in turn communicate with the suction ports on the cover.

The center of the plate support disc can be fitted with an axial bolt which screws into a tapped hole at the end of the motor shaft. The direction of the thread is chosen to ensure a tightening when the engine starts and during the rapid rotation of the plate. If the thread is in the opposite direction, the plate tends to unscrew at start-up and when it attacks the workpiece, which can be very dangerous at high speed.

The accompanying drawings show by way of example several embodiments of the subject of the invention.

Fig. 1 is a side elevational view of a pneumatic sander equipped for the suction of dust through the sanding disc.

Fig. 2 is a top view of a tray cover.

Fig. 3 is a top view of the sander plate of FIG. 1.

Fig. 4 is a diametrical section of the plate of FIG. 3.

Fig. 5 is a diametrical section of the plate of FIG. 3 associated with the cover of FIG. 2.

Fig. 6 is a plan view of an abrasive disc with a flexible peripheral skirt.

Fig. 7 is a side elevational view of a suction sander, the rotary plate of which is equipped with an abrasive disc like that of FIG. 6.

Fig. 8 is a partial section of the plate and of the vacuum chamber of the sander of FIG. 7.

Fig. 9 is a perspective view from below of the sander showing in particular the configuration of the abrasive disc.

Fig. 10 is a diametrical section of a sanding plate with an annular flexible sole.

Fig. 1 shows a pneumatic sander 1, the motor of which is supplied with compressed air by a flexible hose 1a for driving a sanding plate 2 in rotation. The plate 2 is surmounted by a cover 4 which communicates with a vacuum chamber 10 comprising a nozzle suction 13. We see, in fig. 1, that the plate 2 comprises a series of peripheral suction orifices; it can also include central suction ports.

The plate 2 consists of a semi-rigid disk 8 stiffened by radial ribs, and a flexible sole 9 fixed under the disk 8 (see fig. 3). The sole 9 can have different degrees of flexibility depending on the type of sanding to be performed. The plate 2 has, at its periphery, one or more suction orifices 7. In practice, the nozzle 13 is connected to a source of vacuum which creates a vacuum in the chamber 10 and in the passage system of the rotary plate 2 .

In general, the cover 4 and the support disc 8 are semi-rigid and, when they are deformed by a pressure on the surface of the part, the cover 4 tends to deviate locally from the bottom of the chamber. depression 10. To still maintain a good seal, the bottom of the chamber 10 is provided with a flexible skirt 3 which presses on the cover 4. The skirt 3 is generally a rubber band (or a similar elastic material) whose dimensions are calculated to form a fold 3a substantially at mid-height. The elasticity of the skirt 3 maintains a constant pressure on the rear face of the cover 4. To prevent the skirt from going back up along the vacuum chamber 10, the latter forms an annular seat 14 below the end piece. suction 13. The seat 14 can be formed in the outer surface of the chamber 10 or can be a metal ring attached around the outer surface of the chamber. The ribbed disc forms a circumferential groove 23 which can receive an elastic ring used to fix the abrasive disc on the plate, as will be seen in detail below.

The chamber 10 comprises a device for suppressing the depression consisting of a horizontal slot 70 and a curved plate 71. A button 72 is fixed to the plate 71 which can move horizontally behind the slot 70 inside the chamber 10 When the button 70 is in its position of FIG. 1, the chamber 10 is completely closed and the vacuum applied by the nozzle 13 is transmitted to the suction holes 7. Conversely, when the button 72 is pulled towards the right end of the slot 70 (in FIG. 1 ), the plate 71 slides inside the chamber 10 and closes the passage of the end piece 13. The absence of vacuum facilitates the change of abrasive disc. In the absence of this device, the abrasive disc tends to be sucked into the holes 7 and risks tearing or deforming. By bringing the button 72 and the plate 71 in an intermediate position along the slot 70, the suction force can be measured.

We see in fig. 2, that the cover 4 is pierced with several communication holes 5 around a central hole 18.

Fig. 3 is a plan view showing the top of the support disc 8, which is reinforced by radial ribs and the marginal part of its flexible sole 9. Several suction holes 6 are drilled in the central part of the disc and several holes 7 are drilled in the peripheral part of the disc. A threaded rod 17 is fixed to the center of the support disc 8. In the configuration illustrated, there are eight central suction holes and eight peripheral suction holes which ensure efficient evacuation of sanding dust.

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Fig. 4 is a section of the plate of FIG. 3 in the diametrical plane A-A. We see that the central holes 6 cross the entire thickness of the plate. On the other hand, the peripheral holes 7 connect the interior of the ribbed disc 8 to the circumferential surface of the periphery of the elastic sole 9.

The section in fig. 5 shows the plate of FIG. 4 and also the cover 4 which is associated with the ribbed disc 8. The cover 4 is traversed by holes 5 which communicate both with the central holes 6 and with the peripheral holes 7 of the tray 2. When the tray is capped with sound cover 4, it constitutes a sort of rotary vacuum chamber.

Fig. 6 shows the plan shape of an abrasive disc 15 which mounts on the plate 2 and which has central and peripheral holes corresponding to the configuration of the suction orifices of FIGS. l to 5. The abrasive disc has a circular central part 15 pierced with a series of holes 20 near its center. The part 15 is surrounded by a flexible skirt 16 which is cut out from a series of radial notches 21. The disc is covered with an abrasive substance 22 on its central part 15, but not on its peripheral skirt 16. The disc has a centering hole 19 intended to facilitate its positioning and its attachment to the plate 2.

Fig. 7 is a side elevational view of the pneumatic sander of FIG. 1, the rotary plate of which is covered with an abrasive disc having the shape illustrated in FIG. 6. The disc being centered on the plate, the segments of its flexible skirt 16 are folded against the circumferential surface of the plate, taking care to make the notches 21 coincide with the suction holes 7. Thus, the skirt 16 does not interfere the passage of the air which is sucked into the holes 7. The skirt 16 is clamped against the circumferential surface of the plate by an elastic ring 24 which engages in the peripheral groove 28 of the support disc 8 (see fig. 1 ). The abrasive disc 15 is fixed to the plate 2, so that its abrasive surface faces outwards.

Fig. 8 partially shows the interior of the sander of FIG. 7 and indicates the paths followed by the air which is sucked in through the orifices 6 and 7 of the plate when a vacuum is applied to the chamber 10. In practice, it is possible to connect an industrial vacuum cleaner to the nozzle 13, for example a 1.5 kW vacuum cleaner from the Eurêka brand. For the adaptation of such a vacuum cleaner, the nozzle 13 must have a diameter of 32 mm. We see in fig. 8, that the air, which is sucked in through the central holes 6 and through the peripheral holes 7 of the tray, passes through the cover 4 through the holes 5 and ends up in the vacuum chamber 10 from where it is drawn 5 towards the vacuum cleaner by the nozzle 13. Such a system makes it possible to suck the air from the orifices 6 and 7 with minimal leaks, even when the plate 2 rotates at high speed relative to the rest of the sander. Fig. 8 also shows how the plate 2 is mounted on the shaft 25 of the pneumatic motor. To this end, the shaft 25 io carries at its lower end a mandrel 26 into which the threaded rod 17 of the plate 2 is screwed (fig. 4). When the rod 17 is screwed in fully, it is immobilized by means of a lateral locking screw 27.

Fig. 9 is a perspective view from below of the pon-iser 1, showing in particular the vacuum chamber 10, the underside of the plate 2 and the abrasive disc 15. The eight suction holes 6 are distributed in a circle in the part central sole 9. Their angular positions correspond to those of the peripheral holes 7. This configuration facilitates the machining of the 20 holes 6 and 7 and also the mounting of the abrasive disc.

In fig. 9, the abrasive disc 15 is of annular shape and has a large central opening 28. It is also possible to use the disc of FIG. 6 which is pierced with eight central holes 20 corresponding to the holes 6 of the plate. The flexible skirt 16 of the abrasive disc is fixed to the periphery of the plate using a rubber ring 24.

In some sanding applications, it is desirable to work with a very flexible pad. For this, we generally add an annular sole made of cellular material. This technique is easily applicable to the tray, as illustrated in FIG. 10. The tray in question is that of FIG. 5, which is completed by an additional sole 54 mounted directly under the normal sole 9. The annular sole 54 is arranged concentrically and is held in place by the abra-35 sif disc 15 which in this case comprises a single central opening. One could also use the abrasive disc of fig. 6, provided that the configuration of its central holes does not prevent the correct operation of the suction of the tray. The abrasive disc 15 is fixed to the plate by its skirt 16 which is held in place by an elastic ring 24, as described above.

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2 sheets of drawings

Claims (2)

619 884 2 CLAIMS 1. Disc-shaped plate for vacuum sander, characterized in that it comprises upper and lower portions provided with a first group of openings made through the plate in a direction normal to it, in that the lower portion is made of a flexible, elastic material, capable of conforming to the contour of a surface to be sanded, in that the upper portion, linked to the lower portion, is made of a firmer material, in that the periphery outer of the plate is, upwardly inclined towards the inside and comprises a peripheral groove constituting a housing for an elastic clamping ring, in that the upper portion of the plate comprises a central connecting boss, a drive means and a plurality of ribs extending radially outward from the boss to an outer upper lip defining, with the ribs, a plurality of vacuum chambers, in that each of the openings of the first group ends in one of said vacuum chambers, and in that the inclined external peripheral wall of the plate has a series of openings, each of which ends in one of said chambers. 2. Tray according to claim 1, characterized by a cover centered on the upper face of the tray and closing the top of the chambers, and comprising a series of openings facing the chambers.