CH615108A5 - Sucking sanding machine - Google Patents

Abstract

The sanding machine with suction comprises a rotary plate (2) to which an abrasive disc is fastened. In order effectively to evacuate the sanding dust, the sanding disc comprises a series of openings placed opposite corresponding openings (6) made through the rotary plate (2), and communicating with a vacuum chamber (10) connected via an orifice (13) to a vacuum source. The sanding machine is used, for example, in the motor industry for sanding bodywork. <IMAGE>

Description

The present invention relates to dust suction sanders.

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. It is also frequent that the intermediate layers are sanded or touched up to soften the angles and eliminate certain imperfections before the application of the final layer of paint.

Finishing any item almost always requires one or more sanding operations to give it a satisfactory surface finish. So far, all sanding processes have suffered from a serious drawback: the production of fine dust resulting from the abrasion of the sanded material. This nuisance is particularly accentuated in the case of devices working at high speed, since the dust released is so fine that it often remains long in suspension in the air.

A large capacity sanding installation using high speed equipment releases huge amounts of fine dust which creates particularly unsanitary working conditions for workers. The fine particles remaining in suspension for a considerable time are inhaled by the workers and are deposited on their clothes and on all exposed surfaces in the vicinity of work stations. The evacuation of sanding dust is therefore a crucial problem.

Many solutions have been proposed to try to solve this problem, especially in high capacity and high speed installations. In auto plants, it is common to water the work surface to produce a continuous film of water that entrains the fine particles released by the sander. This technique is known as wet sanding. However, although it helps minimize the release of flying dust, it has the disadvantage of using considerable amounts of water and creating arduous working conditions, since workers must wear waterproof clothing and work constantly in a cold and humid atmosphere.

The ideal technique is dry sanding, provided that the dust problem can be resolved. With this in mind, we obviously thought of using a suction system, but the current results are relatively disappointing. The efficiency of these vacuum cleaners is relatively poor and considerable quantities of dust escape into the atmosphere with the drawbacks described above.

Static electricity is another source of problems in dry sanding of metal and plastic surfaces. More specifically, under the effect of electrostatic charges produced by the friction of the sander, the dust adheres to the sanded surfaces and current vacuum cleaners are unable to dislodge them.

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,

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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 proposes a solution consisting in directly sucking the dust at the level of the surface which is being sanded, through the abrasive disc and the rotary plate. The invention relates to a suction sander, which is the subject of claim 1.

According to one embodiment, one or more orifices are drilled at the periphery of the plate either in its circumferential surface or in its working face, and communicate with holes in the periphery of the abrasive disc. The best results are obtained with holes in both the central area and the peripheral area of the platter, especially for platters and discs of small diameter. For trays and large diameter discs, one can be satisfied with central orifices, but peripheral orifices can improve the efficiency of the suction. A suction effect is produced at the orifice (s) by a vacuum chamber which is placed between the rear face of the plate and the drive motor of the sander. The assembly consisting of the vacuum chamber, the plate and the abrasive disc constitutes a suction system directly connecting the sanded surface to a vacuum source.

The advantage of the solution proposed by the invention lies in the fact that the suction orifices of the plate create localized suction effects which attract almost all of the particles torn off 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 separated from the surface of the room. Thanks to this intermittent migration, the particles are practically all sucked by the orifices of the abrasive disc and the plate.

The suction device of the sander of the invention 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 useless 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 abrasive disc facilitates the entrainment of the particles which adhere to the surface of the part by electrostatic attraction.

Another advantage of the configuration of the invention is that the suction of the central orifices tends to press the abrasive disc against the surface of the part. 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. The presence of suction orifices at the periphery of the plate does not provide any holding effect and a reduced holding effect is obtained when there are orifices in the center and at the periphery of the plate.

In the case of sanders equipped with large diameter plates with central suction orifices, the suction effect is such that the operator can practically not move the abrasive disc on the surface of the workpiece. This drawback can be solved by equipping the sander with a vacuum adjustment valve to adjust the suction effect. By acting on this valve, the user can arrive at an optimal compromise between the suction force which presses the abrasive disc against the surface of the part and the suction of dust. With a little practice, you can easily get a good mobility of the sander and an efficient evacuation of dust.

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Another advantage of the sander of the invention is that it prolongs 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 workpiece. 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 suction device is that it produces a constant flow of air which cools the abrasive disc, the plate and the bearings of the sander whose longevity is improved. This cooling effect of the abrasive disc makes it possible to sand continuously while up to now the sanding operation had to be periodically interrupted to avoid excessive heating of the disc and the plate. This translates into increased productivity.

The suction through central and / or peripheral orifices can be adapted to an abrasive disc sanding system with flexible support of the type described in Canadian patent application No. 203840. This flexible support is made of a material of thickness and suitable characteristics attached to the back of the abrasive disc. Linen is particularly suitable for this use. When such an abrasive disk with flexible support is used on the sander of the invention, it must have holes whose configuration corresponds to that of the central and / or peripheral suction orifices of the plate. During assembly, these holes must be arranged so as not to obstruct any of the suction orifices, especially at the periphery of the plate when the canvas skirt of the disc is folded down. The efficiency of the suction is therefore not reduced by the use of cloth-backed abrasive discs.

To fix the abrasive discs with a cloth back, you can use an elastic ring fitting in a groove in the circumferential surface of the plate on the canvas skirt of the disc.

The central part of the disc can be pierced with several holes corresponding to the central holes in the tray or with a single large diameter hole covering all the central holes in the tray. The two configurations give equivalent results.

In a similar manner, the canvas skirt and / or the periphery of the abrasive disc can be pierced with round holes or cut out with radial notches extending up to the outer circumference of the skirt. In the second case, the disc looks like a daisy. All these configurations are suitable provided that the suction openings on the tray are not obscured.

When the abrasive disc has a central circular opening, the cut round can be recovered for use as an abrasive disc on a rotary sander of corresponding diameter. The abrasive disc market is largely standardized. The central disc of the disc can therefore be cut to a standard diameter and reused as an abrasive disc to reduce falls.

Experience shows that the periphery of the abrasive disc works much more than its central part. This phenomenon is due to the fact that the linear speed is higher there and that the workers generally prefer to use the edge of the plate to carry out certain special works. Consequently, the use of an annular disc from which the central part is cut has practically no influence on the efficiency of sanding.

By way of example, starting from a 203 mm diameter disc from which a central 127 mm disc is cut, an annular abrasive disc 38 mm wide can be produced having excellent efficiency on the sander of the invention. The central disc can be used on standard 127mm sanders.

The choice of the number and configuration of the central openings of the disc must obviously take into account the surface area of the abrasive necessary for sanding and the mechanical resistance of the disc and its canvas skirt. An annular disc of large dia3

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meter is subjected to significant centrifugal forces when the plate rotates at high speed.

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 plane of the disc. 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 depression. 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 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.

It is recommended to use the abrasive discs with a cloth back fixed by a skirt of peripheral fabric. These discs are easy to replace and avoid the use of adhesives which tend to block the suction openings on the tray. It is however possible to use conventional abrasive discs bonded to the face of the plate with a suitable adhesive, on condition that care is taken to avoid introducing glue into the central suction ports. When the abrasive disc is worn, it is enough to detach it from the plate by pulling on its edge.

The choice of the dimensions of the central opening or the configuration of the central suction orifices must be carefully studied. The passage sections of the central hole (s) must be sufficient to ensure effective dust extraction. If the tray has several central holes, they must be relatively apart to distribute the suction power. Similarly, in the case of a single central hole, the diameter of the orifice must not be too large so as not to excessively reduce the surface of the abrasive disc. Conversely, 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 installation of the abrasive disc and its cloth skirt on the sander plate can be facilitated by the use of a loading device automatically ensuring the correct positioning of the disc and its elastic fixing ring. Such a loading device automatically ensures the alignment of the central holes and the notches of the skirt of the disc with the corresponding orifices of the tray. It also facilitates the positioning of the elastic ring in the peripheral groove of the plate to tighten the canvas skirt. The installation of abrasive discs can also be done by hand, but the use of a loading device is preferable in an industrial context.

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 because a slight flexibility makes it easier to work with the edge of the abrasive disc in areas that are difficult to sand like concave parts, fillets, etc.

In some cases, the vacuum chamber may 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 backing disc and a cover molded from a hard plastic like 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 are 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 concentric circles 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 vacuum chamber which is mounted between the sanding pad and the motor must be rigid enough to withstand atmospheric pressure and to withstand rough treatment. The chamber can be made of steel, rigid plastic material or the like. A molded semi-rigid nylon chamber is both strong and light, which is advantageous for the maneuverability of the sander.

The vacuum chamber can be a bell carrying on the side a connection piece to the vacuum source. It is obviously possible to provide several connection ends, but only one is generally sufficient. The vacuum source creates a strong vacuum inside the chamber which is transmitted to the suction ports through the passages of the tray.

In the case where the support disc and the cover, when it exists, are slightly flexible, it is difficult to ensure the seal between the vacuum chamber and the cover or the plate if the latter is deformed. To avoid inadvertent air entry which would result in a reduction in the efficiency of the suction device, it is desirable that the junction between the suction chamber and the tray or its cover is provided by an elastic skirt. This skirt perfectly fits the deformations of the cover or the tray and ensures a good seal, even when the rotation is rapid. It is obviously possible to use other sealing systems giving equivalent results.

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 part,. 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.

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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 of the invention, showing in particular the configuration of the abrasive disc.

Fig. 10 is a side elevational view of a semi-rigid sanding plate 20 cm in diameter.

Fig. 11 is a side elevational view of a pneumatic sander with a 20 cm platform provided with a dust suction chamber.

Fig. 12 is a perspective view of the vacuum chamber of the sander of FIG. 11.

Fig. 13 is a perspective view from below of the vacuum chamber of FIGS. 12 and 13.

Fig. 14 is a perspective view of the sander plate of FIG. 10.

Fig. 15 is a plan view of an abrasive disc having a circular central opening and several holes drilled in its peripheral part.

Fig. 16 is a diametrical section of a sanding plate with an annular flexible sole.

Fig. 17 is a diametrical section of an apparatus for loading the abrasive discs onto the plate of the sander of the invention.

Fig. 18 is a section through a tray similar to that of FIG. 5, but having only central suction orifices.

Fig. 19 is a section through a plate similar to that of FIG. 18, but having only peripheral suction orifices.

Fig. 20 is a plan view of an abrasive disc having a circular central opening and holes drilled at the periphery of its annular abrasive surface.

Fig. 21 is a plan view of an abrasive disc having a circular central part and a peripheral part cut out with radial notches.

Fig. 22 is a side elevational view of a sanding plate provided with the abrasive disc of FIG. 21 which is fixed by an elastic ring.

Fig. 1 shows a pneumatic sander 1, the motor of which is supplied with compressed air by a flexible hose 1a for rotating a sanding plate 2. 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 nozzle 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 suction 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.

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. 1 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 comprises a centering hole 19 intended to facilitate its positioning and its attachment to the plate 2, as will be seen below.

Fig. 7 is a side elevational view of the pneumatic sander of FIG. 1, the turntable 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 outward.

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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 Eureka brand. For the adaptation of such a vacuum cleaner,

the end piece 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 entrained towards the vacuum cleaner by the tip 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 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 sander 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 central part of the sole 9. Their angular positions correspond to those of the peripheral holes 7. This configuration facilitates the machining of 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.

Fig. 10 shows a plate 29 of larger diameter, that is to say 20 cm in diameter. This plate consists of a semi-rigid support disc 30 and a flexible protruding sole 29, preferably made of cellular material, having a diameter of 203 mm. Central suction holes 31 are drilled vertically around the common axis of the support disc 30 and the sole 29. Peripheral suction holes 32 open at the periphery of the sole 29. These holes can communicate internally with the central holes 31, as indicated in dotted lines in FIG. 10. In such a configuration, when a vacuum is applied at the top of the holes 31, the air is sucked in both from the bottom of the holes 31 and through the peripheral holes 32. The sole 29 has a peripheral groove 42. A chamber vacuum depicted in broken lines in FIG. 10 partially covers the rear face of the support disc 30.

Fig. 11 illustrates a 20 cm plate sander comprising a pneumatic motor 33 and a vacuum chamber 34 similar to that of FIG. 10. The pneumatic motor 33 can be a compressed air turbine of approximately 0.93 kW of the Dotco brand driving the plate at approximately 1500 rpm.

The vacuum chamber 34 has a connecting piece 35 and a sealing skirt 36. The skirt 36 can be made of rubber or another elastic material and can be reinforced to withstand atmospheric pressure by layers of canvas or the like. The skirt 36 is held in place by a rubber ring 37. The chamber 34 and its skirt 36 cover the rear face of the support disc 30. The vacuum chamber 34 is fixed to the pneumatic motor 33 by a clamp 43.

An abrasive disc 39 is fixed under the rotary plate by a peripheral skirt 40 which is clamped in the groove of the plate by a rubber ring 41. The notches of the flexible skirt 40 coincide with the peripheral holes 32 of the plate when it has them .

Practical experience has shown that with a 20 cm plate having suction holes only in its central part, the abrasive disc is applied with such force against the workpiece that it is difficult to move the sander. It is therefore desirable that the worker can manually adjust the intensity of the suction using a control valve 38 mounted on the chamber 34. He can thus adjust the value of the vacuum so that the displacements of the sander requires only moderate force. When the tray is provided with peripheral suction orifices, the retaining force is negligible and the adjustment valve 38 is not necessary.

Fig. 12 is a perspective view of the vacuum chamber 34 provided with its rubber skirt 36 and its fixing elastic 37. It can be seen that the adjustment valve 38 is a screw 38a surrounded by a helical spring 44. Several small holes 45 are cut in the wall of the chamber 34 around the hole of the screw 38a. Fig. 13 which shows the underside of the chamber 34, makes it possible to see the other parts of the valve 38. The screw 38a engages in a nut 47 which holds a closing disc 46 against the interior surface of the chamber 34. In service, when a strong vacuum prevails inside the chamber 34, the disc 46 slightly deviates from the adjacent wall by compressing the spring 44. A certain air flow can then enter through the holes 45 to reduce the vacuum that prevails in the chamber 34. This air flow is adjustable by screwing or unscrewing more or less the screw 38a to suitably adjust the force of the spring 44. The valve 38 is therefore a vacuum regulator associated with the chamber 34.

We also see in fig. 13 that the side wall of the chamber 34 has a window 48 making it possible to engage a key or another tool for locking the plate 29 on the shaft of the pneumatic motor 33.

Fig. 14 illustrates a detail of the plate 29 relating to the configuration of the peripheral holes 32 which are connected to the central holes 31. Due to this internal connection, the suction of the holes 32 is derived from that of the holes 31. The passages leading could be drilled to the holes 32 in radial directions from the axial passages 31. It is however preferable that the holes 32 are inclined in the direction of rotation of the plate to benefit from the scoop effect which is important at a rotation speed of around 1500 rpm. For this, each hole 32 is drilled in the direction of the hole 31 which immediately precedes the one which is on the same radius as the hole 32 (as shown in dotted lines in FIG. 14). Fig. 14 also shows the central threaded rod 49 which serves to fix the plate 29 to the end of the motor shaft 33 (fig. 11).

On the sander plate of fig. 11, an abrasive disc can be used, the central part of which comprises holes which correspond to the positions of the holes 31 of the plate, and the peripheral skirt of which comprises holes whose positions correspond to those of the peripheral holes 32 of the plate. The configuration of such a disc can be that of FIG. 6 or a variant comprising only a circular central opening of a diameter sufficient to surround all the holes 31 of the plate. Fig. 5 illustrates another possible configuration of an abrasive disc 51 comprising a central opening 58. In this case, the flexible skirt 52 is not cut as in FIG. 6, but has circular holes 53 allowing the suction of air through the peripheral orifices 32 of the plate.

Other variants of the abrasive disc can be used with the sander of the invention. One can, for example, have a simple circular disc with or without a central opening depending on whether the tray has central suction holes or not. The disc sticks directly to the working face of the tray and does not need to have a flexible skirt 52. The major drawback of using an adhesive is that it ends up blocking the suction orifices of the plateau. In addition, the residues of hardened glue accumulating on the working face of the plate form bumps and recesses which cause irregular wear of the abrasive disc, the life of which is reduced.

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In some sanding applications, it is desirable to work with a very flexible pad. For this, an annular sole is generally added in a material of suitable characteristics, generally a cellular material. This technique is easily applicable to the tray of the invention, as illustrated in FIG. 16. The plate 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 abrasive disc 15 which in this case has 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. 15

To facilitate the placement of the abrasive discs on the pan, the loading device in fig. 17. This device is suitable for mounting a flexible skirted disk with an additional sole 54 on a plate 20 cm in diameter reinforced by a semi-rigid disk 30. It is obvious that this application is not limiting and that the device can be modified for other configurations and dimensions of abrasive disc, with or without additional sole.

The apparatus of fig. 17 comprises a cylindrical cup 59 ^, the center of which is provided with a centering pin 55. The pin 55 is surrounded by an elastic element 56, for example a block of polyurethane foam or a coil spring. The elastic element 56 is surmounted by a circular centering plate 57 having a central cylindrical boss. Thanks to this configuration, the plate 57 can receive an abrasive disc with flexible skirt and central opening, and an annular sole 54. A rubber ring is arranged around the external cylindrical surface of the bowl 59. The abrasive disc 52 and the additional sole 54 being stacked on the centering plate 57, as illustrated ^ in fig. 17, the plate 29 and its support disc 30 are threaded onto the centering pin 55.

To fold the skirt 52 around the plate 29, it suffices to push the latter into the loading device by compressing the elastic element 56 until the circumferential groove 42 40 is aligned with the upper edge of the bowl 59 At this time, it only remains to roll the elastic ring 41 to the edge of the bowl so that it falls into the groove 42 to tighten the flexible skirt 52 around the periphery of the plate.

Fig. 18 is a section through a tray 60 having only "central suction ports 61. Although a tray with orifices

615 108

is generally more efficient, the model in fig. 18 is however very effective in removing dust from a room. In the case of fig. 18, a cover 62 is associated with the plate 60, but it can be eliminated if a vacuum chamber 10 extending to the periphery of the plate is used (see FIG. 8).

Fig. 19 is a section through a tray 63 having only peripheral suction orifices 64. Like the central suction tray of FIG. 18, the plate 63 ensures a very effective suction of the sanding dust, but at the periphery of the disc. The peripheral orifices 64 open out near the surface of the part to create a suction effect similar to that of the vacuum chamber described and claimed in Canadian patent application No. 148535. The plate of FIG. 19 does not create a suction effect under the abrasive disc and the operator must use his muscular force to exert the necessary pressure on the sander. The ideal configuration is therefore that of a plate having both central and peripheral ports judiciously dimensioned. The tray in fig. 19 is associated with a cover 65 which can be eliminated if a vacuum chamber of suitable configuration is used, as in the case of FIG. 18.

• Fig. 20 shows an abrasive disc configuration comprising a central opening 69, a flexible peripheral skirt 67 and a series of peripheral suction holes 68 drilled at the periphery of the annular abrasive zone 66. In this case, the flexible skirt 67 is not neither pierced nor cut. This type of abrasive disc can be used with a plate whose peripheral orifices open into the working face, and not into the circumferential surface as in the examples of FIGS. 1, 4, 5 and 7. A slight drawback of the suction holes 68 drilled in the abrasive surface 66 of the disc is that they can sometimes catch sharp projections on the workpiece, in which case the disc tears. On the other hand, this arrangement of the peripheral orifices ensures more efficient dust extraction.

Fig. 21 illustrates another form of abrasive disc 70, the circular part of which is pierced with a central hole 73. The periphery of the disc 70 is cut out by trapezoidal notches 71 forming regularly spaced teeth 72. Such a disc is mounted on a plate 74 of the type illustrated in fig. 22. The disc is fixed by a rubber ring 75 tightening the teeth 72 against the circumferential surface of the plate.

The same principle can be applied to a sander with a rotary and vibrating plate, with multiple actions and with an oscillating plate, provided that a good seal is maintained between the vacuum chamber and the movable plate.

R

4 sheets of drawings

Claims (7)

615 108 1. Suction suction machine, characterized in that it comprises a plate connected to a drive means and comprising a sanding disc fixed on it detachably, a vacuum chamber mounted on the upper surface of the plate, a series of openings on the active face of the disc and arranged opposite with openings on the underside and / or side of the tray, all the openings being in communication with the vacuum chamber, a means provided on the vacuum chamber for adjusting the value of the vacuum, the vacuum chamber being connected to the drive means which passes through the center of the chamber, and in that it comprises a flexible skirt between the lower peripheral edge of the chamber and the upper face of the plate, the chamber being arranged so as to be able to undergo bending relative to the plane of the plate. 2. Sander according to claim 1, characterized in that the diameter of the chamber is less than that of the plate, in that the chamber has an orifice connected to a vacuum source and in that the means making it possible to adjust the value of the depression comprises a plate on the interior wall of the chamber and movable between an inactive position in which the orifice is uncovered, and an active position in which the orifice is found covered. 2 3. Sander according to claim 2, characterized in that the side wall of the chamber has a slot and in that the plate has a protruding lever exiting through the slot to allow manual adjustment of the value of the vacuum. 4. Sander according to claim 1, characterized in that the means for adjusting the value of the depression comprises a series of perforations in the wall of the chamber, and an adjustable plate biased by a spring and covering the perforations. 5. Sander according to claim 1, characterized in that the plate comprises a flexible and elastic lower section, connected to a harder and more rigid upper section, and a rigid cover covering the upper section, arranged between the upper section of the plate and the lower peripheral edge of the chamber. 6. Sander according to claim 5, characterized in that the upper section of the plate comprises a series of radial ribs, interposed with the openings made in the plate, each pair of two adjacent ribs delimiting an internal vacuum chamber contained in the cover, and in that it comprises on the outer side wall of the tray a series of openings in communication with the internal chambers, these openings having a diameter less than that of the openings on the underside of the tray. 7. Sander according to claim 1, characterized in that the sanding disc comprises a central abrasive portion of the same diameter as the underside of the plate and a flexible peripheral skirt extending beyond the outer edge of the abrasive portion, arranged to fold up on the side wall of the tray, and having a series of openings facing the openings of the side wall of the tray.