WO2008034035A1

WO2008034035A1 - Dust vacuuming sander and dust vacuuming sander apparatus

Info

Publication number: WO2008034035A1
Application number: PCT/US2007/078459
Authority: WO
Inventors: Satoru Takinami; Tamotsu Yarimizu
Original assignee: 3M Innovative Properties Company
Priority date: 2006-09-15
Filing date: 2007-09-14
Publication date: 2008-03-20
Also published as: JP5095180B2; JP2008093817A

Abstract

A dust vacuuming sander comprising a housing constituting the outer shape of the dust vacuuming sander with a shroud; a pressurized air path including an air inlet tube for supplying pressurized air, an air-powered motor housed in the housing and an air exhaust tube; a venturi tube having an inlet confronted with an outlet of the air exhaust tube via a gap; and a dust vacuuming path leading from the shroud of the housing to the venturi tube; wherein the pressurized air path further has bypass means which divides a part of pressurized air from the air inlet tube, causes it to bypass the air-powered motor and causes it to recombine downstream of the air-powered motor (6) and thereby the recombined air exhausts through the outlet.

Description

DUST VACUUMING SANDERAND DUST VACUUMING SANDER APPARATUS

Technical Field The present invention relates to dust vacuuming sanders utilizing the venturi mechanism for producing a negative pressure for dust vacuuming, and to dust vacuuming sander apparatus comprising the dust vacuuming sanders.

Background To The Invention Air-powered dust-vacuuming sanders, wherein the motor is driven by a supply of pressurized air, are generally known. Fig. 1 is a sectional view showing a typical structure of an air-powered dust vacuuming sander.

This dust vacuuming sander has a housing 2 which defines the outer shape of the sander, including a shroud 1. The housing is sufficiently rigid to maintain a negative pressure produced inside the dust vacuuming sander, and has sufficient structural integrity to be an external member of a dust vacuuming sanding tool. For example, the housing is formed of a rigid plastic material, a metal casting, etc. Along the perimeter of the shroud 1 is skirt 3, which may be removable.

The pressurized air pathway of the dust vacuuming sander is defined by an air inlet tube 5 through which pressurized air is supplied, an air-powered motor 6, and an air exhaust tube 7. The air inlet tube 5 may have means 8 for adjusting the rate of flow of the pressurized air (for example, a master valve). The air-powered motor may have, on drive shaft 9, a balance weight 10 for stabilizing the rotation of the shaft. For sanding operations pad 4 is attached to the drive shaft 9. The pressurized air supplied from an air source (not shown) is introduced into the air-powered motor 6 through the air inlet tube 5. The pressurized air drives the air-powered motor 6, then passes through the air exhaust tube 7 and flows out through outlet 11, which is the end of the air exhaust tube 7.

A venturi tube 12 is disposed in series with the air exhaust tube 7. The venturi tube 12 is arranged so that the inlet thereof confronts with the air exhaust tube 7 via a gap. There is a space extending from the shroud through the venturi tube. When the air flows out of the outlet 11, a negative pressure is produced by a venturi mechanism, so that the space serves as a dust vacuuming path 13.

In the structure mentioned above, the rotational speed of the air-powered motor 6 is adjusted by changing the rate of flow of the pressurized air by opening and closing the master valve 8, which is one example of means for adjusting the rate of air flow. For low speed sanding, the rate of flow of the pressurized air is decreased, whereas for high speed sanding, the rate of flow of the pressurized air is increased. Consequently, the amount of the air flow through the outlet 11 varies with the rotational speed of the air-powered motor, and therefore, so does the magnitude of the negative pressure produced by the venturi mechanism in the dust vacuuming path. In other words, low rotational speed will lead to insufficient vacuum within the sander and to reduced dust collection efficiency. Brief Description of the Drawings

[Fig. 1] A sectional view showing a typical structure of a dust vacuuming sander.

[Fig. 2] A sectional view showing the structure of a dust vacuuming sander which is one example of the present invention.

[Fig. 3] A sectional view showing the structure of a dust vacuuming sander which is another example of the present invention.

[Fig. 4] A schematic view showing one example of a dust vacuuming sander having bypass means disposed outside the housing; (a), (b) and (c) show one side face, a top face, and the other side face, respectively.

[Fig. 5] A schematic view showing another example of a dust vacuuming sander having bypass means disposed outside the housing; (a), (b) and (c) show one side face, a top face, and the other side face, respectively.

[Fig. 6] A schematic view showing another example of a dust vacuuming sander having bypass means disposed outside the housing; this shows the back face.

[Fig. 7] A cross sectional view showing one example of a backup pad suitable for use in the present invention.

[Fig. 8] A view showing the supporting surface of the backup pad. of Fig. 7. [Fig. 9] A view showing another example of the supporting surface of a backup pad suitable for use in the present invention.

[Fig. 10] A cross sectional view showing one example of an intermediate pad suitable for use in the present invention.

[Fig. 11] A view showing another example of the supporting surface or back surface of an intermediate pad suitable for use in the present invention. [Fig. 12] A view showing another example of the supporting surface or back surface of an intermediate pad suitable for use in the present invention.

[Fig. 13] A view showing another example of the supporting surface or back surface of an intermediate pad suitable for use in the present invention. [Fig. 14] A view showing the abrasive surface of an abrasive material suitable for use in the present invention.

[Fig. 15] A view showing the perforation structures employed in the examples.

Explanation of reference numerals

1 ... Shroud,

2 ... Housing,

3 ... Skirt,

4 ... Pad ,

5 ... Air inlet tube,

6 ... Air-powered motor,

7 ... Air exhaust tube,

8 ... Master valve,

9 ... Rotation shaft,

10 .. . Balance weight,

11 .. . Outlet,

12 .. . Venturi tube,

13 .. . Dust vacuuming path,

14 .. . Bypass means,

15 .. . Valve, 100 ... Vicinity of an air outlet in an air-powered motor chamber,

20 ... Abrasive sheet material, 24, 24' ... Perforations,

30 ... Backup pad, 31 ... Rigid material layer,

32 ... Elastic resin layer,

33 ... Bolt,

34, 34' ... Perforations,

40 ... Backup pad, 44, 44' ... Perforations,

50 ... Backup pad,

54, 54' ... Perforations,

55 ... Channels,

60 ... Intermediate pad, 61 ... Foam layer,

64, 64' ... Perforations,

70, 80, 90 ... Intermediate pad,

74, 74', 84, 84', 94, 94' ... Perforations,

75, 85, 95 ... Channels.

Disclosure of the Invention

The present invention intends to solve such existing problems. The object of the present invention is to provide a dust vacuuming sander in which the magnitude of the negative pressure in a dust vacuuming path produced by a venturi mechanism is independent of the rotational speed of an air-powered motor and a sufficient vacuum is obtained even when the air-powered motor rotates at a low speed, and a dust vacuuming sander apparatus which comprises the dust vacuuming sander.

The present invention provides a dust vacuuming sander, comprising: a housing defining the outer shape of the dust vacuuming sander, the housing having a shroud, an air-powered motor housed within the housing, an air inlet tube for supplying pressurized air to the air-powered motor, an air exhaust tube for exhausting the pressurized air downstream of the air-powered motor, a venturi tube having an inlet opposed with an outlet of the air exhaust tube via a gap, a bypass means, wherein the bypass means separates a portion of the pressurized air from the air inlet tube and recombines it downstream of the air-powered motor.

The pad comprises a backup pad and an optional intermediate pad. The shaft to which the pad is attached is a means for transmitting rotational power from the sander motor directly to the pad, or alternatively, indirectly through a series of gears.

The present invention also provides a dust vacuuming sander apparatus comprising the above-described dust vacuuming sander, a pad, and an abrasive material, wherein the pad is a backup pad, the backup pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the shaft of the air-powered motor; and the abrasive material having an abrasive surface, a back surface and perforations penetrating from the abrasive surface through the back surface, the back surface of which is removably attached to the supporting surface of the backup pad.

The present invention further provides a dust vacuuming sander apparatus comprising the above-described dust vacuuming sander, a pad, and an abrasive material, wherein the pad is composed of a backup pad and an intermediate pad, the backup pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the shaft of the air-powered motor; the intermediate pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the supporting surface of the back up pad; and the abrasive material having an abrasive surface, a back surface and perforations penetrating from the abrasive surface through the back surface, the back surface of which is removably attached to the supporting surface of the intermediate pad.

The dust vacuuming sander of the present invention can exert sufficient vacuum even when the air-powered motor rotates at low speed and, therefore, it excels in dust vacuuming efficiency. Detailed Description of the Invention

Dust Vacuuming Sander

Fig. 2 is a sectional view showing the structure of a dust vacuuming sander which is one example of the present invention. This sander is structurally different from the dust vacuuming sander of Fig. 1 in that bypass means 14 is provided between an air inlet tube 5 and an air exhaust tube 7 in the pressurized air pathway. The bypass means 14 is connected to the air inlet tube and the air exhaust tube at its starting point and its terminal point, respectively. The bypass means 14 separates part of a pressurized air supply from the air inlet tube 5, bypassing the air-powered motor 6 and recombines it downstream of said motor. The bypass means may be a tube or a conduit formed as a part of the housing.

When the master air pressure is kept constant, the rotational speed is adjusted not by increasing or decreasing of the pressurized air flow but by increasing or decreasing the amount of bypassed air. When the amount of air to be bypassed is reduced, the amount of air which flows into the air-powered motor will increase and the rotational speed of the air-powered motor will increase. Conversely, when the amount of bypassed air is increased, the amount of air which flows into the air-powered motor will decrease and the rotational speed of the air-powered motor will decrease. The amount of the air bypassed may be changed, for example, by use of a valve 15 for adjusting the rate of flow of the air, the valve being located along the bypass means 14.

When the valve 15 is opened and the rotational speed of the air-powered motor 6 is reduced, the amount of air which passes through the air-powered motor 6 will decrease. However, this will result in increase in the amount of air which passes through the bypass means 14. The air which passed through the bypass means 14 thereafter combines with the air that passed through the air motor and exits through the outlet 11. Therefore, even when the rotational speed of the air-powered motor 6 is reduced, the amount of air that exits through the outlet 11 does not decrease. As a result, even when the rotational speed of the air-powered motor 6 decreases, the magnitude of the negative pressure produced by a venturi mechanism in the dust vacuuming path 13 does not decrease and therefore prevents a decrease in dust vacuuming.

When the air which bypassed the air-powered motor and the air which passed through the air-powered motor combine together, it is preferable that the flow direction of the former air and that of the latter air be as close to parallel as much as possible. This is because if the flow direction of the air which bypassed the air-powered motor and the flow direction of the air which passed through the air-powered motor are different, air turbulence at the confluence causes noise. The flow direction of the air bypassed the air-powered motor and that of the air passed through the air-powered motor intersect at an angle, for example, of 90° or smaller, preferably 45° or smaller, and more preferably 30° or smaller. Such a configuration will improve the rotational efficiency of the air motor.

Fig. 3 is a sectional view showing the structure of another example of the dust vacuuming sander of the present invention. In this example, a terminal point of bypass means 14 is connected to a vicinity 100 of an air outlet of an air-powered motor chamber. This example is configured so that the air which bypassed the air-powered motor and the air which passed through the air-powered motor join together inside the air-powered motor chamber. The location in the bypass means is not particularly limiting. For example, the bypass means may be located in the housing as shown in Fig. 3 or alternatively may be located outside the housing.

Fig. 4 is a schematic view showing one example of a dust vacuuming sander having bypass means which is located outside the housing. Fig. 4 (a) is a side view of the dust vacuuming sander. Bypass means 14 branches from an air inlet tube 5 and extends over the sander. The bypass means 14 has a valve 15 for adjusting the rate of flow of the air. Fig. 4 (b) is a top view of the dust vacuuming sander, wherein a lever 16 which opens and closes a master valve is not shown. The bypass means 14 bypasses the air-powered motor toward the rotational direction of the air-powered motor and extends to a vicinity 100 of the air outlet of the air motor. Fig. 4 (c) is another side view of the dust vacuuming sander. The bypass means 14 is introduced into the inside of the housing and into the air-powered motor chamber, a portion of which is shown with dotted lines in Fig. 4(c), from the top of the sander. The air which bypassed the air-powered motor joins the air which passed through the air-powered motor at a vicinity 100 of the air outlet of the air motor. The direction in which the bypass means is introduced into the air-powered motor chamber is adjusted so that the flow direction of the air which bypassed the air-powered motor and the flow direction of the air which passed through the air-powered motor intersect at a minimal angle α.

Fig. 5 is a schematic view showing another example of a dust vacuuming sander having bypass means disposed outside the housing. Fig. 5 (a) is one side view of the dust vacuuming sander. Fig. 5 (b) is a top view of the dust vacuuming sander. Fig. 5 (c) is another side view of the dust vacuuming sander. This sander is different from the dust vacuuming sander shown in Fig. 4 in that the bypass means 14 bypasses the air-powered motor in the opposite direction to the rotation of the air-powered motor and extends to a vicinity of the air outlet of the air-powered motor (Fig. 5(b)).

Fig. 6 is a schematic view showing another example of a dust vacuuming sander having bypass means disposed outside the housing. In this figure, a pad is not shown. In Fig. 6, the back face of the dust vacuuming sander is shown. Bypass means 14 branches from an air inlet tube 5 and extends under the air inlet tube 5 and an air exhaust tube 7. It bypasses an air-powered motor in a direction opposite to the rotational of the air-powered motor. It extends to a vicinity of the air outlet of the air-powered motor and is introduced into an air-powered motor chamber in the housing. The bypass means 14 has a valve 15 for adjusting the air flow rate.

Specific examples of the dust vacuuming sander of the present invention include a double action sander, an orbital sander, a gear sander, a single sander, a rocking sander, a strait sander, and the like. The pad attached to the shaft of the air-powered motor, so moves according to the type of sander to which it is attached, for example, an orbital motion if an orbital sander is employed, and in reciprocating motion if a straight sander is employed.

Dust Vacuuming Sander Apparatus

The dust vacuuming sander of the present invention is combined with a pad (a backup pad, an intermediate pad and the like) and an abrasive material, and may be suitably employed for automobile body repair as a dust vacuuming sander apparatus.

In automobile body repair and the like, paint, clear coat, putty filler, primer or the like is abraded, thereby generating a large amount of abraded dust, or swarf. The abrasive swarf has to be removed otherwise the surface of the abrasive material becomes clogged, resulting in reduced abrading efficiency. Consequently, abrasive materials (coated abrasive cloths and papers and the like) and pads (backup pads and the like), having a plurality of perforations for vacuuming dust (approximately 10 mm in diameter) at predetermined positions, have been employed.

When the sander apparatus is attached to a vacuum means, swarf from the abrading process is vacuumed through the perforated abrasive material and perforated pad and subsequently discharged.

Besides automobile body repair, the apparatus of the present invention may also be employed to remove swarf when sanding other types of workpieces, for example, wood, plastic, natural and synthetic stone, and the like.

It has been the conventional wisdom that optimum dust extracting efficiency is achieved when the abrasive material perforations are precisely aligned with the pad perforations. However, when the abrasive material is replaced, the process of aligning the perforations is tedious and may not result in perfect alignment. Likewise, if the abrasive material is replaced with one having a different perforation structure, (the perforation structure means the number, arrangement and size of the perforations) the pad will also have to be replaced in order to precisely align the perforations. Again, a tedious process.

The dust vacuuming sander of the present invention eliminates the need for matching perforation structures of the abrasive material and pad., The dust vacuuming sander apparatus of the present invention provides improved dust vacuuming and cutting performance, improved efficiency and working environment for the operator.

The backup pad, the intermediate pad (optionally employed) and the abrasive material which may be employed in the present invention are described as follows.

Backup Pad

An abrasive material is typically made of a flexible backing, which limits the amount of abrading pressure that can be applied to the work surface. Therefore, the backup pad supports the abrasive material in order to apply adequate abrading pressure to the surface to be sanded.

The backup pad of the present invention is not limited to a particular perforation structure or material. For example, a dust vacuuming backup pad in which about 6 or 7 perforations for vacuuming dust, having a diameter of approximately 10 mm formed at predetermined positions, may be employed. Specific examples include perforated dust vacuuming pads having trade designations such as BODY FILLER SANDING PAD 5312, FEATHER EDGING PAD 5311, SCUFFING PAD 5310, STIKIT DISK PAD 558 IJ, and HOOKIT DUST FREE DISK PAD 5594/5595, available from 3M Company. The means for removably attaching the backup pad on the shaft of the air-powered motor in the dust vacuuming sander is, not limited to as described above, so long as it transmits the pad rotational force of the air-powered motor to the pad. For example, a sander fixing bolt, gears and the like are equipped (at for example the center) on the back surface of the backup pad, and they are fixed on the shaft of the air-powered motor.

The backup pad used in automobile body repair varies in hardness according to the particular sanding operation. For feathering work, an Asker hardness of C5 to C 15 backup pad is preferably employed. For scuffing or removing old paint, a backup pad having an Asker hardness of C20 to C45 is preferable.

Fig. 7 is a cross sectional view showing one example of a backup pad suitable for use in the present invention. This backup pad 30 has a structure where an elastic resin layer 32 is disposed on a rigid material layer 31. The exposed surface of the elastic resin layer 32 side is a supporting surface. The exposed surface of the rigid material layer 31 side is a back surface. The supporting surface may be provided with an attachment member, if needed. The back surface is provided with means for mounting the backup pad to a sander, for example, a bolt 33. Moreover, the backup pad has perforations 34, 34' etc. penetrating from the supporting surface to the back surface.

Fig. 8 is a view showing the supporting surface of a backup pad as shown in Fig. 7. This backup pad 30 has many perforations 44, 44' etc. in its supporting surface. The number of perforations 44, 44' etc. is preferably at least about 20, more preferably from about 20 to 150, and further more preferably from about 30 to 100. The perforations 44 are not always necessary arranged uniformly throughout the supporting surface and the arrangement may be changed depending upon required performance or applications.

The diameter of the perforations of the backup pad is preferably 80 to 120% of the diameter of the perforations of the abrasive material in sheet form. The ratio of from 80% to 120% brings superior dust vacuuming efficiency, adequate support to the abrasive material at around perforations, and good abrasive performance. The ratio is more preferably 90 to 110%.

In the supporting surface of the backup pad, channels may be formed along lines connecting all or part of the perforations 44, 44' etc. Such channels, will efficiently guide the swarf that has passed through the abrasive sheet perforations to the perforations 44, 44' etc. of the backup pad.

The width of the channels is preferably from 1 to 8 mm, for guiding the swarf effectively and for supporting the abrasive material effectively. The width is more preferably 2 to 7 mm. The depth of the channels is preferably from 0.5 to 5.0 mm, due to dust guiding and vacuuming ability. The depth is more preferably 1.0 to 3.0 mm.

Fig. 9 is a view showing another example of the supporting surface of a backup pad suitable for use in the present invention. This backup pad 50 has seven perforations 54, 54' etc. in its supporting surface. The number of perforations 54 is not particularly limited and may be appropriately determined, for example, within the range of from 3 to 70 or from 5 to 19. The diameter and arrangement of perforations 54 are also not particularly restricted and may be determined by taking into consideration the supporting function and dust vacuuming function of the backup pad.

Moreover, the supporting surface of this backup pad 50 is provided with channels 55. The channels 55 are arranged along lines connecting the 20 or more perforations of the abrasive material. The channels 55 interconnect dust vacuuming perforations 54, 54' etc. Swarf which has passed through perforations of the abrasive material travels along the channels 55 and is guided to dust vacuuming perforations 54, 54' etc. of the backup pad.

The channels in the supporting surface of the backup pad need not be arranged along all the lines connecting the 20 or more dust vacuuming perforations of the abrasive material, and may be arranged partly along the lines. In a backup pad shown in Figs. 7 to 9, diameter of the perforations may be different from perforation to perforation, and does not have to be all the same.

Intermediate Pad The intermediate pad means a pad which is used to adjust the hardness or compliancy of the backup according to the needs of the sanding operation. The intermediate pad is not essential for the dust vacuuming sander apparatus of the present invention, but may be optionally mounted between the abrasive material and the backup pad. For example, when abrading an object having a curved surface, if the pad supporting the abrasive material is made of elastic resin, the surface is so hard that the abrasive material does not make uniform contact with the entire curved surface of the object. As a result, it becomes difficult to uniformly abrade the entire surface. As a solution of this problem, a foam pad is mounted between the abrasive material and the backup pad to reduce the hardness of the supporting surface.

The intermediate pad of the present invention is not limited to a particular perforation structure or material. For example, a dust vacuuming backup pad in which about 6 or 7 perforations for vacuuming dust, having a diameter of approximately 10 mm formed at predetermined positions, may be employed. Specific examples include perforated dust vacuuming pads having trade designations such as HOOKIT INTERMEDIATE SOFT PAD 5598, 5599 and 5600, available from 3M Company, may be employed.

Fig. 10 is a cross sectional view showing one example of an intermediate pad suitable for use in the present invention. This intermediate pad 60 is composed of a foam layer 61. One exposed surface is a supporting surface and the other exposed surface is a back surface. The supporting surface and the back surface may be provided with an attachment member, if needed. The intermediate pad has perforations 64, 64' etc. penetrating from the supporting surface through to the back surface.

Fig. 11 is a view showing another example of the supporting surface or back surface of an intermediate pad suitable for use in the present invention. This intermediate pad 70 has seven perforations 74, 74' etc. in its supporting surface. The number of the perforations 74 is not particularly limited and may be appropriately determined, for example, within the range of from 3 to 70 or from 5 to 19. The diameter and arrangement of perforations 74 are also not particularly restricted and may be determined by taking into consideration the supporting function and dust vacuuming function of the intermediate pad.

Moreover, the supporting surface and/or the back surface of this intermediate pad 70 is provided with channels 75. The channels 75 are arranged along lines connecting the 20 or more dust vacuuming perforations of the abrasive material in sheet form. The channels 75 cross the perforations 74, 74' etc. to interconnect them. Swarf which has passed through perforations of the abrasive material travels along the channels 75 and is guided to perforations 74, 74' etc. of the intermediate pad.

The channels in the supporting surface or back surface of the intermediate pad need not be arranged along all the lines connecting the 20 or more perforations of the abrasive material and may be arranged partly along the lines. The width and depth of the channels may be determined like those of the backup pad.

Fig. 12 is a view showing another example of the supporting surface or back surface of an intermediate pad for use in the present invention. This intermediate pad 80 has channels 85 in addition to 61 perforations 84, 84' etc. The channels 85 are arranged along lines interconnecting all the perforations 84, 84' etc. The channels 85 interconnect the perforations 84, 84' etc.

Fig. 13 is a view showing another example of the supporting surface or back surface of an intermediate pad for use in the present invention. The channels in the supporting surface or back surface are arranged along lines connecting the dust vacuuming perforations 94, 94' etc. in a series of concentric loops. In an intermediate backup pad shown in Figs. 10 to 13, diameter of the perforations may be different from perforation to perforation, and does not have to be all the same.

Abrasive Material The abrasive material has an abrasive surface, a back surface and perforations penetrating from the abrasive surface through the back surface. The back surface being removably attached to the supporting surface of the backup pad or the intermediate pad. The abrasive material of the present invention is not limited to a particular perforation structure or material. For example, a dust vacuuming backup pad in which about 6 or 7 perforations for vacuuming dust, having a diameter of approximately 10 mm formed at predetermined positions, may be employed. Specific examples include perforated dust vacuuming pads having trade designations such as DF HOOKIT UNI, DF DRY SANDING FINISH DISK, and WET SANDING FINE DISK, available from 3M Company.

The abrasive material comprises abrasive particles adhered to the surface. The abrasive particles may be of any suitable abrasive mineral for repairing autobody surfaces, for example, aluminum oxide, cerium oxide, silicon carbide, diamond, alumina oxide, including melt alumina, ceramic alumina (including sol-gel alumina) and the like can be used. In addition, the abrasive particles may be fine particles made of plastic, such as polymethacrylate ester, polystyrene, polyolefm and the like. As for the dimensions of the abrasive particles, the average particle diameter is generally approximately 500 μm to 0.45 μm.

Fig. 14 is a view showing the abrasive surface of an abrasive material used in the present invention. This abrasive material 20 in sheet form is provided with 61 perforations 24, 24' etc. on the abrasive surface. The number of perforations 24 is preferably at least about 20, more preferably from about 20 to 150, and further more preferably from about 30 to 100.

The arrangement of perforations 24, 24' etc. is preferably configured to be a contiguous lattice, where the centers of three adjacent perforations form an equilateral triangle. The distance between adjacent perforations, which are located at vertices of an equilateral triangle, is preferably not greater than 1.5 times, and more preferably from 0.5 to 1.5 times the diameters of the perforations. If the distance between adjacent perforations is not greater than 1.5 times the diameters of the perforations, the perforations of the abrasive material and those of the backup pad, or those of the intermediate pad, may be adequately aligned when such pads or abrasive materials are moved about their respective axis of rotation. Consequently, the dust vacuuming efficiency is improved.

The diameter of the perforations 24 is preferably 2 to 8 mm, and more preferably 3 to 7 mm, due to good vacuuming power. Diameter of the perforations may be different from perforation to perforation, and does not have to be all the same.

It is not always necessary for the perforations to be uniformly arranged throughout the entire abrasive surface. This is because the amount of swarf generated is not uniform throughout the abrasive surface. For example, since the abrasive power is weak in the center of the axis of rotation of the abrasive surface and the amount of swarf is small, the dust vacuuming performance does not decrease even if some dust vacuuming perforations are omitted. For some applications, it may be desirable to enhance the abrading power in a peripheral area of an abrasive surface by forming an area having fewer, or even no perforations, in the peripheral area.

Attachment of Backup Pad, Intermediate Pad and Abrasive Material in Dust Vacuuming Sanding Apparatus

The back surface of the backup pad is attached to the shaft of the air-powered motor, and the back surface of the abrasive material is removably attached to the supporting surface of the backup pad, and thereby, the dust vacuuming sander apparatus of the present invention is obtained. In the case where the intermediate pad is employed, the back surface of the backup pad is attached to the shaft of the air-powered motor, the back surface of the intermediate pad is removably attached on the supporting surface of the backup pad, and the back surface of the abrasive material is removably attached on the supporting surface of the intermediate pad, and thereby, the dust vacuuming sander apparatus of the present invention is obtained.

A conventional attachment means may be employed for attaching the backup pad or/and the intermediate pad, and the abrasive material to each other. Examples of preferred attachment means include 2-part hook and loop mechanical fasteners and adhesives. In the case where a 2-part hook and loop mechanical fastener is used, a clearance is created between the abrasive material and the backup pad, and this clearance functions as a channel for vacuuming abraded swarf, and therefore, the efficiency of dust vacuum can further be increased. The hook part of the mechanical fastener may be attached to either the rear surface of the abrasive material and the loop part of the mechanical fastener attached to the supporting surface of the backup pad, or vice versa The height of the clearance may be adjusted using the height of the loops, and it is not smaller than 0.5 mm, preferably not smaller than 1 mm to 2 mm, in order to make it function as a channel for vacuuming dust.

Method for Using Dust Vacuuming Sander Apparatus

The dust vacuuming sander apparatus of the present invention is particularly useful for carrying out, for example, the steps of feather edging, body filler sanding and scuffing of automobile body panels. They are preferably employed in combination with the backup pad having the perforation structure as shown in Fig. 8 and the abrasive material having the perforation structure as shown in Fig. 14. The abrasive materials having abrasive particles in an average particle size of 50 μm (JIS P240) to 200 μm (JIS P80) are preferably employed for the feather edging step, the abrasive materials having abrasive particles in an average particle size of 40 μm (JIS P320) to 400 μm (JIS P40) are preferably employed for the body filler sanding step, and the abrasive materials having abrasive particles in an average particle size of 10 μm (JIS P2000) to 80 μm (JIS P 180) are preferably employed for the scuffing step.

In the scuffing step, the intermediate pad having the perforation structure as shown in Fig. 14 may additionally be employed in combination. In that case, the abrasive materials having abrasive particles in an average particle size of 5 μm (JIS P3000) to 80 μm (JIS P 180) are preferably employed.

While the present invention is specifically described using the following examples, it should be understood that such examples do not limit the scope of this invention. . EXAMPLES

Example A

As shown in Fig. 4, a dust vacuuming sander in which the terminal of bypass means is connected to a vicinity of the air outlet of the air-powered motor chamber.

Subsequently, the dust vacuuming sander was powered by providing pressurized air to the air inlet tube at a pressure of 600 kPa and the rotational speed of the air-powered motor was adjusted to 5000 rpm by adjusting the valve 15. In this state, the negative pressure produced in the dust vacuuming path 13 was measured.

Subsequently, the rotational speed of the air-powered motor was adjusted to 9000 rpm by adjusting the valve 15. In this state, the negative pressure produced in the dust vacuuming path 13 was measured again. The results are shown in Table 1.

Comparative Example A

A conventional type of dust vacuuming sander was prepared which had a structure the same as that of the dust vacuuming sander of the Example except having no bypass means. The negative pressure produced in the dust vacuuming path 13 was measured at two different rotational speeds in the same manner as Example except for using this conventional type of dust vacuuming sander. The results are shown in Table 1. Table 1

Negative pressure produced in dust- vacuuming path 13

The dust- vacuuming sander of the present invention is able to produce approximately constant negative pressure in the dust vacuum path by operating the valve 15, independent of rotational speed of the air-powered motor.

Example B

A hook material of a mechanical fastener was attached to the supporting surface, and a bolt for attaching to the air-powered motor in the dust vacuuming sander was attached to the back surface, of a commercially available solid (non-perforated) backup pad having a diameter of 125 mm. Perforations were then formed in this pad material to form a perforated structure, and thus a backup pad was obtained.

A lO mm-thick foam sheet was punched into a circle 125 mm in diameter. A hook material of a mechanical fastener was attached to the supporting surface of the resultant foam disc and a loop material of the mechanical fastener was attached to the back surface. Perforations were formed in the disc material to form a perforation structure, and thus an intermediate pad was obtained.

A nylon pile loop material of a mechanical fastener was attached to the back surface of an abrasive material "Disc Unicut P400" having a diameter of 125 mm, made by Sumitomo 3M Ltd. Perforations were formed in the abrasive material to form a perforation structure, and thus, an abrasive material in disk form was obtained. The perforation structures for the backup pad, the intermediate pad and the abrasive material in disk form were the three types (7 perforations, 49 perforations, and 61 perforations) as shown in Fig. 15.

A dust vacuuming sander apparatus was constructed by attaching the backup pad, the intermediate pad and the abrasive material in disk form to the dust vacuuming sander (double action type) of Example A. The perforation structures employed for the examples were shown in Table 3.

Sanding test was carried out under the conditions shown Table 2, and the quantities of workpiece abraded and dust vacuumed, were determined. The results were shown in Table 3.

Table 2

Comparative Example B

A dust vacuuming sander apparatus was constructed according to the manner as described in Example B except that DUST VACUUMING TYPE DOUBLE ACTION SANDER SI3111 (made by Shinano Inc.) was employed instead of the dust vacuuming sander of Example A. The results are shown in Table 3. Table 3

^DThe abrasive performance was shown under that the amounts determined in Comparative Example Bl are 100%.

The dust vacuuming sander apparatus of the present invention showed far excellent cutting ability and dust vacuuming ability even when the perforated structure in the abrasive material was not the same as the perforated structure in the backup pad.

Claims

1. A dust vacuuming sander, comprising: a housing defining the outer shape of the dust vacuuming sander, the housing having a shroud, an air-powered motor housed within the housing, an air inlet tube for supplying pressurized air to the air-powered motor, an air exhaust tube for exhausting the pressurized air downstream of the air-powered motor, a venturi tube having an inlet opposed with an outlet of the air exhaust tube via a gap, a bypass means, wherein the bypass means separates a portion of the pressurized air from the air inlet tube and recombines it downstream of the air-powered motor.

2. The dust vacuuming sander according to claim 1 further comprising a valve for adjusting the rate of air flow which passes through the bypass means.

3. The dust vacuuming sander according to claim 1, wherein a terminal point of the bypass means is connected to an air-powered motor chamber and wherein the air which bypassed the air-powered motor and the air which passed through the air-powered motor join together at a vicinity of the air outlet inside the air-powered motor chamber.

4. The dust vacuuming sander according to claim 1 or 2, wherein when the air which bypassed the air-powered motor and the air which passed through the air-powered motor join together, the flow direction of the former air and that of the latter air intersect at an angle of 90° or smaller.

5. The dust vacuuming sander according to claim 1 or 2, wherein when the air which bypassed the air-powered motor and the air which passed through the air-powered motor join together, the flow direction of the former air and that of the latter air intersect at an angle of 45° or smaller.

6. A dust vacuuming sander apparatus comprising the dust vacuuming sander according to any one of claims 1 to 5, a pad, and an abrasive material, wherein the pad is a backup pad, the backup pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the shaft of the air-powered motor; and the abrasive material having an abrasive surface, a back surface and perforations penetrating from the abrasive surface through the back surface, the back surface of which is removably attached to the supporting surface of the backup pad.

7. A dust vacuuming sander apparatus comprising the dust vacuuming sander according to any one of claims 1 to 5, a pad, and an abrasive material, wherein the pad is composed of a backup pad and an intermediate pad, the backup pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the shaft of the air-powered motor; the intermediate pad having a supporting surface, a back surface and perforations penetrating from the supporting surface through the back surface, the back surface of which is removably attached to the supporting surface of the back up pad; and the abrasive material having an abrasive surface, a back surface and perforations penetrating from the abrasive surface through the back surface, the back surface of which is removably attached to the supporting surface of the intermediate pad.

8. A method of dust vacuum sanding a workpiece, comprising: providing a dust vacuuming sander apparatus of claim 6 or claim 7, providing a supply of pressurized air to the air inlet, separating a portion of the pressurized air via the bypass means, rotating the air-powered motor by means of the remaining pressurized air, applying the rotating abrasive surface to a workpiece, and recombining the separated pressurized air downstream of the air-powered motor, wherein the negative pressure generated in the shroud vacuums the sanding dust, the sanding dust removed from the housing via the venture tube.