EP3437800B1

EP3437800B1 - Supporting device for abrasive elements

Info

Publication number: EP3437800B1
Application number: EP18186181.6A
Authority: EP
Inventors: Claudio Mazzolini
Original assignee: Abrex-System Srl
Current assignee: Abrex-System Srl
Priority date: 2017-07-31
Filing date: 2018-07-27
Publication date: 2020-04-15
Anticipated expiration: 2038-07-27
Also published as: EP3437800A1; PT3437800T; ES2805076T3; IT201700087962A1

Description

The invention relates to supporting devices for abrasive elements to be mounted on orbital or random orbital sender machines. In particular, the invention relates to a supporting device, so called backing pad, adapted to support an abrasive-material disc and coupleable to a tool machine which makes it rotate. Such a supporting device is for example disclosed in Document WO2015119521 A1 , on which the preamble of claim 1 is based.
Known supporting devices or backing pads typically comprise a generally disc-shaped supporting body made of plastics or metal material and a connecting element, disc-shaped too, fixed to a lower face of the body and made of a yielding and elastic material, generally an elastomeric material or alike. An abrasive-material disc is removably fixed to the connecting element, for instance by means of a repositionable adhesive or glue or by means of a hooking system of the Velcro® type or alike. A coupling element, typically a pin, is provided on the upper face of the supporting body for connecting a rotation chuck of the sander machine.
In order to allow the sander machine to suction dust generated during the operations of abrasion, sanding, grinding of pieces/parts being processed, the backing pad and the abrasive disc are provided with a plurality of through holes. More precisely, the body and the connecting element are provided with a variable number of through holes, six or more, arranged circumferentially about a rotation axis of the backing pad and having also different sizes. For proper passage of air and sucked dusts, the through holes of the body and the fixing element are aligned and coaxial. For the same reason, also the through holes provided on the abrasive disc must coincide with the backing pad ones. The backing pad through holes come out on the upper face of the body at and inside a suction sleeve of the sander machine, such sleeve surrounding the rotation chuck and forming an internal chamber connected to a suction system.
Air suction also allows to cool the abrasive disc which can reach high temperatures during the usage.
A disadvantage of the known backing pads is that for a correct dust suction the abrasive disc should be mounted in such a way that its holes are aligned and coincide with the backing pad ones. However while in use, due to mechanical stresses, the abrasive disc may move and rotate modifying the alignment of the holes.
The through holes made in the backing pad do not allow to cool the latter efficiently. In an intensive use of the backing pad the temperature increase may compromise the connection between the body and the connecting element, even resulting in the detachment thereof. The connection between the two parts is in fact generally carried out by means of glues and abrasive adhesives, which can deteriorate at high temperatures. High temperatures can further damage also the abrasive disc material or limit the duration and/or the performance thereof.
Another drawback is that through holes can be made only in the central part of the backing pad so as to be engaged by the normal suction sleeves mounted on sander machines. Therefore, the peripheral areas or crowns of the backing pad and abrasive disc cannot be provided with holes for suctioning dust and for cooling, unless suction sleeves with larger size, consequently more expensive and hindering, are installed on the sander machines. Furthermore, in case abrasive discs with different hole configurations (number, sizes, arrangements) are to be used, for example to perform specific operations, it is necessary to use specific backing pads provided with a supporting body and a connecting element having corresponding hole geometries, with resulting increase of production and storage costs.
In order to overcome some of the aforementioned disadvantages, supporting devices or backing pads were made provided with an inner chamber for the passage of air and sucked dust. More precisely, the backing pad body has an upper portion provided with a cavity and a disc-shaped lower portion which closes the cavity such as to form the inner chamber. The lower disc may be holed even at one of its peripheral crowns similarly to the yielding connecting element fixed thereto for the support of the abrasive disc. In contrast, the upper portion of the body has a plurality of through holes at its central portion for being connected to a standard suction sleeve of the sander machines. Thereby it is possible to suction air on the whole abrasive disc surface with no need to use increased suction sleeves.
A disadvantage of such backing pads is that in use the peripheral annular portion of the inner chamber tends to shut due to dust accumulation: suctioned air in fact tends to pass mainly through the lower disc holes and the inner chamber portion which face the outlet holes made in the central portion of the upper portion of the body, also because the height or thickness of the inner chamber is necessarily limited. As a matter of fact, in order not to increase excessively the backing pad thickness, the chamber height must be reduced. As known, increase of the backing pad thickness implies increase of vibrations and oscillations thereof during usage, i.e. less precision and efficiency in operations.
Another disadvantage of such kind of backing pad is that the body, being provided with such inner cavity (in particular its upper part provided with a wide cavity) is structurally less robust and strong than traditional backing pads, as well as the fixation of the lower disc holed in the upper part is less secure and robust.
Document WO 2011/021087 discloses a supporting device or backing pad for abrasive elements in form of sheets comprising a first disc-shaped body which has a rear surface arranged for the attachment to a tool machine and which is crossed in its thickness by first section openings intended to be connected to a suction device when in use. The backing pad comprises a second disc-shaped body associated to a front surface of the first body and which has a front surface substantially flat on which a flat abrasive element can be laid. The second body is crossed in its thickness by a plurality of second suction openings communicating with the first suction openings. The second suction openings are densely distributed substantially on the whole area of the front surface or at least on a portion thereof. The front surface face, in the portions without the second suction openings, has an outwardly open channel of the second disc-shaped body and communicating with the second suction openings.
Document WO 2015/119521 discloses a backing pad with slots for sanding discs with multiple holes, comprising un upper portion, an intermediate portion and a lower portion joined between them by a fixing system. The upper portion, with truncated-cone shape, comprises suction holes and a central hole. The intermediate portion comprises suction slots and a central hole and it is provided in its rear face with suction channels delimited by raised walls. The lower portion, with truncated-cone shape, and wherein the intermediate portion is mounted, comprises slots, a central hole and suction slots arranged in concentric and equidistant rings and with a size increasing from the centre to the periphery. Document WO2012/019286 discloses a supporting device or backing pad for use with a surface treatment apparatus which includes a support plate having a fixing plate for a buffer and a support buffer having a first face and a second face. The supporting device can also include a porous interface layer provided with an external face. A layer of a first adhesive is arranged on the external face and extends into the interface layer and a layer of a second adhesive is applied on the layer of the first adhesive. The second adhesive may be selected to releasably bond with an abrasive sheet. The first and second adhesive may be selected such that the adhesive bond between the first adhesive and the second adhesive is stronger than the adhesive bond between the second adhesive and the abrasive sheet.
An object of the invention is improving known supporting devices or backing pads for abrasive elements to be mounted on orbital or random orbital sander machines.
Another object is providing a supporting device which allows to efficiently and effectively suction dust generated during abrasion, sanding, grinding operations and in the meantime cooling optimally the device body and above all the abrasive element.
A further object is implementing a supporting device which can be easily configured while being assembled for coupling with different types of abrasive elements and having in particular different hole configurations (number, size, arrangements).
Still another object is providing a particularly robust and strong supporting device even for intensive use.
Another further object is implementing a supporting device which can be used efficiently and high-performing on sander machines provided with standard suction sleeves.
These and other objects are obtained by a supporting device for abrasive elements according to one or more of the following claims.
The invention shall be better understood and implemented referring to the enclosed drawings showing an exemplary and non-limiting embodiment, wherein:

figure 1 is a plan view from above of the supporting device of the invention;
figure 2 is a section according to line II of figure 1 illustrating the supporting device of the invention associated to a suction sleeve of a sander machine, represented by a dotted line;
figure 3 is an enlarged detail of the device of figure 1 associated to an abrasive element;
figure 4 is a plan view from below of the device of figure 1 without a connecting element for the abrasive element, to better highlight an underlying support element and closing element;
figure 5 is a plan view from below of the supporting body of the device of figure 1;
figure 6 is a plan view of the closing element;
figure 7 is a perspective view of the supporting body of figure 5;
figure 8 is a schematic side view of the supporting device mounted on a sander machine and supporting an abrasive element;
figure 9 is a section according to line IX-IX of figure 5.

Referring to figures 1 to 8, it is illustrated a supporting device 1 of the invention suitable to support an abrasive element 30 and associable with an orbital or random orbital sander machine 50, of the type used to perform sanding, milling, abrasion, polishing processing on surfaces and objects.
More precisely, the supporting device 1, also called backing pad, includes a supporting body 2 comprising an external face 21 and a central part 3 provided with a series of first through holes 11, and a connecting element 6 fixed to the supporting body 2 and arranged to support the abrasive element 30. The connecting element 6 comprises a central portion 7 provided with a series of second through holes 12 facing the series of first through holes 11 of the supporting body 2. The latter also comprises an annular cavity 5 made in a peripheral part 4 of the aforesaid supporting body 2, in particular on a inner face 22 opposite to the external face 21, and around the central part 3. The annular cavity 5 is provided with a series of third through holes 13 coming out at the external face 21.
The backing pad 1 further comprises a closing element 10 that coupleable to the supporting body 2 such as to close the annular cavity 5 and form an inner annular chamber 16. The closing element 10 is provided with a series of fourth through holes 14 facing a series of fifth through holes 15 made on a peripheral annular portion 8 of the connecting element 6. The first through holes 11 and the third through holes 13 of the supporting body 2 come out at a coupling portion 21a of the external face 21 of the latter arranged to engage to an air and dust suction system of the sander machine 50. More precisely and as shown in figure 2 , the coupling portion 21a is inside a suction chamber 52 formed with the same supporting body 2 by a suction hood 51 of the sanding air and sanding dust suction system of the sander machine 50.
As illustrated in figure 3, the abrasive element 30 comprises at least a series of sixth through holes 31 and a series of seventh through holes 32 almost corresponding and aligned respectively to second through holes 12 and fourth through holes 14 of the connecting element 6.
The supporting body 2 and the closing element 10 are made of plastics, in particular of high-density plastics.
The connecting element 6 is on the contrary made of yielding and flexible material, for example elastomeric material, in particular rubber, for elastically supporting the abrasive element while it is being adapted to the shape of the surface to be processed.
The connecting element 6, in addition to being fixed to the inner face 22 of the supporting body 2 is also fixed to the closing element 10. Fixing is made with means of the known type, such as for example glues or adhesives or by means of ultrasound welding.
The first through holes 11 of the supporting body 2 and the second through holes 12 of the connecting element 6 are almost aligned and coaxial to ensure an excellent passage of air and dust sucked by the suction system of the sander machine 50 while in use, as better explained in the hereinafter description.
The first through holes 11 and the second through holes 12 thus form a first suction central path for air and sanding dust at a central portion of the backing pad 1 and of the abrasive element 30.
As illustrated in particular in figure 9, in order to allow a more efficient suction and consequently a more rapid removal of sanding dust within the suction hood 51 of the sander, the first through holes 11 are conical, and in particular divergent, that is with an increasing transverse section, directed towards the external face 21. Such conicity of the fist through holes 11 allows in fact an increase of air suction speed.
It is also provided, in one variant of the supporting device 1 non illustrated in the figures, that the first through holes 11 are almost cylindrical.
The fourth through holes 14 of the closing element 10 and the fifth through holes 15 of the connecting element 6 are themselves preferably almost substantially aligned or coaxial. The third, fourth and fifth through holes 13, 14, 15 along with the inner peripheral chamber 16 form a peripheral path of air and dust suction at a peripheral portion of the backing pad 1 and of the abrasive element 30.
In the illustrated embodiment each series of through holes 11, 12, 13, 14, 15 each comprises a plurality of respective through holes having a same respective shape and size, in particular same circular shape and same diameter. It is however possible that each series of through holes comprises through holes having different sizes and/or shapes (circular, elliptical,...).
Each series of through holes further comprises a respective number of holes (equal or different) arranged according to an arrangement or distribution adapted to secure an optimal flow of air and sanding dust being sucked without compromising in any case the mechanical strength and hardness of the various components, that is of the supporting body 2, of the connecting element 6 and of the closing element 10.
In the illustrated embodiment the third through holes 13 are arranged along a circumference around the central portion 3 and are greater in size than the first holes 11 in order to increase suction and the passage of air and dust through the inner chamber 16, as better explained in the hereinafter description.
The closing element 10 can be selected in a group of closing elements having different configurations of the fourth through holes 14 and can be coupled to the supporting body 2 according to features and configurations of the through holes of the abrasive element 30 to be used. The latter, of the known type and not described in detail, generally comprises an abrasive-material disc provided with a plurality of through holes of equal or different sizes and arranged such as to ensure the best suction of dusts generated during processing.
In the illustrated embodiment the supporting body 2 has a disc shape which is almost circular, in particular axial-symmetrical with respect to the central axis X about which the whole backing pad 1 rotates when it is connected and moved by the sander machine 50. The supporting body 2 further has a decreasing thickness starting from the central part 3 and towards the peripheral part 4. Referring to the section of figure 2 the annular cavity 5 has an elongated rectangular-shaped section and has an inner shoulder 25 and an external shoulder 24, both of them circular-shaped, adapted to receive and support the closing element 10. The latter has flat and annular shape, in particular circular crown shape.
In order to support and allow a more stable connection of the closing element 10 to the supporting body 2, the annular cavity 5 comprises a plurality of support pins 27 arranged around the central part 3. More precisely, each support pin 27 has a tapered end 27a arranged for engaging a respective fourth through hole 14 of the closing element 10. The portion of the tapered end 27a coming out from the hole of the closing element 10 can be rebutted or plastically deformed such as to tightly block the closing element 10 to the supporting body 2, in one assembly step of the backing pad 1.
Referring in particular to figure 7, the supporting body 2 comprises on its inner face 22 opposite to the external face 21 and at the central part 3 a further cavity 9 which is in flow connection with the external face 21 by means of a plurality of slots 17 and respective through openings 18, 19, these latter in particular coming out at the coupling portion 21a of the external face 21. The further cavity 9 is faced and connected to a central hole 26 of the connecting element 6. Thanks to the aforesaid central hole 26 and the further cavity 9 connected to the coupling portion 21a by means of a plurality of through openings 18, 19 it is possible to efficiently suction the majority of dust accumulating on the abrasive element 30 and on the backing pad 1 in the area adjacent and around the central axis X at which the peripheral speeds (which tangentially push dust outside of the backing pad) are almost void.
In the illustrated embodiment, the further cavity 9 is connected to the external face 21 by means of four holes 17 and four respective first through openings 18, arranged spaced apart angularly about the central axis X. Four second through openings 19, each of which is made adjacent to a respective slot 17, connect directly a bottom wall 9a of the further cavity 9 to the external face 21.
First and second through openings 18, 19 and the further cavity 9 of the supporting body 2 and the central hole 26 of the connecting element 6 form a second central air and dust suction path at the central portion of the backing pad 1 and of the abrasive element 30, in particular about the central axis X.
The further cavity 9 further comprises a central opening 29 for coupling the backing pad to the sander machine 50, in particular by coupling means 20. The central opening 29 is for example a respective circular hole made on the bottom hole 9a of the additional cavity almost coaxial to the central axis X and coming out on the external face 21.
In the illustrated embodiment, the packing pad 1 comprises coupling means 20 which allow to reversibly couple the backing pad thereof to the sander machine 50. Coupling means comprise, in particular, a pin 20 fixed to the central part 3 of the supporting body 2, extending from the external face 21 and arranged for engaging to chuck means of the sander machine 50. More precisely, the pin 20 is inserted in the central opening 29 and has a shaped head 20a which is fitted and fixed in the further cavity 9.
Fixing means of the known type are provided to join the abrasive element 30 to the connecting element 6, the aforementioned fixing means comprising for example adhesives or reversible hooking systems of Velcro ® type.
In use, the backing pad 1 of the invention bearing an abrasive element 30 fixed to the connecting element 6 is rotated about the central axis X of the sander machine 50 onto which it is mounted. The depression created in the suction chamber 52, formed by the suction hood 51 with the upper face 21 of the supporting body 2, determines suction of air and above all of dust made during use. Thanks to the backing pad 1 structure of the invention, air and sanding dust are efficiently suctioned and removed by the abrasive element 30 both in one of its central portion and in one of its peripheral portion. More precisely, the first through holes 11 of the supporting body 2 and second through holes 12 of the connecting element 6 form a first central path for the passage of air and dust, at the central part 3 of the supporting body 2. The sanding dust extraction in the central portion of the backing pad 1 is eased by the conicity of the first through holes 11 which allows an increase in air suction speed.
Dust extraction is further eased by the through openings 18, 19 and by the further cavity 9 of the supporting body 2 and by the central hole 26 of the connecting element 6 which form the second central suction path always at the central portion of the backing pad 1 and of the abrasive element 30, in particular around the central axis X, i.e. in the area where there is the majority of dust accumulation.
Dust suction and removal from the peripheral portion of the backing pad 1 and of the abrasive element 30 is on the contrary efficiently carried out by the third through holes 13, by the inner peripheral chamber 16 of the supporting body 2, by the fourth through holes 14 of the closing elements 10 and by the fifth through holes 15 of the connecting element 6.
Thereby, thanks to the presence of three different and separated suction paths (two central and one peripheral) it is possible to optimally extract dust during processing. Furthermore, unlike known supporting devices or backing pads, the inner peripheral chamber, being provided with respective and separate through holes (series of third through holes 13) which make it communicate with the suction chamber 52 formed by the suction sleeve 51 of the sander machine 50, is subject to a constant suction flow and it is not subject to blockages or obstructions caused by dust accumulation.
The closing element 10 also advantageously contributes to such a result as it can be selected with a suitable configuration of the fourth through holes 14 such as to make the backing pad 1 suitable for a specific type of abrasive element 30 and/or of operative conditions. In particular, the closing element 10 can be selected during the assembly of the backing pad 1 according to the physical-chemical characteristics of the abrasive element and/or of its through holes configuration (number, size, arrangement).
The optimal air suction through the backing pad 1 of the invention also allows to cool the latter efficiently and in particular the abrasive element 30 such as to avoid damage to the material it is made of and increase the duration and/or the performance thereof.
It is also worth noting that the backing pad 1 of the invention, though having an inner peripheral chamber 16 and a plurality of through holes, is particularly strong and robust as it comprises a supporting body 2 made of a single piece and having a peripheral portion 4 and above all a central portion 3 arranged about the central axis X which the connecting element 6 is directly fixed with. The closing element 4 coupled and fixed to the inner face 22 of the supporting body 2 for forming the inner peripheral chamber 16 contributes to reinforce the backing pad structure 1.
Finally, it must be noted that, as holes and through holes made on the supporting body 2 all come out at a coupling portion 21a of the external face 21 of said supporting body 2 having limited sizes, the backing pad 1 of the invention can be efficiently used and high-performing on sander machines provided with standard suction sleeves and not with the enlarged type.

Claims

Supporting device (1) that is suitable to support an abrasive element (30) and associable with an orbital or random orbital sander machine (50), including:
- a supporting body (2) comprising an external face (21) and a central part (3) provided with a series of first through holes (11);

- a connecting element (6) fixed to said supporting body (2) and arranged to support said abrasive element (30), said connecting element (6) comprising a central portion (7) provided with a series of second through holes (12) facing said series of first through holes (11);

- a closing element (10);
characterized in that said supporting body (2) comprises an annular cavity (5) made in a peripheral part (4) of said supporting body (2) around said central part (3) and provided with a series of third through holes (13), wherein the closing element (10) is coupleable to said supporting body (2) so as to close said annular cavity (5) and form an inner annular chamber (16), said closing element (10) being provided with a series of fourth through holes (14) facing a series of fifth through holes (15) made on a peripheral annular portion (8) of said connecting element (6), said first through holes (11) and said third through holes (13) of said supporting body (2) coming out at a coupling portion (21a) of said external face (21) that is suitable to engage an air and sanding dust suction system of said sander machine (50).
Supporting device (1) according to claim 1, wherein said first through holes (11) of said supporting body (2) and said second through holes (12) of said connecting element (6) are almost aligned.
Supporting device (1) according to claim 1 or 2, wherein said first through holes (11) are conical, in particular divergent towards said external face (21).
Supporting device (1) according to any preceding claim, wherein said fourth through holes (14) of said closing element (10) and said fifth through holes (15) of said connecting element (6) are almost aligned.
Supporting device (1) according to any preceding claim, wherein said closing element (10) is selectable in a group of closing elements having different configurations of fourth through holes (14) and is connectable to said supporting body (2) according to features and configuration of through holes of said abrasive element (30) to be used.
Supporting device (1) according to any preceding claim, wherein said annular cavity (5) has an inner shoulder (25) and an external shoulder (24) arranged to receive and support said closing element (10).
Supporting device (1) according to any preceding claim, wherein said annular cavity (5) comprises a plurality of supporting pins (27) arranged around said central part (3) to support said closing element (10), in particular each supporting pin (27) having a tapered end (27a) arranged to engage a respective fourth through hole (14) of said closing element (10).
Supporting device (1) according to any preceding claim, wherein said supporting body (2) comprises an inner face (22) opposite to said external face (21) and a further cavity (9) made on said inner face (22) at said central part (3), said further cavity (9) being connected with said external face (21) by means of a plurality of slots (17) and respective through openings (18, 19) which come out at said coupling portion (21a) of said external face (21), said further cavity (9) facing and being connected to a central hole (26) of said connecting element (6).
Supporting device (1) according to claim 8, wherein said further cavity (9) comprises a central opening (29) for the coupling to said sander machine (50), in particular by coupling means (20).
Supporting device (1) according to any preceding claim, comprising coupling means (20) for reversibly coupling said supporting device (1) to said sander machine (50), said coupling means comprising a pin (20) that is fixed to said central part (3) of said supporting body (2), extends from said external face (21) of said supporting body (2) and is arranged to engage chuck means of said sander machine (50).
Supporting device (1) according to any preceding claim, wherein said supporting body (2) and said closing element (10) are made of plastics.
Supporting device (1) according to any preceding claim, wherein said connecting element (6) is also fixed to said closing element (10).
Supporting device (1) according to any preceding claim, comprising fixing means for joining said abrasive element (30) to said connecting element (6), said abrasive element (30) comprising at least a series of sixth through holes (31) and a series of seventh through holes (32) almost corresponding respectively to said second through holes (12) and to said fifth through holes (15) of said connecting element (6).