Flexible sanding disc unit
United States Patent 3875703
A flexible adapter unit is used in mounting a flexible abrasive disc to the surface of a motorized rotary operator such as is commonly used in relatively light sanding operations. As sold, the unit is a package-like lamination of three discs adhesively secured in a stack, namely a basic intermediate membrane disc bearing a pressure-sensitive coating on each of the opposite sides thereof, and a pair of thin outer strippable protective cover members, one adhered releasably on either side of the membrane. Said last-named members are thin flexible discs, each preferably being wax or otherwise coated on an inner side thereof to present a somewhat glossy, entirely non-tacky surface adherently engaging a membrane surface coating. The intermediate membrane disc is also flexible, and may vary considerably as to material; and it is coated on its opposite sides with pressure-sensitive adhesive layers. These, though by preference being in common of a known latex composition, yet vary considerably in an operational characteristic of said composition. That is, one of said coatings or layers, as applied in use to a rotary tool surface, is a relatively heavy one having a relatively high degree of tacky adhesiveness, so as to adhere tightly to the tool surface as so applied, yet being removably strippable manually from said surface. The other or outer adhesive layer is lighter and substantially less tacky adhesively, yet sufficiently so to have ready pressed-on engagement with the non-abrasive rear side of a sanding disc, while still allowing the latter to be readily stripped from the membrane disc and discarded when worn.
US Patent References:
Sanding disk accessory
O'Neil - July 1953 - 2644280
/2732065.html
Merchese - January 1956 - 2732065
Power-driven hand tool
Wickes - June 1957 - 2794303
Sanding disk accessory
O'Neil - July 1953 - 2644280
/2732065.html
Merchese - January 1956 - 2732065
Power-driven hand tool
Wickes - June 1957 - 2794303
Application Number:
05/427849
Publication Date:
04/08/1975
Filing Date:
12/26/1973
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
451/538
International Classes:
B24D11/00; B24D13/14; B24D13/00; B24B23/00; B24D11/00
Field of Search:
51/17T,17MT,401,406,407
Primary Examiner:
Jones Jr., James L.
Attorney, Agent or Firm:
Whittemore, Hulbert & Belknap
Claims:
What is claimed is
1. A flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit consisting in its entirety of a temporary lamination of an intermediate flexible membrane of thin, substantially inelastic sheet material and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, and another and specifically different pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a readily releaseable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, the adhesive bond to said abrasive sheet effected by said first-named coating on the outer membrane surface being substantially less strong and more readily releasable than the bond of the inner membrane surface coating to said operator surface.
2. The adapter unit of claim 1, in which the membrane bonds to the respective strip sheets are weaker than either of the abrasive sheet and operator surface bonds.
3. The adapter unit of claim 1 as a circular disc unit applied in adhesive combination with a motor-driven operator presenting said first-named surface, with a protective sheet of the unit stripped from the inner membrane surface and that surface adhered to said first-named operator surface.
4. The adapter unit of claim 2 as a circular disc unit applied in adhesive combination with a motor-driven operator presenting said first-named surface, with a protective sheet of the unit stripped from the inner membrane surface and that surface adhered to said first-named operator surface.
5. The combination of a unit in accordance with claim 1 as stripped of one of said protective sheets to expose said inner coated membrane surface, and a backing member to which said membrane is adherently secured at said inner surface thereof.
6. The combination of a unit in accordance with claim 1 as stripped of both of said protective sheets to expose said inner and outer coated membrane surfaces, a backing member to which said membrane is adherently secured at said inner surface thereof, and an abrasive sheet releasably secured adherently to said outer coated surface of said membrane.
7. The combination of claim 5, in which said backing member is a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond.
8. The combination of claim 6, in which said backing member is a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond.
9. The combination of a flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit comprising a temporary lamination of an intermediate flexible membrane and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, another pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a releasable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, said unit being adapted to be stripped of one of said protective sheets to expose said inner coated membrane surface, a backing member to which said membrane is adherently secured at said inner surface thereof, said backing member being a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond, the yieldable facing of said backing member comprising a foamed layer having a flexible facing sheet permanently secured on an outer surface, and a relatively rigid support member to which an inner surface of said foamed layer is relatively permanently secured.
10. The combination of a flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit comprising a temporary lamination of an intermediate flexible membrane and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, another pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a releasable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, said unit being adapted to be stripped of both of said protective sheets to expose said inner and outer coated membrane surfaces, a backing member to which said membrane is adherently secured at said inner surface thereof, an abrasive sheet releasably secured adherently to said outer coated surface of said membrane, said backing member being a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond, the yieldable facing of said backing member comprising a foamed layer having a flexible facing sheet permanently secured on an outer surface, and a relatively rigid support member to which an inner surface of said foamed layer is relatively permanently secured.
1. A flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit consisting in its entirety of a temporary lamination of an intermediate flexible membrane of thin, substantially inelastic sheet material and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, and another and specifically different pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a readily releaseable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, the adhesive bond to said abrasive sheet effected by said first-named coating on the outer membrane surface being substantially less strong and more readily releasable than the bond of the inner membrane surface coating to said operator surface.
2. The adapter unit of claim 1, in which the membrane bonds to the respective strip sheets are weaker than either of the abrasive sheet and operator surface bonds.
3. The adapter unit of claim 1 as a circular disc unit applied in adhesive combination with a motor-driven operator presenting said first-named surface, with a protective sheet of the unit stripped from the inner membrane surface and that surface adhered to said first-named operator surface.
4. The adapter unit of claim 2 as a circular disc unit applied in adhesive combination with a motor-driven operator presenting said first-named surface, with a protective sheet of the unit stripped from the inner membrane surface and that surface adhered to said first-named operator surface.
5. The combination of a unit in accordance with claim 1 as stripped of one of said protective sheets to expose said inner coated membrane surface, and a backing member to which said membrane is adherently secured at said inner surface thereof.
6. The combination of a unit in accordance with claim 1 as stripped of both of said protective sheets to expose said inner and outer coated membrane surfaces, a backing member to which said membrane is adherently secured at said inner surface thereof, and an abrasive sheet releasably secured adherently to said outer coated surface of said membrane.
7. The combination of claim 5, in which said backing member is a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond.
8. The combination of claim 6, in which said backing member is a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond.
9. The combination of a flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit comprising a temporary lamination of an intermediate flexible membrane and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, another pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a releasable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, said unit being adapted to be stripped of one of said protective sheets to expose said inner coated membrane surface, a backing member to which said membrane is adherently secured at said inner surface thereof, said backing member being a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond, the yieldable facing of said backing member comprising a foamed layer having a flexible facing sheet permanently secured on an outer surface, and a relatively rigid support member to which an inner surface of said foamed layer is relatively permanently secured.
10. The combination of a flexible adapter unit for mounting an abrasive sheet on a surface of an operator for said sheet, said unit comprising a temporary lamination of an intermediate flexible membrane and a pair of flexible protective strip sheets having temporarily-adhered application respectively to inner and outer surfaces of said membrane, said application being through the agency of a pressure-sensitive adhesive coating pre-applied on the inner membrane surface, which coating when exposed and pressure-applied on said operator surface has a relatively strong but releasable bond to that surface, another pressure-sensitive adhesive coating pre-applied on the outer membrane surface, which last-named coating when exposed and pressure-applied to the abrasive sheet has a releasable bond to said abrasive sheet, the respective protective strip sheets being relatively readily peeled from said respective membrane coatings, said unit being adapted to be stripped of both of said protective sheets to expose said inner and outer coated membrane surfaces, a backing member to which said membrane is adherently secured at said inner surface thereof, an abrasive sheet releasably secured adherently to said outer coated surface of said membrane, said backing member being a yieldably faced one, at the facing of which said inner membrane coating has a relatively strong but releasable bond, the yieldable facing of said backing member comprising a foamed layer having a flexible facing sheet permanently secured on an outer surface, and a relatively rigid support member to which an inner surface of said foamed layer is relatively permanently secured.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The sanding adapter lends itself to any application heretofore open to the use of removable or removably strippable sanding or like abrasive members, in particular in rotary disc sanders usually employed manually.
2. Description of the Prior Art
In the past, in applications generally similar to that of the present invention, a sandpaper sheet, disc or like flexible abrasive unit has been removably mounted on the surface of a compressible cushioned rotor pad, or equivalent backing member, by simply applying fluid adhesive to the face of the pad and pressing a sandpaper sheet, disc or the like onto the adhesive-coated surface. In applications in which the backing surface is afforded directly by an inflexible disc, this has in the past been coated with an appropriate mastic composition softened under frictional heat, with the abrasive disc pressed thereto before it takes a set. Said conventional procedures are fairly inexpensive material-wise, but over the long run of replacements of worn abrasive sheets are inconvenient and time-wasting.
According to an earlier improvement on the procedure first described above, sandpaper discs have been sold with a pre-applied pressure sensitive adhesive on the non-abrasive side, that coating being protected prior to sale and use by an appropriate slip or strip sheet cover, to be peeled away and discarded before pressure-applying the sandpaper disc against a cushioning pad or other abrasive-mounting surface of the tool. This improvement is, of course, more expensive than the case of a plain sandpaper disc, the number of replacement pieces being assumedly the same in each instance.
SUMMARY OF THE INVENTION
The invention is a substantial improvement over both of the above prior art concepts in its use of a single flexible membrane which in operation is interposed between a tool pad, cushion or equivalent backing surface and a sandpaper or other flexible abrasive disc as mounted on said surface by the membrane. The invention in particular distinguishes over and improves on prior expedients in that the special membrane is protected prior to sale and/or use between a pair of like thin external strip discs or sheets. These serve as protective covers in the handling of the unit, said discs preferably having an inner non-tacky slip coat of clear wax-like or varnish-like material. This facilitates their stripping by peeling from the surfaces of the basic intermediate membrane, the latter as distinctively coated pressure-sensitively in the manner described in the Abstract.
The pad component of the compressively mounted combination may be permanently supported on a relatively rigid backing plate of metal or plastic, the pad comprising a vinyl or leather-like facing to which the membrane is adherently mounted, and a vinyl foam cushion part between said facing and the backing plate. The cushion is secured relatively permanently to the plate and the facing is secured equally permanently to the foam, as by a pressure bonded or contact cement. Said vinyl facing preferably carries a slip coat of varnish or varnish-like material to enable it to stick moderately strongly to the membrane's inner, heavier strength pressure-sensitive adhesive without, however, any likelihood of the membrane being dislodged from the backing pad under severe sanding.
The membrane may be of any appropriate grade of fiberboard or heavy paper material, but of whatever stock the membrane may be comprised, it should not tear readily, particularly in active abrading use; and with this in mind the membrane may also be of a textured fabric or woven cloth.
The ability in accordance with the invention to use plain unfaced and unprocessed sandpaper discs of course eliminates the cost factor in pre-coating each disc with a pressure-sensitive adhesive; a single coating of the inner tool-engaging surface of the membrane of the invention eliminates all of these costs. Likewise, a single coating of the external sanding disc-mounting surface of the membrane is all that is required in the successive use of a multiplicity of sandpaper discs of like or different grades, prior to their discard and replacement as they become worn and useless. The worn disc is simply stripped or peeled off the membrane, which remains in place on the tool pad or other mounting part with both of its pressure-sensitive coatings intact.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an end face elevation of a package-type lamination of special membrane and protective cover components, the form in which the adapter unit is sold and handled prior to use, the view illustrating in a partially fanned arrangement inner and outer protective strip discs and the intermediate membrane disc of the combination, the latter as coated pressure-sensitively on its opposite side surfaces;
FIG. 2 is a view in transverse diametral section through the lamination of FIG. 1, being in an enlarged scale schematically distorted somewhat for clarity in thicknesses of constituent disc and coating components;
FIG. 3 is a substantially full scale perspective view of the laminated package unit of FIGS. 1 and 2 as stripped of its protective covers and applied to a sander disc base pad structure, being equipped with a sanding disc and with the latter and its supporting membrane shown partially peeled away from a supporting base pad; and
FIG. 4 is a side-elevational view, partially broken away, showing a typical application of the unit as backing pad-mounted for use on a conventional motorized hand sander.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIGS. 1 and 2 somewhat schematically show, and not in necessarily scaled relation of their parts, the adapter unit of the invention, generally designated by the reference numeral 10, in the package form in which it is merchandised, whether in an appropriate outer promotional envelope or not. This unit consists of the essentially important membrane sheet or disc 12, which may be optionally constituted by a ruggedly strong flexible paper in any desired thickness, or may be constituted of a flexible grade of paperboard, fiberboard, a woven fabric, or like substantially inelastic thin sheet material. The material of membrane 12 is susceptible of relatively wide choice, so long as it has adequate strength and/or toughness to resist the torsional stress to which it is subjected in use, without tearing free from a support pad or disc on the sanding tool.
As thus constituted, an inner or rear surface of membrane disc 12 is relatively heavily coated with a pressure-sensitive adhesive of the rubber latex type, such as is readily available on the market in different grades. This rear or inner coating of membrane 12 is indicated at 13, and it is selected and set to afford a relatively high degree of adhesive strength or tackiness when pressure-sensitive applied against a non-coated surface. The opposite outer or front surface of membrane disc 12 is, on the other hand, provided with a coating 14 of the same general latex type, but in a thickness and/or grade such as to present when set a substantially lesser degree of adhesive strength or tackiness than does the inner or rear coating 13.
Finally, the membrane is removably and adherently faced at its respective coatings 13 and 14 with relatively thin protective strip or cover sheets 15, 16. These are in the form of light-gauge paper discs which are treated only on their membrane-facing surfaces, as by an appropriate dried waxy or varnish-like application, to render them individually non-tacky, but still readily strippable by the fingers from the respective coated membrane surfaces of unit 10. When the discs 15, 16 are stripped from the membrane 12, the latter is applied removably and adherently as a part of a backing pad and abrasive disc lamination unit or combination. This combination, generally designated in FIGS. 3 and 4 by the reference numeral 17, presents a further novel and improved aspect of the invention.
Said laminated unit 17 comprises a more or less conventional sub-combination of a relatively rigid circular backing plate 18 of metal or plastic material equipped at a central cavity thereof with a cylindrical washer-like reinforcement 19 which presents a preferably integral rearwardly extending and exposed stem 20 at which the adapted sander disc unit 17 is chucked to an entirely conventional motorized sander 22. There is typically an eccentric mount of said unit to the head 23 of sander 22, so that the unit 17 has an orbital sanding action, as indicated by the double-headed arrow in FIG. 4. In some cases, the stem will be threaded, as at 20' (FIG. 4), for its removable mount to the tool 22. Of course, the operational nature of said tool is entirely optional; but a dual action air motor driven one typically appears in FIG. 4.
FIG. 3 shows the rigid backing plate 18 of unit 17 as having a relatively permanent bond at a forward interface surface 25 thereof with a vinyl foam cushion 26 of cylindrical form and substantial thickness; and the forward surface of this cushion is faced by a leather-like vinyl sheet 27 having relatively great strength in tension and torsion. By preference, the vinyl facing 27 is forwardly provided with a slip coat of a clear varnish or varnish-like material for an improved adherence thereto of membrane disc 12.
That disc is shown in FIG. 3 as having its high strength or tacky inner latex coating 13 removably adhered to the cushion pad facing 27, with its more lightly adherent coating 14, as stripped of the protective cover 16, exposed and adherently engaged by the plain rear surface of a conventional sanding disc 28.
As thus constituted, the backed membrane and pad unit is resistant to tear and to dislodgement from its pad component under relatively heavy duty sanding operation. Yet the relatively small degree of tackiness of forward surface 14 enables the sanding disc 28 to be marginally lifted from membrane coating 14 and peeled off the latter for replacement when worn with another abrasive disc; and the greater tackiness of rear membrane coating 13 is sufficient to resist its separation from cushion pad 26 in said replacement removal of the sanding disc, while at the same time enabling the membrane 12 itself to be similarly stripped along with the sandpaper from the facing 27 of the rotary tool mount.
1. Field of the Invention
The sanding adapter lends itself to any application heretofore open to the use of removable or removably strippable sanding or like abrasive members, in particular in rotary disc sanders usually employed manually.
2. Description of the Prior Art
In the past, in applications generally similar to that of the present invention, a sandpaper sheet, disc or like flexible abrasive unit has been removably mounted on the surface of a compressible cushioned rotor pad, or equivalent backing member, by simply applying fluid adhesive to the face of the pad and pressing a sandpaper sheet, disc or the like onto the adhesive-coated surface. In applications in which the backing surface is afforded directly by an inflexible disc, this has in the past been coated with an appropriate mastic composition softened under frictional heat, with the abrasive disc pressed thereto before it takes a set. Said conventional procedures are fairly inexpensive material-wise, but over the long run of replacements of worn abrasive sheets are inconvenient and time-wasting.
According to an earlier improvement on the procedure first described above, sandpaper discs have been sold with a pre-applied pressure sensitive adhesive on the non-abrasive side, that coating being protected prior to sale and use by an appropriate slip or strip sheet cover, to be peeled away and discarded before pressure-applying the sandpaper disc against a cushioning pad or other abrasive-mounting surface of the tool. This improvement is, of course, more expensive than the case of a plain sandpaper disc, the number of replacement pieces being assumedly the same in each instance.
SUMMARY OF THE INVENTION
The invention is a substantial improvement over both of the above prior art concepts in its use of a single flexible membrane which in operation is interposed between a tool pad, cushion or equivalent backing surface and a sandpaper or other flexible abrasive disc as mounted on said surface by the membrane. The invention in particular distinguishes over and improves on prior expedients in that the special membrane is protected prior to sale and/or use between a pair of like thin external strip discs or sheets. These serve as protective covers in the handling of the unit, said discs preferably having an inner non-tacky slip coat of clear wax-like or varnish-like material. This facilitates their stripping by peeling from the surfaces of the basic intermediate membrane, the latter as distinctively coated pressure-sensitively in the manner described in the Abstract.
The pad component of the compressively mounted combination may be permanently supported on a relatively rigid backing plate of metal or plastic, the pad comprising a vinyl or leather-like facing to which the membrane is adherently mounted, and a vinyl foam cushion part between said facing and the backing plate. The cushion is secured relatively permanently to the plate and the facing is secured equally permanently to the foam, as by a pressure bonded or contact cement. Said vinyl facing preferably carries a slip coat of varnish or varnish-like material to enable it to stick moderately strongly to the membrane's inner, heavier strength pressure-sensitive adhesive without, however, any likelihood of the membrane being dislodged from the backing pad under severe sanding.
The membrane may be of any appropriate grade of fiberboard or heavy paper material, but of whatever stock the membrane may be comprised, it should not tear readily, particularly in active abrading use; and with this in mind the membrane may also be of a textured fabric or woven cloth.
The ability in accordance with the invention to use plain unfaced and unprocessed sandpaper discs of course eliminates the cost factor in pre-coating each disc with a pressure-sensitive adhesive; a single coating of the inner tool-engaging surface of the membrane of the invention eliminates all of these costs. Likewise, a single coating of the external sanding disc-mounting surface of the membrane is all that is required in the successive use of a multiplicity of sandpaper discs of like or different grades, prior to their discard and replacement as they become worn and useless. The worn disc is simply stripped or peeled off the membrane, which remains in place on the tool pad or other mounting part with both of its pressure-sensitive coatings intact.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an end face elevation of a package-type lamination of special membrane and protective cover components, the form in which the adapter unit is sold and handled prior to use, the view illustrating in a partially fanned arrangement inner and outer protective strip discs and the intermediate membrane disc of the combination, the latter as coated pressure-sensitively on its opposite side surfaces;
FIG. 2 is a view in transverse diametral section through the lamination of FIG. 1, being in an enlarged scale schematically distorted somewhat for clarity in thicknesses of constituent disc and coating components;
FIG. 3 is a substantially full scale perspective view of the laminated package unit of FIGS. 1 and 2 as stripped of its protective covers and applied to a sander disc base pad structure, being equipped with a sanding disc and with the latter and its supporting membrane shown partially peeled away from a supporting base pad; and
FIG. 4 is a side-elevational view, partially broken away, showing a typical application of the unit as backing pad-mounted for use on a conventional motorized hand sander.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIGS. 1 and 2 somewhat schematically show, and not in necessarily scaled relation of their parts, the adapter unit of the invention, generally designated by the reference numeral 10, in the package form in which it is merchandised, whether in an appropriate outer promotional envelope or not. This unit consists of the essentially important membrane sheet or disc 12, which may be optionally constituted by a ruggedly strong flexible paper in any desired thickness, or may be constituted of a flexible grade of paperboard, fiberboard, a woven fabric, or like substantially inelastic thin sheet material. The material of membrane 12 is susceptible of relatively wide choice, so long as it has adequate strength and/or toughness to resist the torsional stress to which it is subjected in use, without tearing free from a support pad or disc on the sanding tool.
As thus constituted, an inner or rear surface of membrane disc 12 is relatively heavily coated with a pressure-sensitive adhesive of the rubber latex type, such as is readily available on the market in different grades. This rear or inner coating of membrane 12 is indicated at 13, and it is selected and set to afford a relatively high degree of adhesive strength or tackiness when pressure-sensitive applied against a non-coated surface. The opposite outer or front surface of membrane disc 12 is, on the other hand, provided with a coating 14 of the same general latex type, but in a thickness and/or grade such as to present when set a substantially lesser degree of adhesive strength or tackiness than does the inner or rear coating 13.
Finally, the membrane is removably and adherently faced at its respective coatings 13 and 14 with relatively thin protective strip or cover sheets 15, 16. These are in the form of light-gauge paper discs which are treated only on their membrane-facing surfaces, as by an appropriate dried waxy or varnish-like application, to render them individually non-tacky, but still readily strippable by the fingers from the respective coated membrane surfaces of unit 10. When the discs 15, 16 are stripped from the membrane 12, the latter is applied removably and adherently as a part of a backing pad and abrasive disc lamination unit or combination. This combination, generally designated in FIGS. 3 and 4 by the reference numeral 17, presents a further novel and improved aspect of the invention.
Said laminated unit 17 comprises a more or less conventional sub-combination of a relatively rigid circular backing plate 18 of metal or plastic material equipped at a central cavity thereof with a cylindrical washer-like reinforcement 19 which presents a preferably integral rearwardly extending and exposed stem 20 at which the adapted sander disc unit 17 is chucked to an entirely conventional motorized sander 22. There is typically an eccentric mount of said unit to the head 23 of sander 22, so that the unit 17 has an orbital sanding action, as indicated by the double-headed arrow in FIG. 4. In some cases, the stem will be threaded, as at 20' (FIG. 4), for its removable mount to the tool 22. Of course, the operational nature of said tool is entirely optional; but a dual action air motor driven one typically appears in FIG. 4.
FIG. 3 shows the rigid backing plate 18 of unit 17 as having a relatively permanent bond at a forward interface surface 25 thereof with a vinyl foam cushion 26 of cylindrical form and substantial thickness; and the forward surface of this cushion is faced by a leather-like vinyl sheet 27 having relatively great strength in tension and torsion. By preference, the vinyl facing 27 is forwardly provided with a slip coat of a clear varnish or varnish-like material for an improved adherence thereto of membrane disc 12.
That disc is shown in FIG. 3 as having its high strength or tacky inner latex coating 13 removably adhered to the cushion pad facing 27, with its more lightly adherent coating 14, as stripped of the protective cover 16, exposed and adherently engaged by the plain rear surface of a conventional sanding disc 28.
As thus constituted, the backed membrane and pad unit is resistant to tear and to dislodgement from its pad component under relatively heavy duty sanding operation. Yet the relatively small degree of tackiness of forward surface 14 enables the sanding disc 28 to be marginally lifted from membrane coating 14 and peeled off the latter for replacement when worn with another abrasive disc; and the greater tackiness of rear membrane coating 13 is sufficient to resist its separation from cushion pad 26 in said replacement removal of the sanding disc, while at the same time enabling the membrane 12 itself to be similarly stripped along with the sandpaper from the facing 27 of the rotary tool mount.