US2781618A - Abrasive articles and holders therefor - Google Patents

Description

Feb. 19, 1957 A. J. LARsoN 2,781,618

ABRAsIvE ARTICLES AND HOLDERS THEREFOR Filed March 27, 195e ja 7//\ fz 5./ 24 JZ /6 /7 56 2j 34 55 @all if ff 2Q Q5 m 2,781,618 Patented Feb. 19, 1957 dee ABRAslvE ARTICLES AND HOLDERS THEREFOR Adolph J. Larson, Wauconda, lll., assignor to Contur Abrasive Company, Inc., Crystal Lake, Ell., a corporation of Illinois The present invention relates to articles for finishing surfaces and means for holding such articles, and particularly, to improvements upon the articles and holders disclosed in the copending application of Donald N. Gellert, Serial No. 453,795, iled September 2, 1954, now Patent No. 2,747,343, issued May 29, 1956, which is assigned to the assignee of the present application.

The said copending application discloses a number of embodiments of surface finishing articles and holders therefor, some of which are intended for rotation and others for reciprocation. For convenience herein, reference is made principally to the rotary type, but it is to be understood that the present invention is equally applicable to the reciprocatory type.

A-A preferred embodiment of the rotatable finishing article disclosed in said copending application comprises an imperforate disc of emery cloth or the like and a backing therefor, the backing comprising a disc of relatively stii expendable material, such as iibre, having an annular marginal portion defining a plane surface and a circular central embossed portion raised with respect to the plane of the marginal portion. The abrasive disc is secured to the plane annular surface of the `backing and bridges across the embossed or raised portion. In its upper wall, lthe raised portion is provided with an axial centering aperture and a plurality of circumferentially spaced keyhole slots formed on a circle concentric with the axis of the disc, the slot portion of each keyhole extending forwardly in 4the direction of rotation of the article.

The holder inten-ded forA cooperation with the described article comprises a shaft, a cylindrical head on the shaft of a diameterv equal substantially to that of the embossed portion of Athe Aarticle backing, an axiall centering pin on the head, and a plurality of circumferentially spaced headed pins disposed concentrically on the head on a circle of the same diameter as that of the keyhole slots in the article.

In use, the axial pin on the holder is inserted in the axial aperture in the article to center the two, and the article and holder are then rotated relative to one another to align the headed pins with the keyhole slots, the head of each pin passing through the circular opening at the rearward end of a slot to be disposed in the space between the raised portion of the backing and the abrasive disc. Further rotation of the article and holder moves the shank of each headed pin into the slot of a keyhole and confines parts of the embossed backing between the head of each pin and the head of the holder, thus detachably to connect the article to the holder. When one article becomes worn, another may readily be substituted therefor' and the worn article discarded.

While the described holder and article have aforded substantial advantages in the art, certain difliculties have been encountered involving the convenience of attachment and removal of the article, the ability of the holder to retain the article under extremely demanding conditions of service, and the exibility/rigidity of the article.

It is the object of thespresent invention to provide improved articles and holders overcoming the said difficulties and meeting all the demanding requirements of the art.

Specifically, in regard to convenience of attachment of an article to the holder, one subject of the invention is to provide improved articles and holders including improved means for centering the article on the holder.

Another object of the invention is the provision of an improved holder including means adjacent each of the headed pins for assuring alignment of the head of each pin with the circular aperture at the rearward end of the respective keyhole upon relative rotation of the article in the direction 'to remove the same from the holder, thereby to lfacilitate removal. Y

An additional object is to provide an improved holder including means resiliently and frictionally engaging the article to prevent accidental displacement of the article relative to the holder.

A further object of the invention is the provision of a holder of improved construction including means resiliently mounting the headed pins for optimum support ofv an abrasive article.

It is also an object of the invention to provide an improved surface nishing article including improved slot means cooperable with the headed pins of the holder to assist in firmly retaining the article against accidental displacement relative to the holder.

A still further object is the provision of an improved surface iinishing article including backing means imparting flexibility to the marginal ange portion of the article.

Other objects and advantages of the invention will become apparent in the following detailed description of preferred `embodiments of the invention.

Now, in order to acquaint those skilled in the art with the manner of making and using the improved abrasive articles and holders of my invention, I shall describe, in connection with the accompanying drawing, preferred embodiments of the invention and preferred manners of making and using the same.

In the drawing, wherein like reference numerals indicate like parts: Figure l is a vertical cross section of the nishing article and the holder of the invention showing the article attached to the holder;

Figure 2 is a plan View of the article;

Figure 3 is a bottom view of the holder;

Figure 4 is a fragmentary sectional View taken substantially on line 4 4 of Figure 3;

Figure 5 is a side elevation of the article and a modified form of holder; and

Figure 6 is a side view, partly in section and partly in elevation, of further embodiments of the article 'and the holder. v

Referring now to the drawings, and particularly to Figures 1 to 4, I have shown preferred embodiments of my improved surface finishing article and holder, .the holder being indicated generally at 10 and thearticle at 30. The embodiments shown comprise a rotary assembly of disc form particularly adapted for use in portable rotary grinders, portable eiectric drills, drill presses and other rotary tools,

The holder lo comprises a metallic hub 11 including a reduced axial extension 12 at its lower end, a ring or carrier 13 concentrically encircling the extension 12 and a body 14 of molded rubber or the like bonded to the hub and ring. The hub 11 preferably is provided with a circumferential groove l5 to insure intimate bonding of the hub in the body. The hub is bored and counterbored from its upper end to define an axial passage therethrough and a radial shoulder 16 adjacent the lower endl of the hub.

An elongateA centering pin 17 is slidablyV mounted inl the bore of the hub and includes a lower end portion normally projecting a substantial distance beyond the lower end of the hub and body means. Adjacent its upper end, the pin 17 is provided with a head i3 engageable with the shoulder 16 to limit downward movement of the pin. The upper end of the bore in the hub is tapped for the threaded reception of a shaft 19 adapted to be received in the chuck of a rotary tool to be driven thereby. The shaft 19 retains the pin 17 in the hub, and a compression spring 20 is confined therebetween to bias the pin out wardly or downwardly of the hub. Preferably, the shaft and pin are provided with centering stubs on the adjacent ends thereof for reception of the opposite ends of the spring, the spring frictionally grasping the stubs to retain the three parts assembled when removed from the hub to mitigate against loss of the individual parts.

The ring or carrier 13 is of an inner diameter greater than the diameter of the extension 12 so as to be spaced radially therefrom and is bored at circumferentially spaced points for the reception of a plurality of article retaining means or members, preferably in the form of headed pins 21. The pins are preferably three in number and disposed at equal circumferential spacings to afford optimum support for the article at minimum cost. Each pin comprises a knurled shank press fitted in the ring and a head disposed in spaced parallel relation to the ring. The heads are thus disposed at equal spacings on a circle concentric with the axial pin 17.

The rubber body 14 of the holder is molded directly about the hub 11 ring 13 and pins 21, and generally complements the hub and ring. The ring or carrier 13 is thus mounted by the material of the body in spaced relation to the extension 12, and the resiliency of the body accommodates relative movement of the ring for a purpose to be described. The extension 12 which projects into the ring limits the dened movement and insures a substantially concentric disposition of the ring at all times. After molding, the body 14 may be machined to expose the pins 21 and to define a generally planar surface 22 in the central area of the bottom face of the body, the said surface being parallel to and spaced inwardly or upwardly from the heads of the pins. If desired, the body may include cloth reinforcing or the like. Radially outwardly of the pins, the body includes a radial flange portion having a depending annular resilient lip 23 encircling and extending below the heads of the pins, thus to dispose the pins within a generally circular recess 24. After the body has been molded, and machined if necessary, the centering pin, spring and shaft are assembled in the hub.

The finishing article 30 comprises an imperforate planar sheet 31 of finishing material, such as emery cloth, sandpaper, billiard cloth, felt or the like, and a backing 32 therefor. In the embodiment shown, the sheet 31 is of disc form and of a predetermined diameter. The backing 32 comprises a disc of the same diameter as that of the finishing material formed of a relatively stiff, yet very economical and completely expendable material. I prefer to form the backing of a composition material or fibre of a type which is well known and has been used extensively in the art. A suitable material is sold under the name Armite by Spaulding Fibre Company, Inc. of Tonawanda, New York. The backing disc 32 includes a rst portion-33 defining a substantially plane surface, in this embodiment an annular outer marginalflange, and a second portion 34 Vraised with respect to the plane portion 33, in this embodiment an embossed or raised, circular, .central portion. The embossed portion 34 defines a flat or plane upper surface on the disc 32 that is disposed .in spaced parallel relation t0 the plane surface portion 33. The discj31 of -nishing material is permanently and xedly secured at its inner or non-abrasive surface to the lower surface of the plane annular portion 33 of the backing 32` by a permanent glue', adhesive, or cement,

4 and the disc bridges across the raised or embossed portion 34 of the backing to define a cavity or chamber 35 between the raised portion of the backing and the sheet of finishing material. rfhe raised portion of the backing 32 is provided in the at circular wall thereof with a central or axial depression 36 having an imperforate wall, the depression being of a depth less than the'distance between the raised portion of the backing and the finishing material. On a circle concentric with the depression 36 a plurality of circumferentially spaced slots or openings 37, in the ferm generally of keyhole slots, are provided in the raised portion of the backing. Each slot 37 includes a small opening 38 of a diameter equal approximately to that of the shank of the pins 21 disposed forwardly in the direction in which the article is to be rotated, an enlarged aperture 39 of the size of the heads of the pins disposed rearwardly of the opening 38, and a slot portion 4d connecting the two. As will be appreciated, each slot 37 extends through the backing material and communicates with the chamber 35.

In the assembly of the described article and holder, the headed pins of the holder and the keyhole slots in the backing of the finishing material are of the same number and are located on circles of equal diameter, at equal circumferential spacings. The apertures 39 of the keyhole slots are of a size to accommodate passage of the heads of the pins 21, and the slot portions 40 and openings 38 are of a size to receive the shanks of the pins, but not to accommodate passage of the heads. The central depression 36 in the backing is of a diameter to receive the centering pin 17 on the holder. The embossed or raised portion 34 of the backing 32 is of substantially the same diamter as that of the recess 24 in the holder, and the lip 23 of the holder is of slightly greater height than that of the portion 34.

To assemble or mount an article on a holder, the article is positioned to accommodate initial entry of the centering pin 17 on the holder into the centering depression 36 in the embossed portion of the backing. In this respect, the present invention affords substantial advantage in that the pin 17 projects a considerable distance beyond the lower surface of the holder to enable the user to effect entry of the pin into the depression under visual observation to assure proper centering of the article on the holder. Thereafter, the user may move the article toward the holder, whereupon the pin retracts against the light biasing force of the spring 20. By providing an imperforate depression in the backing of the article, rather than an aperture, the present invention provides a strong surface area against which the pin 17 is biased by the spring 2t), so that the spring may perform some useful work, as will be described, without acting directly on the nishing material 31 or creating an unevenness or rupture therein.

VWhen the article is properly centered on the holder, the user moves the article toward the holder to retract the pin 17 and to move the raised or embossed portion of the backing 32 into the recess Z4 in the holder. As described, the lip 23 of the holder is of a greater height than the portion 34 of the backing, so that the lip engages on the plane surface portion 33 of the backing and is resiliently exed or compressed before the at upper surface of the backing engages the planar surface 22 of the holder. Thus, the spring Ztl and lip 2-3 of the holder both exert a resilient force on the article for a purpose to be described. When the upper wall of the embossed ponion of the backing has been forced into engagement with the heads of the pins 21, further axial movement of the two is temporarily prevented, and the holder may then be rotated relative to the article. The holder is rotated in the direction that the same would be rotated in normal use, and at the same time axial pressure is maintained on the article Vto maintain the described association of the two. By rotating the holder, the pins 21 are brought into alignment with the apertures 39 ofthe keyhole slots 37 in the article, whereupon the pins will enter into the slots, the heads of the pinswill be disposed in the chamber 35 and the upper surface of the backing 32 will engage the surface 22 of the holder. Due to the flexible mounting of the ring 13 carrying the pins 21, the pins are resiliently mounted for a knee action relative to the body of the holder to insure proper disposition of the pins in the raised portion of the backing, not only upon attachment of the article to the holder, but upon subsequent use as well.

With the pins entered in the keyholes as above described, further rotation of the holder in the defined direction will result in forcing the exposed portions of the shanks of the pins 21 through the slot portions 40 of the keyholes and into the openings 38. The spacing of the inner surfaces of the heads of the pins from the surface 22 is only slightly greater than the thickness of the backing material, and the heads of the pins are larger than the slots 40 and openings 38 so that the backing of the article in the raised central portion thereof is closely confined between the pin heads and the surface 22. The article is thus securely mounted on the holder for conjoint rotation therewith.

Attachment'of the article to the holder in the manner described is very conveniently and efficiently carried out. Likewise, detachment is swiftly effected. In use, however, the disc cannot readily become'detached from its holder. vThe direction of movement of the holder, as viewed from the stem end, is clockwise in practically all tools of the character referred to, thus imparting clockwise rotation to the article to insure that the pins 21 are constantly positioned in the openings 38 ofthe keyholes. Any resistance to movement applied to the disc further insures such positioning. The locating or centering pin 17 and the headed pins 21 prevent lateral movement of the disc relative to the holder so that thedisc is held for concentric rotation with the holder.

The embossing of the fibre backing 32 in relation to the thickness of the heads of the pins 21 is preferably such as to dene a cavity or chamber 35 of a depth greater than the thickness of the pin heads. By this arrangement, the pins 21 will be conned closely to the surface of the backing and will be spaced from the finishing material so as to avoid any possible interference with, or bumpiness or irregularity in, the finishing surface. The finishing material is firmly supported by the annular marginal portions 33 of the disc, and is stretched relatively tautly across the area of the raised portion 34. The backing material is tough and relatively stiff to insure firm support of the finishing material without appreciable distortion in the area of the embossed portion of the disc. Being tough, the libre will retain its shape and Will Withstand rough handling to insure ready attachment of an article to a holder and to prevent tearing of the fibre in use.

While the firm engagement of the headed pins 21 in the keyhole slots in the article backing normally retains the article on the holder for conjoint operation therewith, the conditions of use to which the article and holder are subjected are so severel that additional precautions against accidental detachment of the article are essential. In particular, the holder and article of the invention are adapted to be driven by a variety of devices, including pneumatic grinders which operate at speeds up to 60,000 R. P. M. When air supply to a pneumatic grinder is discontinued, the grinder spindle stops immediately, apparently because of exhaust back pressure. The holder, being fixedly attached to the grinder spindle, likewise stops immediately, whereas the momentum of the article maintains rotational force on the same in the direction to move the apertures 39 into alignment with the heads of pins 21, in which position the article would be free to become detached from the holder. Under such circumstances, a substantial load is placed on the detachable connection of the article to the holder. To insure against inadvertent or accidental detachment of the article, the present invention, in the frstjinstance, provides movement retarding means in the form of the spring 20 and lip 23 on the holder. According to the invention, the spring 20 and lip 23 maintain resilient forces on the backing 32 of the article to maintain the backing in firm frictional engagement with the heads of the pins, and the lip 23 frictionally engages the article under the said resilient force to mitigate against relative rotation of the article and holder. .in addition, the invention provides a locking form of keyhole slot. Specifically, the centers of the opening 38 and aperture 39 of each keyhole 37 are set on the circle defined by the axes of the pins 21, and the slot portion 40 of each keyhole defines portions of the backing material disposed in the arcuate path of movement described by a pin 21 in being rotated from the aperture 39 into the opening 38. In a preferred embodiment, the slot portion 40 of each keyhole, at least adjacent the opening 38, is oset from the circle on which the opening is set. By virtue of the defined relationship, as the shank portion of a pin 21 passes through the slot portion 40 of the keyhole, the pin forcibly engages against the margin of the slot and forces the backing material adjacent the said margin out of its normal position or shape. When the shank of the pin enters the opening 38, the tough material from which the backing is formed returns substantially to normal shape, wherein a part thereof projects into the path of return movement of the shank of the pin to constitute releasable detent means detachably retaining the pin in the opening 38. Thus, the invention positively insures against inadvertent detachment of the article from the holder. Yet, the article may be manually detached from the holder speedily and with relative ease.

To facilitate convenient detachment of the article, I provide means to the rearward side of the shank of each pin for preventing movement of the pins relative to the article rearwardly beyond the position wherein the heads of the pins are aligned with the apertures 39 of the keyholes. Specifically, as shown in Figures 3 and 4, I provide a rubber abutment 25, integral with the body 14, to the rearward side of the shank of each pin in the direction of holder rotation, the abutment extending from the surface 22 of the holder to the inner surface of the pin head, being of the same width as the pin shank and projecting from the shank to the trailing edge of the head, thus to fill the space between the surface 22 and the head of the pin to the trailing side thereof. When a worn finishing article is being removed from the holder, the abutments 25 prevent relative rotation to such position that the heads of the pins would overlie portions of the article backing at the rearward margin of the keyhole apertures 39, which would prevent removal of the article, and assure alignment of the heads and apertures. l'n the resulting position of alignment, the resilient force of the lip 23 and spring 20 on the article bias the article away from the holder, whereby removal of the article is effected with extreme ease.

In use of the article and holder of the invention, some flexibility of the article is normally required, -the degree of fiexibility varying generally in three stages, highly fiexible, fairly stiff and relatively rigid. The backing material of the holder is quite stiff and the marginal portion 33 thereof normally stifens the article so that if the portion 33 is left unsupported by the holder, as shown generally in Figure 1, the second or intermediate requirement as to article exibility is satisfied. To this end, the body of the holder is of a diameter only slightly larger than the embossed or raised portion 34 of the backing, so as to define a lip 23 which engages about the inner margin only of the portion 33 of the article. The peripheral portions of the finishing disc 31 are thus supportedl only by the backing 32, and accordingly are fairly stiff, yet somewhat flexible.

To render the article more rigid, a second form of holder is `provided in accordance with the invention, which, as shown in Figure 5, includes a body having a radially extending marginal fiange portion 50 defining a wide resilient lip extending substantially to the periphery of the article, thus to afford a support for the marginal flange of the article. The holder otherwise is the same as that shown in Figure l.

To increase fiexibility, the present invention provides an improved article as shown in Figures l and 2. In the improved form, the marginal flange portion 33 of the backing 32 has a plurality of concentric arcuate slits fst therethrough which accommodate ready fiexing of the backing. The finishing material per se, being thin, is highly fiexible, so that the resultant article attains a high degree of flexibility. As shown, the finishing material 31 is imperforate or unslitted, and the slits all are provided solely in the backing material. The slits preferably extend entirely through the backing material, and the flange portion includes a plurality of unslitted, circumferentially spaced, relatively thin radial ribs 42, suitably three or six at equal circumferential spacings, to retain the backing in one piece. When used with the holder shown in Figure l, the article of Figure 2 is highly flexible to facilitate contour grinding of short radius fillets and other concave and covex surface configurations. lf less flexibility is required, the improved article described may be employed in conjunction with the holder of Figure 5.

For small diameter finishing discs, such as 3/4 inch, a third form of holder, shown in Figure 6, is preferred according to the present invention. In this embodiment, the construction of the article and holder are generally the same as previously described, with the exception that the holder does not include a radially extending ange. The body of the holder tapers uniformly downward in a generally conical form to a bottom diameter somewhat greater than that of the pin carrying ring 13, to define a downwardly extending, thin, flexible lip 60 adapted to engage resiliently along the sides of the raised portion 34 of the article backing and against the upper surface of the plane portion 33 of the backing for the purposes previously explained,

From the foregoing, it is to be appreciated that the present invention provides improved article holders, preferably in three embodiments, each of the same general improved construction including a resilient body iiexibly supporting a ring that carries the headed pins so as to accommodate a knee action insuring proper attachment of an article to the holder. The holders further include an improved centering pin construction facilitating alignment of an article with the holder, and providing a spring force that assists in retaining the article on thc holder and that expedites removal of the article from the holder. rfhe resilient body of the holder includes a lip resilicntly and frictionally engaging the article to assist in retaining the same on the holder, and moreover provides abutment means adjacent each pin for facilitating removal of the article from the holder.

In addition to the above, the present invention provides an improved surface finishing article for cooperation with said holder', including a particular flange construction enhancing the flexibility of the article and including improved keyhole slot means and improved centering means. The central depression of the raised portion of the article backing insures proper alignment of the article `with the holder and prevents any detrimental consequence from the employment `of a spring biased retractable centering pin on the holder. The improved lteyholes cooperate with the locking pins on the holder to facilitate attachment of the article to the holder, and to retain the article firmly on the holder despite and severe abuse to which the article and holder are subjected in use.

Accordingly, it is apparent that the present invention overcomes the enumerated difficulties encountered in the art and, affords surface finishing means of optimum de sign-and economy. The objects of the invention are thus shown to be attained in a highly practical, convenient and economical manner.

l claim:

l. A holder for finishing articles comprising a molded resilient body, a hub molded in said body including an extension adjacent one face of said body, a carrier molded in said body and encircling said extension in spaced relaton thereto, and article retaining means mounted on said carrier and extending beyond said one face of the body for cooperation with the finishing article, said resilient body accommodating relative movement of said carrier and said extension limiting such movement.

2 A holder for finishing articles comprising body means h 2 a face engageable with the finishing article, article retaining means projecting from said face of said body means for cooperation with the finishing article, and resilient lip means projecting from said face of said body means beyond said 'article retaining means for resilient frictional engagement with the article.

3. A holder for finishing articles comprising a lmolded resilient body, a hub molded in said body including an extension adjacent one face of said body, a carrier molded in said body and encircling said extension in spaced relation thereto, and article retaining means mounted on said carrier and extending beyond said one face of the body for cooperation with the finishing article, said resilient body laccommodating relative movement of said carrier and said extension limiting such movement, said body including a resilient lip encircling said carrier and projecting from said face thereof beyond said article retaining means for resilient frictional engagement with the finishing article.

4.'A rotatable holder for finishing articles comprising a molded resilient body, a central hub molded in said body axially thereof, said hub including a reduced extension adjacent one end face of the body, a ring moldedin said body in radially spaced concentrically encircling relation to said extension, said ring carrying a plurality of circumferentially spaced headed pins disposed in concentric relation to the axis of said hub and body, said pins extending through said one end face of the body, the heads of said pins being disposed in outwardly spaced relation to said face, said hub having an axial bore therethrough, a centering pin reciprocably mounted in said bore and having an outer end portion normally projecting substantially beyond said one end face of the body, a shaft detachably mounted in said bore in `said hub at the end thereof opposite said one end face of the body, and a spring confined in said bore between said shaft and said centering pin normally biasing the outer end portion of said pin outwardly beyond said one end face of said body, said body at said one end face thereof including a lip concentrically encircling said headed pins in radially spaced relation thereto and projecting outwardly beyond the heads of said pins, said body including abutment portions adjacent the shank of each of said headed pins disposed to the rearward side of the pin in the direction of rotation of the holder, said abutments each projecting from the shank of the respective pin to the trailing edge of the head thereof and from said one end face of the body to the head.

5. A finishing article comprising Ia fiat sheet of finishing material and a backing therefor, said backing comprising a sheet of relatively stiff` expendable material of a size substantially equal to that of the finishing material, said backing including fa planar marginal portion to which said sheet of finishing material is secured, said marginal portion of said backing including a plurality of spaced ribs and having a plurality of spaced slits therethrough between said ribs, said slits accommodating flexing of said portion and imparting a high degree of flexibility to the marginal portions of the article.

6. A finishing-article `and a holder therefor, said article comprising a sheet of finishing material and a backing forv said sheet, said backing having a vplane surface portion to which said sheet is secured and a portion raised relative to said sheet, said raised portion of said backing having an imperforate centering depression therein of a depth no greater than the spacing between said sheet and said raised portion, said holder comprising hub means having a bore therethrough, a centering pin slidably mounted in said bore and including a portion extending beyond one end of said hub means for entry into said depression in said article, andresilient means normally biasing said pin toward Vsaid one end of said hub means, said portion of said pin centering the article on the holder and being retractable into said bore against the bias of said resilient means to accommodate disposition of said naised portion ofi saidbacking in proximity to said end of saidvhubmeans. I

7. A finishing article and a holder therefor, said article comprising a sheet of finishing material and a backing for said sheet, said backing comprising a sheet of relatively stitf expendable material including a plane surface portion to which said sheet of finishing material is secured and a portion raised relative thereto, said raised portion of said backing having Aa plurality of spaced slots therethrough, said holder comprising body means having a face engageable with the backing of said article and a plurality of headed pins projecting from said face, said pins being of the same number as said slots and disposed complemental thereto, said slots each including an aperture of a size accommodating passage of the head of each pin, an opening smaller than the head of each pin but lof a size accommodating the shank of the pin and a slot portion joining the aperture and opening, said opening being disposed forwardly in the direction of movement of the article and holder, the said slot portions defining portions of said backing disposed in the path of movement of said pins along said line, the heads of said pins being movable through said .apertures of said slots, said holder being movable relative to said article to force the shanks of said pins through the slot portions of said slots and into said openings thereof to confine portions of said backing between the heads of said pins and said face of said body means thereby to mount the article on the holder, the shank portions of said pins during movement through the said slot portions forcing said portions of said backing out ,of normal shape and accommodating at least partial return of said portions toward normal shape when said Shanks enter said openings, said portions of said backing in said latter position comprising releasable detent means disposed in the pa-th of return movement of said Shanks detachably to retain said pins in said openings of said slots.

8. A finishing article and a holder therefor as set forth in claim 7, including resilient lip means on said body means projecting from said face thereof beyond the heads of said pins, said lip means resiliently and frictionally engaging said backing to assist in retaining the article on the holder.

9. A finishing article for use with a holder having article retaining means projecting from one surface thereof, said article comprising a sheet of iinishing material and a backing therefor, said backing including a plane surface portion to which said sheet is secured and a portion raised relative thereto, said raised portion of said backing having at least one slot therein for reception of -the article retaining means on the holder, said slot including an aperture for accommodating passage therethrough of the said retaining means, an opening spaced from said aperture for substantially conformably receiving said means in article retaining position and a slot portion joining said aperture and opening, said slot portion deiining portions of said backing intersecting said opening for releasably retaining said means in said opening.

10. A rotatable finishing article comprising a disc of nishing material and a backing therefor, said backing y10 comprising a disc of expendable material of a diameter substantially equalto that of the finishing material, said backing including a planar marginal ange i portion to which -the iinishing material is secured and a circular central portion raised relative thereto, said central portion of said backing including axial centering means and having a plurality of circumferentially spaced slots therein disposed in generally concentric relation to said means, each of said slots including a relatively larger aperture, a relatively small opening spaced from the aperture and a slot portion joining said aperture and said opening, said slot portion deiining portions of said backing intersecting said opening and lying in the normal path of communication between said aperture and said opening.

l1. A holder for finishing articles comprising rotatable body means, an axial centering pin extending from one surface of said body means, a plurality of headed pins projecting from said surface of said body means, the heads of said pins being spaced from said surface, said headed pins being disposed in circumferentially spaced relation to one another in generally concentric relation to said centering pin, and a resilient annular lip projecting from said surface beyond the heads of said pins, said lip being concentric with said centering pin and encircling said headed pms.

l2. A rotatable finishing article and holder; said article comprising connected discs of iinishing and backing material, the backing including a plane marginal portion to which the finishing material is secured and a central portion raised relative thereto, said raised portion of said backing having a plurality of slots therethrough disposed in circumferentially spaced relation concentric with the axis of rotation of the articles and holder; said holder comprising a rota-table body, a plurality of headed pins projecting from one face of said body and disposed in complemental relation to said slots in said backing for cooperation therewith; said slots each including an aperture of -a size accommodating passage of the head of each pin, an opening smaller than the head of the pin but of a size to receive its shank and a slot portion joining the Iaperture and opening, the opening being disposed forwardly'in the direction of rotation of the article; the heads of said pins being insertable into said apertures; said holder being rotatable relative to said article to rotate the Shanks of said pins through the slot portions of said slots and into said openings to confine portions of said backing 'between the heads of said pins and said face of said body thereby to mount the article on the holder; said body having a resilient portion including a resilient lip concentric with and encircling said pins and projecting from said face of said body beyond the heads of said pins, said lip resiliently and frictionally engaging said backing to assist in retaining the article on the holder, and abutment means associated with each of said headed pins to the trailing side thereof in the normal direction of rotation of the article and holder, said abutment means filling the space between said face of said body and the head of each pin to the said trailing side thereof to dispose the heads of said pins in alignment with the apertures in said slots when said holder is rotated in the opposite direction relative to said article, said resilient lip of said body biasing said article oif of said holder when said apertures are aligned with the heads of said pins.

13. A rotatable finishing article and holder; said article comprising connected discs of iinishing and backing material, the backing including a plane marginal portion to which the iinishing material is secured and a central portion raised relative thereto, said raised port-ion of said backing having axial centering means therein and a plurality of circumferentially spaced slots therethrough disposed in concentric relation to said centering means; said holder comprising a rotatable body, a plurality of headed pins projecting from one face of said body disposed in complemental relation to said slots; an axial centering pin extending from said face of said body for entry into said centering means in said backing for centering the article on the holder; said slots each including an aperture of a size to accommodate passage of'the head of each pin, an opening smaller than the head of the pin but of a size to receive its shank and a slot portion joining the aperture and opening, the opening being disposed forwardly in the direction of rotation of the article; the heads of said pins being enterable into said apertures; said holder being rotatable relative to said article about the axis of said centering pin to rotate the shanks of said headed pins through the slot portions of said slots and into said openings to confine portions of said backing between the heads of said pins and said face of said body thereby to mount the article on the holder, the said slot portions of said slots dening portions of said backing 1 disposed in the pa-th of movement of the shanks of said headed pins, the Shanks of said pins during movement through said slot portions forcing said portions of said '12 backing out of normal shape and accommodating at least partial return of said portions toward normal shape when the Shanks enter said openings, said portions of said backing in said latter position comprising detent means releasably retaining said pins in said openings; said body having a resilient portion including a resilient lip concentric with and encircling said pins and projecting from said face of said body beyond the heads of said pins, said lip resiliently and frictionally engaging said backing to assist in retain- 10 ing the article on the holder.

References Cited in the le of this patent UNITED STATES PATENTS -www,

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