GB2360474A - Manufacturing of abrasive wheels - Google Patents

Abstract

An abrasive wheel comprising a hub and sheets of abrasive material extending radially therefrom is manufactured by compressing a pack of said sheets 21 between two blades 23 and 24 connected to each other by an elastic strap 25, transferring the pack 21 to a mandrel 34 by means of the blades 23 and 24 where one end 30 of one of the blades 23 is inserted into a slot 36 on the mandrel 34. The other blade 24 is then rotated about the mandrel 34, thereby forming the pack 21 into an annulus about the mandrel 34. A ring (37, fig. 4) is then fitted onto the annular pack 21. The ring (37, fig. 4) maintains the shape of the pack 21 when it is removed from the mandrel 34 and the blades 23 and 24 for fixing by adhesive (4, figs. 5, 7 and 8) onto a shaft (2, fig. 5) or a sleeve and flanges (43 and 45, figs. 7 and 8).

Description

1 --- 2360474 1 METHOD OF MANUFACTURING ABRASIVE BRUSHES, AND RELATIVE

MANUFACTURING SYSTEM The present invention relates to a method of manufacturing abrasive brushes of the type in which a number of abrasive sheets are equally spaced about and fitted to a hub.

one known method of making abrasive brushes of the above type is to arrange the sheets manually about the hub and fix the sheets to the hub by injecting resin about the hub. The sheets are picked up one by one or in small groups by hand, and are positioned so as to extend radially with respect to the hub.

The above known method has several drawbacks. In particular, it is relatively time-consuming, owing to the sheets having to be spaced and aligned extremely accurately to prevent in-service vibration caused by a lack of symmetry of the brush.

Moreover, using the above known method, the quality of the finished brush depends on the skill of the operator, so that a constant quality standard cannot be maintained.

2 It is an object of the present invention to provide a brush manufacturing method designed to eliminate the drawbacks of the known state of the art.

According to the present invention, there is provided a method of manufacturing abrasive brushes comprising a hub and a.giver number of sheets of abrasive material equally spaced and oriented radially about said hub; the method comprising the steps of compressing an orderly pack of said given number of sheets, parallel to and facing one another, along a first axis perpendicular to the sheets; and winding said pack about a given second axis parallel to said sheets, so as to equally space said sheets in said pack in an annular configuration; the step of winding said pack including compressing said sheets against one another at respective first edges close to said second axis, and spacing said sheets with respect to one another at respective second edges of said sheets.

The present invention also relates to a system for manufacturing abrasive brushes of the type in which a number of abrasive sheets are equally spaced about and fixed to a hubL.

According to the present invention, there is provided a system for manufacturing abrasive brushes comprising a hub and a given number of sheets of abrasive material equally spaced and oriented radially about said hub; the system comprising gripping means, in turn comprising a first blade and a second blade for compressing an orderly pack of said given number of 3 sheets, parallel to and facing one another, along a first axis perpendicular to the sheets; and an assembly fixture, in turn comprising a shaft extending along a given second axis and comprising lock means for locking said first blade; said second blade being rotated about said second axis to equally space said sheets in said pack in an annular configuration.

A non-limiting embodiment of the present invention will be described by way of example with reference to the io accompanying drawings, in which:

Figure 1 shows a side view of a system machine for implementing one step in the method according to the invention; Figures 2, 3 and 4 show views in perspective, with parts removed for clarity, of system tools for implementing successive steps in the method according to the invention; Figure 5 shows a section of a brush and f ixture in the course of one step in the method according to the invention; Figure 6 shows a view in perspective of a variation of the Figure 5 brush; Figure 7 shows a section of the Figure 6 brush in the course of an assembly step in the method according to the present invention; Figure 8 shows a detail of Figure 6.

Number 1 in Figure 5 indicates as a whole an abrasive brush comprising a shaft 2 extending along an 4 axis A; and a given number N of abrasive sheets 3 - only two of which are shown in Figure 5 - extending radially with respect to shaft 2 and fixed to shaft 2 by means of a resin 4. Each sheet 3 has an inner edge 3a located at 5 shaft 2, and a free edge 3b opposite edge 3a.

Figure 1 shows a system I comprising a machine 5 for cutting sheets 3 from a strip 6 of abrasive cloth. Machine 5 comprises a support 7 for supporting respective reels 8 of strips 6 of abrasive cloth; and a cutter 9 for cutting sheets 3 off strips 6.

Support 7 comprises four unwinding pins 10 for supporting respective reels 8 when unwinding respective strips 6.

Cutter 9 comprises two facing rollers 11, between which the strips 6 unwound off respective reels 8 are brought together along a common path P; and a drive roller 12 facing a roller 13 pressed against drive roller 12 to step-feed strips 6 along path P in a direction D1.

Cutter 9 also comprises a punch 14 movable back and forth in a direction D2 perpendicular to direction D1; and a die 15 located along the feed path P of strips 6. Punch 14 and die 15 are located on opposite sides of path P; and die 15 is aligned with a prismatic guide 16 housing a pusher 17, which is movable in direction D2 and supported by elastic means not shown.

Cutter 9 also comprises actuating members 18 and 19 for respectively activating drive roller 12 and punch 14.

With reference to Figure 2, cutter 9 also comprises plate 20,. which is movable back and forth, in a direction D3 perpendicular to directions D1 and D2, between a work position covering die 15, and a rest position exposing die 15 to permit insertion of punch 14 inside die 15.

The cut sheets 3 are packed inside prismatic guide 16 and compressed between plate 20 and pusher 17 by elastic means (not shown) acting on pusher 17.

After forming a pack 21 of sheets 3, i.e. an orderly group of N sheets 3 facing and parallel to one another and housed inside prismatic guide 16 along an axis C, machine 5 is deactivated to enable removal of pack 21. As shown in Figure 2, pack 21 is removed by means of a tool 22 comprising two blades 23 and 24, and an elastic strap 25 connecting blades 23 and 24 to each other. As shown in Figures 2, 3 and 4, blades 23 and 24 have respective grips 26 and 27; and respective gripping portions 28 and 29, which, in use, are positioned contacting the end faces of sheets 3 in pack 21, while strap 25, in use, is placed in contact with edges 3b of sheets 3. Blade 23 also comprises, at the opposite end to grip 26, an appendix 30 projecting beyond gripping portion 28; and elastic strap 25 is fixed to gripping portion 28, 29 of each blade 23, 24 at a point lying between grip 26, 27 and gripping portion 28, 29.

Number 31 in Figures 3 and 4 indicates an assembly fixture comprising a base 32, a circular platform 33 integral with base 32, and a pin 34 integral with 6 platform 33 and having an axis 35 and a groove 36 parallel to axis 35. Fixture 31 is used,together with tool 22, to equally space sheets 3 in pack 21 about axis as described in detail below.

In addition to tool 22 and fixture 31, Figure 4 shows a i ring 37 having an inside diameter DM substantially equal to the outside diameter of brush 1, and which is placed about sheets 3 in pack 21 spaced about axis 35.

In Figure 5, brush 1 is shown positioned on a centering fixture 38 comprising a base 39 for centering shaft 2, and a plate 40 integral with the base and for centering sheets 3 with respect to shaft 2. Once the shaft and sheets are centered, a noz"zle 41 injects a measured quantity of resin 4 about shaft 2 to fix sheets 3 to shaft 2. The making of brush 1 will now be described as of removal of a pack 21 of N sheets 3 from prismatic guide 16. 20 With reference to Figure 2, grips 26 and 27 of tool 22 are gripped by the operator; blades 23 and 24 are parted to stretch strap 25, and respective gripping portions 28 and 29 are inserted inside prismatic guide 16, at opposite ends of pack 21 of sheets 3, so that 25 strap 25 contacts edges 3b of sheets 3; and the pack 21 of sheets is extracted from prismatic guide 16, in the course of which, sheets 3 are maintained in an orderly position by elastic strap 25 and the pressure applied by 7 the operator on grips 26 and 27, which exert compression along axis C of pack 21. At this stage, maintaining sheets 3 in group 21 in an orderly position is also assisted by each sheet 3 having an abrasive, i.e. rough, surface contacting a smooth surface of the adjacent sheet 3, so that a small amount of compression on the ends of pack 21 is sufficient to produce a high degree of friction between adjacent sheets 3.

With reference to Figure 3, pack 21 is then transferred onto fixture 31 by means of tool 22, which is connected to pin 34 by means of appendix 30, which projects from pack 21 and is inserted inside groove 36 in pin 34 so that pack 21 rests partly on platform 33. Maintaining blade 23 in the above position, the operator then rotates blade 24 about axis 35 of pin 34 as shown in Figure 4 so that sheets 3 fan out into a circle about pin 34. That is, sheets 3 contact pin 34 along edges 3a, and strap 25 along edges 3b; and, as blade 24 is rotated, edges 3a are brought successively into contact with pin 34, the adjacent sheets 3 remain contacting one another at edges 3a, and edges 3b are fanned out by elastic strap 25, which is formed into a loop about axis 35 of pin 34. At this stage, elastic strap 25 provides for pushing sheets 3 radially against pin 34 and fanning edges 3b of sheets 3 out about axis 35. That is, sheets 3 are compressed at edges 3a and spaced apart at edges 3b.

When blade 24 is rotated full circle into contact with blade 23, sheets 3 extend radially with respect to 8 axis 35 of the pin, and ring 37 is fitted about sheets 3 to hold sheets 3 in position so that tool 22 can be removed.

Sheets 3 in the annular configuration are removed together with ring 37 and placed on shaft 2 and plate 40 of centering fixture 38. Though the adjacent sheets 3, at this stage, contact one another over a relatively small surface portion at edges 3a, the friction between the adjacent sheets 3 and ring 37 are sufficient to keep io sheets 3 in the annular configuration even without pin 34. once sheets 3 are positioned on fixture 38, nozzle 41 emits and distributes a measured quantity of resin 4 about shaft 2 at edges 3a of sheets 3 so as to fix sheets 3 to shaft 2. Once resin 4 sets, brush 1 is complete and is removed from fixture 38.

In a variation not shown, system I comprises a hopper located over centering fixture 38. The hopper is in the form of a truncated cone converging towards an outlet facing fixture 38 and of substantially the same diameter as diameter DM of ring 37, which is maintained beneath the hopper at fixture 38; and sheets 3 are transferred by means of tool 22 from fixture 31 to fixture 38, and are fed through the hopper, at the outlet of which, the sheets are inserted inside ring 37. In other words, the hopper provides for assisting insertion of sheets 3 inside ring 37.

Number 42 in Figures 6, 7 and 8 indicates a variation of brush 1. Brush 42 comprises a sleeve 43 of 9 axis B; a number of sheets 44 equally spaced about sleeve 43; and two flanges 45 located at opposite ends of sleeve 43 to fix sheets 44 to sleeve 43. Each sheet 44 has an inner edge 44a; an outer edge 44b; and two slits 46 located between inner edge 44a and outer edge 44b and close to the inner edge; and flanges 45 have respective annular appendixes 47, which are inserted inside respective slits 46 in sheets 44 to connect sheets 44 to flanges 45. Number 48 in Figures 7 and 8 indicates a centering fixture comprising a base 49; and a pin 50 having an axis 51 and fitted to base 49, which has a seat 52 for housing a flange 45.

The making of brush 42 will be described with reference to Figures 7 and 8, it being understood that sheets 44 are cut, are f ormed into a pack 21 of sheets 44, and are arranged into a circle by means of tool 22 and fixture 31 in the same way as sheets 3.

one flange 45 is fitted onto pin 50 and inside seat 52 with appendix 47 facing upwards, and sleeve 43 is f itted onto the pin and to flange 45. At this point, sheets 44 - which, as described previously, are arranged in a circle and held together by ring 37 - are f itted about sleeve 43 so that appendix 47 fits inside slits 46; resin 4 is injected between sleeve 43 and inner edges 44a of sheets 44; and the other flange 45 is fitted onto the top end of sleeve 43 so that appendix 47 fits inside slits 46.

once resin 4 sets, brush 42 is complete and is removed from pin 50.

Claims (1)

1) A method of manufacturing abrasive brushes comprising a hub and a given number of sheets of abrasive material equally spaced and oriented radially about said hub; the mthod comprising the steps of compressing an orderly pack of said given number of sheets, parallel to and facing one another, along a first axis perpendicular to the sheets; and winding said pack about a given second io axis parallel to said sheets, so as to equally space said sheets in said pack in an annular configuration; the step of winding said pack including compressing said sheets against one another at respective first edges close to said second axis, and spacing said sheetg with respect to one another at respective second edges of said sheets.

2) A method as claimed in Claim 1, wherein said pack is compressed by means of a tool comprising a first blade and a second blade connected to each other by an elastic strap; said first and said second blade being located at the end sheets in said pack; and said strap being located contacting said second edges,.

3) A method as claimed in Claim 2, wherein said pack is wound by means of said tool about a pin extending along said second axis; said first edges being brought gradually into contact with said pin, and said second edges being drawn gradually apart by said elastic strap, which is closed into a loop about said first axis.

4) A method as claimed in Claim 3, the method 12 comprising the further steps of maintaining said sheets equally spaced about said second axis by means of a ring surrounding said sheets; and releasing said tool from said sheets. 5 5) A method as claimed in Claim 4, the method comprising the further step of removing the equally spaced said sheets from said pin by means of said ring. 6) A method as claimed in Claim 5, the method comprising the further step of centering the equally spaced said sheets with respect to said hub by means of a centering fixture; and fixing said sheets to said hub.

7) A method as claimed in Claim 5, wherein the step of fixing the equally spaced said sheets includes injecting an adhesive material between said hub and the equally spaced said sheets.

8) A method as claimed in Claim 5, characterized in that said adhesive material is a resin.

9) A method as claimed in one of the foregoing Claims, wherein said hub is a shaft; said brush comprising a shaft, a number of sheets equally spaced about said shaft, and a resin surrounding said shaft.

10) A method as claimed in one of Claims 1 to 8, wherein said hub is a sleeve; said brush comprising a sleeve, a number of sheets equally spaced about said sleeve, and two flanges fixed to opposite ends of the sleeve and to said sheets.

11) A method as claimed in Claim 10, wherein each of said sheets comprises two slits; and each of said flanges 13 comprises an appendix insertable inside one of said slits.

12) A method as claimed in Claim 1, and comprising the further steps of detaching said sheets from at least one strip of abrasive material by means of a cutting operation; and packing said sheetb inside a prismatic guide to form said packs.

13) A system for manufacturing abrasive brushes comprising a hub and a given number of sheets of abrasive material equally spaced and oriented radially about said hub; the system comprising gripping means, in turn comprising a first blade and a second blade for compressing an orderly pack of said given number of sheets, parallel to and facing one another, along a first axis perpendicular to the sheets; and an assembly fixture, in turn comprising a shaft extending along a given second axis and comprising lock means for locking said first blade; said second blade being rotated about said second axis to equally space said sheets in said pack in an annular configuration.

14) A system as claimed in Claim 13, characterized in that said first and said second blade are connected to each other by an elastic strap.

15) A system as claimed in Claim 13, characterized in that said first blade comprises an appendix; said shaft comprising a groove for housing said appendix.

16) A system as claimed in one of Claims 13 to 15, characterized by comprising a machine in turn comprising c. 1 14 i a cutter for cutting said sheets from at least one strip of abrasive material, and a prismatic guide for packing the cut sheets and forming said packs.