BE603789A - - Google Patents

Description

       

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  "Method of manufacturing abrasive tools"
The present invention relates generally to abrasive tools and relates more particularly to rotary abrasive tools of the grinding wheel type.



   A wide variety of grinding wheels are commonly manufactured and they are usually made of a mass of separate abrasive grains, densely agglomerated and bonded using a molded and fired ceramic material or resin binder. It is well known that such grinding wheels are difficult to manufacture, requiring very careful placement.

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 more abrasive grains and also usually relatively prolonged curing or polymerization. Many of these wheels are relatively fragile, require gentle handling and also frequent dressing to maintain uniform cutting efficiency. Wheels which are capable of performing a rapid cutting action have not been found to simultaneously provide a surface finish of the quality frequently required.



   In ordinary grinding wheels the granules or grains of abrasive material come into direct contact with each other and the gaps can be completely filled with a binding agent, although in other cases it is necessary to leave tiny voids which are inevitable as a result of the irregular shapes of high density agglomerated grains.

   It is also known to make abrasive, slightly elastic polishing pads and finishing wheels from cellular elastomeric materials and resins, such as sponge rubber and synthetic resins, but it is obvious that the latter type of articles cannot be suitable for forming a grinding wheel because it does not have the basic characteristics required for a grinding wheel, namely: the ability to perform a cut of predetermined dimensions in a work, for example in a steel article , when the grinding wheel and the work are moved in relation to each other.



   Consequently, the main aims

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 hereby invent @ @n are to provide @ - tools. br @ site .1'a new type, and more especially grinding wheels, in which the abrasive chips are supported, generally slightly apart from each other, in a body of cellular resin,

   such a cell body being rigid as a whole in order to allow the grinding wheel to make a deep cut in the work having a shape and dimensions predetermined with precision while at the same time supporting the abrasive grains so as to allow micro-movement individual of the latter in order to adjust the working pressures, and at the same time avoiding that the grains are prematurely dislodged from the grinding wheel or that) in a variant, they do not cause deep localized creasing in the work.

   Accordingly, such grinding wheels are both capable of precise capping action and of obtaining a better finish of the work, these two characteristics having previously been considered incompatible; - A method of manufacturing such abrasive tools which not only makes it possible to achieve a substantially uniform distribution of the abrasive grains, for example on the periphery of the grinding wheel, but also ensures the desired slight spacing, substantially uniform, between the grains, in view to facilitate such an individual adjustment of the grains to the working surface of the tool, and also to allow a complete fall.

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 mode for chips,

   thereby avoiding excessive loading or smoothing of the working surface of the tool and reducing the necessary frequency of dressings of such surface using a diamond dressing tool or the like; - a particularly advantageous composition for the manufacture of such abrasive tools in order to improve the production of the desired cellular structure and improve the working characteristics of the grinding wheel; and, - an apparatus for the formation by centrifuging of such an abrasive tool, comprising means for the suitable ventilation of the excess gases of this apparatus.



   Other objects of the invention will emerge from the following description given with reference to the appended drawings, it being understood that the various embodiments which will be described and represented are only given for explanatory purposes and in no way limit the invention. On these drawings:
Figure 1 is a schematic elevational view, in partial cross section, of a circular mold mounted on a turntable or in a centrifuge and for the production of a rotating abrasive wheel according to the invention;
Figure 2 is a view similar to Figure 1, but showing a later stage of the process
Figure 3 is a vertical section

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 hold showing ur. later stage of the preceding;

  
Figure 4 is a vertical sectiona '¯. through the closed mold during the blowing and gelling or setting stage
Figure 5 shows an abrasive wheel obtained by the process illustrated in Figures 1 to 4,
FIG. 6 represents an abrasive wheel similar to that of FIG. 5, but on which suitable face plates have been added by molding,
Figure 7 is a cross section taken on line 7-7 of Figure 6;
Fig. 8 is an enlarged schematic view showing the arrangement of the abrasive trains and the binder resin during the initial centrifugation;
FIG. 9 is an enlarged view similar to FIG. 8, but showing the ratio and the shape of the chips and of the binder after the blowing;

   and,
Figure 10 is a diametrical section through one embodiment of the centrifuge mold.



   We will first describe the improved process which constitutes one of the aspects of the present invention, with reference to the aforementioned figures of the drawings. In this description, the matrix or binder material will be designated by the general term of “resin” or more particularly, “polyurethane resin”.

   However, it should be noted

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 EMI6.1
 .1U 1 "ir, le: take part I certß: .. de3 av-: r.tā- ± 88 I the pI ... S3 ::., = 1 nte :. ullld3.n: one ri ne other qu <; Li r0 = 1; e ùe ï o;, u: ti ::: re, COI: J.lt: for example a phenolic re,; ine me re3im =! epoxy, a natural rubber, the;. olyi :: or :: e, a resin of 'butf.idien-B, -yr m, buta.h "' n - '. r; rj 10n1 tr11e and olà7vinylt chloride ,, 1.; ic :; the state of foam or cell. GENERAL METHOD OF MANUFACTURING.
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 Gan can incorporate 1. n: a: ié;> e -1ùr-J.sive granular such as carburean. silicon or
 EMI6.3
 aluminum oxide, in: nélar., a polyurethane that has not reacted or has very much refagi, after which the reaction is completed in a mold a; prol;

  laughed? to form the desired abrasive tool. In general, a swelling or foaming agent is incorporated into such a mixture, approximately simultaneously with the incorporation of the abrasive into it, and the swelling or blowing which then occurs during the setting of the resin contributes to achieve a uniform, slightly spaced distribution of the abrasive grains in the body of the resin, and also helps. keep the grains in suspension previously. solidification. The rapid setting of the polyurethane resin prevents the grains from breaking up after they have taken their correct positions.



   However, in the manufacture of many types of abrasive tools, such as the novel abrasive wheels of the present invention, it is necessary to

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   uses a close one of the type shown in Figures 1 to 4 of the drawing. In these figures, we see an annular noule 1 .on: the bottom, -, 2 is attached d @ ns inside a turntable 3; whose rotation around its vertical axis is ensured by a mechanism 4 with worm and helical wheel, driven by an electric motor 5.



  The mold comprises a removable cover 6 having a central opening through which protrudes an axial tenon 7, the outer end 8 of which is threaded. At the initial stage of manufacture, a metered quantity of fluid or uncured resin, such as a polyurethane resin, is poured from an upper reservoir 9 into the central opening 10 provided in the cover 6 of the mold, and the turntable 3 in rotation to force the resin to flow radially outwards and to accumulate in the radially outer portion of the mold, as seen at 11. In this way, the entire radially outer half of the mold can be filled. mold.



   On fi ure 2, the following stage has been shown which is carried out at the same work station: it consists in discharging a metered quantity of abrasive grains from a hopper 12 into the rotary mold and, under the effect of the centrifugal force these abrasive grains flow radially outward and penetrate into the previously deposited resin, through which they migrate towards the radial peripheral area of the mold cavity, accumulating regularly in the area peri-

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 outer ring 13, and so that a relatively small amount of resin is sufficient to fill the gaps between the individual grains.



   We then come to the next operating stage which always takes place at the same station, a new quantity of resin is poured into the center of the mold, as can be seen in FIG. 3, so that the mold is substantially filled in three concentric zones. an outer zone 13, which contains a high concentration of abrasive joints separated by a relatively small quantity of binder resin, an intermediate zone 11 comprising a major proportion of resin in which is embedded a small quantity of abrasive grains, and finally a zone internal 14 which consists only of resin without any abrasive.



  Cn stop the rotation of the turntable and close the mold, as shown in figure 4, using a conical annular plug 15, an outer washer 16 and a nut 17 screwing on the tenon 8. Cn leaves the resin in the mold to harden or it is polymerized, as the case may be. For the profuse resin, that is to say polyurethane, the reaction of the ingredients constituting this resin is allowed to proceed to completion, which usually takes about 15 minutes at room temperature. After that, the molded article can be removed from the mold and kept at about 66 ° C for 30 minutes, after which it is ready to serve.

   If you want to get more rigid tools, you can leave them in the mold for two

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 approximately hours t heat them during this time to approximately 93 C.



   As indicated above, it is generally much preferred to incorporate into the resin a small amount of a blowing agent capable of forming a large number of tiny cells or voids in the body of the finished article.



  Depending on the particular type of blowing agent used, as will be explained in more detail below, it is desirable to heat the material while alla is enclosed in the mold, known as shown in Figure 4. In general, at this stage the mold has already. been removed from the turntable because centrifugation is undesirable during inflation. The tiny # cells or voids, which are usually in communication with each other, go a long way in lightening the wheel and saving on the amount of resin required. In addition, they serve to give the inner portion of the wheel a much greater elastic flexibility.

   In a particular form of structure, the interstices between the abrasive grains in the radially outer region where these grains are highly concentrated, instead of being almost entirely filled with binder resin, may themselves be relatively open, thus forming a fine-pored structure, so that the seeds which are exposed to the working surface of the tool, are not firmly embedded in the individual cells and their sharp edges are better exposed

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 for active work than in the.1 achievement.? earlier. We therefore obtain a much more efficient tool,

   while eliminating unnecessary waste of abrasive fears and notable wear of the grinding wheel, if a binder consisting of polyurethane resin is used, -depending on the embodiment of the invention, this resin is re-produced. - velant capable of achieving an unexpected force bond for abrasive grains, a bond whose effectiveness persists, even under the most severe working conditions and resulting from the fact that the resin only comes into contact with certain parts of the grains abrasives instead of drowning them almost completely.

   If a sufficient quantity of resin is loaded into the mold previously or simultaneously with the abrasive material, the inflation or foaming operation allows complete filling of the mold without having to make subsequent additions.



   We reduce even to the minimum. ; -excessive wear and damage to the abrasive tool due to the fact that the central part of the tool is; formed by an elastically deformable resin or in the plastic state to support the outer, rigid part and relatively hard which has the abrasive elements (moreover the outer portion also has a certain degree of elasticity): the way to absorb shocks. and the violent forces to which the tool can * be subjected when it attacks a part.

   Beer. that the inner zone

 <Desc / Clms Page number 11>

 
 EMI11.1
 ! "3eu: '', a> ;. i .îli:. = L. ''. '. T,;>. Diia'ùr u-n" a # w <ei; ...: .o l; force ei. rî f -Àgp 1 finding4 read In #>.> ne ew; ':: -: t>.' "i!; ii, = ;; do pr4ccntrainre = en, 4 .. ;; + c <,,.; :,;; "i, - = z, -. J course of the fabricA + 1 <Jr¯, c, + ¯l * i '" li:. ending a trend i :;; e.: a;. x ;; i ;; i iwe;,; 1't2rieur "him 3'oproe. ..ir.> "1'- '':.:;. r; *. = :, i '= excessive verp outside 1 in #er; .ics As we see in figures? 5 and'; 1: ..: re'.l *? = * rotary sive manufactured cosi'cm # 4re; .t .i Á'iVt4ion
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 presented orùinai-e ... in the usual cylindrical storyteller and a central opening 18 fo "::; / e r, r the" tenon 7 inside the mold, la = i'll ....

   C "7et'.e s-rvire later to receive a mandrel .vntuelle-
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 You can place in the wheel various types
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 of metal hubs and SL¯l - 1.: '- "" le .-- cwve'L-ros corresponding ap 3:'? i: S: i 'alcrs inc +; Li, or such part of the article tr #: 1 = .4, A: 8. :: 'i.o; e 6, a rotary abrasive tool, e? "#ensibi> re = .t similar to the tool repr8ser.t; - Figure 5, this tool having 4té 4galeIù.; nt fabriu'; ' 1 proceeds diagrammatically on fiue2 1 to :: is where thin annular front plates 2C -at 21 have been
 EMI11.5
 molded and attached to the finished article, these
 EMI11.6
 front plates 3 'extending from the central hole 18 to mandrel, raialee: .t to the outside and
 EMI11.7
 up to zone 13 with a high concentration of abrasive material.

   These frontal plates
 EMI11.8
 can be for.:. ée ::: in µle n; 4-lliq, àe or even in strong paper, car-or or in a ..¯a-: ièe plastic,

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 and besides providing relatively rigid surfaces intended: to engage with plates or clamps when the tool is mounted on a lathe or suitable mandrel, these faceplates have proved effective in initiating, or even eliminating, lateral buckling or the formation of protuberances of the resiliently flexible and substantially abrasive-free central portion of the tool, under the action of the aforementioned shrinkage or contraction of the abrasive outer zone 13.



  It is therefore in general preferable to incorporate such faceplates or equivalent elements, such as textile mesh discs or the like, for this purpose.



   Of course, instead of separately introducing into the mold the matrix or the binder, on the one hand, and the abrasive material, on the other hand, retorted it has been explained with reference to Figures 1 to 3, these two can be mixed. constituents beforehand and send them simultaneously into the mold in the same way as that used in the embodiment comprising separate incorporations.



  In this case, we must then close the mold, place it on the turntable, and rotate the latter, so that the centrifugal force thus developed causes the migration of a prc. predominant distribution of abrasive particles towards the outer peripheral zone of the mold cavity.

   If, as is preferred, a swelling agent is incorporated into the matrix or the binder material, this agent will be activated while the cover is.

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 1: ix <5 in! -! Ice, e CO: 1Tl! '. Áe: in: i. l Jl:>, 'e:': rt.:..èrte :: 51Jo ±> .1e 1 :::. 3 le: 6C (.:.; ... r. lf .... 3, ' ....:; e! '.;. :::.:. P -L -1 S -e-,; CO ::;: 2.8 "" I this ie ::. 2r5 L!. [;, .; c '.!:' :, cr. leads to char ;, trI fUe'eu ..,:! i, ac j ,; "1 '>; ctié; <; ie ;;; mo.iss éje oa until! .W 1'1. réi'r.ei * <+ /, 1.
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 less partially ';' J.rC18 0'1 r.'l1e. ov in ra = ¯¯: te, we can stop the tee at- :. this Irrigation.



  To explain one more important aspect of the invention, go to: alut, enir. : # refer to figures Gcl: 8 :: w.tiquen (5 and <1 which show, in very enlarged form, the successive stages: the production of the outer abrasive region of the grinding wheel in accordance with the invention. The figure shows how the abrasive grains 27 emerge densely agglomerated during centrifugation, with the interstices between these grains filled to a great extent with the binder resin 28, although some foaming already occurs.
 EMI13.3
 in this resin.

   After stopping the centriiugeaée and an additional foaming of the binder resin, the abrasive grains are separated from each other.
 EMI13.4
 as is generally seen in Figure Si, the spacing between the grains preferably being equal, on average, to the diameter of a grain. The resin is set in this state, and although the structure seen under the microscope appears rather complex, it can be summarily described as consisting of relatively thin coatings on the surfaces of the grains, which coatings are bonded to these grains and hold them in position, being united by

 <Desc / Clms Page number 14>

 
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 :, s: .... .. ¯ .. ¯ .. j "': t; * H- .. 0" "".



  : 'c: T; .t'- n n. : '"..,' 4.!" .E ",. ¯. ::" ': 4'; t ". ' ...: .¯ .. ::. I'cr.a: o \: ': r.'.: 3: -. L "'\ ::, ce :: ..)'. The 1 a ,at,: :.



  .c-.o.fi '1-J; rlrt ..) (1.À.X or di 'ltJH ri 1.,:, lt'.2' 29 1 30, '' * un tir.r.c ".u e t c 1 i3 c. n ...



  '' # - '' i.ire 3 '. The "pli'caux 2 \ <and 1C whose l, t-.:t., '" J3 conforms to the walls of the section in C (I: d',
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 i r: 1cu13be must L "" rf ':'. t: 1.: G'J.0; e! 1 :, co :::. e il e;.; teji4scnt4, to be exact rôjl14uer.? l'ill ie the other and therefore be mi erci: j3n, e b? e :; I, '::. NF:: -;.' ..: r.trûtol! 1ûr.; Ent: 32 whose goal '::, 3: de co :: forr., E:' the outer perimeter of L The new article must of course have an internal diameter cnricsç; cx <to that of the article and it must also have a radial thickness d ±: e1T-in ";

   Oven 11k its outer face comes into alignment with the outer edges of trays 29 and 30 ′ when all these parts are assembled. Preferably, this outer face of the ring 32 should have bevelled outer edges 33 and 34 and the transverse thickness of the ring should obviously match the thickness of the article to be molded.



   The plates or discs 29 and 30 have identical central openings 35 and 36,
 EMI14.3
 the diameter of which must fit 8 three times on the

 <Desc / Clms Page number 15>

 
 EMI15.1
 .¯ ¯. j. ' . ¯. : '¯, i? 1 'l to "-t, ir, 3.'. I îet'n121" '11? Ie.,' <3 'to' e.: ...: ....;. E ÀC.1 ': 'At :: -...': 'I "\. -'. E: =: - -02: F -:" ..- 'f.? 'lQ ".h C - ::!.], 12 ..? 18," ¯ ¯ ¯r? <±> 1 2- e: j ie .C :: 4:: "1." E: -f) r "é C ('." :. and: "' -: e ex ': e:.: ..! e "l: c'-. '],.': Îe3 '± Y, .7" 3 ::: .. ex "r 4- 40- ..- .:?], l;? fe "iiÀeÎ4e"; ... e; ...;: ..;: 3..s; .3e; "4 -:": '- -01:' sth "'...." "': : 'è :: -' e î r¯, Â ..., a:. :: ate .. - <1 '=:. <.::;. + -t = ce ..1.'¯ ... è ¯; - .. i "= i = .rr: .3: '4 the .. ^ .. ¯it: i' ... -'crcu ': i,.?!.: r' ..: ". e- :: t 02 ..



  I "1 1. ' ; tl t ± o'à2'n e r .l1: tel 1 "1 r o to i '.. Y: s le,? ? r. 13 -3.:,ro-! .. :(, we either C '::: -: ...:,. (! "" ...,' t 'r'31 on: .e ..: : flé '.1+ 3, "' on 1 '-1 ::: .. cn:.; 1:: F': ': ..": 1..1'v 32 ro "1"' ¯ " : 1 "Y":.::: .Cture de :: lo'llc .l :: 1 + - 'l:' e Le,;: lae '-, "1.;' X 2 é 3C 1 <1 ; en;. '' .. e: $ 'T? lte1Ient on!' $:. :: ea :: 32]? ", tl 'close :: a; -..- ¯. =., iten" l tes tlce: "'or: j: 1:" ::' '' 1 chancre C l recedes v ..: t.::- 1.:. 'tt CO: .VT :: e. it will be "re :. '¯': 1:, ..- ti''Sr at, ¯,> jin-;: '.' I * icns' r:, al-ticulir8 30r .. "t 1-i.3C r \ , -! ': ¯: .a-: e' i. '': H1: peI: ler.t of éaz Q through the opening ce:. + Rie? 'An jd3 çlate: z> x, 1: know , The? '. 2..ü 2 CC. ,,: 2 e'1' ''.;? E! 1t2, en r.alis ": des ..sv: e le ..; t2 ::.: ::: + -: - =:
 EMI15.2
 .iyy.ropr14s through the post 3c, the> nut, tî aim on this post and a sleeve or, :: 'o1À.rrea.i.

   Li which is "removable adjusted on the body of the tenon and tooth the goal is to interpose itself between the.3 plates 29 and 3C. The transverse thickness of this sheath must
 EMI15.3
 be 6dale n. that of the ring 32 in sor iui when 1 1 nut 40 is tightened on the tenon 36, the desired parallelism, -; between trays 29 and 30 remains whole.
 EMI15.4
 view to allow <3Cl1ap1-er.lent gases from the center of the cavity of ::: 01.:.1a68 annular C,

 <Desc / Clms Page number 16>

 
 EMI16.1
 1 post 3. 1 '<' cross 4C- e 'the rour- t-.jntt 4' 1 t- 'l'nh'nt <1; 1 U11n ""':;

  t1tll1dr, "o ci..alté". 4nnn 1 no. a pannnôe efsti t r- 1 4? 2 "loV'r'1nt freely you zum ends and radial passages 43 which communicate with the central passage, in the nut 4 @, the radial passages 44 in free communication with the flattened side surfaces of the tenon 38 and with which the aforementioned passages 43 also communicate;

   and in the sleeve 41 of the radiant passages 45 which communicate freely with the spaces provided by the flattened surfaces of the post
As a result, air or gas has the possibility of freely escaping from mold cavity C, in a substantially radial direction and inwardly, through passage 45 of sleeve 41 and thence or through. the passages 43 and the central opening 42 of the tenon 38, either through the space left free by the flattened surfaces of the tenon, from which the escape continues through the radial openings 44 of the nut 40.

   In operation, a mixture of the constituents of polyurethane, for example, and a granular abrasive is placed in the mold which rested in a suitable assembly allowing to keep the inner plate 30 and the ring 32 centered on the post 38, and then , the cover plate 29 was mounted in position using the nut 40, this cover plate also being centered on the whole of the fact that the tenon 38 and the ring 32 are necessarily centered with respect to this together thanks to the aforementioned frame. The foaming mixture must not,

 <Desc / Clms Page number 17>

 
 EMI17.1
 <> ti P>.

   IIA-N 1, r ",} lit 'ln1Ht'flneht In cnvi t4 de mO'tlafid Zut and a net al6t'O le moula eh rotntion around eto 1' Xe ita toJhOt1 38 p0hd, iht a duration not sufficient for elf, etuttr uno distribution UhitottiUt at 3.a 1818Hrt! nbruaivo dant loi 80tti S> 't'i th't'1' \ '! --tem di, ioule, be at a Vitogne euffittahtw to pttically prevent any mouoooéé at the r4..in this rotntidfi is stopped in. nnite or, all dU maina, Oh significantly reduces the vittâgd # polar pofttttre to the t'8ihl of foaming in order to completely fill the mold cavity, during which time the gat and the air in ex-
 EMI17.2
 these escape through 198 various ventilation passages described below. The resin is then allowed to set or bone, forming a substantially rigid structure, and the article can then be removed from the mold.

   With this procedure, one obtains grinding wheels in which the cells which separate the abrasive grains in the outer annular region are considerably larger than the multitude of cells formed in the radially inner or non-abrasive region. Finally, the bridges bringing together the cells in the said outer abrasive zone are thicker and more resistant than in the central zone.
 EMI17.3
 



  MATIR3 ABRASIVJ -
The type, size and quantity of the abrasive can be changed on demand to produce a wide variety of interesting products. It has been found that polymers of urethanes

 <Desc / Clms Page number 18>

 
 EMI18.1
 rr'o, ut '{! nt a high rate (]' '1rjhl'ence for 1 @ -! "ln =" ab: rJ \ l1if: 1 and the like, allowing a given concentration of tuls glaine abrtai fa in the working 1'31'tio, of the abrasive tool, the quantity of polyurethane deposited in the interstices between the grains and sgrtnnt?: the bonding to each other can be reduced even further by the incorporation of the swelling agent whose presence has the effect of creating a multitude of small pores or cells in these interstices.

   Not only does the abrasive tool thus formed exhibit great physical resistance, but it also has a much greater abrasive action on the work due to the decrease in the quantity of the binding resin in the region of attack, the grains. individual abrasives or other abrasive materials are thus more exposed to have an effective action on the work, while the quantity of resin coming into frictional contact with the tool.
 EMI18.2
 vage is reduced to such a point that any soiling of the part to be rectified is immediately removed,
 EMI18.3
 and in ... 3rd step, the heat loss generated by the machining itself is considerably reduced.

   



  We thus have a grinding wheel which operates more or less cold and causes little or no fouling and smoke.



   Among the abrasives suitable for this purpose,
 EMI18.4
 we can mention notaLi..3nt the silicon carbura. aluminum oxide, meri, garnet, talc, 11 ..: 1 ": -... 'or.cc, -dioxyl d3 siliceous lime and other products u: .. I.ie . ;; .- 'nre, depending on the nature of

 <Desc / Clms Page number 19>

 
 EMI19.1
 1 <, '1 <1' tr't'i- '' J '? 1 '. 1 '1; -', ..; ... '1la't t.'E. tzircb .1-s it ".i 1 '? ir,' 1b1'Hir. It !! 1 z: trh '.'8' itili!" r>. ' j rW cvl¯. ' > ion +, s 1j.!.: '1 (): r;: rqll'Jlai; eu variant I 5 nicnns' 2 mm, the usual 1,' ltl1: e is between about 45 nierons and about 0.49: : one and more frequently still between 250 microns and 700 microns.



   It was possible to form other abrasive tools :; interesting, in particular grinding wheels, by incorporating fibers the reinforcement in the # constituents of the reaction: among these reinforcements, it is worth mentioning the glass fiber, the monofilaments of "Nylon", of the sisal fiber, of the tampico fiber, steel threads, cotton and others. It has been found that the incorporation of these materials improves the wear resistance of the wheels.



  MATRIX OR BINDING MATERIAL
As noted above, it is much preferred to use the polyurethane resin to effect the driving and bonding of abrasive grains or other abrasive materials, and also to form the relatively non-abrasive inner region of new tools. according to the invention, such as rotary grinding wheels. One of the following processes can be used, for example, to obtain suitable polyurethanes:
1) A polyol, polyester, polyether or an alkyd resin is reacted with an isocyanate in the presence of a catalyst to improve

 <Desc / Clms Page number 20>

 the reaction rate.



   2) A polyol, polyester, polyether or an alkyd resin is reacted with an isocyanate to form a prepolymer containing an excess of isocyanate. This prepolymer is subsequently reacted in the presence of a catalyst such as an amine.



   3) A polyol, polyester, polyether or alkyd resin is reacted with a polyisocyanate.



   In breadcrumbs, polyurethanes are formed by reacting an isocyanate or diisocyanate with materials giving a positive reaction in the "Zerewitinoff" test (see "Polyurethanes" by Bernard A. Dombrow, published in 1957 by the Reinhold Publishing Corporation; New York, USA for further details on this process, and in particular the study made in this book on rigid, semi-rigid and flexible polyurethane foams).



   A particularly satisfying composition can be obtained with the following ingredients:
Parts by weight
Polyester 100.0
Toluene diisocyanate 35, C
Water 2.4
N-methyl-morpholine 1,3
Emery (250 microns) 100.0
Glycerol Monoricinoleate 1.0
These constituents can be mixed and

 <Desc / Clms Page number 21>

 
 EMI21.1
 VE. ': ,, a1 a-3i ::' un o '... h: 1 ..'; r .. :: pr10 q, # r form a '"..'? Ule 'T" .: '1 JF' or 1 :: article, :) 1 .1: Sl.r ..: of all fT'lB: s - à4ions 3îT'.s ?: 0n can 1.FEI r the dcjrë of ', (\ 'JO, 1'!, E lu r01y: .0r d'u.rth'1r.e er, -adjusting the amount of eru included in the mixture.



   Usually the ingredients are mixed at room temperature although they can optionally be preheated to lower the viscosity and increase the reaction rate. They are mixed for about a minute and poured into a rotating boil, the latter taking about 3C seconds, while the centrifuging takes about 45 seconds. The turntable is then stopped and the foaming is allowed for about 10 minutes to fill the central mold cavity and widen the outer peripheral abrasive zone r @@ ially inwards by spreading the abrasive elements due to their slight spacing.

   Another ten minutes may be needed for the initial risc and another twenty minutes or more for the final dose.



   The formation of the foam can obviously be carried out by any known process, taking into account the type of resin used, for example by whipping or batta ,, e, or by the incorporation of soluble granules which are subsequently removed. - ment of the solution, or by the introduction of gas under pressure. The term "foam" used in the present specification notably includes cellular structures without regard to the particular method used for their formation,

 <Desc / Clms Page number 22>

 
 EMI22.1
 'l' (oI: .lt; t;: '"r1er." ..: lu34: ". 1"' ,,:. .l1! J; ....



  ::, - 1. l "'the' 1 ::: .1 '' '1,.;.".:; f-! ": t'V .. i.'ilr4: e la j) q ..x, 4.zo ::; la ': 4C." , l.> P01 ': i'Jt ""'. qr.l 8lX: i!; J '91006f: 2enW o., e..r .:, r¯.aée:' l'lnv - :. ti - '. r. : 'effc t;,:,.) 1: 1: 11'-' n-: t: .x ch'ro Jor, te je ricin oil rr1: 'finh- "3 oil:! e castor oil > ?, o>: =. lFe d-xs ur.
 EMI22.2
 1 liter bottle jt J: 1 added slowly 2.:2 fi = dl130cyun'ttt ..! of tluènu. this: .. 5lun,; a, avjc a, ... 1 td-; ion, and pendd ... "1T 30 minutes, in heating the product p..na1 obtained at lt0 d laying one hour, one laize to cool at b5OC and we check it in doo boxes .3 'et .: an which are AcelldtJ8 and kept for later use.

   100 g of the prepolymer thus obtained can be mixed with C, 5 g of dimethyl siloxane and then 0.35 of distilled water is added.
 EMI22.3
 The flexibility of the urethane polymer can be adjusted according to the choice of polyesters which are prepared for example by reacting polyesters which are prepared for example by reacting the foam and., 4 g of di << thylothano1al? ine adapted to initiate the foaming reaction. ricinoleic acid or hydroxystearic acid
 EMI22.4
 with one of the following materials: 1-lol-1-ethylene glycol, propylene glycol, ethylene glycol, glycerol, pentaerythritol, castor oil.

   Other suitable polyesters can be formed by reacting adipic acid with diethylene glycol, trimethanol propane or ethylene glycol or by reacting phthalic acid with hexanetriol.



   You can also choose the amine catalyst to regulate the rate of amine formation

 <Desc / Clms Page number 23>

 
 EMI23.1
 .ié j, slj;.: 41. a '-: r.'thane, suitable catalysts 1-n, - ce tu ... ta .. t not - ::.:. er.t la tr14thj, lamine la: lé â.: i1171wLiraE: la di : -14-t: lyl-ar, .ii-io - thai-.ola, .iine 1 tri ^ ethar.ol3 .-: ine
It is also possible to use polyethers based on sorbitol and polyesters based on acid.
 EMI23.2
 I ".: inre :; for the production ru pol:, rurlth¯ne.

   It is possible to make 1> olyétiers such as l.olyoxrflLoylne-1 ;; col and polypropylene glycol with toluene diisocyanate to form polyurethan
 EMI23.3
 The polyst0r ,. suitable for the purposes of the present invention are illustrated by the following forms:

   Formula 1
Glycerol 4.0 moles
Adipic acid 2.5 moles
 EMI23.4
 Phthalic alloy C, 5 mol
Formula 2 Trimethylol propane 4.0 moles Adipic acid 2.5 moles Phthalic anhydride 0.5 moles
Formula 3 Glycerol 2.0 moles
 EMI23.5
 Penta4rythritol 0.5 5 mo13 Phthalic anhydride 1, C mol
 EMI23.6
 S4bacic acid 3.0 moles

 <Desc / Clms Page number 24>

   Drill 4
 EMI24.1
 Tri :: tthylol propane 3.0 moles Phthalic ahyàride 2.0 moles:

   formula 5
 EMI24.2
 G13 c $ itol 1, C mole
Phthalic anhydride 1.5 mole
We can change the proportions of the constituents in these formulas and still obtain satisfactory results.
The most satisfactory results are obtained when the water content in the
 EMI24.3
 Alkyd constituents of the mixture:> The content of 3üsocyanatr and alkyd resin is between 0.1 and 3.0% by iron. This water can be introduced in liquid form; however, it is also possible to proceed otherwise, for example by incorporating one or more hydrates of the metal salts. It is also possible to introduce wetting agents such as
 EMI24.4
 glj-c41.01 monoricinoleate contribute to the even dispersion of water in the alkyd resin.



   To make a satisfactory wheel, 162 g of an alkyd resin, as given in Formula 1, is mixed with 138 g of toluene 2,4-diisocyanate for 1 minute. To this mixture of alkyd and diisocyanate can be added an abrasive material, for example 330 g of molten aluminum oxide with a particle size of 0.51 mm.



  We place this mixture immediately in the mold

 <Desc / Clms Page number 25>

 
 EMI25.1
 ¯ 'cxi t el ... 1êUR? mil le:! t en î, itatio .. during ine rnlhutQ at JOCJ tou1'lI / minut approximately, Jii 1 1 ce aneuiT ,: ie inotilti <"1na a fnur b la teipeatur, from 121st anvif n where he was hanged two hours after that, 10 oils were removed from the fnub and cooled before removing in turn the entire millstone.



  Cri obtains payment for the grindstones eatisfaieantux by bringing certain mc) dif1catioh8 to the process which has just been described: For example, the abrasive material is premixed with the alkyd resin or with the diisocyanate to be then placed in the mixture. On the other hand, one can modify the composition of the alkyd resin by resorting for example to one of the formulas 2, 3,4
 EMI25.2
 or 5.

   In addition, the typa and the granulometry of the abrasive water can be imparted to the grinding wheel with the desired abrasive characteristics. Cn can modify the composition of the toluene diisocyanate in the mixture by using
 EMI25.3
 for example mixtures of toluene 2t4-diisoovanate with 2, o-diisocyanata d. = toluene.
 EMI25.4
 



  Satisfactory Leulea are also formed by preproducing the dialkyd rsine with the diisocyanate and then using an aminocatalyst such as N-methyl-morpholine, immediately.
 EMI25.5
 tament before pouring the mixture, 3 pre-rëaji of isocyanate with the abrasive in the mold.



   Despite the above-described cell construction of the improved grinding wheel, through the use of suitable resinous ingredients and no-

 <Desc / Clms Page number 26>

 
 EMI26.1
 tWnnh1nt. of poly> a "oi% i -k 'ype qui vimt' ectrr 1-
 EMI26.2
 written and having received with inocyinateir or dt 3 diioocynnetaa to form 111: olyurthan'3 substantially rigid, we obtain a grinding wheel having a cutting surface intended to engage with the work which is extraordinarily strong and ri-
 EMI26.3
 guide, if we consider it to be a whole, thanks to which we have the ability to perform precision ectifications to one. greatly increased speed.

   It is quite remarkable that despite the very rapid molding speed which can be obtained, the tool according to the invention is far from wearing out as quickly as the previously known grinding wheels,
 EMI26.4
 All the way to: z edges, and this tool does not require such frequent drying to maintain the desired precision. its cutting surface. In sowing time, we avoid the creasing of the work despite the exceptional depth of the passas that we realize and the
 EMI26.5
 superficial finishing net'ercn plus perfctio.1'1é of the work.

   It will readily be admitted that such a combination of advantageous properties would hardly have seemed possible up to now, considering a very rapid tool advance and a great depth of the cutting passes. place severe working stresses on the tool, and normally individual abrasive grains protruding from the tool surface would have broken or still formed deep grooves in the work surface. The observations made at
 EMI26.6
 nicroscope of the working surface of the new tool have detected that when a sharp blow is given to the

 <Desc / Clms Page number 27>

 
 EMI27.1
 tle [1 tr.lt1n ni'Y ':' \ L: "2 1:, '1j" 1: .lp lqns 1'1 nose <! ', 4;' 1 + il '1., l'! '. lâl '.JOna'. 01 '1 "11. F: tE3i'1L"! It.; 1-;:

  al'Ü ret la y¯olyur f thJ3.11 (cell which supports this grain yields '51a3a1ue! r, in and I way not'¯blr l: 1-3.lrér la rieidi'4 x / n4ral #' lE: 1 "> t! RL ce ase
 EMI27.2
 To a whole, and in this way, the individual Grain adjusts itself to neighboring fears without appreciably affecting the structure of the latter.

   When the tool is in use, it is quite obvious that individual grains protruding from the surface may tilt, turn over or lead to sink into the working surface when they come into contact with the tool. work, so that these grains take positions, at least during contact with the work, comparable to those of the adjacent cracks, from which it follows that the cracks which initially had an excessive projection are not likely to crease surface of the work or break on the surface of the tool.



   The grinding wheel or a similar abrasive article obtained according to the invention can be further improved by the incorporation into the gellable resin of a finely ground and inert material constituting an additional load, in addition to the abrasive material. Such an inert and finely divided filler can be, for example, diatomaceous earth, lime ivy, aluminum oxide, magnesium oxide, silicon carbide flower or mica. , and it must be regularly incorporated into the resin and have a sufficient finish.

 <Desc / Clms Page number 28>

 
 EMI28.1
 fi3ante for ..;. u 'at ..1Or.1nt du ce: ltrifugeea ..:; r;

   at the speed necessary to concentrate the abrasive grains at the outer periphery of the wheel, this load remains substantially unaffected and retains its uniform distribution in the resin. Such fillers can both strengthen the article and decrease the amount of resin required which is always expensive. In addition, such fillers, particularly finely ground mica, can be used to entrain a certain amount of absorbed or adsorbed moisture which contributes to a muuu.
 EMI28.2
 excessive amount of resin of h> olyU1 where it <3ile.

   Among the other advantages arising from the incorporation of the finely divided filler, it can be mentioned that it helps to prevent the deposition of the abrasive material and softening of the grinding wheel afterwards.
 EMI28.3
 centriiugeaôe, and that it serves et;: alley of sdent


    

Claims (1)

additional polishing ABSTRACT A - A method of producing an abrasive article characterized by the following points separately or in combinations. 1) It consists of centrifuging a mixture of abrasive particles and a binder resin to concentrate these particles in a localized area, 1; to cause the foaming of this binder to slightly space the particles, and to set this binder. 2) The mixture is centrifuged in a circular mold so that the parts <Desc / Clms Page number 29> EMI29.1 cule, - be uniforr ^: ans corc% 3iit -je !! .3ur con perimeter in: 'or.:'. N-t ur. abrasive tool (.:.: 'c'.la1.'f>. 3) We do not initially fill the noule with this mixture. -3, this filling 4t-, nt later aazur4; r the coussacu, the foam material: 3rd expanding radially inwards from the p-iri: turned towards the center. of the mold, this material having been removed slowly towards the periphery by the centrii7ugc:>., - ,, U. ) The pure moulo is ventilated on the central portion during the n: ou8U ..; e and 1 expansion inwards. 5) The resin used is polyurethane. 6) The resin is polyurethane which is relatively stiff after setting, and is prepared by reacting aromatic polyesters or polyethers with an isocyanate B - Process for manufacturing a molded article characterized by the following separately or in combinations: 1) It consists of confining a mass of a gel-forming and foaming resin composition to prevent it from moving outwards in a radial direction from a central axis; to rotate this;: weary of resin around this axis at a high speed to distribute the resin evenly and prevent the. bubble formation; and then slow down this rotation to allow the resin to foam by forming bubbles <Desc / Clms Page number 30> EMI30.1 King. :: - 1.ndQ RÓJ, &.: - '. 1 .; -'- to i rort10: 1C unl.n ,,:. [dlai! 1: 'd18t1Vt; c: t:! .I ,. s.t 4 ins li artH: l: l't: .. ¯! 1T'i:,: f. ' Ct3 4H! As'.1, and lù. bull.-j iàu.4. '' .: 'L1t.e ..- with àe parts 1 ;; zir.:; Jà; a; - a thin flua d.lni3 1 portion Intél'1eu:' ;! of the: m3. =, 3t 'leave EMI30.2 sar l cc:; oolt1on ac 3: lfier. 2)! n includes Í "'.. rt1cules aura-3ivo in cott mass du r4oina, jjo, uelluà3 particles as concentrate UOU9 the .. ft of the rotation in the outer portion containing the large bubbles, this particle? being 0J) ac. :: .I pir 00.] bubbles ut tant 8UP1 'rtéd3 1nn ±> Is c tions int, rm4j1air8 plus B1s8e8. 3) The r31n used is polyur th: .l: 1 ::. 4) We keep the seat for EMI30.3 the! moussaigoe lin3 a rapidly rotating mold. the predominant portion is ventilated slowly towards the interior: inante with excess gas is released, tge'1.nt of the plastic material, and we allow @ the plastic material to get caught with the remaining part of this gas to form a multitude of small cells in the mass. 5) The plastic material mentioned under 4 contains in mixture a solid granular material capable of moving radially outwards under the effect of the centrifugal force developed by the rotation of the mold, and a finely divided inert material which is not substantially not affected by this centrifugal force. <Desc / Clms Page number 31> C - Mold used to mold a material consisting of a.:! gel-forming and foaming resin \ ,; this roll being characterized in that it comprises two plates having corresponding central openings; a spacer ring interposed between these plates and concentric with the openings in them; a bolt introduced into these openings; a removable sleeve surrounding this bolt between the plates, this sleeve having the same thickness as the: said ring; and a nut for this bolt, so that these plates can be tightened strongly in contact with this ring, this bolt, the sleeve and the nut having communicating passages for venting the gas of the molding quality thus defined. D - As a new industrial product, an abrasive article characterized by the following points separately or in combinations. 1) It comprises a matrix of a foamed resin binder and separate particles of abrasive material incorporated in this resin, this body was substantially rigid but still resiliently at certain points to facilitate readjustment of the individual abrasive elements in service. to prevent these elements from being dislodged prematurely from the work surface This article or that the book is not creased by contact with said article. 2) This resin is cellular polyurethane having a permanent elastic action. <Desc / Clms Page number 32> siat,: nte. 3) This polyurethane is formed by reacting an aromatic polyther or polyester with an isocyanate. E - Moula characterized by the following points separately or in combinations: 1) = 1c comprises a substantially rigid annular body of cellular polyurethane in which abrasive particles are embedded, these particles being supported in the polyurethane portions between the cells whereby these particles are slightly spaced and susceptible to a slight movement relative to the working surface of the grinding wheel, when the latter attacks the work, so that the premature dislodging of the particles of this grinding wheel or the deep grooving of the work by particle tillers are avoided. 2) These abrasive particles are disposed only in the outer peripheral region of the grinding wheel, the inner portion thereof being formed of substantially abrasive-free cellular polyurethane. 3) The cells in the abrasive zone are larger than the cells in the inner non-abrasive zone.