US2664316A - Method of making brushes - Google Patents

Description

fn c Dec. Q9, 1950 c. H. wlNsLow, JR., ET AL 2,654,315'

METHOD 0F MAKING BRUSHES Filed Feb. `5, 1948 3 sheeis-sheet 1 FIG., 3 FIG.4

{NVIENT RS CHARLES H.Wl 5L VV H/5F2Y S.WILL ISTON Dec. 29, 1953 c. H. WINSLOW, JR., ET AL ZA-f@ TI-IOD OF MAKING BRUSHES Filed Feb. 5, 1 948 5 SheeSwShee 2 FIG.5 FIG.6

Dec. Z9, i953 c. H. wlNsLow, JR., ET AL METHOD OF' MAKING BRUSHES 3 Sheets-Sheet 3 Filed Feb. 5, 1948 FIG. IO

gill/Egal Elm mai.

FIGJZ IIIIIIII lNVENTORS NLOVV S ON A TORN YS Patented Dec. 29, 1953 UNITED STATES PATENT OFFICE METHOD OF MAKING BRUSHES ware Application February 5, 1948, Serial No. 6,426

1.1 Claims..

This invention relates to improvements in methods of making brushes, and particularly re.- lates to brushes madey with artificial bristles of plastic material, or possibly a combination of natural and artificial bristles.

The purpose of the invention is to provide a new and useful method of making the brush. Considered as a product, the bristles are held tcgether in an improved way and are also fastened to thev brush back or handle in an improved way. Also the construction of the brush permits less of the liber length to be used for fastening to the back or handle,.thus, in contrast to comparable brush construction, saving costly ber material. Considered as a method, the invention provides 'substantial manufacturing advantages as will appear when the method is explained. The disclosure is made as the invention would be used when adapted to the manufacture of a high quality brush for personal use, such asv hair or tooth brushes, shaving brushes and the like, although industrial brushes which are made with highly quality bristles, such as paint brushes and the like, are within the scope of the invention as will be pointed out in the claims.

For sometime past, quality brushes have been made with articial rather than natural fibers, particularly with artificial libers made of plastic material. Suitable plastic fibers are expensive, as are suitable natural bers, but the tendency is for natural fibers of comparable quality to be the more expensive, and increasingly so. For

this reason, as well as'their uniformity of size 1 ing manufacture,

In the routine manufacture of brushes with artiicial fibers, the 'methods long used with natural fibers areV still being generally followed essentially as they were in the brush manufacture when thelshift to artificial plastic bristles first began. The disclosure of the present invention will show a particular way to depart from the routine methods of brush manufacture to save manufacturing cost, or to make a better brush, orboth.

An importantinnovation and improvement of the invention involves Welding together all the bristles of plastic material at that end of a bundle or fknot .which is to be mounted in a brush back or handle. An additional feature of improvement involves ,not only welding the bristles togetherat one ,fend of the bundle, but also Welding that endof the bundle to the plastic back or handle of the brush. The way these and other features of improvement to be described can be practiced will be disclosed by illustrative examples indicated in the accompanying drawings and fully explained in the following description, the scope of the invention being particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is an elevational View oi a new and improved brush element made by practicing the invention, this particular element having all of its plastic fibers integrally welded together at one end and being adapted for use -as a shaving brush when mounted in a handle;

Fig. 2 is an elevational View showing a form of apparatus suitable for making the brush element shown in Fig. l;

Fig. 3 is a view, in sectional elevation, illustrating a method of joining the brush element of Fig. 1 to a shaving brush handle;

Fig. 4 is a view, also in sectional elevation, illustrating a method of forming the brush element of Fig. 1 and securing such element to a shaving brush handle in the same operation;

Fig. 5 is a sectional elevation similar to Fig. 4 but showing another method of integrally Welding the plastic bristles at one end and simultaneously welding that end in a brush handle;

Fig. 6 isa vertical cross section of a shaving brush handle with a metallic insert molded therein to serve `as an electrode for carrying out the method illustrated in Fig. 5;

Fig. "7 is a vertical cross section of a shaving brush handle showing the position and shape of a metal ferrule for'molding the welded portion of the bristles to form an ornamental addition to the handle;

Fig. 8 is a'view, in sectional elevation, illustrating a method of welding bristle ends together and securing them to a handle in the same operation by a transfer of `energy through the handle material;

Fig. 9 is a vertical cross section of an apparatus for inserting bristles through av brush handle for a predetermined portion of their length to form a stepped end on a brush or tuft of bristles and for welding thebristle endsretained in the handle together at the Sametime such ends are joined to the handle;

Fig. l0 is a sectional elevation illustrating how plastic bristles ina tuft may be joined together at their base and simultaneously joined t'o anotherv plasticv element vby dielectrically heat plasticizingthe bristle ends through the other plastic element;

Fig.V 11 is a vertical cross section of .an apparatus for inserting bristles through a tooth brush back (shown in elevation, partly in section) to form a stepped end on the tufts and to then dielectrically heat plasticize the bristle ends together bonding them at the same time to the tooth brush back; and

Fig. 12 is an elevation, partly in section, of a plastic brush having a plurality of single plastic bristles rather than tufts of bristles, each of which is secured in the brush by a heat plasticization of its end portion after insertion.

The brush element I shown in Fig. 1 has bristles 2 of plastic material integrally welded together at one end by a plasticizing of the collective bristle ends to form disc shaped weld 3, which hardens when the plasticized mass sets. This brush element i may be used in combination with a handle as a brush, or in a brush back as one of a number of tufts of bristles, depending on the size of the bundle of fibers selected.

Assume that a shaving brush is to be made. Nylon fibers are cut to bristle length and bunched to form bundle or knot 4 (see Fig. 2). Knot l is threaded through metal ferrule 5, which is of a size to hold the fibers closely packed at one end of the knot. The lower edge of ferrule 5 is spaced a short distance from the end of the knot d. One electrode of an electronic dielectric heating machine of available commercial form (not shown) is made in the form of a plate 6 held by an insulated handle portion 'I. This electrode plate 6 is placed, either manually or automatically, in contact with the ends of the closely packed nylon bristles protruding through the lower edge of ferrule 5. Ferrule 5 is the second electrode of said electronic 'dielectric heating machine. The electrodes are spaced apart as indicated With the dielectric plastic material (nylon is but one example of such material) of the portion of the bristles to be heated held between. This relatively short portion 8 of the bristles which is the portion to be heated is determined by the horizontal plane through the lower edge of ferrule 5 and the plane of the bristle contacting surface of electrode plate 6. With the parts in position as stated and as illustrated in Fig. 2, portion 3 of the bundle of nylon bristles is heated when the heating machine is put into operation. The nylon bers in portion 8 are heat plasticized by the electronic dielectric heating to the extent that they weld together into the form of solid disc 3. The placing of ferrule 5 determines the thickness of disc 3 since the disc can be no thicker than the distance between the planes above referred to. Disc 3 is preferably made only thick enough to give it the desired strength for holding the bristles. Because it is formed by the plasticizing of the bristles themselves, disc 3 can be much thinner than the thickness of a body of cement or other binding material as commonly used in holding bristles together for brush making purposes. The result is that expensive bristle material is more economically used. There is a larger proportion of the bristle length used for'the iiexible function of brush bristles than when the bristles are bound together in one end portion by the 01d routine methods.

The nature of the binding portion 8 in the example given is improved compared to its counterpart in the old brush products. The improvement follows from the fact that the solid bristle anchoring disc 3 is not only of the same material as the anchored bristles, it is chemically the identical material which comes from the bristles in the making of the anchoring disc. It is apparent that these circumstances provide substantially ideal conditions for joining the nylon bristies With their anchoring means. There are no joints between the material of anchor disc 3 and the material of plastic fibers 2.

After the disc anchor 3 is formed with the nylon bristles extending integrally and outwardly, ferrule electrode 5 may be slipped off the knot or may be left on and used in joining the bristles to a brush handle or back. By way of example, Fig. 3 illustrates how ferrule 5 may be left on the knot and aid in the binding of brush element I to a shaving brush handle 9. Handle 9 is made of plastic, which for this particular binding method illustrated in Fig. 3 preferably is a plastic having dielectric losses low enough not to cause great heating in the handle itself, such, for eX- ample, as polystyrene. Handle 9 may be hollow so that the brush parts may be assembled as indicated in Fig. 3. As shown in Fig. 3, ferrule 5 has been slipped down on the knot over disc 3, the latter yielding enough for the purpose, and inserted in the top of hollow handle 9. Ferrule 5 is simultaneously bonded to disc 3 and to handle 9 by the use of an electronic induction heater (not shown) which is connected to coil IG, made of conducting material such as copper, by wires II and l2. A high frequency electric current is passed through the coil and inducesl electric currents inside the metal ferrule 5 through the walls of handle 9. Such induced currents rapidly raise the temperature of the metal ferrule 5 in which they are set up and the heat conducted by the ring plasticizes the adjacent thermoplastic material of disc 3 and of handle 9 on either side of the ferrule and simultaneously bonds the ferrule to both disc and handle. A bracket or stand i3 suitable for holding the parts during the operation is indicated.

The above disclosed way of joining brush element I to a brush handle is a preferred way, however, this element may be fastened in a brush back or handle by any of the old routine ways, such as cementing or stapling.

A preferred way of forming disc anchor 3 and securing it to a brush back or handle is disclosed in Fig. 4. Nylon fibers are cut to bristle length, bunched to form a bundle and inserted through metal ferrule 5 as in the method for making brush element i shown in Fig. 2. The tightly packed end portion 8 of the bundle is put into hollow handle 9 which may be the same plastic as that of the nylon fibers, but in any event a thermoplastic of dielectric properties. Handle 9 contains therein groove I4. Metal ferrule 5 rests on top of handle 9 and is firmly held by clamp I5. Clamp I5 is joined to an electronic dielectric heating machine so that ferrule 5 acts as one electrode thereof. Plate 6, inserted in the hollow handle to contact bristle portion 8 as illustrated, serves as the other electrode. When bristle portion 8 is plasticized by the heat generated to form anchoring disc 3, a part of the plasticized mass is forced by an upward movement of plate 5 into groove I4. Thus a part of anchoring disc 3 is firmly secured in groove I4 of handle 9. in this arrangement, the operation of the electronic dielectric heating. machine forms the anchoring disc 3, welded to handle 9 as well as to the nylon bristles. The ferrule electrode 5 may be removed over the outer ends of the bristles, the other plate electrode B removed out the open end of tubular handle 9, and the assembly of bristles, anchor and handle is one form of the new quality shaving" brush products.` The open` end of the handle may be capped if desired,` but it-need not be as the shaving brush is substantially complete without capping'.

Ferrule may be molded as an insert in plastic handle 9 as shown in Fig. 5, in which case contact with the electronic dielectric heating machine is through yoke shaped part I6. Bristle portion 3 when plasticized Will form anchoring disc 3 Which will be held in handle 9 by the abutting edge of ferrule 5.

If ferrule 5 is molded as an insert in plastic handle 9, it may have contacting pins Il as shown in Fig. 6 through which current may pass in order that the ferrule can act as an electrode. of handleS as shown or may be ground off flush with the handle surface ifrdesired. `Or errule 5 may have a bell shaped flare-or flange at its base as illustrated in Fig. 7 and may be removed after the bristles are secured in the brush there by giving an additional ornamentation to the shaving brush handle due to the imprint on the plasticiz'ed material.

Fig. 8 illtstrates how the plasticizing of the bristle bundles end portion 8 may be accomplished by applying current through handle 9. Handle 9 has molded in it metal ferrule 5 and also a groove il. Band I3, positioned as shown, acts as one plate of a capacitorand ferrule ii acts as the other. Energyr is transferred from ferrule 5 to hot electrode plate t. `Handle 9 is made of polystyrene or any other such plastic material which is a good insulator for high frequency current, not having enough losses to cause great heating. The plasticized nylon fills groove il, and anchoring disc` 3 so formed is held in handle 9by both the groove i'i and the ferrule 5. l

We are acquainted with the invention filed in patent application Serial No. 572,449 by Charles Edgar Maynard on January 12, 1945, now Patent No. 2,488,873, November 22, 1949, and-Fig..

9 illustrates how the present invention may be used With relation to that one in fastening lthe bristles to the brush back or handle. In the figure, apparatus part I8 contains a stepped cav'- ity i9 of size, depth and shape to provide a desired contour to the end of a tuft of bristles or the.L other Aend Will be a short distance above metal ferrule 5 molded as an insert in handle, 9. Metal ferrule 5 rests on conducting plate 22 separated from apparatus part i8 byinsulation 23. Conducting plate 22 is connected to an electronic heating machine (not shown) 'so that ferrule 9 acts as one electrode of such machine and plate 24 of plunger 2l acts as the other electrode. When current is applied through these These pins may project beyond the sides' electrodes the iiber material betweenthe elecy monly ,used in tooth brushes,` nail brushes, hair brushes, and the like may be secured in its hold# A holding vmember 24 is shownr ing member. in the form of a block, however, it may beof .any shape or form desired. Holding member 24 contains recesses or blind holes 25 toreceive the ends of thermoplastic bristles 26 assembled together in tufts 21. One electrode 2B, connected to an electronic dielectric heating machine (not shown) by Wire 29, abutsv the holdingv member 24 in the area containingv the bristles whatever. such area may be. Theother electrode 3D.

connected to the electronic.Vv dielectric heating` advantageous when the holding member is. of.

transparent plastic material since staples will show and many cements tend` to discolor. It may be expedient in some cases to form the brush element I as shown in Fig. 1 and insert the element l into the holding member rather than inserting a tuft of bristles unattached to one another. The current passing between the electrodes and through the holding member will then bond the solid merged bristle `material to the holding member.

Fig. 11 shows an` apparatus similar to that illustrated in Fig. 9, but'extended vand modified for inserting and fastening bristles in a tooth brush, or other such brush having a thin Wall handle, such method of inserting and vfastening eliminating the necessity of trimming the tufts to a desired contour. Bristles 32 cut to thepsame length are clustered ltogether and fed intoholes 33 in apparatus member 34 Where they are forced by plungers 35 through holes 3E in tooth brush handle 3i into cavities38. Cavities 38 extend into conducting member 39; insulating member di? and base member 4l. The bottom portions of cavities 38, located in base. member 4|, arel stepped in size, depth and shape and plungers 35 have their ram ends Aof a shape similar to that of the base portions vof cavities 39, so as.

to provide a desired contour to the ends of the tufts when the bristles are forced down into the cavities. VWhen the ends of thebristles are butting yup. against thenbases or. f. the cavities the other ends will be slightly above the back of toothbrush handle 3i and abutting the ram ends of plungers 35. Plungers 3o are attached to a conducting member 42 which is connected With an electronic dielectric. heating machine (not shown) by Wire 43. These plungers 3&5 ract as one electrode of the electronic dielectric heating machine. Conducting member 39 forms the other electrode, being connected with the electronic dielectric heating machine by wire 44. High frequency current appliedthrough the electrodes plasticizes the bristle material between the electrodes and bonds itto the walls of the holes in the tooth brush handle. The brush is then removed from the apparatus and Ltheback ground and polished to remove excess plastic bristle material.

' In oneaspect of the invention, the -inventionis` also applicable in making :brusheshaving single bristles vof plastic material instead` of tufts or bundles. Fig. 12 shows one such brush having a number of single bristles each of which is independently fastened to the brush back or handle. The bristles 45 may be secured to the handle by the same method illustrated in Fig. l0, the bristle portion within the handle 46 being plasticzed by dielectric heating and bonding itself to the handle. Or the brush illustrated may be made by having handle i6 in two portions 46 and 46a and inserting bristles 5 through holes 41 in handle portion 46a, then heat plasticizing the ends of each bristle to form an enlargement or distortion 48 which will tend to bond itself into the base of handle portion 46a. When the bristles are thus secured to handle portion 46a, this portion can be then cemented or otherwise attached to the rest of the handle.

'Ihe disclosure up to this point seems sufficient for one in the brush art to practice the invention. There are a number of things useful to consider however which will help understand the nature of the invention so that it may be practiced not only in the several specific forms disclosed but also practiced when one meets the many other specific forms of brushes too numerous to add to this disclosure and which will require intelligent adaptation of the invention to practice it whereever useful.

The most useful aspect of the invention is the idea of making out of a part of the plastic mate rial of the bristles themselves the anchor which holds the bristles for brush use. The ordinary routine manufacture is to merely cement or bind the plastic bristles in material supplied in addition to the material of the plastic bristles themselves. One consequence is that in order to get a sufficient anchor it has been considered necessary to bury a substantial length of plastic material of the bristles in the material furnished for the function of the anchor. As compared to the practice of the present invention this common routine results in a waste of the expensive plastic bristles, because when according to this invention there is no joint between each bristle and its main anchor, the anchor element may be made smaller and less of the expensive bristle material need be buried away in the anchor.

This broad aspect is indicated in the structural arrangement of anchor and bristle material. It is one and the same material, its form being merely changed by heat plasticizing and setting under a molding action on the anchor portion alone. This form would be substantially the same even though a few natural bristles were assembled in the bunch of plastic bristles provided the latter were enough in quantity to makeV the anchor disc which binds the bunch as explained.

It will be appreciated from the description that in the form of Fig. 1 the anchor disc is of solid plastic material and that the plasticized bristle ends used to mold the disc need to be sufcient for the purpose. Where a brush tuft or knot is wanted with the bristles very close to one another where they root into the anchor, very little molding pressure is needed to form the disc solid. Where the bristles are Wanted in relatively different arrangement at the root" connection with the disc, they can be made so but more of their length would then be needed to form the solid material of the disc. As an alternative in getting all such material from the fiber ends, the same plastic material as used for the ber can be added in'powder form merely to ll out the spaces between the loose form of the bristles at their anchoring portion. The powder form of the plastic would then merely add itself when plasticized to the plasticized bristle ends and again the bristles and disc would be of one integral material.

The idea of Fig. 2 is to indicate the best Way to plasticize the bristle ends and make the anchor. Electronic heating machines to generate high frequency current are so well known that only the electrode applicators of such a machine are indicated to make their operation clear with regard to this invention. 'l'he electrode applicators shown need not be near the generator portion of the electronic heating machine but may be conveniently located at the work position. The electrodes may be made of any suitable material such as brass, copper or steel, and the ferrule electrode may be a band of any desired width or even a tube. Needless to say, the plate electrode may be in the form of a rod or bar and machined to the contour of any desired seal, or to a suitable shaped surface to produce any desired contour on the top of the brush element or tuft or bristles when pressed against the portions of the bristles which are to be sealed together. By adjusting the distance between electrodes any size weld may be produced. This is of special importance where bristle saving is to be eifected since only the desired amount of thickness in the welded disc formed determines the amount of bristle material to be melted up to form the disc. In most cases this disc can be wafer thin and still provide enough bearing surface for secure attachment to a handle of brush back.

When the electrodes of the electronic heating machine are positioned from one another with plastic bristle material between them, and the electrodes are carrying electronic power produced in the form of high frequency electricity by the electronic heating machine, heat is created in the plastic material by the action of the electronic power in causing molecular friction, all as is well known in this type of heating. The heat concentrated in the plastic material that lies between the electrodes causes this portion of the plastic bristles to soften, plasticize, and intermingle, thereby producing a bond which is substantially as strong as the material itself.

It is the intention to show in Fig. 3 a way of bonding the brush element formed by the operation illustrated in Fig. 2 to a brush handle or back. By Way of example the hollow shaving brush handle shown discloses one way of doing this. In Fig. 3, the brush element of Fig. 1 has the ferrule shown in Fig. 2 forced down over its welded portion. The problem then is to bond the welded portion to the metal ferrule and bond the metal ferrule to the plastic brush handle material A simple way of doing this is disclosed in Fig. 3, the metal ferrule being heated inductively by the induction coil around the portion of handle containing the ferrule. When the ferrule is heated suiciently the plastic handle material on its one side will melt sufficiently to bond to it as will the welded portion of the plastic bristles on the other side of the ferrule. The ferrule, thus embedded in the two plastic forms, secures the brush element to the handle without any actual contact being necessary between the two plastic surfaces.

The advantages of Fig. 4 as to method are apparent in that the task of Welding the bristles together at one end and of securing that end to a brush back or handle is done simultaneously 'andfin the lsame operation.4 Advantages as to jproduct follow in thata, positive seal can be ef f fected by allowing themolten plastic of the.A plasj'tioia'ed bristle portions "to ilow into the retaining groove shown in the handle and thus mold the welded end portion with a ange or ring seated in the retaining groove of the handle. The

ygroove provides a mechanical bond to supple ment the physical bond set up when the plastic @of the bristle material welds together with the plastic of the handle material. This welding of the two plastics willbe a suicient bond in most casesparticularly when using the same or similarplastics for bristles and handle material.

The ideaoFig. is to disclose' that the ierrule electrode shown in Figs. 2 and Il may be carried by the handle as an insert therein. In this mann ner-the ferrule will serve as ornamentation to the handle as well as for one of the electrodes by which electronic power is applied to bond bristle to `bristle and bond plasticized bristle material to the handle material. By inserting the ferrule as shown, an additional securing advantage is derived since one edge of the ferrule affords a ledge which-tends to prevent the welded form of brisltle 4material lying behind such ledge from conrin-g out of the brush handle. The bonding of plastic bristle material to handle material by which avoids the need of a subsequent operation to trim or shape the outer end of the bunch of bristles into desired form. In the operation indictated, the lower ydie forms a bottoming form for the outer ends oi the bristles so that as the l:formed electrode at the yupper ends of the bristles `is pressed down in the heating operation the `outer iormwill be retained.

Fig. le is to show how a tuit of bristles may be attached to aI brush back in brushes where it is 'desirable to keep uniform and unmarred the eX- terior surfaces of the plastic back material that cover and completely surround embedded bristle ends. In such cases, the bristle ends are usually yen'il-3e'dd`ed in the brush back only to a depth necessary to firmly secure them. These bristle 'ends are then visible in the product, particularly when embedded in transparent plastic material. Staples or cement generally have been used as the Yleast inconspicuous means of holding the bristles in the brush back, but both are usually readily visible. Also, needless to say, the stapling "is expensive and the cementing difficult Rejects "commonly occur with the best 4of stapling machines and discoloration or deterioration with rmostr cements. jpresent invention these objections may be avoided, the bristle ends being properly plasticized to- Under careful practice of the gether and making an almost invisible bond to the brush back by dielectrically heating them through the brush back itself'in the manner shown inthe ligure.

n The purpose of' `Fig. il is to disclose how'the present invention may be used in the making of tooth brushes, nail brushes or the like, so as to 'retain the tutt shaping 'feature 'shown in'Fig. 9V "and eliminate ,a subsequent trimming operation.

Y El() This method'shown is `applicable inV making any brush having steppedor shapedtuft ends, where the bristlesy can jbe inserted through the brush back; Fig. 9 illustrating a method more adapted to the making of shaving brushes, paint Abrushes and the like.` t A l In Fig. 12 the idea disclosed shows how the invention is adapted to making brushes having singleplastic bristles individually secured ina plastic brush back or handle. Any one of the methods disclosed are useful in making this type of brush. '.Ihe singleV bristles may be attached to the handle or back inthe same manner as the tufts of bristles in Fig. 10, or they may be inserted through the brush back and secured as shown in Fig. 11. As has been described, still another way ci securing the single plastic bristles would be to make the plastic handle back in two members, insert the bristles through holes in one member, plasticize the ends of the bristles to bond with thewholding member or to distort them so they couldY not pull out and then bond the two members together to form the brush.

Having fully disclosed our invention, we claim:

l. The method of constructing brushes which comprises assembling a plurality of dielectric thermoplastic bristles in tutt form, conning said tuft adjacent its base with a metal member, said member being spaced from the base of the tuit but suiciently close thereto to hold the base portions of the bristles extending beyond the coniining means closely packed, positioning an electrode across the base of the tuft and placing said metal member and said electrode in circuit with an electronic power generator to thereby fuse the material of the bristles between the metal member and electrode into a unitary block.

2. The method of constructing a brush which comprises assembling a plurality of dielectric trermoplastic bristles in tuft formA encircling the tuft of bristles adiacent'its base with a metal member of sucient size to hold the extending base rortions of the bristles in closely packed parallelrelation, positioning a metal plate member across the base of the tuft and placing the metal members vin circuit with an electronic power generator to' thereby plasticize the material of the portions of the bristles lying between the metal plate member and the adiacent edge of the encircling metal member, while applying sufcient pressure to the base of the tuft to form the so-n-lasticized portion into a solid block.

3. The method of constructing a brush which comprises assembling a pluralty of dielectric thermoplastic bristles in tuft form, encircling the tuft of bristles adjacent its base with an electrode in the form of a ferrule, the ferrule being of suilicient size to hold the extending base portions of the bristles in closely packed parallel relation, applying a second electrode across the base of the bristles, and while holding the bristles tightly packed between said electrodes passing an 4. The method of constructing a brush which vcomprises assembling a plurality of dielectric thermoplastic bristles Ain tuft form, encircling the tuft of bristles adjacent its base with a metal member ofsuiiicient size to hold the extending base portions of the 'bristles in closely packed parallelrelation, forming a supporting member of a thermoplastic material having lower dielectric losses than the bristle material and providing said supporting member with a tuft receiving opening, inserting the base portion or the tuft within said opening, positioning a metal plate member across the base of the tuft and placing the metal members in circuit with an electronic power generator to thereby Dlasticize the material of the portions of the bristles lying between the metal plate member and the adjacent edge of the encircling metal member while applying sufficient pressure to the base of the tuft to form the so-plasticized portion into a solid block and simultaneously weld the block to the sides of the opening.

5. The method of constructing a brush which comprises assembling a plurality of dielectric thermoplastic bristles in tuft form, forming a supporting member of dielectric thermoplastic material having lower dielectric losses than the bristle material and providing said supporting member with a tuft receiving opening, positioning the base of the tuft in said opening with a metal electrode encircl'ng the tuft adjacent the mouth of the opening and with a second electrode positioned across the base of the tuft and connecting said electrodes in circuit with an electronic power generator to thereby plasticize the material of the portions of the bristles within the opening and between the electrodes and simultaneously form said plasticized material into a solid block and weld it to the wall of the opening.

6. The method of constructing a brush which comprises assembling a plurality of dielectric thermoplastic bristles in tuft form, forming a dielectric thermoplastic handle member, the material of the handle member having lower dielectric losses than the material of the bristles, providing said member wth a tuft receiving opening having a recess in the wall of the opening,

positioning the base portion of the tuft in the opening with an electrode encircling the tuft and spaced from its base and with a second electrode positioned across the base of the tuft, and placing said electrodes in circuit with an electronic power generator to thereby electronically fuse the portions of the bristles between the electrodes into the form of a unitary plastic block and bond the block to the wall of the opening, while applying suiiicient endwise pressure to the tuft to cause the fused plastic of the bristles to iill said recess.

7. The method of constructing a brush which comprises forming a brush back of dielectric thermoplastic material having a plurality of brush receiving openings, placing said back between metal members, one of said metal members having openings algned with the bristle receiving openings of the back, inserting the base portion of the bristles of dielectric thermoplastic material through the opening in the metal member and into the aligned openings in the back, and connecting said metal members in circuit with an electronic power generator to thereby electronically fuse the material of the base portion of the bristles within the openings in the back and weld the fused material to the walls of the back openings.

8. The method of constructing a brush which comprises assembling a plurality of dielectric thermoplastic bristles in tuft form, forming a supporting member of a thermoplastic material having lower dielectric losses than the material of the bristles, providing said supporting member with a tuft receiving opening extending therethrough, xing a metal ferrule in one end of said opening, inserting the tuft endwise through the opposite end of said opening by means of an electrode engaging the base of the tuft, advancing the electrode and tuft to position the base of the tuft in said opening spaced from the adjacent edge of the ferrule, and placing said ferrule and electrode in circuit with an electronic power generator to thereby plasticize the material of the portions of the bristles between the electrode and the adjacent edge of the ferrule to form said plasticized material into a solid block and simultaneously weld it to the wall of the opening.

9. The method of constructing a brush which comprises forming a brush handle having an opening extending completely therethrough with a metal ferrule fixed as an insert at one end of the opening and extending therein for only aV portion of the depth of such opening, placing and securing the brush handle on a work tool hav-Y ing a cavity so that the opening in the former is in register with the cavity in the latter, said cavity in the work tool having its bottom stepped in shape, placing a second work tool on top of the brush handle so that a corresponding opening in the second work tool is in alignment with the opening of the brush handle, assembling bristles substantially of the same length in tufted form, inserting such tuft into the opening in the second work tool, putting a plunger having its ram end of similar stepped shape as the bottom of the cavity into the'hole opening in the second work tool and against one end of the tuft, forcing the tufted bristles through the aligning openings of the second work tool and the brush handle by the plunger so that the tuft is advanced into the cavity of the rst work tool until the forward end of the tuft is shaped by the engagement of thegbristle ends with the stepped bottom of the cavity, the bristles in the tuft being of a length such that when one end of the tuft abuts the bottom of the Cavity the other end will be in the opening in the brush handle and extending beyond the metal ferrule; when the tuft end has been so shaped and the bristles so positioned, applying a high frequency current from an electronic powergenerator by connecting the ram end of the plunger and the metal ferrule in the circuit of said generator to plasticize the bristle material between the ram end of the plunger and the adjacent edge of the ferrule and simultaneously bond the plasticized portion of the tuft to the handle.

10. The method of constructing a brush which comprises placing a brush back having an open ing therethrough on a work tool having a cavity therein so that the opening and the cavity are in alignment, the cavity having its bottom generally cone shaped, placing a second work tool having an opening therethrough on top of the brush back so that the openings in the second work tool and brush back register, assembling bristles of substantially the same length in tuft form,Y inserting such tuft into the opening in the second work tool, inserting thereafter a plunger having its ram end of similar shape as the bottom of the cavity in the rst tool, forcing the ram end of the plunger against the adjacent end of the tuft, to advance the bristles of the tuft through the second work tool and through the brush back until the forward ends of the bristles in the tuft abut the bottom of the cavity and the bristles are so disposed in the tuft as to give the tuft a shaped end similar in contour vof the bottom of the cavity, the bristles being of such lengths that when one end of the tuft abuts the bottom of the cavity the other end of the tutt Will be in the brush back, applying high frequency current from an electronic power generator, by using the rain end of the plunger as one electrode and the top surface of the first Work tool as the second electrode to dieleetrically plasticize and merge the bristle material between the two electrodes and bond such material to the brush back.

11. The method oi securing dielectric thermo' plastic bristles in a handle member formed ci dielectric thermoplastic material and having openings in which the base portions of the bristles are seated which comprises, positioning a metal electrode in encircling Contact with the bristles at the mouths of the openings, positioninsr a second. electrode across the bases of the openings, and placing the electrodes in circuit with an electronic power generator to thereby le plasticize the thermoplastic material of the bristles Within the openings and bond the plasti cized material to the Walls of the opening.

CHARLES H. WINSLOW, J R. HARRY S. WILLISTON.

References mieli in the le of this patent UNETED STATES PATENTS .Number Name Date 2,172,433 Churchill Sept. 12, 1939 2,263,681 Hart Nov. 25, 1941 2,294,480 Rohweder Sept. l, 1942 2,303,800 Swann Dec. 1, 1942 2,322,903 Wilkoh" June 29, 1943 2,341,823 Smith Feb. 5, 1944i 2,372,929 Blessing Apr. 3, 1945 2,397,471 Cox Apr. 2, 1946

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