US3107382A

US3107382A - Brush strip for power-driven brush

Info

Publication number: US3107382A
Application number: US148189A
Authority: US
Inventors: Ralph F Tilgner
Original assignee: Pittsburgh Plate Glass Co
Current assignee: PPG Industries Inc
Priority date: 1961-10-27
Filing date: 1961-10-27
Publication date: 1963-10-22
Anticipated expiration: 1980-10-22

Description

1963 R. F. TILGNER 07,382

BRUSH STRIP FOR POWER-DRIVEN BRUSH Filed Oct. 2'7, 1961 3 Sheets-Sheet 1 FIG.

ATTORNEY Oct. 22, 1963 R. F. TILGNER 3,107,382

BRUSH STRIP FOR POWER-DRIVEN BRUSH Filed Oct. 2'7, 1961 v 3 Sheets-Sheet 2 INVENTOR.

Y 240% A r/za/vae (9 m;

Oct. 22, 1963 R. F. TILGNER ,38

BRUSH STRIP FOR POWER-DRIVEN BRUSH Filed Oct. 27, 1961 s Sheets-Sheet 5 FIG. H FIG. I!

INVENTOR. RALPH I? T/LG/VISQ ATTOE/YEY R locking core.

, of this construction will be apparent.

ration of Pennsylvania Filed Oct. 27, 1961, Ser. No. 148,189 8 Claims. (ill. 15-182) This invention relates to a brush construction and it has particular relation to a brush construction comprising means for locking the filamentary core in the channeh like backing of a brush strip which is spirally wound upon an appropriate mandrel.

It has heretofore been proposedto fabricate a powerdriven brush by spirally winding a continuous brush strip formed by locking doubled fill material in a channellike backing element by means of a filamentary locking core disposed in the bight portions of the fill material.

Such brushes are relatively cheap to manufacture because an appropriate backing element can be formed from a continuous metallic tape by means of rollers or other instrumentalities, and at the same time, the fill material may be forced into the channel backing element and locked by the filamentary locking core by use of available automatic machinery. The resultant brush strip can then be wound as it is formed upon a mandrel, to which the ends of the strip are secured in well-known manner, as by welding, or by screws or clamps, thus pro viding a finished rotary, power-driven brush.

Although the process of forming such "brushes is relatively inexpensive to operate, certain objectionable features are often encountered in connection with the resultant brushes and the operation thereof. For example,

when the brushes are driven at high speed, as is otfiten Q desirable in brushing operations, considerable centrifugal force is exerted by the fill material against the filamentary Often, the ends of the strip become loosened by the force, or in some instances, the filamentary locking core holding the fill material may be broken by tensional forces, in which event the fill material is released. This material, as well as the core, may be thrown or ejected at high speed from the brush, thus producing a hazard for personnel and equipment that may be in the vicinity. Moreover, when the brush is running under load, the fill material may sometimes be impelled by the tangential forces exerted, causing it to migrate along the channel backing element. Such migration may throw the brush out of balance, setting up severe vibration, and may force the side walls of the channel backing element apart. There is then a likelihood of loss of the fill material at some point or ponts along the length of the spiral. When such loss is once initiated, the contiguous fill material is left unsupported, so that progressive breakdown of the brush structure at an accelerating rate may result.

In order to reduce the possibility of the filamentary locking core becoming loosened or displaced from the channel backing element and thus permitting loss of the fill material, and also to prevent migration of the fill material in the channel backing element, it has been disclosed to form the side walls of the latter element with integral tabs or teeth projecting inwardly and being adapted to engage the outer perimeter of the filamentary locking core to hold the latter in place. Disadvantages For example, in order to provide teeth of adequate strength, it is necessary to form substantial cuts in the side walls of the channel backing element, thus greatly weakening the side walls against the effects of tensional forces such as may occur in the circularization of the strip when it is wound around a mandrel or core. Rupture or tearing of the United States Patent the construction.

2 outer perimeters of the side walls at points Where the cuts have been made are then very likely to occur.

It will also be evident that teeth merely projecting as cantilevers secured at one end to the sidewalls are not very strongly supported. When a strip embodying such construction is subjected to severe bending, as when the brush is rotated at high speed, the centrifugal force exerted upon the filamentary locking core may tend to stretch or dislodge the same, thus allowing the core to exert considerable radial force against the teeth, whereby the latter may be distorted or bent outwardly so that the filamentary locking core becomes dislodged from the locking teeth and the construction may fail in the manner already described.

A further disadvantage of the conventional construction resides in the fact that the fill material looped about the locking core is a poor conductor of heat, such as is often generated in the brush when the latter is subjected to heavy workloads; Sincein the conventional construction there is no effective metallic path for conduction of this heat radially away from the interior of the brush, it tends to build up to an excessive degree in the zone about the filamentary locking core and often shortens the life of The present invention comprises the provision of a rotary, power-driven brush formed from a spirally wound strip element in which the locking core holding the fill material in the channel backing element is formed from a continuous tape having formed therein a series of closely spaced, projecting teeth, the tips of which are locked in or under appropriate shoulders or ridges disposed within the channel backing element at proper height. These teeth, by engagement under the shoulders within the channel, effectively hold the filamentary locking core from dislodgment by centrifugal force. The formationoct the teeth in no way weakens the side walls of the channelbacking' element. The teeth also provide paths of high heat conductance from the inner zones about the locking core outwardly to the side walls where the heat is more readily dissipated by the air currents circulatin'g between the turns of the brush.

For a better understanding of the invention, reference may now be had to the accompanying drawings wherein like numerals refer to like parts, and in which:

FIGURE 1 is a side elevational view of a brush formed of a strip which has been constructed in accordance with the provisions of this invention.

FIGURE 2 is a fragmentary side elevational view of a brush strip embodying the principles of the invention, before it has been spirally wound to provide a powerdriven brush construction.

FIGURE 3 is a diagrammatical view illustrating the shaping of a simple metallic tape element to provide a semi-formed [channel backing element in accordance with the provisions of the present invention.

FIGURE 4 is an end elevational view showing the roperation asjdisclosed in FIGURE 3, but from another angle.

FIGURE 5 is a diagrammatical view illustrating the formation of a metallic strip or tape element into a locking core element embodying teeth and'being adapted FIGURE 9 is a plan view of a tape which has been so cut as to provide the tabs for the teeth of the locking core illustrated in FIGURE 8.

FIGURE 10 is a fragmentary end view showing the winding of the finished strip in forming the brush illustrated in FIGURE 1.

FIGURE 11 is a sectional view of a tape from which an embodiment of channel backing element may be formed.

FIGURE 12 is a sectional view illustrating the tape as shown in FIGURE 11 in a later stage of formation.

FIGURE 13 is a sectional view illustrating a further step in the fabrication of a brush using the tape shown in FIGURE 11.

FIGURE 14 is a fragmentary sectional view illustrating the initiation of the operation of inserting the filamentary core and the fill material in the partially formed channel backing element of FIGURE 13.

FIGURE 115 is a diagrammatical view illustrating the shaping of the brush strip into its final sectional form.

FIGURE 16 is a sectional view of a modified form of brush strip. 1

FIGURE 17 is a sectional view diagrammatically illustrating a die through which a tape is drawn in order to provide a channel backing element of the strip shown in FIGURE 16.

FIGURE 18 is a diagrammatical view illustrating an initial stage of inserting the fill material and the filamentary core in the partially formed channel backing element after it has passed through the die.

FIGURE 19 is a diagrammatical view illustrating the shaping of the partially formed channel backing element shown in FIGURE 18 to final form.

FIGURES 20 and 21 are sectional views showing further embodiments of the invention.

FIGURE 22 is a view partly in section and partly in elevation of a further embodiment of locking core which may be used in the practice of the invention.

FIGURE 23 is a sectional view taken substantially upon the line XXIII-XXIII of FIGURE 22.

In accordance with the provisions of the present invcntion, a metallic tape or metallic ribbon, indicated at 26 in FIGURE 3, is drawn from supply roll 27 and is partially formed to channel shape, as indicated at 30 in FIGURE 4, wherein it has diverging side walls 30a and a connecting web or bottom portion 30b therebetween. Ribs 29 in walls 30a may be continuous or broken into short sections as preferred. Any appropriate embodiment of apparatus may be used so partially to shape the channel, although for purposes of illustration, it may comprise a pair of

rollers

31 and 31a, the lowermost of which is peripherally grooved, as indicated in FIGURE 4 at 32, the groove being of a sectional shape corresponding to that of the sectional shape of the semi-formed channel. The upper roller, as shown in FIGURE 4, is cyclindrical and of a width to clear the inwardly projecting ribs 29. The roller 31 is illustrated as being mounted upon the mandrel 36 and the roller 31a is mounted on mandrel 36a driven at appropriate speed by power means (not shown).

In forming a brush strip using a semi-formed channel backing element such as is illustrated in FIGURE 4, various embodiments of locking core C may be used. The design and formation of one such core is diagrammatically illustrated in FIGURE 5, wherein a tape or strip 37 of metal of appropriate thickness and width is drawn from supply roll 38. At one stage, it is subjected to a dieing operation by passing it through a press, the housing of which is shown at X, in order to cut out spaced portions 39 along the edges. Obviously, the portions 39 could be cut out by a stamping or punching operation before the strip is coiled. The strip may also be partly transversely bent to provide a shallow channel, as at SC, as by rollers 40 preceding the dieing apparatus X.

The portions of metal left standing between the cutout portions 39 provide laterally extending teeth 41. The strip having the cut-out portions may be passed between a pair of rollers 42 and 43 having the outer perimeters thereof shaped to deepen the shallow channel to form a U-shaped channel or rib portion 44, shown in FIGURE 5. The finished locking core is thus provided. The sectional shape thereof imparts high resistance to bending. The core can be used directly in assembling a brush strip in a continuous line operation or can be stored for subsequent use.

The formation of a brush strip using the semi-formed channel shown in FIGURES 4 and 12, and the core element shown in FIGURE 5, is shown in the progression of views in FIGURES 13, 14 and 15. As illustrated in FIGURE 13, a continuous semi-formed channel element with divergent side walls 30a having ribs 29 after the shaping operation obtained by the

rollers

31 and 31a, is passed over a suitable grooved carrier roller, or a series of such rollers, illustrated by the roller 46 which has a peripheral groove with

sides

47 and 48 connected by a bottom portion 49. The semi-formed channel, as it progresses over the roller and/ or rollers 46, receives a layer of fill material 51 which may comprise any suitable filamentary material, such as steel wire, Tampico, Nylon, cellulose acetate, or other filamentary material. Preferably, this material is of double length, i.e., of such length that it can be doubled to hairpin shape about the locking core. The layer of fill material may be laid down manually or by an automatic stock picker device of well-known structure.

The channel with the fill material disposed thereacross, travels to a second roller 53, also having an appropriately shaped groove about the perimeter thereof and being designed to retain the semi-formed channel backing strip in place. At this stage, a locking core, usually in a continuous strip, such as the toothed core element C, illustrated in FIGURE 5, is brought down upon the top of the layer of fill material and is forced down firmly into the channel as by means of a narrow roller 54 disposed upon a power-driven shaft 56 and having an outer edge designed to ride in the channel or rib 44 to maintain the locking core in accurately centered relationship with respect to the channel backing element.

Rollers

53 and 54 oppose each other and exert pressure to force the core C and the fill material into the channel.

The partially formed strip then passes through one or more sets of bending rollers designed progressively to bend the side walls of the channel backing element upwardly into final form, wherein they are pressed firmly against the fill material, the elements of which have now been bent to final hairpin shape. The teeth 41 in the same operation are also engaged at their tips under the ribs 29, thus firmly securing the locking core in the channel at closely spaced points. One set of rollers for finally forming the channel is indicated in FIGURE 15 and comprises a cylindrical roller 57 upon a power-driven shaft 58 engaging the bottom portion of the channel backing element. The side walls 30a of the channel backing element are bent into final position, as by means of an opposed pair of

rollers

59 and 61 mounted upon shafts 62 and 63 which are carried upon appropriate fixed arms 64 and 66. If desired, these rollers (59 and 61) each may be provided with peripherally extending ribs, as at 68 and 69, engaging in the longitudinally extending groove formed by the ribs 29 in the side walls of the channel backing element. The

ribs

68 and 69, it will be apparent, are optional features and often are not required. In the final form of the brush strip S (FIGURE 2), the teeth 41 are held below the ribs 29, which thus provide one form of abutments to lock the teeth in place against centrifugal force.

The brush strip, as it passes from the rollers illustrated in FIGURE 15, is in the form of a substantially straight bar, a small section of which is illustrated at S in FIG- URE 2. This strip may be circularized or spirally wound upon a drum or mandrel M ("FIGURE of a brush substantially as it is formed. The operation is diagrammatically shown in FIGURE 10, wherein a power-driven H winding shaft is indicated at 71. This shaft may be permanently retained with the brush or may be removed and replaced by another supplied by the user. The shaft is provided with a keyway and key 72 providing a driving connection between the shaft and the bushings 73 in the drum or mandrel M of a rotary, power-driven brush. Upon the outer perimeter of the bushings is disposed a sheet metal, cylindrical liner 74 and upon the outer perimeter of the liner is disposed a longitudinally corrugated outer shell 76. corrugations 77 of the latter may be secured to the liner 74 as by welding, indicated at 78. It will be apparent that screws, rivets, or other fastening means may be employed to secure the crests of the corrugations to the latter shell. The brush strip,

from the forming operation shown in FIGURE 15, is

attached to the drum or mandrel M at one end thereof by appropriate means, such as electrical welding of the channel backing to the liner 74, or by screws, clamps 740 (see FIGURE 1) or by any other means. The shaft is rotated at appropriate speed to take up the brush strip S as it is formed and to deposit the same in a series of spiral turns T on the shell 76. When the proper number of turns have been formed on the shell, the strip is cut and the side walls are squeezed together, as at W. The free end is attached to the shell to provide a finished brush B, shown in FIGURE 1. The brush may remain on the shaft 71 or may be removed for application to a shaft in the apparatus used by the purchaser.

The brush may be mounted for driving in any convenient apparatus. and/ or under heavy loads. The teeth 41 on the locking core C will hold the latter from displacement. The teeth will also hold the stock from migrating in the channel backing. If for some reason a tuft of stock should be loosened or lost, the loss is limited to the space between contiguous sets of teeth and cannot produce progressive failure of the entire unit.

In the construction of a brush in accordance with the provisions of this invention, other forms of locking core and/ or other forms of channel backing element may be used. The use of one such locking core is illustrated in FIGURE 6, wherein the channel backing element 79 may be substantially the same as the channel backing 30 already described. it initially is formed with outwardly flaring sides having longitudinal ribs 81 which may be con tinuous or interrupted at intervals, as may be desired.

The locking core in this construction is formed of a strip or metallic tape, illustrated in :FIGURE 7, and having tabs, as at 82, which are bent outwardly to provide integral teeth 82a. The teethare disposed in two parallel rows separated by an intermediate or land portion 83 and being spaced from the edges of the strip by portions 84. To form a core suitable for locking fill material in the channel 79, the teeth 82a are struck laterally outwardly and the strip is bent intermediate of the teeth to U-shape, as indicated in FIGURE 6. The portions 84 may be inward-1y bent, as indicated at 86, and the marginal portions may be brought into contact with each other. These marginal portions may be left free, or they may be secured together as by spot welding or other form of welding, as indicated at 87. Welding or other mode of securing the strip ends together is optionah This construction, it will be appreciated, is very rigid and strong. As illustrated in FIGURE 6, the tooth portions 820 are engaged under the ribs 8 1 in such manner as positively to hold the locking core against displacement from the channel. When the strip is wound upon a core, the teeth are disposed in radial planes so that there is but little displacement of the fill material. This arrangement also gives great strength to the teeth be- It may be driven at high speed 6 cause their vertical width is usually much greater than their thickness.

It will be appreciated that when a number of turns of the brush strip of the sections shown herein, e. g., in FIG- URES 6, 15 or in other figures to be described, are

wound upon a mandrel or core M in the manner illustrated in FIGURE 10, the side walls of the channel backing element mutually support each other so that it is virtually impossible for the side walls of the channel to spring outwardly with respect to the tips of the teeth, thus releasing the latter. To enhance the supporting effect, the ends of the spirally wound strip may be engaged by check plates having nuts 71a threaded upon the shaft 71.

In FIGURES 8 and 9, still another embodiment of locking core is illustrated. in this construction, a tape, such as the tape 89 shown in FIGURE 9, is employed and this is provided with cuts forming tabs 90 at the edges thereof. These tabs are bent to provide teeth 91, shown in FIGURE 8, and are disposed atthe upper edges of the U-shaped core element 92 which holds the fill material 92a in the channel. The teeth are engaged under the lower edges of continuous or discontinuous ribs 93 corresponding to the ribs 2.9 and 81 already described. In

the finished brush, these teeth are also disposed in radial planes and interfere but little with the fill material. FTheir radial width is relatively great, therefore, they offer great resistance to centrifugal force.

In the embodiment of the invention illustrated in FIG- URE 16, the ribs, such as ribs29 and 81, in the side walls are eliminated, appropriate abutments within the channel backing element being provided for retaining the ends of the teeth of the locking core by folding inwardly the edge portions of the side walls of the channel backing element.

In the finished construction, the channel backing element 95 is shown as having

side walls

96 and 97 interconnected at their lower edge-s by web 98, which may be flat (as shown), rounded, or otherwise configured. The side walls may be disposed substantially in vertical position or as shown, slightly inwardly inclined, thus increasing the pressure upon the doubled or hairpin-like fill material 99. The fill material is held in place as by a locking core 101 which is much like that illustrated in FIGURES 5, 14 and 15, except that the teeth elements 102 thereof are somewhat longer than those of the previously described embodiment and as shown, at their tips, are upwardly bent as indicated at 10 3 and are gripped by portions 104 of the edges of the

side walls

96 and 97,

which portions are folded downwardly over said tip portions to grip the same and thus to tie the side walls of the channel backing element together at their upper edges.

The essential steps involved in forming the construction shown in FIGURE 16 are illustrated in FIGURES 17, 18 and 19, wherein for purposes of forming the channel backing element, a suitable metallic tape or ribbon similar to that shown in FIGURE 11, except for the elimination of ribs 29, is provided. The tape is bent to semi-formed channel shape, as indicated at 105 in FIGURE 17, this form being attained by passing a flat tape or strip through a shoe element, indicated diagrammatically at 106. The latter has an opening formed therethrough, which at the emergent end for the tape, corresponds in section to the shape desired in the semi-formed channel. Obviously, the opening may be graduated in section from the substantially fiat section of the original tape to the ultimate section desired in the semi-formed channel backing element.

The single shoe element, if desired, may be replaced by a series of such elements so placed as to contact successively the tape as it is drawn, and being designed progressively to bring the flat tape or ribbon from its initial shape to the ultimate semi-formed section illustrated in FIGURE 17. If desired, the shoe (or shoes) illustrated in FIGURE 17 may also be replaced by forming rolls designed to impart desired section to the fiat tape or ribbon in well-known manner. As shown in FIGURE 17, the marginal portions 104 are only partially folded over, sufficient space being left between the folded portions and the contiguous portions of the side walls to admit of the insertion of the ends of the teeth 102.

The essential steps of forming a brush strip using the semi-formed channel backing element 105 shaped by the shoe 106, are illustrated in FIGURES 18 and 19. In FIGURE 18, the semi-formed channel backing element is indicated as being conveyed by suitable cooperating rollers, one (107) of which is disposed on shaft 107a to engage the bottom portion 98 of the channel backing element. The

side walls

96 and 97 of the latter are engaged by

rollers

108 and 109, which are respectively supported on

shafts

111 and 112, which at their extremities are secured in appropriate supports, such as arms 113. In the operation of forming the strip, double-length fill material, indicated at 116, is disposed across the upper edges of the partially formed channel backing element. A locking core 101 is disposed thereupon with the teeth elements 102 thereof disposed in outwardly and upwardly inclined position in contiguity to the inwardly folded edge portion 104 of the semi-formed channel backing element. The channel backing element is downwardly pressed by narrow roller 117 on shaft 118 and running in the channel of locking core 101, thus forcing the mid-portions of the fill material into the semi-formed channel backing element. The roller v117, it will be apparent, in addition to forcing the locking core 101 down upon the fill material, also functions to hold the semi-formed channel backing element firmly in place upon the

rollers

107, 108 and 109.

In order to impart the desired final form to the channel backing element, the latter, after the fill material and the locking core have been disposed in place, may be passed between an additional set or a series of sets of rollers, which bring the side walls of the channel backing element to their final position. This change of position of the side walls may be obtained gradually by a series of sets of rollers which operate progressively to press the upper edges of the side walls toward each other, or it may be accomplished by means of a single set of rollers in a single stage. In any event, the positions of the several rollers for the final pressing operation are indicated in FIGURE 19, wherein a roller 119 upon a driven shaft 121 is shown as engaging the mid-portion or bottom portion 98 of the channel backing element, while the side walls are inwardly pressed by rollers 122 and 123, which may be similar or identical to the

rollers

108 and 109, except that the axes thereof are upwardly and inwardly inclined in order to press the sidewalls toward each other. Preferably, in the final operation of forming the channel backing element, the side walls are pressed with considerable force against the sides of the fill material, thus completing the doubling of the latter to hairpin shape and also clinching the folded marginal portions 104 of the channel backing element 105 down upon the tips 103 of the teeth 102.

In the pressing operation, as the upper edges of the side walls of the channel backing element approach each other, the outer tips of the teeth 102 are upwardly bent by contact with the

side walls

96 and 97 to their final position, as indicated at 103, being bent; toward the inner faces of the side walls. The teeth and the core portion 101, it will be apparent, function in the finished strip to hold the side walls against any outward pressures exerted by the compressed fill material within the channel backing element. The tips of the teeth are positively locked in place, thus preventing bending of the teeth by centrifugal force exerted against the locking core.

A section of a slightly modified form of a brush strip wherein the channel backing is also provided with folded margins, is illustrated in HGURE 20. The construction embodies a channel backing element having a web portion 131 and side walls 132 with downwardly folded edge portions 133. The locking core 134 is substantially the same as that illustrated in FIGURE 16, except that the teeth elements 136 thereof are some what shorter and instead of being locked or gripped between the folded portions 133 and the side walls 132, are disposed with their tips below the lower edges of the downwardly folded portions 133. The latter portions provide abutments having substantially the same effect as the ribs 29 in previously described embodiments of the invention. The fill material 137 in this construction is of double length or harpin type corresponding to that described in the previous embodiments of the invention.

In the form of the invention as illustrated in FIGURE 21, a channel backing element 138 is provided, having a pair of side walls 139 interconnected by a web 141. The side walls are also provided with ribs 142 which, as shown in this instance, are inwardly concave to receive the tips of the teeth 144 of a locking core 146 which, as illustrated, is of the same form as that disclosed in FIGURE 5. The hairpin-like fill material 147 is held within the channel by the core. The teeth 144 engaging the concavities of the ribs 142 prevent the dislodgment of the core under the centrifugal forces exerted thereagainst. If desired, the ribs 142 may be interrupted at intervals to provide passages between the turns of a spirally wound brush formed of the channel strip having the form shown in this figure. The passages between the sides of the turns promote circulation of air to convey away heat which may tend to build up within the strip.

It will be appreciated that the locking core need not necessarily be formed by the bending of a strip or tape in the manner illustrated in FIGURE 5. The core may, for example, be formed by rolling or extruding a rod of approximately dumbbell section, as illustrated in FIGURES 22 and 23. In this form of the invention, the dumbbell section comprises beads 150 along one or both edges, these beads being interconnected by an integral web portion 151 which is punched at intervals to provide integral teeth 152. These teeth may be bent alternately to opposite sides of the web, leaving portions 153 of web between contiguous teeth constituting a pair, thus supporting the bead portions 150 in spaced relationship with respect to each other. The teeth 152, it will be appreciated, are adapted to engage under ribs 29 or the edge portions 104 of the channel backing element, as already described, thus securely holding the locking core in place against centrifugal force developed against the inner perimeter of said locking core.

I claim:

1. A brush strip comprising a channel backing element having imperforate side walls and a web portion interconnecting the side walls, said side walls having substantially continuous, longitudinal abutment portions formed therein, hairpin shaped fill material having the bight portions thereof disposed within the channel backing element, a locking core disposed within the bight portions and having longitudinally spaced, laterally projecting teeth engaging the abutment portions of the side walls to hold the locking core in place within the channel backing element.

2. A brush strip comprising a channel backing element having imperforate side walls and a web portion interconnecting the side walls, said side walls having substantially continuous, longitudinally extending ribs formed therein, hairpin shaped fill material having the bight portions thereof disposed between the side walls, a locking core disposed within the bight portions of the fill material and having laterally extending teeth engaging the ribs whereby to hold the locking core within the channel backing element.

3. A brush strip comprising a channel backing element having imperrorate side walls and a web portion interconnecting the side walls, said side walls having substantially continuous, inwardly concave, longitudinally extending ribs formed therein, hairpin shaped fill material having the bight portions thereof disposed between the side walls, a locking core disposed within the bight portions of the fill material and having laterally extending teeth engaging under the ribs whereby to hold the locking core within the channel backing element.

4. A brush strip comprising a channel backing element having imperforate side walls and a Web portion interconnecting the side Walls, said side walls having substantially continuous, longitudinal abutment portions, hairpin shaped fill material having the bight portions thereof disposed within the channel backing element, a locking core disposed within the bight portions and comprising a strip of longitudinally folded metal having laterally projecting teeth engaging the abutment portions of the side walls to hold the locking core in place within the channel backing element.

5. A brush strip comprising a channel backing element having imperforate side walls and a web portion interconnecting the side walls, said side walls having substantially continuous, longitudinal abutment portions, hairpin shaped fill material disposed with the bight portions thereof within the channel backing element, a locking core disposed within the bight portions and comprising a longitudinally folded metallic strip having teeth formed alons the edges thereof, the teeth being laterally projecting and the ends thereof engaging the abutment portions of the side walls to hold the locking core in place within the channel backing element.

6. A rotary, power-driven brush comprising a brush strip having a channel backing element spirally wound upon a mandrel, said channel backing element comprising imperforate side walls and a web portion interconnecting the side walls, said side walls having longitudinally extending continuous inwardly projecting channel shaped rib portions disposed within the channel backing element, hairpin shaped fill material having the bight portions thereof disposed within the channel backing element, a longitudinally extending locking core disposed within the bight portions, said locking core having laterally projecting teeth engaging the abutment portions to secure the core within the channel backing element against centrifugal forces developed when the brush is rotated.

7. A brush strip comprising a channel backing element having imperforate side walls and a web portion interconnecting the side walls, said side walls having the upper edges thereof folded inwardly substantially along their entire lengths to a position substantially parallel to the lower portion of said side walls, thereby forming inverted Us with the contiguous unfolded portions of said side walls, hairpin-shaped fill material having the bight portions thereof disposed within the channel backing element, a locking core disposed within the bight portions and having longitudinally spaced, transversely projecting teeth enclosed between the folded portions of the side walls and the contiguous unfolded portions of said side walls, thereby holding the locking core in place within the channel backing element.

8. A brush strip comprising a channel backing element having imperforate side walls and a web portion interconnecting the side walls, said side walls having the upper edges thereof folded inwardly substantially along their entire lengths to a position substantially parallel to the lower portion. of said side walls, thereby forming inverted Us with the contiguous unfolded portions of said side walls, hairpin-shaped fill material having the bight portions thereof disposed within the channel backing element, a locking core disposed within the bight portions and having longitudinally spaced, transversely projecting teeth engaging the folded upper edge of the side walls to hold the locking core in place within the channel backing element.

References (Iited in the file of this patent UNITED STATES PATENTS Great Britain Nov. 17, 1932