US2609242A - Brush element and method of manufacture - Google Patents

Description

Sept. 2, 19 B. E. NELSON BRUSH ELEMENT AND METHOD OF MANUFACTURE Filed. July 15, 1948 uI l/////,/////// INVENTOR. zmao/zs EJVELJON BY 060 06M. ATTOIZIVEYJ.

Patented Sept. 2, 1952 ATENT OFFICE I BRUSH ELEMENT AND METHOD OF MANUFACTURE Brooks E. Nelson, Cleveland, Ohio, assignor to The Osborn Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application July 13, 1948, Serial No. 38,373

This invention relates, asindicated, to brush manufacture and more particularly to a novel brush element adapted to be circularized or similarly deformed about a very small radius.

It has long been recognized that a desirable manner of producing brush elements continuously is to manufacture the same inthe form of a relatively flat layer of brush material retained in an elongated channelform brush back and various constructions of such brush strip have been suggested, as, for example, in Cave Patent No. 1,834,911.

The form of strip disclosed in Peterson Patent No. 2,803,386 has proven to be particularly efficient and useful, especially when circularized to produce annular rotary brush sections and the like. The teeth which are punched in from the sides of the channelform back not only serve to secure the elongated brush material retaining member in place but-also prevent any appreciable shedding of such material from the severed end of a length of brush strip. The shape of the teeth is such that concentrations of stresses are minimized during circularization, as by winding upon a mandrel, andtearing of the edges of the channelform back is avoided.

When, however, annular rotary brush sections, for example, have been desired having an internal diameter on'the order of one or two inches, even such improved form of strip tends to tear at the outer edges of the sides of such channelform back and the insect such back becomes overly compressed and will buckle. It has therefore been the general practice to form suoh small rotary brushes individually, using stampings which may be welded or riveted together to clamp the radially extending brush material therebetween. This is, of course, a relatively slow and expen-' sive process and is not adapted to the production of helically wound brush elements at all. In fact, it has not previously been commercially practicable to manufacture helically wound rotary brush elements of small diameter although for many uses a roller brush thus formed offers advantages overa comparable brush formed by assembling a plurality of annular sections in sideby-side relationship.

When using wire brush material in a brush back of the type disclosed in Peterson Patent No. 2,303,386, there is some tendency forsuch material to cut and tear the highly stressed edges stresses at such edges.

When brush strip is circularized, there is a 29 Claims. (Cl. 300-21) 2 resultant lessening of bristle density at the brush face so it is important that a maximum of brush material be retained in a given channelform back. When teeth are punched in from the sides of such back at a point removed from the edges or lips thereof, the space between the wire retaining member held under such teeth and the bottom of the channel is reduced with a consequent reduction in the quantity of brush material which may be secured beneath such wire. This is a rather serious disadvantage in the production of the smaller sizes of brush strip and has necessitated the employment of disproportionately large backs. Yet teeth punched in from the channel edges cause severe tearing whenever circularization' about a small diameter is attempted.

It is therefore a primary object of this invention to provide a new method of continuously forming an elongated brush element in which the brush material will be securely retained without the disadvantages involved in the prior methods known to the art.

Another object of this invention is to provide a novel construction of brush strip in which the brush material is securely retained and which is adapted to be circularized about-a relatively small radius or similarly angularly bent about a small radius without consequential injury to the brush back.

Still another object is to provide an elongated brush element of the type indicated having a maximum quantity of brush material retained in the brush back so that upon circularization the brush face of the resultant rotary brush may be of the desired density. I p 7 A further object is to provide a rotary brush which will combine the features of increased strength with increased density of the brush material at the brush face.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and par ticularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. 1 is a fragmentary perspective view of the novel brush back. element prior to its being shaped into channel form;

Fig. 2 is a somewhat diagrammatic perspective view illustrating the general method of construction of the brush element of this invention;

Fig. 3 is a perspective view of the finished brush strip produced in accordance with the process of Fig. 2;

Fig. 4 is a perspective view similar to Fig. 3 but with the brush material and wire retaining member removed to disclose the disposition of the teeth within the channel;

Fig. 5 is a view in cross-section of the brush element of Fig. 3;

Fig. 6 is a view similar to Fig. 5 but showing a slightly modified form of brush back construction;

Fig. 7 is a view similar to Figs. 5 and 6 but illustrating a corresponding prior art form of brush back construction for purposes of comparison;

Fig. 8 is a view in cross-section showing a construction in which two opposed tooth-carrying members are employed within the outer channel back; K

Fig. 9 is an elevational view of an annular rotary brush section formed of a single turn of the brush strip of Fig. 3; and

Fig. 10 is an elevational perspective view of a helically wound or roller brush formed by circularizing the brush strip of this invention.

Referring now more particularly to Figs. 1-5 inclusive, one form of brush back in accordance with this invention comprises an inner strip I secured to an outer strip 2 as by spot welding 3. These two strips will ordinarily be of metal such as steel and will ordinarily be of substantially the same width as shown in Fig. 1. As explained below, it may occasionally be preferred that outer or backing strip 2 be of somewhat greater width than inner strip I.

Prior to securing the two strips together, teeth 4 are turned up by punching from the opposite edges of strip I. Such teeth will preferably have a portion of their inner edges 5 adjacent the base of such teeth parallel to the edges of strip I as this has been found to minimize tearing upon circulation, as taught in Peterson Patent No. 2,303,386. r

As shown diagrammatically in Fig. 2, stranded brush material 6 will be laid across strip I and a wire'retaining member I laid thereon centrally of the strip. Strips I and 2 will then be formed into a channel 8 by passage between suitable dies, teeth 4 being turned inwardly with their opposed ends overlapping to secure brush material retaining member I thereunder. Such teeth on opposite sides of strip I may desirably be formed only slightly offset from each other longitudinally of the strip so that they will engage retaining member I in pairs (see Fig. 4).

As shown in Fig. 5, a brush strip is thus produced having a channelform back within which a maximum quantity of brush material is securely held since teeth 4 are as near as possible to the upper edge or lip 9 of the channelform brush back, thereby leaving maximum space between retaining member I and the bottom of the channelform back. This advantage may readily be appreciated by comparison with Fig. 7 showing an analogous prior art construction in which the teeth II] are punched in from the side of the channeelform back II at a point spaced from the lip or edge I2 thereof. Obviously, for a given size brush back considerably less brush material may be retained beneath elongated retaining member I and consequently when the strip is circularized to form a rotary brush member the density of the brush material at the brush face may not be as much as desired. As above indicated, the reason for thus punching such teeth In at a point spaced from the lip of the channel was that otherwise serious tearing of the channel lip frequently occurred upon circularization of the strip.

By employing two relatively thin strips secured together in the formation of the brush back, it has been found that the teeth 4 may be placed in the most advantageous position adjacent the respective lips of the channelform back without incurring the disadvantages previously resulting from such an arrangement. Reinforcement by outer strip 2 serves to minimize damage to the inner strip I despite the notches I3 in the edges of the latter. Brush strip formed in this manner has been circularized about mandrels of a very small diameter with complete success, and even when employing crimped wire brush material it has been possible to circularize the strip about a mandrel'of 1 inches diameter and less. No tearing or other damage to the channelform back was incurred.

Referring now to Fig. 6 of the drawing, a slightly modified'form of channel construction is there illustrated in which outer strip 2 is of appreciably greater width than inner strip I and the edge portions I4 of the former have been bent or flanged inwardly to overlie the edge of strip I. This serves to further reinforce such inner strip and to firmly secure the same so that it is not always necessary that strips I and 2 be tacked togethed by spot welding or otherwise as above described. Turned in portions I4 may, if desired, extend sufficiently to produce a somewhat more constricted neck to the brush back, thereby reducing the degree of outward flare of the brush material. This arrangement may frequently be desired, since the positioning of retaining member I relatively close to the neck of the channelform back is conducive to a larger degree of flaring than would occur when such retaining member is nearer to the base of the channel.

Depending upon the material employed and the uses to which the brush element is to be put, strips I and 2 may be adhered together by means of'suitable adhesives or plastic cements rather than by spot welding.

The finished brush strip may be out into desired lengths for use in various types of brushes or may be circularized in well-known manner to produce a helical or roller brush as shown in Fig. 10. A single turn of such strip may be formed into an annular rotary brush section by bringing the opposed ends together, as shown at I5 in Fig. 9, and mounting between suitable adapters or clamping plates.

It will be seen from the foregoing that a novel brush element has been produced in the form of a brush strip having a channelform back, from the sides of which teeth are turned inwardly to secure the brush material retaining member in place without, however, destroying the usefulness of such element for many purposes requiring bending or circularization of the strip. It is now possible to produce a rotary brush member in'which the brush material extends substantially radially, such brush having a brush face of larger outer diameter, but a brush back circularized to fit a smaller mandrel, while still maintaining the desired density of brush material at such brush face. Small annular rotary brush sections and the like can now be continuously produced from strip material, which is much less expensive than the prior method of assembling the same from individual stampings. Furthermore, by helically winding such strip, a roller brush may be produced which will not cause streaking of the work such as is commonly encountered when such brushes are formed by assembling a plurality of individual annular sections in sideby-side relationship.

As shown in the drawing, the sides of the channelform back will generally slope inwardly slightly to form a somewhat narrower neck, although such sides may be substantially normal to the base of the channel if desired. While the back will normally be of metal such as steel, other materials such as copper and certain of the synthetic plastics may be employed. In such cases brazing and an appropriate solvent may be utilized to adhere the respective types of materials together. Any of the usual brush materials may be used for the fill, including tampico fiber, horsehair, cord, synthetic plastic strands such as nylon, and crimped wire.

While it is contemplated that the teeth will be punched from the respective edges of the inner strip in order to provide for maximum fill, they may if desired be punched in at points spaced from such edges as taught in Peterson Patent No. 2,303,386, the outer strip closely embracing and reinforcing the same to permit successful circularization about a smaller radius.

In any case, the sides of the outer or reinforcing back should extend at least to the base of the openings punched in the toothed member, and will preferably extend to the edge or lip of such inner toothed member. As above explained in connection with the Fig. 6 embodiment, theouter channel sides may be extended beyond the edges of the inner member and bent inwardly to help secure such member in place and, optionally, to form a pressure neck laterally constricting the brush material.

Referring now more particularly to Fig. 8 of the drawing, two elongated strips I6 and 'l'! are shown secured to the inner side of channel 2 by spot-welding l8, and provided with opposed teeth 19 to hold brush material retaining member l in place thereunder. The spot-welding will be close to the base of channel 2 so as not to interfere appreciably with uniform stretching of L the channel edge when the brush strip is circularized. By this construction a certain amount of material is saved and additional space is provided within the back beneath retaining member I so that a still greater quantity of brush material may be held thereunder. Circularization is also somewhat facilitated by the fact that the base of the brush back is of only single thickness. Supplemental to, or replacing, the spotwelding, the edges of channel 2 may extend beyond the edges of strips l6 and I! and be turned in to help hold such strips in place.

When brush strip of this nature is to be circularized with the brush material extending generally in the same direction (to form a cup brush, for example) rather than radially to form a wheel-type brush, one of the strips It or Il may be omitted and the brush back bent with the teeth on the inside of the bend. The outer channel wall will be drawn inwardly toward the ends or" such teeth to help hold member 1 in place. Reference may be had to co-pending applica-'- tion Serial No. 38,374 of Brooks E. Nelson and Ruben 0. Peterson Brushes filed July 13, 1948 for further details concerning this latter type or construction. It should be appreciated that brush strip constructed in accordance with this invention has greatly increased resistance to tearing when circularized or otherwise bent, whether with the brushmaterial extending axially (parallel) orradially.

I have, therefore, provided a novel brush element having a channel back, the exterior surface of which is unbroken but which nevertheless has teeth therein to hold the Wire retainin member thereunder. Concentration of stresses is thus avoided in such back upon circularization, and tearing is prevented.

Instead of providing the toothed member as a continuous strip, a plurality of individual toothed members may be employed similarly spot-welded or otherwise secured within the back. In one form such toothed members may comprise sections of a strip such as toothed strip l, with two or more teeth per section.

When employing the Fig. 6 construction, or constructions wherein the sides of the outer channel back incline inwardly at the neck, for example, it is not always necessary to spot-weld or otherwise adhere the toothed member to the outer channel since the latter will mechanically hold the former in place.

Other modes of applying the pirnciple of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of continu ously turning up teeth from both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of substantially the same width by spot-welding, advancin the resultant composite backing strip longitudinally, depositing a layer of stranded brush material transversely of the face of such strip from which such teeth project, placing a wire retaining member on such material between the two rows of teeth lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such wire secured beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

2. In the manufacture of brush strip having a relatively fiat layer of brush material extending from a channelform back, the steps of turning up teeth from both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of at least equal width by spot-welding, depositing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member socured beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

3. In the manufacture of brush strip having a relatively fiat layer of brush material extending from a channelform back, the steps of turning up teeth from both edges of a strip of self-sustaining material, securing the non-tooth bearing side of such strip to another reinforcing strip of at least equal width, placinga layerof brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the'two rows of teeth lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member secured beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

4. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from an edge of a metal strip, securing the nontooth bearing side of such strip to another metal strip of at least equal width by spot-welding, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

5. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from an edge of a strip of self-sustaining material, securing the non-tooth bearing side of such strip to another reinforcing strip of at least equal width, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

6. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of at least equal Width by spot-welding, depositing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member secured beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

7. In the manufacture of brush strip having a relatively fiat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent both edges of a strip of self-sustaining material, securing the non-tooth bearings side of such strip to another reinforcing strip of at least equad width, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, and forming such composite backing strip, into generally U-shape cross-section with such retaining member secured beneath such teeth to hold such 8 brush material firmly seated in the resultant channelform back.

8. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent an edge of a strip of self-sustaining material, securing the non-tooth bearing side of such strip to another reinforcing strip of at least equal Width, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

9. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of somewhat greater width by spot-welding, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, forming such composite backing strip into generally U-shape cross-section with such retaining member secured beneath such teeth to hold such brush material firmly seated in the resultant channelform back, and turning in the edges of such outer strip to overlie the respective edges of such toothed strip.

10. In the manufacture of brush strip having a relatively flat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent an edge of a strip of self-sustaining material, backing such strip with a reinforcing strip of somewhat greater width, turning in the edge portions of such reinforcing strip to engage the respective edges of such toothed strip, placing a layer of brush material transversely of the face of such strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such strip, and forming such composite strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back and the edge portions of such reinforcing strip closely overlying the edges of such toothed strip.

11. In the manufacture of a rotary brush element having a relatively fiat layer of brush material extending from a channelform back, the steps of turning up teeth from both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of at least equal width by spot-welding, depositing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, forming such composite backing strip into generally U-shape cross-section with such retaining member secured beneath such teeth to hold such brush material firmly seated in the resultant channelform back, and circularizing the brush strip thus formed.

12. In the manufacture of a brush element having a layer of brush material extending from a 'channelform back, the steps of turning up teeth from both edgesofv a strip of self-sustaining material, securing the nontooth bearing side of such strip to another reinforcing strip of at least equal width, placing a layer. of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, forming such composite backing strip into generally lJ-shaped cross-section with such retaining member secured beneath such teeth to hold such brush material firmly seated in the. resultant channelicrm back, and circularizing the brush strip thus formed.

13. In the manufacture of a brush element having a layer of brush materialextending from a channelform back, the steps of turning up teeth from adjacent both edges of a metal strip, securing the non-tooth bearing side of such strip to another metal strip of at least equal width by spot-welding, depositing a layer of brush material transversely of the face of the resultant come posite backing strip from which such teeth project, placing an elongated retaining member on such material between the two rows of teeth lengthwise of such backing strip, forming such composite backing strip into generally U-shape cross-section with such'retaining member secured beneath such teeth to hold such brush material firmly seated in'the resultant channelform back, and circularizing the brush strip thus formed. 14. in the manufacture of a brush element having a layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent an edge of a strip of self -sustaining material, securing the non-tooth bearing side of such strip to another reinforcing strip of at least equal width, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such backing strip, forming such composite backing strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back and bending the brush strip thus formed to desired shape.

15. As a new article of manufacture, a brush strip comprising an inner metal channelform back having teeth turned inwardly from the edges thereof, a wire retaining member disposed lengthwise within such channel and held in place beneath such teeth, brush material secured in such channel by said retaining member, and an outer metal channelform back secured to said inner back by spot-welding and closely embracing said inner back, the sides of said outer back being substantially coextensive with the sides of said inner back.

16. As a new article of manufacture, a brush strip comprising an inner channelform back having teeth turned inwardly from the edges thereof, an elongated retaining member disposed lengthwise within such channel and. held in place beneath such teeth, brush material secured in such channel by said retaining member, and an outer channelform back secured to said inner back and closely embracing the same, the sides of said outer back extending at least to the respective edges of said inner back.

17. As a new article of manufacture, a brush element comprising an inner channelform back hayilrls teeth turned inwardly froman edge thereof, an elongated retaining member disposed lengthwise within such channel and held in place beneath such teeth, brushmaterial secured in such channel by said retaining. member, and an outer channelform'back secured to said inner back and closely embracing the same, the sides of said outer back extending at least to the respective edges of, said inner back. 2

l8. a new article of manufacture, brush strip comprising. an inner channel-form back having teeth turned inwardly from adjacent the edges thereof, an elongated retaining member disposed lengthwise within such channel and held in place beneath such teeth, brush material secured in such channel by said retaining member, and an outer channelform .back secured to said inner back and closely embracing the same/the sides of said outer back extending at least to the respective edges of said inner back.

19. As a new article of manufacture, a brush element comprising an inner channelform back havingteeth turned inwardly from adjacent an edge thereof, an elon ated retaining member disposedlengthwise within such channel and held in place beneath such teeth, brush material secured in such channel by said retaining member, and a unitary outer channelform back secured to said inner back and-closely embracing the same, the sides .of said outer back extending at least to the respective edges of said inner back.

2 0. A 8 newsarticleof manufacture, a flexible brush strip comprising a unitary channelform a k. a member secured within such channel and closely engaging a side thereof for reinforcement thereby, said member havingteeth extending transversel of such channel, :such teeth being formed by punchin and leaving corresponding openings in such -member,.an elongated retaining member disposed lengthwise within such channel and held in place beneath such teeth, and brush material secured in such channel by said retaining member.

21. As a new article of manufacture, a brush element comprising a unitary channelform back,

a member secured within such channel and closely engaging a side thereof for reinforcement thereby, said member having teeth extending transversely of such channel, such teeth being formed by punching, and leaving corresponding openings in such member, an elongated retaining member disposed lengthwise Within such channel and held in place beneath such teeth, and brush material secured in such channel by said retaining member, such assembled brush back being bent into non-rectilinear form.

22. As a new article of manufacture, a brush element comprising an inner channelform back having teeth turned inwardly from the edges thereof, an elongated retaining member disposed lengthwise within such channel and held in place beneath such teeth, brush material secured in such channel by said retaining member, and an outer channelform back closely embracing said inner back with its edges turned in to overlie and secure the corresponding edges of said inner back, such assembled brush back being circularized.

23. As a new article of manufacture, a brush strip comprising an outer unitary channelform back, a member disposed lengthwise within said a back and having teeth projecting transversely of such channel. an elongated retaining member disposed lengthwise within such, channel and held in place beneath such teeth and brush ii material secured in such channel by said retaining member, an edge of said outer channel- .form backbeing turned in to overlie and secure posed lengthwise within such channel and held in' place. beneath such teeth, and brush material secured in such channel by said retaining member.

25. In the manufacture of brush strip having a .relatively fiat layer of brush material extending from a channelform back, the steps of turning up teeth from adjacent an edge of a strip of self-sustainin .material, securing such strip to another reinforcing strip of a'width extending at least to the bases of such respective teeth, placing a layer of brush material transversely of the face of the resultant composite backing strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such backing strip, and forming such composite backing strip into generally U-shape cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back. 26. As a new article of manufacture, a brush strip comprising an inner channelform back having teeth turned inwardly from adjacent an edge thereof, an elongated retainin member'disposed lengthwise within such channel and held in place beneath such teeth, brushmaterial secured in such channel by said retaining member, and an outer unitary channelform back secured to said inner back and closely embracing the same, the sides of said outer back extending at least to the bases of such teeth.

i2 27. As a new article of manufacture, a flexible brush strip comprising a unitary channelform back, a tooth bearing member held within said back havin teeth disposed transversely thereof,

an elongated retaining member disposed lengthwise within such channel and held in place beneath such teeth of said tooth bearing member, and brush material secured in said channelform back by said retaining member.

28. As a new article of manufacture, a flexible brush strip comprising a unitary channelform back having sides with an unbroken external surface, an elongated retaining member disposed lengthwise within such channel, teeth projecting inwardly from the sides of such channel holding said retaining member therebeneath, and brush material secured-in-said channelform back by said retaining member.

29. In the manufacture of a brush element having a relatively fiat layer of brush material extending from a channelform back, the steps of placing a tooth bearing member on a strip of self-sustaining backing material, placing a layer of brush material transversely of such strip on the face of such strip from which such teeth project, placing an elongated retaining member on such material lengthwise of such strip, and forming such strip into generally U-shaped cross-section with such retaining member beneath such teeth to hold such brush material firmly seated in the resultant channelform back.

BROOKS E. NELSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,829,665 Mertes Oct. 27, 1931 2,303,386 Peterson Dec. 1, 1942

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