MXPA00001488A - A method of endrounding loose fibres - Google Patents

Abstract

For implant molding of toothbrushes pre-cut and pre-rounded fiber of thermoplastic material are used. Loose fibres are presented to an endrounding tool in a tuft or bundle and the free ends of the fibres are exposed to a working surface of the tool. Relative movement between the fibre ends and working surface causes the material of the fibres to be heated by friction of a predetermined intensity. The fibres while they are exposed to the working surface of the tool are permitted to flex laterally and are held in an axial direction of the tuft or bundle with their free ends commonly defining a surface different from a plane which is perpendicular to the axial direction, thereby achieving a substantially consistent flexing resistance throughout the cross section of the tuft or bundle with respect to lateral deflection upon engagement by the endrounding tool.

Description

A METHOD FOR ROUNDING OF EXTREME LOOSE FIBERS Pescrjpcj.fn The present invention relates to a method for rounding end loose fibers of thermoplastic material for use in the manufacture of brushes, and in particular in the manufacture of toothbrushes.

Brushes for dental or cosmetic use should have bristles with rounded free ends to avoid injury or damage to the user. The rounding of the bristle ends is done since the bristles have been attached to a brush body by means of abrasive methods or radiation.

According to a more recent technology, the bristles are implanted with molding in the body of the brush. This technology allows the use of pre-cut and pre-rounded fibers, avoiding a finishing step after the bristles have been attached to the body of the brush. It is more convenient to process the fiber for the purpose of rounded end before fastening to the brush body than to carry out the finishing steps with the bristles already attached to the brush body.

When a method of rounded abrasive end is used, it is mandatory to have the free ends of the fibr perfectly aligned in a plane perpendicular to the length of the bundle or strand presented to the work surface of the end rounding tool. This requirement has been recognized and confirmed in the patent literature, for example, in European patent 0 346 646 Bl. Unless this requirement is satisfied, the fiber ends are not consistently rounded and smoothed on all sides. Also, the amount of fiber that must be processed in a single country is limited because the fiber ends must be free to be deflected laterally so that the fiber end surface can be presented to the work surface and hooked thereto by the end rounding tool from all sides and directions.

Recently, a new end-rounding technology has been proposed where a consistent and perfect rounding quality is achieved by producing a friction rather than abrasion between the working surface of the end rounding tool and the free ends of the tool. the fibers. As described in utility model patent 296 14 118 the rounding effect achieved with this technology is not fully understood, but the relative speed between the end fibers and the work surface is an essential parameter. The relative velocity d produce friction in an amount sufficient to heat the thermoplastic material of the fiber near its melted point, but excessive heat will destroy the fiber ends. This technology has been used successfully on the bundles of bristles attached to the bodies of the toothbrush so that the bristles (or the fibers are exposed to the working surface of the extremity rounding tool in relatively small bundles. large quantities of bristles or fibers in a bundle due to the expected concentration of friction and heat in the central part of the plane, in which the free ends of the fibers are exposed, such friction concentration, and po so much the heat in the The central part of the bunch is due to the increased lateral support of the fibers in the central part against the deflection by means of the hook with the end rounding tool.The fiber in the central part of the bundle is more rigid because it is sustained laterally by the rounding fiber, therefore, a uniform distribution of heat through the cross-section of the bundle may not be As mentioned above, however, the new rounded end technology requires consistent heating conditions within closed limits. A similar rounding technique is described in U.S. Patent No. 2,554,777 wherein the fibers are processed while they are mounted on a brush.

The present invention provides a method for rounding off the loose fibers of thermoplastic material for use in the manufacture of brushes where the new rounded end technology based on friction, rather than abrasion can be used and can be processed. relatively large amounts of fiber in a single time. Therefore, according to the invention, the fibers are presented to an end rounding tool in a bunch of a relatively large diameter, and the free ends of the fibers are exposed to the working surface of the tool to produce the relative movement. between the fiber ends and the work surface, causing the material of the fibers to be heated by friction of a predetermined intensity. Even when the fibers are exposed the working surface of the tool, it is allowed to flex laterally and are maintained in an axia direction of the bundle or tuft with its free ends commonly defining a different surface of a plane which is perpendicular to the direction axial. Since the fibers have their ends lying in a different plane in a plane to which and perpendicular to the axial direction of the bundle or strand, the flexural strength of each individual fiber can be adjusted in a manner to achieve a consistent friction heating through of the cross section of the tuft bunch. Specifically, in the preferred embodiment, the fibers have a cantilever length, which is greatly close to the center of the bundle or strand that is closest to the periphery. From a geometric point of view, the fibers have their free ends located on a convex surface. The convex shape can be conical, frusto-cranial hemispherical.

The features and additional details of the invention will be apparent from the following description of the various embodiments with reference to the drawings. In the drawings: Figures 1, 2 and 3 show three possible configurations of a bundle of fibers to be presented to an end rounding tool.

Figure 4 is an enlarged partial view of the configuration of Figure 1; Figure 5 is an enlarged partial view of the configuration of Figure 3; Figures 6, 7 and 8 are schematic illustrations of three additions of the new end rounded method.

Figure 1 shows the configuration of a cylindrical fiber bundle whose free ends define a pla perpendicular to the axial direction of the bundle. With this configuration, the end rounded of the figure is possible using a conventional abrasive method.

In the configuration of figure 3, the free ends of the fibers in the bundle define a conical shaped surface.

Referring now to Figures 4 and 5, it can be seen in Figure 4 that those fibers 10 in bundle 12 which are closest to the central part of the bundle are supported laterally by a greater number of surrounding fibers than those closest fibers 14. to the periphery of the bundle 12. Po therefore, the fibers which are closer to the periphery oppose less deflection to an end rounding tool d passing over the free ends of the fiber. It should be understood that, as seen in Figs. 1, 2 and 3, the palm is grasped radially at a predetermined distance from the free ends of the fiber so that each fiber can be deflected laterally upon contact with the working surface of the fiber. the fiber rounding tool. In the conical configuration shown in Figure 5, the fibers in the central part of the bundle have a greater cantilever length than those near the periphery. Recalling that according to the theory of the resistance of the materials, the deflected material is calculated by the cantilever beam formula. f - Z_ _ß_ 3 E • I in which: f = displacement towards the sides of the fiber tip. F = force exerted on the end of the thread. L = fiber yarn length E, I = constants for a given material and beam section d.

It is easily seen that the greater resistance to flexing of the fibers in the central part of the bundle due to lateral support by a greater number of surrounding fibers can be compensated by a larger cantilever length of the fibers in the central part of bundle. In the preferred embodiment, each fiber end in the bundle has a given cantilever length to provide an essentially consistent flexural strength through the cross section of the bundle with respect to lateral deflection upon contact with the end rounding tool.

Even though the aforementioned requirement satisfied better with the conical configuration shown in Figure 3, it is possible to use the configuration of Figure 2 where the free ends of the fibers define a plan inclined to the plane perpendicular to the axial direction of the bundle.

In the method illustrated in Figure 6, the individual bundles 20 are collected from a pre-cut parallel and packed fiber supply 22. The bundle or cluster 20 is radially grasped and therefore axially held in the handle 24. The handle 24 with the bundle or lock 2 hooked there, is then moved between a complementary pair of plungers 26 and 28, and the handle 24 is released. As seen in the drawings, the plungers 26 and 28 have complementary concave and convex profiles. When the plungers 26 and 28 are engaged with the axial ends of the bundle or lock 2 while the handle 24 is released, the fibers are moved axially with respect to each other, resulting in a configuration similar to that shown in Figure 3. L The handle 24 is then engaged again and moved to an end rounder 30. The end rounded tool 30 has a rotating cylinder 32 which defines a work surface which has frictional properties rather than abrasives. The details of the nature and material of the end rounding tool are found in the German Utility Model Patent No. 296 14 118. It should be noted here that the rotational speed of the cylinder 32 is essentially in excess of that for the rounding tools. of end which are d abrasive nature. Also, an important aspect of the end rounding tool is that the cylinder 3 has one on a material which produces frictional and frictional heat on contact with the free ends of the fibers of the thermoplastic material. Finally, it is important to have this coating of the cylinder 32 thermally decoupled from the cylinder body 32 so that the cylinder body 32 does not form a heat sink. The shape of the end rounding tool is not critical. For example, a rotating disc can be used.

Even when a single rounding tool: is shown in the drawings, the preferred method uses a plurality of processing steps. At each processing step, the free ends of the fibers in the bundle or lock are exposed to a rotating end rounding tool.

After the last processing step s has completed, the handle 24 is moved to a discharge station where the handle 24 is released. The axial ends of the fibers are now engaged between a pair of plungers 34 and 36, which have the opposite flat alignment surfaces. The rounded ends of the processed fibers are now aligned in one plane, and the fibers are discharged into a box 38 containing the finished fibers, ready to be used in an implant molding method and where these are attached to a brush body while the brush body is injection molded.

The embodiment of Figure 7 differs from Figure 6 only in that the pistons 34A and 36A with the cover plates are used to align the finished fibers within the case 38.

In the embodiment shown in Figure 8, continuous yarn 40 of parallel fiber is radially grasped by means of a handle 41 at a first distance DI from the free ends of the fibers. A second handle 43 s provides a second distance D2 from the free ends of the fibers, but it is released. A profiling member 44 having a concave conical profiling face is now engaged with the free ends of the fibers at point 42 in Figure 8. The fibers are moved axially to align to the free ends on a surface of the shape desired conical, the outer fibers of the yarn are bulged outwards as seen at point 45 in Figure 8. The handle 43 is now hooked, and the free ends of the fibers are exposed to the end rounding tool 30 as in the methods d Figures 6 and 7. After all the processing steps have been completed, the bracket 43 is released and the desired length of the rounded end fiber is cut from the yarn 4 and then moved to the fiber box 38.

Claims (11)

1. A method for rounding end fibers of thermoplastic material for use in the manufacture of brushes fibers are presented to an end rounding tool and the free ends of the fibers are exposed to a work surface in the tool, the relative movement between the fiber ends and the working surface causes the fiber material to be heated by friction of a predetermined intensity, where the fibers while being exposed to the work surface of the tool allows them to flex laterally and to maintain in an axial direction with its free ends commonly defining a surface different from a plane which is perpendicular to the axial direction, characterized in that the fibers are presented in the tool as a loose bundle or strand of fiber grasped radially at a predetermined distance from the ends free of fibers.

2. The method as claimed in clause 1, characterized in that the shape of said surface e is different from a plane.

3. The method as claimed in clause 1, characterized in that the fibers have a cantilever length which is greater in parts of said surface near the center of the bundle than in positions closer to the outer edge of said surface.

4. The method as claimed in clause 1, characterized in that said surface has a convex shape.

5. The method as claimed in clause 1, characterized in that said surface has a conical shape.

6. The method as claimed in clause 1, characterized in that said surface is a plan inclined to the plane perpendicular to said axial direction.

7. The method as claimed in clause 1, characterized in that each free end in the bundle or strand has a cantilever length determined to provide a resistance to bending essentially consistent across the cross section of said bundle of tuft with respect to the lateral deflection on contact with the work surface.

8. The method as claimed in any of clauses 1 to 7, characterized in that the working surface of the tool is cylindrical.

9. The method as claimed in any of clauses 1 to 8, characterized in that a bundle or tuft is collected from a supply of pre-cut and packaged fibers, at least one axial end face of said bundle or lock is hooked by a profile member having a profiling face corresponding to the shape of said surface to change the fibers axially with respect to one another until the free ends of said fibers define said surface, the bundle or lock is radially grasped, the ends of fibers of said fibers are exposed to the working surface of said tool, said lock or bundle is released and said fibers are changed axially with respect to each other to align their axial ends in a plan perpendicular to their length, and said fibers are deposited e a container containing end fibers, rounded.

10. The method as claimed in any of clauses 1 to 8, characterized in that a parallel fiber continuous thread is radially grasped at a first distance (DI) from the free fiber ends, while these are aligned in a plane , said free ends are hooked by a profiler member having a profiler that corresponds to the shape of said surface to change the fibers axially with respect to each other until the free ends of said fibers define said surface, and bunch or strand is radially grasped at a second distance (D2) from the free fiber ends, which is smaller than said first distance (DI), the free ends of said fibers are exposed to said working surface of the tool, said wire is released at a second distance from the fiber free ends to allow said fibers to move axially with respect to each other to align their ends ax In a plane perpendicular to its length, a length of fiber including said ends of free fibers is cut from said fiber yarn, and the lengths of staple fiber are deposited in a container containing rounded end fibers.

11. The method as claimed in clauses 9 or 10, characterized in that the step of exposing the free ends of said fibers to the work surface repeats a plurality of times with the different work tools.