APPARATUS AND METHOD FOR PRODUCING ROUNDED BRUSH TIPS

Abstract: Apparatus and methodology for rounding the bristle tips of twisted wire brushes (26). Each twisted wire brush (26) is mounted in a carrier (28) by means of a spindle (30) which permits the brush (26) to be rotated along its longitudinal axis. The melting of the synthetic bristle tips takes place in a heated chamber (20) which includes one or more heated cylindrical cavities (38) which may extend over a portion or the whole of the length of each brush (26). When the carrier (28) approaches the chamber, the chamber (20) is lowered over the carrier (28) so that each of the individual brushes (26) is inserted into a heated cavity (38). When inserted in the cavity (38) the brush (26) is rotated on the spindle (30) while it is heated. The rotation and heating causes the individual bristle tips to melt into a rounded ball without adhering to each other. Thereafter, the heating chamber (20) is raised, the carrier (28) indexed and the process repeated.

Description: This invention is directed to apparatus and method for rounding the bristle tips of twisted wire brushes. Twisted wire brushes are used in a variety of applications, particularly in personal care products. These brushes consist of a multiplicity of fine synthetic bristles held and secured by a pair of twisted metal wires which form the core of the brush. The bristles extend in various directions from the twisted wires and the overall brush has a cylindrical or a tapered cylindrical outer surface. The bristles are generally formed by thin nylon or plastic filaments. Because the bristle tips are cut, the ends of the bristles are quite sharp and can cause injury if inserted in the eye. This is a particular problem when the twisted wire brush is used as a mascara brush, which is a common application. Hollow bristle filaments have recently come into use since they are quite flexible and provide a uniform cylindrical appearance to the brush. However, the tips of these filaments are even sharper than solid filament bristles with a consequent increased possibility of injury. A variety of processes have been proposed for rounding the bristle tips of various types of brushes. Such processes have included bringing the bristle tips into contact with a heated surface. Non-contact processes see for example US-A- 2587792 and WO 89/05706 have included the use of heat lamps or laser beams acting on the bristle tips to melt same. However, these processes have generally been applicable only to brushes in which all of the bristles are oriented in the same direction, such as hair brushes. Such processes are unsatisfactory for use with brushes having a cylindrical outer surface such as twisted wire brushes. SUMMARY OF THE INVENTION The present invention is directed to apparatus and method for rounding or balling the ends of the synthetic bristles of twisted wire brush. The invention operates without contact with the bristles and in a manner suitable for high speed manufacturing on an assembly line basis. The invention operates on the twisted wire brushes after the twisting process. Each twisted wire brush is mounted in a moveable carrier by means of a spindle which permits the brush to be rotated along its longitudinal axis. The melting of the bristle tips takes place in a heated chamber which includes one or more heated cylindrical cavities. When the carrier approaches the chamber, the chamber is lowered over the carrier so that each of the individual brushes is inserted into a heated cavity. When inserted in the cavity, the brush spindle is rotated by an external drive motor so that the brush is rotated while it is heated. The rotation and heating causes the individual bristle tips to melt into a rounded ball without adhering to each other. After a predetermined period of time, the heating chamber is raised and the now finished brushes displaced by the carrier. The process is thereafter repeated on the next set of brushes. Different configuration heating chambers may be used to process the brush tips along the entire length of the brush or along only a preselected portion. The improved apparatus and method set forth herein provides an efficient and relatively inexpensive processing for the rounding of the synthetic filament bristle tips of twisted wire brushes suitable for use in cosmetic application. The tiny spheres forming the tips of the processed bristles reduce the chance of injury and aid in the retention of the liquid to be applied by the brush. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference is made to the following drawings in which: Fig. 1 is a perspective view of the apparatus for transporting, rotating and heating the bristle tips in accordance with the improved methodology; Fig. 2 is a cross-sectional view of a first configuration of a heating chamber acting upon the individual twisted wire brushes; and Fig. 3 is a cross-sectional view of a second configuration of a heating chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates the apparatus 20 for rounding the tips of synthetic bristle held by a pair of twisted wires. An indexable carrier wheel 22 is used to transport the brushes to be acted upon by a heating chamber 24. Each of the twisted wire brushes 26 is held in a vertical position by a rotatable spindle assembly 28 which includes a chuck 30 for grasping the twisted wire portion of brush 26. Each spindle 28 is journaled for rotation in carrier wheel 22. Extending from the underside of carrier wheel 22 and coupled for rotation with spindle 28 is an idler wheel 32, which when rotated, rotates spindle 28. In operation carrier wheel 22 is rotated in direction A and halted (i.e. indexed) so that brushes 26 are positioned beneath heating chamber 24. At this point the idler wheels 32 will be engaged by a drive wheel 34 which rotates in direction B. Idler wheel 34 has a rubber rim 36 which contacts the idler wheels 32 of two spindles 26 to rotate them in direction C. At this point heating chamber 24 is displaced vertically down upon the two rotating brushes 26. A cross-sectional diagram of a first heating chamber 24 is shown in Fig. 2. Heating chamber 24 contains multiple hollow cylindrical cavities 38 which, when heating chamber 24 is lowered, will surround the twisted wire brushes 26. Contained within heating chamber 24 are a series of electrical heating element 40 which are connected to a power supply 42 for causing heat to radiate into the hollow chambers 38 towards the rotating twisted wire brushes 26. Heating element 40 can be any suitable heating element such as electrical resistance wire. Since heating chamber 24 and the walls of cavities 38 are constructed from metal such as steel, the heat is evenly disposed about the chamber and this, in conjunction with the rotation of brushes 28, provides that the melting of the bristle tips is uniform and controllable. Furthermore, the uniform heating prevents the melted tips of the bristles from sticking to one another. After waiting a predetermined period of time as the brush tips melt, which is determined empirically from the size, shape, type and material of the bristles, heating chamber 24 is displaced upwardly away from brushes 26. Threreafter, carrier 22 is again indexed in direction A which will move the completed brushes away from the heating chamber and the next pair of brushes will be positioned for the heating process to be repeated. After processing, the brushes may be removed from the spindle by any suitable means, either automatically or manually. After processing, the individual bristles have a spherical ball at each end. The balls have a diameter greater than the shaft of the bristle which greatly lessens the chance of injury and aids in the retention of the fluid, such as mascara, which is applied by the brush. The size of the ball can be controlled by the heating time. For certain application, it is desirable that all of the bristle tips not be rounded. For example, it is desirable with respect to brushes that have a tapered profile, that only the longer bristles near the handle end be rounded, with the shorter brushes remaining unprocessed. A second embodiment of a heating chamber shown in Fig. 3 provides such a result. In Fig. 3, brushes 44 having a tapered profile are processed in a heating chamber 46 which has cavities 48 which are open at the top and extend only over a portion of the length of brushes 44 so that the upper portion of brushes 44 extend out of cavities 48 and the bristles will thus remain unheated and unrounded. The cavities 48 are heated and the brushes rotated in a similar manner to that of chamber 24 of Fig. 2. It is to be noted, that many modifications may be made to the above described system. For example, carrier wheel 22 could be replaced by a linear conveyor. Furthermore, the heating chambers could have anywhere from one to a large number of cavities for processing brushes, dependent upon the volume required. Also, the idler wheel system could be replaced by any other suitable means for rotating the brush holding spindles.

Claims: A method for producing rounded tips on heat meltable bristles of brushes having longitudinal axes, comprising the steps of: a) providing a hollow cylinder, said hollow cylinder having walls which are heated to a temperature sufficient to melt the material of the brush bristles; b) inserting a brush into said hollow cylinder; c) rotating said brush around its longitudinal axis within said hollow cylinder until the tips of said brush bristles are melted; and d) removing said brush from within said hollow cylinder. The method as claimed in claim 1 and further including the step of translating said brushes laterally with respect to said hollow cylinder before and after said melting operation step. The method as claimed in claim 1 or 2 and further including the step of mounting said brushes on an indexable wheel in a rotatable manner. The method as claimed in any one of claims 1 to 3 and further including the step of displacing said hollow cylinder along the longitudinal axis of said brush in order to insert and remove said brush from said hollow cylinder. The method as claimed in any one of claims 1 to 4 and further including the step of providing multiple hollow cylinders for receiving multiple brushes. Apparatus for producing rounded tips on heat meltable bristles of brushes having longitudinal axes, comprising : (a) a heating chamber having at least one hollow cavity having at least one opening and a continuous inner wall surrounding said at least one opening; (b) first means for mounting a plurality of brushes; (c) second means for rotating each brush about its longitudinal axis; (d) third means for intermittently translating said plurality of brushes; and (e) fourth means for moving said heating chamber back and forth between a first position in which said at least one hollow cavity receives a corresponding one of said plurality of brushes while it is stopped with said continuous inner wall of said at least one hollow cavity being at least generally parallel to the longitudinal axis of the brush and a second position in which said at least one hollow cavity is spaced from said plurality of brushes. Apparatus as recited in claim 6 characterised in that said heating chamber has a plurality of hollow cavities. Apparatus as recited in claim 6 or 7 characterised in that said at least one hollow cavity is cylindrical. Apparatus as recited in any one of claims 6 to 8 characterised in that said second means comprises: (a) a plurality of idler wheels, each one of said plurality of idler wheels being operatively connected to a corresponding one of said first means, and (b) a drive wheel that is selectively engageable with each of said plurality of idler wheels. Apparatus as recited in claim 9 characterised in that said drive wheel is simultaneously engageable with a plurality of said idler wheels. Apparatus as recited in claim 6 to 10 characterised in that said third means comprises an indexable carrier wheel. Apparatus as recited in claim 11 characterised in that said second means comprises a plurality of rotatable spindle assemblies mounted on said indexable carrier wheel. Apparatus as recited in any one of claims 6 to 12 characterised in that said at least one hollow cavity has a single opening into which the brushes extend. Apparatus as recited in any one of claim 6 to 13 characterised in that said at least one hollow cavity has an opening at each end of said continuous inner wall.

Inventors: KIGYOS, FRANK M.
Applicants: ANCHOR ADVANCED PRODUCTS, INC.
Application year: 1990
Main classification: A46D9
IPC codes: A46B3, A46D9, A46D1