WO1999017915A1

WO1999017915A1 - Multi-component injection molded toothbrush and manufacture thereof

Info

Publication number: WO1999017915A1
Application number: PCT/US1998/019397
Authority: WO
Inventors: Jonathon Roberts; Joseph Fattori; Robert Moskovich
Original assignee: Colgate-Palmolive Company
Priority date: 1997-10-06
Filing date: 1998-09-17
Publication date: 1999-04-15
Also published as: AU9394798A; TW411266B

Abstract

This invention is directed to a multi-component injection molded toothbrush having a generally longitudinal axis, in which a soft handle grip portion is molded to an internal handle section and a method for manufacturing same. One component is a relatively rigid toothbrush body comprising a head, a neck connected thereto, an internal handle connected to said neck, and, optionally, terminating at a base, which permits the brush to be self-standing. The other is a relatively soft external handle grip. The internal handle has a defined outer diameter, and a plurality of bristles is disposed on the head. The second component comprises a relatively soft elastomeric material injection molded to form an external handle section which covers the internal handle section of the toothbrush body. The external handle section has an internal handle diameter, which is greater than the external diameter of the internal so that the rigid first component does not penetrate the external handle section along its longitudinal axis. The disclosed method permits the external handle grip design to be changed relatively quickly and inexpensively when it is desired to manufacture brushes of different design. This is accomplished by molding the brush body with a universal configuration and molding the external handle grips in removable mold cavity blocks, which may be removed and new ones of different design substituted therefor when it is desired to manufacture brushes of new handle grip design.

Description

MULTI-COMPONENT INJECTION MOLDED TOOTHBRUSH AND MANUFACTURE THEREOF

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to toothbrushes made from at least two components. The first component comprises a relatively rigid or hard plastic material, which forms the bristle-bearing head, neck, inner handle or stem portion, and, optionally, the base of the brush. The second component comprises a soft elastomeric material, which forms an outer gripping portion, and is injection molded over the inner hard plastic handle portion of the brush. The brush is manufactured by a dual component injection molding process such that the elastomeric material surrounding the hard plastic inner handle portion of the brush may be easily substituted with other elastomeric grips of different design without the need to retool an entire dual component mold, which is quite expensive.

Description of the Prior Art

Toothbrushes made of two components, one relatively hard and the other relatively soft, especially in the hand grip area of the handle, are well known in the art and generally are manufactured by a conventional dual injection molding process. According to this process, a hard plastic portion of the brush is molded in a first mold. Traditionally, the hard plastic portion contains either voids or channels where the second, soft component is to be molded. The molded hard plastic portion is then transferred manually or automatically to a second part of the mold where the soft rubber or elastomeric material is injected to fill the voids in the hard plastic skeleton and run along any molded channels where a chemical /mechanical bond holds the two components together. One such process is illustrated, for example, in PCT application no. WO 94/05183 to Jordan A.S. of Norway. The brush shown therein, however, has portions of the hard plastic handle that penetrate the outer elastomeric jating. EP application 0 61 1 533 to Johnson & Johnson also discloses a two component brush, but, again, portions of the hard plastic handle penetrate the outer elastomeπc coating. G.B. application 2 167 995 to Heath illustrates a toothbrush in which the hard plastic handle takes the form of a tapeπng prong which is covered by a sleeve of relatively soft material However, the sleeve is generally detachable from the brush, although since it is made separately from the brush and is force fit over the handle, it may be secured thereto by a suitable adhesive. U.S. 4,283.808 to Beebe is similar to Heath, in that a removable gπpping device is taught, although it, too, may be permanently affixed to the brush portion by means of a bonding agent or glue. U.S. 5,305,490 to Lundgren discloses a one-piece brush with an enlarged tubular handle with an anti slip gπpping surface. U.S. 5.361.446 to Rufo discloses a brush with a uisposable head and a permanent handle. Thus, although there has been mnovaϋon in the art of dual component toothbrushes, none of these publications disclose a dual componeⁿt toothbrush manufactured by injection molding technology wherein the brush design can be radically altered in a relatively short peπod of time by the expedient of changing only that portion of the mold that is involved in the manufacture of the elastomeπc handle gπp portion of the brush.

SUMMARY OF THE INVENTION

According to the practice of this invention, an injection molded, dual component toothbrush is provided which solves the problem of changing the design of the external handle gπp relatively quickly without the necessity of purchasing entire new molds. Instead, only that portion of the mold which is used to mold the gπp matenal must be changed. This permits manufactunng and marketing flexibility of a line of toothbrushes that can dramatically change appearance in record time. This is accomplished by first molding a hard plastic skeleton having a handle portion of smaller external diameter than the internal diameter of the soft elastomeπc coating such that the hard plastic skeleton of the handle section does not penetrate the outer surface of the sott elastomeπc coating. However, the hard plastic ay penetrate the elastomeπc coating onlv at the base of the handle if so desired.

Further according to the invenUon, is a

to manufacture such injection molded, dual component toothbrushes.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side elevational view of the hard plastic skeleton or portion of the toothbrush of this invention.

Figure 2 is a view similar to Figure 1 and illustrates one embodiment of the complete toothbrush of this invention

Figures 3A and 3B are side elevational views of two additional toothbrush embodiments of this invention.

Figure 4 is a top plan view of the knock-out side of a 12+ 12 cavity mold.

Figure 5 is a side view of both halves (the knock-out side and the injection side) of the mold partially illustrated in Figure 4

Figure 6A is a cross-sectional view of both halves (the knock-out side and the injection side) of the mold partially illustrated in Figure 4, showing a cavity in which a hard or rigid handle is molded.

Figure 6B is a cross-sectional view of both halves (the knock-out side and the injection side) of the mold partially illustrated in Figure 4. showing a cavity in which an elastomeπc outer gπp is molded over a hard or ngid inner handle stem.

Figure 7 is an exploded view of two mold cavity blocks used to manufacture six toothbrushes according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the preferred embodiments of the invention, where, in the drawings, like numerals have been used to designate like or similar elements.

Referπng now to Figure 1 , a toothbrush skeleton of the present invention, made of relatively ngid plastic matenal. is designated generally as 10. It is shown in an upπght, self-^crandmg position, although it should be understood that it does not have to ue self-standing. Skeleton 10 is made up of head portion 12, which will bear the bπstles in the complete brush, neck 14, which is connected to head 12, internal handle section 16, which terminates in base 20. which permits the brush to be self-standing, a feature that is of particular interest for c dren. Handle section 16 is here illustrated as of solid elliptical cross-section. It will be understood, however, that the cross section of internal handle section 16 may be circular, ovoid, polygonal or of any other configuration, and it need not be solid but may be πbbed or hollow, or any combination of two or more of these constructions. If handle stem 16 is hollow, then a solid core, preferably metal, would be inserted therewithin duπng the second injection molding cycle to support its integπty duπng this second cycle Base 20 is an optional vaπant and is not needed to practice the present invention.

Referπng now to Figure 2 of the drawings, a complete toothbrush 18 according to the invention is shown also in a vertical, self-standing position. As shown herein, head portion 12 bears a plurality of tufts of bπstles 24. Neck 14, which is connected to head 12 joins internal handle section 16 (not visible), which is covered by elastomeπc gπp portion 22, the handle terminating at base 20.

Referπng now to Figures 3A and 3B. there are shown two additional vaπants of brushes that may be made by the method of this invention. In Figure 3A, elastomeπc gπp portion 22A of brush 18A is dramatically different from elastomeπc gπp portion 22 illustrated in Figure 2 and from elastomeπc gπp portion 22B of brush 18B illustrated in Figure 3B, which further illustrates another vaπant of the brush oi the present invenuon. wherein optional flange 25 separates neck 14 from internal handle section 16 (not visible).

Referring now to Figure 4 a simplified plan view ot the bottom half or "knock-out" side 26 of the mold is shown. The corresponding removable cavity blocks in the upper half of the mold or the "injection ' side 28 are a mirror image of the side shown here, with the exception of the inlets for injecting the thermoplastic mateπal, which forms the hard or ngid skeletons 10, and the elastomeπc mateπal, which forms the external handle portion 22 contained therein, which are standard features in the injection molding art and are not part of the invention herein. Injection side 28 of the mold is best shown in Figs. 5. 6A and 6B. In this connection, ejector pins and other conventional features of KO side 26 are also not illustrated herein as they, too, are standard in the injection molding art and are not part of the invention herein.

As shown in Fig. 4, knock-out side 26 of a 12+12 cavity mold is shown. Such a mold is capable of making 12 brushes at a time. The portion of the mold 26A (illustrated here as the left side of Fig. 4) is that portion of the mold in which a molten thermoplastic mateπal is injected into each cavity

(36a-361) in the mold (12 in this instance) to form, upon cooling, the hard plastic mateπal forming the skeleton 10 of the brush, e.g. head 12. neck 14, inner handle 16. and base 20. These skeletons 10 are then transported, either manually or automatically, (by means not shown, as not related to the present invention) to a second portion of tlie mold, 26B, (illustrated here as the πght side of Fig. 4), containing a second seπes of cavities (38a-381), where a relatively soft elastomenc matenal is then injected into each cavity, to thereby form, upon cooling, a two-component brush, minus, of course, the bπstles which are subsequently implanted, cut to size, and end rounded in a conventional tufting and finishing operation, which is standard in the brush art and is not illustrated herein as not being part of the present invention. Four leader pins 30a. 30b. 30c. and 30d ensure that the injection 28 and knock-out 26 sides of the mold are properly aligned when both halves of the mold are closed. As shown in the left side 26A of the knock-out side of the mold, there are 12 cavities (36a. 36b. 36c. 36d, 36e. 36f. 36g, 36h, 36i, 36j, 36k, and 361) that form the bottom h.-i^" of hard or rigid skeleton 10 illustrated in Fig. 1. The injection side of the mold 28. not illustrated in Fig 4, contains the corresponding halves of these cavities. The right side of the mold, 26B, illustrates the portion of the mold in which each skeleton 10 now, in essence fills the interior of each mold cavity, and each of the mold cavities 38a-381 (12 as before) now constitute the outer wall of the mold chamber, so that upon the injection of molten elastomer into each mold cavity 38a-381 (and the corresponding halves of these cavities contained in the injection side of the mold, not illustrated here), and subsequent cooling thereof, a soft elastomeric external handle grip will be molded to internal handle portion 16 of skeleton 10 having whatever shape is dictated by the external contour of each mold cavity 38a-381. The balance of the mold cavities which hold base 20, neck 14, and (unbristied) head 12 of skeleton 10. remain the same and unchanged. It will be appreciated, therefore, that, in the portion of the mold in which the elastomer is molded over rigid handle section, each skeleton 10 serves as the interior mold surface while each cavity 38 serves as the outer mold surface, and the elastomeric material thus fills the space created between these inner and outer mold surfaces.

Given the universal nature of skeleton 10, the shape of external elastomeric handle 22 can be changed by the simple expedient of changing the shape of mold cavities 38a-381. This is made relatively quick and comparatively inexpensive by utilizing removable first 32a and second 32b cavity blocks, which can easily be removed from the knock-out half of the mold, as well as corresponding removable third 32c and fourth 32d (not shown) cavity blocks, which can also easily be removed from the injection half of the mold. The removable cavity block 32a is held in place by tapered wedges 40c and 40d and screws 42e, 42f, 42g, and 42h. while removable cavity block 32b is held in place by tapered wedges 40a and 40b and screws 42a, 42b. 42c. and 42d. Corresponding tapered wedges and screws are present to hold the two removable cavity blocks on the injection side 28 of the mold.

Thus, to change the brush of the present invention by utilizing a dramatically different external handle gπp design, the mold is opened, the screws on both halves of the mold are removed, the tapered wedges removed, the removable cavity blocks taken out and the new ones substituted therefor. Then, the wedges are replaced, the screws replaced and tightened and the mold is ready to manufacture the new brush design. Therefore, by replacing only that portion of the mold (i.e. the four removable cavity blocks) that forms the elastomenc external handle (since the balance of the mold cavity that forms the head 12, neck 14. and base 20 of the skeleton remains in the mold), the cost of changing from a particular brush design to a new one is greatly reduced. And by utilizing four removable blocks, which can easily be replaced with four new ones, the cost of a changeover is reduced to approximately one-fifth the cost of an entirely new mold. Correspondingly, manufacture and delivery of only four removable mold cavity blocks takes approximately only one-third the time it would take to manufacture and deliver an entirely new mold.

Referring now to Figure 5. a front side view of both the injection side 28 and the knock-out side 26 of the mold, taken along line 5-5 of Figure 4, is shown. Injection side 28 of the mold, in this view, illustrates the third removable mold cavity 32c (the fourth removable mold cavity, and the wedges and screws supporting same not being visible in this view), supported in place by wedges 40g and 40h and screws 42m and 42n. Six mold cavities 36 are shown on the left side of Fig. 5, which show views through internal handle 16, while the right side of Fig. 5 show views through internal handle 16 and external grips 22 in mold cavities 38. Knock-out side 26 of the mold, in this view, illustrates the first removable mold cavity 32a (the second removable mold cavity, and the wedges and screws supporting same not being visible in this view), supported in place by wedges 40c and 40d and screws 42e and 42g. An empty space 44. which permits the brush ejector pins (not illustrated) to remove molded brusnes from the mold separates the balance of the knock-out side 26 of the mold from pm plate 46, pin backing plate 48. and bottom clamp plate 50 Again, as these are standard components of conventional injecuon molds, no further discussion thereof is deemed necessary

Figure 6A is a cross-sectional view of both halves, i.e. injection side 28 and knock-out side 26. of the mold of Figure 4, taken along lines 6A-6A, showing a cavity 36 in which a hard or rigid skeleton 10 is molded.

Figure 6B is a cross-sectional view of both halves, i e. injection side 28 and knock-out side 26, of the mold of Figure 4, taken along lines 6B-6B. showing a single cavity 38 in which an elastomeπc outer handle 22 is molded to a hard or ngid skeleton 10

Figure 7 is an exploded view of both halves, i.e. injection side 28 and knock-out side 26, of two removable mold cavity blocks 32a and 32c containing twelve half cavities 38g through 38r. which form six complete cavities when the knock-out and injection sides of the mold are closed to manufacture toothbrushes according to this invention.

All terms of oπentation, such as vertical, left, πght and the like, are employed only to facilitate the descπption and are not intended to be construed as limitations.

The skeletons 10 may be made from relatively ngid. compared to the elastomer, thermoplastic mateπals, such as nylon, polypropylene, polyethylene, polyethylene terephthalate, polycarbonate, polyacrylate, polymethylmethacrylate. styrene/acrylonitπle copolymers (SAN), cellulose acetate, and cellulose acetate propionate (CAP). Hard or ngid, as applied to the toothbrush body, means that the brush is self-supporting. However, the "hard or ngid" body does not exclude the possibility that portions of the neck and/or head can be flexible in the manner shown in U.S. 5,052.071 ; European Patent 0 291 522; co-pending patent applications U.S.S.N. 08/762.783 filed 12/ 10/96: U.S.S.N. 08/881 ,735 filed June 24. 1997; and U.S.S.N. 08/881 ,740 filed June 24, 1997, the teachings of which are incorporated herein by reference in their entirety.

The thermoplastic elastomer which forms the eiastomeπc grip 22 may be of any elastomeπc mateπal compatible with and capable of bonding with the thermoplastic skeleton material. Suitable elastomers include a thermoplastic vulcanate (TPV) consisting of a mixture of polypropylene and EPDM (ethylene propylene diene monomers) (Santoprene brand), or Vyram (brand), or mother TPV consisting of a mixture of polypropylene and natural rubber, botn Santoprene and Vyram (brands) being elastomers marketed by Advanced Elastomer Systems. A preferred elastomer includes Kraton, a brand of styrene block copolymer (SBC) marketed by Shell, and Dynaflex G 2706 (brand), a thermoplastic elastomer marketed by GLS Corporation and which is made with Kraton (brand) polymer. Other useful elastomers include rubber, polyurethane, polyisobutylene. polypropylene, and polybutadiene.

The bristles are conventionally made of nylon, but they may also be fabricated from polyamides. polyolefins, polyesters, or natural fibers.

Generally speaking, the present invention is directed to a multi- component injection molded toothbrush having a generally longitudinal axis. One of the components is relatively rigid and forms the toothbrush body through a first injection molding step, and the second is softer than the first component and forms an external handle grip, the toothbrush body comprising a head, a neck connected to said head, an internal handle connected to said neck, and, optionally, terminating at a base, which permits the brush to be se'f-standing. The internal handle has a defined outer diameter, and a plurality of bristles is disposed on the head. The second component is comprised of a relatively soft elastomeric material injection molded through a second injection molding step to form an external handle section which covers the internal handle section of the toothbrush body. The external handle section has an internal diameter, which is greater than the external diameter of the internal handle so that the rigid first component does not penetrate the external handle section along its longitudinal axis.

The foregoing description and drawings are intended to be illustrative of the present invention, but various changes and modifications thereto can be made without departing from the spirit and scope of the invention as defined in the accompanying claims.

Claims

What is claimed is:

1 A multi-component injection molded toothbrush having a generally longitudinal axis, one of said components being relativ* <y ngid and forming the toothbrush body through a first injection molding step, and the second of said components being relatively softer than said first component and forming an external handle g╧Çp, the toothbrush body comp╧Çsmg a head, a neck connected to said head, and an internal handle connected to said neck, said internal handle having a defined outer diameter, wherein a plura_^ty of bnstles is disposed on said head, and wherein said second component is comp╧Çsed of a relatively soft elastome╧Çc mate╧Çal injection molded through a second injecuon molding step to form an external handle section which covers said internal handle section of said toothbrush body, said external handle section having an internal diameter, wherein the internal diameter of said external handle section is greater than the external diameter of said internal handle whereby the ngid first component does not penetrate said external handle section along its longitudinal axis.

2. The toothbrush of claim 1 wherein said neck is separated from said internal handle by an integral flange.

3. The toothbrush of claim 1 wherein said internal handle terminates at the end most remote from the neck in a base which permits the brush to stand in a substantially up╧Çght position relative to a ho╧Çzontal support surface.

4. The toothbrush of claim 1 wherein said thermoplastic elastomer which forms the external handle is selected from the group consisting of a mixture of polypropylene and ethylene propylene diene monomers; a mixture of polypropylene and natural rubber; a styrene block copolymer; rubber, polyurethane, polyisobutylene, polypropylene, polybutadiene and mixtures thereof.

5. The toothbrush of claim 1 wherein said relatively rigid toothbrush body is a thermoplastic material selected from the group consisting of nylon, polypropylene, polyethylene, polyethylene terephthalate, polycarbonate, polyacrylate, polymethvlmethacrylate, styrene/acrylonitrile copolymers. cellulose acetate, cellulose acetate propionate and mixtures thereof.

6. A method of manufacturing a multi-component toothbrush having a generally longitudinal axis comprising a body including a head made out of a first component; an external handle made out of a second component covering a portion of said body; and a plurality of bristles disposed on said head; said toothbrush body comprising a head, a neck connected to said head, and an internal handle connected to said neck, said external handle having a defined inner diameter and being injection molded over said internal handle by use of removable mold cavity blocks in an injection molding machine, said method comprising the steps of: molding in a first injection molding step in an injection molding machine said toothbrush body made of a first component comprising a relatively rigid or hard thermoplastic material such that said internal handle section of said toothbrush body has a defined outer dimension; molding said external handle over said internal handle portion of said toothbrush body in a second injection molding step in an injection molding machine, said external handle made of a second component comprising a relatively soft elastomeric material such that said external handle has a defined internal dimension, wherein the internal dimension of said external handle section is greater than the external dimension of said internal handle so that said inner handle does not penetrate said external handle along its longitudinal axis, wherein said external handle is molded in said injection molding machine in removable mold cavity blocks, such that a variety of external handles may be molded over said internal handle portions of said toothbrush body by replacing only said removable mold cavity blocks in said injection molding machine; affixing a plurality of tufts of bristles to said head; trimming the tooth contacting ends of said bristles to predetermined lengths: and rounding the tooth contacting ends of said bristles to avoid damage to teeth and gums when used to brush teeth.

7. The method of claim 6 wherein said neck is separated from said internal handle by an integral flange.

8. The method of claim 6 wherein sai╬▒ internal handle terminates at the end most remote from the neck in a base which permits the brush to stand in a substantially upright position relative to a horizontal support surface.

9. The method of claim 6 wherein said thermoplastic elastomer which forms the external handle is selected from the group consisting of a mixture of polypropylene and ethylene propylene diene monomers; a mixture of polypropylene and natural rubber: a styrene block copolymer; rubber, polyurethane, polyisobutylene, polypropylene, polybutadiene and mixtures thereof.

10. The method of claim 6 wherein said relatively rigid toothbrush body is a thermoplastic material selected from the group consisting of nylon, polypropylene, polyethylene, polyethylene terephthalate, polycarbonate, polyacrylate, polymethylmethacrylate, styrene/acrylonitrile copolymers, cellulose acetate, cellulose acetate propionate and mixtures thereof.