Improved toothbrush with interchangeable head and method of manufacture therefor

Abstract: The present invention relates to a device for oral hygiene and a method for manufacture thereof, in which a replaceable insert (4), provided with working elements, can be locked by holding means (39,49,6) inside a housing head integral with to a handle. Said holding means comprise at least one retaining element integral with the insert and a slider (7) which is slidable inside said handle and can be actuated voluntarily between a locked position, in which one locking end (6) thereof is engaged with said retaining element, and a disengaged position.

Description: The present invention relates to a toothbrush with an interchangeable head and a method for the manufacture thereof. As is known, for some time now toothbrushes with an interchangeable head of different shapes and types have existed on the market, said toothbrushes being designed with the fundamental aim of providing a device for oral hygiene and for cleaning teeth which has advantageous ecological and cost-related features since it allows replacement of only the portion which is subject to wear, thereby helping reduce maintenance costs and the impact on the environment. At the present time there exist many types of toothbrushes which can be disassembled and in which the replaceable portion correspondingly has different shapes and size coinciding, in some cases, with the head and a neck portion of the toothbrush and, in other cases, with a much smaller part of the toothbrush. The smaller the replaceable portion, the greater the problems relating to solidity of the assembly, while the bigger the replaceable portion, the more difficult it is to achieve an advantageous result in terms of cost efficiency. The description below will consider a toothbrush in which the replaceable portion is fairly small, i.e. coincides substantially with the insert to which are attached the tufts of bristles intended to perform the brushing action, and for this very reason constitutes the portion which is most subject to wear and is most conveniently replaceable. A device of this type is known, for example, from European patent application EP-A-870,440 in the name of the same Applicants, in which the head is engaged on the toothbrush in a transverse direction with respect to its longitudinal axis. US-5,471,701 and WO98/01055 illustrate other embodiments in which the head is engaged in a parallel direction with respect to the longitudinal axis of the toothbrush. Although an interchangeable head according to the abovementioned known art is advantageous in many respects, it involves certain difficulties which relate to functioning of its assembly system and which have not yet been entirely resolved. In fact, whereas on the one hand it is desirable to obtain an assembly system able to offer the greatest possible retaining action - in order to prevent the possibility of the bristled insert coming out of its seat during use of the toothbrush, ending up dangerously inside the oral cavity - on the other hand it is desirable that the engaging force should not be excessive so that it is possible to perform manually separation of the bristled head from its seat without having to use additional tools. These two conflicting requirements are partially satisfied by using mutually engaging fastening means (ribs and grooves, pins and holes, etc.) which, exploiting the intrinsic deformability of plastic materials, allow the bristled head to be snap-engaged into its seat and, conversely, released with a snap action simply using one's fingers. However, tne assembly and release operations are not always convenient and easy. Moreover, in accordance with specific safety standards applicable in some countries, the fastening means must be safer in order to prevent accidental separation of the bristled head. CH 83482 discloses a brush according to the preamble of claim 1. It must also be pointed out that in all the cases where it is required to form a connection between different mutually interacting or cooperating parts, as in the examples described above, it is necessary to ensure small manufacturing tolerances which often can only be achieved using precise and costly moulds. Since the different component parts of the toothbrush are manufactured separately and then later assembled, problems exist with regard to transfer and recovery of the various parts which require additional manipulators. Moreover, the individual parts must be designed so as to be able to be completely separated and assembled, this resulting in design restraints and/or costly production processes in order to obtain complex shapes. The object of the present invention is therefore that of solving the abovementioned problems. In particular, it is intended to provide a toothbrush with an interchangeable head in which the bristled insert can be engaged in its seat with extreme ease and in which there are fastening means which ensure a firm connection and allow disengagement of the insert only upon a voluntary and active action by the user. According to the invention, it is intended to provide a toothbrush with an interchangeable head in which an elastic action ensuring a firm connection is exerted by a mass of elastomer material which can be easily obtained during the toothbrush moulding process. According to a further aspect, it is also intended to provide a method for manufacturing this toothbrush, which is able to exploit fully the intrinsic characteristics of various materials so as to obtain a toothbrush with an optimum functioning capacity by means of a simple, rapid and low-cost production cycle. These objects are achieved by means of a toothbrush and a method as described substantially in the accompanying claims. Further characteristic features and advantages of the toothbrush and the method according to the invention will emerge more clearly, however, from the following detailed description of a few preferred embodiments provided by way of example and illustrated in the accompanying drawings in which: Figs. 1A, 1B and 1C are, respectively, a side elevation view, plan view of rear side and plan view of front side of an embodiment of the toothbrush according to the invention; Fig. 2 is a view, on a larger scale, of the neck and head portion of the toothbrush shown in Fig. 1C; Fig. 3 is a longitudinally sectioned view along the line II-II in Fig. 2; Fig. 3A is a cross-sectional view along the line III-III in Fig. 3; Fig. 4 is a longitudinally sectioned view, similar to that of Fig. 3, in the disengaged condition of the bristled head; Fig. 4A is a cross-sectional view along the line IV-IV in Fig. 4; and Figs. 5, 6 and 7 are views similar to those of Figs. 2, 3 and 4, respectively, of another embodiment of the invention. The construction of the toothbrush according to the invention will first be described, then illustrating a preferred method for manufacture thereof, which is particularly advantageous. A toothbrush is composed, in a manner known per se, of a handle body 1, a connecting neck 2 and a head 3. The head 3 is configured so as to form a housing 3a into which a bristled insert or head-piece 4 can be engaged. The head-piece 4 is the working part of the toothbrush, intended to perform the brushing action inside the oral cavity, and is the part which, due to greater wear, must be replaced most frequently. A plurality of bristles S are embedded in the insert 4 using any of the known techniques, for example by means of anchoring pieces or using the known "in-moulding" technology. According to the invention, the head-piece 4 can be inserted precisely, but with a minimum of play, into the housing 3a and is firmly fixed therein by holding means partly arranged on the head-piece and partly on the remaining portion of the toothbrush. The holding means comprise, on the one hand, a detent or rib 4a which is formed at the front end of the head-piece 4 and can be engaged in a corresponding seat 3b in the head 3; on the other hand, the rear end of the head-piece 4 is provided with another detent or hook 4b which can be engaged with one locking end 6 of a slider 7. The slider 7 is slidable between two positions, i.e. a locked position and disengaged position, illustrated in Figs. 3 and 4. In the locked position, the end 6 of the slider 7 is engaged (Fig. 3) with the detent 4b of the head-piece: the latter thus remains positively locked inside the seat 3a by means of the detents 4a and 4b which, owing to their size and arrangement, do not allow any separation of the head-piece, even following accidental deformation of the head 3 resulting from pressure of the fingers or during the brushing action. In the disengaged position (Fig. 4), the slider 7 is displaced backwards, as indicated by the arrow D, and therefore releases the detent 4b, allowing expulsion of the head-piece 4 by means of rotation (arrow R) about the detent 4a. In the embodiment shown, the slider is guided during its sliding movement inside the neck 2 of the toothbrush and may be easily operated from the outside by means of a lever or projection 7a with a simple pulling action performed using a finger. The slider is kept actively in its locked position by means of the thrust exerted thereon by an elastic means such as, for example, a compression spring or a rubber plug. The bottom end 7b of the slider rests against a mass of elastic/rubbery or elastomer material G which exerts, on the slider, a continuous pressure into the locked position. Therefore, in order to disengage the head-piece from the seat 3a, it is required to exert a positive and voluntary action on the projection 7a, overcoming the elastic reaction of the mass G and therefore providing that active safety against accidental separation of the head-piece, which has been long sought after. According to another embodiment (Figs. 5, 6 and 7), the elastic mass G' is arranged directly in contact with the projection 7a: in this case, the mass G' of elastic material has the further aim of closing and providing a finish for the sliding seat 8 of the projection 7a. In order to exploit fully the elastic characteristics of the mass G', the sliding seat 8 is wider than the corresponding seat in the embodiment according to Figs. 2, 3 and 4. The engagement travel of the slider on the detent 4b of the head-piece 4 is sufficient, on one hand, to ensure perfect locking even in the case where the housing or the neck of the toothbrush are deformed owing to the pressure exerted by a user during use and, on the other hand, to establish the correct deformation of the elastic mass G or G' so as to obtain the desired level of elastic reaction. The travel of the slider may be, for example, 1 mm. The length and the shape of the slider 7 may be varied depending on the configuration of the handle 1 used, although they constitute secondary aspects compared to the main inventive idea expressed here. In order to avoid the need for excessively small tolerances during manufacture of the head-piece and the housing, but at the same time to prevent the occurrence of troublesome play and ensure a firm retaining action, according to a preferred embodiment the seat 3a comprises an elastic cushion 9 located between the arch of the said housing and the head-piece. When the head-piece 4 is in its operating position (Figs. 3 and 6), the cushion 9 remains compressed and therefore exerts an opposing elastic reaction which tends to take up all the play and stabilise the coupling between the head-piece itself and its housing; moreover, the reaction exerted by the cushion 9 is also partially transmitted to the coupling between the detent 4b and the working end 6 of the slider 7, increasing locally the frictional force and therefore making the locking system even more stable and secure. Preferably, the elastic cushion 9 is arranged in the vicinity of the working end 6 of the slider 7. The elastic energy accumulated in the compressed cushion 9 also facilitates expulsion (see arrow R in Fig. 4) of the head-piece 4 from the housing 3a as soon as the slider 7 is disengaged from the detent 4b. Moreover, preferably, the head-piece 4 has an extended pressure piece 5, at its end directed towards the neck 2 of the toothbrush, which is devoid of bristles S or other cleaning means. This extended pressure piece 5 is particularly convenient for gripping with a finger and applying a slight pressure to the head-piece in order to engage it into its housing, after initially positioning it with the aid of the relief 4a inside the front seat 3b of the head 3. According to a particularly advantageous embodiment of the invention, also with regard to that which will be described further below in relation to the manufacturing method, the brush comprises a skeleton body 100, made of substantially rigid material (for example polypropylene), and a filling 200 consisting of substantially soft and elastic material (for example rubber or elastomer material). In this case, the filling 200 also forms the elastic mass G or G' and the cushion 9; for this purpose the skeleton 100 of the brush has holes 11 and 12 through which the filling 200 is able to pass, respectively, into the housing 3a, so as to form the cushion 9, and into the seat 8, so as to form the mass G'. The toothbrush structure described above, as mentioned, may be obtained in the best possible manner by means of a particular and original manufacturing method which will be described below. During a first step, the locking slider 7 is moulded using a first material, for example Nylon®, polyamide, acetal or polyacetal resins. Then, the slider is retained in a suitable position, by means of support elements (such as, for example, thin pins) inside a subsequent mould in which a skeleton body 100, consisting of a second material which is physically and/or chemically "unrelated" to or "incompatible" with the first material, for example polypropylene, is moulded. In this context, the term "incompatible" is used to indicate that the second material does not tend to adhere to nor merge with the first material during moulding of the second element onto the first element: this ensures that the slider 7 subsequently remains free to slide inside the skeleton body 100 (in the case shown, within the neck 2) of the toothbrush in a sliding seat which it itself defines during the moulding process, without it being necessary to carry out further smoothing or finishing operations on the slider or on the seat itself. Examples of suitable combinations between first material and second material are as follows: polyamide (PA) with polypropylene (PP), polyethylene, polystyrene (PS), SAN, ABS, acetal resin (POM) and the like, or, polycarbonate with polypropylene (PP), polyethylene, polystyrene (PS), SAN, ABS, acetal resin (POM) and the like. Alternatively, it is envisaged arranging in between a thin layer of release substance, so as to prevent the two components from adhering together. The extreme simplicity and rational nature of the solution proposed also allows the entire brush to be obtained by means of successive injection-moulding operations, without having to mould separately the various components and then assemble them during a second step. This results moreover, on the one hand, in a low-cost and simple manufacturing process (the production machinery is correspondingly simpler, without the need for recovery or reassembly of various parts during construction) and, on the other hand, in excellent coupling tolerances which ensure efficient and safe assembly of the two or more toothbrush portions. The skeleton body 100 forms most of the handle 1, the neck 2 and the housing 3, constituting, by its nature, the structural portion of the toothbrush. During a third step, the rough-finished part previously obtained is transferred into a third mould into which the filling material 200 is injected, said material forming, among other things, the elastic mass G or G', with which the slider 7 interacts, and, possibly, also the cushion 9. The filling material is preferably a rubbery or elastomer material and also has the function of completing and providing a finish for the entire toothbrush. Suitable materials are, for example, PTE elastomers which are compatible with the corresponding first and second materials to which they must adhere. It is emphasized that the various moulding steps may be performed in a single multi-components moulding machine, or in several moulding machines arranged in sequence in several stations towards which the toothbrush is conveyed by means of suitable conveying systems which do not form part of the contents of the present invention. As can be easily understood, the toothbrush and the method according to the invention fully achieve the objects described in the preamble. In particular the invention provides a toothbrush with a replaceable head in which, despite the small dimensions of the replaceable portion, solid assembly together with safe use are achieved. In fact, in order to obtain disengagement of the head-piece from its housing, the user must operate voluntarily the locking slider and it is not conceivable, under any circumstances, that the head-piece might accidentally become detached due to simple bending or deformation of the toothbrush itself. Moreover, the elastomer mass, by exerting a significant elastic reaction, ensures that the assembly system is extremely safe against accidental disassembly and takes up any possible play which otherwise would occur during use. With the preferred method according to the invention, it is possible to manufacture a complex toothbrush, such as the toothbrush according to the invention, in an economical manner by means of simple successive co-moulding operations. It is understood, however, that the invention is not limited to the particular configurations which are illustrated above and which represent only non-limiting examples of the scope of the invention, but that numerous variants are possible, all within the reach of a person skilled in the art, without thereby departing from the scope of the said invention. In particular, the holding means (represented by the detent/groove pair 3b, 4a and detent/slider pair 4b, 7) have been shown arranged opposite each other at the two ends of the head, but it is conceivable that the slider may slide along the sidewall of the head-piece, locking the latter laterally cooperating with another detent/groove pair arranged on the opposite side. Obviously, the operative portions of the retaining elements, such as the detent or the ribs and the grooves, may have widely ranging forms, provided that they perform the function described above. For example, the locking end of the slider could be in the form a fork, if necessary having a width such as to embrace the two sides of the head-piece. Finally, the teachings of the invention may also be extended to a device for oral hygiene in which the head-piece is in the form of an insert provided with other working elements (for example a rubberized head-piece for massaging the gums).

Claims: Device for oral hygiene with an interchangeable head-piece of the type comprising a handle (1) and a housing head (3) inside which a replaceable insert (4), provided with working parts, can be locked by holding means, said holding means comprising at least one retaining element (4b) integral with the insert (4) and a locking element (7) slidable inside said handle and operable voluntarily between a locked position, in which a locking end (6) thereof is engaged with said retaining element (4b), and a disengaged position, characterized in that said slider is kept in the locked position by an elastic means and said disengaged position can be reached by overcoming the elastic reaction of said elastic means, said elastic means being a mass of elastic material which is arranged on the handle of said toothbrush and against which a thrusting portion of said slider bears. Device according to Claim 1, in which said locking element is a slider sliding inside a neck portion of said handle and has an actuating member emerging from said neck portion. Device according to Claim 2, in which said thrusting portion of the slider is a base end thereof and said mass of elastic material is contained inside said handle. Device according to Claim 2, in which said thrusting portion of the slider is said actuating member and said mass. of elastic material is contained in a sliding seat of said actuating member. Device according to any one of the preceding claims, in which said holding means also comprise a second retaining element which is arranged on said head-piece and can be engaged in a corresponding locating element in said housing head. Device according to any one of Claims 1 to 5, in which said retaining elements are in the form of grooves or detents, said locating element in the housing head being, respectively, a detent or a groove. Device according to any one of the preceding claims, in which a compressible elastic cushion means is also provided between said housing head and said insert. Device according to Claim 7, in which said elastic cushion means is provided in the vicinity of one side of the insert adjacent to the locking end of the slider. Device according to any one of the preceding claims, in which said insert has an extended pressure piece devoid of said working elements and able to be pressed by a finger on one hand so as to engage the insert into the housing head. Device according to Claim 2, in which said slider is made of a mouldable material incompatible with the material of the neck portion inside which it is slidable. . Device according to any one of the preceding claims, said device being a toothbrush and said working elements being tufts of bristles for cleaning the teeth. Method for manufacturing a device for oral hygiene which can be disassembled, characterized in that it comprises the following steps: moulding a first sliding component part of the device using a first material; moulding a second component part of the device on to and embracing at least partially said first part, using a second material incompatible with said first material. Method for manufacturing a device for oral hygiene which can be disassembled, characterized in that it comprises the following steps: moulding a first sliding component part of the device with a first material; moulding a second component part of the device on to and embracing at least partially said first part, using a second material after providing a releasing substance layer on the first part. Manufacturing method according to Claim 12 or 13, in which, at the end of the preceding steps, a filling or finishing mass of elastomer material is moulded.

Inventors: PONZINI ELIGIO, PONZINI, ELIGIO
Applicants: PONZINI SPA
Application year: 2000
Main classification: A46B7
IPC codes: A46B7