Abstract:
An all plastic pump for liquids has an elastic bellows in the shape of a spiral incorporates an integral spring. The turns of the bellows are arranged with contracted areas of the spiral formed with a protruding stiffening rib and sidewalls having a convex outwardly projection region.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application No. 08/455,499 filed May 31, 1995 U.S. Pat. No. 5,673,824. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention concerns an all plastic pump particularly suitable for dispensing liquid or thick substances from containers. 
     As it is known, dispensing pumps are widely used for dosing and dispensing liquid or creamy substances, such as soaps, cosmetic creams, detergents and similar. Said pumps are applied to the container which holds said substances. 
     The majority of the pumps used at present are made of both plastic materials and metal, the latter being mostly used for the return spring of the piston which forms the pump. 
     The presence of such metal materials entails some problems for recycling. In fact, should the pump be completely made of plastic materials, even differing from each other but being mutually compatible, it is possible to entirely recover the material the pump is made of, by shredding the pump directly. On the other hand, the presence of materials which are heterogeneous in relation to each other and, in particular, the presence of metal materials, prevents such a direct shredding and requires, for an eventual recycling of the plastic material, a previous separation of the metal parts. The difficulty and the costs related to such a sorting operation imply that the dispensing pumps, once they are no longer useful, are eliminated as a waste, with the inconvenience of wasting plastic material which could be recovered and of increasing the amount of non-degradable materials present among the waste. 
     Pumps are also known which, rather than using a spring made of metal material, use a bellows, as an elastic element made of plastic material obtained by a blow moulding process. 
     Said bellows element consists of a plurality of essentially toroidal elements, placed one on the other, so that the profile of the bellows, in a cross-section, presents itself as a series of expansions and contractions arranged on horizontal planes and essentially parallel in relation to each other. 
     Said type of profile can only be realized by blow moulding, because it is impossible to remove the snapping tool from the bellows after the moulding, and, therefore, its realization with the injection moulding process is not possible. The possibility for the bellows to be realized by injection moulding process rather than by blow moulding, would yield a number of advantages, one of which is the reduction of the production costs, since injection moulding is quicker than blow moulding. 
     Apart for this fact, the moulding of the bellows by injection would permit to obtain a thicker profile in the bending points which undergo a greater stress and, therefore, it would permit to realize a bellows having a higher mechanical resistance. 
     The realization of a bellows made of plastic material is known from the Belgian patent 718118. Said patent describes a bellows used in the field of distribution valves for the protection of the sliding elements of the valves themselves. The bellows realized according to the dictates of the mentioned patent presents its lateral surface in the shape of a spiral, so as to obtain the bellows by injection moulding since the spiral profile permits the removal of the snapping tool. 
     The bellows of this type present one profile of the spiral in their longitudinal section, which is not essentially symmetrical in relation to the plane of inclination of the spiral itself, so that they have a limited resistance when they undergo a pressing force because of the action of an axial stress which turns into a smaller build-up of elastic power and, therefore, into a weaker elastic return when they are released. 
     It easy to understand that such a fact consitutes a negative factor for the use of said bellows in the range of the pumps for dosing elements, wherein it is necessary to have forces presenting a rather consistent elastic return, since the piston of the pump, once it has gone back to its resting position after the dispensing action has been completed, must suck back the liquid in order to prearrange the pump for the next dispensing operation. 
     SUMMARY OF THE INVENTION 
     The present invention proposes to overcome such limitations. 
     In particular, one of the purposes of the invention is to realize a pump made of plastic for dispensing liquid or creamy substances from containers, wherein the elastic element, which ensures the return of the piston into its resting position, is an elastic bellows presenting a higher elastic coefficient against the axial pressure, as compared to elastic bellows belonging to the known technique and equivalent with it. 
     Another purpose is for the elastic bellows which realizes said pump to be complete with a higher elastic return as compared with equivalent bellows belonging to the known technique. 
     Further purpose of the invention is to realize the elastic return of the bellow without using materials different from those ones used for making the bellow. The described purposes are achieved by a pump for dosing liquids to be applied to a container which, in accordance with the main claim comprises: 
     a cylindrical chamber communicating with said container through a feeding hole and suited to receive said liquid to be dispensed held inside said container; 
     at least one piston axially sliding within said cylindrical chamber and provided internally with a tubular chamber; 
     retaining valvular means; 
     at least one elastic bellows made of plastic material and having its lateral surface in the shape of a spiral suited to ensure the return, by elastic recovery, of said pistons in their resting positions once the dispensing has occurred, and is characterized in that said elastic bellows incorporates a spring realized in a single piece with the bellows itself, the turns of which are arranged in correspondence with the contraction areas of the spiral which forms the lateral surface of the bellows, where the thickness of said turns are suited to realize a protruding stiffening rib in respect of the external surface of the spiral. 
     According to one preferred embodiment, the spiral which forms the lateral surface of the bellows presents, in its longitudinal section, the walls having a symmetrical profile in relation to the axis of inclination of the spiral itself. 
     According to one embodiment, the bellows presents a cylindrical profile. 
     According to another embodiment, the bellows presents a profile in the shape of a truncated-cone. 
     Advantageously, the presence of the spring realized in a single piece with the bellows, yields a higher elasticity to the bellows itself and also gives it a greater mechanical resistance. 
     Moreover, with advantage, the manufacturing of the spiral which forms the lateral surface of the bellows, which is symmetrical in relation to the axis of inclination of the spiral itself, permits to obtain a considerable elastic recovery of the bellows whenever the pump is released after the dosing. 
     With as much advantage, the spiral profile allows the realization of the bellows by injection moulding and permits to increase the thickness of the spiral in correspondence with the bending areas where there is a greater stress. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     However, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description and from the drawings, wherein: 
     FIG. 1 shows in a perspective view the pump according to the invention; 
     FIG. 2 shows a longitudinal section of the pump according to the invention; 
     FIG. 3 shows the suction pump of FIG. 2 during the dispensing phase; 
     FIG. 4 shows in a cross-section the bellows of the pump according to the invention, presenting a cone-shaped profile; 
     FIG. 5 shows a no-cutaway lateral view of the bellows of FIG. 4; 
     FIG. 6 shows in a cross-section a different embodiment of the bellows belonging to the pump according to the invention and realized with a cylindrical profile; 
     FIG. 7 shows a no-cutaway lateral view of the bellows of FIG. 6; 
     FIG. 8 shows in a cross-section the enlarged profile of the spiral which forms the lateral surface of the bellows belonging to the pump according to the invention. 
     FIGS. 9 and 10 illustrate fragmentary cross-sectional elevations of another embodiment of the invention in which the pump is shown at rest and in the dispensing position respectively. 
    
    
     DESCRIPTION OF THE INVENTION 
     The pump according to the invention is represented in FIG. 1, wherein is indicated as a whole with 1, and it can be observed that it comprises a cylindrical collar 11, to the lower part of which a cylindrical chamber 13 is connected, while an elastic bellows 40 is attached to its upper part. The cylindrical chamber 13 is inserted into the neck of a container, not represented in the drawing, which contains the product to be dispensed and the cylindrical collar 11 is tightened on the neck of the container itself. A dispensing element 10, provided with a dispensing inner channel 21, is connected to the upper part of the elastic bellows 40, as can also be observed in FIG. 2, and permits the dispensing of the product held in the container. 
     In FIG. 2 it can be observed that the dispensing element 10 is connected to the tubular body 121 of a first piston 12 which slides inside said cylindrical chamber 13 communicating with the container to which the pump is connected through a feeding hole 14 drilled at the bottom 130 of said cylindrical chamber 13. 
     Inside said tubular body 121 a tubular chamber 160 is defined. 
     Stem 16 of a second piston 120 slides within said tubular chamber, said stem 16 being provided with first valvular elements consisting of a ball 22 suited to intercept duct 122 which sets into communication said tubular chamber 160 with said cylindrical chamber 13 and with second valvular elements consisting of a bevel 18 realized in the terminal part of said second piston 120. 
     Again in FIG. 2 it can be observed that on the opposite side of said duct 122 realized in said tubular body 121, there are third valvular means consisting of a ball 20 which intercepts the communication of said tubular chamber 160 with the dispensing channel 21 obtained in the dispensing element 10. 
     Finally, it can be observed that said dispensing element 10 is mechanically connected to said collar 11 by means of the interposition of said elastic bellows 40 which presents a first extremity 41 attached to said dispensing element 10 and a second extremity 42, opposite to the previous one, connected to said collar 11. Said bellows permits the mutual elastic movement of said dispensing element 10 and of said collar 11. 
     When the dispensing element 10 is pressed downward, it also drags downward the tubular body 121 to which it is connected, together with the first piston 12 which slides inside the cylindrical chamber 13. When said first piston 12 descends, it pushes downward said second piston 120, so that said second valvular elements 18 intercept the feeding hole 14. 
     When the dispensing element 10 is released, the elastic recovery of bellows 40 makes the first piston 12 slide upwards again, thus creating inside the cylindrical chamber 13 a depression and, therefore, a lifting of the second piston 120 because of the pressure of the liquid coming up from the container following direction 140 and which, through the feeding hole 14 and the holes 15 drilled in the second piston 120, fills the cylindrical chamber 13. 
     At this point, by pressing downward again the dispensing element, the first piston 12 descends together with the second piston 120, whose second valvular elements 18 intercept again the feeding hole 14. The descent of the first piston 12 compresses the liquid present in the chamber 13 which, as can be observed in FIG. 3, flows following direction 131 from the cylindrical chamber 13 into the tubular chamber 160 through duct 122, which is no longer obstructed by ball 22. The pression of the liquid inside said tubular chamber 160 lifts said first valvular means 20 and enters into the dispensing channel 21 from which it pours out. 
     Once the dispensing has been completed, the released of the dispensing element 10 permits the dispensing element 10 itself to slide back up into its resting position because of the action of the elastic recovery of bellows 40, thereby causing again the refill of the cylindrical chamber 13 with the liquid coming from the container. 
     The pump 1 is thus ready to perform a new dispensing action as soon as the dispensing element 10 is pressed downwards again. 
     It is important to observe that the elastic bellows 40 described and represented in the FIGS. 1, 2 and 3, is also represented in the FIGS. 4 and 5. It presents a tapered profile and its lateral surface, indicated as a whole with 50, has the shape of a spiral. More specifically, said spiral shape permits the realization of bellows 40 through injection moulding, since the spiral shape allows by rotation the extraction of the snapping tool once the bellows has been moulded. 
     As can be observed in the detail represented in FIG. 8, the elastic bellows 40 incorporates spring 63 which is obtained in a single piece together with the bellows and its turns are located in correspondence with the contraction areas of the spiral 80 which forms the lateral surface 50 of the bellows. 
     In particular, the spiral 80 presents, in its longitudinal section, an essentially symmetrical profile in relation to its axis 70 which is slanted in relation to the longitudinal axis 400 of bellows 40. The presence of such a spring 63, together with the essentially symmetrical profile of each spiral 80, is such as to allow the greatest build-up of elastic power during the pressing action. Said elastic power is released when the bellows elastically return into its resting position, once the axial force which has caused the pressing stops. 
     During the return of the dispensing element 10 into its resting position, this considerable amount of built-up elastic power permits a great suction of liquid which is transferred from the container into the cylindrical chamber 13 by means of the action of the first piston 12. 
     The possibility for the bellows to build-up and then release another amount of elastic power is further increased since, as can be observed in FIG. 8, the walls 60 of spiral 80 also present curved profiles 62 having an outward convexity, which make each spiral essentially acquire the shape of Belleville washers thus permitting a good axial force after the pressing action. 
     Therefore, with such a configuration of the elastic bellows 40, it is possible to obtain elastic returns having values which can be compared with those obtained by using metal springs, with the advantage of achieving, at the same time, the possibility of a complete and immediate recovery and recycling of the material which composes the pump. 
     In a different embodiment, as can be observed in the FIGS. 6 and 7, the bellows according to the invention, indicated as a whole with 500, can also be obtained with a cylindrical profile, yet maintaining the spiral 510 which forms its lateral surface 600, the symmetrical profile in relation to the axis of inclination 700 of the spiral and the same structure which incorporates the spring. 
     A different embodiment of the pump according to the invention is represented in the FIGS. 9 and 10 wherein it can be observed that said pump, indicated as a whole with 300, foresees a different embodiment of the pistons with which it is complete. In fact, it can be observed that, when the dispensing element 100 is pressed downwards, it also drags a first piston 320 connected with it, which presents internally a cylindrical chamber 321 and slides inside a cylindrical chamber 330 by means of the interposition of a second piston 360. Said first piston 320, during its downstroke, also drags the second piston 360 by means of the projections 421, so as to obstruct passage 240 by means of the valvular element consisting of ball 180. 
     When the dispensing element 100 is released, as a consequence of the elastic return of bellows 800, the first piston 320 and the second piston 360 also slide upwards. This creates a depression inside the cylindrical chamber 330. Said depression generates a suction of liquid from the container below which flows through passage 240 no longer obstructed by the valvular element 180 and which refills the cylindrical chamber 330. 
     By pressing down again dispenser 100 the liquid contained in the cylindrical chamber 330 is compressed and enters following direction 331 into the first piston 320 through opening 322 obtained in the first piston 320 which acts as a valvular element by co-operating with said second piston 360. The liquid then flows outwards through dispenser 100. 
     In this different embodiment, too, bellows 800 presents its lateral surface in the shape of a spiral so that it can be manufactured by injection moulding. Moreover, each of the folds which form the lateral surface of said bellows presents in a longitudinal cross-section a symmetrical profile in relation to the axis of inclination of the fold itself, so as to create a strong elastic return and, as a consequence, a great depression within chamber 330 when bellows 400 goes back to its resting position. 
     On the basis of what has been described, it is easy to understand that the pump according to the invention together with the described elastic bellows, reaches all the proposed purposes and also permits to obtain all the mentioned advantages. 
     It is obvious that the pump according to the invention can also be manufactured with different shapes and dimensions concerning, for instance, the dispensing element or the collar for its application on the container. The latter can also acquire any shape or dimension and can be used for more or less thick liquids. 
     All mentioned variations and others are to be considered as belonging to the scope of the present invention.