Patent Publication Number: US-2010125962-A1

Title: Toothbrush with metal skeleton and plastic body moulded around it

Description:
The present invention relates to a toothbrush having a moulded plastic body and a metal skeleton. 
     Despite the prior art there remains a need for toothbrushes which are capable of providing improved cleaning. 
     Accordingly, the present invention provides a toothbrush according to claim  1 . 
     The metal skeleton extends from the handle, through the neck and into the head of the toothbrush. The metal skeleton provides the necessary strength to the toothbrush neck without significantly contributing to the neck&#39;s volume such that it is now possible to brush the back teeth efficiently since the oral cavity is less likely to be filled with the toothbrush. This allows the user to properly manipulate the toothbrush as he would when brushing the front teeth. 
     Preferably, the skeleton comprises no more than 30% by area, more preferably no more than 25% and especially no more than 20% by area of the toothbrush in any cross section in a 0.5 cm long section of the neck of the toothbrush and transverse to the longitudinal axis of the toothbrush. The 0.5 cm long section must begin and end in the neck of the toothbrush. The neck is considered to begin at the junction with the head and end at the beginning of the thumb grip of the toothbrush. 
     Preferably, the metal skeleton is wholly contained within the plastic body. 
     Preferably, the metal skeleton extends for at least 50% of the length of the toothbrush, more preferably at least 75% and most preferably at least 90% of the length of the toothbrush. 
     Preferably, the plastic body comprises transparent or translucent material. By this is meant that at least part of the skeleton is discernable through the plastic body. More preferably, at least 50% and especially preferably at least 80% of the surface of the skeleton is visually discernable through the plastic body. 
     Preferably, the head comprises a plastic body part, a head skeleton part and a bristle bearing part. Preferably, at least one, more preferably two and more preferably all three parts are layered. 
     Preferably, the head skeleton part comprises a flattened portion in the head of the toothbrush. More preferably, the external dimensions of the flattened portion mirror the external dimensions of the head of the toothbrush. Such a structure offers improved support to the toothbrush head by presenting a greater surface area on which to bear pressure during toothbrushing. 
     Preferably, the skeleton in the head is shaped to correspond to the external dimensions of the outer shape of the head. This provides improved support to the neck during brushing since the pressure applied to the head is borne by a relatively large surface area and not by a mere wire or prong into the neck. Preferably the skeleton in the head is apertured. An apertured skeleton in the head part of the toothbrush provides improved bonding between the plastic body and the remainder of the head. 
     Preferably, the head comprises a plate which supports the bristles. Preferably, the plate is distinct from the remainder of the head. More preferably, the bristles are fixed through holes in and pass through the plate. 
     Preferably, the bristles are welded together into tufts at their base ends. 
     Preferably, the bristles are gathered into tufts, passed through holes in the plate and welded at their base ends thus fixing them into the plate. The plate is then moulded onto the remainder of the brush. 
     Preferably, the skeleton comprises a receiving means for receiving and maintaining the plate in position. This improves the overall structural integrity of the toothbrush head since it minimizes the chances of the plate rocking during moulding the plastic body around the plate and skeleton. Preferably, the receiving means is a groove or channel. 
     Preferably, the skeleton comprises a groove running along part of its length. The groove provides a channel along which the plastic forming the plastic body courses during injection moulding. This reduces the need for multiple injection points on the brush. Preferably, the groove runs on the underside of the toothbrush. The underside of the brush is the opposite side to the bristle bearing side. 
     Preferably, the toothbrush according to the invention comprises a metal skeleton. Preferably the metal comprises a zinc alloy. Preferably, the zinc alloy is zama alloy. 
     Preferably, the plastic body comprises acrylonitrile butadiene styrene (ABS) or BR. ABS and BR provide the optimum strength with flexibility when surrounding a metal skeleton. 
     Preferably, the toothbrush according to the invention has a transverse cross sectional area ratio between the skeleton and the total brush ranges from 1:7 to 1:3, preferably from 1:4 to 1:6 along at least a 1 cm length of the neck. More preferably the transverse cross sectional area ratio between the skeleton and the total brush ranges from 1:7 to 1:3, preferably from 1:4 to 1:6 along at least a 2 cm length of the neck, most preferably a 3 cm length of the neck. The level of metal in the neck of the toothbrush is beneficial in achieving the objective of improved reach to the back teeth of the brush. 
    
    
     
       Embodiments of the invention will now be described with reference to the following non-limiting figures in which: 
         FIG. 1  is a plan view of a skeleton for a toothbrush according to the invention; 
         FIG. 2  is a cross section of the skeleton depicted in  FIG. 1  at section A-A; 
         FIG. 3  is a cross section of the skeleton depicted in  FIG. 1  at section B-B; 
         FIG. 4  is a plan view of the skeleton of  FIG. 1  in a toothbrush according to the invention; 
         FIG. 5  is a side view of the head of a toothbrush according to the invention; and 
         FIG. 6  is a side view of a bristle plate. 
     
    
    
     In detail,  FIG. 1  shows a skeleton ( 1 ) for a toothbrush according to the invention. The skeleton ( 1 ) has a handle part ( 2 ), a neck part ( 3 ) and a head part ( 4 ). The head part has a perimeter ( 5 ) which corresponds to the shape of the toothbrush head (not shown). 
       FIG. 2  is a cross sectional view along A-A of  FIG. 1  and shows a groove ( 6 ) on the underside of the skeleton. 
       FIG. 3  is a cross sectional view along B-B of  FIG. 1  and shows a groove ( 6 ) on the underside of the skeleton. 
       FIG. 4  is a plan view of the toothbrush in which the skeleton depicted in  FIG. 1  is employed. The toothbrush has a handle ( 8 ) which extends from the distal end of the brush towards the head up to the end of the thumb grip, a neck portion ( 9 ) which extends from the end of the thumb grip ( 11 ) to the beginning of the head and a head portion ( 10 ) which extends from the neck portion to the tip of the brush. 
       FIG. 5  is a side view of a brush head (bristles not shown). The head shows the plastic body ( 12 ) which provides the underside surface of the toothbrush head, the skeleton ( 4 ), upon which is mounted the plate ( 13 ) for bearing bristles. 
       FIG. 6  shows a plate with bristles mounted therein and projecting through the plate to an underside thereof where the bristles are held in place by welding their ends together.