Cartridge-type dispenser

Abstract

A cartridge-type dispenser has a cartridge main body with a filling space, an extrusion nozzle on the front, and a piston slidably disposed in the filling space. The piston extrudes contents of the filling space from the extrusion nozzle by applying a push-in force. The piston includes a trunk portion having an outer circumferential wall running along an inner wall of the main body with a gap therebetween, a front wall on one end of the trunk portion directly contacting the contents of the filling space, and a rear wall on the other end whereon a rod of a push-in tool applies the push-in force on the piston. On the outer circumferential wall of the trunk portion, protrusions are provided, which contact the inner circumferential wall of the main body. The points of contact form sliding parts of the piston but do not seal the main body interior.

1 . A cartridge-type dispenser comprising: a cartridge main body defining a filling space for contents and provided with an extrusion nozzle at a front end portion of the cartridge main body; and a piston slidably arranged in the filling space of the cartridge main body and configured to cause the contents of the filling space to be extruded from an end of the extrusion nozzle in response to application of a push-in force, wherein:
 the piston includes (i) a trunk portion having an outer circumferential wall arranged opposite to an inner circumferential wall of the cartridge main body so as to define a gap therebetween, (ii) a front end wall portion provided at one end portion of the trunk portion in direct contact with the contents of the filling space, and (iii) a rear end wall portion provided at another end portion of the trunk portion to be pressed with a rod of a push-in tool for application of the push-in force to the piston; and   the outer circumferential wall of the trunk portion is provided with a protrusion, which is in contact with the inner circumferential wall of the cartridge main body to form a sliding part of the piston without sealing off an interior of the cartridge main body.   
     
     
         2 . The cartridge-type dispenser of  claim 1 , wherein the trunk portion of the piston has an hourglass shape having a reduced diameter at a middle portion thereof in a push-in direction of the piston. 
     
     
         3 . The cartridge-type dispenser of  claim 1 , which satisfies the following conditions:
     X−D   1 ≦1 mm; and
       X−D   2 ≦1 mm
   wherein D 1  and D 2  represent, respectively, dimensions at one end portion and the other end portion of the trunk portion of the piston, and X represents an inner dimension of the cartridge main body.   
     
     
         4 . The cartridge-type dispenser of  claim 1 , which satisfies the following conditions:
     D   3   −X≧ 0.01 mm; and       D   4   −X≧ 0.01 mm   wherein D 3  and D 4  represent, respectively, dimensions at one end portion and the other end portion of the trunk portion of the piston, inclusive of the protrusion, and X represents an inner dimension of the cartridge main body.   
     
     
         5 . The cartridge-type dispenser of  claim 1 , which satisfies the following conditions:
     X−D   1 ≦1 mm;
       X−D   2 ≦1 mm;
       D   3   −X≧ 0.01 mm; and       D   4   −X≧ 0.01 mm, wherein   D 1  and D 2  represent, respectively, dimensions at one end portion and the other end portion of the trunk portion of the piston;   D 3  and D 4  represent, respectively, dimensions at one end portion and the other end portion of the trunk portion of the piston, inclusive of the protrusion; and   X represents an inner dimension of the cartridge main body.