Extrusion apparatus and method for extruding abrasive pastes

Claim 1

An extrusion apparatus including a piston and cylinder; said cylinder having a bore generally complementary to said piston and leading at its inner end to an external orifice, said bore having a side-wall, and operating means associated with said piston for causing paste-like material to be compressed within said bore and extruded through said external orifice; wherein the improvement consists essentially of a lining system for said cylinder comprising a tubular liner, a first replaceable disc, and a second replaceable disc, said liner and first and second discs each composed of plastics material selected from the group consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon; said tubular liner formed as a thin sheet and having appropriate dimensions and resilience so as to assume an essentially tubular form without overlap when inserted into said bore, closely fitting against and substantially covering said side-wall of said bore; said first replaceable disc substantially closing the end of said liner nearest said external orifice and defining a central hole having a diameter not larger than the diameter of said orifice; and said second replaceable disc substantially closing the other end of said liner, and shaped so that it is capable of slidable movement within the space enclosed by said liner under the influence of said piston and said operating means, so that said extrusion apparatus is useful for extruding dental filling compositions or like abrasive paste-like materials.

Claim 6

A method of extruding an abrasive paste-like dental filling composition utilizing an extrusion apparatus comprising a piston and cylinder, the cylinder having a bore generally complementary to the piston and leading at its inner end to an external orifice, and an operating device for the piston; said method comprising the steps of (a) preventing frictional wear occuring to the piston and the bore during utilization thereof by (i) cutting a rectangular thin sheet composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, to size to form a sheet liner, and inserting into the bore the thin sheet liner so that it assumes a tubular form without overlap, closely fitting against and substantially covering the side-wall of the bore; (ii) inserting into the bore a first replaceable disc having a central opening and composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, so that the first disc closes the end of the liner nearest the external orifice with the central opening therein in-line with the orifice, and having a diameter no larger than the diameter of the orifice; and (iii) inserting into the bore a second replaceable disc composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, so that the second disc is capable of slidable movement within the space enclosed by the liner; (b) moving the piston with the operating device to extrude the filling composition from between the first and second discs and liner through the orifice; and (c) replacing the tubular liner and first and second discs when they become worn.

Claim 7

A method of extruding an abrasive paste-like dental filling composition utilizing an extrusion apparatus comprising a piston and cylinder, the cylinder having a bore generally complementary to the piston and leading at its inner end to an external orifice, and an operating device for the piston; said method comprising the steps of (a) preventing frictional wear occuring to the piston and the bore during utilization thereof by (i) cutting a rectangular thin sheet composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, to size to form a sheet liner, and inserting into the bore the thin sheet liner so that it assumes a tubular form without overlap, closely fitting against and substantially covering the side-wall of the bore; (ii) inserting into the bore a first replaceable disc having a central opening and composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, so that the first disc closes the end of the liner nearest the external orifice with the central opening therein in-line with the orifice, and having a diameter no larger than the diameter of the orifice; and (iii) inserting into the bore a second replaceable disc composed of a material consisting essentially of polypropylene, polytetrafluoroethylene, high density polyethylene, and nylon, so that the second disc is capable of slidable movement within the space enclosed by the liner; (b) moving the piston with the operating device to extrude the filling composition from between the first and second discs and liner through the orifice; and (c) replacing the tubular liner and first and second discs when they become worn.