Piston Rod Foot

• US 20130267895A1
• Filed: 06/17/2011
• Published: 10/10/2013
• Est. Priority Date: 07/13/2010
• Status: Abandoned Application

• Current Assignee: Novo Nordisk A/S
• Original Assignee: Novo Nordisk A/S
• Inventors: Hemmingsen, Hans
• Application Number:
  US13/809,542
• Publication Number:
  US 20130267895A1
• Time in Patent Office: Days
• US Class Current: 604/93.01
• CPC Class Codes: A61M 2005/3151 by friction
• CPC Class Codes: A61M 5/24 Ampoule syringes, i.e. syringes with needle for use in combination with replaceable ampoules or carpules, e.g. automatic ampoules or carpules A61J1/06
• CPC Class Codes: A61M 5/31511 Piston or piston-rod constructions, e.g. connection of piston with piston-rod A61M5/5066 takes precedence
• CPC Class Codes: A61M 5/31513 Piston constructions to improve sealing or sliding
• CPC Class Codes: A61M 5/31515 Connection of piston with piston rod

Abstract

The invention relates to a medical drug delivery apparatus which comprises a cartridge (1) being closed at one end by a flexible membrane (2) and at the opposite end by a movable piston (10). The movable piston rod (19) is moved forward by a piston rod (20). In order to distribute the force from the piston rod (20) to the movable piston (10) a piston rod foot (30) is provided sandwiched between the piston rod (29) and the movable piston (10) The piston rod foot (30) provided between the piston rod (20) and the movable piston (10) has a plurality of arms (34) extending in a direction perpendicular to a longitudinal axis (X) of the cartridge (1) and which arms (34) engages the inner wall (4) of the cartridge (1) thereby obtaining geometric guidance or generating a force of friction between the piston rod foot (30) and the inner wall (4) of the cartridge (1).

Claims

1. A medical drug delivery apparatus for delivering a liquid drug, comprising

A cartridge (1) containing the liquid drug to be delivered, the cartridge (1) comprising a distal end and a proximal end connected by an inner wall (4) forming a space (12) containing the liquid drug, the distal end being closed by a flexible membrane (2), and the proximal end being closed by a movable piston (10) having a front-wall (11) and a back-wall (13), and which piston (10) can be moved inside the cartridge (1) by a piston rod (20) thereby decreasing the variable space (12) between the flexible membrane (2) and a front wall (11) of the piston (10), and

A piston rod foot (30) provided between the piston rod (20) and the piston (10), the piston rod foot (30) having a distal surface (32) for abutting the back-wall (13) of the piston (10) and a proximal surface (31) abutting the piston rod (20),

Characterized in that, the piston rod foot (30) has a number of arms (34) extending in a direction perpendicular to a longitudinal axis (X) of the cartridge (1) and which arms (34) engages the inner wall (4) of the cartridge (1).

2. A medical drug delivery apparatus according to claim 1, characterized in that, the piston rod foot (3) has an outer surface (33) with a diameter smaller than the diameter of the inner wall (4) of the cartridge (1).

3. A medical drug delivery apparatus according to claim 1, characterized in that, a peripheral circle drawn tangential to the arms (34) has a diameter substantial identical to the diameter of the inner wall (5) of the cartridge (1) thereby obtaining geometric guidance of the piston rod foot (30) against the inner wall of the cartridge (1).

4. A medical drug delivery apparatus according to claim 1, a peripheral circle drawn tangential to the arms (34) has a diameter larger than the diameter of the inner wall (5) of the cartridge (1) thereby generating a force of friction between the piston rod foot (30) and the inner wall (4) of the cartridge (1).

5. A medical drug delivery apparatus according to claim 1, characterized in that, the arms (34) have a width substantially equal to the width of the outer surface (33) of the piston rod foot (3).

6. A medical drug delivery apparatus according to claim 1, characterized in that the arms (34) are resilient.