DELIVERY DEVICE

1 . A delivery device for delivering a fluid drug, comprising:

a housing comprising a reservoir module and a drive module configured to be detachably connected;

a reservoir configured with a variable internal volume for storing the fluid drug, wherein the reservoir is at least partially arranged in the reservoir module of the housing;

a drive device at least partially arranged in the drive module of the housing, the drive module comprising:

a drive, the drive comprising a motor or a spring; and

a movable piston rod mounted in the housing and configured to be movable by the drive to change the variable internal volume of reservoir,

wherein the piston rod is configured to be guided via an aperture through at least one of an inner wall of the housing, an outer wall of the reservoir module, or an outer wall of the drive module,

wherein the piston rod is displaceably and non-rotationally mounted in the aperture,

wherein a bearing surface between the piston rod and the aperture comprises an elastically deformable seal configured to prevent liquid from passing through the aperture while permitting displacement of the piston rod, and

wherein a shape of a circumference of a cross-section of the piston rod is approximately a non-trivial curve of constant width.

2 . The delivery device according to claim 1 , wherein the curve of constant width is a curve of constant width with three or more corners.

3 . The delivery device according to claim 2 , wherein the curve of constant width comprises five corners or seven corners.

4 . The delivery device according to claim 1 , wherein the curve of constant width is a curve of constant width with rounded corners.

5 . The delivery device according to claim 1 , wherein a housing of the reservoir module and a housing of the drive module are configured to be detachably connectable to each other, wherein at least a portion of the housing of the drive module is constructed of a two-component injection molded material in an area of the outer wall comprising the aperture, wherein a material of a first component defining the outer wall differs from a material of a second component defining the seal.

6 . The delivery device according to claim 5 , wherein the material of the second component is a thermoplastic elastomer.

7 . The delivery device according to claim 6 , wherein the thermoplastic elastomer comprises at least one of a thermoplastic polyurethane or a thermoplastic polyamide.

8 . The delivery device according to claim 5 , wherein the material of the second component is a silicone.

9 . The delivery device according to claim 5 , wherein a region of the outer wall comprising the aperture comprises at least one additional aperture comprising at least one additional seal, and wherein the at least one additional seal is constructed of the material of the second component of the two-component injection molded material.

10 . The delivery device according to claim 9 , wherein a seal component defines the seal and the at least one additional seal, wherein the seal and the at least one additional seal are coupled by at least one arm of the seal component.

11 . The delivery device according to claim 9 , wherein the at least one additional aperture is configured as an aperture for at least one of an operating element or for one or more electrical contacts.

12 . The delivery device according to claim 1 , wherein the delivery device is an infusion pump.

13 . The delivery device according to claim 12 , wherein the infusion pump is a patch pump.

14 . The delivery device according to claim 1 , wherein the delivery device is an injection device.

15 . The delivery device according to claim 14 , wherein the injection device is a pen-shaped injection device.