Dosing device comprising a medium reservoir and corresponding pump device

1. A dosing device having an outlet, comprising:

a cover element configured to mount to a medium reservoir, said cover element having an inlet passageway providing a pathway for medium from said medium reservoir, a finite length dosing chamber of uniform dimension connected in communication with said inlet passageway, said dosing chamber having at opposite ends a dimensional widening larger in dimension than said uniform dimension of said dosing chamber; and

a pump casing element mounted on said cover element and configured to move with respect thereto a defined dosing stroke length along a stroke axis, said pump casing element having an outlet chamber forming a passageway communicating with said outlet of said dosing device as well as being configured to communicate with said inlet passageway, said pump casing having an elongate plunger member longer than said finite length of said dosing chamber and having on at least a portion thereof a dimension that is conformed to said uniform dimension to operatively form a sliding piston relation with said finite length dosing chamber, said dimension of said sliding piston being less than each said dimensional widening, said sliding piston being oriented on said elongate plunger member so that at opposite ends of said stroke length, said sliding piston will be oriented beyond said uniform dimension of said dosing chamber so as to form an open passageway between said medium reservoir and said outlet chamber.

2. The dosing device according to claim 1 , wherein said cover element includes an annular reception space of a first volume encircling said dosing chamber, wherein said pump casing element includes an annular displacement body encircling said elongate plunger and has a second volume approximately equal to said first volume, said annular displacement body being configured to enter said annular reception space at a beginning of said dosing stroke and to occupy approximately all of said annular reception space when said sliding piston is at an end of said dosing stroke.

3. The dosing device according to claim 2 , wherein said inlet passageway, said dosing chamber and said annular displacement body of said cover element are integrally formed from the same material.

4. The dosing device according to claim 1 , wherein a pump spring is provided between said cover element and said pump casing element to facilitate a return of said pump casing element to a beginning position relative to said cover element.

5. The dosing device according to claim 1 , wherein said cover element includes an annular reception space of a first volume encircling said dosing chamber, wherein said pump casing element includes an annular displacement body encircling said elongate plunger and has a second volume approximately equal to said first volume, said annular displacement body being configured to enter said annular reception space at a beginning of said dosing stroke and to occupy approximately all of said annular reception space when said sliding piston is at an end of said dosing stroke, and wherein said cover element further includes a first annular space encircling said annular reception space and said pump casing element includes a second annular space encircling said annular displacement body, said first and second annular spaces being coaxial and housing therein said pump spring.

6. The dosing device according to claim 5 , wherein said pump spring is oriented remotely from said passageway between said medium reservoir and said outlet chamber.

7. The dosing device according to claim 1 , wherein said pump casing element includes a valve body oriented between said outlet chamber and said outlet of said dosing device and configured to move relative to said cover element between a first position closing the passageway between said outlet chamber and said outlet of said dosing device and a second open position, a return spring for continually urging said valve body to said second closed position.

8. The dosing device according to claim 7 , wherein said pump casing element includes a valve chamber open at one end and closed at the other end and in which said valve body is reciprocally provided, said return spring being provided between said valve body and said closed end of said valve chamber for continually urging said valve body toward and into engagement with a valve seat provided adjacent said open end of said valve chamber.

9. The dosing device according to claim 7 , wherein said return spring is oriented remotely from said passageway between said medium reservoir and said outlet of said dosing device.

10. The dosing device according to claim 2 , wherein said outlet chamber is configured to communicate with inlet passageway through said dosing chamber during intervals that said sliding piston is oriented at said opposite ends of said stroke length.

11. The dosing device according to claim 10 , wherein said annular displacement body sealingly slidingly engages a wall of said annular reception space so that as said annular displacement body is moved out of said annular reception space, a vacuum will be created in a region vacated by said annular displacement body such that when the sliding piston becomes oriented at said beginning of said dosing stroke, said vacuum will draw medium from said dosing chamber into said annular reception space.

12. The dosing device according to claim 11 , wherein said annular displacement body and said annular reception space are additionally configured to urge medium out of said annular reception space in response to a movement of said annular displacement body into said annular reception space and a simultaneous movement of said sliding piston through said dosing chamber, said conformance of said dimensions of said sliding piston and said dosing chamber preventing the flow of medium therebetween.