received by the International Bureau on 22 January 2018 (22.01.2018)

I Claim:

1. A pump unit comprising an outer part (17) and an inner part (16) arranged so as to

form a cavity, the pump unit further comprising a top element (18), said top

element (18) sealing the cavity and comprising a piston wall (5a) extending in the cavity sealingly between opposite ends of the cavity,

the outer part (17) comprising at least a first inlet (6) and a first outlet (9),

the top element (18) being arranged to perform a scrolling movement whereby the inner part (16) is caused to slide back and forth in a first dimension relative to the outer part (17) and the piston wall (5a) is caused to slide in a second dimension substantially perpendicular to the sliding movement of the inner part (16), in such a way that a first and a second chamber are formed in the cavity, separated by the piston wall (5a), the first chamber comprising the first inlet (6) and the first outlet (7), in such a way that the sliding of the inner part (16) will cause the first inlet (6) and the first outlet (7) to be alternatingly closed and exposed by the inner part

(16), to achieve a pumping effect from the first inlet (6) to the first outlet (7).

2. A pump unit according to claim 1 , wherein,

• Either the outer part (17) or the inner part (16) comprising a first side wall (4al)

forming a first side of the cavity, and

• Either the outer part (17) or the inner part (16) comprising a second side wall

(4a2) forming a second side of the cavity opposite the first side, and

• Either the outer part (17) or the inner part (16) comprising a bottom element

(12) forming a bottom wall of the cavity, and

• The outer part (17) comprising either the bottom element (12), the first and

second side walls (4al, 4a2), or both, and

• the inner part (16) comprising a first and a second end stop (3al, 3a2) extending between the side walls (4al, 4a2), forming opposite ends of the cavity, and

the scrolling movement causing the inner part (16) to slide parallel to the first and second side walls (4al, 4a2), and the piston wall (5a) is caused to slide

33 between the side walls (4al, 4a2), parallel to the extension of the end stops (3al, 3a2),

3. A pump unit according to claim 1, wherein an element of the outer part (17)

further comprises a second inlet (8) and a second outlet (9) in the second chamber, and the sliding of the inner part (16) will also cause the second inlet (8) and the second outlet (9) to be alternatingly closed and exposed to achieve a pumping effect from the second inlet (8) to the second outlet (9), respectively.

4. A pump unit according to claim 1 or 2, wherein the outer part (17) comprises the first and second side wall (4a 1, 4a2) and the first inlet (6) and outlet (7), and the second inlet (8) and outlet, if present, are arranged in the first and second side walls (4a 1, 4a2), respectively.

5. A pump unit according to any one of the preceding claims, wherein the outer part (17) comprises the bottom element (12) and the first inlet (6) and outlet (7) are arranged in the bottom element (12) near the first side wall and the second inlet (8) and outlet (9) are arranged in the bottom element (12) near the second side wall (4al, 4a2).

6. A pump unit according to any one of the preceding claims, wherein the inner part (16) comprises a box formed by the first and the second side wall (4al, 4a2), first and second end stops (3al, 3a2) and a frame bottom (13a), and the outer part (17) comprises a bottom element (12) on which the frame bottom (13a) can slide.

7. A pump unit according to claim 5, wherein the first and second side walls (4al , 4a2) are arranged on the inner part (16) and the outer part (17) further comprises a first and a second outer side wall arranged outside of the first (4al) and second side wall (4a2), respectively.

8. A pump unit according to any one of the claims 1 - 4, wherein the inner part (16) comprises the first and second end stops (3al, 3a2) and the outer part (17) comprises the first (4al) and second (4a2) side walls and the frame bottom (13a), the inlets and outlets and the end stops (3al, 3a2) being arranged so that the end stops (3al, 3a2) will alternatingly expose and close the inlets and the outlets, respectively.

9. A pump unit according to any one of the preceding claims, wherein at least one inlet and/or one outlet comprises a number of holes.

10. A pump unit according to any one of the preceding claims, wherein either the inner part (16) of the outer part (17) comprises support elements, or skids to reduce the friction between the inner part (16) and the outer part (17).

11. A pump unit according to claim 9, wherein the inner part (16) comprises a frame bottom (13a) and the outer part (17) comprises the bottom element (12) on which the frame bottom (13a) can slide, and either the frame bottom (13a) or the bottom element (12) comprises support elements, or skids to reduce the friction between the frame bottom (13a) and the bottom element (12).

12. A pump unit according to any one of the preceding claims, further comprising at least one wheel arranged so as to reduce friction between the outer part (17) and the inner part (16).

13. A pumping device comprising at least a first and a second pump unit according to any one of the claims 1 - 9, at least an outlet of the first pump unit being connected to an inlet of the second pump unit.

14. A pumping device according to claim 10, wherein a common top element (18) is used for both or all pump units, the top element (18) comprising one piston wall (5a) for each pump unit.

15. A pumping device comprising a first series of pump units and a second series of pump units, each pump unit being a pump unit according to any one of the claims 1 - 9, said first and second series being interconnected to achieve a compression or an expansion.