[0001] The invention relates to a pump comprising a cylindrical pump chamber provided with end walls and, arranged in the pump chamber, an inlet opening for a suction pipe and an outlet opening for an exhaust pipe.

[0002] It is an object of the invention to achieve an above- mentioned pump with a simple structure and therefore low manufacturing costs, which also has low friction, consumes little energy and is suitable for pumping fluid, gas and sludge, for instance.

[0003] This object is achieved with a pump of the invention, which is characterized in that a rotatable pump shaft is arranged in the pump chamber coaxially to the central axis of the pump chamber and at least one protrusion is arranged to protrude from the pump shaft, that the pump shaft and said at least one protrusion protruding from it are arranged inside a hose-like element, the opposite ends of the hose-like element being arranged to rest against the end walls of the pump chamber and the hose-like element and the cylindrical inner surface of the pump chamber being, in the region between the end walls of the pump chamber, attached to each other between the inlet opening for the suction pipe and the outlet opening for the exhaust pipe so that pumping material is not allowed to flow between the hose-like element and the cylindrical inner surface of the pump chamber at the location of the attachment, and that the hose-like element is dimensioned so that while the pump shaft is rotating, the protrusion or protrusions change the cross-sectional shape of the coating surface of the hose-like element.

[0004] In a preferred embodiment of the invention, the distance between the cylindrical inner surface of the pump chamber and the free end of the protrusion is arranged to be smaller than or as big as the wall thickness of the hose-like element. Because of this arrangement, pressure losses of pumping material driven by the protrusion remain small, since no flow can exist between the cylindrical inner surface of the pump chamber and the free end of the protrusion.

[0005] According to the invention, it is particularly advantageous if a rotating support element is arranged at the free end of the protrusion. In this case, also the frictional forces remain small and less energy is required for operating the pump.

[0006] Although the pump of the invention operates with one protrusion, a preferable embodiment of the invention is implemented such that

at least two protrusions are arranged to protrude from the pump shaft at regular intervals. Thus, forces directed to the pump shaft are more balanced and the pump power per one pump shaft cycle increases.

[0007] According to the invention, it is furthermore arranged that the inlet opening for the suction pipe and the outlet opening for the exhaust pipe divide the cylindrical inner surface of the pump chamber in the circumferential direction of the pump chamber into two parts of different sizes, the shorter part being attached with the hose-like element. It is preferable to arrange said shorter part as short as possible, yet long enough to allow the hose-like element to be connected thereto.

[0008] According to the invention, it is also arranged that the hose- like element is formed of a flexible material substantially inelastic in the circumferential direction, most suitably of rubber, plastic, steel or a combination thereof.

[0009] In yet another preferred embodiment of the invention, it is arranged that the protrusion is dimensioned such that the path of the end surface of the hose-like element is outside the opening made to the end wall of the pump chamber for the pump shaft. Due to this solution, the end of the hose-like element can always rest against the uniform and even end wall of the pump chamber, whereby the wear of the end of the hose-like element remains very low.

[0010] In the following the invention will be described in more detail with reference to the attached drawing, in which Figure 1 shows a schematic end view of a pump with a removed front end wall according to a preferred embodiment of the invention, Figure 2 shows a section along the line 11-II of Figure 1.

[0011] A self-sucking pump is shown as a schematic end view with a removed front end wall 2 in Figure 1 and in section in Figure 2.

[0012] The pump comprises a cylindrical pump chamber 1 provided with end walls 2,3, and an inlet opening 6 for a suction pipe 4 and an outlet opening 7 for an exhaust pipe 5, which are arranged on a cylindrical inner surface 14 of the pump chamber 1 or on an end wall 2,3. In the example of the drawing, the end wall 3 forms a fixed part of the pump chamber 1. The end wall 2, for its part, is arranged to be detachable, and thus it can be attached to the pump chamber 1 by means of screw connections 23, for instance.

[0013] The pump chamber 1 having, in the solution of the invention,

the shape of a circular cylinder, is provided with a rotatable pump shaft 8 which is arranged coaxially to the central axis 9 of the pump chamber 1. The pump shaft 8 can be rotated either manually or most suitably by a motor (not shown) at the end 19 of the pump shaft 8 protruding from the pump.

[0014] At least one protrusion 10 is arranged to protrude from the pump shaft 8. In the example of Figure 1 there are two protrusions 10 which are arranged on the opposite sides of the pump shaft 8 and formed as a uniform piece. The protrusions 10 are formed in such a manner that they do not substantially change their shape during pumping. The protrusions 10 are rigidly locked to the pump shaft 8 by means of a hole 20 provided in the protrusions 10 in the example of Figure 1. In the direction of the pump shaft 8 the protrusions 10 extend from one end wall 2 of the pump chamber 1 to the other 3, naturally taking a required clearance into account. The pump shaft 8 is pivoted to a protrusion 21 protruding from the end wall 3 of the pump chamber 1, the protrusion also comprising required seals 22.

[0015] The protrusions 10 are not in contact with pumping material itself, so they may be made of a solid material or comprise openings, as is explained in more detail later on.

[0016] The pump shaft 8 and the protrusions 10 connected thereto are arranged inside the hose-like element 11. The opposite ends 12,13 of the hose-like element 11 are arranged to rest against the end walls 2,3 of the pump chamber 1. The hose-like element 11 and the cylindrical inner surface 14 of the pump chamber 1 are, in the region between the end walls 2,3 of the pump chamber 1, attached to each other between the inlet opening 6 for the suction pipe 4 and the outlet opening 7 for the exhaust pipe 5 so that pumping material is not allowed to flow between the hose-like element 11 and the cylindrical inner surface 14 of the pump chamber 1 at the location of the attachment.

[0017] In the example of the drawing, the outer surface 15 of the hose-like element 11 is provided with a protrusion 17 extending along the entire length of the hose-like element 11 and arranged to be locked in a groove 18 provided in a section between the inlet opening 6 and the exhaust and outlet opening 7 of the pump chamber 1.

[0018] The hose-like element 11 is dimensioned such that the protrusions 10 change the cross-sectional shape of its surface 15 while the pump shaft 8 is rotating. The cross-sectional shape is thus defined according

to the tips of the moving protrusions 10 and the protrusion 17 of the hose-like element 11, which protrusion stays in its place in the groove 18.

[0019] The distance between the cylindrical inner surface 14 of the pump chamber 1 and the free end of the protrusion 10 is smaller than or as big as the wall thickness of the hose-like element 11. This guarantees that at the free end of the protrusion 10, the hose-like element 11 is pressed tightly against the cylindrical inner surface 14 of the pump chamber 1.

[0020] To reduce friction, a rotating support element 16 is arranged at the free end of the protrusion 10. In the example of the figure, the support element 16 is a cylindrical pin of plastic, for instance, which is rotatably supported in a groove arranged at the free end of the protrusion 10 and the length of which is approximately the distance between the end walls 2,3 of the pump chamber 1.

[0021] Although the pump can be operated by using a single protrusion 10, it is preferable to arrange at least two protrusions 10 to protrude from the pump shaft 8, whereby it is easier to control forces which occur during pumping. Also, the pumping power per one pump shaft cycle increases. There can be a freely selectable number of protrusions 10 arranged at regular intervals and protruding radially. The upper limit for this number is defined mainly according to the size of the pump.

[0022] The inlet opening 6 for the suction pipe 4 and the outlet opening 7 for the exhaust pipe 5 divide the cylindrical inner surface 14 of the pump chamber 1 in the circumferential direction of the pump chamber 1 into two parts of different sizes, the shorter part being attached with the hose-like element 11 by means of the protrusion 17 and the groove 18 in the example of Figure 1. This shorter part between the inlet opening 6 and the outlet opening 7 is arranged to be as short as possible, whereby no waste space develops nor any unnecessary loads are caused on the joint 17,18 between the hose- like element 11 and the pump chamber 1. Correspondingly, if suction pipes and exhaust pipes arranged at the end wall, for instance, are used, the distance between them should be as short as possible.

[0023] The hose-like element 11 is formed of a flexible material substantially inelastic in the circumferential direction, most suitably of rubber, plastic, steel or a combination thereof. The circumference length of the hose- like element 11 is selected so that the pump shaft 8 and its protrusions 10 have enough space to rotate inside the hose-like element 11 without stretching

it in the circumferential direction.

[0024] The protrusion 10 is dimensioned such that the path of the end surface of the hose-like element 11 is always outside the opening made to the end wall 3 of the pump chamber 1 for the pump shaft 8. In this way, the end 13 of the hose-like element 11 does not wear so much, since the end 13 always rests against the straight and even surface of the end wall 3 only.

[0025] The pump of the invention operates in the following way.

[0026] The direction of rotation of the pump shaft 8 is denoted by an arrow 24 in Figure 1. It is to be stressed, however, that the pump can be used just as well in both directions. The hose-like element 11, which is fastened in the groove 18 and the shape of which element 11 is continuously changed by the protrusions 11 and the support elements 16 rotating at their ends during rotation of the pump shaft 8, divides the pump chamber 1 into three different spaces A, B, C at the operating stage shown in the example of Figure 1.

[0027] Let us first examine the space A. Its volume increases continuously during the time the pump shaft 8 rotates in the direction of the arrow 24. At the same time, the pressure drops in the space A and pumping material is sucked from the suction pipe to the space A until the next rotating support element 16, in Figure 1 the rotating support element 16 on the right, closes the inlet opening 6 for the suction pipe 4. The situation is now the same as in the space denoted by B in Figure 1. In the space B, the pressure remains constant and the pumping material does not move forward until the preceding rotating support element 16 passes the outlet opening 7 for the exhaust pipe 5.

The situation is then the same as in the space denoted by C in Figure 1. The volume of the space starts to decrease when the pump shaft 8 rotates in the direction of the arrow 24. At the same time, the pumping material is forced to exit via the outlet opening 7 to the exhaust pipe 5. The pumping stages are repeated for each protrusion 10 on each cycle of the pump shaft 8. The number of completed pumping events corresponds to the number of protrusions 10 on each cycle of the pump shaft 8.

[0028] In the space B, the hose-like element 11 is supported on the surface of the protrusions 10 in the example of Figure 1. Potential pressure at this point is, however, very low and thus the frictional forces between said parts remain low. In practice, a quantity of pumping material always enters the hose-like element 11, which, on one hand, advances the lubrication of the surfaces and, on the other hand, supports the hose-like element 11. It is therefore desirable, not harmful, that pumping material gets inside the hose- like element 11.