Radial pump device

Abstract

The invention relates to a radial pump device (1) comprising: - a drive shaft (11) arranged to provide a rotational movement, - an adjustable excentre drive (12) arranged to be rotated around drive axis (A) by the drive shaft (11), - at least three pump elements (21, 22, 23, 24, 25) arranged to be actuated by the excentre drive (12), said pump elements being evenly distributed around the drive axis (A), wherein the adjustable excentre drive (12) is adjustable between a first and a second position (P1, P2) with respect to the drive shaft (11), wherein the excentre drive, when rotated, will act intermittently on the at least three pump elements (21, 22, 23, 24, 25) with a major stroke in the first position (P1) and a minor stroke, which is shorter than the major stroke, in the second position (P2). The adjustable excentre drive (12) comprises an opening (14) for receiving the drive shaft (11) with a play and a pivot connection allowing the drive shaft (11) to pivot between two end positions within the play of the opening (14) depending on the rotation direction of the drive shaft (11), wherein the adjustable excentre drive (12) will occupy the first position (P1) when the drive shaft (11) is rotated in a first direction (R1) and the second position (P2) when the drive shaft (11) is rotated in a second direction (R2), contrary to the first direction (R1).

Description

[0001] RADIAL PUMP DEVICE

[0002] TECHNICAL FIELD

[0003] The invention relates to an adaptive radial pump device. Specifically, the invention relates to a radial pump device with at least three pump elements arranged around an excentre drive, which pump device may be driven in two different modes depending on the rotational direction of the excentre drive.

[0004] BACKGROUND

[0005] Hydraulic pumps are used in many different applications to drive a hydraulic motor such as a hydraulic cylinder or a hydraulic rotation motor.

[0006] In some applications it is desired to use a relatively small radial pump device, since a small radial pump device may be made mobile and may therefore be utilised in many different applications and in many different environments.

[0007] Hydraulic radial pumps are useful in many different applications in view of that they are reliable and may be produced in different sizes so as to achieve a desired hydraulic flow.

[0008] A drawback of radial pumps is that they are not very flexible in that they are conventionally either arranged to provide a specific flow or a specific hydraulic pressure, which is also limited by the power provided by the motor. Specifically, if the motor used to drive the radial pump is of a lighter model with a limited power it is only possible to achieve a specific hydraulic pressure which may not be exceeded without adding an auxiliary gearing device or by using another more powerful motor to drive the hydraulic pump.

[0009] In EP 1775467 A1 , a switchable eccentric drive for a radial pump is disclosed, which is arranged to provide different hydraulic flows depending on the direction of rotation of the eccentric drive. A drawback with the disclosed is that it is adapted to drive two pump elements only, which will make it impossible to achieve a continuous flow of hydraulic fluid. Also, the construction of EP 1775467 A1 will not function if more than two pump elements are positioned around the eccentric drive because, when driven in the high flow mode, a third pump element would provide a counteracting force that will prevent the excentre drive from entering said high flow mode.

[0010] It would be advantageous to achieve a device overcoming, or at least alleviating, at least one or some of the drawbacks of the prior art. SUMMARY OF THE INVENTION

[0011] It is an object of the invention to provide a radial pump device able to deliver a reliable yet switchable hydraulic flow without the need of external gearing, which device may be driven by a relatively light motor, such as an electric motor.

[0012] According to a first aspect the invention relates to a radial pump device comprising: a drive shaft arranged to provide a rotational movement an adjustable excentre drive arranged to be rotated around a drive axis by the drive shaft, at least three pump elements arranged to be actuated by the excentre drive, said pump elements being evenly distributed around the drive axis, wherein the adjustable excentre drive is adjustable between a first and a second position with respect to the drive shaft, wherein the excentre drive, when rotated, will act intermittently on the at least three pump elements with a major stroke in the first position and a minor stroke, which is shorter than the major stroke, in the second position, wherein the adjustable excentre drive comprises an opening for receiving the drive shaft with a play and a pivot connection allowing the drive shaft to pivot between two end positions within the play of the opening depending on the rotation direction of the drive shaft wherein the adjustable excentre drive will occupy the first position when the drive shaft is rotated in a first direction and the second position when the drive shaft is rotated in a second direction, contrary to the first direction.

[0013] A great advantage of the inventive radial pump device is that it provides two different hydraulic flow outputs without the need of a gear box or the like. For many applications two different modes with the provision of two different hydraulic flow outputs solves many problems and drastically increases the usability of the pump device.

[0014] In specific embodiments of the invention the drive shaft includes a protrusion arranged to be received in a recess in the excentre drive, to allow the drive shaft to pivot around a pivot point at the interaction between the protrusion and the recess. As an alternative, the protrusion may be provided on the excentre drive and the recess in the drive shaft.

[0015] This is one advantageous way, among others, to provide the pivot point for the pivoting action of the excentre drive with respect to the drive shaft. It is inter alia advantageous because it may be achieved by relatively straight forward machining of the involved components. In embodiments of the invention a low friction element is arranged between the excentre drive and the pistons of the pump elements.

[0016] In specific embodiments of the invention a ball bearing is arranged around the excentre drive, and wherein an outer ring of the ball bearing is arranged to intermittently push pistons of the pump elements to provide a pump action. The outer ring of the ball bearing may of course be one of several outer rings arranged around the ball bearing.

[0017] The ball bearing allows the interaction between the outer ring thereof and the pistons to be free from rotation, thereby eliminating losses that could otherwise be produced by friction in the contact between the outer active surface of the excentre drive and the contact surface of the pistons. Hence, the ball bearing further increases the efficiency of the pump device.

[0018] As an alternative, an individual bearing may be arranged at each of the pump elements to provide friction free, or at least low friction, contact between the excentre and the pistons of the pump elements in an alternative manner.

[0019] In specific embodiments of the invention a resilient member is arranged to push the adjustable excentre drive towards the first position.

[0020] In such embodiments a high flow could be achieved regardless of the direction of rotation. However, in the second rotation direction the flow would be dependent on the pressure needed to drive the application. Specifically, if the pressure would surpass a first threshold, the flow will decrease with an increasing pressure until the second position has been occupied by the excentre drive with respect to the drive shaft, from which point the radial pump device will operate at a second, lower flow at a higher pressure. Hence, these embodiments provide the possibility of obtaining a pressure controlled flow within a specific range, which range will be determined both by the difference of eccentricity between the first and the second position and by the spring action of the resilient member.

[0021] Other embodiments and advantages will be apparent from the detailed description and the appended drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Below, specific embodiments of the invention will be described with reference to the appended drawings, of which:

[0023] Fig. 1 is a transparent perspective view of a first embodiment of a radial pump device according to the invention,

[0024] Fig. 2 is a transparent side view of the radial pump device in Fig 1 ,

[0025] Fig. 3a is a view of the radial pump device shown along the cut Ill-Ill in Fig. 2 in a first mode,

[0026] Fig. 3b is a view of the radial pump device shown in Fig. 3a in a second mode, and

[0027] Fig. 4 is a cut view a second embodiment of a radial pump device according to the invention.

[0028] DETAILED DESCRIPTION OF THE SHOWN EMBODIMENTS

[0029] In Fig. 1 a radial pump device 1 in accordance with the invention is shown in a transparent perspective view and in Fig. 2 the same radial pump device is shown in a transparent view from the side.

[0030] The radial pump device 1 comprises a drive shaft 11 arranged to provide a rotational movement and an adjustable excentre drive 12 arranged to be rotated around a drive axis A by the drive shaft 11 . Pump elements 21 , 22, 23, 24, 25 are arranged to be intermittently actuated by the excentre drive 12 to provide a continuous flow to drive a hydraulic application, such as a hydraulic cylinder or a hydraulic motor.

[0031] The function of the radial pump device 1 will now be explained with reference to Figs. 3a and 3b, which are cut views of the radial pump device along the cut Ill-Ill in Fig. 2 in two different modes.

[0032] In Fig. 3a the radial pump device 1 is shown in a first mode and in Fig. 3b it is shown in a second mode. A main difference between the first and the second mode is the direction of rotation, wherein the radial pump device rotates in a first direction Ri (clockwise in the drawing) in Fig. 3a and in a second, opposite direction R2(counter-clockwise in the drawing) in Fig. 3b. The rotation is provided by a drive unit (not shown) driving the drive shaft 12 and transferred to the excentre drive 11 via the locking interaction between the drive shaft 12 and the excentre drive 11 . At least three pump elements, in the shown embodiment five pump elements 21 , 22, 23, 24, 25 are arranged to be actuated by the excentre drive 12, which pump elements are substantially equiangularly arranged around the drive axis A, i.e. at equal angles with respect to each other, typically 360 degreed divided by the number of pump elements. In the shown embodiment with five pump elements, the mean angle is hence 72 degrees between two adjacent pump elements. The angles should preferably the same or close to the same to guarantee a smooth drive, but small variations are acceptable.

[0033] Further, the pump elements are preferably arranged at corresponding distances from the drive axis A such that they all may be reached by the excentre drive.

[0034] Each pump element 21 , 22, 23, 24, 25 comprises an outlet port 41 , 42, 43, 44, 45 arranged to allow the emission of an outlet flow when the pistons 31 , 32, 33, 34, 35 of the pump elements 21 , 22, 23, 24, 25 are pushed inwards. The pump elements comprise conventional back valves (not shown), one at each respective outlet port to prevent back flow into the pump elements, and one at each respective inlet port, which may be arranged facing the respective outlet port, the back valves in the inlet ports being arranged to prevent the useful flow provided by the action of the pistons from escaping.

[0035] The adjustable excentre drive 12 is adjustable between a first position Pi with respect to the drive shaft 11 representing the first mode of the radial pump device 1 as illustrated in Fig. 3a and a second position P2representing the second mode of the radial pump device 1 as illustrated in Fig. 3b. The excentre drive 12 will act intermittently on the pump elements 21 , 22, 23, 24, 25 when rotated, and with different strokes depending on the rotational direction.

[0036] In the first mode, as illustrated in Fig. 3a, when the drive shaft 11 is rotated in the first direction Ri, the excentre drive 12 will occupy the first position P1 and produce a major stroke. In the second mode, as illustrated in Fig. 3b, when the drive shaft 11 is rotated in the second direction R2the excentre drive 12 will occupy the second position P2and produce a minor stroke, which is less than the major stroke.

[0037] The positioning of the excentre drive 12 with respect to the drive shaft 11 is achieved in that the adjustable excentre drive 12 comprises an opening 14 for receiving the drive shaft 11 with a play and a pivot connection allowing the drive shaft 11 to pivot between two end positions within the play 14 depending on the rotation direction of the drive shaft 11 , wherein the adjustable excentre drive 12 will occupy the first position Pi when the drive shaft 11 is rotated in the first direction Ri and the second position Pi when the drive shaft 11 is rotated in the second direction R2, contrary to the first direction Ri. In the shown embodiment the radial pump device 1 the drive shaft 11 includes a protrusion 13 arranged to be received in a recess 15 in the excentre drive 12, to allow the drive shaft 11 to pivot around a pivot point PP at the interaction between the recess 15 and the protrusion 13. As an alternative, a pivot point could be achieved in many different ways, as long as it allows the interaction of the drive shaft 1 1 and the excentre drive 12 to occupy two different positions with different eccentricity, which is governed by the rotational direction of the drive shaft 11 .

[0038] In the shown embodiment a ball bearing 16 is arranged around the excentre drive 12, wherein an outer ring 17 of the ball bearing 16 is arranged to intermittently push the pistons 31 , 32, 33, 34, 35 of the pump elements 21 , 22, 23, 24, 25 to provide a continuous pump action.

[0039] The ball bearing is one embodiment of achieving a low friction in the interaction between the pump elements 21 , 22, 23, 24, 25 and the excentre drive 12. Other types of low friction elements may be used. For example, a separate bearing may be arranged at the contact surface of each pump element 21 , 22, 23, 24, 25.

[0040] During operation of the radial pump device 1 the excentre drive 12 will intermittently push the pistons 31 , 32, 33, 34, 35 to produce a hydraulic flow, pump element by pump element, wherein a continuous joint flow may be achieved. In the sequential instant shown in Fig. 3a the pump element 21 is at an end of a pump cycle where the piston 31 has been pushed by the excentre drive 12 to its innermost position from which it will be allowed to return outwards. The pistons are preferably spring loaded towards their outermost position.

[0041] Further, in the instant shown in Fig. 3a, the piston 32 has just concluded a pump cycle and is being returned outwards towards a starting position, whereas the piston 33 is in, or close to, its outermost position from which it will be pushed into the pump element 23 by means of the action of the excentre drive 12. Piston 34 is in an initial state of its pump cycle and the piston 35 has been pushed to a position close to its innermost position.

[0042] It should be noted that the pump device will need to comprise at least three pump elements in order for the excentre drive 12 to remain in the first position Pi. Namely, the pump elements work together to keep the excentre drive 12 in the first position Pi . In the instant shown in Fig. 3a, the first pump element 21 provide a counter force towards the outer ring 17 of the ball bearing 16. As may be understood from the drawing this force act on the excentre drive 12 via the ball bearing towards the second position P2shown in Fig. 3b, downwards in Fig. 3a. This force is however balanced by the third pump element 23 and the fourth pump element 24, which both provide counter forces that have major contribution contrary to the counter force of the first pump element 21 , thereby balancing the forces such that the excentre drive 12 will remain in the first position P1 with respect to the drive shaft 1 1 .

[0043] During operation there may be a slight fluctuation in the mutual position of the drive shaft 1 1 and the excentre drive 12, wherein the excentre drive 12 may intermittently leave the first position Pi for short periods of time. The joint contribution of the pump elements will however keep the excentre drive 12 close to the first position Pi. Also, the joint contribution of the pump elements will make sure that the produced flow remains continuous and even, in view of that a slight loss of flow production in one pump element will be compensated by an increased flow production in an opposed pump element.

[0044] In the sequence shown in Fig. 3b the drive shaft 1 1 is rotated at the same rotational speed, but in the opposite direction R2of rotation Ri illustrated in Fig. 3a and the excentre drive 12 will, as a consequence of the rotation direction, occupy a second position P2with respect to the drive shaft 1 1 . In this second position P2the eccentricity of the excentre drive 12 is less accentuated meaning that its impact on the pistons 31 , 32, 33, 34, 35 will be less important such that each pump cycle will produce a lower flow than when in the first position Pi (illustrated in Fig. 3a).

[0045] The lower flow provided in the second position P2makes it possible to instead achieve an increased pressure for the same drive unit, because less driving force will be required to rotate the excentre drive 12 via the drive shaft 1 1 .

[0046] In Fig. 3b the pump element 25 is shown at an end of a pump cycle where the piston 35 is at its innermost position from which it will be returned outwards. In view of the less accentuated eccentricity of the excentre drive 12 when it occupies the second position P2, the innermost position achieved in this mode is not as deep as in the mode shown in Fig. 3a, which is apparent from the distance remaining to the outlet channel 45 of the pump element 25 in said innermost position.

[0047] Further, in Fig. 3b, the pistons 32 and 33 are being returned outwards towards an outermost starting position, whereas the piston 33 has passed its outermost position and is in an initial state of its pump cycle where it is pushed into the pump element 23 by means of the action of excentre drive 12. Piston 34 has been pushed to a position close to its innermost position. In Fig. 4 a second embodiment of a radial pump device 1 in accordance with the invention is shown in a cut view. The main difference in the second embodiment with respect to the first embodiment is that a resilient member 18 is arranged to push the adjustable excentre drive 12 towards the first position Pi, in which a relatively higher hydraulic flow may be achieved. In the shown embodiment the resilient member 18 is comprised of a spring that pushes a contact member 19, which is arranged in contact with the drive shaft 11 . The resilient member 18 is arranged to act on the excentre drive 12 with respect to the drive shaft 11 .

[0048] In the second embodiment a high flow may be achieved also when the drive shaft 11 is driven in the second rotation direction R2. However, the flow will be dependent on the pressure needed to drive the hydraulic tool driven by the radial pump. Namely, if said pressure surpasses a first threshold Ti , corresponding to the spring force of the resilient member 18, the mutual position of the excentre drive 12 with respect to the drive shaft 11 will gradually move from the first position Pi wherein the flow will decrease with an increasing pressure until the second position P2has been occupied by the excentre drive 12 with respect to the drive shaft 11 , from which point the radial pump device 1 will operate at a second, lower flow at a higher pressure.

[0049] A skilled person will now how to adapt the spring force of the resilient member 18 and the eccentricity of the two different positions Pi and P2to best provide a usable difference between the two modes as provided by the two different positions Pi and P2, depending on the intended use of the radial pump device.

[0050] Above, the invention has been described with reference to specific embodiments. The invention is however not limited to these embodiments. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.

Claims

CLAIMS1 . A radial pump device (1 ) comprising: a drive shaft (11 ) arranged to provide a rotational movement an adjustable excentre drive (12) arranged to be rotated around drive axis (A) by the drive shaft (1 1 ), at least three pump elements (21 , 22, 23, 24, 25) arranged to be actuated by the excentre drive (12), said pump elements being evenly distributed around the drive axis (A), wherein the adjustable excentre drive (12) is adjustable between a first and a second position (Pi, P2) with respect to the drive shaft (1 1 ), wherein the excentre drive, when rotated, will act intermittently on pistons (31 , 32, 33, 34, 35) of the at least three pump elements (21 , 22, 23, 24, 25) with a major stroke in the first position (Pi ) and a minor stroke, which is shorter than the major stroke, in the second position (P2), characterised in that the adjustable excentre drive (12) comprises an opening (14) for receiving the drive shaft (11 ) with a play and a pivot connection allowing the drive shaft (11 ) to pivot between two end positions within the play of the opening (14) depending on the rotation direction of the drive shaft (11 ), wherein the adjustable excentre drive (12) will occupy the first position (Pi ) when the drive shaft (11 ) is rotated in a first direction (Ri) and the second position (P2) when the drive shaft (11 ) is rotated in a second direction (R2), contrary to the first direction (Ri).

2. The radial pump device (1 ) according to claim 1 , wherein the drive shaft (11 ) includes a protrusion (13) arranged to be received in a recess (15) in the excentre drive (12), or wherein the excentre drive (12) includes a protrusion arranged to be received in a recess in the drive shaft (1 1 ), to allow the drive shaft (1 1 ) to pivot around a pivot point (PP) at the interaction between the protrusion (13) and the recess (15).

3. The radial pump device (1 ) according to claim 1 or 2, wherein a low friction element is arranged between the excentre drive (12) and the pistons (31 , 32, 33, 34, 35) of the pump elements (21 , 22, 23, 24, 25).

4. The radial pump device (1 ) according to claim 1 or 2, wherein a ball bearing (16) is arranged around the excentre drive (12), and wherein an outer ring (17) of the ball bearing (16) is arranged to intermittently push the pistons (31 , 32, 33, 34, 35) of the pump elements (21 , 22, 23, 24, 25) to provide a pump action.

5. The radial pump device (1 ) according to any one of the preceding claims, wherein a resilient member (18) is arranged to push the adjustable excentre drive (12) towards the first position (Pi).

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