Abstract:
The present invention relates to an adjustment device for adjusting the pitch angle of the propeller blades ( 4 ) of a propeller pump ( 1 ) and a propeller pump incorporating such a device. The adjustment device comprises adjustment means ( 5; 25; 35 ) mounted within the hub ( 2 ) arranged to be axially movable in a direction along the drive shaft ( 7 ), the adjustment means ( 5; 25; 35 ) being provided with a plurality of guide slots ( 6; 26   a   , 26   b   ; 36 ) arranged at circumferential spacings around the surface; a plurality of attachment means ( 20 ) rotationally mounted in the hub ( 2 ), each being fixedly attached to a propeller blade ( 4 ) and supported by at least one guide slot ( 6; 26   a   , 26   b   ; 36 ), wherein each attachment means ( 20 ) and the corresponding at least one guide slot ( 6; 26   a   , 26   b   ; 36 ) are arranged to interact such that a force applied on the attachment means ( 20 ) is distributed symmetrically about an axis perpendicular to the drive shaft ( 7 ) and parallel with a rotational axis of the attachment means ( 20 ); and wherein the guide slots ( 6; 26   a   , 26   b   ; 36 ) are arranged to, at an axial movement of the adjustment means ( 5; 25; 35 ), cause the attachment means ( 5; 25; 35 ) to rotate about its own rotational axis, whereby the propeller blade ( 4 ) in turn is rotated.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to propeller pumps or axial pumps and, in particular, to a device for adjusting the propeller blades of the pump. 
       STATE OF THE ART 
       [0002]    In many pump applications it is often desirable and/or necessary to vary the flow, which can be achieved, for example, by rotating the propeller blades of the pump about their own axis (adjusting the angle of incidence of the fluid against the propeller blades), i.e. adjusting the pitch angle of the propeller blades. These adjustments are often performed manually, i.e. the pump is disconnected and an operator manually adjusts the blade to obtain the desired or required angle with respect to the flow direction. This is time consuming as well as it entails high costs due to operational disturbances and labour requirements. Moreover, this manual adjustment is highly impractical if these variations are of a frequent nature and it may even be inapplicable if the changes of the flow occur at a sufficiently high frequency. Accordingly, it is often necessary to be able to adjust the flow during the operation of the pump. 
         [0003]    By using so called frequency control to adjust the flow of a pump it is possible to achieve this flow variation during the operation of the pump by increasing/decreasing the number of revolutions of the propeller in order to achieve a corresponding increase/decrease of the flow in accordance with the requirements or desires. However, the frequency control allows an adjustment of the flow of about 30%, which, in many applications, is a too narrow range. This applies in particular in applications where considerably flow variations are desired or required as, for example, in adventure baths, artificial waterfalls for paddling and other waterfall activities such as rafting. Therefore, a number of approaches have been proposed that address the above mentioned problems. 
         [0004]    U.S. Pat. No. 2,357,229 discloses a pump rotor provided with swivelling blades angularly adjustable automatically while the rotor is in motion. Each swivelling blade is formed integrally with its spindle and with an operating crank depending therefrom. Pivotally mounted on the lower end of each crank is a block slidably fitting in a groove in one face of a hollow prismatic member disposed around the axis of the hub. The prismatic member is hollow with a cylinder interior serving as the cylinder of the axial servo-motor and slidable on the fixed piston carried at the lower end of a hollow part of the hub depending from the inner bearings. The admission of fluid under pressure to the servo-motor cylinder on one side or the other of the piston causes axial reciprocation of the member and this imparts a swivelling movement to the cranks and hence to the blades through sliders and inclined grooves, thereby obtaining a variation of the flow. 
         [0005]    EP 0 541 046 discloses a propeller pump with blade pitch adjustment in which an adjustment apparatus by a threaded spindle, an adjustment nut axially adjustable thereon which is provided with a slide bar and, via a guide bar bracket arranged in the propeller hub, determines the position of the blades and thereby allows a variation of the flow. 
         [0006]    JP 60162073 A discloses a runner-vane operating mechanism for mixed-flow water wheel. In this mechanism, a slidable guide directly connected to a piston of a vertically movable servo-motor and an inclined groove is formed in each opposed position on an operating lever fixed onto a runner vane stem. On both sides of the inclined groove, a pair of opposed slider blocks are arranged in slidable ways in the longitudinal direction of the groove. Each blade is fixedly connected to a respective operating lever. By sliding each block in respective groove, the pitch angle of each corresponding blade can be adjusted. 
         [0007]    DE 1 101 154 discloses an adjustment device for adjusting the blades of a pump or a turbine comprising a hub, bearings incorporated therein, a plurality of propeller blades mounted in said bearings and projecting from said hub, each blade being connected with a corresponding block through a slot, which in turn is connected to a slot block arranged in the slot. By an axial displacement of the slot an adjustment of the pitch angle of blades can be obtained. 
         [0008]    All of the above described pumps with adjustable propellers blades or adjustments devices disclose an unsymmetrical distribution of forces at the hub or, in fact, at respective attachment point of the cranks or arms. Furthermore, the pump rotor with adjustable propeller blades according to U.S. Pat. No. 2,357,229 and the adjustment device of JP 60162073 A both discloses long cranks or arms carrying the blades, which gives a long arm of lever between the blade and respective attachment point at the hub. This may cause problems because, in many applications, the flow may periodically be very strong, in particular in certain applications such as in adventure baths, artificial waterfalls for paddling and other waterfall activities such as rafting, which entail that considerable forces will act on the pumps and especially on parts of the pumps such as the propeller blades, the cranks or arms carrying the blades, and the attachment points of the cranks or arms. Accordingly, the durability of the pumps can be severely shorten. Furthermore, since the wear of certain parts such as the attachments point of the cranks or arms at the hub may be significant, shutdowns due to maintenance may be frequent. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0009]    Thus, one object of the present invention is to provide an adjustment device for adjusting the propeller blades of a pump and a pump including such a device which, in comparison with prior art, have a high endurance against wear and a high ability of withstanding large forces. This, in turn, provides for a long durability and a good reliability. 
         [0010]    It is another object of the present invention to provide a propeller pump comprising an adjustment device for adjusting the propeller blades of the pump and an adjustment device for adjusting the propeller blades of the pump which can obtain large variations of the flow. 
         [0011]    Yet another object of the present invention is to provide a propeller pump comprising an adjustment device for adjusting the propeller blades of the pump during operation of the pump and an adjustment device for adjusting the propeller blades of the pump during operation of the pump. 
         [0012]    These and other object are achieved according to the present invention by providing a propeller pump comprising an adjustment device for adjusting the propeller blades of the pump and an adjustment device for adjusting the propeller blades of the pump having the features defined in the independent claims. Preferred embodiments are defined in the dependent claims. 
         [0013]    For purposes of clarity, the term “pitch angle” refers to the angle between the outer periphery of the pressure side of the propeller blade and the neutral line. 
         [0014]    According to a first aspect of the present invention, there is provided a propeller pump comprising a hub, bearings incorporated therein, a plurality of propeller blades mounted in the bearings and projecting from the hub, comprising an adjustment device for adjusting the pitch angle of the propeller blades about an axis perpendicular to a drive shaft of the propeller. The adjustment device comprises adjustment means mounted within the hub arranged to be axially movable in a direction along the drive shaft, the adjustment means being provided with a plurality of guide slots arranged at circumferential spacings around the surface; a plurality of attachment means rotationally mounted in the hub, each being fixedly attached to a propeller blade and supported by at least one guide slot, wherein each attachment means and the corresponding at least one guide slot are arranged to interact such that a force applied on the attachment means is distributed symmetrically about an axis perpendicular to the drive shaft and parallel with a rotational axis of the attachment means; and wherein the guide slots are arranged to, at an axial movement of the adjustment means, cause the attachment means to rotate about its own rotational axis, whereby the propeller blade in turn is rotated. 
         [0015]    According a second aspect of the present invention, there is provided an adjustment device for a propeller pump comprising a hub, bearings incorporated therein, a plurality of propeller blades mounted in said bearings and projecting from said hub, for adjusting the pitch angle of said propeller blades about an axis perpendicular to a drive shaft of the propeller in accordance with the first aspect of the present invention. 
         [0016]    Thus, the present invention is based on the idea of arranging each one of the guide slots, which are formed so as to, at an axial movement of the adjustment means, cause the attachment means on which the propeller blades are mounted to rotate about its own rotational axis such that the propeller blades in turn are rotated, to interact with a corresponding attachment means such that a force exerted on the corresponding propeller blade or the attachment means is distributed symmetrically about an axis perpendicular to the drive shaft and parallel with a rotational axis of the attachment means. 
         [0017]    This solution provides several advantages over the existing solutions for adjusting the propeller blades of a pump. One is that the ability to withstand large forces is improved significantly in comparison with the known devices and the systems described in U.S. Pat. No. 2,357,229, EP 0 541 046, JP 60162073, and DE 1 101 154, which all discloses an unsymmetrical distribution of the forces applied to the propeller blades and propagated further to the attachment means. This is an important feature since the forces acting on each blade usually are of a considerably magnitude. In some applications where the flows periodically can be extremely strong, such as in adventure baths, artificial waterfalls for paddling and other waterfall activities such as rafting, this ability may even be a necessary condition because of the considerable forces acting on the pumps and especially on parts of the pumps such as the propeller blades, the cranks or arms carrying the blades, and the attachment points of the cranks or arms. 
         [0018]    Another advantage is that, due to the symmetrical distribution of the forces, the pitch angle of the propeller blades can be adjusted during operating conditions with large flows applying large forces on the propeller blades, which, in turn, impart large forces to the attachment means. Accordingly, the applicability of the propeller pump according to the present invention is increased. 
         [0019]    A further advantage is that the flow can be varied or changed within a broad range of possible flows at a maintained high efficiency. According to a preferred embodiment, the flow can be varied within a range of 100-50% at a efficiency of about 85-80%. 
         [0020]    An additional advantage is that the construction of the adjustment device according to the present invention is less complex in comparison with the prior art solutions discussed above. Thereby, the manufacturing costs can be lowered. 
         [0021]    Moreover, due to the symmetrical force distribution in the adjustment device and the simple construction thereof, a high endurance against wear can be achieved. This, in turn, provides for a long durability and a good reliability, and, in addition, lowered maintenance costs. 
         [0022]    In one embodiment of the present invention, each attachment means is supported by two inclined guide slots. Thereby, the ability to withstand forces can be improved even further. 
         [0023]    According to one exemplifying embodiment of the present invention, the two inclined guide slots consist of one upper guide slot, in a direction along the drive shaft, and one lower guide slot, in a direction along the drive shaft, the upper and the lower guide slot being symmetrically arranged about a centre, in a direction along the drive shaft, perimeter line of the adjustment means such that an angle is formed between each guide slot and the perimeter line. 
         [0024]    Further objects and advantages of the present invention will be discussed below by means of exemplifying embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0025]    Above-mentioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments, merely exemplifying, in conjunction with the attached drawing, wherein: 
           [0026]      FIG. 1  schematically shows a propeller pump including an adjustment device according to the present invention; 
           [0027]      FIG. 2  schematically shows in more detail the propeller pump in  FIG. 1  including an adjustment device according to the present invention; 
           [0028]      FIG. 3  shows the adjustment means according to the present invention of  FIG. 2 ; 
           [0029]      FIG. 4  shows a second embodiment of the adjustment means according to the present invention; 
           [0030]      FIG. 5  shows a third embodiment of the adjustment means according to the present invention; and 
           [0031]      FIG. 6  illustrates the pitch angle of a propeller blade shown in cross section. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    In the following, there will be disclosed preferred embodiments of the present invention. 
         [0033]    Hereinafter all directions will be referred to the two-dimensional coordinate systems shown in  FIG. 1 . 
         [0034]    With reference first to  FIG. 1 , a propeller pump comprising an adjustment device in accordance with the present invention will be described. The propeller pump or the axial pump  1  comprises a hub  2 , in which bearings  3  (see  FIG. 2 ) are incorporated. A propeller blade  4  is mounted in each bearing  3  and projects from the hub  2 . The direction of the flow is indicated with an arrow denoted with A, i.e. in the y-direction as indicated with the two-dimensional coordinate system of  FIG. 1 . Furthermore, the pump  1  is mounted in a pump house  9 . 
         [0035]    Turning now to  FIG. 2 , the pump  1  shown in  FIG. 1  will be described in more detail. Adjustment means  5  is slidably arranged within the hub  2  so that it can be moved reciprocally in the y-direction, i.e. in a direction along a drive shaft  7  of the pump  1  connected to a motor (not shown) for driving the pump. In this embodiment, the adjustment means  5  is a cylindrical sleeve arranged concentrically with the drive shaft  7 . An outer envelope surface  8  of the adjustment cylinder  5  is provided with a number of inclined guide slots  6 , formed in pairs, see  FIG. 2 . The pairs of guide slots  6  are arranged at circumferential spacings at diametrically opposed positions around the surface  8  and symmetrically about a centre, in the x-direction, perimeter line of the adjustment cylinder  5  such that an angle is formed between each guide slot  6  and the perimeter line. As will be described hereinafter with reference to  FIGS. 3-5  and as the skilled man easily realizes, there are a number of other designs of the adjustment device and the guide slots that are conceivable and within the scope of the present invention. As one example, the angle between each guide slot and the centre perimeter line may be varied. In another example, the pairs of guide slots are replaced by a single guide slot. 
         [0036]    Furthermore, a pair of yokes  12  is fixedly attached to the adjustment cylinder  5 , for example, by means of bolts (not shown). Moreover, an attachment rod  14  is fixedly mounted between the yokes  12 , for example, by means of mounting screws (not shown), which attachment rod  14 , in turn, is connected to actuator means (not shown) arranged in a housing  16  powered by drive unit  17 . The drive unit  17  may be electrical, pneumatic, or hydraulic. In this embodiment, the drive unit  17  is, in turn powered via a drive cable  18  arranged within the drive shaft  7 . If the drive unit  17  is electrical the drive cable  18  is an electrical lead, if the drive unit  17  is hydraulic the drive cable is an oil line, and if the drive unit  17  pneumatic the drive cable  18  is a line conducting, for example, pressurized air. According to one preferred embodiment, the attachment rod  14  is mounted on a worm drive arranged in the housing  16 , which worm drive, in turn, is connected to the drive unit, which, in this case, is electrical. 
         [0037]    Each propeller blade  4  is mounted on an attachment plate  20 , which in this embodiment is formed as a circular plate. A pair of guide means  22  are, in turn, mounted on the attachment plate  20 . According to this embodiment, the guide means  22  are guide pins or protrusions, each being slidably supported in a respective inclined guide slot  6 . In one embodiment, the guide means  22  are needle bearings arranged in pulleys or rolls. 
         [0038]    With reference now to  FIG. 3 , the adjustment means in accordance with the present invention of  FIGS. 1 and 2  is shown in more detail. According to this embodiment, the adjustment means  5  is a cylindrical sleeve and the outer envelope surface  8  of the adjustment cylinder  5  is provided with a number of inclined guide slots  6 , formed in pairs. In this embodiment, the slots are through openings, which not however is a necessary feature. For example, the slots can be formed as recesses in the outer envelope surface  8 . The pairs of guide slots  6  are arranged at circumferential spacings at diametrically opposed positions around the outer surface  8  and symmetrically about a centre, in the x-direction (i.e. a direction perpendicular to the drive shaft), perimeter line of the adjustment cylinder  5  such that an angle is formed between each guide slot  6  and the perimeter line. 
         [0039]    Turning now to  FIG. 4 , a second embodiment of the adjustment means in accordance with the present invention will be shown. According to this embodiment, the adjustment means  25  is a sleeve having a square-formed outer envelope surface  28   a - 28   d , i.e. in a cross section, in a plane perpendicular to the y-direction, the outer perimeter of the sleeve is quadratic, and a circular inner envelope surface  29 , i.e. in a cross section, in a plane perpendicular to the y-direction, the inner perimeter of the sleeve is circular. Furthermore, each lateral surface  28   a - 28   d  (where only the sides  28   a ,  28   b  are shown in  FIG. 4 ) of the outer envelope surface  28  of the adjustment sleeve  25  is provided with a pair of inclined guide slots  26   a  and  26   b . In this embodiment, the slots are through openings, which however is not a necessary feature. For example, the slots can be formed as recesses in the outer envelope surface  8 . The pairs of guide slots  26   a  and  26   b  are arranged at circumferential spacings at diametrically opposed positions around the outer surface  28  and symmetrically about a centre, in the x-direction (i.e. a direction perpendicular to the drive shaft), perimeter line of the adjustment sleeve  25  such that an angle is formed between an upper guide slot  26   a  and a lower guide slot  26   b , in the x-direction, of each pair and the perimeter line. 
         [0040]    Referring now to  FIG. 5 , a third embodiment of the adjustment means in accordance with the present invention will be shown. According to this embodiment, the adjustment means  35  is a circular sleeve. An outer envelope surface  38  of the adjustment sleeve  35  is provided with a number of V-shaped guide slots  36 . In this embodiment, the slots are through openings, which however is not a necessary feature. For example, the slots can be formed as recesses in the outer envelope surface  38  of the sleeve. The guide slots  36  are arranged at circumferential spacings at diametrically opposed positions around the outer surface  38  and symmetrically about a centre, in the x-direction (i.e. a direction perpendicular to the drive shaft), perimeter line of the adjustment sleeve  35  such that an angle is formed between each arm of respective guide slot  36  and the perimeter line. 
         [0041]    As should be obvious for the man skilled in the art from the above, there are a number of conceivable designs and modifications of the adjustment device and, in particular, of the adjustment means and the above described embodiments should be considered only as exemplifications. In order to further illustrate this, a yet another embodiment of the adjustment means will be discussed in the following. According to this further embodiment, the adjustment means can be provided with groups of four inclined guide slots. In this embodiment, the slots are through openings, which however is not a necessary feature. For example, the slots can be formed as recesses in a outer envelope surface of the sleeve. The guide slots are arranged at circumferential spacings around the outer surface and symmetrically about a centre, in the x-direction (i.e. a direction perpendicular to the drive shaft), perimeter line of the adjustment sleeve such that an angle is formed between each guide slot and the perimeter line. Preferably, this embodiment of the adjustment means is used with an attachment plate provided with four guide pins, wherein each guide pin is slidably supported in one inclined guide slot. Furthermore, the adjustment means can be designed as an octagonal sleeve or a hexagonal sleeve. Moreover, the different designs of the adjustments sleeve and the guide slots can be combined in other ways and the above mentioned, for example, the V-shaped guide slots can be provided on the sleeve have a quadratic outer perimeter. 
         [0042]    Now the operation of the pump and the adjustment device according to the present invention will be discussed. As indicated above, there is, in many applications, desirably or even necessary to change the flow of a pump or, in other words, change the amount of water pumped per time unit. According to this invention, this can be performed during operation of the pump at large flows. Moreover, the pump according to the present invention is capable of delivering flows within a broad range of flows. 
         [0043]    In operation, the adjustment device work as follows. First, the drive unit  17  receives an instruction or command that the flow should be increased or decreased by a control unit. This instruction can be created either manually by an operator via an operator unit or automatically by, for example, the control unit. The drive unit  17  activates the actuator means, which, in turn, moves the attachment rod  14  axially in the y-direction (i.e. along the axis of the drive shaft  7 ), either in forward direction or a rearward direction depending of whether the flow is to be increased or decreased. The attachment rod  14 , which is fixedly mounted between the yokes  12 , moves the yokes  12 , which, in turn, moves the adjustment means  5  in the axial direction, i.e. in the y-direction. 
         [0044]    If the adjustment means  5  is moved in a direction such that the pitch angle of the propeller blades increases, the flow is, in turn, increased. For example, at a movement in a forward direction of the adjustment means  5 , the guide pins  22  will slide in respective inclined guide slots  6  causing the attachment plates  20  to rotate in a counter clock-wise direction, as viewed in the  FIG. 1 . Thereby, each propeller blade  4  mounted on a respective attachment plate  20  is rotated in the same direction and the pitch angle of the propeller blades is increased. As described above and with reference to  FIG. 6 , the pitch angle is defined as the angle between the outer periphery  40  of the propeller blade  42  and the neutral line  44 . 
         [0045]    On the other hand, if the adjustment means  5  is moved in a direction such that the pitch angle of the propeller blades decreases, the flow is, in turn, decreased. At the movement in a rearward direction of the adjustment means  5 , the guide pins  22  will slide in respective inclined guide slots  6  thereby causing the attachment plates  20  to rotate in a clock-wise direction, as viewed in the  FIG. 1 . Accordingly, each propeller blade  4  mounted on a respective attachment plate  20  is rotated in the same direction and the pitch angle of the propeller blades is decreased and, thus, the flow of the pump is decreased. Preferably, the pitch angle can be changed within a range of approximately 28 degrees to 5 degrees, and more preferably, within a range of approximately 25 degrees to 6 degrees. Moreover, a preferred angle adjustment is approximately +/−1 degree. The flow change resulting from an adjustment of the angel with 1 degree depends of the absolute angle position. An adjustment from a large angle, for example, from 24 to 23 degrees, corresponds to a reduction of the flow of about 3%. At an adjustment from, for example, 8 to 7 degrees, the flow reduction is about 5%. According to one embodiment, a range of about 25 degrees to about 8 degrees corresponds to a regulating range of the flow about 50% to 100% of the flow at an approximately constant efficiency, i.e. at an efficiency of about 85-80%. 
         [0046]    During operation of the pump, and in particular during the adjustment operation to change the pitch angle of the propeller blades in order to increase or decrease the flow, the pump and in particular parts such as, for example, the propeller blades, the attachment means including the attachment plates and guide pins as well as the adjustment sleeve are subjected to forces of a considerable magnitude resulting from the flow. Due to the construction of the adjustment device in accordance with the present invention, in which the adjustment device is provided with guide slots formed symmetrically with respect to a centre line, along a x-direction and perpendicular to the y-direction (see  FIG. 1 ), of the sleeve and where the attachment means is arranged to interact with the guide slots, these forces of a considerable magnitude are distributed symmetrically about an axis perpendicular to the drive shaft and parallel with a rotational axis of said attachment means. Thereby, high endurance against wear and a high ability of withstanding large forces are obtained, which, in turn, provides for a long durability and a good reliability. 
         [0047]    Although specific embodiments have been shown and described herein for purposes of illustration and exemplification, it is understood by those of ordinary skill in the art that the specific embodiments shown and described may be substituted for a wide variety of alternative and/or equivalent implementations without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the preferred embodiments discussed herein. Consequently, the present invention is defined by the wordings of the appended claims and equivalents thereof.