MXPA01011354A

MXPA01011354A - Marine propeller with detachable blades

Info

Publication number: MXPA01011354A
Application number: MXPA/A/2001/011354A
Authority: MX
Inventors: Istvan Bacskay
Original assignee: Kamewa Ab
Priority date: 1999-05-19
Filing date: 2001-11-07
Publication date: 2002-06-05

Abstract

A marine propeller comprises a hollow hub body (11), a plurality of propeller blades (16) and a plurality of fastening devices (19, 21) for each propeller blade (16). Each fastening device includes a tension rod (19) and a flange member (22) mounted on the tension rod. The propeller blades (16) may be turnable for adjustment of the blade pitch angle (&agr;) andlockable in a selelcted position by means of the fastening devices (19, 21). The flange member (22) has a plurality of recesses (23) and tensioning members (24) received in the recesses. These tensioning members (24) are extendable from the flange member (22) towards the hub body wall (14) to apply tension to the tension rod (19).

Description

MARINE PROPELLER WITH REMOVABLE FLOPS DESCRIPTION OF THE INVENTION This invention relates to a marine propeller of false blades, that is, a marine propeller, the blades of which are removably secured to a hub body. More particularly, the invention relates to a marine propeller of false blades having a hollow cube body and a plurality of propeller blades distributed around the hub body and removably secured thereto in engagement with a bearing surface external on a wall of the cube body. Although not limited in this way, the invention is particularly useful in a false blade propeller having adjustable blades, i.e., a propeller the blades of which can be moved to a selected pitch position in the hub body and Fixed in this position. In a propeller the pitch of the blade is fixed in the direction in which it can not be changed when the propeller is rotating. However, when the propeller is stationary, it is possible to change the pitch within a certain relatively small range. A need for a reduced pitch change of a marine propeller can occasionally occur as a REF: 133406 consequence of the changed operating conditions of the loading equipment with the propeller, for example, with respect to a change from summer operation to winter operation or operation at commercial speed or maximum change. The specifications of patents GB-1 455 504 and DE-483 317 and a publication of the company KaMeWa 7ABP (Adjustable Built-Up Propeller) published in 1974 by Karlstads Mekaniska Werkstad (Sweden), show some examples of prior art modalities of marine propellers of removable blades with removable blades, each The blade is secured to the hub body by a plurality of bolts. In these propellers of the prior art, the propeller blades are fixed to the hub body by means of a number of fixing devices. Each fastening device includes a rod or tension bar in the form of a threaded bolt which extends through the holes formed in the hub body and in the projections of the blade by which the blades are maintained on a supporting surface of the cube body. In the propellers shown in GB-1 455 504, the bolts are studs or studs passed from inside the hub body into the tapped holes in the projections of the blade and tightened by threaded nuts on the inner ends of the studs . The spikes are used to position the blades in a precise pitch position relative to the hub body. There is no precision to adjust the pitch. In the propeller shown in DE-483 317, the bolts are bolts with heads passed from the outer side, the side of the projections of the blade is exposed to water, through elongated holes in the projections of the blades in the body of the blade. Cube. Although the purpose of the elongated shape of the holes in the projections of the blade is not to make the pitch adjustable, however some adjustment of the pitch can be accepted. In the propeller shown in the publication of the aforementioned company, the headed bolts are passed from inside the hub body into the threaded dead holes in the projections of the blade. The holes, in the projections of the blade and the holes in the hub body are arranged so that a predetermined pitch position can be selected somewhat differently. The pins are used to place the blades exactly in the different pitch positions. When a blade can be adjusted, the bolts are first loosened so that the blade can be rotated about its longitudinal axis to a desired position within the range of adjustability. Then the bolts are tightened to fix the blade in the selected position. As will be appreciated, it is very important that the blades are firmly fixed in the selected adjustment position. The force by which the bolts have to secure the projection of the blade against the supporting surface, and therefore, the torque with which the bolts have to be tightened, is therefore substantial. Close to the bolts the space available for the application of wrenches or other tightening tools, is limited, however, and for this and other reasons it is difficult to apply a torque that is sufficiently large to ensure a satisfactory fixation that relies only in the friction between the projection of the blade and the body of the bucket. This is especially the case where the bolts are tightened from inside the hub body. The same problem exists in the propellers of false blades that have non-adjustable blades. Even in such helices, the fastening devices have to be tightened under a considerable torque.

In the propellers of the prior art the pins used to accurately position the blades relative to the hub body and to prevent undesirable pitch changes after the adjustment also occupies a certain space, and for this reason only a position of pitch something fixed within the adjustment range. It is desirable to be able to adjust the substantially continuous blades between the limits of the adjustment range, ie, to an infinite number of adjustment positions which can be selected when desired, and to lock the blades reliably in each selected adjustment position without being have to use spikes. Whether or not the propeller is of the type having adjustable blades, it is also desirable to be able to apply the fastening devices from within the hub body with adequate force using tools too small to allow them to be used within the hub body. Accordingly, it is an object of the invention to provide a helix of the initially indicated class having these desirable properties. According to the invention this object is achieved with a helix having the characteristics described in the characterization part of the independent claims. The dependent claims are directed to preferred features of the propeller according to the invention. As will appear more clearly from the description that follows, each tensioning rod - which may be the body of a bolt - may be provided with a protruding element, such as a nut or a bolt head, having a plurality of recesses distributed around the tension rod and a similar plurality of tension elements which are received in these recesses and can extend from the projecting element towards the wall of the cube body to force the projecting element away from the wall of the projecting element. cube body and therefore subject the tension rod to tension. Naturally, each tension element will be applied only to a fraction of the total tension force that has been applied to the tension rod to ensure reliable frictional clamping of the propeller blade to the hub body. However, the combined tensile force applied by the tensioning elements can ensure a firm frictional grip without the need to subject the individual tensioning elements to more than a small fraction of the force required for a firm hold of the blades of the propellers. of the prior art, wherein for each fastening device the torque is applied to a single fastening bolt head or to a nut on the fastening bolt. Because each tensioning element has only been subjected to a small force, the tension of the tensioning rod can be made by means of a small tool, such as a power wrench if the tension elements are screwed. In many cases, it is therefore possible to perform the tension operation from inside the cavity of the hub body; The propellers of the class with which the invention is concerned are normally large enough to allow a mechanic to work with a hand power tool inside the hub body when adjusting the position of the propeller blade. The tension rods in such cases can enter the propeller blade from the side of the projection of the blade that engages the bearing surface on the hub body. Therefore, they do not need to extend completely through the thickness of the projection of the blade, which therefore can have a smooth outer surface. This also means that the entire protrusion surface which engages the bearing surface on the hub body is available for the application of the tension rods. If, on the other hand, the tension rods enter the projection of the blade from the opposite side, the side exposed to water, the root of the propeller blade restricts the space available for the application of the tension rods. The invention will be understood more fully from the following description of a mode shown as an example in the accompanying drawings, mainly a propeller of false blades that has adjustable blades. Figure 1 is a side view of the propeller and a portion of the associated propeller shaft. Figure 2 is a view similar to Figure 1 but shows the propeller hub body sectioned along a plane containing the axis of the tail shaft; Figure 3 is an enlarged sectional view of the upper left corner of the hub body as shown in Figure 2 and the adjacent portion of the protrusion of the propeller blade; and Figure 4 shows a portion of the cube body as seen from line IV-IV in Figure 3.

The marine propeller of false blades 10 shown in the drawings is bolted to a projection R on a tail shaft S only a part of which is shown and the axis of which is designated C. The propeller 10 comprises a hub body. 11 generally cube-shaped recess 11 including a front wall 12 by which the hub body is bolted to the tail shaft projection R, a rear wall 13 and four side walls 14 placed around the C axis. Three of the four side walls are shown in Figure 2 while the fourth is shown in Figure 1. The circular openings 12A and 13A centered on the C axis of the tail shaft are formed in the front wall 12 and the rear wall 13. The openings circular 14A formed in the side walls 14 are centered on orthogonal axes L (only one of them is shown in the drawings) which intersect each other and the C axis of the tail axis at a point K. Normally, the aperture 13A of the back wall, through which the cavity HA of the hub body 11 is accessible, it is hermetically sealed by a removable closure plate 15. The external surface of each side wall 14 forms an external flat bearing surface 14C for a propeller blade 16 secured to the hub body 11 by a circular blade projection 17 centered on the L-axis. A circular flat projection 17A is formed on the side of the projection 17 of the blade facing the hub body 11 and projecting into the opening 14A of the side wall 14 for centering the projection 17 of the blade and thus the propeller blade 16 complete with respect to the hub body 11. On the same side the projection of the blade has an annular groove accommodating a sealing ring 18 by the which the projection of the blade is in sealing engagement with the support surface 14C. Each of the four propeller blades 16, which are arranged in cruciform configuration, is held to the hub body 11 by a plurality of, sixteen in the illustrated embodiment, the tension rods 19 in the form of studs which are spaced apart. uniformly along an imaginary circular cylindrical surface D centered on the axis L with its axes T contained in this cylindrical surface D and extending parallel to the axis L. Each tension rod or stud 19 extends with a reduced space through an opening 20 in the side wall 14 and has an end portion screwed into a threaded hole 17B in the blade projection 17. The openings 20 are evenly distributed along the imaginary cylindrical surface D mentioned above containing the axes of the studs 19. As shown in Figure 4, the openings 20 are elongated in the circumferential direction to admit a slightly rotating movement of the propeller blade 16 around the axis L and therefore admits a gradual (continuous) variation of the pitch angle of the propeller blade in a range of angular adjustment of some degrees. The other end portion of the stud 19 extends internally beyond the inner side of the side wall 14 and has been screwed into a component 21 which is called tensioning nut here. The tension nut 21 serves to secure the projection 17 of the propeller blade against the bearing surface 14C with a great force. It is of the type ("torquenut" (torsion nut)) sold by the North American company Superbolt, Carnegie, Pennsylvania, USA, under the trademark SUPERBOLT ©. The tension nut 21 comprises a protrusion element 22 in the form of a generally circular cylindrical nut body with an internal thread which is closely connected to the external thread of the stud 19. The protrusion element 22 is provided, in the illustrated embodiment, with a number of sixteen recesses in the form of axial threaded holes 23 extending through the protrusion element and uniformly spaced apart circumferentially. In each recess a tensioning element in the form of a tensioning screw 24 having a head 25 is screwed from the outer side, that is, the side of the projection element 22 which faces away from the inner side of the wall 14 of the hub body. The tensioning screw 24 is of such a length that when it is completely screwed into the recess, its tip protrudes from the inner side of the protrusion element 22, that is, the side facing the wall of the hub body 14. Associated with the tension nut 22 there is a metal washer 26. This washer, which has a sliding assembly for the stud 19, is very hard at least on the side facing the protrusion element 22 so that it can withstand the high pressure of the surface produced by the elements. tensioning screws 24. So that the washer 26 can not be excessively deformed in the portions thereof which form a bridge with the open areas of the openings 20, that is to say, the areas that are not occupied by the stud 19 (see FIG. 4), should have a certain minimum thickness. If desired, the illustrated washer 26 can be supplemented with an additional washer (not shown), conveniently the very hard but relatively thin washer that forms a standard part of the SUPERBOLT® tension nut and is positioned adjacent the boss element 22. In In this case, the washer 26 can sometimes be very thin and less hard than in the case where it is the washer alone. Conveniently, the thickness of the washer 26 or, in the case where an additional washer is used, the combined thickness of the two washers, is at least 0.3 times the radial width of the opening 20. When a propeller blade 16 can be mounting, is placed with the inner or lower side 17C of the blade protrusion 17 remaining on the bearing surface 14C and with the holes 17B in the projection of the blade in register with the elongated openings 20 in the wall of the hub body 14. Then the studs 19 are screwed into the holes 17B of the projection of the blade from inside the cavity HA of the hub body 11, the washers 26 slide over the studs 19 and the tensioning nuts 21 are screwed into the exiting ends of the asparagus. After the propeller blade has been returned to the desired position, the tension nuts 21 are tightened until there is no gap between the projection of the blade 17 and the wall of the hub body 14 or between the latter and the nut assembly Tensioner of the washer. This tightening or sealing can be carried out without it being necessary to apply a very large torque to the tension nuts 21. If the tensioning screws 24 are already inserted in the projection element 22, they should not be screwed to such an extent that their tips protrude from the inner side of the projection element. Then the tensioning screws 24 of each tension nut 21 are tightened to support the wall 14 of the hub body through the intermediate of the washer 26 and raise the protrusion element 22 of the washer so that the associated stud 19 will be tensioned . Because of the large number of tensioning screws 24 of each tensioning nut 21, the tension load on the studs 19 can be applied with moderate effort and will be sufficient for the propeller blade to be properly fixed in the selected position only by friction between the projection 17 of the blade and the support surface 14C. Accordingly, the tightening can be performed with the help of a small power wrench from inside the cavity 11A of the hub body 11. Finally the closure plate 15 is attached. If the placement of the propeller blades 16 needs to be changed, the closing plate 15 is removed so that the tensioning screws 24 and consequently the tensioning nuts 21 can be loosened to admit the propeller blades back to the new desired position , whereupon the tension nuts and the tensioning screws are tightened. If the propeller 10 would probably have to operate under very severe conditions, such as on ice, so that the propeller blades will be subject to severe loads, additional fixation against the undesirable return of the propeller blades can be achieved by applying a friction enhancing material to the bearing surface 14C of the hub body and / or the associated internal side 17C of the projection 17 of the blade, For exa, by spraying a layer of chromium oxide or tungsten carbide on one or both surfaces. It is noted that in relation to this date, the best method known by the applicant 'to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A marine propeller comprising a hollow cube body, a plurality of propeller blades distributed around the cube body and secured in a removable manner to the latter. coupling with an external bearing surface on a wall of the hub body, a plurality of fastening devices for each propeller blade, each fastening device includes a tension rod which extends from the cavity of the hub body through the hubs. openings in the wall of the hub body and anchored in the hub body, and a protrusion element mounted on a tensioning rod and supported against the side of the wall of the hub body facing the cavity of the hub body, characterized in that the protrusion element of each fastening device has a plurality of recesses distributed around the tension rod and tension elements. received in the recesses, the tensioning elements can extend from the projection element towards the wall of the hub body to apply tension to the tensioning rod.
2. A marine propeller comprising a hollow hub body, a plurality of propeller blades distributed around the hub body and removably secured thereto in engagement with an external bearing surface on a wall of the hub body, a plurality of of fastening devices for each propeller blade, each fastening device includes a tensioning rod which extends from the cavity of the hub body through the openings in the wall of the hub body and is anchored in the hub body, and a protrusion element mounted on the tension rod and supported against the side of the wall of the hub body facing the cavity of the hub body, the openings in the wall of the hub body are elongated and the propeller blades can be rotated on the support surface for adjusting the pitch angle of the blade (a) in an angular range determined by the elongated openings and can be fixed in a selected adjustment position. within the range by means of the fixing devices, characterized in that the protrusion element of each fixing device has a plurality of recesses distributed around the tension rod and tension elements received in the recesses, the tension elements can extend from the protruding element towards the wall of the hub body to apply tension to the tension rod.
3. A marine propeller according to claim 1 or 2, characterized in that the tension rod is connected to the propeller blade by means of a threaded connection.
A marine propeller according to claim 1 or 2, characterized in that the tension rod is a stud, one end of which is screwed into the propeller blade, and the projection element is a nut screwed onto the other end portion. of the asparagus.
5. A marine propeller according to claim 3, characterized in that the projection element and the tension rod form an integral part.
6. A marine propeller according to claim 4, characterized in that the element of 1 protrusion is supported against the wall of the hub body through the intermediary of at least one washer of hard material. A marine propeller according to claim 6, characterized in that the thickness of the washer, or the combined thickness of the washers, is at least 0.3 times the width of the opening. A marine propeller according to claim 1 or 2, characterized in that the recesses of the projection element are threaded axial bores extending through the projection element, and the tensioning elements are tensioning screws received in the recesses. A marine propeller according to claim 1 or 2, characterized in that a friction-enhancing material, such as a layer of chromium oxide or tungsten carbide, is applied to at least one of the body's support surface of bucket and the surface of the propeller blade secured against the supporting surface.