WO2011095620A1

WO2011095620A1 - Arrangement of a toothed belt wheel

Info

Publication number: WO2011095620A1
Application number: PCT/EP2011/051720
Authority: WO
Inventors: Gaute Tjensvoll
Original assignee: Fobox As
Priority date: 2010-02-08
Filing date: 2011-02-07
Publication date: 2011-08-11
Also published as: NO331391B1; NO20100194A1

Abstract

Device for a toothed belt wheel (1) comprising a toothed rim at the perimeter of the wheel, where the rim is composed of a number of segments (10) that are retained in relation to each other in a circle. The segments (10) can either be retained between two side plates (3, 4) that extend along the whole of the periphery of the wheel (1) or are retained on a casing (35) that extends between, and is fastened to, two side plates (3,4). The segments (10) are manufactured from extruded profiles that are cut to the right length. To ensure the correct positioning of the segments (10) they are loosely attached to the wheel (1), a toothed belt is placed around the toothed edge and the segments (10) are displaced to give a firm engagement with the toothed belt. Thereafter the segments (10) are fastened.

Description

Arrangement of a toothed belt wheel

The present invention relates to an arrangement of a toothed belt wheel and especially a toothed belt wheel with a large diameter, i.e. a diameter of 0.3 meters or more.

The toothed belt wheel is well suited to be used in a windmill, as shown in the previous Norwegian patent application no. 20090433 by the same applicant. This application is hereby incorporated by reference. The toothed belt wheel will in this context function as a belt wheel, with a belt or a chain stretching around it and forming an element for transfer of a rotation between the toothed belt wheel and another wheel.

Toothed belt wheels with a diameter of the order that is described above are difficult to manufacture in one piece. It would be very costly to both cast and to machine. It would also be very inappropriate to transport such a large wheel in one piece.

Toothed belt wheels require a large degree of accuracy to avoid wear and tear. In addition to these high tolerances a small gap is made between the toothed belt and the nominal wheel profile, i.e. that the teeth of the toothed belt are a few tenths of a millimetre smaller than what is stated for the toothed belt wheel profiles. If the wheel should be inaccurate there will be a disagreement between the toothed belt and the teeth on the wheel. This will result in considerable increased wear and low efficiency. Large belt wheels are manufactured today by machining materials made from cast iron or welded steel wheel materials. The machining gives a high degree of accuracy but also a high weight.

US 2707884 describes a tooth gear produced from a non-metallic material and shows segments of a gear rim, which is attached to a wheel with an outer edge. The segments are relatively long and are attached by means of bolts that are fixed to the segments by though-going pins extending in the transverse direction of the wheel.

If this wheel were to be produced in a large size and in metal, the wheel that carries the segments would most likely have to be cast and thereby it would be relatively heavy. Moreover, the shape of the segments is also so that they also most likely would have to be cast. All in all this would mean that there would be no actual weight savings relative to a wheel that is cast in one piece and thereafter machined. Moreover, there would be no savings in machining. This is probably why the technique is limited to non-metallic wheels. The only advantage achieved is that segments can be replaced if they are damaged.

US 3439551 shows a tooth gear which is produced by attaching segments to a single plate wheel. If the plate wheel is to be strong and stable enough, this will have to have a relatively thick wall thickness. Thereby the plate wheel will probably have to be cast and machined. The larger the wheel is to be, the more massive the material has to be, and the heavier the wheel will be. A heavier wheel does not only lead to disadvantages in installation and service, but also has operational disadvantages in the fact that larger forces are required to alter the rotational speed of the wheel and that it is more difficult to achieve a good balance in the wheel.

US 1433923 shows a toothed gear that in principle is similar to US 3439551 . This wheel is shown used in the chain drive of a bicycle, and it would probably not be suitable for much larger wheels than this.

SU 948441 describes a way of attaching toothed segments to each other at the adjoining ends. It is not shown how the segments may be attached to a wheel.

SU 1346890 also describes a way of attaching segments to each other at the adjoining ends. Here also it is not described how the segments may be attached to a wheel. There is therefore a need to provide a wheel of this type in several parts, which can be assembled to a stable wheel that can transfer large forces. There is also a need to provide assembly of the wheel parts that ensures that the wheel is sufficiently round and is sufficiently free from throws. There is also a need to design a method to manufacture a toothed belt wheel which ensures an accurate insertion of the teeth on the toothed belt wheel in relation to the teeth on the toothed belt so that unnecessary wear is avoided. Therefore, the present invention aims to provide such a toothed belt wheel.

This is achieved according to the present invention by the features that are given in the characterizing part of claim 1 .

Smaller belt wheels are sometimes cast in aluminium, especially if they are to be produced in large series, but large belt wheels have hitherto not been produced from aluminium. Aluminium is in itself not sufficiently hard and durable to be used for toothed wheel operation with modern Kevlar or carbon fibre belts, but there are several methods such as anodizing and other surface treatments that can give aluminium these characteristics.

The invention shall now be explained in more detail with reference to an example embodiment shown in the enclosed figures, where:

Figure 1 shows a toothed belt wheel according to one embodiment of the present invention seen in perspective,

Figure 2 shows the toothed belt wheel of figure 1 seen from the side, Figure 3 shows a section of the toothed belt wheel at its periphery, Figure 4 shows a section through the toothed belt wheel at its periphery, Figure 5 shows a section through the whole of the toothed belt wheel, Figure 6 shows a section through the hub of the toothed belt wheel,

Figure 7 shows an alternative embodiment of a toothed belt wheel segment according to the invention,

Figure 8 shows an alternative embodiment of a toothed belt wheel according to the invention,

Figure 9 shows a cross section through the toothed belt wheel in figure 8,

Figure 10 shows a further embodiment of a toothed belt wheel segment for use in a toothed belt wheel as shown in the figures 8 and 9,

Figure 1 1 shows a detail of the wheel in figure 8 with a segment according to figure 10,

Figure 12 shows a section of a belt wheel as shown in the figures 8 and 9 fitted with segments as shown in the figures 10 and 1 1 ,

Figure 13 shows a belt wheel according to the embodiment shown in the figures 1 and 2 that engages with a toothed belt,

Figure 14 shows a belt wheel according to the embodiment shown in the figures 1 and 2, and also a set of tools to position the segments correctly during the fitting, and

Figure 15 shows the belt wheel according to figure 15 but with the side plates removed.

Figure 1 shows a toothed belt wheel according to a preferred embodiment of the invention for narrow wheels. It comprises an edge 1 that extends along the periphery of the wheel and two disc-formed side plates 2, 3 one of which is arranged on each side of the edge 1 . The side plates 2, 3 are fitted with a brim 4 that extends along the edge 1 , spokes 5 that extend radially and connect the brim 4 with the hub part 6. The hub part 6 is fitted with an opening 7 where a coupling 8 is arranged. The side plates 2, 3 and the edge 1 are connected to each other by a number of bolts 9 that extend axially.

Figure 2 shows a section through the toothed belt wheel from the side. The edge 1 is composed of a number of segments 10 each of which cover an angle area of about, for example, 10°. The segments are appropriately extruded profiles.

Figure 3 shows a section through a part of the edge and illustrates a complete segment 10 and a part of the two adjacent segments 10' and 10". The segments are profiles that extend with the same cross section axially, i.e.

perpendicular to the plane of the drawing according to figure 3. The profiles are preferably manufactured from extruded metal, for example, aluminium, that is extruded in long profiles with the cross section of the segment 10.

The profile is thereafter cut into lengths corresponding to the width of the edgel . Alternatively the profiles can also be press cast.

The profile has an arched inside 1 1 and a corresponding arched outside 12. It is also shaped with an inner hollow space 13 to save on weight. The segment 10 may also have a U-shape. Ribs 14 are formed on the outside 12 that extend in the longitudinal direction of the profile, i.e. in the width of the toothed belt wheel. These ribs serve to achieve an accurate engagement between the toothed belt wheel and the outside lying belt (not shown).

At its short ends 15, 16, the segment 10 is formed for engagement with adjacent segments 10' and 10". Thus, a U-shaped groove 17 is formed at both the short ends 15 and 16, which extends in the longitudinal direction of the profile, i.e. in the width of the tooted belt wheel. Elevated sections 18, 19 on each side of the groove 17 are located at the one short end 15, and at the other short end there are recessed sections 20, 21 on each side of the groove 17. The elevated and the recessed sections are complimentary so that when two segments 10,10' are placed against each other the elevated sections 18, 19 will completely fill the recessed sections 20, 21 at the same time as the segments lie against each other on the surfaces 22, 23 outside these sections. The U-shaped grooves 17 on the two segments 10, 10' together form a circular channel. This channel is set up to receive one of the bolts 9 (see figure 1 ).

Figure 4 shows a cross section through the segment at the bolt 9. The figure also shows a section through the side plates 2, 3. Here one can see that the bolt 9 goes through the two side plates 2, 3 and the channel formed by the grooves 17. The segments 10 are thus held in place in the axial direction of the toothed belt wheel. Radially, the segments 10 are held in place by the bolts 9, friction from the side plates 3, 4 and the respective engagement from the elevated and recessed sections 18, 19, 20, 21 .

In practice it will not be possible to achieve the same degree of accuracy with aluminium extrusions as one will get with machining. To some extent one can compensate for this in the following way. One makes narrow tooth sections, for example, about 10-12 cm wide in total. Within this width, one has an extrusion process that is accurate enough and which one can work with. If the segments become considerably wider than this, the teeth will be standing inaccurately in relation to another. Teeth that are too far apart will gradually become less accurate in relation to each other and one risks that the teeth will not fit into the tooth belt over the whole section. Modern toothed belts have a carbon fibre core which makes them completely rigid. Even on 10-12 cm wide aluminium segments one must possibly compensate somewhat by removing some tenths of a millimetre of the aluminium on the outermost teeth in the segment. The middle teeth can beneficially be full size while those on the sides are gradually smaller. The width of the section and the teeth adjustment mentioned above ensure that the teeth of a section fit into the belt. So that several sections shall fit into the toothed belt one must ensure that the section can float somewhat during the fitting. Therefore, a small clearance is made between each segment. When the wheel is assembled, the segments are put in place and the bolts are partially fastened so that the segments can be moved a little. To ensure that the mutual positioning between the segments becomes correct one can place a toothed belt around the belt wheel when all the segments have been fitted. Thereafter, one can displace the segments so that all the segments fit optimally into the toothed belt. When this has been carried out the bolts are tightened to the right torque. The segments are held in place by the frictional force between the plate sides 2, 3 on the wheel and the end plates of the sections 10. This fitting method will demand high accuracy of the cutting length of the section. However, it is possible to achieve this with, for example, CNC cutting.

The fastening described above ensures that it is also very simple to replace individual segments. To do this one removes the bolts on each side of the segment that is to be replaced and loosens a number of bolts at each side of this segment. The segment 10 which shall be replaced can then be pressed outwards. The adjacent segments 10', 10" will swing outwards with the side which is nearest the segment 10 that shall be replaced until the segment 10 which shall be replaced goes clear of the elevations/recesses of the adjacent segments 10' 10". The insertion of a new segment takes place in the same way.

This shaping of segments 10 ensures that the edgel of the toothed belt wheel has a defined circular shape. When the toothed belt wheel is exposed to pressure from the belt, the segments 10 will be held in place by the frictional forces between the side plates 2 and the segments 10. Figure 13 shows a wheel according to this embodiment engaging with a toothed belt 42.

Figure 5 shows a cross section through the toothed belt wheel. A clamp connection 8 is fitted centrally in the wheel. The clamp connection 8 is shown in more detail in figure 6. It comprises a casing 24 which has a middle section 25 with a larger diameter and axially protruding sections 26, 27 at each end of the middle section 25. Thus, there is a shoulder 28 on each side of the middle section 25. The side plates 2, 3 will, after the fitting, be lying against these shoulders 28 and thereby clamps the casing 24.

A clamp connection 30 is fitted inside the casing 24 for fitting of the wheel on a shaft.

Figure 7 shows an alternative embodiment of a toothed belt segment 10a. It is primarily formed in the same way as segment 10 in figure3, but has a somewhat different interface between the segments. Instead of the elevated sections 18, 19 and the recessed sections 20, 21 , a rib 31 and a groove 32 are formed. The rib 31 is somewhat smaller than the groove 32 so that there will be a small clearance between these. The rib 31 and the groove 32 can thereby be used as guides to place the segments in relation to each other. Beyond this the segments are fitted and adjusted as explained above in connection with the embodiment according to figure 3.

The figures 14 and 15 show a tool set for the positioning of the segments 10 during fitting. The only difference in figures 14 and 15 is that in figure 15 the side plates 3 and 4 are removed so that it is easier to see the tool.

The tool set 43 encompasses two parts, a fitting aid 44 and an outer locking bracket 45. The aid 44 has an arched edge 46 with a radius corresponding to the wanted inner radius of the segments 10. Opposite to the arched edge 46 a lip 47 is formed that shores up the aid 44.

The locking bracket 45 has a general U-shape. A notch 49 is formed in each leg 48. The notch 49 is set up to receive the end of the bolt 9. During the fitting of the segments 10, one of the side plates 3 is first placed on a base. The segments 10 are thereby placed in the approximate correct position on the side plate 3. Then, the other side plate 4 is placed on top of the segments. When this has been completed the bolts 9 are put through the channels that are formed by the grooves 17. Thereafter, a toothed belt 50 is placed around the segments. The toothed belt 50 has a length corresponding to the circumference of the belt wheel 1 . The belt 50 is placed so that the teeth of the toothed belt 50 engage with the teeth of the segments. Where the ends of the toothed belt meet, the locking bracket 45 is used to lock the ends of the toothed belt 50 to the segments 10. This is carried out in that the locking bracket 45 is threaded over the segments 10 and one of the bolts 9. The nuts are then screwed onto each end of the bolts 9 so that the bracket is clamped fast. The other nuts are screwed on loosely at this time. The aid 44 is led along the inside of the segments 10 so that the segments are made to form a sufficiently round circle. Thereafter, all the nuts are tightened on the bolts 9. Finally, the locking bracket 45 is removed by loosening the nuts that hold this in place and tightening the nuts after the bracket has been removed.

The figures 8 and 9 show an alternative embodiment of the toothed belt wheel 1 . This wheel comprises side plates 2, 3, but is also fitted with two gables 33, 34 that are placed inside the side plates 2, 3. A cylindrical drum casing 35 is placed between the side plates. The side plates 2, 3 extend radially somewhat out over the drum casing, while the gables 33, 34 lie against the inside of the casing 35. The side plates 2, 3 and the gables are preferably welded to the casing 35.

The side plates can also be replaced by struts or spokes. For small wheels, one can also visualise a casing carrying structure under the middle of the casing. This can be, for example, a cast or a welded structure. It is also possible to produce the casing carrying structure in one piece with the casing, for example, by pressing (in the way that steel rims for cars are manufactured) or by casting. For this embodiment, an alternative fastening method is used to secure the segments. The casing 35 is fitted with a pattern of holes 36 that extend axially in several rows. These holes are used to fasten the segments to the casing 35 as will be explained below.

Figure 10 shows a segment 10b. The segment 10b has a general square cross section with a dovetail groove 37 on the underside. On the sides that shall face the adjacent segments, the segment 10b has either a recess 38 or an elevation 39. These are complimentary.

Before the segment 10b is fitted, bolts with an edged head or nuts are inserted into the dovetail groove 38. The segment 10b is fitted across the casing 35, as shown in figure 1 1 so that the bolts or the nuts in the dovetail groove 38 lie level with the holes 36 in an axial row of holes. If bolts are placed in the dovetail groove 38, the stem of the bolts is inserted through the holes 36 and a nut is screwed onto each bolt from the underside of the casing 35.

If nuts 40 are placed in the dovetail groove, bolts 41 are inserted from the underside of the casing 35 through the holes 36. The latter is shown in figure 12.

This way of fastening the segments is most relevant for long profiles. Long profiles will lead to a need to distribute the load transmission to the whole of the wheel and not just to the end plates. When the segments are fastened to the cylinder plane in this way, one can allow for less accuracy on the lengths of the segments.

The segments are positioned before they are secured in principally the same way as for the previously described fastening method.

Claims

1.

Arrangement of a toothed belt wheel comprising a toothed rim (1) at the periphery of the wheel, the rim (1 ) being composed of a number of segments (10) that are retained in relation to each other in a circle,

ch a racteri sed i n that the segments are securely clamped between two side plates (2, 3) that extend along the whole of the periphery of the wheel.

2.

Arrangement according to claim 1, ch a racteri sed i n that the side plates (2, 3) extend from the periphery of the wheel to its hub.

3.

Arrangement according to one of the preceding claims, ch a racteri sed i n that the segments (10) are manufactured from a long profile which is cut in lengths corresponding to the width of the segments (10) in the axial direction of the toothed belt wheel.

4.

Arrangement according to claim 3, characterised in that the profile is an extruded profile.

5.

Arrangement according to claim 3, ch a racteri sed i n that the profile is manufactured by press casting.

6.

Arrangement according to one of the preceding claims, characterised i n that the segments (10) at their opposite ends have a U-shaped groove (17) which, together with the U-shaped groove (17) on the adjacent segment, form a circular channel for a through-going bolt (9) that extends through the side plates (2, 3) and the circular channel and clamps the side plates (2, 3) against the segments (10).

7.

Arrangement according to on of the preceding claims, characterised in that the segments (10) at their opposite ends have elevations (18, 19) and/or recesses (20, 21) that fit complimentary into one another.

8.

Arrangement according to one of the preceding claims, characterised i n that the side plates (2, 3) are set up to retain a hub casing (24) between them.

9.

Arrangement according to claim 8, characterised in that the hub casing (24) has a shoulder (28) which the side plate (2, 3) is set up to lie against and a section (26, 27) that stretches axially from the shoulder (28) and extends through an opening in the side plate (2, 3).

10.

Arrangement according to one of the preceding claims, ch a racteri sed i n that the toothed belt wheel is set up to engage with a belt (50) or a chain that runs over a part of the periphery of the toothed belt wheel.

11.

Arrangement according to one of the preceding claims, ch a racteri sed i n that the segments (10) are fitted with teeth (12) to engage with a toothed belt (50) and that the teeth (12) have a decreasing width from the middle of the segment (10) to the outermost edge of the segment (10) in the peripheral direction. Method to position segments (10) on a toothed belt wheel as defined in one of the claims 1 -11, characterised in that the segments (10) are fitted to the plates (2, 3) in such a way that they are able to move, a toothed belt is placed around the periphery of the wheel, the segments (10) are displaced until the teeth (12) of all the segments (10) engage well with the toothed belt and that the segments (10) are thereafter tightened in relation to each other.

13.

Method according to claim 12, ch a ra cteri sed i n that the fixation is made by tightening bolts (19) that connect the segments (10) to the side plates (2, 3).

14.

Method according to claim 12 or 13, ch a ra cterised i n that a fitting gauge (44) with an arched edge (46) corresponding to the targeted internal radius of the segments (10) is placed against the inside of the segments (10) before the segments (10) are fixated.

15.

Tool for fitting segments in accordance with the method according to one of the claims 12-14, ch a racte ri sed i n that it comprises a toothed belt (50) adapted to be placed around the segments (10) and a locking device (50) to lock ends of the toothed belt (50) to the segments (10).

16.

Tool according to claim 15, ch a racteri sed i n that it also comprises a fitting gauge (44) with an arched edge (46) corresponding to the target internal radius of the segments (10).