BURSTRÖM, Lennart (Hantverkargatan 10, Nordmaling, S-914 31, SE)
| A track section adapted to be linked to a plurality of similar track sections to form a flexible track belt for mounting around the outer periphery of vehicle tyres, wherein the track section comprises a crossbar member (1 1 ) and two lateral support members (1 2) mounted to the crossbar member (1 1 ) at opposite ends thereof, the support members ( 12) protruding on the same side of the crossbar member (1 1 ) and being spaced apart to allow a tyre to be received between the support members (1 2) with the crossbar member ( 1 1 ) extending across the envelope surface of the tyre and with the support members (1 2) facing a respective one of the two opposed sidewalls of the tyre, each support member (12) having a first side (15) facing the other support member and an opposite second side ( 16) facing away from the other support member, a support surface (1 7) being provided on said first side (1 5) of the respective support member for engagement with the outer surface of a tyre received between the support members, characterized in : - that at least one of the support members (12), preferably both of them, has an inner stem part (18), through which the support member ( 12) is connected to the crossbar member (1 1 ), and an outer head part (19), which is connected to the stem part (18) and which is wider than the stem part as seen in a direction (D 1 ) corresponding to the longitudinal direction of the track belt; and - that the support surface (1 7) of said at least one support member bulges laterally in opposite directions at the part of the support member where the stem part (18) meets the head part (19), so as to form a support surface section (1 7a) on the head part (19) which is wider than an adjacent support surface section (1 7b) on the stem part (1 8) as seen in said direction (D 1 ). A track section according to claim 1 , characterized in , that the stem part ( 18) of said at least one support member has a U-shaped cross-sectional shape, the open side (21 ) of the stem part ( 18) facing away from the other support member and the opposite closed side (22) of the stem part facing the other support member. A track section according to claim 2, characterized in , that the stem part (1 8) has two essentially parallel lateral walls (23, 24) extending at a distance from each other and an intermediate wall (25) extending between the lateral walls on said closed side (22) of the stem part, said narrower support surface section (1 7b) being provided on this intermediate wall (25). A track section according to any of claims 1 -3, characterized in , that the head part ( 19) of said at least one support member is hood-shaped with an open side (26) facing away from the other support member and an opposite closed side (27) facing the other support member, said wider support surface section (1 7a) being provided on this closed side (27). A track section according to any of claims 1 -4, characterized in that the support surface (1 7) of said at least one support member is inclined away from the other support member as seen in the direction from the inner end of the support surface towards the outer end thereof. A track section according to any of claims 1 -5, characterized in that said at least one support member (12) is formed by deep drawing of a blank of steel sheet having a thickness of 6- 1 2 mm , preferably 7-9 mm. A method for producing a support member for a track section according to any of claims 1 -6, characterized in that a blank (40) of steel sheet having a thickness of 6-12 mm, preferably 7- 9 mm, is subjected to deep drawing so as to thereby form the support member (1 2). 8. A method according to claim 7, characterized in that the blank (40) is cut out from a steel sheet having a thickness of 6-1 2 mm , preferably 7-9 mm. 9. A method according to claim 7 or 8, characterized in that the blank (40) is heated before and/or during the deep drawing to a temperature of 900- 1200°C. 10. A method according to claim 9, characterized in that the formed support member (12) is quenched by being immersed in a quenching medium. |
The present invention relates to a track section according to the preamble of claim 1 , which is adapted to be linked to a plurality of similar track sections to form a flexible track belt for mounting around the outer periphery of vehicle tyres. The invention also relates to a method for producing a support member for such a track section .
Track belts which may be removably mounted around tyres of vehicles are known in several different designs. Such a track belt can be used in order to obtain better friction and traction between the vehicle tyres and the ground for a vehicle, particularly on wet, slippery or muddy terrain , or in order to increase the carrying capacity of a vehicle.
A track section according to the preamble of claim 1 is previously known from WO 99/37525 A1 .
OBJECT OF THE I NVENTION
The object of the present invention is to provide a track section of the above-mentioned type having a new and favourable design . SUMMARY OF TH E I NVENTI ON
According to the invention , said object is achieved by a track section having the features defined in claim 1 . The track section according to the invention comprises a crossbar member and two lateral support members mounted to the crossbar member at opposite ends thereof, the support members protruding on the same side of the crossbar member and being spaced apart to allow a tyre to be received between the support members with the crossbar member extending across the envelope surface of the tyre and with the support members facing a respective one of the two opposed sidewalls of the tyre. Each support member has a first side facing the other support member and an opposite second side facing away from the other support member, a support surface being provided on said first side of the respective support member for engagement with the outer surface of a tyre received between the support members. At least one of the support members, preferably both of them, has an inner stem part, through which the support member is connected to the crossbar member, and an outer head part, which is connected to the stem part and which is wider than the stem part as seen in a direction corresponding to the longitudinal direction of the track belt. The support surface of said at least one support member bulges laterally in opposite directions at the part of the support member where the stem part meets the head part, so as to form a support surface section on the head part which is wider than an adjacent support surface section on the stem part as seen in said direction .
Owing to the fact that the head part is wider than the stem part, a widened support surface section can be provided on the head part without increasing the width of the inner part of the support member through which the support member is connected to the crossbar member. An increased width of said inner part of the support member would give an increased width of the track section and thereby a larger distance between the crossbar mem- bers of the track belt formed by several interconnected track sections, which in its turn could reduce the efficiency of the track belt. With the solution according to the present invention , the support member can be given an increased support surface area without increasing the width of the track section and without in- creasing the height of the support member. An increased support surface area will give an increased area of the contact surface between the support member and the tyre and thereby a reduced surface pressure on the tyre from the support member, which in its turn will reduce the wear on the tyre caused by the support member. According to an embodiment of the invention , said at least one support member is formed by deep drawing of a blank of steel sheet having a thickness of 6- 12 mm, preferably 7-9 mm. Hereby, the support member can be produced in a quick, simple and cost- effective manner.
Further advantages as well as advantageous features of the track section according to the invention will appear from the following description and the dependent claims. The invention also relates to a method for producing a support member for a track section , wherein a blank of steel sheet having a thickness of 6-1 2 mm, preferably 7-9 mm, is subjected to deep drawing so as to thereby form the support member. With the method according to the invention , the support members can be produced in a quick, simple and cost-effective manner.
According to an embodiment of the invention , the blank is heated before and/or during the deep drawing to a temperature of 900- 1200°C. Hereby, the deep drawing of the blank is facilitated .
Further advantages as well as advantageous features of the method according to the invention will appear from the following description and the dependent claims.
BRI EF DESCRI PTION OF THE DRAWI NG
With reference to the appended drawing , a specific description of preferred embodiments of the invention cited as examples follows below. In the drawings: is a perspective view of a track section according to an embodiment of the present invention , is a lateral view of the track section of Fig 1 , shows a part of the track section of Fig 1 , as seen from one end of the track section ,
Fig 4 is a perspective view of a support member included in the track section of Fig 1 ,
Fig 5 is a perspective view of the support member of Fig 4, as seen from the rear side, Fig 6 is a rear view of the support member of Fig 4,
Fig 7 is a lateral view of the support member of Fig 4,
Fig 8 shows a part of a track belt formed of interconnected track sections of the type illustrated in Figs 1 -3, with the track belt mounted around the outer periphery of vehicle tyres, and
Figs 9a-d schematically illustrates different steps in a method for producing a support member of the type illustrated in Figs 4-7.
DETAI LED DESCRI PTI ON OF PREFERRED EMBOD I MENTS OF THE I NVENTION
A track section 10 according to an embodiment of the present invention is illustrated in Figs 1 -3. This track section 10 is to be linked to a plurality of similar track sections to form a flexi ble track belt 1 (see Fig 8) for mounting around the outer periphery of vehicle tyres. The track section 10 comprises an elongated crossbar member 1 1 and two lateral support members 12 mounted to the crossbar member 1 1 at opposite ends thereof. The crossbar member 1 1 has an essentially smooth inside 13 for engagement with the envelope surface 2 of a vehicle tyre 3. I n order to improve the grip against the ground , one or more gripping pegs 14 may be provided on the outside of the crossbar member 1 1 , as illustrated in Figs 1 and 2. I n the illustrated embodiment, the crossbar member 1 1 is formed by an elongated rigid beam having an essentially T-shaped cross-sectional shape. However, the crossbar member 1 1 may have any other suitable design .
The support members 12 protrude on the inside 13 of the crossbar member 1 1 . The support members 1 2 are spaced apart to allow a tyre 3 to be received between the support members 12 with the crossbar member 1 1 extending across the envelope surface 2 of the tyre 3 and with the support members 12 facing a respective one of the two opposed sidewalls 4 of the tyre, as illustrated in Fig 2, where the lower part of a tyre 3 is illustrated in broken lines. Each support member 12 has a first side 15 facing the other support member and an opposite second side 16 facing away from the other support member. A support surface 1 7 is provided on said first side 15 of the respective support member for engagement with the outer surface of a tyre 3 received between the support members 1 2. The design of the support members 12 is shown in closer detail in Figs 4-7. The respective support member 12 has an inner stem part 18, through which the support member 12 is connected to the crossbar member 1 1 , and an outer head part 19, which is connected to the stem part 18 and which is wider than the stem part as seen in a direction D 1 corresponding to the longitudinal direction of the track belt 1 to be formed by a number of interconnected track sections 10, i .e. the intended running direction of the track belt. This direction D 1 is indicated by an arrow in Figs 4 and 6. The support surface 1 7 of the support member bulges laterally in opposite directions at the part 20 of the support member where the stem part 18 meets the head part 19, so as to form a support surface section 1 7a on the head part 19 which is wider than an adjacent support surface section 1 7b on the stem part 1 8 as seen in said direction D 1 .
The stem part 18 of the respective support member 1 2 has a U- shaped cross-sectional shape. The open side 21 of the stem part 18 faces away from the other support member, whereas the opposite closed side 22 faces the other support member. The stem part 18 has two essentially parallel lateral walls 23, 24 extending at a distance from each other and an intermediate wall 25 ex- tending between the lateral walls on said closed side 22 of the stem part. The above-mentioned narrower support surface section 1 7b is provided on the intermediate wall 25.
The head part 19 of the respective support member 1 2 is hood- shaped with an open side 26 facing away from the other support member and an opposite closed side 27 facing the other support member. The above-mentioned wider support surface section 1 7a is provided on said closed side 27. The respective support member 12 can be said to be scoop- shaped and has a rim 28 formed by the essentially straight edge 28a of the first lateral wall 23 of the stem part, the arc-shaped edge 28b of the head part 1 9 and the essentially straight edge 28c of the second lateral wall 23 of the stem part.
The support surface 1 7 of the respective support member 1 2 is inclined away from the other support member as seen in the direction from the inner end of the support surface towards the outer end thereof, as illustrated in Figs 2 and 7.
In the illustrated example, the respective support member 12 is secured to an end of the crossbar member 1 1 through a C- shaped connection member 29, a so-called link hook, which is secured to the crossbar member 1 1 by welding . The stem part 1 8 of the support member 1 2 rests against a base part 30 of the connection member 29 through the inner edges of the lateral walls 23, 24 and is secured to this base part 30 by welding . A first end 31 of the connection member 29 is secured to a first lateral wall 23 of the stem part 1 8 by welding and the other end 32 of the connection member 29 is secured to the other lateral wall 24 of the stem part 18 by welding . Hereby, a first opening 33 for receiving a first link element 35 is formed on a first side of the support member 1 2 between the first lateral wall 23 of the stem part 1 8 and the connection member 29 and a second opening 33 for receiving a second link element 35 is formed on the opposite side of the support member 12 between the other lateral wall 24 of the stem part 18 and the connection member 29.
Several track sections 1 0 of the type descri bed above are interconnected by means of link elements 35 to form a flexible track belt 1 , as illustrated in Fig 8. The respective link element 35 is received in an opening 33 of a connection member 29 of a first track section 10 and in an opening 33 of a connection member 29 of another adjacent track section 10. The link elements 35 will act as hinges between the track sections 10. The track section 1 is mounted around the outer periphery of two or more vehicle tyres 3 with the crossbar members 1 1 extending in the cross-direction of the tyres and with the support members 12 facing the tyres, as illustrated in Fig 8. The support members 12 will keep the track belt 1 correctly positioned on the tyres 3 and will prevent the track belt 1 from slipping of the tyres 3. At the part of a tyre 3 that bears against the ground , the opposed sidewalls 4 of the tyre will bulge due to the load from the vehicle and the side- walls 4 will thereby come into contact with the support surfaces 1 7 of the two opposed support members 1 2 of a track section 10 received between the tyre 3 and the ground , as illustrated in Fig 2.
The respective support member 1 2 is formed by deep drawing of a blank 40 of steel sheet. The blank 40 is formed by being cut out from a steel sheet having a thickness of 6-12 mm , preferably 7-9 mm. The blank 40 is heated before and/or during the deep drawing to a temperature of 900-1200°C. Different steps in a deep drawing process for forming a support member 12 of the type described above are illustrated in Figs 9a- 9d . In a first step, a blank 40 having a thickness of 8 mm and heated to a temperature of approximately 950°C is placed on the upper end of a punch 41 with the edges of the blank resting against a lower die 42, as illustrated in Fig 9a. A holding member 43 is pressed against the upper surface of the blank 40 in order to keep the blank in place on the punch 41 . Thereafter, an upper die 44 is pressed against the edges of the blank 40 and against the lower die 42 (see Fig 9b) so as to shape the edges of the blank and give these edges a somewhat rounded shape. The lower die 42 is then lowered and moved away from the upper die, as illustrated in Fig 9c, whereupon the upper die 44 is moved downwards in relation to the punch 41 so as to su bject the blank 40 to deep drawing for the final shaping of a support member 12 having the design described above. Thereafter, the upper die 44 and the holding member 43 are moved upwards away from the support member 1 2 and the punch 41 , and the lower die 42 is moved upwards in relation to the punch 41 in order to push the support member 12 upwards and thereby release the support member 12 from the punch 41 , as illustrated in Fig 9d . The support member 12 is finally quenched by being immersed in water or any other suitable quenching medium. The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to modifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention such as defined in the appended claims.