GB2130535A

GB2130535A - Solid tire with removable tread

Info

Publication number: GB2130535A
Application number: GB08326002A
Authority: GB
Inventors: Pierre Pringiers
Original assignee: Bergougnan Benelux SA
Current assignee: Bergougnan Benelux SA
Priority date: 1982-10-12
Filing date: 1983-09-28
Publication date: 1984-06-06
Also published as: GB8326002D0; FR2534191A1; IT8368051A0; JPS5984605A; IT1161510B; NL8303294A; FR2534191B1; DE3335899A1; SE8305308L; BE897951A; CA1206080A; GB2130535B; LU84420A1; DE3335899C2; IT8353812V0; SE8305308D0

Abstract

The tire comprises a removable tread 5 mounted on a resilient tire strip (1) comprised of two co-axial ring-shaped parts (2,3) with different hardnesses and elasticity modulus and having a resilient elongation factor comprised between 1.03 and 1.08. The inner bead part (3) may have an elasticity modulus between 7 N/mm<2> (+/- 70 DEG Sh) and 15 N/mm<2> (+/- 95 DEG Sh), or be of rubber filled with fibres of length 5-20 mm or comprise, as shown, rubber layers of 55 DEG -75 DEG shore hardness alternating with fabric layers (13). The tire strip body part (2) may have an elasticity modulus between 3 N/mm<2> (+/- 40 DEG Sh) and 10 N/mm<2> (+/- 80 DEG Sh). The tread (5) is a rubber or polyurethane ring which is substantially inextensible e.g. by virtue of reinforcement (6) and has an inner diameter which is slightly larger than the outer diameter of the tire strip (1) before it is mounted on a wheel, and slightly smaller than the said outer diameter when the tire strip is mounted but before the tread ring (5) is added. To mount the tire, the tread (5) is first slipped over the tire strip (1) which is then forced on to the rim using a press and a conical guide device. In a variation, fastening of the tread is achieved by a flexible circumferential side edge on the tread of the tire strip. <IMAGE>

Description

SPECIFICATION Solid tire from rubber or similar, with removable tread This invention relates to a solid tire from rubber or similar, with removable tread, to be used notably on wheels for handling trucks or other similar industrial vehicles.

Vehicles of this kind are generally fitted with solid tires rather than with inflated tires as used for road vehicles, on the one hand due to the indifference of such solid tires to cuts and punctures, and on the other hand due to the relatively high radial stiffness thereof which insures a low collapsing under even high loads.

Such solid tires are however rather costly as they comprise more rubber or similar material than a pneumatic tire. Moreover the stiffness of such solid tires results in the tires becoming substantially integral with the rim thereof, in such a way that the mounting and disassembly of such tires has generally to be made in the works.

To lower as far as possible the cost of such solid tires, it has been conceived to bring on the market solid tires with removable tread.

Consequently, when said tread is worn-down, it is only required to substitute a new tread thereto.

However such solid tires with removable treads are subjected to relatively drastic requirements to insure the fastening and retaining in position of said tread over the tire elastic body.

In solid tires of this type as known up to now, there is a danger that after some period of use the tread will separate from the tire body. Moreover some play may form between the rim or wheel and the tire bead when the tire is subjected to a relatively high load, which causes sliding between the tire and the rim or wheel.

Some known tires with removable tread have an inner hollow groove with the purpose of giving some flexibility to the tire. However the fastening of a hollow-core tire to a rim does not allow the tire to be subjected to high side stresses and results in a danger of bead release and displacement of the tread.

Other known tires comprise a removable tread which is secured or vulcanized on a metal hooping, which is secured in turn to the tire body by hooping over another metal hoop encircling the tire body. Manufacturing of such tires is costly and intricate.

In still other tires, the removable tread is retained on the tire body by air pressure inside a center ring-shaped chamber. Such a method is also rather intricate and relatively unreliable.

This invention has essentially for object to obviate said drawbacks and to provide a solid tire with removable tread with a simple structure which does however become substantially integral with the tire while being removable after being worn-down.

For this purpose according to the invention, the tire comprises a substantially resilient tire strip comprised of two co-axial ring-shaped parts with different hardnesses and elasticity modulus and having a resilient elongation factor comprised between 1.03 and 1.08, an inner part comprising the bead for cooperating with the rim or wheel and having an elasticity modulus comprised between 7 N/mm2 ( + 70 Sh) and 1 5 N/mm2 (+ 95 Sh), a second part comprising the tire strip body having an elasticity modulus lower than the elasticity modulus of the bead and comprised between 3 N/mm2 (+ 40 Sh) and 10 N/mm2 (+ 80"Sh), the tread being comprised of a ring which is substantially extensible in the radial and circumferential direction and having an inner diameter which is slightly larger than the outer diameter of the tire strip before being laid over a rim or wheel, and slightly smaller than the outer diameter of the tire strip as laid without the tread over a rim or wheel.

Advantageously, the tread is reinforced with a ring-shaped reinforcement extending adjacent to the inner surface of said tread, to be fitted on the tire strip.

The invention further relates to a method for mounting and assembling said tire.

Such method comprises first sliding the tread over the resilient tire strip and then forcing the resilient tire strip provided with the tread thereof over the rim or wheel by means of a guide device with cone-shaped surface, fitting sidewise against the rim or wheel, and a press acting sidewise on the tire bead as engaged on the guide device.

Other details and features of the invention will stand out from the following description given by way of non limitative example and with reference to the accompanying drawings, in which: Figure 1 is a cross-section along a radial direction of part of a tire before mounting thereof over a rim or wheel.

Figure 2 shows said tire as mounted over a rim.

Figure 3 is a circumferential section through part of a variation of the tire according to the invention.

Figure 4 is a diagrammatic showing of the assembly and mounting of a tire over a rim.

In the various Figs. the same references pertain to similar elements.

The tire as shown in Figs. 1 and 2 comprises a substantially resilient tire strip formed by two co-axial ring-shaped parts 2 and 3 with different hardness and elasticity modulus, and having a resilient elongation factor comprised between 1.03 and 1.08. By resilient elongation factor is meant in the present description, the ratio between the maximum tire diameter under the action of a resilient distortion and the tire diameter before being distorted.

The inner part 3 comprises the bead which will cooperate with a rim or wheel 4 and has advantageously an elasticity modulus higher than the elasticity modulus of the second part 2 comprising the tire strip body.

More particularly, the elasticity modulus of the bead 3 lies between 7 N/mm2 ( + 70 Sh) and 1 5 N/mm2 (i 95 Sh), while the elasticity modulus of the tire strip body 2 lies between 3 N/mm2 (+ 40 Sh) and 10 N/mm2 (e 80 Sh).

Said tire comprises moreover a removable tread 5 formed by a ring which is substantially unextensible in the radial and circumferential direction of the tire. Said tread has an inner diameter which is slightly larger than the outer diameter of the tire strip before laying same over the rim or wheel 4, and slightly smaller than the outer diameter of the tire strip 1 as laid without tread over said rim or wheel. Such difference in relative diameter is a function of the nature of that material the tire strip and tread are made of, as well as of the shape and size of the tire components.

In the embodiment as shown in the figures, the tread is reinforced with a ring-shaped armouring or reinforcement 6 extending adjacent the inner surface 7 from said tread which will fit over the tire strip 1.

Said reinforcement is formed by wire cables extending substantially along the circumferential direction of the tread.

In an actual embodiment, said reinforcement is formed by a ribbon inside which a plurality of cables extend next to one another along the lengthwise direction of the ribbon, said ribbon extending helix-like about the center axis of the tread 5. This thus comprises a practical means for laying cables inside the tread.

The tire strip body 1 is made from vulcanizable or thermoplastic rubber with a Shore hardness comprised between 40 and 80 and advantageously with a hardness about 60 Shore.

The bead of the tire strip body is on the other hand harder to withstand the friction and crumbling caused by the rim or wheel 4.

To obtain such hardness of the bead, various solutions may be considered according to the invention: 1" -- using a hard rubber vulcanizable mix from 70 to 95 shore; 2' - using a rubber filled with relatively short textile fibers or similar, notably in the range from 5 to 20 mm; 3' - forming the bead from a compound material formed by fabric layers alternating with layers of a rubber with a 55 to 75 Shore hardness.

The outer surface 8 of the tire strip 1 and the inner surface 7 of the tread 5 to be fitted over said outer surface 8 are thus substantially of cylinder shape. This is a manufacturing advantage and allows mostly to provide for a minimum difference between the inner diameter of the tread 5 and the outer diameter of the unextended tire strip 1. It is sufficient for the play between the tread and the tire strip to be exactly large enough to allow sliding of the one over the other.

In this way, the expanding of the resilient tire strip 1 resulting from the mounting on the rim or wheel 4 may be minimized accurately to obtain locking of the thread 5 over such tire strip.

However it may be useful in some cases to increase the contact area between the tire strip body 1 and the tread 5. For this purpose according to the invention, on the respective contact surfaces 7 and 8 are advantageously provided complementary grooves and ribs which are preferably directed cross-wise along the tire axis.

Other interlocking means might possibly be provided to increase the adherence between both said surfaces.

Another substantial feature of the tire according to the invention lies in the tire strip body 1 having a cross-wise narrowing in a location between bead 3 and the contact surface 8 thereof with the tread 5.

As shown in Figs. 1 and 2, such narrowing is advantageously obtained by providing concace side walls 2a and 2b on the tire body 2.

On the other hand, depending on the nature and composition of that material the bead 3 and the body 2 of the tire strip 1 are made of, that zone 10 from bead 3 which will project from the receiving groove 11 provided on the circumference of the wheel or rim 4 is advantageously wider than the zone of the tire strip adjacent the contact surface 8 thereof with the tread 5.

Such particular shapes allow to influence the relative elasticity of the various components.

Such relative elasticity comprises indeed a very important factor for the mounting and fastening of the tread 5 to the tire strip 1 and for the adherence of the bead 3 on the rim, mostly under relatively high loads.

It is indeed indispensable for the elasticity modulus and the hardness of the bead to be higher than the elasticity modulus and the hardness of the tire strip body 2.

As already mentioned above, the invention further pertains to a method for mounting and assembling the above-described tire, which has for main advantage that due to the method simplicity, such assembling, mounting and disassembling of the tire may be performed by untrained workers and without requiring a costly or intricate equipment.

For this purpose, as it appears clearly from Fig. 4, the tread 5 is first slipped over the resilient tire strip 1 and said tire strip 1 fitted with the tread 2, is then forced over the rim or wheel 4 through a guide device 1 2 with cone-shaped surface fitting side-wise against the rim or wheel and a press not shown in the Figs, acting side-wise on bead 3 on that side opposite the side which is engaged on the guide device 12.

An actual embodiment of a tire according to the invention is given hereinafter to further show the essential features thereof.

The tire being considered is a 700 x 1 2 tire comprised of a replaceable tread 5 from a rubber which withstands abrading at 69 Shore, of a tire strip body 2 comprising a layer from resilient rubber with a hardness of 58 Shore, and of a bead 3 comprising layers from rubber at 62 Shore, with a thickness of 2 mm, alternating with fabric layers 1 3.

The tread 5 comprises adjacent the contact 7 thereof, a layer of brass-plated wire cables 6 of 7 X 4 X 0,175 adhering to the rubber and having a strength of 1800 N/cable, the cables being five in number per cm width.

The fabric layers 1 3 have a strength in the warp and weft directions of 800 N/cm.

The sizes of the tread, the tire strip and the corresponding rim have been shown with reference numerals in Fig. 4 and are to be found in the following table: Tread (mm) Tire strip (mm) Rim 500-12 (mm) D1= 577.3 D2= 286.3 D4= 301.3 L, = 141 D3= 574.3 L3= 127 E,= 48 L2= 133 E2= 3 E3= 65 The tire strip 1 thus has to have a resilient elongation factor of at least 1.05 (D4/D2 = 301.3/286.3 = 1.05).

When mounting the tire on rim 4, the following remarks may be made: -the inner diameter D2 from tire strip 1 increases from 286.3 mm to 301.3 mm, that is by 15 mm; -the outer diameter D3 from tire strip 1 increases from 574.3 mm to 589.3 mm, that is also by 1 5 mm (without tread); when the radial extension of the tread is considered as to be neglected, when such tread has been slipped over the tire body 2 before mounting the tire over the rim, the increase in length of diameter D3 is limited to the length of diameter D1, that is to 577.3 mm instead of 589.3 mm without tread; -the specific pressure thus obtained due to such limitation, on the contact surfaces 7 and 8 between the tread and the resilient tire strip is 0.25 MPa.

It has moreover been noticed that after the tread being worn-down, the outer diameter D3 of the tire strip increases up to 575 mm after removing the tire from the rim and removing the worn tread.

This allows to conclude that said tread replacing may be made without any problem and the new tread will still be fitted with enough pressure over the resilient tire strip.

The rim 4 may have the type as shown in Fig, 2, which is comprised of two parts 4a and 4b assembled together along the middle plane by means of bolts 4c to form a rim with a well 11 having a flat bottom or a slightly cone-shaped bottom extended on either side by raised edges.

Said rim may also have the type shown in Fig. 4 and comprises a removable edge 14 retained inside a groove 1 5 by a locking ring 16.

Said edge 14 and locking ring 1 6 have been shown in dotted lines, as said elements are only located on the rim after assembling the tire thereon.

In the same way as bead 3, the body 2 of tire strip 1 may be made either from homogeneous rubber, or with a reinforcement by flexible elements not shown in the figures, which may be nested therein as far as said elements do not hamper the radial and circumferential extension of the tire strip in the required proportion to obtain locking of the removable tread on the contact surface thereof.

The tread 5 is comprised of a rubber or polyurethane ring for example, having good wear resistance, which is made unextensible in the radial and circumferential direction by means of a ring-shaped armouring or reinforcement 6, as already mentioned above.

Such reinforcement is flexible and preferably comprised of a wire cable web extending along a circumferential direction as already mentioned above also : said cable web may be nested inside a rubber ribbon 9.

However it might be useful in some cases to use a web from textile cables or else a plurality of webs from textile or wire cables, which are superimposed and so arranged as to have the super-imposed cables crossing symmetrically relative to the middle plane while forming therewith a relatively small angle.

Moreover instead of cables, use might also be made of other reinforcing means fulfilling the same purpose as said cables, such as a layer from rubber having a very high elasticity modulus or filled with fibers, or else a ring from plain or perforated flexible metal sheet, etc.

Another variation which might be considered to insure fastening of the tread on the tire strip body, lies in providing either on the tread or on the tire body, a circumferential side edge which is preferably relatively flexible to make mounting and disassembling the tread easier.

It must be understood that the invention is in no way limited to the above embodiments and that many changes might be brought therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. Solid tire from rubber or similar with removable tread, which comprises a substantially resilient tire strip comprised of two co-axial ring-shaped parts with different hardness and elasticity modulus and having a resilient elongation factor comprised between 1.03 and 1.08, an inner part comprising the bead for cooperating with the rim or wheel and having an elasticity modulus comprised between 7 N/mm2 ( + 70 Sh) and 1 5 N/mm2 (+ 95 Sh), a second part comprising the tire strip body having an elasticity modulus-lower than the elasticity modulus of the bead and comprised between 3 N/mm2 (f 40 Sh) and 10 N/mm2 ( + 80t Sh), the tread being comprised of a ring which is substantially extensible in the radial and circumferential direction having an inner diameter which is slightly larger than the outer diameter of the tire strip before being laid over a rim or wheel, and slightly smaller than the outer diameter of the tire strip as laid without the tread over a rim or wheel.

2. Solid tire as defined in claim 1, in which the tread is reinforced with a ring-shaped reinforcement extending adjacent to the inner surface of said tread, to be fitted on the tire strip.

3. Solid tire as defined in claim 2, in which the reinforcement is comprised of cables extending substantially along the circumferential direction of the tread, adjacent the inner surface thereof fitting over the tire strip.

4. Solid tire as defined in claim 3, in which the cables extend with a helix shape about the center axis of the tread.

5. Solid tire as defined in any one of claims 1 to 4, in which said tire strip body is made from rubber having a Shore hardness lying between 40 and 80 Shore.

6. Solid tire as defined in claim 5, in which the hardness of the tire strip body rubber is about 60 Shore.

7. Solid tire as defined in any one of claims 1 to 6, in which the tire strip body bead is made from rubber having a hardness from 70 to 95 Shore.

8. Solid tire as defined in any one of claims 1 to 7, in which the rubber contains a fill from short fibers, notably in the range from 5 to 80 mm.

9. Solid tire as defined in any one of claims 1 to 6, in which the bead contains a compound material formed by layers from fabric alternating with layers from rubber having a hardness from 55 to 75 Shore.

10. Solid tire as defined in any one of Claims 1 to 9, in which the outer surface of the tire strip and the inner surface of the tread fitting thereon are substantially of cylinder shape.

11. Solid tire as defined in claim 10, in which said surfaces are grooved in the cross-wise direction.

1 2. Solid tire as defined in any one of claims 1 to 11, ih which the tire strip body has a cross-wise narrowing in a location lying between the bead and the contact surface thereof with the tread.

1 3. Solid tire as defined in claim 12, in which the side walls of the tire strip body are substantially of concave shape.

14. Solid tire as defined in any one of claims 1 to 13, in which the tire strip bead zone which will project from the receiving area provided on the wheel or rim circumference, is wider than the tire strip zone adjacent the contact surface thereof with the tread.

1 5. Solid tire from rubber or similar, as described above with reference to the accompanying drawings.

16. Method for assembling and disassembling a solid tire as defined in any one of the preceding claims, which comprises first sliding the tread over the resilient tire strip and then forcing the resilient tire strip provided with tread thereof over the rim or wheel by means of a guide device with cone-shaped surface, fitting sidewise against the rim or wheel, and a press acting sidewise on the tire bead as engaged on the guide device.

1 7. Method for assembling and disassembling a solid tire, as described above with reference to the accompanying drawings.