GB1570470A - Scraping tool - Google Patents

Description

(54) SCRAPING TOOL (71) We, EUROTUNGSTENE, a body corporate organised and existing under the laws of France, of 54 avenue Rhin-et Danube, 38100 Grenoble, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a scraping tool for use in preparing the outer surface of a tyre for retreading.

Different mechanisms are known for the preparation of tyre surfaces wherein the peripheral surface of a used tyre is moved against a drum shaped cylindrical tool, rotating at high speed around its axis, the drum being provided with protruding cutting elements for removing excess rubber and to prepare the surface for retreading.

The protruding cutting elements can be of various forms such as points, studs or nails.

In a widely used mechanism described in the French Patent No. 1224475 (U.S. Patents 2896309 and 3082506) these cutting elements are steel arched blades presenting an external periphery of sawtooth shape placed in spaced rows in order to form a helix around the drum. The teeth have a symmetrical "Y" shape and the drum can rotate about its axis in both directions in order to allow cutting in either direction.

The main drawback of this mechanism is the fast wearing of the steel blades which will allow only the treatment of a few dozen tyres. This in turn necessitates a dismantling of the tool, a rather lengthy process which limits the productivity of such a tool.

As a result, it was proposed to use elements of a hard material, in particular tungsten carbide. Those cutting elements have the shape of circular removable plates attached on a disc shaped blade. Such a process allows for increased production, and in addition, the tyre's surface temperature is lower, reducing energy consumption as well as dust and smoke emission during the process.

However, this mechanism is not appropriate for radial tyre carcasses. In fact, for this type of tyre the lateral thickness of rubber to be removed is very thin. With such a tool, the cutting force exerted is very important, which increases the risk of the rubber coming off its carcass.

Furthermore, due to its design, the blade can only turn in one direction, the rubber coming off further from the side where the action of the blade takes place by moving upward from the inside of the tyre toward the outside.

According to the present invention there is provided a scraping tool for use in the preparation of the outer surface of a tyre prior to retreading; said tool comprising a cylindrical drum rotatable in opposed directions about its axis, protruding cutting elements on the periphery of the drum, said cutting elements being capable of working in both directions of rotation of the drum, removable bars mounted on the periphery of the drum in spaced relation thereabout and parallel to its axis, at least one said cutting elements fixed to each bar, the cutting elements on two adjacent bars being displaced relative to each other, parallel to the axis, in such a manner whereby the centres of the cutting elements are disposed on helical paths extending about the drum and at the same distance from the axis.

In order to facilitate mass production it is beneficial that all the bars be identical and have the same number of cutting elements.

In this case, the bars themselves are slightly displaced in relation to each other. The cutting element centres of a bar are preferably at the same distance from each other in order to portion out the cutting pressure.

The cutting element's geometrical centres, protruding on the outer surface of the drum, are located on helical arcs or paths which can be of the same direction; i.e. all to the right or all to the left or alternately left helices and right helices. The main concern being that the whole tyre's surface be subjected to the cutting process.

Either the cutting elements of one single bar are on the helical arcs or else the cutting elements of two adjacent bars which are set off relative to each other form the arcs. The cutting elements are preferably a hard cemented alloy such as carbon or tungsten.

The cutting elements advantageously have at least two symmetrical cutting edges relative to a diametrical drum plane, so as to permit cutting in both direction of drum rotation. The drum can also have a supplementary series of cutting elements on at least one of the side edges, these cutting elements being oriented toward the outside of the drum, making the same acute angle with the diametrical plane of the drum.

The bars can be in any material which could provide for a strong attachment of the cutting elements and a good mechanical holding. They can be made by casting, forging, machine finishing or a sintering process.

The fixing of the cutting elements into the bar can be done by adhesive fixing, brazing, binding, setting, use of sealing alloy, mechanical fixing or casting of the bar on the cutting elements.

The mounting means of the bars on the drum should allow a practical and easy mounting and dismounting of the bars. They can for example be affixed on the drum by a conical dovetail mounting and held in place by a screw or pin. According to an embodiment of this invention, the bars will have a prism shape with a trapezoidal section, the wider base of which is located toward the inside of the drum and encased in the drum's periphery.

In this case, the bars are encased in laterally spaced pairs in a similar shaped section formed within and equal to the combined width of the pair of bars. Both bars are held by prismatic removable wedges of similar trapezoidal outline, engaging the opposed lateral sides, and mounted by an adjustable device workable from the outside of the drum.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawings, in which: Figure 1 is a front view of the tool with a portion in section; Figure 2 is a side view of the same tool with a portion in section taken generally on the line a-a of Figure 1; and Figure 3 illustrates a cutting element fixed on a bar.

The tool consists of a cylindrical drum 1 rotatable around its axis 2 and able to reach high speed in both directions.

Bars 3 are mounted at regular intervals on the periphery of the drum 1. The bars 3 are parallel to the axis 2 and provided with cutting elements 4 at equal distance from each other.

The bars 3 are identical, which allows mass production. Two adjacent bars 3a and 3b are slightly displaced in regard to each other in order that the cutting elements 4a and 4b of the similar row may be placed on a helical line 5 traced on the drum's periphery at the distance from the axis.

The helical paths 5 may all be in the same direction or they may alternate to the left and to the right.

The cutting elements 4, made out of tungsten carbide, have a "Y" shape with a stem 6 sunk into the bar 3 and a part composed of two cutting edges 7 and 8 which are symmetrical relative to a diametrical plane of the drum 1. Stem 6 is affixed in bar 3 by a fixing alloy 9. The cutting edges 7 and 8 can be parallel to the axis but preferably form an acute angle with it, for example in the order of 20'.

The bars 3 have a prism shape with trapezoidal section of which the wider base 10 is placed toward the interior of the drum.

The bars 3 are fixed in the drum 1 in pairs, with their outer sides 11 and 12 engaged with the opposed inclined sides of a similar shaped recessed section formed in the peripheral surface of the drum.

The bars 3 are held by two removable wedges 13 of similar trapezoidal profile which engage the facing sides 14 and 15 of the bars 3.

The wedges 13 include a screw-threaded end shaft 16. The engagement of the wedges 13 with the two lateral sides 14 and 15 of the bars 3 is ensured by Belleville washers 17 compressed together between the inside surface 18 of the drum 1 and a screw-nut 19.

A bridle 20 controlled by a screw 21 is in engagement with the stems' ends 16. The screw adjustment 21 allows the bridle 20 to exert pressure on the stems' ends 16 which slightly pushes out the wedges 13. In so doing, they free the two bars' lateral sides 14 and 15 allowing their easy removal for replacement.

As an example, a cylindrical tool having an exterior diameter of 290 mm, and a width of 115 mm was made consisting of 24 bars having each 6 cutting elements forming 4 helices on the periphery of the drum.

In order to prepare the surface of a tyre with such a tool before retreading, one works first on the tread of the tyre and then downward from the tread onto the side, the rotating speed being the order of 3000 rpm.

One can use a similar tool on the sides but of smaller size in order to remove a thinner layer, for the radial type shell.

The cutting elements may be fixed to the bars by brazing or the bars may be cast around the cutting elements. The bars may be fixed to the drum by a conical dovetail mounting.

WHAT WE CLAIM IS: 1. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading; said tool comprising a cylindrical drum rotatable in opposed directions about its axis, protruding cutting elements on the periphery of the drum, said cutting elements being capable of working in both direction of rotation of the drum, removable bars mounted on the periphery of the drum in spaced relation thereabout and parallel to its axis, at least one said cutting element fixed to each bar, the cutting elements on two adjacent bars being displaced relative to each other, parallel to the axis, in such a manner whereby the centres of the cutting elements are disposed on helical paths extending about the drum and at the same distance from the axis.

2. A scraping tool as claimed in claim 1, in which the drum is provided with identical bars, and same number of cutting elements on each bar.

3. A scraping tool as claimed in claim 2, in which the cutting elements on each bar are at equal distance from each other.

4. A scraping tool as claimed in any preceding claim, in which all the helical paths are in the same direction.

5. A scraping tool as claimed in any of claims 1 to 3, in which the helical paths alternate to the left and to the right.

6. A scraping tool as claimed in any preceding claim, in which the cutting elements are formed of tungsten carbide.

7. A scraping tool as claimed in any preceding claim, in which the cutting elements are provided with at least two cutting edges which are symmetrical relative to a diametrical plane of the drum.

8. A scraping tool as claimed in claim 7, in which the cutting edges form an acute angle with the axis of the drum.

9. A scraping tool as claimed in any preceding claim, in which the cutting elements are fixed to the bars by brazing.

10. A scraping tool as claimed in any of claims 1 to 8, in which the cutting elements are fixed to the bars by a fixing alloy.

11. A scraping tool as claimed in any of claims 1 to 8, in which the bars are cast around the cutting elements.

12. A scraping tool as claimed in any preceding claim, in which the bars have a prismatic shape with a trapezoidal section having a wider base placed toward the interior fo the drum, said bars being encased within the drum's periphery.

13. A scraping tool as claimed in claim 11, in which the bars are fixed by a conical dovetail mounting to the drum.

14. A scraping tool as claimed in claim 1, in which the bars are fixed by a conical dovetail mounting to the drum.

15. A scraping tool as claimed in claim 12, in which the bars are fixed to the drum in spaced pairs, the periphery of the drum including a recessed section with inclined sides for each pair of bars with the outer sides of the pair of bars engaged with the inclined sides of the recessed section, removable prismatic wedges of similar trapezoidal shape engage against the facing sides of each pair of bars, and means engaged between the wedges and the drum to bias the wedges inward against the bars for a retention thereof.

16. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading; said tool comprising a cylindrical drum rotatable in opposed directions on its axis, protruding cutting elements on the periphery of the drum, said cutting elements being capable of working in both directions of rotation of the drum, removable bar means mounted on the periphery of the drum parallel to its axis, said cutting elements being fixed to said bar means in a manner whereby the cutting element centres are placed on helical paths about the drum, said helical paths having the same axis as the drum.

17. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. The cutting elements may be fixed to the bars by brazing or the bars may be cast around the cutting elements. The bars may be fixed to the drum by a conical dovetail mounting. WHAT WE CLAIM IS:

1. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading; said tool comprising a cylindrical drum rotatable in opposed directions about its axis, protruding cutting elements on the periphery of the drum, said cutting elements being capable of working in both direction of rotation of the drum, removable bars mounted on the periphery of the drum in spaced relation thereabout and parallel to its axis, at least one said cutting element fixed to each bar, the cutting elements on two adjacent bars being displaced relative to each other, parallel to the axis, in such a manner whereby the centres of the cutting elements are disposed on helical paths extending about the drum and at the same distance from the axis.

2. A scraping tool as claimed in claim 1, in which the drum is provided with identical bars, and same number of cutting elements on each bar.

3. A scraping tool as claimed in claim 2, in which the cutting elements on each bar are at equal distance from each other.

4. A scraping tool as claimed in any preceding claim, in which all the helical paths are in the same direction.

5. A scraping tool as claimed in any of claims 1 to 3, in which the helical paths alternate to the left and to the right.

6. A scraping tool as claimed in any preceding claim, in which the cutting elements are formed of tungsten carbide.

7. A scraping tool as claimed in any preceding claim, in which the cutting elements are provided with at least two cutting edges which are symmetrical relative to a diametrical plane of the drum.

8. A scraping tool as claimed in claim 7, in which the cutting edges form an acute angle with the axis of the drum.

9. A scraping tool as claimed in any preceding claim, in which the cutting elements are fixed to the bars by brazing.

10. A scraping tool as claimed in any of claims 1 to 8, in which the cutting elements are fixed to the bars by a fixing alloy.

11. A scraping tool as claimed in any of claims 1 to 8, in which the bars are cast around the cutting elements.

12. A scraping tool as claimed in any preceding claim, in which the bars have a prismatic shape with a trapezoidal section having a wider base placed toward the interior fo the drum, said bars being encased within the drum's periphery.

13. A scraping tool as claimed in claim 11, in which the bars are fixed by a conical dovetail mounting to the drum.

14. A scraping tool as claimed in claim 1, in which the bars are fixed by a conical dovetail mounting to the drum.

15. A scraping tool as claimed in claim 12, in which the bars are fixed to the drum in spaced pairs, the periphery of the drum including a recessed section with inclined sides for each pair of bars with the outer sides of the pair of bars engaged with the inclined sides of the recessed section, removable prismatic wedges of similar trapezoidal shape engage against the facing sides of each pair of bars, and means engaged between the wedges and the drum to bias the wedges inward against the bars for a retention thereof.

16. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading; said tool comprising a cylindrical drum rotatable in opposed directions on its axis, protruding cutting elements on the periphery of the drum, said cutting elements being capable of working in both directions of rotation of the drum, removable bar means mounted on the periphery of the drum parallel to its axis, said cutting elements being fixed to said bar means in a manner whereby the cutting element centres are placed on helical paths about the drum, said helical paths having the same axis as the drum.

17. A scraping tool for use in the preparation of the outer surface of a tyre prior to retreading, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.