GB2071003A - Blade or a tyre rasping tool - Google Patents

Abstract

A blade for a rotary tool for rasping elastic material, in particular rubber tyres for vehicles, comprises a knife blade 1 having holes 2 for mounting on the tool and provided with teeth 3 separated from one another by recesses 4, 5 and having outer and inner cutting edges 6, 6', the edges 6 of two each adjacent teeth facing one another and the recesses 4 between these teeth being larger than the recesses 5. <IMAGE>

Description

SPECIFICATION Blade for a cylindrical tool The invention relates to a blade for a cylindrical tool for chip detaching machining of elastic material, in particular rubber tires for vehicles, comprising an arcuate knife blade having holes for mounting on supporting projections of the tool and being provided on its outer edge with teeth separated from one another by recesses and - viewed radially - having outer and inner serrations, with the outer serrations of two each adjacent teeth facing one another.

In a known blade of this type, each one of the teeth of the tooth edges is provided with three serrations of which one points in the rotating direction of the tool and the second one in the opposite direction, while the third one is directed radially outwards and surmounts the other two serrations in a radial direction. The recesses between the teeth are of equal dimensions and the teeth do not curve outwards from the plane of the blade (AT-PS 324 866).

It is known from a different context to turn the teeth in working direction alternatingly to the right and/or to the left from the plane of the blade (US-PS 3 879 825, US-PS 4 059 875) or to bend adjoining double teeth alternatingly out of both sides of the blade (GB-PS 1 300 102).

US-PS 2 795 247 describes a saw for cutting wood, metal or the like consisting of a circular saw blade. In this known saw blade, two each teeth facing in opposite directions are jointly bent out of the plane of the blade.

It is the object of the invention to provide a blade of improved working properties, namely a blade of high cutting rate at minimum generation of heat and long edge life.

This object is achieved according to the invention in a blade of the type initially mentioned by providing recesses of different dimensions between the teeth and by defining each one of the larger of the recesses by adjacent outer serrations facing one another are jointly bent out of the plane of the blade in the same direction.

According to the invention, a trailing tooth forming a groove and somewhat compressing the elastic material along this groove runs before the cutting tooth at any given rotating direction of the tool. The following cutting tooth runs precisely in the trace of the preceding trailing tooth and engages the slightly precompressed material.

By applying the features according to the invention, the result is a cutting surface considerably less rough than that obtained by known processes, but still of unrestricted suitability for vulcanizing.

According to a preferred embodiment of the invention, the serration jointly bent out of the plane of the blade in the same direction are positioned together with the remaining part of the tooth in a common plane inclined in relation to the plane of the blade and intersecting the plane of the blade parallel to the peripheral tangent, with the peripheral edges of the teeth positioned radially ouwards extending in a straight line parallel in respect of the plane of the blade.

It is of advantage to make the bending edge extend approximately within the zone of the bottom of the larger one of the recesses.

The invention is explained in detail under reference to the drawing showing embodiments of the object of the invention.

Figure 1 shows a partial view of a first embodiment of the invention; Figure 2a section along line Il-Il in Fig. 1; Figure 3 the blade according to Fig. 1 and Fig. 2 prior to bending out the teeth; Figure 4 a view corresponding to Fig. 3 with a different shape of the teeth and Figure 5 an embodiment with further changed form of the teeth.

The blade shown in Fig. 1 and 2 consists of a segment-shaped knife blade 1 of tempered steel provided with holes 2 for mounting of fixing on supporting projections of the revolving working tool not shown in detail for machining of the rubber forming the running surface of a pneumatic vehicle tire. The knife blade 1 is provided on its convexly curved outer edge with teeth 3 separated from one another by recesses 4, 5. Each tooth is provided with outer serrations or serrated edges 6, 6'. The radially outer serrations 6 of two adjacent teeth 3 face one another, i.e. one serration extends in rotating direction and the other serration extends opposite to the rotating direction, so that the outer serrations 6 of two adjacent teeth 3 face one another.It is essential in this that the recesses 4, 5 are of different dimensions, i.e. of different widths in rotating direction and preferably also of varying radial depths and that the serrations 6 facing one another of two adjacent teeth 3 always define the larger recess 4.

In addition to the outer serrations 6, 6', each tooth is provided with an inner serration or serrated edge 7 of lesser radial distance than the outer serrations 6, 6', so that the inner serration 7 is surmounted in radial direction by the outer serrations 6, 6'. The inner serration 7 is always positioned on that flank of the tooth facing the smaller recess 5.

According to Fig. 1 and 2, the adjacent teeth 3 defining the larger recess 4 are jointly bent out of the plane of the blade. The bending edge extends approximately within the zone of the bottom of recess 4. The pairs of teeth 3 are alternatingly bent outwards from both sides of the plane of the blade.

"Bending outwards" is understood to mean that the teeth are arranged in a plane inclined to the plane of the blade, but are not twisted.

Fig. 3 shows the knife blade prior to bending the teeth outwards. For easy reference, the same reference numbers as in Fig. 1 and 2 are used Fig. 4 shows an embodiment in which the recesses between the teeth 3 are of different shapes. The larger recesses 24 are circular and the smaller recesses 25 are angular and present merely in the form of a wedge-shaped notch 25.

Fig. 5 shows an embodiment in which the larger recesses 34 are formed of rectangles set on their points with rounded-off corners, while the smaller recesses 35 are of circular shape.

It is understood that the teeth of the blades according to Fig. 4 and 5 can be bent outwards in the same manner as those shown in Fig. 1 and 2. It would of course also be possible to use teeth of many other shapes.

The recesses could also have any given form.

The outer serrations are preferably shaped straight, i.e. extending tangentially to the convex outer edge of the blade, but they could also be of curved shape. The outer serrations are arranged particularly on a common straight line or a circular arc.

Claims (6)

1. Blade for a cylindrical tool for chip detaching machining of elastic material, in particular rubber tires for vehicles, comprising an arcuate knife blade having holes for mounting on supporting projections of the tool and being provided on its outer edge with teeth separated from one another by recesses and - viewed in a radial direction - having outer and inner serrations, with the outer serrations of two each adjacent teeth facing one another, characterized in that the recesses between the teeth are of different dimensions and that the adjacent outer serrations facing one another in each case define the larger one of the recesses and that two each adjoining serrations facing one another are jointly bent outwards in the same direction from the plane of the blade.

2. Blade according to claim 1. wherein the serrations jointly bent out of the plane of the blade in the same direction are positioned together with the remaining part of the tooth in a common plane inclined in relation to the plane of the blade and intersecting the plane of the blade parallel to the peripheral tangent.

with the peripheral edges of the teeth positioned radially outwards extending in a straight line parallel in respect of the plane of the blade.

3. Blade according to claim 2, wherein the bending edge extends approximately within the zone of the bottom of the larger one of the recesses.

4. Blade according to any one of the claims 1 to 3, wherein the additional serration of lesser radial distance from the inner edge of the knife blade that the other serrations protrudes into the smaller one of the recesses

5. Blade according to claim 1, wherein the blade is segment-shaped.

6. A blade substantially as described with reference to the accompanying drawing.