IL50710A - Method of removing tread material from vehicle tires - Google Patents

Description

D"t '^-j »a»axa " · ΊΩ Tom men1? no* Method of removing tread material from vehicles tires The present invention relates to the removing of tread material from a vehicle tire preparatory to the retreading of the vehicle tire and is particularly concerned with a method of removing the tread material from the tire.

This Patent Application is a Divisional Application from Application 45150 filed on 1.7.1974 entitled "Apparatus for removing tread material from vehicle tires." The removing of tread material from pneumatic vehicle tires is a well known procedure and is generally accomplished by abrading the periphery of the tire with a barbed rasp, or a member having coarse abrasive thereon. It has also been attempted to remove the tread material by cutting with a sharp knife.

The defect with the first mentioned system is that considerable heat is generated which results in the development of dust and smoke and vapors which can be hazardous to the health and which can form a fire hazard and which, furthermore, requires the installation of rather expensive collecting equipment.

Another known system is more fully described in United States Patent No. 3 646 984, and employs a cutting tool which rotates relative to the tire to be retreaded. This system, however, uses the known knife-like tools and rasps, as has been described above, when removing the tread material from the tire to be retreaded.

In the second mentioned method in which a sharp knife is employed for removing the tread material, a great deal of force is required to turn the tire against the cutting blade and foreign material imbedded in the tread material can severely damage such knives. Furthermore, this procedure for removing the tread material from a vehicle tire is not as rapid as the lemoval of the tread material by an abrasive device.

Having the foregoing in mind, a primary objective of the present invention is the provision of a method for removing tread material from a vehicle tire preparatory to retreading Another object is the provision of a method of the nature referred to in which there is substantially no dust or smoke .^p developed during the removing of the material from the tire tread.

Still another object is the provision of a method for removing tread material from a vehicle tire preparatory to recapping the tire which eliminates the need for expensive dust separators and which also reduces health and fire hazards that usually go with such an operation.

According to the present invention there is provided a method of removing the tread material from a pneumatic tire preparatory to recapping thereof which comprises: inflating the tire, rotating the inflated tire on the axis thereof, mounting sharp edged hard wear resistant cutting elements in spaced relation in a holder, presenting the holder to the tread of the tire with the inserts at a positive rake angle of at least about 25 degrees, moving the holder with the inserts therein relatively to the tire, and feeding the holder and tire relatively to cause each insert to take cleanly cut chips of substantial size from the tire tread.

The objects and advantages of the present invention will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which: FIGURE 1 is a view illustrating diagrammatically a machine for use in removing tread material from a vehicle tire.

FIGURE 2 is a side view broken away and drawn at somewhat enlarged scale showing the cutting device used in the machine of Figure 1.

FIGURE 3 is a section indicated on line III-III of Figure 2.

FIGURE 4 is an exploded perspective view showing a cutting insert employed with the cutting device of Figures 2 and 3 and showing the supporting nest therefor and the clamp member which clamps the insert in the nest while simultaneously clamping the nest in a recess provided therefor in the cutter body.

FIGURE 5 is a schematic plan view showing how the cutting inserts could be staggered laterally in the cutter body thereby to inhibit the formation of , / an irregular surface on the tire when the tread material is cut therefrom.

Referring to the drawings somewhat more in detail in Figure 1, reference numeral 10 represents a spindle adapted for being driven in rotation by a motor Ml and having means for supporting a tire 12 which may be a conventional pneumatic vehicle tire. Tire 12 is a tire which is to be supplied with new tread material by known recapping techniques and preparatory to having the new tread material applied thereto, the old, worn tread material is cut away to present a clean outwardly facing surface to which the new tread material is caused to adhere by a vulcanization process.

The spindle 10 may be fixedly supported in any suitable machine frame generally designated 14. The machine frame comprises a foot portion 16 fixedly arranged relative to the portion supporting spindle 10 and having means defining a vertical pivot axis 18. Vertical pivot axis 18 extends vertically in the region of the central radial plane of tire 12 and somewhat radially inwardly from the outer periphery of tire 12.

Pivotally mounted on foot 16 so as to be swingable about axis 18 is an arm 20 on which there is slidably mounted a support 22. Support 22 is slidable radially toward and away from pivot axis 18 and, therefore, radially toward and away from tire 12. Support 22 carries a spindle 24 drivingly connected to a motor M2 and mounted on spindle 24 is a cutter generally indicated at 26 which has distributed about the periphery sharp edged cutting elements.

When cutters 26 is driven in the direction of the arrow thereon and brought into engagement with the periphery of tire 12 when the tire is rotating in the direction of the arrow on the tire, the cutting inserts in the cutter will cut chips from the tire tread and in this manner remove the desired amount of the worn tire tread.

By swinging arm 20 about axis 18, the cutting of the tread can be caused to proceed over as much of the worn tread area as it is desired to remove . The cutting of the worn tread from the tire can be accomplished in a single pass across the tire tread or in multiple passes. The support may be cam controlled to produce the desired contour on the tire being worked.

A particular point of novelty in respect of the device illustrated in Figure 1 is to be found in the cutter 26 which, as will be seen in Figures 2 and 3 , comprises a body 28 having a central aperture 30 for receiving spindle 24 . On the side of body 28 facing the spindle, the body is formed with notches 32 which receive keys 34 fixed to spindle 24 . The body is clamped to the spindle by a large screw 36 threaded into the spindle and having a head engaging the bottom of recess 38 formed in the side of the cutter body facing away from the spindle.

The cutter body, as will best be seen in Figure 2 , has a plurality of pockets or recesses 40 formed therein extending inwardly from the periphery of the cutter body in uniformly distributed circumferential relation and each inclined in the same direction relative to the radial direction of the body.

Each pocket or recess is adapted for receiving a nest member 42 which has a leg 44 at one side for engaging the adjacent side of the cutter body 28. When a nest member 42 is inserted into a pocket until it abuts the bottom wall of the pocket, and so that the leg 44 abuts one side of the cutter body, the respective nest element will1 be precisely located in Each nest element has a recess 46 formed therein and also has a pin 48 extending into the recess. The recess is slightly more shallow in the direction of the axis of pin 48 than the thickness of a cutting element 50 adapted for being received in the recess and the recess is likewise larger in the radial direction of pin 48 than element 50. The element has a central hole 52 which receives pin 48 , and in this manner, the element is located in the recess and is likewise prevented from shifting therein.

As will be seen in Figure 2 , the one side of nest element 42 engages one side of pocket 40 and the bottom wall of recess 46 which is formed in the opposite side of the nest member, diverges in the radially outward direction with the opposite side of the nest member. The top face of an element 50 in the recess also diverges from the opposed side wall of the pocket in the outward direction.

Because of this, the cutting element and nest member can be firmly clamped in position by utilizing a simple wedge 54 , the opposite sides of which taper so that when one side of the wedge engages the adjacent side of a pocket 40, the opposite side of the wedge engages the exposed top surface of the adjacent cutting element 50.

The wedge 54 is adapted for being firmly drawn into pocket 40 to effect the aforementioned wedging action by a screw 56 which has the opposite ends threaded in respectively opposite directions with the radially outer threaded end threadedly en a in a hole in the wedge and the other threaded end threadedly engaging a threaded hole in the cutter body which extends in a direction parallel to the wall of the pocket 40 and on which the wedge slides.

Each cutting element 50 is formed of a hard wear resistant material such as a good grade of tool steel or, preferably, a cemented hard metal carbide material such as tungsten or titanium carbide or mixtures thereof. Other hard metal carbides can be included in the composition without in any way detracting from the utility of the inserts.

As will best be seen in Figure 4 , each cutting element 50 is circular, and has parallel top and bottom faces and a peripheral wall. Each cutting element can be indexed about the axis of the respective pin 48 so that when one peripheral portion of the element becomes worn, a new portion can be brought into cutting position. It will also be noted that the cutting element has a relatively sharp edge 58 extending thereabout at the juncture of the peripheral wall with the top face with the included angle formed between the peripheral wall and the top face ranging from about 85 degrees down to about 30 degrees.

The included angle formed at the cutting edge is determined by the angle which the cutting element makes with the peripheral surface of the cutter body adjacent thereto because the radially outer sides of the periphery of the cutting element must be inclined at such an angle as to provide for clearance from the tread material being cut.

As illustrated in Figure 2 , each cutting element has an angle of about 45 degrees at the cutting edge and is inclined at an angle of about 30 degrees to the radius so that the clearance ~ angle at the radially outer side of the element is on the order of about 15 degrees.

For a cutter body which is six inches in diameter, cutting elements can be provided at every 36 degrees making ten cutting elements in all. Each element might have a major diameter of about three-fourths of an inch and be on the order of about one-eighth inch thick.

The particular cutting element illustrated in the drawings is circular, but it will be understood that the element could be polygonal when viewed perpendicular to the top face thereof and still could be indexed about the axis of symmetry thereof to present new cutting edges successively to cutting position.

Inasmuch as tread material is-somewhat resilient, there will be some tendency for the surface on the tire after the tread material has been cut off to be slightly irregular. This irregularity can be substantially reduced by using cutting elements having cutting edges parallel to the axis of rotation of the cutter body or by making the cutter as indicated in Figure 5 wherein reference numeral 60 schematically illustrates the cutter body and shows how round button type cutting elements 62 could be mounted thereon in staggered relation thereby tending to eliminate the forming of ob ectionably large ridges on the surface of the tire being cut.

In any case, the surface of the tire after having been cut off by a cutter according to the present invention can be buffed and ortions of the side wall of the tire ad acent the tread can also be buffed and thereby smooth the surface of the tire so that it is in ideal condition for receiving the retread material.

It has been discovered, however, that the clean smooth tread surface which is left after a chip has been taken therefrom by a cutter according to the present invention, forms an ideal surface for receiving recapping material and bonds to the recapping material more strongly than does a conventional buffed surface which is obtained when a rasp is employed to remove a tread.

Due to the sharp edges on the cutting elements, the tread material is removed from the tire in the form of chips of substantial size and the cutting action is clean so that there is not much friction whereby a minimum amount of heat is developed and smoke and vapors are not generated during the cutting operation.

Furthermore, the material removed from the tire tread, as mentioned, is in the form of chips of substantial size and there is little or no dust developed so that no dust collector need be employed when practicing the present invention. Also, since the chips are of substantial size, the fire hazard that would exist if fine dust were to be developed is eliminated as is also the health hazards that go with having the air laden with fine dust.

As an example of the speed of operation, a vehicle tire might be arranged to rotate at a surface speed of about 100 feet per minute up to more than 1,000 feet per minute while the cutter might rotate at about 1,000 feet per minute up to 10,000 feet per minute with the tire surface and the cutter surface moving in respectively opposite directions.

The removal of the tread material from a conventional passenger vehicle tire takes about two minutes when practicing the present invention which compares quite favorably with the length of time required to remove the tread material by conventional methods using an abrasive tool.

In locating the cutting elements on the rotatable cutter body and in correlating the speed of the tire being worked with the speed of rotation of the cutter body, it has been found that the best results are obtained when each cutting element on the cutter body removes a chip of substantial size from the tire tread. When the sharp edged cutting elements take substantial chips from the tire tread, cleaner cutting results than is possible when a cutting element takes only a light cut.

The tread material is inherently yieldable and, unless each cutting element encounters a substantial body of rubber and takes a chip of substantial size from the tire tread, there is a tendency for the tread to yield and to tear rather than to cut cleanly. Accordingly, it will be understood that, in the practice of the present invention, each cutting element is intended to remove a clean chip of substantial size from the tread material.

Normally, a single pass across a tire tread is ample for removing the desired amount of tread material and, with each cutting element taking a clean chip with a clean cut from the tread material, the end result is a surface ideally adapted for bonding to recapping material.

Tests and experiments have shown that the bonding of the recapping material to the tread material of a tire which has been cut with a cutter device according to the present invention is much stronger, up to 50 per cent stronger, for example, than the strength of the bond which exists between retreading or recapping material and a tread surface which has been prepared by buffing with a rasp or the like.

It is also important for the clearance angle behind each cutting edge to be equal and, preferably, slightly greater than the positive rake angle on the front side of each cutting insert because this assists in making a clean cut and prevents the cutting inserts from rubbing on the tread material and developing heat therein. A tire from which the tread material has been removed by the use of a cutting device according to the present invention exhibits substantially no rise in temperature due to the cutting operation and, similarly, the cutting elements also remain cool during the cutting operation.

Modifications may be made within the scope of the appended claims .

Claims (10)

WHAT IS CLAIMED IS:

1. The method of removing the tread material from a pneumatic tire preparatory to recapping thereof which comprises; inflating the tire, rotating the inflated tire on the axis thereof, mounting sharp edged hard wear resistant cutting elements in spaced relation in a holder, presenting the holder to the tread of the tire with the inserts at a positive rake angle of at least about 25 degrees, moving the holder with the inserts therein relatively to the tire, and feeding the holder and tire relatively to cause each insert to take cleanly cut chips of substantial size from the tire tread.

2. The method according to Claim 1 in which the holder and tire are moved relatively in the lateral direction of the tire during cutting to cause the inserts to cut laterally across the crown of the tread and partway inwardly along the side walls of the tire adjacent the tread.

3. The method according to Claim 1 in which said chips are of substantial thickness.

4. The method according to Claim 1 in which said holder is disc-like and said inserts protrude radially from the periphery thereof and said tire and holder are rotated on parallel axes during cutting of the tread.

5. The method according to Claim 4 in which said holder rotates at a surface speed of about 10,000 feet per minute and said tire rotates at a surface speed of about 1,000 feet per minute.

6. The method according to Claim 5 in which said holder and tire rotate in the same direction.

7. The method according to Claim 1 in which said holder is disc- like and said inserts protrude radially from the periphery thereof and said tire and holder are rotated on respective axes which are perpendicular to each other.

8. The method according to Claim 5 in which the inserts are spaced in the direction of movement thereof a distance such that each insert engages a substantial body of tread material each time the insert moves past the tire tread.

9. The method according to Claim 8 in which said distance between each insert and the next following insert is on the order of about four inches.

10. The method of removing the tread material from a pneumatic tire preparatory to recapping thereof substantially as hereinbefore described and with reference to the accompanying drawings. For the Applicants Wolff, Bregman and Goller