A Tire Rasp Blade Ein Reifenraspelblatt Une Lame De Râpe À Pneumatique
Total Page:16
File Type:pdf, Size:1020Kb
Europäisches Patentamt (19) European Patent Office Office européen des brevets (11) EP 0 640 423 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int. Cl.7: B23D 71/02 of the grant of the patent: 05.01.2000 Bulletin 2000/01 (21) Application number: 94650020.4 (22) Date of filing: 31.08.1994 (54) A tire rasp blade Ein Reifenraspelblatt Une lame de râpe à pneumatique (84) Designated Contracting States: (72) Inventor: Jensen, Wayne AT BE CH DE DK ES FR GB GR IT LI LU NL SE Olympia Fields, Illinois 60461 (US) (30) Priority: 31.08.1993 US 114773 (74) Representative: Casey, Lindsay Joseph et al (43) Date of publication of application: F. R. Kelly & Co. 01.03.1995 Bulletin 1995/09 27 Clyde Road Ballsbridge (73) Proprietor: Dublin 4 (IE) B & J MANUFACTURING COMPANY Glenwood Illinois 60425 (US) (56) References cited: US-A- 3 879 825 US-A- 5 033 175 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 0 640 423 B1 Printed by Xerox (UK) Business Services 2.16.7/3.6 12EP 0 640 423 B1 Description [0007] The present invention provides a bent tire rasp blade for use in a tire buffing machine. The bent blade [0001] The present invention relates to a tire rasp has a nonplanar elongated body having two planar por- blade for use in tire buffing machines. Relevant prior art tions or "flats." The blade also includes an outer working is disclosed in U.S. Patent Nos. 5,033,175, 4,019,234 5edge having a plurality of teeth which extend in a direc- and 2,703,446. tion generally parallel to the direction of hub rotation. [0002] Tire buffing machines are well known in the tire The outer working edge is comprised of two curved sur- retreading industry. Conventionally, a tire buffing faces, each curve defining a portion of an ellipse. The machine includes both a structure for mounting a used two curved elliptical surfaces of the outer working edge tire and a rasp hub which removes the worn tread from 10 intersect at a mid-portion of the blade where the two the used tire prior to the retreading process. The used planar end portions of the blade body are joined. tire is rotated while it is held against the rapidly rotating [0008] The use of an elliptically-shaped outer working rasp hub whose outside perimeter is provided with a edge compensates for the inclined positioning of the multitude of tire rasp blades. When so engaged against blades on the hub. As a result, the "effective geometry" the used tire, the blades cut or shear small segments of 15 of the working edges of the inclined blades as they rubber from the worn tread surface area of the tire. In rotate on the hub is circular. this way, the tire is "buffed" to remove the unwanted [0009] In the context of the present invention, the used tread and to achieve an evenly textured surface terms "nonplanar," "bent," and "V-shaped" are all suitable for retreading. intended to describe the geometry of rasp blades once [0003] Tire rasp blades, together with intervening 20 they have been assembled within the hub assembly, spacers, are assembled on the periphery of the rasp and then viewed radially toward the hub's axis of rota- hub between the hub front and back plates. U.S. Patent tion from a point outside the circumference of the hub. Nos. 2,703,446 and 4,019,234 disclose such conven- Thus, a "nonplanar" blade body is one whose length, tional prior art rasp hub assemblies wherein the back from end to end, does not lie in a single plane. plate of the hub has axially directed support pins on 25 [0010] "Symmetrical" as to describe blades is defined which are mounted the rasp blades and spacers. The herein to mean a type of blade in which a repetitive pat- front plate is then assembled onto the support pins tern is utilized, such that one half of the blade is a mirror against the assembled blades and spacers and locked image of the other. However, while the preferred into place. embodiment of the present invention includes the use of [0004] Use of bent blades with flat spacers is 30 symmetrical blades, the present invention also contem- described in U.S. Patent No. 5,033,175 which discloses plates that the blades may be nonplanar and asymmet- a tire rasp blade having the features of the preamble of rical, and these forms are contemplated by the present Claim 1. This arrangement creates a circumferentially invention as well. interlocked hub with less potential for mechanical failure [0011] Additionally, the bent blade is provided with at high rotational speeds. 35 teeth which are arranged generally parallel to the axis of [0005] It has been conventional practice to form the rotation of the hub, as shown in Figure 3. In a preferred outer-most portion or "working edge" of the tire rasp embodiment, the teeth are angularly offset from the flats blade as a segment of a circle. That is, the working edge by an angle of about 3° to 5°. In this embodiment, the is in the form of an arc defined by a common radius. leading edge of each tooth -- the edge pointing in the However, when such tire rasp blades are assembled 40 direction of hub rotation -- will be displaced to one side into a hub, they are inclined relative to the direction of of the blade body along one planar portion of the blade rotation of the hub. As a result, the actual geometry of and to the other side of the blade body along the other the working edge of each blade -- as it is rotated on the planar portion of the blade. hub -- is no longer circular relative to the surface of the [0012] It has also been determined that the present tire being buffed. In effect, as the buffing hub rotates, the 45 invention gives the operator better control and stability working edge of the inclined tire rasp blades cyclically during cutting while also imparting an enhanced buffing move toward and away from the surface of the tire. This, action to the tire. Two reasons arising from the novel in turn, causes inefficient operation and uneven buffing bent blade/tooth arrangement of the present invention of the tire. are believed responsible for the enhanced stability [0006] The present invention having the features of 50 which results. claim 1 is directed to a tire rasp blade having elements [0013] First, it is believed the symmetrical blade con- whose shape and configuration affords it certain advan- figuration of the present invention contributes to the tages over prior art rasp blade designs. Moreover, the overall stability of the hub assembly. A force is exerted tire rasp blade of the present invention enhances per- by the tire onto the first planar portion of the blade as it formance. This is achieved because the configuration of 55 buffs the tire. Then, as the second planar portion of the the blade body and working edge permits the teeth on blade sweeps across the tire, an equal and opposite the working edge to attack the tire tread with more uni- force is exerted by the tire on that portion. These alter- formity and precision. nating, equal and opposing forces are believed to serve 2 34EP 0 640 423 B1 as constant stabilizers for the hub assembly as the hub Because the blade 10 is bent along its longitudinal axis, rotates. when assembled into the tire buffing machine hub, each [0014] Second, the use of the elliptical curved working planar portion 14 and 16 will be disposed at an angle edge allows the working edge to present a uniform relative to the hub's direction of rotation (and to a plane cylindrical surface of teeth to the tire. Because the blade 5normally intersecting the hub's axis). In turn, this angu- is positioned at an angle to the hub's axis, the elliptical lar orientation will, in effect, "convert" the elliptical work- working surface is "converted" to a circular surface ing edge into a circular surface as presented to the tire when mounted on and rotating with the hub. In this man- being buffed. FIGURE 4 is intended to more graphically ner, the blade's teeth are applied more uniformly to the illustrate the elliptical geometry concept of the present tire in the buffing operation. 10 invention (the actual dimensions have been exagger- [0015] While the bent blades of the present invention ated for purposes of illustration). As shown, the typical can be fabricated from a pre-formed rigid material as is circular working edge (in phantom) with radius R has conventional in the art, such as carbon-steel, they can been modified to comprise two elliptical surfaces E1 and also be usefully fabricated from a conformable, ductile E2. material or from a conformable and resilient material. 15 [0019] Thus, the plurality of bent blades, all with dual [0016] A hybrid fabrication has been found suitable, as elliptical working edges, will establish a generally cylin- well. In this hybrid fabrication, a conformable ductile drical buffing surface which uniformly and evenly material is used to fabricate a planar blade.