Abstract:
An abrading wheel such as a rasp hub for use in tire retreading machines includes two generally circular end, or side, plates with plural spaced mounting pins extending between and coupled to the two spaced plates. Rasp blades arranged in stacks which are arranged end-to-end about the wheel&#39;s circular circumference. Disposed between and engaging each pair of adjacent blades is a spacer, which is also attached to the mounting pins. Each spacer is curved lengthwise to match the curvature of the blades and includes plural spaced upper and lower recesses disposed immediately adjacent to its pair of adjacent blades to allow air to freely pass over the entire length of each blade as the hub is rotated at high speed to dissipate heat from the blades during operation for increased blade reliability and longevity.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to tire retreading machines and is particularly directed to improved rasp hubs for use in tire retreading machines. 
       BACKGROUND OF THE INVENTION 
       [0002]    Tire buffing machines are well known in the tire retreading industry. Conventionally, a tire buffing machine includes both a structure for mounting a used tire and a rasp hub which removes the worn tread from the used tire prior to the retreading process. The used tire is rotated while it is held against the rapidly-rotating rasp hub whose outer perimeter is provided with plural tire rasp blades. When engaged against the used tire, the rasp blades cut or shear small segments of rubber from the worn tread surface area of the tire. In this way, the tire is “buffed” to remove the unwanted used tread and to provide the tire with an evenly-textured surface suitable for retreading. 
         [0003]    Tire rasp blades, together with interleaved spacers, are assembled on the periphery of the rasp hub between the hub front and back plates. The back plate is typically provided with plural axially directed support pins for mounting the rasp blades and spacers between the spaced front and back plates. The front plate is then placed on the support pins against the assembled blades and spacers and locked into place. Rasp hubs are typically comprised of five stacked blade sections (wherein each section occupies a 72° circumferential segment) or six stacked blade sections (wherein each section occupies a 60° segment). Thus, each section of the assembled rasp blades is comprised of alternating blades and spacers arranged side-by-side. Furthermore, each section of blades and spacers are angled, or offset, relative to a plane perpendicular to the axis of rotation of the hub to form a cut angle, so that each blade in rotation has an axial cutting swath greater than the width of the blade. The width of a cut swath depends on the cut angle. 
         [0004]    During operation, the toothed blades rotating at high speed come into contact and remove the old tread surface of a revolving tire by the rasp blades&#39; cutting and abrading action. But this high speed frictional interaction causes an increase in temperature of the rasp blades. Prolonged exposure to high temperature causes a weakening of the blades and increases the likelihood of blade failure. Blade failure typically involves the breaking off of its teeth or breaking of the blade&#39;s body, particularly a portion of the body located adjacent an end of the blade. The likelihood of a substantial increase in the temperature of the rasp hub and, in particular, the blades disposed thereon is increased by the generally closed structure of the rasp hub with the blades and spacers disposed around the hub&#39;s outer periphery in a tight fitting arrangement. The present invention operates to reduce the operating temperature of the rasp hub and the blades disposed around its periphery by allowing air to freely circulate through the rasp hub and remove heat from the rasp blades. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0005]    Accordingly, it is an object of the present invention to increase the reliability and operating lifetime of plural cutting blades in a rotating cutting assembly by allowing air to freely circulate throughout the cutting assembly thereby substantially reducing the operating temperature of the blades. 
         [0006]    It is another object of the present invention to increase the reliability and longevity of the buffing blades in the rasp hub for a tire retreading machine. 
         [0007]    The present invention contemplates a multi-blade abrading wheel, or hub, comprising: 
         [0000]    a hub having first and second side plates adapted for rotation about an axis; plural mounting pins equally angularly spaced about the axis of rotation, each mounting pin having first and second opposed ends, wherein the first end of each mounting pin is attached to the first side plate and the second end of each mounting pin is attached to the second side plate; plural stacks of rasp blades removably attached to the mounting pins, the stacks extending end-to-end about the hub; and plural spacers disposed in each of the plural stacks of rasp blades, wherein each of the spacers is disposed between and engages an adjacent pair of rasp blades for maintaining each of the rasp blades in fixed, rigid position in the hub, wherein each of the spacers is attached to one or more of the mounting pins for maintaining the spacers in fixed position between the first and second side plates, and wherein each spacer includes plural lateral recesses each forming a respective opening with an adjacent rasp blade to allow for unrestricted flow of air between each spacer and an adjacent rasp blade for removing heat from the rasp blades during operation. 
         [0008]    The present invention further contemplates a spacer for use in a tire retreading hub adapted for high speed rotation and having plural stacks of elongated rasp blades, wherein the rasp blades are disposed between and securely attached to first and second side plates by means of plural spaced mounting pins disposed between and connected to the first and second side plates, and plural spacers each disposed between and engaging a pair of adjacent rasp blades for maintaining the rasp blades in fixed, rigid position in the hub, each of the spacers comprising: an elongated, generally flat, arc-shaped body comprised of a heat conducting material having a longitudinal axis aligned generally with a longitudinal axis of each of the adjacent rasp blades, the body including plural spaced apertures through each of which is inserted in a tight-fitting manner a respective one of the mounting pins for attaching said body to the hub; and a peripheral flange formed on an outer edge of the elongated, generally flat body and extending outwardly in a direction generally transverse to a plane of the flat body; wherein the peripheral flange includes alternating spaced extended portions and recessed portions disposed about the outer edge of the body, wherein the extended portions engage rasp blades disposed adjacent to the body and the recessed portions form openings between the body and a pair of adjacent rasp blades to allow for unrestricted flow of air between the body and each adjacent rasp blade for removing heat from the rasp blades during operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The appended claims set forth those novel features which characterize the invention. However, the invention itself, as well as further objects and advantages thereof, will best be understood with reference to the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, where like reference characters identify like elements throughout the various figures, in which: 
           [0010]      FIG. 1  is a partial exploded perspective view of a multi-blade rasp hub, or abrading wheel, in accordance with the principles of the present invention; 
           [0011]      FIG. 2  is a plan view of a multi-blade abrading wheel in accordance with the present invention illustrating details of the positioning of the rasp blades and spacers in the wheel; 
           [0012]      FIG. 3  is a top plan view of a spacer adapted for positioning between and in engagement with a pair of rasp blades in accordance with the present invention; 
           [0013]      FIG. 4  is a side elevation view of the blade spacer shown in  FIG. 3 ; 
           [0014]      FIG. 5  is a perspective view of the blade spacer shown in  FIGS. 3 and 4 ; 
           [0015]      FIGS. 6 and 7  are respectively sectional views of cutting blade spacers of ¼″ and ⅜″ widths. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring to  FIG. 1 , there is shown a partial exploded perspective view of a multi-blade abrading wheel  10  incorporating plural inter-blade spacers, where three of these spacers are shown as elements  26 ,  28  and  30  in accordance with the principles of the present invention.  FIG. 2  is a side plan view of an assembled multi-blade abrading wheel  40  illustrating the positions of the cutting blades and spacers within the abrading wheel. From  FIG. 2 , it can be seen that the multi-blade abrading wheel  10  includes a large number of cutting blades and spacers, while only three cutting blades  20 ,  22  and  24  and dime spacers  26 ,  28  and  30  are show in  FIG. 1  for the sake of simplicity. 
         [0017]    Abrading wheel  10  includes first and second hub end plates  12  and  18 . The inner surface of each of the first and second end plates  12 ,  18  is provided with five spaced inclined segments disposed about their respective peripheral portions. Thus, as shown for the second end plate  18 , first through fifth peripheral inclined segments  18   d - 18   h  are disposed about the inner, peripheral surface of the end plate. Only three such peripheral inclined segments  12   d ,  12   e  and  12   f  are shown on the inner surface of the first end hub  12  for the sake of simplicity, it being understood that this end plate is also provided with five spaced, peripheral, inclined segments. Also disposed about the outer periphery of each of the first and second end plates  12 ,  18  are plural spaced apertures extending through the end plate. Thus, plural apertures  12   a  are shown in  FIG. 1  disposed about the outer periphery of the first end plate  12 , while corresponding apertures disposed about the outer periphery of the second end plate  18  are not shown for the sake of simplicity. The first and second end plates  12 ,  18  are disposed within the abrading wheel  10  in a generally parallel, spaced manner, with their respective peripheral apertures in common alignment. Alignment of these apertures allows plural mounting pins  14  to be inserted in corresponding aligned apertures in the first and second end plates  12 ,  18  in assembling abrading wheel  10 . 
         [0018]    In assembling the multi-blade abrading wheel  10 , each of the plural mounting pins  14  is inserted into a respective one of the peripheral apertures in the second end plate  18  as shown in  FIG. 1 . Each of the mounting pins  14  is securely attached to the second end plate  18  in a conventional manner such as by weldments. With the mounting pins  14  securely attached to the second end plate  18 , plural spaced rasp blades  30  each having three spaced apertures therein are positioned over three adjacent mounting pins and slid into position on one of the peripheral inclined segments  18   d - 18   h  of the second end plate. Thus, as shown in  FIG. 1 , a first rasp blade  20  having three spaced apertures therein is positioned on mounting pins  14   a ,  14   b  and  14   c  and is moved into contact with peripheral inclined segment  18   h  disposed on the inner, peripheral surface of the second end plate  18 . With the first blade  20  in position on the peripheral inclined segment  18   h  of the second end plate  18 , a first spacer  26  also having three spaced apertures is positioned in engagement with the first, second and third mounting pins  14   a ,  14   b  and  14   c  and is moved into place in contact with the upper surface of the first rasp blade  20  as shown in  FIG. 1 . This is followed by the sequential positioning of a second rasp blade  22 , a second spacer  28 , a third rasp blade  24 , and a third spacer  30  also as shown in  FIG. 1 . This alternate positioning of rasp blades and spacers on the three spaced, aligned mounting pins  14   a ,  14   b  and  14   c  continues until the specified number of blade and spacer combinations is positioned upon the mounting pins. This sequential positioning of blades and spacers in an alternating manner is also carried out with respect to the remaining peripheral inclined segments disposed about the inner surface of the second end plate  18 . 
         [0019]    When the prescribed number of blade and spacer combinations are positioned about the outer periphery of the second end plate  18  and in engagement with the peripheral mounting pins  14 , the first end plate  12  is positioned in alignment with the mounting pins which are each inserted into a respective peripheral aperture  12   a  within the first end plate. As in the case of the second end plate  18 , the first end plate  12  is then securely attached to the upper ends of the mounting pins  14  by conventional means such as weldments. It is in this manner that plural combinations of alternating blades and spacers are positioned in a fixed, secure manner between and about the respective inner peripheries of the first and second end plates  12 ,  18 . Because of the five peripheral inclined segments described above which are disposed about the respective inner peripheries of the first and second end plates  12 ,  18 , the blade and spacer combinations are oriented at an inclined angle relative to a direction of rotation of the multi-blade abrading wheel. Thus, as shown for the multi-blade abrading wheel  40  illustrated in  FIG. 2 , the stacks of blade and spacer combinations are oriented at an angle α relative to a direction of rotation indicated by arrow  72  of the abrading wheel  40 . 
         [0020]      FIG. 2  shows all or part of three of the five stacked arrays  32 ,  34  and  36  of blades and spacers disposed between first and second end plates  42  and  44 . The first end plate  42  is shown as including first, second and third peripheral inclined segments  42   a ,  42   b  and  42   c . Similarly, second end plate  44  is shown as including third, fourth and fifth peripheral inclined segments  44   a ,  44   b  and  44   c . The first stacked array  32  is disposed between peripheral inclined segments  42   a  and  44   a . The second stacked array  34  is disposed between peripheral inclined segments  42   b  and  44   b . The third stacked array  36  is disposed between peripheral inclined segments  42   c  and  44   c . With reference specifically to the second stacked array  34 , first through tenth cutting blades  46   a - 46   j  are positioned in an alternating manner with first through ninth air cooled spacers  50   a - 50   i  between peripheral inclined segments  42   b  and  44   b  of the first and second end plates  42 ,  44 , respectively. 
         [0021]    Referring again to  FIG. 1 , it can be seen that the inner surface of the second end plate  18  is provided with an upraised inner portion  18   a  having a circular aperture  18   c  therein. Similarly, the first end plate  12  is provided with a corresponding upraised inner portion (not shown in the figure for simplicity) having a circular aperture  12   c  therein. Apertures  12   c  and  18   c  are in mutual alignment and are adapted to receive in a tight-fitting manner a cylindrical drive shaft connected to a conventional rotary drive, which combination is not shown in the figures for simplicity. 
         [0022]    Referring to  FIGS. 3 and 4 , there are respectively shown top plan and side elevation views of an air cooled spacer  56  in accordance with the present invention. Air cooled spacer  56  is arc-shaped, subtending an angle on the order of 72° in one embodiment. Air cooled spacer  56  further includes three spaced, generally circular apertures  60   a ,  60   b  and  60   c  disposed along its length. Each of the three apertures  60   a ,  60   b  and  60   c  is adapted to receive a respective mounting pin in a tight-fitting manner as described above. Air cooled spacer  56  has a cross section in the general shape of an I-beam, as it includes outer and inner flanges  58   a  and  58   b  which extend laterally outward from the inner, flat body  58  of the spacer. 
         [0023]    Disposed on opposed ends of air cooled spacer  56  are first and second end flanges  62   a  and  62   b  which also extend laterally outward from the spacer&#39;s inner body  58 . The outer edges of the spacer&#39;s end flanges  62   a ,  62   b  engage adjacent end portions of a pair of adjacent rasp blades for maintaining the blade end portions in fixed position and preventing bending of the blade. In a preferred embodiment, the first and second end flanges  62   a ,  62   b  are continuous with and formed integrally with the outer and inner flanges  58   a ,  58   b  and all of the flanges are formed integrally with the flat body  58  of the spacer  56  to provide a unitary, single piece structure. 
         [0024]    Disposed on an outer edge portion of air-cooled spacer  56  and extending outwardly from its outer flange  58   a  are plural outer lateral extensions  64   a - 64   e . Similarly, disposed on and extending outwardly from the spacer&#39;s inner flange  58   b  and extending laterally outward therefrom are plural spaced inner lateral extensions  68   a - 68   e . The outer edge portions of each of the outer lateral extensions  64   a - 64   e  and inner lateral extensions  68   a - 69   e  are positioned in abutting contact with adjacent rasp blades for maintaining the blades along their entire lengths in fixed position, thereby preventing bending of the blade. Disposed between each adjacent pair of outer and inner lateral extensions are a pair of recessed portions, each disposed on a respective side of the air-cooled spacer  56 . Thus, pairs of outer recessed portions  66   a - 66   f  are disposed in a spaced manner along the length of the spacer&#39;s outer flange  58   a , while pairs of inner recessed portions  70   a - 70   f  are disposed between adjacent inner lateral extensions  68   a - 68   e  and extend along the length of the spacer  56  in a spaced manner. Pairs of outer and inner recessed portions  66   a  and  70   a  are disposed between opposed ends of the spacer&#39;s first end flange  62   a  and outer and inner lateral extensions  64   a  and  68   a , respectively. Similarly, a pair of recessed portions  66   f  and  70   f  are disposed between adjacent ends of the spacer&#39;s second end flange  62   b  and the fifth outer lateral extension  64   e  and the sixth inner lateral extension  68   e.    
         [0025]    The first through sixth outer recessed portions  66   a - 66   f  and the first through sixth inner recessed portions  70   a - 70   f  respectively disposed on the outer and inner flanges  58   a  and  58   b  of the air cooled spacer  56  allow air to freely move between each spacer and an adjacent cutting blade(s) for cooling the cutting blades during operation. This cooling effect reduces the operating temperature of the blades caused by friction between the blades and the tire work piece. Air flows freely through the multi-blade abrading wheel  10  through its outer circumference in radial directions relative to the rotating abrading wheel. In addition, each of the first and second end plates  12 ,  18  is provided with plural non-axial apertures  74   a - 74   d  as shown for the case of the first end plate  12  in  FIG. 1 . Non-axial apertures  74   a - 74   d  further increase the amount of air flow within the abrading wheel  10  and between each blade and its associated spacer(s). This increased air flow reduces the operating temperature of each of the rasp blades, increasing their reliability during operation and the longevity of each blade in accordance with the present invention. 
         [0026]    While particular embodiments of the present invention have been described, it will be obvious to those skilled in the relevant arts that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications that fall within the true spirit and scope of the invention. The matters set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation.