Abstract:
Tread guides ( 24, 26, 28 ) supported on a frame ( 16 ) over a conveyor ( 10 ) have rollers ( 28 ) for engaging edges of the tread ( 14 ) an the conveyor and a constant centering force is provided by ball nuts ( 50, 52 ) in engagement with a ball screw ( 44 ) connected to a pneumatic torque applying actuator ( 56 ). Conicity adjustment ( 62, 66 ) is provided by lateral adjustment of the ball screw ( 44 ), ball nuts ( 50, 52 ) and tread guide assembly as a unit relative to the conveyor ( 10 ).

Description:
TECHNICAL FIELD 
     This invention relates to an apparatus for applying a constant centering force on the edges of tire tread rubber as it travels across an application conveyor to a tire drum. Conicity offset adjustment is also provided by adjusting the position of the center line of the tread relative to the center line of the tire building drum. 
     BACKGROUND ART 
     Apparatus for applying a uniform force perpendicular to the axis of the tread as it travels across an application conveyor toward a tire building drum is shown and described in U.S. Pat. No. 5,389,187. The method of applying the force is shown and described in U.S. Pat. No. 5,534,093. In accordance with the method and apparatus of these patents, the tread is conveyed on a conveyor between two self-centering guides which are slidably mounted on a frame positioned over the conveyor. The guides have parallel rows or rollers for engaging opposite edges of the tread and are urged toward the tread edges by a pneumatic, double-acting piston cylinder assembly connected to the guides by pulleys and cables. The piston cylinder assembly is connected to a centering screw for adjusting the position of the tread centerline. 
     U.S. Pat. No. 3,413,174 is directed to a conveyor apparatus having guide rolls for adjusting the longitudinal center line of the tread, however, no provision is made for accommodating a variable width of the tread. U.S. Pat. No. 4,261,286 is directed to a conveyor apparatus having a pair of threaded shafts to rotate in threaded shoulder guides urging them towards the center of a tread with a motor rotating the shafts, however, there is no disclosure of a single ball screw extending between supporting frame members for moving two tire tread guides together and providing a continuous constant force against each side of a tire tread. 
     The publication Grundlagen der Preumatik Auto Krausskopf-Verlag GmbH, Mainz sets forth the rotational momentum behavior of compressed air motors. With reference made to FIG. 40 which shows characteristic curves of a compressed air motors has a function of “n” (rotation speed) there is no disclosure of using a pneumatic rotary actuator which does not rotate at a rotational speed, but only applies torque to a ball screw for urging nut members of guides toward the edges of a tread. 
     DISCLOSURE OF INVENTION 
     The present invention is directed to apparatus for applying a constant centering force on the edges of tread rubber as it is carried by an application conveyor toward a tire building drum. The constant centering force is provided by a ball screw and nut assembly, with the ball screw torque controlled by a pneumatic rotary actuator connected to the screw. An adjustment sleeve provides conicity offset adjustment by moving the entire ball screw and nut assembly laterally along the axis of the ball screw whereby the position of the center line of the tread may be adjusted slightly relative to the center line of the tire building drum. 
     In accordance with one aspect of the invention, there is provided apparatus for conveying a tire tread comprising a conveyor with two guides extending over the conveyor and having rollers engageable with side edges of the tread, characterized by the guides having nut members engageable with a ball screw extending between supporting frame members for moving the guides together or apart by rotating the ball screw and torque applying means including a pneumatic rotary actuator connected to the ball screw for applying torque to the ball screw to urge a nut member of a first one of the guides toward a first edge of the tread and a nut member of a second one of the guides toward a second edge of the tread and the torque applying means including a pneumatic rotary actuator connected to the ball screw providing a continuous constant force at each side of the tire tread by the rollers while in contact with the tread regardless of the variation in width of the tread, a clutch mounted between the ball screw and the pneumatic rotary actuator at a first end of the hall screw and manual means to rotate the screw mounted at a second end of the screw whereby the initial spacing of the guides may be provided by manually rotating the ball screw and whereby the torque forces may be applied by actuating the clutch to engage the pneumatic rotary actuator. Further embodiments of the invention are defined in the dependent claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a plan view partly in section of the tread centering apparatus embodying the invention with the conveyor deleted taken along the plane of line  1 — 1  in FIG.  2 . 
     FIG. 2 is a sectional view of the apparatus shown in FIG. 1 with the conveyor taken along the plane of line  2 — 2  in FIG.  1 . 
     FIG. 3 is a sectional view taken along the line  3 — 3  in FIG.  2 . 
     FIG. 4 is an enlarged fragmentary sectional view showing the ball screw nuts and the balls with the left-hand and right-hand grooves of the ball screw. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 2 and 3, a tread application conveyor  10  is shown having rollers  12  for supporting a tread  14  as it travels over the conveyor towards a tire building drum (not shown). A frame  16 , having side members  18  and a top member  20 , is mounted on the conveyor  10  and positioned over the conveyor. As shown in FIG. 1, two guides such as long rod assemblies  24  and  26  with ball bearing rollers  28  are suspended in housings  30  and  32  positioned above either side of the tread  14 . The angular orientation of the rod assemblies  26  may be adjusted to place the rollers  28  in optimum locations to engage the shoulders of the tread  14 . The housings  30  and  32  have bushings  34  and  36  slidably mounted on linear ways or rods  38  and  40  clamped to the side members  18  of carrier frame  16 . 
     A ball screw assembly  42  is positioned between the rods  38  and  40  generally at the center of the tread guiding apparatus. A ball screw  44 , shown more clearly in FIG. 4, is divided at its center line A—A into right-hand threads  46  at one side, and left-hand threads  48  at the other side. A left-hand ball screw nut  50  having a ball  51  is attached to the left-hand housing  30 . A right-hand ball screw nut  52  having a ball  53  is attached to the right-hand housing  32 . Accordingly, when the ball screw  44  is rotated the relative distance between the housings  30  and  32  will be increased or decreased. A hand wheel  54  may be mounted at one end of the ball screw  44  and a torque applying means, such as a pneumatic rotary actuator  56 , may be mounted at the other end of the screw  44 . A clutch  58  may be positioned between the ball screw  44  and the pneumatic rotary actuator  56 . It is understood that other means, such as weights carried by cables wound around the ball screw  44  may be provided to supply the torque needed for the operation of this apparatus. 
     Referring to FIGS. 1 and 2 a screw support bearing  60  is positioned inside a conicity adjustment sleeve  62  having external threads in mating engagement with threads on a mounting bracket  64 , which is attached to one of the side members  18  of the frame  16 . A lock nut  66  may be provided to hold the adjustment sleeve  62  in place. In order to adjust the rod housings  28  and  30  laterally along the axis B-B of the ball screw  44 , the lock nut  66  may be loosened and the conicity adjustment sleeve  62  rotated in the desired direction. This adjustment is used to move the center line of the tread  14  slightly from the center line of the tire building drum to improve conicity readings and is referred to as the “conicity offset adjustment.” 
     At the other end of the ball screw  44  from the conicity adjustment sleeve  62  a housing  68  holding the rotary actuator  56  and surrounding the clutch  58  is slidably mounted on shoulder screws  70 , threaded in the other one of the side members  18  of the frame  16 , permitting the housing to move relative to the frame during the conicity offset adjustment. 
     In operation, the ball screw  44  provides width adjustment and centering for the self-centering rod assemblies  24  and  26 . Adjustment of the distance between the rod assemblies  24  and  26  is provided by disengaging the clutch  58  and rotating the ball screw with the hand wheel  54  until the rod assemblies  24  and  26  reach the desired spacing. Preferably this is a setting which spaces the rollers  28  at a distance slightly narrower than the width of tread  14 . The clutch  58  may then be engaged, coupling the ball screw  44  to the rotary actuator  56  to drive the rod assemblies  24  and  26  towards the center line A—A and providing centering of the rod assemblies  24  and  26 . 
     In addition to centering, the tread guide of this invention utilizes the ball screw  44  to hold the housings  30  and  32  in a position with torque applied to the end of the ball screw by the pneumatic rotary actuator  56 . This torque provides resistance to rotation of the ball screw  44  as the edges of the tread  44  press against the rollers  28  in a direction to open the space between the rollers. The torque provided may be changed by changing the air pressure in the pneumatic rotary actuator  56 . 
     Before the tread  14  reaches the guide rollers  28  on the conveyor  10 , the shaft of the pneumatic rotary actuator  56  may be positioned at one limit of its 280 degree travel, placing the housings  30  and  32  and rollers  28  at a spaced distance apart slightly less than the width of the tread. When the tread  14  reaches the rollers  28  and the edges make contact with the rollers, the rollers will be forced to open slightly. Contact with the rollers  28  at the left-hand housing  30  causes the ball  51  of the ball nut  50  to move along the axis B—B of the screw  44  in a direction away from the centerline A—A of the ball screw  44  rotating the screw so that the right-hand ball screw nut  52  is moved by a ball  53  of the ball nut  52  causing the right-hand housing  32  with the rollers  23  to be moved in the opposite direction. Large lead on the ball screw  44  make it possible to translate linear motion into rotary motion due to the mechanical efficiency of the screw and nut combination. As the housings  30  and  32  are forced open, the restoring torque force applied by the rotary actuator  56  attempting to close them remains constant. This constant force allows the tread  14  to be stretched uniformly over its length as it is delivered on center to the tire building drum. 
     While a certain representative embodiment and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.