Abstract:
A conveyor assembly and method for conveying and storing a strip material in a conveyor system that is subject to changes in length of the strip material due to intermittent operation includes an upper conveyor ( 16 ), an adjustable substantially horizontal center conveyor ( 22 ) for receiving the strip material ( 34 ) from the upper conveyor, and a lower conveyor ( 28 ) for receiving the associated strip material from the center conveyor. A computer ( 94 ) controls the movement and rotation of the center conveyor, and loop detecting apparatus on the center conveyor may also detect a loop ( 90 ) in the strip material carried by the center conveyor and thereby detecting changes in length of the strip material not predetermined by the computer. A servomechanism ( 100 ) activated by signals from the computer or the loop detecting apparatus moves the center conveyor in a substantially horizontal direction.

Description:
TECHNICAL FIELD 
     This invention pertains to the art of methods and apparatuses for adjusting the length of a conveyor system to compensate for changes in the length of a strip material caused by intermittent feeding or by changes in speed of feeding, and more specifically to methods and apparatuses for supporting the strip material in a generally horizontal attitude during the length adjustment. 
     BACKGROUND ART 
     In the past, vertical festoons were used to adjust the length of a conveyor system to compensate for intermittent feeding of strip material to meet variable production requirements. However, when vertical festoons were used, the strip material was not supported and was stretched by its own weight. This stretching of the strip material was not desirable when assembling a product such as a tire. One such conveyor of strip material is found in U.S. Pat. No. 4,892,609 to Nakanome et al., which discloses an automatic material feeder in tire forming machines. The machine has a traditional vertical festoon to support the buildup of tire building materials. 
     When conveyors of a strip material did not have features to compensate for changes in length of the strip material caused by intermittent feeding, extruders, for example, would have to be stopped and started to compensate for the changes in feeding. This starting and stopping may produce undesirable variations in the strip material. 
     Applicants recognized the need to provide an adjustment apparatus and method that did not stretch the strip material and did not produce or add additional stresses to the strip material. 
     The present invention contemplates a new and improved adjustment for a conveyor system which is simple in design, effective in use, and overcomes the foregoing difficulties and others while providing better and more advantageous overall results. 
     DISCLOSURE OF INVENTION 
     In accordance with the present invention, a new and improved adjustable substantially horizontal conveyor is provided which compensates for the changes in length of the strip material being conveyed as a result of intermittent feeding without altering the weight or shape of the strip material. 
     More particularly, in accordance with the present invention, a conveyor assembly for conveying and storing an associated strip material in a conveyor system is provided. The conveyor assembly includes an upper conveyor for receiving and conveying the associated strip material. The upper conveyor has a first conveyor belt and a first driving means for driving the first conveyor belt. The upper conveyor is substantially stationary. A center conveyor receives the associated strip material from the upper conveyor, and has a second conveyor belt and a second driving means for driving the second conveyor belt. The center conveyor is movable along a substantially horizontal path and has length adjusting means for moving the center conveyor along the path. A lower conveyor is provided for receiving the associated strip material from the center conveyor, and has a third conveyor belt with a third driving means for driving the third conveyor belt. The lower conveyor is substantially stationary. 
     According to one aspect of the present invention there is provided a length adjusting conveyor for storing a variable length of strip material in a conveyor system including supply means for supplying the associated strip material to the length adjusting conveyor with the length adjusting conveyor having a conveyor belt and driving means for driving the conveyor belt, the length adjusting conveyor being movable along a substantially horizontal path; power means for moving the length adjusting conveyor along the path; and, take away means for receiving the associated strip material from the length adjusting conveyor. 
     According to another aspect of the present invention there is provided a method of conveying an associated strip material along a conveyor assembly wherein the conveyor assembly includes an upper conveyor having a first conveyor belt and a first driving means, a center length adjusting conveyor having a second conveyor belt and a second driving means, and a lower conveyor having a third conveyor belt and third driving means, the method including the steps of: conveying the associated strip material along the upper conveyor in a first direction with the first driving means; transferring the associated strip material to the center length adjusting conveyor; moving the center length adjusting conveyor along a substantially horizontal path to adjust the length of the conveyor assembly in response to changes in length of the associated strip material; conveying the associated strip material along the center length adjusting conveyor in a second direction opposite the first direction with the second driving means; transferring the associated strip material to the lower conveyor; and, conveying the associated strip material along the lower conveyor in the first direction with the third driving means. 
     According to another aspect of the present invention there is provided a method of adjusting the length of a conveyor system to compensate for changes in the length of an associated strip in a conveyor system, the conveyor system having a length adjusting conveyor with a conveyor belt and driving means, supply means, and take away means, the method including the steps of: supplying the associated strip material to the length adjusting conveyor with the supply means; moving the length adjusting conveyor in a substantially horizontal direction in response to changes in length of the associated strip material in the conveyor system; conveying the associated strip material along at least a portion of the length adjusting conveyor with the driving means; and, transferring the associated strip material to the take away means. 
     One advantage of the present invention is that the conveyor system may adjust for variable lengths of the strip material in the system caused by different supply and take away speeds including stoppage at the takeaway position. 
     Another advantage of the present invention is that the conveyor system adjusts for changes in the length of the strip material in the system without changing the stresses on the strip material. 
     Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and herein: 
     FIG. 1 is a schematic side elevation of a conveyor assembly embodying the invention showing the center conveyor in the retracted position; 
     FIG. 2 is a schematic side elevation of the conveyor assembly of FIG. 1 with the center conveyor in the extended position; 
     FIG. 3 is an enlarged fragmentary view of part of the center conveyor showing a preferred embodiment of the present invention utilizing a proximity switch; and, 
     FIG. 4 is a schematic side elevation of the conveyor assembly of FIG. 1 with a proximity switch at the end of the center conveyor and the upper conveyor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting the same, FIG. 1 shows a schematic view of a conveyor assembly  10  embodying the system of the invention. The conveyor assembly  10  preferably has an upper conveyor  16 , a center conveyor  22 , and a lower conveyor  28 . A strip material  34  of rubber or other deformable material is conveyed by the conveyor assembly  10  from a supply position  40 , such as from an extruder, along a path  44  to a take away position  46 , for feeding the strip material to apparatus such as a strip applicator. The strip material  34  is conveyed from the supply position  40  over the upper conveyor  16  in the direction of arrow A by a conveyor belt  52  driven by a first servomotor  58 . The strip material to fall over an end  60  of the upper conveyor  16  onto the center conveyor where the strip material is moved in a reverse direction as shown by arrow B. The strip material  34  is turned over and is conveyed on the center conveyor  22  on a conveyor belt  64  driven by a second servomotor  70 . At a leading end  72  of the center conveyor  22 , the strip material  34  is then transferred to the lower conveyor  28 , preferably by allowing the strip material to fall over the end of the center conveyor onto the lower conveyor where the strip material again reverses direction in the direction of arrow A and is turned over to the same position as it was on the upper conveyor  16  so that it is right side up. The lower conveyor  28  conveys the strip material  34  in the direction of arrow A along a conveyor belt  76  driven by a third servomotor  82  to the take away position  46 . 
     The upper conveyor  16  conveys the strip material  34  at an upper conveyor speed S 1  that equals the speed at which strip material is provided at the supply position  40 . The lower conveyor  28  conveys strip material  34  at a lower conveyor speed S 2  that equals the speed at which the strip material is taken away at the take away position  46 . When speed S 1  equals speed S 2 , the center conveyor  22  conveys strip material  34  at a speed S 3  that is equal to speed S 1  and speed S 2 . When the demand for the strip material  34  at the take away position  46  decreases, such as when the feeding of the strip material application is intermittent, or decreased, the speed S 2  is decreased. If speed S 1  of the upper conveyor  16  cannot be adjusted to compensate for the decrease in speed S 2 , then the strip material  34  will back up along the conveyor assembly  10 . In the preferred embodiment of the invention, a computer  94  is used to control the servomotor  70  that drives the center conveyor belt  64 . The center conveyor  22  may be supported on a frame which is mounted on a servomechanism  100  such as a belt driven liner actuator having a servo motor to move the frame and supported center conveyor back and forth substantially horizontally, in the directions of arrows A and B. If the speed S 1  is different than the sped S 2 , then computer  94  preferably directs servomotor  70  to rotate the center conveyor belt  64  at a speed S 3  that is equal to the average of speeds S 1  and S 2  or one half of the sum of speeds S 1  and S 2 . Computer  94  is also connected to the servomechanism  100  which moves the center conveyor  22  at a speed S 4  that is equal to one half of the difference between speed S 3  and speed S 2 . If speed S 3  is greater than speed S 2 , the center conveyor  22  is moved in the direction of arrow B. If speed S 2  is greater than the speed S 3 , then the center conveyor  22  is moved in the direction of arrow A. The speed S 4  at which the center conveyor  22  is moved is predetermined for the condition where S 2  is zero between feeding of the strip material  34  and where S 2  is greater than S 1 , during the feeding of the strip material. Additionally, an optical sensor  88  is placed near the end  72  of the center conveyor  22  to detect whether a loop  90 , shown in dotted lines, is formed by decreased tension in the strip material  34  due to the speed S 2  of the lower conveyor  28  being less than the speed S 1  of the upper conveyor, and when the computer  94  has not made a correction for the decreased tension in the strip material. If such a loop  90  is detected the computer  94  receives a signal from the optical sensor  88  and in response causes the servomechanism  100  to move the center conveyor  22  for a predetermined time in direction B to adjust the length of the strip material  34  by picking up the slack in the strip material. 
     FIG. 2 shows a schematic view of the conveyor assembly  10  with the center conveyor  22  moved to the right and acting as a length adjusting conveyor by increasing the length of the path  44  to accommodate the increased length of the strip material  34  in the system as the strip material is moved along the conveyor assembly  10 . In FIG. 2, the servomechanism  100  has moved the center conveyor  22  in the direction of arrow B at the direction of the computer  94  or after the sensor  88  detected a loop  90 . This movement has increased the length of the path  44  to compensate for the increased length of the strip material  34  in the system and allows the conveyor assembly  10  to support the strip material without increasing the tension in the strip material. This is particularly important for materials such as extruded rubber that are susceptible to deformation under tension. 
     With further reference to FIGS. 1 and 2, when a loop  90  is detected by the optical sensor  88  which is in communication with the computer  94 , signals are conveyed from the computer to the servomechanism  100  preferably to move the center conveyor  22  at a speed S 4  that is one half the difference between speed S 3  and speed S 2 . The center conveyor  22  is moved in the direction of arrow B if speed S 2  is less than speed S 3 , and the center conveyor is moved in the direction of arrow A if speed S 2  is greater than speed S 3 . When the sensor  88  no longer detects a loop  90  in the strip material  34 , the computer  94  conveys signals to servomechanism  100  to move the center conveyor  22  in the direction of arrow A. If a loop  90  is again detected in the strip material  34  by the sensor  88 , the computer  94  will once again convey signals to the servomechanism  100  to move the center conveyor in the direction of arrow B. This process of moving the center conveyor  22  back and forth keeps the conveyor assembly  10  in an equilibrium position and the tension on the strip material  34  substantially constant. 
     With reference to FIG. 3, a preferred embodiment of the sensor for the loop  90  is shown in which a proximity switch  106  is disposed at the end  72  of the center conveyor  22  to detect the loop in the strip material  34 . The proximity switch  106  includes a roller  108  attached to a metal contact  112 . The roller  108  is guided by slides  114 ,  116  located at the sides  120 ,  122  of the center conveyor  22 . The roller  108  is pulled in direction A by the tension of the strip material  34 , and in direction B by springs  132 ,  134  that are connected to the roller. The metal contact  112  moves back and forth between two contacts  124 ,  126  to form a switch. When speed S 1  is equal to speed S 2 , the proximity switch  106  is held in an equilibrium position, and the metal contact is suspended between the two contacts,  124 ,  126 . When the speed S 1  is greater than speed S 2 , a loop  90  forms around the proximity switch  106 , and the tension on the roller  108  is reduced, thereby allowing springs  132 ,  134  to pull the roller and the metal contact  112  into engagement with contact  124 , and thereby closing a circuit that includes the power supply  118  and detection apparatus  140 . The detection apparatus  140  then causes activation of the servomechanism  100  (see FIG. 2) to move the center conveyor  22  at a speed S 4  equal to one half the difference of speeds S 3  and S 2  to adjust the path  44  of the strip material  34  by increasing the length of the path of the strip material. If speed S 2  is greater than speed S 1 , then a greater amount of tension is placed on the roller  108 . The tension on the roller  108  overcomes the pull of springs  132 ,  134  and the metal contact  112  comes into engagement with contact  126 , thereby closing a circuit that includes the power supply  118  and detection apparatus  142 . The detection apparatus  142  then causes activation of the servomechanism  100  (see FIG. 2) to move the center conveyor  22  at a speed S 4  equal to one half the difference between speeds S 3  and S 2  in direction A as shown in FIG. 2 to release strip material  34  taken up by prior movement of the center conveyor and thereby decrease the length of the path  44  of the strip material. 
     With reference to FIG. 4, a conveyor assembly  10  is shown with the proximity switch  106  at the end  72  of the center conveyor  22 . Additionally, a second proximity switch  106 ′ is located at the end  60  of the upper conveyor  16 . The second proximity switch  106 ′ further enables the conveyor assembly  10  to detect changes in tension in the strip material  34  by detecting a loop  152  that forms around the end  60  of the upper conveyor  16 . The second proximity switch  106 ′ has a roller  108 ′, contacts  124 ′ and  126 ′ and is also connected to the servomechanism  100  that controls the speed S 4  of the center conveyor  22 . 
     With continuing reference to FIGS. 1,  2 ,  3 , and  4 , the conveyor assembly  10  may employ more than one center conveyor  22  to increase the capacity of the conveyor assembly to accommodate changes in the length of the strip material  34  caused by intermittent feeding of strip material at the takeaway position  46 . Each center conveyor  22  may be equipped with either an optical sensor  88  or proximity switch  106  to detect a loop  90  in the strip material  34  at the end of the center conveyor. The strip material  34  may also be fed through the conveyor assembly  10  to a supply position  40  along the path  44  in the direction opposite that described heretofore. A computer may be connected to the servomechanisms  100  of the center conveyors  22  for controlling their movement during intermittent operation of the lower conveyor  28 . 
     While certain representative embodiments 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 scope of the invention.