Abstract:
Tire changer apparatus having
       a horizontally extended frame; a wheel holder device provided on said frame and designed to support a tired wheel ( 14 ) with horizontally positioned wheel axis; a carriage supported movably along the frame; a tool holder provided on the carriage; at least one tire changing tool for mounting the tire onto the wheel and/or for demounting the tire from the wheel; and actuator means to move the tool holder on the carriage to operating positions in which the tire changing tool is able to act on the tire for mounting or demounting on both sides of the tire, wherein during the mounting operation or demounting operation the carriage is driven by an actuator device along the frame; the tool holder is movably supported on a tool holder carriage which is movably supported on said carriage and driven by an additional actuator device provided on said carriage, and said additional actuator device is in drive connection with the tool holder carriage via a mechanical speed-increasing transmission.

Description:
TECHNICAL FIELD 
     The present invention concerns a tyre changer apparatus. 
     BACKGROUND 
     An apparatus of that kind is known from EP 1 334 846 B1. The known apparatus has a wheel holder device provided on a frame. The wheel holder device supports the tyred wheel with horizontally positioned wheel axis. A carriage provided with tyre changing tool is movably supported on the frame along guides. The tyre changing tool is supported on the carriage by means of a tool holder which can be rotated about its longitudinal axis. To move the tyre changing tool to operation positions in which the tool is able to act on the tyre for mounting or demounting on one of the both sides of the tyre, the carriage is moved along the guides of the frame and the tool holder is rotated synchronously with the movement of the carriage. To create the forces which are needed for the mounting or demounting actions of the tool, the carriage is driven by an actuator. Thus, the carriage of the known apparatus is used for the movement of the tool between its two operation positions and for the transmission of the forces which are needed for the mounting and demounting actions. 
     The object of the invention is to provide a tyre changer apparatus with which the time for the movement of the tyre changing tool between its two operation positions and the tool stroke adjusted can be shortened. 
     That object is solved by features in accordance with the invention. Advantageous modifications of the invention are characterized in an embodiment. 
     SUMMARY 
     According to the invention, the tool holder is movably supported on a tool holder carriage which is movably supported on the carriage which is driven by an associated actuator device during the mounting action and the demounting action. The tool holder is driven by an additional actuator device provided on the carriage. The additional actuator device is in drive connection with the tool holder carriage via a mechanical speed-increasing transmission. 
     The inventive tyre changer provides an automatic and rapid movement of the tool especially for heavy vehicle wheels from the active (operating) position on one side of the wheel to the active (operating) position on the other side of the wheel. It is possible to define the movement of the tool-holder carriage beforehand and the tool stroke can be adjusted and optimized in dependence of the width of the tyre. It does not require other input from the operator except that related to starting respective step. Further, a compact and fast transmission for the tool-holder carriage for its travel along a direction parallel with the axis of the wheel are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in detail with reference to the drawings which show in: 
         FIG. 1  an embodiment of the invention; 
         FIG. 2  parts of the embodiment of  FIG. 1  in exploded depiction; 
         FIG. 3  the parts of  FIG. 2  in assembled depiction; 
         FIG. 4  an additional actuator device and a speed-increasing transmission used in  FIG. 1 to 3 ; 
         FIG. 5  different positions of the tyre changing tool; 
         FIG. 6  a block diagram of a control device to control the motion of the tyre changing tool; and 
         FIG. 7  a flow chart demonstrating the operation of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a tyre changer machine for wheels of industrial or heavy vehicles like trucks, power shovels, tractors, etc. The machine has a frame  13  on which a wheel-holder arm  12  of a wheel holder device pivots. Said arm supports a wheel clamping and centring device  11  which constrains a wheel  14  to the arm  12 . One end of the frame  13  supports a carriage  5  which moves in a direction parallel with the axis  15  of rotation of the wheel. A tool-holder carriage  3  slides on said carriage  5  and can move along a direction parallel with the axis  15  of the wheel  14 . On the tool-holder carriage  3  there is a tool holder  4  on which a tyre changing tool  2  is placed. The carriages  3  and  5  are moved by suitable actuators and are designed to move the tool  2  in a direction parallel with the axis  15  of rotation of the wheel  14  so as to be able to carry out the operations for mounting, demounting or bead breaking on one side or on the opposite side of the wheel  14 . By convention “a” shall be the side of the wheel  14  closest to the wheel-holder arm  12  and “b” shall be the opposite side of the wheel  14 . A tool actuator  6  ( FIG. 2 ) acts on the tool holder  4  in such a way that the tool  2  can be moved from an active operating position (Pos.  1  and  4  in  FIG. 5 ) to an non-operating position (Pos.  2  and  3  in  FIG. 5 ) respectively required during the steps of use and the steps of movement of the tool from side “a” to side “b”. A rotary tool drive  7  allows the tool to be rotated relative to the tool holder  4  in a direction or the diametrically opposed direction. Said directions are parallel with the axis of the wheel, depending whether operations are performed on side “a” or “b” of the wheel  14 . 
     During normal tyre mounting, demounting or bead breaking operations on or from the rims of wheels of heavy vehicles, a step is usually needed in which the tool  2  is moved from one side of the tyre to the other side. This step is required when, after performing the mounting, demounting or bead breaking operation on the bead of one side of the tyre, the tool  2  must perform the same operation on the opposite bead. This movement requires the operation of a set of controls used to activate suitable actuators which move the tool  2 , the tool holder  4  and the tool-holder carriage  3 . 
     To describe these steps, without being too general, it may be assumed that during the initial step the tool  2  is on the inner side “a” of the tyre, with the tool  2  facing the bead. After performing the mounting, demounting or bead breaking operation on the bead on or from the rim, the tool holder  4  must be moved to the outer side “b” of the wheel  14 , with the tool  2  facing the inner bead. Therefore the tool  2  has to be rotated through 180° relative to the axis of rotation of its tool holder  4 . 
     The steps from Pos  1  to Pos  4  in  FIG. 5  are carried out by means of a piece of automated equipment which allows the entire operation to be performed by operating a simple control. 
     Said result is obtained thanks to the presence of a set of control devices:
         1) A position transducer  8  which allows a control of the tool-holder carriage  3  travel along is trajectory parallel with the axis  15  of rotation of the wheel  14 .   2) A detector  9 , for example a microswitch, for detecting tool positioning in the operating position (tool lowered, Pos.  1  and  4  in  FIG. 5 ).   3) A detector  10 , for example a microswitch, for detecting tool positioning in the non-operating position (tool raised, Pos.  2  and  3  in  FIG. 5 ),   4) Electronic control device (CPU) in  FIG. 6 .       

     The position transducer  8  allows a piece of automated equipment to be produced which allows the tool-holder carriage  3  stroke to be set using a graduated control, for example a potentiometer. According to the wheel width, the operator may select the appropriate stroke to be performed by the tool-holder carriage  3  during the operation. 
     After presetting the travel (stroke) of the tool-holder carriage  3 , the operator presses the respective Start button (from “a” to “b” or from “b” to “a”) to allow the entire operation ( FIG. 7 ) to be performed:
         1) The detector  9  allows acknowledgement that the tool holder  4  is in the operating position (Pos.  1  or  4  in  FIG. 5 ) and allows it to be raised by operation of the tool actuator  6  moving it to the non-operating position (Pos.  2  or  3  in  FIG. 5 ).   2) The detector  10  is operated when the tool holder  4  reaches the non-operating position (Pos.  2  or  3  in  FIG. 5 ). At this point the tool actuator  6  is inhibited and joint or sequential consent is given to the actuator which operates the rotary tool drive  7  for rotation of the tool holder  4  and to the actuator device  18  designed to operate a mechanical speed-increasing transmission  17  which drags the tool-holder carriage  3 .   3) The position transducer  8  indicates that the tool-holder carriage  3  has completed the present travel. Then the actuators of the rotary tool drive  7  and  16  related to rotation of the tool holder  4  and to the mechanical transmission  17  are inhibited and the tool actuator  6  is operated to move the tool holder  4  to the new operating position until the detector  9  is activated, and the tool  2  is therefore ready to carry out the next demounting, mounting or bead breaking step on the bead from or on the rim on the inner side of the wheel  14 .    To carry out said steps of demounting, mounting or bead breaking, the carriage  5  is driven by an associated actuator device (not shown).       

     The  FIG. 5  shows the following positions of the tyre changing tool  2 :
     Pos.  1 : The tool  2  is in the operating position on one side (side b) of the wheel  14 .   Pos.  2 : The tool-holder carriage  3  is kept stationary, the tool  2  is moved to the non-operating position.   Pos.  3 : The tool-holder  4  is in the non-operating position, the tool holder carriage  3  moves along a direction parallel with the axis  15  of the wheel  14  until it reaches the inner side “a” of the wheel  15 . Before, during or immediately after said translation movement, the tool holder  4  rotates through 180° about its own axis of rotation, so that the tool  2  is angled in the active operating position for use on the inner side “a” of the wheel  14 .   Pos.  4 : The tool is moved to the operating position, now on the side “a” of the wheel opposite that of pos.  1 .   

     The mechanical speed-increasing transmission  17  provides a solution for dragging the tool-holder carriage  3  on the carriage  5  by means of a transmission chain  23  wound in a loop over two free gear wheels  24 ,  25  positioned at the ends of the carriage  5  and constrained to it in such a way that they can rotate about their own axes ( FIG. 4 ). 
     The transmission chain  23  is wound in the kinematic mechanism in such a way that it has a straight stretch between the gear wheels  24 ,  25  extending for a length not less than the travel required of the tool-holder carriage  3 . The tool-holder carriage  3  is anchored at said stretch by means of a connecting element  30  which constrains the carriage  3  to a link of the chain  23 . 
     The chain  23  is driven by a driving sprocket  22  in turn driven by a sprocket  21  with which it is constrained to rotate integrally about a shared sprocket axis  31  wherein the two sprockets  21 ,  22  forms a gear wheel providing a predetermined gear ratio. The sprocket  21 ,  22  are rotatably supported at the carriage  5  to which their shared sprocket axis  31  is constrained. Finally, the sprocket  21  is driven in rotation by the translation of a toothed rack  19  driven by a linear actuator  18 . The actuator  18  having one end constrained to the carriage  5  and the other end constrained to the rack  19  causes the rack  19  to translate from a first position to a second position respectively corresponding to the fully retracted configuration and the fully extracted configuration of the linear actuator  18 . Therefore, the tool-holder carriage  3  correspondingly translates from an initial position to a final position, covering a measurement equal to the actuator travel multiplied by the ratio of the pitch circle diameter of the driving sprocket  22  to the pitch circle diameter of the sprocket  21  (gear ratio). Once an appropriate gear ratio has been selected, the solution just described allows production of a transmission using a linear actuator  18  whose dimensions along the direction of translation of the tool-holder carriage  3  is less than the dimension given by the two limit positions of the carriage  3  on the carriage  5 . 
     The advantage of being able to set the actuator travel effects a reduction in the times required for the operation to demount the tyre from the rim, in particular, with reference to the tubeless wheels of heavy vehicles (trucks), when the tool can move from one operating position to the other (from one side of the tyre to the other), with a simple control. If the tyre width is known, this travel, which can be set, allows the tool to perform the minimum travel in order to move to the operating position. In this way, it is also possible to reduce the movements for the tool approach to the side of the tyre required after positioning said operating position. 
     A transmission such as the one described above provides a solution for carriage movement using a linear actuator which allows it to be kept compact. Linear actuator dragging systems usually require additional space due to the presence of the cylinder chamber. The solution just described allows production of a transmission in which the linear actuator  18  (cylinder), by means of suitable sizing of the travel gear ratio, has dimensions such that the system does not require additional space to that of the tool holder travel required b the function which must be performed. The invention provides a device for tyre changer machines which allows the tool  2  to pass from one side of the tyre to the other automatically with electric control as described above. 
     The mechanical transmission device as described above allows the dimensions of the actuator  18  along the direction of movement of the tool-holder carriage, to be kept less than the dimensions required by the tool-holder carriage path. The invention shall also be valid for different kinds of transmission (using direct actuator, by means of other type of transmission, etc.) of a different type of actuator (hydraulic, electric motor, etc.). The transmission in accordance with the invention shall also be valid irrespective of the presence of the piece of automated equipment. 
     Tyre changer comprising at least one tyre changing tool and a controlled transmission device to pass the at least one tyre changing tool from one side of the tyre to its other side, wherein the dimensions of the stroke generated by the actuator  18  along the direction of the movement of the tool holder  4  are less than the dimensions of a tool holder carriage path. Thus the overall length of the additional actuator device  16  can be constructed shorter than the longest possible stroke of the tool holder carriage  3 . 
     REFERENCE LIST 
     
         
           1  wheel holder device 
           2  tyre changing tool 
           3  tool holder carriage 
           4  tool holder 
           5  carriage 
           6  tool actuator 
           7  rotary tool drive 
           8  position transducer 
           9  position detector for the tool 
           10  position detector for the tool 
           11  wheel clamping and centering device 
           12  wheel holder 
           13  frame 
           14  wheel 
           15  wheel axis 
           16  additional actuator device 
           17  mechanical speed-increasing transmission 
           18  linear actuator 
           19  toothed rack 
           20  gear wheel 
           21  sprocket 
           22  sprocket 
           23  transmission chain 
           24  gear wheel 
           25  gear wheel 
           26  chain tensioner 
           27  electronic control device (CPU) 
           28  data display 
           29  start button (forward, reverse) 
           30  connecting element 
           31  sprocket axis