Patent Publication Number: US-2004046286-A1

Title: Method and device for vulcanizing tire

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to a tire curing method and a tire press for curing pneumatic tires and, more particularly, to a tire curing method and a tire press using a sectional type mold.  
       TECHNICAL BACKGROUND  
       [0002] In general, a tire press using a sectional type mold, as shown in FIG. 24, includes an annular lower mold section  203  fixed to the upper surface of a lower plate  201 , an annular upper mold section  205  located above the lower mold section  203 , and a side mold section comprising a plurality of sectors  207  placed radially outwardly of the upper mold section  205 .  
       [0003] The upper mold section  205  is attached to an upper mold support plate  213  which is located under an upper plate  209  and can be vertically moved by a cylinder  211 . Fixedly secured to the outer peripheral side of each sector  207  is a holding segment  215 , which is attached to each of guide segments  217  hanged from the outer peripheral portion of the upper plate  209  and can slide in a vertically inclined direction.  
       [0004] Provided on the upper surface of the upper plate  201  is a subplate  221 , on the upper surface of which are mounted a plurality of guide rails  223  extending in the radial direction of the annular lower mold section  203 , the holding segments  215  being engagable with and disengagable from the guide rails  223 .  
       [0005] Installed radially inwardly of the lower mold section  203  is a center mechanism  227  having a bladder  225  which can be vertically moved. The upper plate  209  can be moved up and down by the rod  229   a  of an elevating means  229 . In the drawing, reference numeral  231  denotes an upper mold bead ring and reference numeral  233  demotes a lower mold bead ring.  
       [0006] According to the above tire press, the bladder  225  is expanded and holds a green tire which has loaded and the upper mold section  205  is lowered to a starting position for closing the mold by means of the cylinder  221 . The upper plate  209  is then lowered by extension of the rod  229   a  of the elevating means  229  to set the upper mold section  205  to one side portion Wa (upper side of the drawing) of the green tire W while the lower mold section  203  is set to the other side portion Wa (lower side of the drawing) of the green tire W.  
       [0007] Meanwhile, the holding segments  215  are lowered by the lowering of the upper plate  209 , are engaged with the radially extending guide rails  223 , and are then advanced toward the center along the guide rails  223  to set the sectors  207  to the tread portion Wb of the green tire W. After the mold has set to the green tire W as described above, a hot pressure fluid is supplied into the bladder  225 , as described in the arrow Q, to inflate the green tire W. After that, a steam for heating is supplied through steam passages, not shown, to heat and cure the green tire W, thereby obtaining a vulcanized pneumatic tire.  
       [0008] The conventional tire press discussed above, however, must use the upper plate  209  which is thick and heavy in order to strengthen it, since the upper plate  209  supports components such as heavy side and upper mold sections. A support structure for supporting the upper plate  209  above is large in size and the elevating means  229  for vertically moving the thick and heavy upper plate  209  is also required to be large in size. As a result, there are problems such that the entire tire press is large in size and a large space for installation is required.  
       [0009] Since the holding segments  215  are arranged so as to be engaged with and to be disengaged from the guide rails  223 , a certain amount of clearance is needed between each holding segment  215  and each guide rail  223  to reliably engage the holding segments  215  with the guide rails  223 . Due to the clearance, the sectors  207  which have set are moved by a pressure applied to the sectors  207  from their inner sides during vulcanization, thereby deteriorating the uniformity of vulcanized pneumatic tires.  
       DISCLOSURE OF THE INVENTION  
       [0010] It is an object of the present invention to provide a tire curing method and a tire press which can be small in size and reduce a space for installation.  
       [0011] It is another object of the present invention to provide a tire curing method and a tire press which can improve the uniformity of vulcanized tires.  
       [0012] In order to achieve the aforementioned object, the present invention provides a tire curing method for curing a green tire by means of a tire press having a sectional type mold which includes an annular lower mold section secured to an upper surface of a lower plate, an annular upper mold section disposed under an upper plate vertically moveably placed above the lower plate so that the upper mold section moves vertically along with the upper plate, and a side mold section having a plurality of sectors divided along a circumferential direction thereof and located radially outwardly of the lower mold section in an openable and closable manner, wherein holding segments which hold the sectors are provided on outer peripheral sides thereof, the holding segments being placed on the lower plate so as to move forward and away from a center of the annular lower mold section, guide segments which are engagable with and disengagable from outer peripheral sides of the holding segments being suspended from the upper plate radially outwardly of the upper mold section, first heating means being provided under the lower mold section, second heating means being provided over the upper mold section, and third heating means being provided on the outer peripheral side of each of the sectors, the method comprising the steps of: engaging the guide segments with the holding segments to cause the holding segments to move forward; closing the sectors to set the green tire in the mold; applying a pressure into the set green tire to inflate it; and heating the green tire by the first, second and third heating means to cure it.  
       [0013] A tire press according to the present invention includes a sectional type mold which has an annular lower mold section secured to an upper surface of a lower plate, an annular upper mold section disposed under an upper plate vertically moveably placed above the lower plate so that the upper mold section moves vertically along with the upper plate, and a side mold section having a plurality of sectors divided along a circumferential direction thereof and located radially outwardly of the lower mold section in an openable and closable manner, wherein holding segments which hold the sectors are provided on outer peripheral sides thereof, the holding segments being placed on the lower plate so as to move forward and away from a center of the annular lower mold section, guide segments which are engagable with and disengagable from outer peripheral sides of the holding segments being suspended from the upper plate radially outwardly of the upper mold section and being arranged such that the engagement of the guide segments with the holding segments causes the holding segments to move forward and backward to close and open the sectors, first heating means being provided under the lower mold section, second heating means being provided over the upper mold section, third heating means being provided on the outer peripheral side of each of the sectors, and the green tire set in the mold being curable by the heating means.  
       [0014] As described above, since the sectors and the holding segments are mounted on the lower plate side, the weight of the components supported by the upper plate can be reduced much less than that of the components in the prior art, thereby allowing the upper plate which supports the components to be smaller in size and to be lighter in weight than before. Also, associated components supporting the upper plate can be reduced in size and in weight. In addition, means for vertically moving the upper plate is reduced in size. Accordingly, the tire press can be minimized in size, and the space for installing the tire press can be reduced. Also, electric power consumed by the means for vertically moving the upper plate is reduced, thereby allowing a decrease in power consumption.  
       [0015] The holding segments are always in engagement with the lower plate side, and do not have a structure such as the prior art in which the holding segments engage therewith and disengage therefrom, whereby the clearance between the engagement parts can be smaller than that of the prior art. Thus, movement of the sectors due to pressure applied to the sectors from its radially inner side can be less than is known in the prior art, thereby allowing tire uniformity to be improved. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 is a cross-sectional view showing a tire press according to the present invention in an open state, taken along the line I-I of FIG. 3;  
     [0017]FIG. 2 is a cross-sectional view, corresponding to FIG. 1, showing the tire press of FIG. 1 in a closed state, which, for the sake of easy understanding, includes a section of a holding segment engaged with a guide segment and a section of a positioning pin engaged with a positioning member;  
     [0018]FIG. 3 is an illustrative plan view showing a state in which the guide segments engage with the holding segments holding the sectors in the closed condition shown in FIG. 2;  
     [0019]FIG. 4 is a cross-sectional view showing a state in which the holding segment engages with guide rails;  
     [0020]FIG. 5 is an enlarged cross-sectional view of a guide segment and a holding segment shown in FIG. 1, taken along the line V-V and the line V′-V′ of FIG. 6;  
     [0021]FIG. 6( a ) is a cross-sectional view of the guide segment, taken along the line VI-VI of FIG. 5;  
     [0022]FIG. 6( b ) is a cross-sectional view of the holding segment, taken along the line VI′-VI′ of FIG. 5;  
     [0023]FIG. 7 is a perspective view of a preferred first sealing means;  
     [0024]FIG. 8 is a vertically cross-sectional view of the first sealing means in FIG. 7;  
     [0025]FIG. 9 is a vertically cross-sectional view showing a state in which the first sealing means of FIG. 8 engages with a stop means when the mold is clamped;  
     [0026]FIG. 10 is a vertically cross-sectional view of another preferred first sealing means;  
     [0027]FIG. 11 is a vertically cross-sectional view showing a state in which the first sealing means of FIG. 10 engages with a stop means when the mold is clamped;  
     [0028]FIG. 12 is a plan view of FIG. 2;  
     [0029]FIG. 13 is an illustrative cross-sectional view showing a locking means in a locking state;  
     [0030]FIG. 14 is an illustrative cross-sectional view showing the locking means of FIG. 13 in an unlocking state;  
     [0031]FIG. 15 is an enlarged partial cross-sectional view of peripheral parts of the lower mold section;  
     [0032]FIG. 16 is a plan view of the upper mold support plate;  
     [0033]FIG. 17 is a cross-sectional view taken along the line XVII-XVII of FIG. 16;  
     [0034]FIG. 18 is a cross-sectional view taken along the line XVIII-XVIII of FIG. 19;  
     [0035]FIG. 19 is a plan view of the holding segment to which electric heaters are attached;  
     [0036]FIG. 20 is an enlarged plan view of the electric heater;  
     [0037]FIG. 21 is a front view of FIG. 20;  
     [0038]FIG. 22 is a partial plan view showing positioning means;  
     [0039]FIG. 23 is a cross-sectional view showing another tire press according to the present invention in an open state; and  
     [0040]FIG. 24 is a partial cross-sectional view showing a conventional tire press. 
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION  
     [0041] With reference to FIG. 1, there is shown a tire press according the present invention, which includes a plurality of support members  1  which stand on a base surface B, and a horizontally extending base plate  3  which is placed on the upper ends of the support members  1 . The base plate  3  is formed square in shape as shown in FIG. 3, and has a circular opening in its center as shown in FIG. 1.  
     [0042] Attached on the base plate  3  is a square-shaped lower plate  5  with its corners being cut off. The lower plate  5  has a center region  5   a  in the center of which is formed a circular opening  5   c.    
     [0043] Mounted on the upper surface of the center region  5   a  is an annular lower mold section  7  for molding one side portion W 1  of a green tire W. Affixed to an inner peripheral side of the lower mold section  7  is a lower mold bead ring  9  for molding one bead portion W 2  of the green tire W.  
     [0044] Radially outwardly of the lower mold section  7  there is provided a side mold section  11  for molding a tread portion W 3  of the green tire W. The side mold section  11  comprises a plurality of sectors  11   a  into which a toroid is divided along its circumferential direction. A holding segment  13  holding the sector  11   a  is disposed radially outwardly of each sector  11   a . Each sector  11   a  is detachably fastened to each corresponding holding segment  13  by means of screws, not shown.  
     [0045] A plurality of guide rails  15  for moving the sectors  11   a  between a mold open position and a mold closed position, as shown in FIG. 3, are provided on an outer periphery of the upper surface of the lower plate  5  and extend straight toward the center side. As shown in FIG. 4, placed on each pair of parallel guide rails  15  is a holding segment mounting plate  19  having on its lower surface linear bearings  17  which engage with the parallel guide rails  15 . Each holding segment  13  is fixed on the upper surface of each holding segment mounting plate  19  via a thermal insulating layer  21  which is formed from a composite composed of fiber glass and heat-resistant resin such as epoxy resin having thermal durability. Each holding segment  13  can move along the guide rails  15  toward and away from the center of the lower mold section  7 , and each sector  11   a  can be moved between the mold open position and the mold closed position by the movement of each holding segment  13 .  
     [0046] Each holding segment  13  has a vertically extending depression  13   b  on an outer peripheral surface  13   a  thereof, as shown in FIGS. 5 and 6. The depression  13   b  has on both wall surfaces of its bottom portion grooves  13   x  which extend along the depression extending direction. The bottom surface  13   c  which is flat and includes one wall surface of each of the grooves  13   x  is a sloping surface inclined so that its lower side is radially outwardly of its upper side. A plate member  13   d  for reducing the frictional resistance of a guide segment described later is provided so that one surface of the plate member  13   d  is located in the same plane as the bottom surface  13   c.    
     [0047] A stop means  23  for preventing the holding segments  13  from moving backward during vulcanization is provided on a peripheral portion of the upper surface of the lower plate  5  which is positioned radially outwardly of the holding segments  13 . The stop means  23  comprises a cylindrical member  23 A securely mounted on the upper surface of the lower plate  5  so as to surround the entire holding segments  13 . The cylindrical member  23 A is hermetically mounted on the upper surface of the lower plate  5  because it is used as a part of a first sealing means described later.  
     [0048] A projecting shelf portion  25  which is triangular in shape when seen from the top, as shown in FIG. 3, is provided between each pair of the guide rails  15  on the upper surface of the lower plate  5 . A cylindrical positioning part  27  to which a positioning pin described later is engaged in a fitting manner projects from the upper surface of every other shelf portion  25 .  
     [0049] A center mechanism  31  with a bladder  29  for vulcanization is provided radially inwardly of the lower mold section  7 . The center mechanism  31  includes a first cylinder  35  attached to the center of a support frame  33  (center of the lower mold section  7 ) hanged from the periphery of the opening  3   a  of the base plate  3 . The vertically extending rod  35   a  of the first cylinder  35  is an elevating post vertically moved by operation of the first cylinder  35 .  
     [0050] A plurality of second cylinders  37  are attached to the supporting frame  33  around the first cylinder  35 . Secured to the upper ends of upwardly extending rods  37   a  of the second cylinders  37  is a lower bladder attachment member  39  to which the lower end of the cylindrical vulcanization bladder  29  is attached. When the second cylinders  37  are operated, the rods  37   a  are moved up or down, thereby raising or lowering the lower bladder attachment member  39 . The first and second cylinders  35  and  37  extend into a pit  41  formed on the base surface B. Fixed on the upper surface of the lower bladder attachment member  39  is an emission member  42  having supply ports for radially emitting a thermal pressurized medium into the vulcanization bladder  29 . A passageway  45  in communication with the emission member  42  is formed in the lower bladder attachment member  39 , and a supply pipe  47  for supplying a thermal pressurized medium is connected to the passageway  45 . The supply pipe  47  is connected to a thermal pressurized medium supplying source, not shown.  
     [0051] The elevating post (rod  35   a ) upwardly extends through the lower bladder attachment member  25 . An upper bladder attachment member  49  is fixedly attached to the upper end of the elevating post. The vulcanization bladder  29 , the upper end of which is gripped by the upper bladder attachment member  49 , is provided on the upper side of the elevating post which vertically movably stands.  
     [0052] A horizontally extending upper plate  51  is placed above the lower plate  5 . The upper plate  51  slidably engages with a plurality of columns  55  mounted between the base plate  4  and a horizontally extending top plate  53  which is placed above the upper plate  51  and is shaped in square, and moves vertically along the columns  55 .  
     [0053] A discoid upper mold support plate  57  is provided under the central part of the upper plate  51 . Affixed on the lower surface of the upper mold support plate  57  is an annular upper mold section  59  for molding the other side portion W 4  of the green tire W. Fixed to an inner peripheral side of the upper mold section  59  is an upper mold bead ring  61  for molding the other bead portion W 5  of the green tire W.  
     [0054] Connected to the upper surface of the upper mold support plate  57  are the lower ends of the vertically extending rods  63   a  of elevating cylinders  63  which are mounted on the upper plate  51  and arranged in a predetermined interval along its circumferential direction. There are provided on an outer peripheral part of the upper surface of the upper mold support plate  57  a plurality of guide rods  65  vertically extending through the upper plate  51  and arranged in a predetermined interval along the circumferential direction of the upper mold support plate  57 . The rods  63   a  extend or retract by activation of the elevating cylinders  63 , thereby allowing the upper mold support plate  57  to be moved up or down with the support plate  57  guided by the guide rods  65 .  
     [0055] Guide segments  69  having the same number as the holding segments  13  are hanged radially outwardly of the upper mold support plate  57  from the lower surface of the upper plate  51  in a predetermined interval along its circumferential direction via a ring-shaped segment attachment member  67 . Each guide segment  69  comprises a segment body  71  which engages with the holding segment  13 , and a stop means engaging member  73  attached to the outer peripheral side of the segment body  71 .  
     [0056] Each segment body  71 , as shown in FIG. 6 a , has on both side surfaces thereof projections  71   a  which are engagable with the grooves  13   x  formed in the depression  13   b  of the holding segment  13 . The guide segment  71  has an inner peripheral surface  71   b  which is a flat sloping surface with the same angle as the bottom surface  13   c  in the depression  13   b  of the holding segment  13 . The projections  71   a  extend along the inner peripheral surface  71   b . One side surface of each projection  71   a  is formed so that it is located in the same plane as the inner peripheral surface  71   b , and a plate member  71   c  for reducing the frictional resistance of the holding segment  13  which comes into sliding contact therewith is provided on the other side surface.  
     [0057] When the guide segments  69  are lowered by lowering of the upper plate  51 , the segment bodies  71  are engaged with the depressions  13   b  of the holding segments  13  with the projections  71   a  being engaged with the grooves  13   x . When further lowered, the holding segments  13  are pushed by the guide segments  69 , and moved radially inward along the guide rails  15 , thereby moving the sectors  11   a  from the mold open position (position in FIG. 1) toward the mold closed position. When the guide segments  69  are raised by elevation of the upper plate  51  in the mold closed position shown in FIG. 2, the holding segments  13  are pulled by the guide segments  69 , and moved radially outward, thereby moving the sectors  11   a  toward the mold open position, where the holding segments  13  are disengaged from the upwardly moving guide segments  69 . The guide segments  69 , as described above, are engagable with and disengagable from the holding segments  13 .  
     [0058] An inclined angle α of the bottom surface (engaged surface)  13   c  in the depression  13   b  formed in the outer peripheral surface  13   a  of the holding segment  13 , and an inclined angle β of the inner peripheral surface (engaging surface)  71   b  of the segment body  71  which comes into sliding contact therewith, with respect to the vertical direction, are preferably 15 to 20 degrees. If the inclined angles α and β are out of the above range, it is difficult that the vertically lowering guide segments  69  smoothly engages with the holding segments  13 . The angles may more preferably be about 18 degrees.  
     [0059] Each holding segment  13  has a sloping wall surface (wall surface in a radially outer position)  13   y  which faces each groove  13   x  and comes into sliding contact with the plate member  71   c  provided on the other side of the projection  71   a  of the segment body  71 , the upper end  13   z  of the sloping wall surface  13   y , as shown in FIG. 5, being preferably chamfered in a circular arc having a radius of 10 to 30 mm to form a curved surface, thereby making the guide segments into smooth engagement with the holding segments  13 .  
     [0060] The stop means engaging members  73 , which are formed in a shape having a projecting lower part, are detachably fastened to the outer peripheral surfaces of the segment bodies  71  by means of bolts, not shown. When vulcanized after the sectors  11   a  have been moved to the mold closed position, the stop means engaging members  73  come into contact with the stop means  23  and prevent the holding segments  13  from moving backward by an inner pressure applied into the bladder  29  not to open the sectors  11   a . A clearance between the stop means  23  and each stop means engaging member  73 , when the sectors  11   a  are in the mold closed position prior to vulcanization, may be substantially 0.1 to 0.2 mm. If the clearance is less than 0.1 mm, there is a risk that a problem may occur such as contact between the stop means  23  and the stop means engaging members  73  when the guide segments  69  are lowered. If the clearance is more than 0.2 mm, it is not preferable since the rubber is overflowed from gaps produced when the holding segments are moved back by the inner pressure during vulcanization.  
     [0061] The guide segments  69  each may be formed from a single member which integrally has a segment body  71  and stop means engaging member  73 , but may preferably be of a two-peace structure as mentioned above. In the case of employing such structure, the clearance between the stop means  23  and each stop means engaging member  73  can be easily adjusted by attaching a new stop means engaging member  73  to the segment body  71 , or by placing a spacer, not shown, between the stop means  23  and each stop means engaging member  73 .  
     [0062] Positioning pins  74 , which can fit within the positioning parts  27 , project downwardly from places, corresponding to respective positioning parts  27  between the guide segments  69 , of the lower surface of the segment attachment member  67 .  
     [0063] A first sealing means  75  for hermetically sealing the entire mold during vulcanization is provided on the lower surface of the upper plate  51  radially outwardly of the segment attachment member  67 . The first sealing means  75  comprises a first sealing cylindrical assembly  77  which is attached to the lower surface of the upper plate  51 . The first sealing cylindrical assembly  77  includes an upper ring member  81  which is hermetically fixed to the lower surface of the upper plate  51 , and a lower ring assembly  85  which is attached to the lower peripheral side of the upper ring member  81 . The lower ring assembly  85  includes a fixed ring member  85 A hermetically fixed to the upper ring member  81 , and a slide ring member  85 B hermetically attached to the outer peripheral side of the fixed ring member  85 A. The slide ring member  85 B is vertically slidably coupled to the fixed ring member  85 A by means of coupling rods  85 C placed in a predetermined interval along the ring circumferential direction, and is lowered by its own weight.  
     [0064] As shown in FIGS.  7  to  9 , it is preferable that the first sealing cylindrical assembly  77  is constructed such that the slide ring member  85 B is always urged downward by means of springs  91 . The first sealing cylindrical assembly  77  shown here has a lower ring assembly  85  hermetically attached via an O-shaped sealing ring  79  to the lower end face of the upper ring member  81  hermetically fixed to the lower surface of the upper plate  51 . The lower ring assembly  85  includes a fixed ring member  85 A hermetically fixed to the lower end face of the upper ring member  81  via the sealing ring  79 , and a slide ring member  85 B hermetically attached to the lower outer-peripheral side of the fixed ring member  85 A via an O-shaped sealing ring  83 . The slide ring member  85 B is vertically slidably coupled to the fixed ring member  85 A by means of coupling means  87  located in a predetermined interval along the ring circumferential direction.  
     [0065] Each of the coupling means  87  includes a metal plate piece  87   b  having a vertically extending elongated opening  87   a , and the metal plate piece  87  is fastened at its upper end by means of a bolt  87   c  against the outer peripheral surface of an annular flange portion  85 A 1  formed on the upper part of the fixed ring member  85 A. Bolts  87   d  protrude from the upper end outer-peripheral surface of the slide ring member  85 B, and the heads of the bolts  87   d  engage with the elongated openings  87   a . The lower surface of the flange portion  85 A 1  of the fixed ring member  85 A has holes  85 A 2  in a predetermined interval along the ring circumferential direction, and pins  88  protrude downwardly from the bottom faces in the holes  85 A 2 . The upper end surface of the slide ring member  85 B has holes  85   a  in a predetermined interval along the ring circumferential direction, into which the pins  88  can be inserted. Coil springs  91  are each placed between both corresponding holes  81   b  and  85   a  with each spring  91  surrounding each pin  88 , and always urge the slide ring member  85 B downwardly.  
     [0066] An O-shaped sealing ring  89  is attached to the lower surface of the slide ring member  85 B, whereby the slide ring member  85 B can hermetically be engaged with a circular flange portion  23 B formed on the top of the cylindrical member  23 A constituting the stop means  23 . The first sealing means  75  located between the upper plate  51  and lower plate  5  surrounds the entire mold hermetically during vulcanization in such a manner that, as shown in FIG. 9, the lower end of the slide ring member  85 B comes into contact with the cylindrical member  23 A with the slide ring member being engaged with the flange portion  85 A 1  of the fixed ring member  85 A.  
     [0067] The lower ring assembly  85  of the first sealing cylindrical assembly  77  may be formed as shown in FIGS. 10 and 11. In the lower ring assembly  85  shown here, pins  87   e  are used as coupling means  87  connecting the fixed ring member  85 A and slide ring member  85 B. The pins  87   e  are located between the flange portion  85 A 1  of the fixed ring member  85 A and the slide ring member  85 B, and fixed to the lower surface of the flange portion  85 A 1  with the upper ends of the pins  87   e  embedded therein. Straight grooves  85   b   2  are formed from the lower end face to the upper end portion of the slide ring member  85 B in a predetermined interval along the ring circumferential direction. Each upper end section  85 B 3  adjacent to each of the straight grooves  85 B 2  has a perforation  85 B 4  arranged such that it extends from the upper end face to the straight groove  85 B 2  of the slide ring member  85 B, and the lower sides of the pins  87   e  are inserted through the perforations  85 B 4 . Affixed to the lower ends of the pins  87   e  are Insertion keeping members  87   f  having a larger outer diameter than the diameter of the perforations. The lower end face of the fixed ring member  85 A has holes  85 A 3  in a predetermined interval along the ring circumferential direction. A circular flange portion  85 B 5  projects radially inwardly from the lower end of the slide ring member  85 B, and pins  90  which are insertable into the holes  85 A 3  are provided on the upper face of the flange portion  85 B 5  in a predetermined interval along the ring circumferential direction. Each coil spring  91  is mounted between the lower end of the pin  90  and the corresponding hole  81   c  and always urges the slide ring member  85 B downward to make it in the state of FIG. 10. As shown in FIG. 11, during curing, the lower end of the slide ring member  85 B comes into contact with the flange portion  23 B of the cylindrical member  23 A with the slide ring member being in contact with the flange portion  85 A 1  of the fixed ring member  85 A, and the first sealing means  75  hermetically surround the whole mold.  
     [0068] Provided on the lower surface of the upper plate  51  radially inwardly of the segment attachment member  67  is a second sealing means  92  which makes a hermetical seal between the upper plate  51  and the upper mold support plate  57  during vulcanization so that the space including the guide rods  65  and the rods  63   a  of the elevating cylinders  63  are placed inside the second sealing means. The second sealing means  92  comprises a second sealing cylindrical assembly  93  which is provided on the lower surface of the upper plate  51 . The second sealing cylindrical assembly  93  includes an upper ring  95  hermetically fixed to the lower surface of the upper plate  51  through an O-shaped seal ring, not shown, and a lower ring  97  hermetically attached to the outer circumferential side of the lower side of the upper ring  95  through an O-shaped seal ring, not shown. The lower ring  97  is coupled to the upper ring  95  by connecting rods  98  located in a predetermined interval in the ring circumferential direction such that the lower ring  97  is vertically movable and lowered by its weight.  
     [0069] The hermetical engagement of the lower end of the lower ring  97  with the upper surface of the outer peripheral portion of the upper mold support plate  57  seals the through holes  51   a  of the upper plate  51  through which the guide rods  65  and the rod  63   a  penetrate. The second sealing means  92  may also be preferably structured as in the first sealing means  75 , as shown in FIGS.  7  to  11 .  
     [0070] Connected to a chamber  99  (see FIG. 2) hermetically surrounded by the first sealing means  75  is a suction means  101  for making the chamber vacuum. The suction means  101  includes a vacuum pump  101 A and a vacuum tank  101 B connected to the vacuum pump  101 A. The vacuum tank  101 B is communicatingly connected to the chamber  99  via a pipe  101 C. When the vacuum pump  101 A is operated, the air in the chamber  99  is sucked, thereby making the chamber  99  into a vacuum state.  
     [0071] There is provided on the top plate  53  a lifting means  103  for vertically moving the upper plate  51 . The lifting means  103  includes a hydraulic cylinder  105  which is placed on the center of the upper surface of the top plate  53 . The vertically extending rod  105   a  of the hydraulic cylinder  105  is fixedly attached at its lower end to the center of the upper surface of the upper plate  51 . The operation of the hydraulic cylinder  105  vertically extends and retracts the rod  105   a  to thereby move the upper plate  51  vertically with the upper plate  51  being guided by the columns  55 . The hydraulic cylinder  105  is also used to apply a clamping force on the upper mold section  59  during vulcanization.  
     [0072] There are provided on the top plate  53  a plurality (two in the drawings) of locking means  109  for making the upper mold section  59  locked in the state in which the upper mold section  59  is clamped by the hydraulic cylinder  105  in the mold clamping position. Each of the locking means  109 , as shown in FIG. 12, has a pair of hydraulic cylinder units  111  placed on the upper surface of the top plate  53 . Each of hydraulic cylinder units  111  includes a projectable stop  115  for preventing the raising of each of vertically extending locking shafts  113  which are provided on the upper surface of the upper plate  51  and penetrate through the top plate  53 .  
     [0073] The hydraulic cylinder units  111  of this type can preferably include one shown in FIGS. 13 and 14. The hydraulic cylinder unit  111  shown comprises a body  117 , a cylindrical piston  119  having a closed front end, and a stop  115 , the piston  119  and the stop  115  being horizontally slidably mounted in the body  117 . Attached to the front end of the piston  119  is a pushing member  121  for pushing the stop  115  into a projected position. A first spring  123  is placed inside the piston  119 , the first spring  123  always urging the piston  119  toward the front end side. A second spring  125  is attached between the stop  115  and a body wall  117   a  in the rear side (right side of FIG. 13), the second spring  125  always urging the stop  115  to be located in a retracted position. The first spring  123  has a spring force greater than the second spring  125 .  
     [0074] There are formed in the body  117  a first port  127  and a second port  129  to which hydraulic pipes  131  are connected. As shown in FIG. 13, oil transmitted from a hydraulic source  133  is supplied via a solenoid selector valve  135  to the first port  127  and thereby advances the piston to make the stop  115  into a projected state. This causes the stop  115  to come into engagement with the top end of the locking shaft  113 , thereby locking the locking shaft  113  such that the locking shaft  113  is prevented from raising. The stops  115  of two hydraulic cylinder units  111  come into engagement with each locking shaft  113  to lock it. This prevents the upper mold section  59  in the curing position (clamping position) from opening due to pressure applied inside during vulcanization.  
     [0075] As shown in FIG. 14, oil transmitted from the hydraulic source  133  is supplied to the second port  129  via the solenoid selector valve  135  to thereby retract the piston  119 . This causes the stop  115  to be pulled by the second spring  125  to be positioned in the retracted position, which results in release of the locking between the stop and the locking shaft  113 .  
     [0076] When oil leaks out of the pipes  131  or the like and the pressure of the oil supplied to the ports  127  and  129  becomes zero, the first spring  123  causes the piston  119  to advance to thereby keep the stop  115  in the projected state.  
     [0077] First heating means  137 , as shown in FIG. 15, are disposed inside the lower plate  5  under the lower mold section  7 , second heating means, as shown in FIGS. 16 and 17, are placed inside the upper mold support plate  57  above the upper mold section  59 , and third heating means  141 , as shown in FIGS. 18 and 19, are disposed inside the holding segments  13  on the peripheral side of the sectors  11   a , the heating means  137 ,  139  and  141  heating the green tire W set in the mold to cure it.  
     [0078] Each of the heating means  137 ,  139  and  141  may preferably employ, for example, an electric heater  143  as shown in FIGS. 20 and 21. The electric heater  143  includes a rod-shaped heating part  145  having a rod-shaped stainless steal sheath and a heating member encased therein, a vacuum terminal part  147  connected to one end of the heating part  145  and having terminals in a vacuum, and two cords  149  connected to the vacuum terminal part  147 . The vacuum terminal side of each of the cords  149  is covered with a thermal insulation tube  151  made of fluororesin.  
     [0079] The rod-shaped heating parts  145  of the first heating means  137  are radially located inside the lower plate  5  in a predetermined interval along the circumferential direction. The thermal insulation tubes  151  covering the cords  149  which are connected to the vacuum terminal part  147  pass through the inside of the lower plate  5  and are led outside. As shown in FIG. 15, there is provided inside the lower plate  5  under the heating parts  145  a thermal insulating layer  152  which has a structure identical to that of the thermal insulating layer  21  described above.  
     [0080] The rod-shaped heating parts  145  of the second heating means  139  are radially placed inside the upper mold support plate  57 . It is preferable that, as shown in FIG. 16, six rod-shaped hating parts  145  be radially mounted in an equal interval along the circumferential direction. The thermal insulation tubes  151  covering the cords  149  which are connected to the vacuum terminal part  147  extend upward and the cords  149  upwardly extend through the upper plate  51  (see FIG. 1). Provide on the upper surface of the upper mold support plate  57  is a thermal insulating layer  159  which is formed from a composite composed of fiber glass and heat-resistant resin such as epoxy resin having thermal durability.  
     [0081] The rod-shaped heating parts  145  of the third heating means  141  are positioned in a pair of vertically extending mounting holes formed in both sides of the inner peripheral portion of each holding segment  13 . The upper surface of each holding segment  13  has a groove  155  in communication with each mounting hole  153 , and the vacuum terminal part  147  and thermal insulation tubes  151  covering the cords  149  are placed in the groove  155 . The cords  149  are led outside through cord leading-out parts  157  mounted to the cylindrical member  23 A in a predetermined interval along the circumferential direction.  
     [0082] A fourth heating means  163 , as shown in FIG. 15, is disposed between the lower mold section  7  and the lower mold bead ring  9 . The fourth heating means  163  comprises an electric heater including a heating part which has a flexible pipe and a heating member encased therein, the heating part being deformable. Inside the lower mold section  7  under the fourth heating means  163  there is disposed a thermal insulating layer  165  having the same structure as the above, the thermal insulating layer  165  extending annularly along the lower mold circumferential direction. The fourth heating means  163  enables the bead portion W 2  of the green tire W to be effectively heated under temperature control.  
     [0083] Provided between the cylindrical member  23 A and each of the holding segments  13  is, as shown in FIG. 22, a positioning means  161  for positioning the holding segment  13  in a location in which the guide segment  16  engages with and disengages from the hold segment  13 . The positioning means  161  comprises a spring member  161 A formed from a coil spring, and the spring member  161 A is coupled at its one end to the inner peripheral surface of the cylindrical member  23 A and at the other end to the back surface of the holding segment  13 . Since the spring members  161 A are elongated when the sectors  11   a  are moved forward, the sectors  11   a  are not prevented from moving to the mold clamping position. When the sectors  11   a  reach the mold open position, or the position in which the guide segments  69  engages with and disengage from the holding segments  69 , the spring members  161 A come into non-elongating state and hold the holding segments  13  in that position.  
     [0084] A method of curing the green tire W by means of the tire press mentioned above will be described below. First, when the green tire W is transported to the outer peripheral side of the bladder  29  by a carrier means, not shown, a pressurized fluid is supplied to the bladder  29  via the supply pipe  47 , the passageway  47  and the emission member  43 , whereby the green tire W is held from inside by the bladder  29  which has inflated. After the holding of the green tire W, the first cylinder  35  of the center mechanism  31  is actuated, thereby lowering the rod (elevating post)  35   a  to the curing position (position in FIG. 2).  
     [0085] Next, the upper mold support plate  57  is lowered by the actuation of the elevating cylinders  63  to move the upper mold section  59  and the upper mold bead ring  61  to a starting position for setting shown in FIG. 1. The rod  105   a  of the hydraulic cylinder  105  is then extended to lower the upper plate  51 .  
     [0086] The upper mold section  59  and the upper mold bead ring  61  which are lowered by the lowering of the upper plate  51  come into engagement with and are positioned relative to the other side portion W 4  and the other bead portion W 5  of the green tire W; at the same time, the elevating cylinders  63  are released from activating, whereby the rods  63   a  of the elevating cylinders  63  are retractable.  
     [0087] Meanwhile, the guide segments  69  are lowered with the projections  71   a  of the segment bodies  71  being engaged with the grooves  13   x  of the holding segments  13 . The inner peripheral surfaces  71   b  of the segment bodies  71  push against the bottom surfaces  13   c  of the holding segment depressions  13   b  from the radially outer side, thereby moving the holding segments  13  radially inward along the guide rails  15  to advance the sectors  11   a  toward the mold clamping position. The positioning pins  74  which are lowered are engaged with the positioning parts  27 , whereby the upper plate  51  is positioned relative to the lower plate  5 .  
     [0088] Just before the upper plate  51  reaches the lowermost position, that is, after the lower end of the slide ring member  85 B of the lower ring assembly  85  of the first sealing means  75  has engaged with the annular flange portion  23 B of the cylindrical member  23 A and the lower end of the vertically movable lower ring  97  of the second sealing means  93  has engaged with the upper mold support plate  57 , the vacuum pump  101 A of the suction means  101  is operated to suck air in the chamber  99 . The sucking is performed for a predetermined length of time to make the chamber  99  into a vacuum state.  
     [0089] After the upper plate  51  has reached the lowermost position, that is, the sectors  11   a  have advanced to the mold clamping position, and the sectors  11   a , upper mold section  59  and lower mold section  7  has set up relative to the green tire W, the actuation of the locking means  109  causes the stops  115  to project to engage the stops  115  with the top end faces of the locking shafts  113 . As a result of this, the locking shafts  113  are locked, whereby the upper mold section  59  is clamped to prevent the upper mold section  59  form being opened by an inner pressure applied during vulcanization (see FIG. 2).  
     [0090] A thermal pressurized medium is then supplied into the bladder  29  through the supply pipe  47 , the passageway  45  and the emission member  43 . Also, the first, second, third and fourth heating means heat the green tire W to cure it.  
     [0091] During curing, although the upper mold section  59  and the sectors  11   a  receive pressure in the mold opening directions by the thermal pressurized medium which has supplied to the bladder  29 , the locking means  109  prevent the upper mold section  59  from opening. The sectors  11   a  are prevented from opening since the stop means engaging members  73  engage with the stop means  23 .  
     [0092] After completion of the curing, the locking means  109  are released before the upper plate  51  is raised. The raising of the upper plate  51  raises the guide segments  69  while the sectors  11   a  are retracted toward the mold open position. When the sectors  11   a  reach the mold open position, the guide segments  69  are disengaged from the holding segments  13  and are elevated. Since the spring members  161 A as the positioning means  161  are attached to the holding segments  13 , the holding segments  13  from which the guide segments  69  have disengaged are always maintained in the position of engagement with and disengagement from the guide segments  69 . After vulcanization, the cured tire is removed from the tire press to obtain it.  
     [0093] According to the present invention, since the sectors  11   a  and the holding segments  13  are not attached to the upper plate  51  side, but are mounted to the lower plate  5  side, the weight of the components supported by the upper plate  51  decreases much less than that of the components in the prior art. The upper plate  51  which supports the components can, therefore, be thinner, thereby allowing the upper plate  51  to be reduced in size as well as in weight. Also, the columns  55  slidably supporting the upper plate  51  can be thinner in diameter and the top plate  53  supporting the upper plate  51  via the hydraulic cylinder  105  can be smaller in thickness than before. Further, the hydraulic cylinder  105  can have the capacity much less than the prior art. Accordingly, the tire press can be minimized in size, and the space for installing the tire press can be reduced. Also, electric power consumed by the lifting means  103  for the upper plate  51  is reduced, thereby allowing a decrease in power consumption.  
     [0094] Since the holding segments  13  are always in engagement with the guide rails  15  of the lower plate  5  side and do not have a structure such as the prior art in which the holding segments engage therewith and disengage therefrom, the clearance between the holding segments  13  and the guide rails  15  can be smaller than that of the prior art. Accordingly, movement of the sectors  11   a  due to pressure applied to the sectors  11   a  from the radially inner side can be less than is known in the prior art, thereby allowing tire uniformity to be improved.  
     [0095] Since the electric heaters  143  are employed as means for heating the green tire W in place of conventional steam means, the tire press can be much smaller in size. By disposing the electric heaters  143  of the first, second and third heating means  137 ,  139  and  141  in the above positions, respectively, temperature control during vulcanization can be performed independently, which can effectively heat the green tire W to thereby shorten the curing time.  
     [0096] There is provided between the upper plate  51  and the lower plate  5  the first sealing means  75  which hermetically covers the entire mold during vulcanization, and air in the chamber  99  hermetically covered with the first sealing means  75  is sucked by the suction means  101  to make the chamber vacuum, thereby allowing trapped air between the green tire W and the mold in engagement therewith to be significantly reduced. When air is trapped between the mold and the green tire W, the air causes the tire surface to be rugged after vulcanization, resulting in a poor appearance. As mentioned above, since the trapped air can noticeably be reduced, appearance of the tire obtained after curing can be improved. Also, since the pressure (inner pressure) of a thermal pressurized fluid supplied to the bladder  29  can be lowered, the pressure which is applied to the upper mold section  59  and the sectors  11   a  and which acts as a mold opening pressure is reduced. As a result, since stiffness and strength of the components which hold the upper mold section  59  and the sectors  11   a  in the mold clamping position can be lowered, the cost of the components is reduced, thereby allowing a decrease in tire press cost. Also, a tire quality can be improved because the green tire W pressed by the bladder  29  is restrained from changing the angle of the reinforcement cords of the belt layers and carcass layer thereof, and from causing variations in thickness.  
     [0097] Since the holding segments  13  are provided via the linear bearings  17  on the guide rails  15  in an advancable and retractable manner, the holding segments can smoothly move along the guide rails and the looseness therebetween can be restrained. Accordingly, movement of the sectors  11   a  by the inner pressure during vulcanization can be reduced, thereby improving a tire quality.  
     [0098] The holding segments  13 , which are slidably located on the guide rails  15 , may move due to vibration or the like; by providing the positioning means  161  which position the holding segments  13  in the engagement position with the guide segments  69 , the holding segments  13  can reliably be engaged with the guide segments  69  at all times, preventing a trouble at the clamping of the mold from happening.  
     [0099] The upper mold section  59  and the sectors  11   a  can always be held in the mold clamping position without causing the mold to open during curing, because there are provided the locking means  109  for locking the upper mold section  59  in the mold clamping position during curing and the stop means  23  for stopping the retraction of the holding segments  13 . Thus, the occurrence of rubber overflow of the tire is prevented, and a tire with a good quality can be obtained.  
     [0100]FIG. 23 shows another tire press according to the present invention. This apparatus has guide segments  69  comprising two groups of guide segments  69 A and  69 B in the tire press described above, each group comprising alternate guide segments. One group of guide segments  69 A are fixedly attached to the annular segment attachment member  67  mounted on the lower surface of the upper plate  51 . Each of the other group of guide segments  69 B is attached to a lifting means  171  which is installed on the upper surface of the upper plate  51 . The lifting means  171  includes a hydraulic cylinder  175  fixedly attached to the upper surface of the upper plate  51 . The hydraulic cylinder  175  has a vertically extending rod  175   a , to the lower end of which is secured the segment body  71  of the guide segment  69 B.  
     [0101] According to the above tire press of FIG. 23, the activation of the hydraulic cylinders  175  extend the rods  175   a  to a predetermined length upon the lowering of the upper plate  51  to position the other group of guide segments  69 B lower than the one group of guide segments  69 A.  
     [0102] This causes the other group of guide segments  69 B to engage with the holding segments  13  first and the sectors  11   a  that the holding segments  13  hold to advance first. When these sectors  11   a  come to the mold clamping position, the activation of the hydraulic cylinders  175  is released and the rods  175  are shortened with the lowering of the upper plate  51 . When the upper plate  51  reaches the lowermost position, the sectors  11   a  which are moved forward by the holding segments  13  that the one group of guide segments  69 A have engaged with come to the mold clamping position. The two groups of guide segments  69 A and  69 B, therefore, come into a time lag engagement with the holding segments  13  to thereby do a time lag mold clamping between each adjacent sectors  11   a.    
     [0103] Since this can facilitate escaping air trapped between the green tire W and the sectors  11   a  which have engaged with the green tire W first, the tire appearance can be more improved.  
     [0104] In the embodiment shown in FIG. 23, the same number and even number of guide segments  69 , holding segments  13  and sectors  11   a  are employed, and the number thereof may preferably be, for example, eight, ten or twelve.  
     [0105] In FIG. 23, the locking means  109  and the locking shafts  113  are not shown, but they are placed at locations in which they do not vertically overlap the lifting means  171 .  
     [0106] As mentioned above, according to the present invention, since the sectors and the holding segments are mounted to the lower plate side, the weight of the components supported by the upper plate is reduced much less than that of the components in the prior art. As a result, the upper plate which supports the components can be reduced in size as well as in weight less than before. Associated components which liftably support the upper plate can also be reduced in size and in weight, and further, lifting means lifting the upper plate can be smaller in size. Accordingly, the tire press can be small-sized, and the installation space therefor can be reduced. Also, since the electric power consumed by the means for lifting the upper plate is reduced, power consumption can be lowered.  
     [0107] Since the holding segments are always in engagement with the lower plate side and do not have a conventional structure in which the holding segments engage therewith and disengage therefrom, the clearance between engagement parts can be smaller than that of the prior art. As a result, movement of the sectors is less than before at the mold clamping position when pressure is applied thereto from the radially inner side thereof during vulcanization, thereby allowing tire uniformity to be improved.  
     INDUSTRIAL APPLICABILITY  
     [0108] The present invention having the aforementioned excellent effects can be used very effectively as a tire curing method and tire press for producing pneumatic tires for passenger cars, trucks, buses and the like.