Patent Publication Number: US-8989565-B2

Title: Multistage furnace

Description:
CROSS-REFERENCE OF THE INVENTION 
     This application claims priority from Japanese Patent Application Nos. 2012-224148 and 2012-224149, the contents of which are incorporated herein by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a multistage furnace in which a plurality of furnace units are piled up in the vertical direction. 
     2. Description of the Related Art 
     For vehicle components, a thinned and high-strength member is used so as to enhance both the safety and economy. For this purpose, so-called hot press is known in which a steel plate heated to high temperature is quenched by cooling the plate with low-temperature press dies. In this method, a steel plate is heated to transformation temperature or higher at which the metal structure of the steel member is transformed into austenite, and the steel plate is formed and rapidly cooled with press dies simultaneously, completing quenching. 
     As a furnace for hot press, as shown in  FIG. 11 , one is known in which a multiple number of lower heaters  1  and upper heaters  2  are arrayed in the horizontal direction and a steel plate W is carried and heated between the lower heaters  1  and the upper heaters  2  from the inlet to the outlet. Steel plates W are sequentially inserted into the furnace from the inlet thereof, and heated between the lower heaters  1  and the upper heaters  2  until these are discharged from the outlet. A relevant technique is disclosed in Japanese Patent Application Publication No. 2010-44875. 
     The conventional furnace heats a plurality of steel plates W sequentially, but the multiple number of lower heaters  1  and upper heaters  2  arrayed in the horizontal direction make the installation area of the furnace large in a factory. Furthermore, even when only one of the multiple number of lower heaters  1  and upper heaters  2  is broken due to burnout or the like, all the steel plates W inserted in the furnace become defective products due to underheating. 
     SUMMARY OF THE INVENTION 
     To solve the described problem, the invention provides a multistage furnace including a plurality of furnace units piled up in a vertical direction, the furnace units each including: upper and lower heaters having plate shapes layered in the vertical direction; a first support pipe disposed on one end of the upper heater and extending in a horizontal direction; a second support pipe disposed on other end of the upper heater and extending in the horizontal direction; and a plurality of work support bars disposed over the first and second support pipes so as to support a work, wherein a back surface of a work supported by the plurality of work support bars is opposed to the upper heater and a front surface of the work is opposed to a lower heater of an adjacent furnace unit disposed above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing all installations for hot press. 
         FIG. 2  is a front view of a multistage furnace in an embodiment of the invention. 
         FIG. 3  is a plan view of one of the furnace units of the multistage furnace in  FIG. 2 . 
         FIG. 4  is a left side view of  FIG. 3 . 
         FIG. 5  is a plan view of a work carrier machine. 
         FIG. 6  is a first plan view showing a state of carrying works by the work carrier machine. 
         FIG. 7  is a second plan view showing a state of carrying works by the work carrier machine. 
         FIG. 8  is a third plan view showing a state of carrying works by the work carrier machine. 
         FIGS. 9A ,  9 B and  9 C are side views showing a state of carrying a work by the work carrier machine. 
         FIGS. 10A and 10B  are cross-sectional views of a support pipe and a work carrier bar. 
         FIG. 11  is a view showing a conventional furnace. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a view showing all installations for hot press. As shown in  FIG. 1 , a multistage furnace  100 , two work carrier machines  200 A and  200 B, and a press machine  300  having press dies are disposed. The work carrier machine  200 A is disposed on the inlet side of the multistage furnace  100  so as to insert works such as a steel plate into the multistage furnace  100 , and the work carrier machine  200 B is disposed on the outlet side of the multistage furnace  100  so as to discharge works from the multistage furnace  100 . 
     The multistage furnace  100  is configured by piling a plurality of furnace units in the vertical direction. In this example, ten furnace units  100 - 1  to  100 - 10  are piled up. 
     The work carrier machine  200 A for insertion and the work carrier machine  200 B for discharge have the same structures basically, each of which has a plurality of work carrier bars  201 , a horizontal motion mechanism  205  connecting the ends of the plurality of work carrier bars  201  and moving these on horizontal rails  204 , and a vertical motion mechanism  207  moving the horizontal rails  204  on vertical rails  206 . A controller  208  such as CPU that controls the operations of the horizontal motion mechanism  205 , the vertical motion mechanism  207  and so on is further provided. 
     This enables a work to move in the horizontal and vertical directions, being supported on the plurality of work carrier bars  201 , and the work is inserted in any one furnace unit  100 -X of the multistage furnace  100  together with the plurality of work carrier bars  201  of the work carrier machine  200 A for insertion. The work inserted in the furnace unit  100 -X is heated to an austenitizing temperature or higher. 
     When the heating of the work is completed, the plurality of work carrier bars  201  of the work carrier machine  200 B for discharge are inserted in the furnace unit  100 -X of the multistage furnace  100  and the work is discharged from the multistage furnace  100 , being supported on the plurality of work carrier bars  201 . Then, the work discharged from the multistage furnace  100  is formed and cooled rapidly by the press dies of the press machine  300 , thereby completing quenching. 
     Hereafter, the structures of the multistage furnace  100 , and the work carrier machines  200 A and  200 B will be described. 
     &lt;Structure of Multistage Furnace  100 &gt; 
       FIG. 2  is a front view of the multistage furnace  100 ,  FIG. 3  is a plan view of one furnace unit of the multistage furnace of  FIG. 2 , and  FIG. 4  is a left side view of  FIG. 3 . In  FIG. 2 , only four furnace units  100 - 1  to  100 - 4  are shown. 
     The furnace units  100 - 1  to  100 - 10  have the same structures basically. Two plate-shaped lower heaters  101 A and  101 B are provided adjoining in the horizontal direction on the bottom portion of the furnace unit  100 - 1 . Upper heaters  102 A and  102 B are layered on the lower heaters  101 A and  101 B respectively so that the upper heaters  102 A and  102 B and the lower heaters  101 A and  101 B are opposed to each other, holding heat insulators  103 A and  103 B therebetween. A pair of electrodes  109 A and  109 B for power supply are provided on each of the lower heaters  101 A and  101 B, and a pair of electrodes  110 A and  110 B for power supply are provided on each of the upper heaters  102 A and  102 B. It is preferable that the lower heaters  101 A and  101 B and the upper heaters  102 A and  102 B are far-infrared heaters that emit far-infrared radiation. 
     A support pipe  104 A is provided near the inlet of the furnace unit  100 - 1  on the left side in  FIG. 2 , extending on one end portion of the upper heater  102 A in a horizontal direction (Y direction). A support pipe  104 B is provided near the center of the furnace unit  100 - 1 , extending on end portions of the upper heaters  102 A and  102 B in the horizontal direction (Y direction). Furthermore, a support pipe  104 C is provided near the outlet of the furnace unit  100 - 1  on the right side in  FIG. 2 , extending on one end portion of the upper heater  102 B in the horizontal direction (Y direction). The support pipes  104 A,  104 B and  104 C are made of metal and have cylindrical shapes. 
     The support pipe  104 A is inserted in a plurality of bases  105 A (e.g. five bases) provided at predetermined intervals. The support pipes  104 B and  104 C are also inserted in the bases  105 B and  105 C in the similar manner, respectively. 
     Support stands  111 A,  111 B and  111 C are provided standing on the bases  105 A,  105 B and  105 C, respectively. A concave portion having a semicircle cross section is formed in the upper surfaces of the support stands  111 A,  111 B and  111 C. A plurality of work support bars  106  (e.g., five bars) are mounted over the three support pipes  104 A to  104 C, extending in a horizontal direction (X direction). In this case, the work support bars  106  are metallic columns or cylinders, and fitted in the concave portions of the support stands  111 A,  111 B and  111 C. 
     Two works W 1  and W 2  inserted from the inlet by the work carrier machine  200 A are supported on these work support bars  106 . Each of the works W 1  and W 2  is a vehicle component, for example, and made of a steel plate having a predetermined shape. Furthermore, an inlet door  107  and an outlet door  108  that are openable and closable are provided on the inlet and outlet of the furnace unit  100 - 1 , respectively. 
     The furnace unit  100 - 1  is stored in a housing, and the furnace unit  100 - 2  having the same structure is mounted thereon. Furthermore, the furnace units  100 - 3  to  100 - 10  are sequentially piled up thereon. 
     In this case, the back surface of the work W 1  inserted in the furnace unit  100 - 1  is opposed to the upper heater  102 A, and the front surface of the work W 1  is opposed to the lower heater  101 A of the adjacent furnace unit  100 - 2  on the second stage disposed above. Furthermore, the back surface of the work W 2  inserted in the furnace unit  100 - 1  is opposed to the upper heater  102 B, and the front surface of the work W 2  is opposed to the lower heater  101 B of the adjacent furnace unit  100 - 2  on the second stage disposed above. 
     As described above, since the multistage furnace  100  is configured by piling up the furnace units  100 - 1  to  100 - 10  in the vertical direction, the installation area is decreased to save the space in a factory. Furthermore, since each of the furnace units functions as an independent furnace, even when one furnace unit is broken, the other furnace units are not influenced by it. The number of the furnace units may be increased or decreased according to need depending on a required number of products. 
     The multistage furnace  100  has such a structure that the lower heaters  101 A and  101 B and the upper heaters  102 A and  102 B are layered on each of the bottom portions of the furnace units  100 - 1  to  100 - 10  and hold the heat insulators  103 A and  103 B therebetween respectively, and the work support bars  106  are mounted over the upper heaters  102 A and  102 B. Therefore, the sizes of the furnace units  100 - 1  to  100 - 10  are decreased in the vertical direction to make the multistage furnace  100  compact as a whole. 
     In each of the furnace units  100 - 1  to  100 - 10 , the two lower heaters  101 A and  101 B and the two upper heaters  102 A and  102 B are provided so as to insert two works W 1  and W 2  respectively and correspondingly. However, the number of the heaters may be increased or decreased depending on the number of works to be inserted, and the number of the support pipes and the number of the work support bars may be increased or decreased correspondingly. 
     Since the lower heaters  101 A and  101 B of the furnace unit  100 - 1  on the lowest stage and the upper heaters  102 A and  102 B of the furnace unit  100 - 10  on the highest stage have no work to heat, these may be replaced by unused dummy heaters or removed so as to save the electric power. 
     Furthermore, since the loads of the works W 1  and W 2  and the work support bars  106  are applied to the support pipes  104 A,  104 B and  104 C, the support pipes  104 A,  104 B and  104 C are easy to deform by the heating of the furnace units  100 - 1  to  100 - 10 . If the heat deformations of the support pipes  104 A,  104 B and  104 C occur, the works W 1  and W 2  may shift out of position or fall. Therefore, by flowing cooling water through the support pipes  104 A,  104 B and  104 C, the heat deformations are prevented. 
       FIGS. 10A and 10B  are cross-sectional views showing the structure of the support pipes  104 A,  104 B and  104 C, and  FIG. 10B  is a cross-sectional view of  FIG. 10A  along line X-X. As shown in  FIGS. 10A and 10B , each of the support pipes  104 A to  104 C includes an outer pipe  112  of which one end is closed by a stopper  114  and the other end is open, and an inner pipe  113  inserted in the outer pipe  112  with a space therebetween, of which both the ends are open. Cooling water is injected into the inner pipe  113  from the opening of the inner pipe  113  by cooling water injecting device such as a water tap. The cooling water injected into the inner pipe  113  hits the stopper  114 , flows back in the reverse direction through the space, and is collected. This structure doubles the path of cooling water to provide a high cooling effect and save the piping of cooling water. 
     &lt;Structure of Work Carrier Machines  200 A and  200 B&gt; 
     As described above, the work carrier machine  200 A is used for inserting works W 1  and W 2  into the multistage furnace  100  and the work carrier machine  200 B is used for discharging the works W 1  and W 2  from the multistage furnace  100 , and both the machines have the same structures. 
       FIG. 1  is a front view of the work carrier machine  200 A, and  FIG. 5  is a plan view of the work carrier machine  200 A, and  FIGS. 6 to 8  are plan views showing a state of carrying works by the work carrier machine  200 A.  FIGS. 9A ,  9 B and  9 C are side views showing a state of carrying a work by the work carrier machine  200 A. 
     The work carrier machine  200 A includes a plurality of work carrier bars  201  (e.g., 6 bars) extending in the horizontal direction, the horizontal motion mechanism  205  connecting the ends of these work carrier bars  201  and moving these on the horizontal rails  204 , and the vertical motion mechanism  207  (ref.  FIG. 1 ) moving the body of the work carrier machine including the horizontal rails  204  on the vertical rails  206 . 
     The horizontal motion mechanism  205  and the vertical motion mechanism  207  include wheels running on the horizontal rails  204  and the vertical rails  206  respectively, and motors driving and rotating the wheels. 
     The works W 1  and W 2  are supported on predetermined positions of the six work carrier bars  201 , but only by this support, the works W 1  and W 2  may shift out of position or fall while the work carrier bars  201  are moving. To prevent this, a pair of guide bars  202  are mounted on each of the work carrier bars  201 , parallel with each other. The pair of guide bars  202  are parallel to the corresponding work carrier bars  201 . 
     A pair of work restriction components  203 A and  203 B formed in a ring shape is attached to each of the guide bars  202 , and the work restriction components  203 A and  203 B are positioned corresponding to the planar shape of the works W 1  and W 2  and hold each of the works W 1  and W 2  from both the sides to restrict the motions. 
     The operation of the work carrier machine  200 A will be described referring to  FIGS. 6 to 9C . The operations of the horizontal motion mechanism  205  and the vertical motion mechanism  207  are controlled by the controller  208 . First, as shown in  FIG. 6 , works W 1  and W 2  are mounted on the work carrier bars  201  and the motions of the works W 1  and W 2  are restricted by the work restriction components  203 A and  203 B. Then, by the vertical motion mechanism  207 , the body of the work carrier machine is moved in the vertical direction to the height of one furnace unit to insert the works W 1  and W 2 . 
     Then, as shown in  FIG. 7  and  FIG. 9A , the six work carrier bars  201  are horizontally moved in the X direction by the horizontal motion mechanism  205  so as to be inserted between the five work support bars  106  of the furnace unit. 
     Then, as shown in  FIG. 9B , by moving the six work carrier bars  201  downward by the vertical motion mechanism  207 , the works W 1  and W 2  mounted on the work carrier bars  201  are transferred onto the work support bars  106 . Then, as shown in  FIG. 9C , the work carrier bars  201  are further moved downward by the vertical motion mechanism  207 , and the work carrier bars  201  are moved away from the works W 1  and W 2  into spaces surrounded by the works W 1  and W 2  and the support stands  111 A,  111 B and  111 C. Then, as shown in  FIG. 8 , the work carrier bars  201  are pulled out from the furnace unit by the horizontal motion mechanism  205 . 
     In this manner, the works W 1  and W 2  are inserted into any one of the furnace units of the multistage furnace  100  by using the work carrier bars  201 . As described above, the furnace unit has such a structure that the size in the vertical direction is small, and the works W 1  and W 2  are stored in a narrow space between the work support bars  106  and the lower heaters  101 A and  101 B disposed above. The work carrier machine  200 A is suitable for inserting the works W 1  and W 2  into such a narrow space by using the work carrier bars  201 . 
     The work carrier machine  200 B also uses the work carrier bars  201  in the similar manner so as to discharge the works W 1  and W 2  from any one of the furnace units of the multistage furnace  100 . 
     Furthermore, since the work carrier bars  201  are inserted into the high-temperature furnace unit, the work carrier bars  201  are easy to deform by heat. If the heat deformations of the work carrier bars  201  occur, the works W 1  and W 2  may shift out of position or fall. In the similar manner to the support pipes  104 A,  104 B and  104 C described above, the heat deformations of the work carrier bars  201  are prevented by flowing cooling water therethrough. 
     In this case, too, as shown in  FIG. 10 , the work carrier bar  201  includes an outer pipe  112  of which one end is closed by a stopper  114  and the other end is open, and an inner pipe  113  inserted in the outer pipe  112  with a space therebetween, of which both the ends are open. Cooling water is injected into the inner pipe  113  from the opening of the inner pipe  113  by cooling water injecting device such as a water tap. The cooling water injected into the inner pipe  113  hits the stopper  114 , flows back in the reverse direction through the space, and is collected. This structure doubles the path of cooling water to provide a high cooling effect and save the piping of cooling water. 
     It is noted that the number of the work carrier bars  201  is determined depending on the number of the work support bars  106  of the furnace unit, and it is preferable that the number of the work carrier bars  201  is more than the number of the work support bars  106  by one bar. 
     As described above, a multistage furnace in which a plurality of furnace units are piled up in the vertical direction, and thus the installation area of the furnace is decreased. Since each of the furnace units functions as an independent furnace, even when one furnace unit is broken, the other furnace units are not influenced by it. Furthermore, the size of one furnace unit in the vertical direction is decreased, and thus the whole size of the furnace in the vertical direction is decreased. Also, the support pipe is configured so as to flow cooling water therethrough, thereby preventing the heat deformation.