Abstract:
An endless dough conveyor  16  is provided with a resin endless toothed belt  18  instead of a metal chain. A toothed pulley  22  around which the endless toothed belt is wound is also made of resin. A rail  64  is disposed adjacent to a horizontal path of the belt, and a roller  46  attached to the belt is adapted to roll on the rail. At least two induction motors are provided for driving the endless toothed belt. The induction motors are supplied with electric power from a single inverter  35.  At least a pulley is provided with a detecting unit  80.  The detecting unit  80  detects a state in which teeth of the endless toothed belt climb onto that of the pulley, thereby predicting breakage of the belt. Thus, it is possible to prevent contamination of dough in a proofer.

Description:
This application claims priority under 35 U.S.C. §119 to Japanese Patent application No. JP2007-039989 filed Feb. 20, 2007, the entire content of which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a proofer (a fermentation apparatus) used in a bread making process. 
   2. Description of the Related Art 
   In a bread making process, bread dough undergoes a series of dough forming processes such as dividing, rounding, fermentation, deflating, and panning, and then is baked. In order to promote fermentation and stabilize dough structure, divided and rounded dough pieces are placed on a conveyor and conveyed for a predetermined period of time in a proofer chamber in which temperature is kept constant. 
   A dough conveyor disposed in the proofer generally has a pair of metal endless chains spaced from and parallel to each other, and a plurality of dough holding members disposed between the pair of metal endless chains. The dough holding members are each provided with a basket on which dough is placed. 
   In such a conventional proofer, a metal chain is wound around and driven by a metal sprocket. Therefore, metal powders generated by the friction between the chain and the sprocket may be mixed into bread dough. Moreover, since the metal chain is lubricated, the lubricant may drip off, and powders floating in the proofer adhere to the metal chain and the metal sprocket. Then, the mixture of wear powders, lubricant, and bread dough flour may be separated from the chain and the sprocket and mixed into the bread dough. 
   It is an object of the present invention to solve the above problems in such a conventional proofer. 
   SUMMARY OF THE INVENTION 
   The present invention provides a proofer including a proofer chamber, and an endless dough conveyor at least a part of which is disposed in the proofer chamber. The endless dough conveyor includes a pair of resin endless toothed belts spaced a predetermined distance from each other in the horizontal direction, a resin toothed pulleys around which the resin endless toothed belts are engaged, a dough holding members disposed between and successively arranged along the pair of endless toothed belts so as to extend in a direction perpendicular to the direction in which dough is conveyed, a connecting members attached to the endless toothed belts for detachably connecting opposite ends of the respective each end of the dough holding members detachably to the endless toothed belt, resin rollers rotatably attached to the connecting members, and a pair of rails disposed along horizontal moving paths of the rollers which extend between the opposite ends of the dough holding members and the pair of resin endless toothed belts, respectively, for supporting the rollers moving along the horizontal moving paths. 
   In this proofer, the endless toothed belt and the toothed pulley are made of resin. Therefore, in contrast to a conventional proofer using a chain, metal powders are not generated or lubricant does not drip from the toothed belt and the toothed pulley, whereby it is possible to substantially reduce the possibility of contamination of bread dough. 
   Specifically, the connecting member is a metal shaft secured to the endless toothed belt and extending inwardly in a widthwise direction of the endless dough conveyor. The metal shaft has a connection hole extending outwardly in the widthwise direction from the inner end of the shaft. The roller is rotatably attached to the shaft to rotate about an axis of the shaft. The dough holding member has at each end thereof a connecting pin which is displaceable in the connection hole in the widthwise direction of the endless dough conveyor. The connecting pin is pushed outwardly in the widthwise direction to be inserted into the connection hole, whereby the dough holding member is connected to the connecting member. 
   More specifically, the rail may include a metal rail body and a roller engaging member made of resin and attached to the rail body so as to support the roller. 
   The roller may have at opposite ends thereof a flange each having an inclined surface. The inclined surfaces of the flanges extends in a diverging fashion from a surface of the roller. The roller engaging member of the rail may be configured to be engaged with the inclined surfaces of the flanges at a position away from the surface of the roller. 
   With this arrangement, the roller surely engages with the rail, whereby it is possible to stably move the endless toothed belt. 
   Further, the proofer may also include an assist rail which is disposed on the outer side of the rail and extends along the rail. The assist rail engages with and supports the endless toothed belt positioned on the outer side of the rail when the endless toothed belt is engaged with the toothed pulley in a state in which the dough holding member has not been connected to the connecting member. 
   When the endless dough conveyor is installed in the proofer, the left and right endless toothed belts are each wound around the corresponding toothed pulleys, and then the dough holding member is connected to the both endless toothed belts. In this state, it is possible to stably handle the endless toothed belts by means of the assist rails. 
   More specifically, the proofer may also include a frame disposed on both sides of the endless dough conveyor and having a cantilever shaft extending from the frame toward the endless dough conveyor. The toothed pulley is rotatably held by the cantilever shaft. 
   With this arrangement, if the dough holding members are removed from the endless toothed belts, there is no obstruction between the endless toothed belts, whereby a worker can enter the proofer to carry out cleaning and the like. 
   More specifically, the toothed pulleys are arranged to make a plurality of pairs of the toothed pulleys which are oppositely disposed on left and right sides of the endless dough conveyor and at least two pairs thereamong areare for driving. Each pair of the at least two pairs of the toothed pulleys is drivingly connected to an induction motor. The induction motors are supplied with driving electric power from a single inverter. 
   In this case, for example, the two induction motors, which are separately disposed, operate synchronously with each other, thereby sharing the load of driving the endless dough conveyor. Therefore, in comparison with a case in which a single motor is used, a driving force for each endless toothed belt (i.e., a tension of each endless toothed belt) can be half or less. With a plurality of motors, the total motor capacity for the endless dough conveyor can be large, while the tension acting on each belt can be smaller than an allowable tension of each belt. Therefore, although the allowable tension of each belt is smaller than that of each chain, it is possible to provide an equal conveying power which compares with that of the endless chain conveyor. 
   Further, the proofer may also de configured as follows. The toothed pulleys are arranged to make a plurality of pairs of the toothed pulleys which are oppositely disposed on left and right sides of the endless dough conveyor and at least one pair thereamong among the pairs of toothed pulleys disposed on the left and right sides of the endless dough conveyor so as to oppose to each other, at least a pair of toothed pulleys is a pair of take-up pulleys being displaceable according to the tension of the endless toothed belts. The proofer further includes an abnormal tension detecting sensor for detecting and indicating occurrence of abnormal tension on the endless toothed belts when the displacement of the at least one pair of the toothed pulleys is larger than a predetermined value. 
   Furthermore, the proofer may further include a detecting switch for detecting a risk of breakage of the endless toothed belt. If teeth of the endless toothed belt disengage with and climb onto that of the toothed pulley, the detecting switch detects this displacement of the endless toothed belt and indicates a risk of breakage of the endless toothed belt. 
   In comparison with the chain, the endless toothed belt has the above-described advantages. However, in a case where the endless toothed belt has broken at the end of its useful life, it takes time to replace the broken belt. Therefore, it is substantially important to predict such breakage of the endless toothed belt. Before the endless toothed belt breaks at the end of its useful life, the endless toothed belt is plastically stretched at a certain portion which will be broken, and then the distance between adjacent teeth at the certain portion becomes larger. In this plastically stretched portion, teeth of the endless toothed belt disengage with and climb onto that of the toothed pulley. The above detecting switch detects this displacement of the endless toothed belt, thereby predicting breakage of the endless toothed belt. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing an inner structure of a proofer according to an embodiment of the present invention, as viewed from the front of the proofer. 
       FIG. 2  is a simplified perspective view of an endless dough conveyor in the proofer in  FIG. 1 . 
       FIG. 3  is a perspective view of one end portion of the endless dough conveyor in the proofer in  FIG. 1 . 
       FIG. 4  is a view of the one end portion as viewed in the conveying direction of the endless dough conveyor. 
       FIG. 5  is a top view of the one end portion. 
       FIG. 6  is a diagram showing the relationship between an endless toothed belt and a connecting member at the one end portion. 
       FIG. 7  is a diagram showing the relationship between a take-up pulley of the endless dough conveyor and a proximity switch which is disposed adjacent to the take-up pulley to detect abnormality of the endless toothed belt. 
       FIG. 8  is a view showing another detecting unit for detecting the abnormality of the endless toothed belt. 
       FIG. 9  is a view showing still another detecting unit for detecting the abnormality of the endless toothed belt. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of a proofer according to the present invention will now be described with reference to the accompanying drawings. 
   As in conventional proofers, a proofer  10  according to an embodiment of the present invention includes a housing  14  having a proofer chamber  12 , and an endless dough conveyor  16  for receiving dough and conveying the dough in the chamber  12 , as shown in  FIG. 1 , as a basic structure. 
   As shown in  FIG. 2 , the endless dough conveyor  16  has a pair of endless toothed belts  18  spaced a predetermined distance from and parallel to each other in the horizontal direction, a plurality of toothed pulleys  22  around which the endless toothed belts are wound, and a plurality of dough holding members  24  extending in a direction perpendicular to the direction in which dough is conveyed by the endless dough conveyor and supportably connected at both ends thereof to the endless toothed belts  18 . 
   The endless toothed belts  18  and the toothed pulleys  22  are made of resin. The endless toothed belts are preferably made of urethane resin and provided inside thereof with a steel core wire extending in the longitudinal direction thereof. The toothed pulleys are preferably made of resin different from that used for the endless toothed belts. For example, nylon resin is suitable for the toothed pulleys. These kinds of resin are preferably anti-statically treated. 
   As shown in  FIG. 1 , the housing  14  has a base portion  14 - 1  disposed on a floor F, and a proofer portion  14 - 2  defining a proofer chamber  12 . The endless dough conveyor  16  extends upwardly in the base portion  14 - 1  and horizontally in plural layers (six layers in the illustrated example) in the vertical direction. The endless dough conveyor  16  receives dough supplied through a chute  23  at the bottom portion of the base portion  14 - 1 , conveys the dough upwardly and into the proofer chamber  12 , and then discharges the dough to a discharge chute  25 . As shown in  FIGS. 1 and 2 , in the endless dough conveyor  16 , two pairs of toothed pulleys  22  positioned at the upper and lower portions at the left end (as viewed in the figure) of the horizontally extending portion of the endless dough conveyor are each drivingly connected to an output shaft of a respective induction motor  34  by means of drive belts  32  provided for each toothed pulley. Each of the induction motors  34  is supplied with and driven by an identical voltage at an identical frequency from an inverter  35 . Even if loads on the induction motors are different from each other, the induction motors eliminate the difference to operate synchronously with each other. 
     FIGS. 3 to 5  show the relationship among the housing  14 , the endless toothed belt  18 , and the dough holding member  24 , at one end portion in the transverse direction of the horizontally extending portion of the endless dough conveyor  16 .  FIG. 6  shows the relationship between the endless toothed belt  18  and a connecting member  54  for connecting the dough holding member  24  to the endless toothed belt  18 . 
   As shown in  FIGS. 3 and 5 , the dough holding member  24  has a frame  38  having a rectangular shape in a plan view, and the frame  38  is provided with a plurality of dough trays (baskets)  26 . 
   The endless toothed belt  18  is provided with a through hole  42  extending across the endless toothed belt so as to correspond to each dough holding member  24  (see  FIGS. 6 and 5 ). A shaft  44  having a roller  46  rotatably attached thereto is inserted into and secured to the through hole. Specifically, the shaft  44  has a small-diameter portion  47  which is inserted into the through hole  42 , and a large-diameter portion  48  which rotatably holds the roller  46 . A nut  50  is screwed onto the distal end of the small-diameter portion  47  projecting outwardly from the through hole  42 , whereby the shaft  44  is secured to the endless toothed belt  18 . The shaft  44  is provided with a support hole  52  extending from the right end thereof to the left coaxially with the shaft. 
   Between the shaft  44  and the frame  38  of the dough holding member, a connecting member  54  is provided for connecting the shaft and the frame. As shown in  FIGS. 3 to 5 , the connecting member  54  has a trapezoidal-shaped portion  56  (see  FIG. 3 ) secured to a side end surface of the frame  38 , a tubular portion  58  extending from the upper central portion of the trapezoidal-shaped portion  56  toward the endless toothed belt  18 , and a connecting pin  60  slidably disposed in the tubular portion  58 . The left end portion of the connecting pin  60  is inserted into the support hole  52  of the shaft  44 , whereby the frame  38  of the dough holding member is pivotally attached to the shaft  44  (i.e., to the endless toothed belt). 
   In  FIG. 4 , reference numeral  62  denotes a frame forming the housing  14 . The frame  62  is provided with a rail  64  disposed along a moving path of the roller  46  and attached to the frame  62  by means of the support bar  65 . The rail  64  has a metal rail body  66 , and a resin roller engaging portion  68  extending along and covering the upper end portion of the rail body  66 . The roller  46  has at both ends thereof flanges  70 ,  70 , each of which has an inclined surface extending mutually away from the surface of the roller  46 . The roller engaging portion  68  has at both ends thereof inclined surfaces which engage with the inclined surfaces of the flanges, and a central surface parallel to the surface of the roller  46 . Preferably, the central surface of the roller engaging portion  68  is adapted not to contact with the surface of the roller  46 . 
   An assist rail  72  is disposed below the endless toothed belt  18  so as to extend along the endless toothed belt  18  by means of the support bar  65 . In assembling the endless dough conveyor  16  in the proofer, the endless toothed belt  18  engages with and is supported by the assist rail  72  when the endless toothed belt  18  is wound around the toothed pulley  22  in a state in which the dough holding member  24  has not been connected to the endless toothed belt  18 . Then, when the dough holding member  24  is connected to the endless toothed belt  18 , the endless toothed belt  18  is moved upwardly from the assist rail  72 . In  FIG. 4 , reference numeral  74  denotes a foreign matter tray. 
   In the toothed pulleys shown in  FIG. 1 , toothed pulleys  22 - 1  are take-up pulleys which are displaceable according to the tension of the endless toothed belt  18  wound around the take-up pulleys  22 - 1 . Specifically, as shown in  FIG. 7 , the take-up pulley  22 - 1  is slidably attached to the housing  14  by means of a toothed pulley holding member  76 , and is biased by a tension spring  78  in a direction in which the endless toothed belt  18  is applied to the tension (i.e., in the leftward direction in  FIG. 7 ). The take-up pulley  22 - 1  is adapted to be displaced rightward when the tension of the endless toothed belt becomes larger. Reference numeral  80  denotes a proximity switch attached to the housing  14 . If the holding member  76  of the take-up pulley is displaced rightward by excessive tension of the endless toothed belt  18 , the proximity switch detects this displacement of the holding member  76  and generates a command signal necessary for stopping a motor and the like. 
     FIG. 8  shows an abnormality detecting unit  82  for the drive toothed pulley  22 . The abnormality detecting unit  82  has a roller  84  which rotatably engages with the outer surface of the endless toothed belt  18  wound around the drive toothed pulley  22 . In a case where the endless toothed belt disengages with the drive toothed pulley  22  and then teeth of the endless toothed belt climb onto that of the drive pulley, the abnormality detecting unit detects the displacement of the endless toothed belt and indicates occurrence of abnormality. For example, such abnormality occurs when the endless toothed belt  18  reaches the end of its useful life. Before the endless toothed belt  18  breaks at the end of its useful life, the endless toothed belt is plastically stretched at a certain portion which will be broken. In this state, the distance between adjacent teeth of the endless toothed belt at the certain portion becomes larger. Thus, teeth of the endless toothed belt disengages with that of the toothed pulley  22 , which causes the teeth of the endless toothed belt to climb onto that of the drive pulley. Therefore, by detecting the above stated abnormality, it is possible to predict that the endless toothed belt is reaching the end of its useful life. 
   Alternatively, it is also possible to predict the end of useful life of the endless toothed belt by means of another detecting unit shown in  FIG. 9 . The housing  14  (i.e., the frame defining the housing) is provided with a lever  86  pivotally attached thereto. The lever  86  is provided at one end thereof with a detecting toothed roller  88  which engages with the endless toothed belt  18 , and a proximity switch  90  is disposed adjacent to the other end of the lever  86 . When the endless toothed belt  18  reaches the end of its useful life and is then plastically stretched, teeth of the detecting roller  88  disengage with that of the endless toothed belt  18 , which causes the detecting roller  88  to be moved upwardly. Then, the proximity switch  90  detects this displacement. 
   It should be noted that the present invention is not necessarily limited to the foregoing embodiment but can be modified in a variety of ways without departing from the gist of the present invention.