Abstract:
The invention provides an apparatus and method for improved mixing of yeast-raised and yeast-raised type dough. The device and method keep the dough cool by an improved structure and method for circulating coolant around a jacketed bowl, and by circulating cooled air through the spinning agitator roller bars. Better aeration of the dough and faster mixing time are achieved along with full water and flour absorption, and reduced operating temperatures by controlling placing of the agitator driveshaft in a carefully defined region. Finally, the invention provides a wiper for wiping the lip of the bowl to keep it clean of dough and to insure a proper seal along the bowl lip when a resilient, expandable bowl seal is used, and it provides a pneumatic seal for securely sealing the mix ingredients in the bowl during mixing.

Description:
FIELD OF THE INVENTION 
     This invention pertains to yeast-raised and yeast-raised-type dough-mixing machines and to methods of yeast-raised and yeast-raised-type dough mixing. 
     BACKGROUND OF THE INVENTION 
     Conventional methods and devices for mixing yeast-raised dough have a number of shortcomings, such as relatively long mix times which result in undesirable higher output temperatures, less than optimal gluten development, and high operating costs. In addition, these conventional methods and devices do not produce uniform aeration of the dough. When conventional devices are run at higher operating speeds to decrease mix time, they produce even poorer aeration of the dough, along with tearing of the dough and even higher dough temperatures. 
     A need exists, therefore, for improved methods and apparatus for mixing dough that will reduce mixing time, decrease the dough temperature and better aerate the dough. This invention relates to an apparatus and method for achieving optimal gluten development of yeast-raised and yeast-raised-type dough by reducing the mixing time while achieving lower dough temperatures and better aeration of the dough. The benefits of this invention may be achieved with different yeast-raised dough types having different air and water absorption levels and different flour protein levels. Furthermore, because this invention reduces the dough mixing time, it decreases the operating costs per pound of product. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention is generally directed to providing improved efficiency and effectiveness in mixing of yeast-raised dough. The apparatus and method of the invention achieve a cooling effect on the dough by way of an improved jacketed bowl structure and method for circulating cooled air around a jacketed bowl. The jacketed bowl has a generally v-shaped channel adjacent to the exterior surface of the bowl to distribute coolant around the exterior surface of the bowl. 
     The apparatus and method achieve further improved cooling through an improvement made to the agitator that mixes dough in the bowl. While mixing, the agitator rotates around its driveshaft. The agitator&#39;s stretcher bars rotate around the agitator driveshaft, and spin in their mountings on the agitator. In the past, it has not been possible to circulate cool air through spinning stretcher bars while the agitator rotates. This invention achieves further improved cooling of dough during mixing by circulating cooled air through the spinning roller bars of the rotating agitator. 
     In one important embodiment, the present invention achieves better aeration of the dough and faster mixing times at lower operating temperatures while still allowing for full water and flour absorption by positioning the agitator driveshaft in a defined region vis á vis the interior surface of the bowl to ensure a gentle folding and rolling of the dough during mixing. This produces more uniform aeration and less heat than experienced in prior art dough mixing machines. 
     In another important embodiment of the invention, the distance the roller bars are placed away from the stretcher bars further optimizes the aeration of the dough thereby reducing mixing time and heat build-up. 
     It is desirable to maintain a good seal between the cover and the top of the bowl during mixing. This has not been successfully done in the past. Thus, in yet another embodiment of the invention a wiper is provided for wiping the lip of the bowl to insure secure sealing of the ingredients in the bowl during mixing. 
     The invention makes use of solid stainless steel to improve ease of sanitation and decrease cleaning costs for the mixer and the surrounding area of the production facility. 
     The above and other objects and advantages of the invention will be apparent from the description of the invention provided herein which may be best understood by reference to the following drawings in which embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a mixer configured according to an embodiment of the invention with the mixer bowl in a dumping position. 
         FIG. 1B  is a perspective view of a mixer configured according to an embodiment of the invention with the mixer bowl in an upright position. 
         FIG. 2A  is a perspective view of an agitator and a bowl configured according to an embodiment of the invention. 
         FIG. 2B  is a partial cross-sectional view taken on line  2   b - 2   b  of  FIG. 1B  of an agitator in a bowl configured according to an embodiment of the invention. 
         FIG. 3A  is a partial cross-sectional view taken on line  2   b - 2   b  of  FIG. 1B  of a bowl (with the agitator removed) configured according to one embodiment of the invention illustrating A, R 1 , R 2 , and D. 
         FIG. 3B  is a partial cross-sectional view taken on line  2   b - 2   b  of  FIG. 1B  of a bowl (with the agitator removed) configured according to one embodiment of the invention illustrating region Y. 
         FIG. 3C  is a partial cross-sectional view taken on line  2   b - 2   b  of  FIG. 1B  of the agitator in a bowl configured according to one embodiment of the invention and illustrating the placement of the agitator driveshaft in region Y according to an embodiment of the invention. 
         FIG. 3D  is a side view of the spider of three different embodiments of the invention. 
         FIG. 4  is a cross-sectional view taken on line  4 - 4  of  FIG. 2A  of a bowl and jacket configured according to one embodiment of the invention. 
         FIG. 5  is a perspective view of the channels disposed on the exterior bowl surface according to one embodiment of the invention. 
         FIG. 6A  is a front perspective partial view of the cover and the bowl seal configured according to one embodiment of the invention. 
         FIG. 6B  is a partial cross-sectional view of the cover and the retracted bowl seal configured according to an embodiment of the invention. 
         FIG. 7A  is a perspective partial view of the wiper configured according to an embodiment of the invention. 
         FIG. 8  is a partial cross-sectional view taken on line  8 - 8  of  FIG. 1A  of the agitator cooling passageway configured according to an embodiment of the invention. 
         FIG. 9A  illustrates an embodiment of a spider defining a spider arm entry passageway. 
         FIG. 9B  illustrates the transition from a spider arm entry passageway to a roller bar passageway. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is generally directed to a device and method of mixing yeast-raised and yeast-raised-type dough. The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope. 
       FIG. 1A  illustrates an embodiment of a mixer, generally labeled  10 , for mixing dough according to the method of this invention. The mixer  10  includes a frame  12  on which the mechanical components are disposed. Although not limited to this material, the frame may be made of solid stainless steel plates such that there are no corrosion sensitive materials in any part of the frame. In one preferred embodiment, the frame may be made of #304 solid stainless steel plates. Use of solid stainless steel plates, as opposed to a layer of stainless steel veneered over a core of another material, provides greater stability to the mixer while mixing dough, and improves the overall sanitation and ease of maintenance of the apparatus because solid stainless steel is corrosion-free. The mixer can be sprayed down with a cleaning liquid such as water without fear of corrosion forming on the mixer once a veneer of stainless steel has worn away and portions of an underlying corrosion sensitive core are exposed. 
     As shown in  FIGS. 1A-1B , the frame  12  comprises a right leg casing  14  and a left leg casing  16 , disposed on either end of a support casing  18 . Each leg casing has a top (respectively,  22  and  24 ) and an inner side wall (respectively,  26  and  28 ). A cover  30  is adjacent the frame and extends between the top ( 22 ,  24 ) of the right and left leg casings ( 14 ,  16 ) and may overlap a portion of each top ( 22 ,  24 ). A drive motor and an associated gear reducer (not shown) are disposed inside the support casing  18  and are mounted on plates that may be approximately ¼ inch to 2½ inches. 
     As shown in  FIGS. 1A-1B , the mixer also includes a bowl  100 . In  FIG. 1A , the bowl  100  is shown in a dumping position. In  FIG. 1B , the bowl  100  is in an upright position. The bowl  100  may be made of solid stainless steel, however, any other material suitable for use when mixing dough for human consumption may be used. In one embodiment, the bowl  100  may be made of #304 solid stainless steel. 
     An agitator driveshaft  210  is rotatably mounted within the bowl  100  and passes through the inner side wall ( 26 ,  28 ) of each leg casing ( 14 ,  16 ) and defines a driveshaft axis  212 . An agitator (generally marked  200  in  FIG. 2A ) is fixed to the agitator driveshaft  210  which rotates the agitator  200  as discussed below. The agitator driveshaft may be made of stainless steel. In one embodiment the agitator driveshaft may be made of #304 stainless steel. 
     Typically, different agitator designs are required for dough types with different absorption levels, flour protein levels and other formula variations. This often results in mixers that are customized for use with only one particular agitator design and, hence, only one particular dough type. The mixer of the present invention can accommodate various types of dough and can improve the mixing characteristics for each dough type by changing the agitator position within the mixing bowl and/or changing the agitator design to optimize performance, reduce mix time, improve aeration characteristics, and improve gluten alignment characteristics. 
     As shown in  FIGS. 2A-2B , the agitator  200  is comprised of spiders  214  each with spider arms  216  radiating from a central hub  218 , stretcher bars  220  (as discussed below), and roller bars  222  (as discussed below). In one embodiment, as illustrated in  FIGS. 2A-2B , the agitator  200  may have two spiders  214  each with three spider arms  216 . Greater or fewer spider arms may be used in other embodiments. The stretcher bars  220  and the roller bars  222  are disposed between the spiders  214  and are oriented substantially parallel to the agitator driveshaft  210 . A center point “B” is disposed substantially at the midpoint of the diameter of each stretcher bar  222 . The center points B of the stretcher bars  220  may be generally evenly spaced at 120 degrees apart from each other. A center point “C” is disposed substantially at the midpoint of each roller bar. The center points C of the roller bars  222  may be generally evenly spaced at 120 degrees apart from each other. The spiders  214  are mounted on the agitator driveshaft  210  and a spider arm  216  is attached at each end of the stretcher bars and roller bars ( 220 ,  222 ). Although not limited to this material, the spiders  214 , the stretcher bars  220 , and the roller bars  222  may be made of cast stainless steel. In one embodiment, the spiders  214 , the stretcher bars  220 , and the roller bars  222  may be made of cast #304 stainless steel. 
     As illustrated in  FIG. 2B , each spider arm  216  has a finger portion  226  arranged at an inclined angle relative to an inner edge  224 . In one embodiment, the angle between each inner edge  224  and the finger  226  is substantially an obtuse angle, and each angle is substantially the same. In other embodiments, an angle other than an obtuse angle may be used. As illustrated in  FIG. 2B , a boss  230  is attached to each finger adjacent to the pivot point  231  on the spider arm  216 . The stretcher bars  220  are mounted on these bosses  230 . The end of each finger  226  is provided with a bushing  232  for holding roller bars  222 . Each bushing is held in place by a bearing cap secured by bolts. The tubular roller bars  222  are enclosed at their ends by split, bolted hubs. Each end of each tubular roller bar  222  has a journal which fits into the bushings  232  so that each roller bar  222  is freely movable and rotates around the driveshaft axis  212  and spins in its (the roller bar) mounting around a roller axis  270  substantially parallel to the driveshaft axis  212 . The stretcher bars  220  may be fixed in some embodiments, and in others, may be allowed to spin on bushings. In the embodiment depicted in  FIGS. 1A and 2A , there are three stretcher bars  220 , three roller bars  222 , and three radiating spider arms  216  on the spiders  214 . In other embodiments, there may be fewer or more stretcher bars  220  or roller bars  222 . 
       FIG. 3A  illustrates a cross-sectional view of one embodiment of the bowl  100 . The bowl  100  is defined by two parallel sides  112  adjacent to a semicircular base  114 . The diameter of the semicircular base is designated as “X.” The midpoint of the diameter X of the semicircular base  114  is designated as “A.” The bowl is comprised of an interior bowl surface  116  and an exterior bowl surface  118 . The radius “R 1 ” of the semicircular base  114  extends from the midpoint A to the interior bowl surface  116  of the semicircular base  114 . “D” is the center point of the agitator driveshaft  210 . In one embodiment, the driveshaft center point D is disposed below the midpoint A such that the agitator driveshaft distance “R 2 ,” the distance between D and the interior bowl surface  116  of the semicircular base  114 , is about 72% to about 97% of the radius R 1 . The length of R 2  may vary, depending on the formula and the absorption level of the dough to be mixed; the aeration characteristics of higher absorption dough improves when D is positioned closer to A, and the aeration characteristics of lower absorption dough improves when D is positioned farther away from A. 
     The vertical axis in the bowl  100  is designated as “V.” In another embodiment of the invention, the placement of D may be moved forward or backward from the vertical axis V within the region shown as “Y” in  FIGS. 3B-3C . The region Y is a sector of approximately 36° defined by a vertex point Y 1 , which is disposed a distance of approximately 3% of R 1  directly below midpoint A, and a radius R 3  of approximately 25% of R 1  radiating outward from Y 1 , toward the interior bowl surface  116  of the semicircular base  114 . As illustrated in  FIG. 3B , the region Y is centered on the vertical axis V and extends approximately +18° from the vertical axis V and approximately −18° from the vertical axis V for a total combined angle of approximately 36°. 
     Changing the position of the agitator driveshaft  210  ( FIG. 2B ) center point D improves the aeration characteristics of the mixing process by changing the outline of the compression zone  132  ( FIG. 2B ) and the outline of the decompression zone  130  ( FIG. 2B ) around the agitator  200 . The most desirable location of the agitator driveshaft  210  center point D in region Y depends on the absorption level of the dough. For instance, for dough having low absorption characteristics, D may be disposed, in region Y, in the range of 0° to −18° from the vertical axis V. For the lowest-absorption dough type, D should be disposed, in region Y, approximately −18° from vertical axis V toward the rear of the bowl. For dough having high absorption characteristics, D may be disposed, in region Y, in the range of 0° to +18° from the vertical axis V. For dough having the highest absorption characteristics, D should be disposed approximately +18° from the vertical axis V. The entire region Y is an area of potential points where the driveshaft center point D of the agitator driveshaft  210  may be optimally located. 
       FIG. 3C  illustrates three exemplary positions of the driveshaft center point D in the region Y. The dough forms generated by placement of the agitator driveshaft  210  driveshaft center point D in the Y sector allow for higher operating RPMs of the agitator without causing gluten degradation in the dough or excess heat generation, and without causing mechanical vibrations in the mixer that reduce mixer component and bearing life cycles. In the first illustration in  FIG. 3C , generally labeled  140 , the agitator driveshaft  210  center point D is shown in region Y disposed for the lowest type of absorption dough. D is disposed approximately −18° from vertical axis V toward the rear of the bowl. In the third illustration in  FIG. 3C , generally labeled  160 , the agitator driveshaft  210  center point D is shown in region Y disposed for the highest type of absorption dough. D is disposed approximately +18° from vertical axis V toward the front of the bowl. In the second illustration in  FIG. 3C , generally labeled  150 , the agitator driveshaft  210  center point D is shown in region Y disposed for an average type of absorption dough. D is disposed approximately near the V axis. 
     For high-absorption through low-absorption yeast raised dough types, the agitator design may be modified for better performance and higher mixer RPMs by varying the position of the stretcher bars. For high-absorption dough, which is softer and has an extended dough form during mixing, the agitator may use spiders with high-lead stretcher bars  240  to increase the tumbling and rotation of the dough mass as it orbits around the agitator driveshaft  210 . As shown in  FIG. 3D , the radius “R 5 ” is the distance between D and the center point C of the roller bars  222 . The radius “R 4 ” is the distance between D and the center point B of the stretcher bars  220 . For spiders with high-lead stretcher bars, R 4  is about 0.80R 5  to about 0.84R 5  and the angle “E” substantially between B and C is about 20 degrees to about 30 degrees. The vertex for E is disposed on the driveshaft center point D. For average-absorption dough, the agitator may use spiders with mid-lead stretcher bars  250 . For spiders with mid-lead stretcher bars, R 4  is about 0.71R 5  to about 0.75R 5  and the angle “E” substantially between B and C is about 25 degrees to about 35 degrees. The vertex for E is disposed on the driveshaft center point D. For low-absorption dough, which is stiffer, heavier, and maintains a more compact dough form during mixing, the agitator may use spiders with low-lead stretcher bars  260  to increase the tumbling and rotation of the dough mass as it orbits around the agitator driveshaft  210 . In spiders with low-lead stretcher bars, R 4  is about 0.62R 5  to about 0.66R 5  and the angle “E” substantially between B and C is about 30 degrees to about 40 degrees. The vertex for E is disposed on the driveshaft center point D.  FIG. 3D  illustrates these three variations of the agitator design. 
     For dough having the highest absorption characteristics, the combination of an agitator with spiders designed for high-lead stretcher bars  240 , and placement in region Y of D approximately +18° from the vertical axis V at the lowest point in region Y, where R 2  is approximately equal to 72% of R 1 , generates the optimum mixing performance. For dough having average absorption characteristics, the combination of an agitator with spiders designed for mid-lead stretcher bars  250 , and placement in region Y of D approximately on the vertical axis V at the lowest point in region Y, where R 2  is approximately equal to 72% of R 1 , generates the optimum mixing performance. For dough having the lowest absorption characteristics, the combination of an agitator with spiders designed for low-lead stretcher bars  260 , and placement in region Y of D approximately −18° from the vertical axis V at the lowest point in region Y, where R 2  is approximately equal to 72% of R 1 , generates the optimum mixing performance. 
     According to another embodiment of the invention, a jacket and channels may be attached to a portion of or to the entire bowl  100  for optimized cooling of the dough while mixing. In this alternative embodiment, as shown in  FIG. 4 , a cavity  121  is defined between the exterior bowl surface  118  and a bowl jacket  120  surrounding at least a portion of the bowl  100 . One or more member(s)  122  are disposed in cavity  121 . The members  122  form a flow channel  124  adjacent to the exterior bowl surface  118 . In a preferred embodiment, the members  122  may be angle irons. The members  122  may be attached to the exterior bowl surface  118  by flux-core, inert gas welding. 
     In one embodiment, as illustrated in  FIGS. 4-5 , the channel  124  winds back and forth horizontally across at least a portion of the exterior bowl surface  118  in a serpentine configuration. In other embodiments, the channel  124  may wind around the entire exterior bowl surface in a spiral configuration, or the channel  124  may be disposed on the exterior bowl surface  118  in a configuration other than spiral or serpentine. Although not limited to this material, the channel  124  may be made of stainless steel. In one embodiment, the channel  124  may be made of #304 stainless steel. In the embodiment illustrated in  FIGS. 4-5 , there is a single continuous channel  124  disposed adjacent to the exterior bowl surface  118 . Inside the channel  124 , coolant  128  maintained at a desired cooling temperature circulates. The circulating coolant  128  reduces the temperature of the bowl  100  and the dough (not shown) being mixed in the bowl  100 . For example, 2000-lb. mixers have discharged dough at a temperature as low as 59° F. (15° C.) using coolants with a temperature of 15° F. (−10° C.). In one embodiment of the invention, glycol is used as a coolant, however, any coolant suitable for use with food-processing equipment may be used. The coolant enters one end  125  of the channel  124 , circulates through the entire channel  124 , and goes out the other end  127  of the channel  124 . A pump or other means may be used to circulate the coolant  128  through the channel  124 . 
     The channel  124  is generally V-shaped. To optimize the cooling performance, the V-shape may have approximately a 90-degree angle at its vertex. The V-shaped channel design distributes the pressure of the circulating coolant  128  such that more pressure is focused on the vertex and less pressure is focused on the welds. The V-shaped channel also helps minimize flexing of the bowl  100  during mixing, thereby reducing hardening of the welds applied to the channel  124 . Finally, the V-shaped design of the channel  124  increases the turbulence of the coolant  128  as it flows through the channel  124 , and thereby increases the thermal transfer to the dough inside the bowl  100 . 
     Insulating material  126  may be is disposed in the cavity between the channel  124  and the bowl jacket  120 . Preferably, the insulating material  126  is expanded urethane foam. The insulating material  126  and the bowl jacket  120  help prevent condensation from forming on the outside of the bowl and dripping onto the production floor of the facility where the mixer is installed. Although not limited to this material, preferably, the bowl jacket  120  is a welded stainless steel sheet attached to the bowl. In one embodiment, the bowl jacket  120  may be made of #304 stainless steel. 
     As illustrated in  FIG. 1A , the cover  30  has a front edge  32  and back edge  34 . Attached to the cover are a left extension  33  and a right extension  35 . The cover  30  and its extensions ( 33 ,  35 ) span the distance between the tops ( 22 ,  24 ) of the leg casings. Although not limited to this material, the cover  30  may be made of solid stainless steel plates. In one embodiment, the cover may be made of #304 solid stainless steel plate. In one embodiment, the cover  30  ands its extensions ( 33 ,  35 ) may be bolted to each top ( 22 ,  24 ). Disposed along at least one edge of the cover  30  is an inflatable bowl seal  31  as shown in  FIG. 6A . The bowl seal  31  is resilient and expandable. The bowl seal  31  may comprise an inflatable bladder. In one embodiment, a bowl seal  31  may be disposed on the front edge  32  and on the back edge  34  of the cover  30  and may extend across the opening of the bowl  100 . The bowl seal  31  may be pneumatically filled with air when the agitator  200  is operating so that it expands to fill the gap between the cover  30  and the bowl  100 , thus preventing migration of flour dust, water, and other ingredients out of the bowl  100 . Upon completion of mixing, the bowl seal  31  deflates and retracts away from the bowl  100 , as illustrated in  FIG. 6B . The bowl seal  31  is easily removable for periodic cleaning. In the embodiment shown in  FIG. 6B , a bowl lip  102  is disposed adjacent to the top of the bowl  100 . The bowl lip  102  may be adjacent to a portion of the perimeter of the top of the bowl  100  or adjacent to the entire perimeter of the top of the bowl  100 . 
     The mixer  10  may include a wiper  300  laterally movable along at least one rod  302 . In the particular embodiment illustrated in  FIG. 7A , there are two rods  302  mounted to the bowl  100 ; the wiper  300  is mounted adjacent to the bowl  100  on the rods  302  and moves laterally on the rods  302  across the bowl lip  102  of the bowl  100 . The rods  302  are attached in a substantially horizontal position to the bowl  100 . The movement of the wiper  300  across the bowl lip  102  reduces the amount of dough remnants on the bowl lip  102  (deposited by pouring of the dough) and, thus, improves the seal between the bowl lip  102  and the bowl seal  31 . 
     In one embodiment of this invention, cooled air at positive pressure or a combination of compressed inert gas and air is circulated through an interconnected cooling passageway  400  illustrated in  FIG. 8  as comprising a shaft entry passageway  402 , a spider arm entry passageway  404 , a roller bar passageway  406 , a spider arm exit passageway  408 , and a shaft exit passageway  410 . The agitator driveshaft  210  may define a shaft entry passageway  402 , and a shaft exit passageway  410 . A first spider may define a spider arm entry passageway  404 . A second spider may define a spider arm exit passageway  408 . In this invention, the term “air,” when used in reference to the agitator or the cooling passageway, refers to chilled air, or alternatively to a combination of compressed inert gas and air. The shaft entry passageway  402  is connected to at least one spider arm entry passageway  404 . The shaft exit passageway  410  is connected to at least one spider exit passageway  408 . Each roller bar  222  may define a roller bar passageway  406  connected between a spider arm entry passageway  404  and a spider arm exit passageway  408 . The combination of the roller bars extending and aligning the gluten structures in the dough without tearing as the roller bars spin, and the flowing of cooled air through the cooling passageway  400 , provides for superior mixing capabilities while reducing the heat generated by the agitator. For illustrative purposes,  FIG. 9A  illustrates an embodiment of a spider  214  defining a spider arm entry passageway  404 .  FIG. 9B  illustrates the transition from a spider arm entry passageway  404  to a roller bar passageway  406 . 
     As shown in  FIGS. 8-9B , in a preferred embodiment, the shaft entry passageway  402 , the spider arm entry passageway  404 , and the roller bar passageway  406  will be smaller in diameter than the spider arm exit passageway  408  and the shaft exit passageway  410  in order to reduce back pressure and improve air circulation. The journal at each end of each roller bar  222  has a groove  424 . A first groove ( FIG. 9B ) is aligned, inside the roller bar hub, with the passage through the spider arm to assist with the flow of circulating chilled air from the spider arm entry passageway  404  to the roller bar passageway  406 . The first groove allows access of the air flow from the spider arm entry passageway  404  to the roller bar passageway  406  at substantially all points of rotation of the roller bar  222 . Similarly, a second groove, at the other end of the roller bar, is aligned, inside the roller bar hub, with the passage through the spider arm to assist with the flow of circulating chilled air from the roller bar passageway  406  to the exit spider passageway  408  at substantially all points of rotation of the roller bar  222 . Removable seals  426  disposed adjacent to hub  412  prevent migration of chilled air. In one embodiment, a means for pumping the cooled air into the cooling passageway  400  may be used. One example of such a means is a cooling heat exchange unit that is used to pump the cooled air into the cooling passageway  400 . The heat exchange unit may be a glycol chiller with a fan that circulates the chilled air. Air with a temperature as low as 20° F. (7° C.) may be used with either the expanded gas and air combination, or the chilled air. This design allows either clean cooled air to circulate and chill the agitator, or the use of an expansion valve to harness the latent heat of expansion of the inert gas/air mixture to provide for the cooling effect on the circulated air. Lines  420  providing air, or a combination of gas and air may be connected to the agitator driveshaft  210  by a rotary connection  422 . An expansion valve, if used, may be disposed adjacent the rotary connection  422 . 
     This invention may utilize an independent, coupled drive motor and reducing gearbox combination, which is oriented horizontally to the mixer in order to lower the center of gravity of the overall mixer mechanical platform. An independent drive motor coupled to an independent gearbox allows for faster, easier maintenance with lower inventory expenses for bakers because when the motor requires removal for maintenance, this can be easily achieved without removing the gearbox and vice versa. This independent coupled design dramatically increases platform stability, rigidity, and maintenance of the alignment of all mechanical drive components due to this improved design. The horizontal orientation of the drive motor aids in improved life of the motor and gearbox shaft seals, which prevents leaking of lubricants into the motor and dough preparation areas. 
     This invention may use a Gates synthetic KEVLAR-geared, belt-driven system that reduces lubrication requirements, noise generation, alignment requirements, and maintains a cleaner mixer and production area by avoidance of lubrication requirements. A large diameter flanged hub with tapered-locked bushing inserts may be positioned on both sides of the belt-driving sprocket. The tapered-locked bushing inserts ensure that the drive belt does not come off of the driving sprocket at any time during regular operation. 
     Programmable Logic Controllers, in tandem with Variable Frequency Drive (VFD) systems, allow for control and monitoring of the electrical motors and drive systems. This invention may use a high-efficiency AC motor controlled by a VFD, to allow mixing speeds from 40 to 200 RPMs. In most mixers, applications at these rates cause severe, gluten degradation and tearing of the dough, as well as heat build up and poor aeration of the dough. The key design elements of this invention allow higher operating speeds, with gentle gluten alignment and development, while minimizing heat generation, and optimizing aeration or uniform air incorporation into the dough. 
     This invention may use hydraulic cylinders and actuators to effect the bowl  100  rotation for receiving ingredients and pouring of finished dough. The bowl  100  preferably will rotate on a heavy trunnion mounted in manganese bronze-bearing blocks. The rotational torque may be delivered by Parker Actuators driven by an electric hydraulic pump through a valve/regulator/solenoid stack. The heavy coupling or eccentric arm may be bolted or attached to the bowl trunnion with self-aligning couplers and preferably will affect a one-direction tilt to 140 degrees forward only or a dual-direction tilt to approximately 140 degrees forward and backward. Pneumatically operated bowl locks are engaged to support the bowl when operating in the upright mix position. A plate is used to mount the actuator to its support bracket in a manner that allows alignment and placement stability, even in the absence of the bracket-mounting bolts. This improves the ease of maintenance. 
     Preferably there will be at least two banks of zerk lubrication points on the frame  12  to allow easy, regular access to the main lubrication points of the mixer  10 , without interruption of mixer operation. These zerk points serve the rotation trunnions that are adjacent to the agitator driveshaft  210 , the main agitator shaft bearings, the belt tensioning pulley, the drive motor  36 , and the rear-bearing sets. The mixer frame  12  preferably will be built with access openings covered by doors attached by bolts or door hinge assemblies to the frame. Similar to the frame  12 , the doors may be made out of stainless steel although an acceptable alternative material may also be used. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and set forth in its entirety herein. 
     The use of the terms “a,” “an,” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.