The described invention relates in general to a system and apparatus for mixing viscous substances such as dough, and more specifically to a refrigerated agitator assembly which may be incorporated into industrial horizontal dough mixers for controlling the temperature of the substance being mixed during the mixing process.
Friction and viscous shear encountered during mixing typically causes a temperature rise in a substance being mixed. This temperature rise becomes more severe as mixing speed increases and can adversely affect a mixing process by making the substance sticky and difficult to process. Accordingly, mixers, particularly dough mixers, are most effective when equipped with some type of temperature control means, whereby the temperature of the substance to be mixed may be stabilized at a predetermined level or maintained below a predetermined threshold. For example, bread dough should be mixed at a temperature of about 78-80° F. A known means for controlling the temperature of a substance being mixed is through the use of a refrigeration jacket attached to the mixing bowl component of a mixer. Bowl refrigeration jackets, also referred to as “cooling jackets” usually include multiple coolant channels that are arranged perpendicular to the ends of a mixing bowl, and which are arrayed around the profile of the mixing bowl.
Large commercial scale dough mixers may be manufactured both with and without mixing bowl cooling jackets based primarily on the type and quantity of dough to be mixed. The performance, i.e., cooling capacity, of a refrigeration system used with a commercial scale mixer is the ability of the mixing bowl cooling jacket to remove heat from within the mixing bowl during a batch cycle. As previously indicated, major sources for heat generated during the mixing process are dough ingredient temperatures, ambient temperatures around the mixer, and heat generated from friction and shearing forces within the mixing bowl as the dough is processed. In some circumstances, these variables make it difficult or impossible for a mixing bowl cooling jacket to provide adequate cooling.
U.S. Pat. No. 6,047,558, which is incorporated herein by reference in its entirety for all purposes, teaches the use of a refrigerated agitator assembly as a means for increasing or enhancing the cooling capacity of a refrigeration system incorporated into a mixing apparatus. While effective for its intended purpose, this system is known to experience multiple sources of coolant leaks within the mixer product zone and to possess inefficient internal flow characteristics. Thus, there is an ongoing need in the art of dough mixing for a refrigerated agitator assembly having enhanced coolant sealing, simplified manufacturing, and more efficient cooling characteristics.