Methods and Apparatus for Chilling a Product

The present invention relates to methods and apparatus for chilling a product and more particularly to methods and apparatus for chilling such product in a blender device with the use of carbon dioxide as a refrigeration medium.

In the course of processing products such as ground meats it is frequently necessary to chill such meat to enable further processing operations to be effected. Large batches of meat products such as ground beef, ground pork, etc. are typically chilled from temperatures of about 40.degree. F. to approximately 28.degree. F. thereby enabling formation of the product in particular shapes such as hamburgers, etc. In order to chill such products, it has been common to utilize blending devices wherein the product to be chilled is mixed with a refrigerant to reduce the average product temperature to a desired level. In the past, blender devices have typically included one or more trough sections in which a mixing element such as a rotatable auger or ribbon screw member is operated so as to pass the products being chilled into contact with the refrigerant thereby reducing product temperature.

Carbon dioxide has been utilized as a refrigerating medium for chilling products in a blending device. Typically, the blender is provided with a cover across the top thereof and means for injecting carbon dioxide through the cover into the interior of the enclosed blender. Those skilled in the art will appreciate that devices known as "snow horns" may be mounted on such a cover and extend therethrough so as to discharge a mixture of solid and gaseous carbon dioxide into the interior of the blender. The cover is typically provided with an exhaust plenum or other means for removing carbon dioxide vapor which is introduced into the blender with solid CO.sub.2 and which forms in the blender upon sublimation of the solid carbon dioxide. In operation, the top of the blender is raised and a batch of product to be chilled is introduced into the blender device. The top is then lowered and carbon dioxide is supplied by snow horns as CO.sub.2 gas and snow into the blender while the mixing elements are actuated. A suitable exhaust fan in the exhaust plenum system is energized so as to remove CO.sub.2 vapor from beneath the blender cover and thereby avoid the buildup of excessive quantities of CO.sub.2 gas in the blender. Upon the product reaching a predetermined reduced temperature, the supply of carbon dioxide is terminated and the product is removed from the blender. This may be achieved by terminating operation of the mixing elements and opening the blender top to permit the product to be `dumped` or opening bottom trap doors. Alternatively, the mixing elements, e.g. screw devices may continue to operate to discharge chilled product through end doors of a blending device of this type. Discharge of the chilled product will enable cleaning of the mixing members and the blender interior. One system for introducing carbon dioxide into a blender through top mounted snow horns is illustrated in U.S. Pat. No. 4,314,451, which is assigned to the assignee of the present invention.

Although the blender devices described above are effective to reduce the temperature of a product, there are several disadvantages attendant to such blending systems. First, it has been found difficult and time consuming to load and unload product into and from a blender as it is necessary to open and close the top cover of the blender. The cover is a relatively heavy member which usually requires hydraulic or pneumatic raising and lowering devices to enable opening and closing thereof. These hydraulic or pneumatic lifting devices are costly and require maintenance to assure effective operation. In addition, the presence of a cover, even in an open position, reduces access to the blender interior and thus renders cleaning of the blender more difficult and time consuming.

The introduction of carbon dioxide through a blender cover as described above is not particularly efficient from a refrigeration viewpoint. It has been found that by expanding liquid carbon dioxide through a nozzle in a snow horn, considerable refrigeration exists in the CO.sub.2 gas thus formed. Although this gas will contact the top surface of product being mixed with solid carbon dioxide, relatively little refrigeration available in such CO.sub.2 gas is utilized in chilling the product. In addition, solid carbon dioxide which is mixed with the product tends to sublime rapidly and a portion of the solid carbon dioxide introduced into the blender will sublime before being thoroughly mixed with the product. Consequently, a significant portion of the refrigeration available from solid CO.sub.2 is not realized in actually reducing temperature of the product being chilled. Thus, blender systems utilizing top mounted snow horns having not been as efficient as desired in terms of utilizing refrigeration available from carbon dioxide.

It has been proposed to introduce carbon dioxide into the lower portions of chilling systems to enable passage of products to be chilled through the carbon dioxide and obtain a greater degree of refrigeration available from the carbon dioxide so introduced. One such system is illustrated in U.S. Pat. No. 3,468,135 wherein a fluidized bed of carbon dioxide is maintained in the lower portion of a chilling device and products are passed through this fluidized bed of CO.sub.2. In this system a set of impellers is utilized to impart continuous motion to the bed of carbon dioxide to fluidize the same and cause solid carbon dioxide particles to contact the product being passed therethrough. A cover is required to retain the solid CO.sub.2 within the chilling system and although impellers may be effective to fluidize carbon dioxide, such devices tend to impart heat into the portion of the system containing the carbon dioxide refrigerant which in turn is effective to reduce the refrigeration of such carbon dioxide. Consequently, the chilling system described in this reference is not considered to be a particularly effective technique for chilling products and is not considered suitable for chilling products such as ground meat.

Accordingly, there is a clear need for a blending system and method for chilling products which does not require a top cover and associated lifting devices yet which enables efficient use of an expendable refrigerant.

It is an object of the present invention to provide improved methods and apparatus for chilling products.

It is another object of the present invention to provide improved methods and apparatus for chilling products with the use of carbon dioxide as a refrigerant.

It is a further object of the present invention to provide improved methods and apparatus for chilling products in a blender having an open top yet without incurring excessive consumption of refrigerants.

It is still another object of the present invention to provide improved chilling apparatus which does not require excessive cleaning and maintenance.

It is yet another object of the present invention to provide an open top blender from which rising CO.sub.2 vapor is readily collected.

Other objects of the present invention will become apparent from the following description of exemplary embodiments thereof which follows and the novel features will be particularly pointed out in conjunction with the claims appended hereto.

In accordance with the invention, a product is chilled by directly mixing carbon dioxide and the product in a blender having one or more trough means and an open top, means for injecting liquid carbon dioxide into the trough below the surface of product, mixing means disposed in the trough and adapted to be driven so as to mix the product with solid and gaseous carbon dioxide formed in the trough to thereby chill the product, and deflector means disposed essentially along and above sidewalls of the trough for directing CO.sub.2 vapor rising from the open top of the trough means toward an exhaust device. The product to be chilled in the blending apparatus according to the invention is typically a food product such as ground meat and may comprise ground beef, ground pork, ground chicken, etc. Mixing means disposed in the blender trough typically take the form of a rotatable helical ribbon, screw or auger which when driven is effective to mix carbon dioxide introduced into the trough and the product being chilled. The mixing members are driven in a direction countercurrent to the direction in which carbon dioxide is introduced into the trough at a location below the surface of the product. By so introducing carbon dioxide, the weight of the product and the mixing member is effective to dampen the momentum of the introduced solid and gaseous CO.sub.2 which in turn permits mixing of carbon dioxide and the product with relatively low turbulence and thus enables CO.sub.2 vapor leaving the trough to rise along one wall and to be readily collected by an exhaust plenum above the open top of the blender device.

A plurality of troughs may be utilized with a single blender device and carbon dioxide may be introduced into each trough at a plurality of locations along the length thereof. Preferably, carbon dioxide is introduced at a location below the surface of product in the trough and at a slight angle downwardly from horizontal although CO.sub.2 may be introduced into the trough at a slight upward angle or even horizontally. The deflector means provided with the trough in accordance with the invention preferably extend along the length of the trough and over the open top of the trough to the extent necessary to deflect rising CO.sub.2 vapor to an exhaust plenum. In effect, the deflector means comprise a lip which overhangs a minor portion of the width of the blender. An exhaust plenum may be located above and at one end of the open top blender device or above and on one side of such device.

The invention will be more clearly understood by reference to the following description of exemplary embodiments thereof in conjunction with the following Drawing in which the sole FIGURE is a partial elevational view of the cross section of a blending device according to the invention.

Referring now to the Drawing, illustrated therein is an exemplary embodiment of a blending device 10 which is provided with two trough sections 12 and 14. A pair of mixing means 16 and 18 which may comprise a rotatable ribbon screw are mounted for rotation about central shafts 20 and 22, respectively. Support members 24 and 26 are provided to securely mount associated mixing means 16 and 18 to the appropriate shafts 20, 22. It will be understood that mixing means 16 and 18 may be comprised of elements such as an auger or rotatable screw member which are effective to mix a solid product such as ground meat with a refrigerant in a manner as will be described below. Liquid carbon dioxide is supplied through conduits 30 and 32 each of which is appropriately connected to nozzles 31 and 33, respectively. Upon discharging liquid CO.sub.2 through nozzles 31 and 33, solid and gaseous CO.sub.2 will be formed in troughs 12 and 14 of blending device 10. Preferably, liquid CO.sub.2 is injected into troughs 12 and 14 in a slight downward direction of approximately 15.degree. from the horizontal although the angle at which such liquid CO.sub.2 is supplied to troughs 12 and 14 may be horizontal or even at a slight upward direction. In the latter event, liquid CO.sub.2 is directed through the walls of troughs 12 and 14 toward apex 28 between such troughs. Although the product to be chilled is not illustrated in the drawing to thereby enable a better understanding of the invention, the level at which nozzles 31 and 33 are mounted in the walls of troughs 12 and 14 will be such as to assure that liquid CO.sub.2 is introduced into these troughs at a location below the upper surface of product therein.

Deflector means 34 and 36 are preferably comprised of elongated members rigidly secured to the upper portion of the side walls of troughs 12 and 14. Deflector means 34 and 36 are preferably configured in the form of lip members which extend over the open top of blending device 10 to a relatively minor degree but to an extent sufficient to cause CO.sub.2 vapors rising along the inner surface of trough walls to be directed toward an exhaust plenum 38 which is illustrated as positioned above the open top of blending device 10. It will be understood that plenum 38 may be located at one side or end of blending device 10 or thereabove as depicted in the drawing. The actual geometrical configuration of deflector means 34 and 36 is not critical although members having an L-shaped cross section will generally be adequate to serve the purpose mentioned above. Preferably, deflector means 34 and 36 extend along substantially the complete length of the side walls of trough means 12 and 14. In a typical blending device 10, deflector means 34 and 36 may, for example, extend approximately 3 inches over the width of the open top of the blending device and may be removably mounted on the side walls.

The operation of blending device 10 will now be described. Initially, a charge or batch of product such as ground beef, pork, etc. will be introduced into troughs 12 and 14 to a height above the location at which nozzles 31 and 33 are disposed in the side walls of troughs 12 and 14. Mixing means 16 and 18 are actuated by energization of a drive motor (not shown) which in turn is effective to rotate shafts 20 and 22 thereby rotating mixing means 16 and 18. Liquid carbon dioxide is then introduced through appropriate valves (not shown) through conduits 30 and 32 and is injected into the product within troughs 12 and 14 through nozzles 31 and 33, respectively. Operation of mixing means 16 and 18 will be effective to continuously cause solid and gaseous carbon dioxide formed in troughs 12 and 14 to directly contact the product therein. This contact will result in a chilling of the product as solid carbon dioxide is sublimed and refrigeration of the cold CO.sub.2 gas is yielded to the product.

Mixing means 16 is rotated in the direction of arrow A while mixing means 18 is rotated in the direction of arrow B. The rotation of mixing means 16 and 18 will be effective to pass product in troughs 12 and 14 countercurrent to the direction at which liquid carbon dioxide is supplied into each trough. This countercurrent contact between product being chilled and CO.sub.2 introduced into each trough is effective to dampen or reduce the momentum of the supplied solid and gaseous carbon dioxide and thereby achieve a relatively low turbulence contact between the CO.sub.2 refrigerant and product being chilled. It will be understood that typically liquid carbon dioxide is supplied to each of nozzles 31 and 33 under pressures of approximately 200-300 psig. By introducing the resulting solid and gaseous carbon dioxide at a location considerably below the surface of product in troughs 12 and 14, the weight of such product and the weight of the mixing means 16 and 18 will be sufficient to dampen or reduce the momentum of such CO.sub.2. This will avoid lifting of the product out of the blender and will tend to retain such carbon dioxide in contact with the product being chilled rather than simply permitting the resulting CO.sub.2 snow and vapor to exit trough means 12 and 14 without yielding a considerable portion of the refrigeration available in such carbon dioxide. The passage of product being chilled countercurrent to the stream of CO.sub. 2 solid and gas is also effective to maximize contact between the product and this refrigerant thereby enabling a more effective use of CO.sub.2 as a refrigerant. Moreover, by passing product being chilled and the solid and gaseous carbon dioxide stream in a countercurrent relationship as described above, it has been found that the majority of CO.sub.2 vapor either introduced into troughs 12 and 14 as vapor or resulting from sublimed solid carbon dioxide will rise along the outer walls of troughs 12 and 14 and will be readily directed by deflector means 34 and 36 to exhaust plenum 38. Consequently, a complete cover or top for troughs 12 and 14 is not required as the CO.sub.2 vapor rising from the open top of troughs 12 and 14 will be readily directed by deflectors 34 and 36 to exhaust plenum 38. Consequently, by utilizing deflector means 34 and 36 and a stream of solid and gaseous CO.sub.2 as mentioned above, the need for a cover over such troughs and associated raising and lowering equipment can be eliminated without impairing the capability of exhaust plenum 38, which as mentioned above, is preferably disposed at one end of troughs 12 and 14, to collect CO.sub.2 vapors rising from the open top of the troughs.

In addition to directing CO.sub.2 vapors toward exhaust plenum 38, deflector means 34 and 36 are effective to prevent the spillage of product over the side walls of troughs 12 and 14. Furthermore, it has been found that by introducing solid and gaseous CO.sub.2 through nozzles 31 and 33 at a location toward the bottom of troughs 12 and 14, the temperature of CO.sub.2 vapor reaching exhaust plenum 38 will be considerably higher than is the temperature of vapor exhausted through a typical exhaust plenum provided with a blender employing injection of CO.sub.2 through a top or cover. For example, is has been found with the latter type of blending systems that the temperature of such CO.sub.2 vapor in an exhaust plenum will be typically about -20.degree. to -30.degree. F. while with apparatus according to the invention, temperatures have been measured in a exhaust plenum on the order of approximately 35.degree. F. The significance of such a temperature differential between CO.sub.2 vapor evolved from the operation of apparatus according to the invention and prior art apparatus is that the higher the temperature of the exhausted CO.sub.2 vapor, the more refrigeration contained in liquid CO.sub.2 supplied to the blending device is actually consumed in chilling product. Thus, the apparatus according to the invention enables more efficient chilling of product in terms of the amount of carbon dioxide required to chill a given amount of product to a particular temperature. In addition, it has been found that virtually no solid CO.sub.2 is drawn into exhaust plenum 38 upon operation of blending device 10 in accordance with the invention while with blending devices utilizing top injection of CO.sub.2 snow and gas, some solid CO.sub.2 or snow is frequently found in the exhaust plenum associated therewith. Consequently, avoidance of the exhaust of solid CO.sub.2 particles will, in accordance with the invention, result in the sublimation of such particles in a manner more likely to yield useful refrigeration of the product being chilled.

It will be appreciated that conventional equipment may be utilized to supply liquid CO.sub.2 through conduits 30 and 32 and through nozzles 31 and 33 as described above. In addition a vapor purge of such conduits and nozzle may be effected so as to avoid the plugging thereof by the formation of solid CO.sub.2. It has been found, however, that such a vapor purge is not necessary when pneumatically operated ball valves (not shown) are utilized in connection with conduits 30 and 32. Furthermore, in order to comply with cleaning requirements, nozzles 31 and 32 may be purged of any product which may adhere thereto by simply permitting the appropriate CO.sub.2 supply equipment including conduits 30, 32 and nozzles 31 and 33 to reach ambient temperature such that any liquid CO.sub.2 admitted therethrough will vaporize. The resulting vapor pressure will be sufficient to purge nozzles 31 and 33 thereby satisfying cleaning requirements.

The foregoing and other various changes in form and details may be made without departing from the spirit and scope of the present invention. Consequently, it is intended that the appended claims be interpreted as including all such changes and modifications.