Patent Application
20050237852
The present invention is directed to a mixing apparatus. More particularly, the invention is directed to a mixing apparatus which comprises a viscosity sensor that is positioned in the outlet conduit instead of in a separate viscosity sensing conduit.
Prior art mixing machines are used in a variety of industries to mix an array of different ingredients. In the food industry, for example, batter mixing machines are commonly used to blend a dry batter mix with water to produce a batter coating that is subsequently applied to a food product. Controlling the viscosity of the batter coating is important to achieving a predictable cooking time, cooking yield, final weight and total cost for the coated food product. One method of controlling the viscosity of the batter coating involves monitoring its viscosity and adjusting the mixing process to maintain the viscosity at a desired level.
Therefore, prior art batter mixing machines usually include a viscosity sensor for measuring the viscosity of the batter coating. The viscosity sensor is often positioned in a viscosity sensing conduit through which the batter coating is circulated. This viscosity sensing conduit is typically separate from the outlet conduit which conveys the batter coating to, for example, a batter applicator. Consequently, prior art batter mixing machines must usually also include a separate pump to circulate the batter coating through the viscosity sensing conduit. However, requiring a separate viscosity sensing conduit and an additional pump necessarily increases the cost and complexity of the machine.
In accordance with the present invention, these and other disadvantages in the prior art are overcome by providing a mixing apparatus for mixing a first ingredient with a second ingredient which comprises a mixing tank in which the first and second ingredients are mixed, a mixing unit which mixes the first and second ingredients, first means for conveying the first ingredient to the mixing tank, second means for conveying the second ingredient to the mixing tank, an outlet assembly which is connectable to an outlet port in the mixing tank and which includes an outlet conduit, and a viscosity sensor which is positioned in the outlet assembly between the outlet port and the outlet conduit.
In one embodiment of the invention, the mixing tank comprises a return port, the outlet assembly comprises a return conduit which is connectable between the return port and a portion of the outlet assembly located upstream of the outlet conduit, and the viscosity sensor is positioned upstream of at least one of the outlet conduit and the return port. Alternatively, the viscosity sensor may be positioned upstream of both the outlet conduit and the return port.
Since the viscosity sensor is positioned in the outlet assembly between the outlet port and the outlet conduit, the mixing apparatus does not need a separate viscosity sensing conduit in order to measure the viscosity of the mixed ingredients. Consequently, the mixing apparatus does not require a separate feed pump to convey the mixed ingredients through a separate viscosity sensing conduit. In addition, when the viscosity sensor is positioned upstream of both the outlet conduit and the return port, the viscosity of the mixed ingredients may be measured when the mixed ingredients are flowing through either the outlet conduit or the return conduit. Thus, the viscosity of the mixed ingredients can be measured at almost any time during the operation of the mixing apparatus.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings.
Referring to
The components of the mixing apparatus 10 are preferably supported as a unitary assembly on a frame 24. Referring to
Referring to
In addition, the body 46 may comprise a double-walled portion which houses a heat exchanger that is connected between an inlet refrigeration port 76 and an outlet refrigeration port 78. The refrigeration ports 76, 78 may in turn be connected to an external refrigeration unit (not shown), which circulates a refrigerant through the heat exchanger to maintain the temperature of the batter mixture at a desired level.
The mixing tank 12 is supported on the frame 24 in a generally upright position, with the bottom surface 48 resting on both the cross beams 30 and the struts 32. Although the weight of the mixing tank 12 may be sufficient to hold it in place relative to the frame 24, the mixing tank may include a number of brackets 80, which as shown in
As best seen in
Referring to
Referring again to
Referring now to
The bin portion 122 of the feed hopper 16 comprises a generally vertical front wall 128, a generally vertical rear wall 130, and a pair of inwardly sloping upper sidewalls 132 which are connected such as by welding to the front and rear walls 128, 130. In addition, the rear wall 130 may include an inwardly projecting lip 134 to help isolate certain components of the conveyor apparatus 126 from the dry batter mix.
The conveyor portion 124 of the feed hopper 16 comprises two generally vertical lower sidewalls 136, each of which is connected to or formed integrally with a corresponding upper sidewall 132. Each lower sidewall 136 includes a nose portion 138 that projects beyond the front wall 128 and a lower edge that is bent laterally inwardly to form an elongated rail 140. The conveyor portion further includes a cross bar 142 which is connected between the rails 140 proximate the nose portions 138 and a generally planar removable pan 144 that is slidably supported on the rails. The removable pan 144 is connected to or formed integrally with a rear panel 146 which is ideally configured to follow the contour of the rear portion of the lower sidewalls 136. In addition, the rear panel 146 is releasably secured to the rear wall 130 with, e.g., a hold down clamp 148 and is also optimally provided with a handle 150. Thus, by releasing the hold down clamp 148, both the rear panel 146 and the removable pan 144 may be removed to provide access to the conveyor apparatus 126.
The area of the feed hopper 16 which is bounded by the front wall 128, the lower sidewalls 136 and the removable pan 144 forms a generally rectangular opening 152 which, when the mixing apparatus 10 is assembled, communicates with the aperture 54 in the mixing tank 12. The height of the opening 152 is established by a header plate 154 which extends between the lower sidewalls 136. The header plate 154 is preferably adjustably connected to the front wall 128 by, e.g., a wing nut 156 that is threaded onto a bolt which is welded to the front wall and which extends through a vertical slot in the header plate. Consequently, the height of the opening 152 may be adjusted by simply loosening the wing nut 156. In this manner, a desired rate for the flow of dry batter mix into the mixing tank 12 may be established by adjusting the height of the opening 152 depending on the speed of the conveyor apparatus 126.
The conveyor apparatus 126 can comprise any suitable conveyor which is capable of transporting the dry batter mix from the feed hopper 16 to the mixing tank 12. For example, the conveyor apparatus 126 may comprise the Flat-Flex® wire belt conveyor which is sold by the Wire Belt Company of America of Londonderry, N.H. The conveyor apparatus 126 includes a drive shaft 158 which extends through the lower sidewalls 136 and on which are mounted a number of sprockets 160 that engage a continuous wire conveyor belt (not shown). The wire conveyor belt travels over a conventional nose roller assembly 162 which extends between and is connected to the nose portions 138 of the lower sidewalls 136. As shown in
The drive shaft 158 is rotationally supported in a pair of flange mounted ball bearing assemblies 166. Referring also to
The drive shaft 158 is driven by a conveyor motor 174 through a gear box 176. The conveyor motor 174 and the gear box 176 may comprise a unitary drive assembly 178, such as the R-Series parallel gear motor which is sold by SEW-Eurodrive, Inc. of Troy, Ohio. The drive assembly 178 is activated by the control circuit which is located in the console 22. In addition, the drive assembly 178 is secured to the frame 24 via a motor mount 180 which is attached to the upright support member 36.
The rear portion of the feed hopper 16 is preferably pivotably supported on the frame 24 via a number of bearing devices which are mounted concentrically over the drive shaft 158. As shown in
Accordingly, the feed hopper 16 may be pivoted from its normal operating position to a vertical position to facilitate maintenance and cleaning of the mixing apparatus 10. In this regard, the mixing apparatus 10 ideally includes means for retaining the feed hopper 16 in its vertical position. Referring again to
The front portion of the feed hopper 16 is preferably freely supported relative to the frame 24 on one or more suitable spring means. Referring to
In addition, the mixing apparatus 10 preferably includes a hopper sensor 202 for detecting the movement of the front portion of the feed hopper 16 relative to a fixed portion of the mixing apparatus. For example, the hopper sensor 202 may comprise a proximity sensor, such as a conventional inductive-type proximity sensor, which is mounted to the mixing tank 12 adjacent the removable pan 144. The hopper sensor 202 is optimally connected to the control circuit in the console 22 and is ideally designed to generate an appropriate signal when the springs 198 push the feed hopper 16 away from the brackets 200 a predetermined distance. This signal is representative of the fact that the quantity of dry batter mix in the feed hopper 16 has fallen below the desired minimum level. In response to this signal, the control circuit preferably generates an appropriate audible or visual message to inform the operator that the quantity of dry batter mix in the feed hopper 16 has fallen below the desired minimum level.
Referring again to
In addition, the supply assembly 18 ideally comprises a bypass flowline 218 which includes a first end that is connected to the main flowline 206 upstream of the regulator 214 and a second end that is connected to the main flowline downstream of the water supply valve 216. The bypass flowline 218, which comprises a suitable flow control valve 220, such as a manually-operated ball or plug valve, allows the operator to quickly fill the mixing tank 12 with water without being impeded by the regulator 214.
The main flowline 206 and the bypass flowline 218 can comprise any combination of suitable pipes and connectors. In addition, the components of the supply assembly 18 are optimally secured to the frame 24 by a number of clamps 222 which are connected to a support plate 224 that is attached to the brace members 34.
Referring once again to
The first, second and third conduits 246, 248 and 250, as well as the outlet conduit 252 and the return conduit 254, may comprise any combination of suitable pipes and fittings. In one embodiment of the invention, these pipes and fittings are constructed of a durable, sanitary material, such as stainless steel, and are connected together by conventional sanitary clamps to facilitate their breakdown for maintenance and cleaning. In addition, the return conduit 254 may include a length of relatively flexible tubing 256, such as a braided PVC tubing, to accommodate any misalignment between the second valve outlet 244 and the return port 60.
The feed pump 226 may comprise any pump which is capable of pumping a specified batter mixture at a desired rate. A suitable feed pump 226 may comprise, for example, the Model C114 centrifugal pump which is sold by Waukesha Cherry-Burrell of Delavan, Wis. The feed pump 226 is preferably activated by the control circuit in the console 22 and is mounted to the frame 24 via a motor mount 258 which is connected to the first stretcher members 38.
The viscosity sensor 232 can comprise any suitable device which is capable of sensing the viscosity of the batter mix in the outlet assembly 20. In one embodiment of the invention, the viscosity sensor 232 comprises a continuous flow viscosity sensor, that is, one which is capable of sensing the viscosity of the batter mix “on the fly” as it flows through the outlet assembly 20. In a more preferred embodiment of the invention, the viscosity sensor 232 comprises a vibratory-type sensor which includes a vibrating sensing element that is contacted by the batter mix flowing through the outlet assembly 20.
Such a viscosity sensor 232 can comprise, for example, the AST-100® Viscometer which is sold by Brookfield Engineering Laboratories of Middleboro, Mass. This viscosity sensor 232 includes a control system which is preferably housed in the console 22 and is connected to the control circuit for the mixing apparatus 10. The viscosity sensor 232 supplies the control circuit with a signal which is representative of the viscosity of the batter mix that is flowing through the outlet assembly 20, which is generally the same as the viscosity of the batter mix in the mixing tank 12. Also, the viscosity sensor 232 may include a temperature sensor for detecting the temperature of the batter mix as it flows through the outlet assembly 20.
The flow control valve 238 may comprise any suitable valve or combination of valves which is capable of selectively directing the flow of batter mix from the third conduit 250 to either the outlet conduit 252 or the return conduit 254. In one embodiment of the invention, the flow control valve 238 comprises a three-way diverter valve which is designed to selectively connect the valve inlet 240 with either the first valve outlet 242 or the second valve outlet 244. The flow control valve 238 includes a closure member which is movable between a first position in which the valve inlet 240 is connected to the first valve outlet 242, a second position in which the valve inlet is connected to the second valve outlet 244, and preferably also a third position in which the valve inlet is isolated from both the first valve outlet and the second valve outlet. The closure member may be moved manually via a handle 260 or, alternatively, via a solenoid which is activated by the control circuit in the console 22. Thus, the flow control valve 238 allows the batter mix to be pumped from the mixing tank 12 to either the outlet conduit 252 or back into the mixing tank via the return conduit 254. Of course, the flow control valve 238 could be replaced with, for example, two separate valves, one of which is positioned between the third conduit 250 and the outlet conduit 252 and the other of which is positioned between the third conduit and the return conduit 254.
Furthermore, since the viscosity sensor 232 is positioned upstream of the flow control valve 238, it can sense the viscosity of the batter mix whether the batter mix is pumped through the outlet conduit 252 or the return conduit 254. Thus, as long as the batter mix is flowing through any portion of the outlet assembly 20, the viscosity sensor 232 can determine the viscosity of the batter mix. Consequently, the mixing apparatus 10 eliminates the need to divert the batter mix through a separate viscosity sensing conduit in order to check the viscosity of the batter mix.
Referring again to
The level sensor 262 is preferably shielded from ambient light by a shroud 264 which is positioned over the window 88 in the lid 52. In addition, the level sensor 262 is ideally movably supported on a bracket 266 which in turn is secured to the frame 24 via a cross bar 268 that is connected between the upstanding brace members 34.
Referring now to
The controller 272 ideally receives input signals from the lid switch 100, the hopper sensor 202, the viscosity sensor 232 and the level sensor 262. Based on these signals, the controller 272 selectively activates the mixer motor 106, the conveyor motor 174, the water supply valve 216 and the feed pump 226. The controller 272 may also receive certain information from the operator via an input device 274 and communicate specific information to the operator via a display unit 276. For example, the operator may input a desired viscosity for the batter mix using the input device 274, which as shown in
The controller 272 preferably controls the operation of the mixer motor 106 in response to the signal from the viscosity sensor 232, which as mentioned above is representative of the measured viscosity of the batter mix in the mixing tank 12. In particular, the controller 272 controls the speed of the mixer motor 106 by sending an appropriate mixer control signal to the variable speed drive which powers the mixer motor. The controller 272 determines the appropriate mixer control signal by, for example, accessing a look-up table which lists the preferred mixer motor speed for each of a number of measured viscosity ranges. For example, if the measured viscosity is between 0 and 100 centistokes, the preferred mixer motor speed may be 400 rpm; if the measured viscosity is between 100 and 200 centistokes, the preferred mixer motor speed may be 550 rpm; and if the measured viscosity is between 200 and 300 centistokes, the preferred mixer motor speed may 700 rpm. The preferred mixer motor speeds may be determined empirically for each of a number of batter viscosities.
Thus, at predetermined intervals during the operation of the mixing apparatus 10, the controller 272 will sample the signal from the viscosity sensor 232 and, based on this signal, will determine a preferred mixer motor speed. The controller 272 will then send a corresponding mixer control signal to the variable speed drive, which will drive the mixer motor 106 at that speed.
The controller 272 ideally controls the operation of the conveyor motor 174 and the water supply valve 216 in accordance with a Proportional-Integral-Derivative (“PID”) control scheme which depends on the difference between the desired and measured viscosities of the batter mix. The desired viscosity is a process set point which the operator communicates to the controller 272 via the input device 274. The difference between the desired viscosity and the measured viscosity defines a viscosity offset value which the controller 272 uses to control the operation of the conveyor motor 174 and the water supply valve 216. For example, if the measure viscosity is lower than the desired viscosity, the controller 272 will activate the conveyor motor 174 for a length of time which is proportional to the viscosity offset value to add more dry batter mix to the mixing tank 12. Similarly, if the measured viscosity is higher than the desired viscosity, the controller will open the water supply valve 216 for a length of time which is proportional to the viscosity offset value to add more water to the mixing tank 12.
In operation of the mixing apparatus 10, the viscosity sensor 232 will continually sense the viscosity of the batter mix and generate a signal which is representative of this measured viscosity. Periodically, for example every ten to fifteen seconds, the controller 272 will sample the signal from the viscosity sensor 232 and calculate the viscosity offset value. Depending on the sign of the viscosity offset value, the controller 272 will then activate either the conveyor motor 174 or the water supply valve 216 for a length of time which is proportional to the magnitude of the viscosity offset value. Simultaneously, the controller 272 will adjust the speed of the mixer motor depending on the measured viscosity, as discussed above.
The controller 272 preferably also samples the signal from the level sensor 262 periodically in order to monitor the level of batter mix in the mixing tank 12. Based on this signal, if the controller 272 determines that the level of batter mix has fallen below a desired minimum level, the controller will activate the conveyor motor 174 and open the water supply valve 216 in order to refill the mixing tank 12. The controller 272 will then deactivate the conveyor motor 174 and close the water supply valve 216 when the signal from the level sensor 262 indicates that the level of batter mix has reached a desired maximum level.
The desire minimum and maximum levels of batter mix in the mixing tank 12 may be entered into the controller 272 by the operator using the input device 274. Alternatively, these levels may be programmed directly into the level sensor 262. In addition, the operator may change the desired minimum and maximum levels depending on the requirements of a particular mixing process. Thus, the mixing apparatus 10 is capable of processing any desired amount of batter mix in a single batch.
The controller 272 may also control certain other aspects of the mixing apparatus 10 based on signals from the lid switch 100 and the hopper sensor 202. For example, if the signal from the lid switch 100 to the controller 272 is interrupted, which is indicative of the fact that either the switch plate 92 has been raised or the lid 52 removed, the controller may deactivate either the mixer motor 106, the conveyor motor 174, the water supply valve 216, or the feed pump 226, or any combination of these devices. In addition, if the signal from the hopper sensor 202 to the controller 272 is interrupted, which is indicative of the fact that the amount of dry batter mix in the feed hopper 16 has fallen below a desired minimum level, the controller 272 may generate a message which prompts the operator to refill the feed hopper or, alternatively, deactivate the conveyor motor 174 and/or the feed pump 226.
The mixing apparatus 10 may also be provided with a number of emergency stop switches which when actuated will deactivate the mixer motor 106, the conveyor motor 174, the water supply valve 216, and the feed pump 226. For example, a first emergency stop switch 278 may be located at the front of the mixing apparatus 10 on the console 22. Also, as shown in
It should be recognized that, while the present invention has been described in relation to the preferred embodiments thereof, those skilled in the art may develop a wide variation of structural and operational details without departing from the principles of the invention. Therefore, the appended claims are to be construed to cover all equivalents falling within the true scope and spirit of the invention.
