tray vacuum freeze dryer

A freeze dry unit having several novel features is the subject of this vacuum freeze dryer. A plurality of shelves are placed in the drying unit and are coupled with cables which serve to interconnect three points on each shelf. This assures that an upward force applied at any point on the shelf will be distributed over the entire shelf and the shelf will rise in a true horizontal plane. An improved refrigeration system is also provided which incorporates an auxiliary capillary tube that can be bypassed by a solenoid valve or used to reduce the volume of refrigerant flowing through the system thereby decreasing the load on the compressor.

Food drying equipment is a technique well known to those skilled in the art for preserving both plant and animal biological materials. For relatively small production or laboratory requirements, so-called “fluid bed dryer” have long been in use. These units are normally relatively small and are designed to freeze dry and stopper a large number of small vials or other “laboratory size” vessels. It is known in the art to utilize movable shelves inside of a stoppering tray dryer along with an inflatable bladder which raises one or more shelves until the stoppers on the vials of the shelf being raised contact the horizontal shelf or frame section immediately above it thus forcing the stoppers into sealing relationship with the vial.

Another difficulty with drying equipment of the type that have heretofore been commercialized is the need to size the refrigeration compressor to handle maximum cooling requirements, namely those required to effect the initial freezing of the sample. This means that once the sample is frozen and a vacuum is applied, there is excess refrigeration capacity because of the lowered pressure inside of the dryer.

It is also one of the objects of the vacuum freeze dryer to provide an improved locking mechanism for the door of a stoppering tray dryer which provides a more reliable seal than previous locking mechanisms as a result of applying the locking force at the center of the door.

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Stoppering tray vacuum freeze dryer

This vacuum freeze dryer relates generally to freeze drying equipment and, more particularly, to a freeze dryer which is provided with a mechanism for placing stoppers in vials subsequent to the drying step and before the vacuum conditions have been terminated

Freeze drying is a technique well known to those skilled in the art for preserving both plant and animal biological materials. For relatively small production or laboratory requirements, so-called “stoppering tray dryers” have long been in use. These units are normally relatively small and are designed to grain dryer and stopper a large number of small vials or other “laboratory size” vessels. It is known in the art to utilize movable shelves inside of a spray dryer along with an inflatable bladder which raises one or more shelves until the stoppers on the vials of the shelf being raised contact the horizontal shelf or frame section immediately above it thus forcing the stoppers into sealing relationship with the vial.

Stoppering tray dryers have heretofore encountered the problem that, when the shelves are raised, it is not always possible to keep the shelf in a horizontal plane. This may cause one or more vials to tip over or, if a vial is already tipped over, damage to the shelf or other vials may occur because of the unequal forces applied to the shelf when the inflatable bladder is actuated.

It is, therefore, a primary object of the present coffee processing equipment to provide a refrigeration unit which is particularly applicable, though not limited, to freeze dryers wherein the volume of refrigerant passing through the evaporator may be reduced when cooling requirements are less thereby reducing the load on the compressor so as to lengthen the life of the compressor and reduce energy requirements.

A further aim of the food drying equipment is to provide an improved door construction for a stoppering tray dryer wherein the door moves away from the adjacent sealing strip during opening so as to preclude damage to the seal by repeated opening and closing of the door.

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The Food Drying Equipment and Methods

A rotary food drying equipment is used in the preferred embodiment of this drying equipment for drying the food granules. In some cases, for certain types of food granules, a vacuum freeze dryer may also be used. In the drying of rice, for example, a rotary dryer and a bed dryer typically are used. Further, in making a highly dehydrated rice such as a quick rehydrating variety of rice, a vertical dryer also is used to reduce the moisture content of the rice to a low level.

Of course there are numerous methods of transporting the food granules from the steam cooker to the rotary drying apparatus, and transport by using a water slurry is only one method. For example, a dry transport method could use a combination of rice/air transport by blowing the rice through a conduit, or rice could be transferred on a conveyor belt, if sufficient apparatus (such a breakers) are employed to prevent lumping of the food granules.

The food granules are provided to the body of the grain dryer where they are dried as they proceed into the various heat zones of the dryer. The heat zones that may be seen in FIG. 14 are the first heat zone 268, the second heat zone 270, the third heat zone 272, and the fourth heat zone 274. The heat zones may be regulated to various temperatures for various types of drying, depending upon the food particle to be dried and the temperature of each zone may be regulated to achieve the maximum drying effect for the minimum amount of energy consumption of the spray dryer.

Four separate burners 222 are provided, one to each heat zone, and blower fans 56 recirculate heated air from the main drying chamber through the baffle plate 234 into the rotating barrel, and then into the recirculation duct 232 and then eventually back into the food drying equipment. As cooked food granules 238 proceed through the body of the dryer, their moisture content is reduced. Exhaust fan 216 is provided at the upper end of the rotary dryer to provide a positive air current flow along the path of the food particles being dried. Dried food granules 218 emerge from the distal end of the rotary dryer.

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