The present invention relates to a freezing apparatus and, more specifically to a freezing device for quickly chilling or freezing articles, such as foodstuffs, in a chilly ambience by exposing the entire surfaces of the articles to a chilly atmosphere.
In a conventional freezing apparatus for such a purpose as shown in FIG. 5, an endless steel belt 1 formed of a single stainless steel sheet having a smooth flat surface is extended between a driving pulley 3 and a tension pulley 2 disposed at the delivery station 11 and at the feed station 10 of the freezing apparatus, respectively. The driving pulley 3 is driven by a variable-speed motor at an optional speed to regulate the freezing duration, while the tension pulley 2 applies a fixed tension to the endless steel belt 1. A brine tank 4 is disposed under the upper run of the endless steel belt 1 in contact with the inner surface of the upper run. Articles 5 to be frozen are fed onto the endless steel belt 1. A blowing device comprising a finned chilling coil unit 6 is disposed above the endless steel belt 1. A duct 8 forms a path for circulating chilly air through a freezing zone 12 defined by a heat-insulating tunnel 9. Chilly brine 13 chilled by a brine chiller, not shown, is supplied into the brine tank 4 through a brine supply pipe 14, and is returned through a brine return pipe 15 to the brine chiller to circulate the chilly brine through the brine tank 4. A refrigerant is supplied from an external refrigerator through a refrigerant supply pipe 16 into the finned chilling coil unit 6, and is returned through a refrigerant return pipe 17 to the refrigerator to circulate the refrigerant through the finned chilling coil unit 6.
In operation, articles 5 successively supplied from the feed station 10 onto the endless steel belt 1 are conveyed at a fixed conveying speed through the freezing zone 12. While being conveyed through the freezing zone 12, the articles 5 are frozen by the chilly endless steel belt 1 chilled by the brine 13 contained in the brine tank 4 in a so-called contact freezing mode. On the other hand, the upper portion of the article 5 is frozen by the chilly air chilled by the finned chilling coil unit 6 and blown through the duct 8 by the blower 7 so as to circulate through the heat-insulating tunnel 9. The articles 5 thus frozen are discharged from the heat-insulating tunnel 9 and are delivered to the next process.
Although the lower portion of the article is frozen quickly in a so-called contact freezing mode, since chilly air is blown against the upper portion of the article, the upper portion of the article is frozen slowly at a low freezing speed, and thereby the upper portion of the article is caused to dry and lose in weight deteriorating the quality of the frozen article. Furthermore, since the conventional freezing apparatus comprises two chilling systems for chilling the brine and the air to be blown into the freezing zone, two refrigerators are necessary, which increases the initial cost and the running cost.