US 3,938,350 A · Freeze tunnel

Abstract

Freezing apparatus in which food is quickly frozen comprising five coils, two joined in series to form a first set and two joined in series to form a second set, the exhaust of the two sets being delivered to the fifth coil in a pre-cooling chamber where food is introduced by a conveyor to the freeze tunnel. Each of the five coils is positioned in a separate chamber in the tunnel and thermal couple sensors deliver signals which are compared to a set-point signal in proportional controllers to control the flow of liquid nitrogen to each set of coils. Flow from the first and second sets of coils is vented to atmosphere and heater apparatus adjacent the fifth coil is energized when the temperature of nitrogen vapor discharged from the fifth coil is less than a predetermined value which results when formation of ice on the surface of the fifth coil reduces exchange of the heat between air circulated over the fifth coil and nitrogen vapor flowing therethrough.

Claims11

Dependent claims

Freezer apparatus comprising:

first and second heat exchanger means having inlets and outlets;
means to deliver coolant to the inlet of the first exchanger means;
a conduit connecting the outlet of the first exchanger means to the inlet of the second heat exchanger means;
an exhaust line connected to the outlet of the first exchanger means;
signal responsive valve means in said conduit and in said exhaust line;
means to heat said second heat exchanger mean;
sensor means positioned in heat exchange relation with coolant discharged from second heat exchanger;
signal generator means operably connected to said sensor means and to said signal responsive valve means and to said heater means, said signal generator means being adapted to generate signals to actuate said valve means such that flow of coolant is diverted from the first heat exchanger to the exhaust line and the heater means is energized when temperature of coolant exhausted from said second heat exchanger is less than a predetermined temperature.

5 more elements

Dependencies are inferred from the claim text.

Freeze tunnel

Life of this patent

Freeze tunnel

Life of this patent

Abstract

Claims11