Abstract: A food freezing tunnel has an inner trough member and a roof member. In order to gain access to the interior of the tunnel, for example for purposes of cleaning the tunnel, the inner trough member is able to be raised and lowered. The tunnel has a spray header for liquid nitrogen and fans for circulating resulting cold nitrogen vapor. The tunnel has an inner trough member spaced from the outer trough member. The inner trough member has a floor extending underneath the upper run of a conveyor passing through the tunnel and has sides which prevent direct impingement of liquid nitrogen onto the outer trough member and which co-operate with the roof member to inhibit the passage of cold gas from within the trough member over the sides.

Abstract: A food freezing tunnel has a trough member and a roof member. In order to gain access to the interior of the tunnel, for example for purposes of cleaning the tunnel, the trough member is able to be raised and lowered. Jack means housed in the respective legs of the tunnel are driven by for example an electric motor to lower and raise the tunnel. The trough has counterweights. Typically the jack includes a rotary screw-threaded shaft which carry a nut connected to a chain which travels over pulleys and which is secured to the trough member.