Air return bulkhead

Details Air return bulkhead Air return bulkhead

2003-09-29

2004-12-07

Joyce, Harold (Department: 3749)

Freight accommodation on freight carrier

Load bracing means

Panel or frame, wall-to-wall

C062S239000, C062S263000, C062S297000, C410S121000, C454S118000

Reexamination Certificate

active

06827534

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to air return bulkheads for trailers for insuring proper flow of refrigerated air therein, and more specifically to universal-mount air return bulkheads which may be rapidly modified to fit on different trailer wails with differently-sized makes and models of refrigeration units thereon.
DESCRIPTION OF THE PRIOR ART
Refrigerated trailers are commonly used to transport perishable cargo on roadways in order to distribute the cargo to consumers in a fresh condition. These refrigerated trailers are specially designed for effective cooling of the cargo. The refrigeration unit for the trailer is generally mounted on the front wall of the trailer with a portion protruding into the interior of the trailer. The refrigerator inlet is located on the lower portion of the refrigerator adjacent the trailer interior front wall, and the refrigerator outlet is located on the top portion of the refrigerator near the trailer ceiling. As a result, warmer air is pulled from the trailer front wall, cooled, and blown along the ceiling of the trailer toward the trailer rear wall. The cargo is stacked on the trailer floor so that it is spaced from the trailer ceiling and the walls of the trailer. The floor of the trailer may be a false floor with a space located beneath, or as illustrated by the drawings in U.S. Pat. No. 2,923,384 to Black, the trailer floor may comprise a series of rails, ridges, or similar raised structures with lengths oriented from the front of the trailer to the rear of the trailer. In either case, the floor supports the cargo but allows refrigerated air to flow rearward along the trailer ceiling, along the trailer rear wall, and beneath the cargo and toward the front of the trailer. The refrigerator inlet then pulls the air in so that it may be recooled and again ejected rearwardly along the trailer ceiling. This cooling methodology allows a steady recirculating flow of refrigerated air to surround the entirety of the cargo, thereby keeping it at a cold temperature.
However, it has been found that cargo can sometimes shift during transport and slide against the front or rear wall of the trailer to block the circulating air. To prevent this problem, a bulkhead including a series of ribs or ridges thereon is frequently mounted to the front wall below the refrigerator inlet. This bulkhead, which is often called a “lattice-type” air return bulkhead, preserves the passage of air to the refrigerator inlet along the front wall even if cargo shift against it. The spacing between the ridges is such that cargo cannot fit therein, thereby preventing shifting cargo from moving between or behind the ridges and obstructing the circulation of air. The lattice type air return bulkhead may even extend over the refrigerator and toward the trailer ceiling to protect the refrigerator from damage from shifting cargo. One lattice-style air return bulkhead sold by Donovan Enterprises (LaGrange, Ga.) includes a series of vertically-oriented beams mounted to the trailer front wall below and adjacent to the refrigerator. A number of spaced horizontally-oriented slats are mounted to the beams to form a web-like slat framework spaced from the front wall of the trailer. Air can thereby flow from the floor between the beams and into the refrigerator inlet. The slats prevent cargo from shifting between the beams and blocking air flow. A similar lattice-style air return bulkhead is sold by Aero Industries (Indianapolis, Ind.).
However, when some types of lattice-style bulkheads are used, there is a possibility that cargo adjacent the refrigerator can shift so that spaces between the cargo provide an air passage between the bottom and top of the refrigerator. Air exiting the refrigerator outlet near the ceiling of the trailer can then be pulled directly downward toward the front wall of the trailer, through the lattice of the bulkhead, and back into the refrigerator inlet, rather than circulating through the trailer by flowing along the trailer ceiling towards the trailer's rear wall. This phenomenon, known as “short cycling” sends freshly cooled air into the refrigerator inlet and causes the thermostat in the refrigerator inlet to misread the air temperature in the trailer. The refrigerator then shuts down prematurely, resulting in product thawing and unsafe temperatures for foodstuffs.
To reduce the problem of short cycling, much of the trucking industry has been switching to “solid-style” or “false wall” air return bulkheads, which provide a solid, continuous wall spaced a short distance from the front wall of the trailer and surrounding the refrigerator inlet. The false wall air return bulkhead is opened near the floor of the trailer to allow air to flow from the trailer floor, behind the bulkhead wall, and into the refrigerator inlet. Because the false wall air return bulkhead provides a barrier between the refrigerator inlet and outlet and an effective refrigerator inlet near the trailer floor, the air exiting from the refrigerator cannot re-enter the refrigerator inlet unless it circulates throughout the mailer first. As a result, the false wall air return bulkheads work quite well in preventing short cycling. A summary of prior art false wall air return bulkheads follows.
U.S. Pat. No. 3,206,946 to Lindersmith et al. illustrates a false wall air return bulkhead which includes two parallel panels connected in spaced relation by a number of support beams. One panel (the “wall panel”) is attached to the trailer front wall so that the other panel (the “floating panel”) is maintained in spaced relation from the trailer front wall. Warm air from the floor passes between the panels to reach the refrigerator inlet. A series of vertically oriented, generally sinusoidal indentations or flutes are included in the floating panel to enhance heat transfer from the air passing between the panels to the air in the remainder of the trailer.
U.S. Pat. No. 5,427,237 to Kiefer et al. discloses a shipping crate for a refrigeration unit which may be converted to a false wall air return bulkhead. The resulting bulkhead utilizes side rib members which fit vertically on the trailer front wall on either side of the refrigerator, and central rib members which are placed at a diagonal on the trailer front wall beneath the refrigerator inlet. A planar floating panel is then attached to these rib members so that it is supported in spaced relation to the trailer front wall and so that it covers the lower portion of the refrigerator and the refrigerator inlet, thereby isolating the refrigerator inlet from the refrigerator outlet. Pallet stops in the form of C-shaped bumpers are then placed beneath the panel between the panel and the floor. These pallet stops prevent pallets or other cargo from shifting forward during transport, moving under the panel, and blocking air flow to the refrigerator inlet. The pallet stops also prevent pallets or other cargo from sliding beneath the panel and possibly catching and damaging the panel when the cargo is later lifted out of the trailer for removal.
U.S. Pat. No. 4,399,737 to Severson illustrates a false wall air return bulkhead having a floating panel spaced from the trailer front wall. Side support panels descend from the sides of the floating panel and extend into abutment with the trailer front wall near the trailer side walls. Corrugations or flutes are depressed into the floating panel between the panel and the trailer front wall. The top of the floating panel is placed in abutment with the refrigerator adjacent the refrigerator inlet. Supplementary panels or extension members are then attached to the top of the floating panel on both sides of the refrigerator to isolate the refrigerator inlet and prevent air exiting the refrigerator outlet from re-entering the inlet. These supplementary panels may include apertures at their sides to allow air adjacent the side walls of the trailer to flow inward towards the refrigerator inlet. The bulkhead is made in several different heights, and the supplementary panels can have several

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