Abstract: A door and frame assembly useful for commercial coolers and heaters comprises a door frame having an upper horizontal member and opposing side members with an insulated door fitted in the door opening between the sides and with a discontinuous heating element extending at least along one, and preferably both, of the sides.

Abstract: A system for measuring the load on drive axles of tractors of over the road semitrailers and for determining load distribution on the front and drive axles of the tractor and the rear axles of the trailer. A calibratable air pressure gauge, placed in the cab of the tractor or truck, senses the pressure exerted by the trailer load on conventional air bags used to cushion the load on the drive axles. Approximate weight load may be determined by reading the pressure gauge. The gauge may be variably calibrated to accommodate the progression of settings for the fifth wheel assembly placement on an adjustment rack. Besides use on semitrailers, the system may be employed on straight or box trucks and trailers provided with air bags to cushion the axle load.

Abstract: A compressed air engine having specially designed cylinder heads and piston configurations in order to reduce friction and maximize the application of air from a pressurized air source. The disclosure includes a lubrication system whereby the mechanical parts receive oil via a lubrication arrangement including a conveyor chain continually bathed in oil.