Patent ID: 7377848
Filing Date: 2008-05-27
Classification: B60H

Abstract:
1. A variable air circulation system for an off-highway vehicle having a cab body, a generally dust-tight operator's enclosure and work station within said cab body, and a cab door pivotally mounted on said cab body and adapted to open and close said operator's enclosure to permit ingress thereto and egress therefrom, said circulation system comprising: a distribution plenum for distributing a combination of fresh air and recirculated air into said operator's enclosure; a heating and air conditioning core housing; a fresh air inlet port through said cab body; an air flow duct between said plenum and said fresh air inlet port, said core housing in said air flow duct; a fresh air filter adjacent said fresh air inlet port, arranged such that air passing through said fresh air inlet port also passes through said filter; a recirculation port between said operator's enclosure and said air flow duct; a recirculation valve with a variable closure mechanism in said recirculation port controlling the amount of air flow through said recirculation port; a recirculation blower in air flow communication with said plenum and said core housing, said recirculation blower, core housing, recirculation port, fresh air inlet port and air filter arranged such that said recirculation blower causes recirculated air from within said operator's enclosure to flow through said recirculation valve and recirculation port and fresh air from outside the cab to flow through said fresh air inlet port and air filter along said air flow duct where the fresh air mixes with the recirculated air, then through said core housing into said plenum and thence into said operator's enclosure; a pressurizer blower in said air flow duct to increase the flow of air into said operator's enclosure; a control device connected to said recirculation valve and a sensor, said sensor causing said recirculation valve to fully open when said sensor senses that said vehicle has been put into a rest, yet operative condition signaling that the operator is about to leave said operator's enclosure; said control device also connected to said recirculation blower such that said recirculation blower is inactivated when said cab door is opened, and activated when said cab door is closed, whereby closing said cab door creates an air pressure pulse within the operator's enclosure, causing a reverse air flow through said air filter; and a time delay device to delay the time period between closure of said cab door and turning on of said recirculation blower.