Abstract: A method and apparatus for low NOX combustion of natural gas in a compact steam boiler having output steam delivery controlled by predetermined outlet steam pressure. The compact boiler employs a small high heat release combustor discharging into a forced draft convective heat exchange section. In operation, the compact boiler is completely and automatically self-operating, employing flue gas recirculation (FGR) wherein the FGR is admitted into the burner combustion air through a valve controlled by boiler flue gas NOX content. A novel bell mouthed flue gas scoop is utilized in the boiler stack upstream of the NOX sensor. In an alternate combustion chamber design, a cylindrical water wall coil surrounds the combustion process, increasing boiler efficiency through the inherent large temperature difference between the coil and the combustion in process, along with reducing the combustion temperature and further reducing the NOX content of combustion products.

Abstract: An improved transponder for use in identifying an controlling vehicles wherein transponders mounted on vehicles respond to signals from a fixed location interrogator providing information relative to the vehicle or other data as required. The transponder disclosed in particular utilizes an improved method of providing frequency shift keyed (FSK) signals in response to a trigger or command signal received from a ground mounted loop or antenna. As disclosed, the transponder of the invention generates FSK signals through programming multiple microprocessor loops of predetermined duration, each loop providing microprocessor highs and lows for transmission to the interrogating station. Utilization of the inherently accurate microprocessor cycle time to generate distinct FSK signals avoids problems with ordinarily used analog frequency generating devices.

Abstract: Method and apparatus for reducing the NOX levels in stack emissions of compact boilers and fluid heaters through selective injection of exhaust flue gases into the combustion process. Flue gas injection into the primary and secondary air of the burner along with flue gas injection directly into the combustion process is utilized. Injection of generated steam obtained from various components of a compact boiler, selectively injected into the combustion process is also provided.

Abstract: A stabilizing arm for use in power operated doors in mass transit vehicles. Doors are of the type where a door panel is moved out of an opening in the car side wall to an opened position outside the car side wall. Stabilization is achieved by moving a rotating arm out of the side wall and capturing the panel in its opened position, thereby minimizing possible hazards in passenger passing through the car opening and damage to the doors either by passengers or others. Operation of the arm is sequenced in the door opening cycle.

Abstract: A power door operator for multi-passenger mass transit vehicles, typically buses, features electric actuation of dual swinging doors. A manual activator having an ergonometrically correct actuating plunger, for emergency door opening, operates a sleeved clutch. Fixed to the sleeve clutch is a drive bar with arms having individually adjustable lengths. The drive arms actuate outboard door shaft levers on individual door leaf through door drive rods intermediate the door arms and drive arms. Each rod incorporates spherical rod ends. The drive arms also actuate limit switches establishing door opened and door closed circuitry for energizing the electric drive system. The adjustable length clutch door drive arms provide a convenient device for controlling door leaf closing sequence and residual or door holding force when the doors are in a closed position.

Abstract: A system for detecting objects in the path of a power operated, movable door operating in a mass transit vehicle, which would obstruct door closing. The system also includes an integral method for detection of a "free wheeling" door occasioned by failure of the door mechanical drive. Method and apparatus disclosed utilize door handle locating devices such as electrical switches located at predetermined points along the door closure track. A combination of door locations along the closure track centrally define positions signaling either door linkage failure with attendant "free wheeling" door, and/or door obstruction, in each case, the system disclosed prevents train motion until the improper door condition is remedied. The combination provides a reduction in passenger hazards occasioned by train movement with defective operator linkage and/or door obstruction due to trapped passengers or other impediments to door closure.