GRADUATED RELEASE VALVE

An apparatus incrementally reduces pressure in a first volume in response to an increase in pressure in a second volume. A valve body defines a bore that houses a piston and supply and return passages that communicate with first and second ends of the bore, respectively. The valve body also defines a release passage that connects the bore with the first volume and an exhaust passage that connects the bore with atmosphere. An inlet valve opens when pressure in the second volume increases relative to pressure in the supply passage. An outlet valve opens when pressure in the second volume decreases relative to pressure in the return passage. The piston is biased in a closed position against the first end and defines a passageway through which the first and the second ends communicate. When pressure increases in the second volume, the inlet valve opens causing the first end to pressurize and move the piston to an open position in which the release and exhaust passages communicate. This al lows the first volume to vent gradually to atmosphere. As the pressure gradually equalizes between the first and second ends via the passageway, the piston returns to its closed position thereby discontinuing communication between the release and exhaust passages so that the first volume is cut off from atmosphere. When pressure decreases in the second volume, the outlet valve opens causing pressure to equalize between the supply and return passages via the passageway and to approximate the pressure in the second volume. Un aparato reduce la presion de manera creciente en un primer volumen en respuesta a un incremento en la presion en un segundo volumen. Un cuerpo de valvula define un orificio que aloja un piston y pasajes de suministro y retorno que se comunican con el primer y segundo extremos del orificio, respectivamente. El cuerpo de la valvula tambien define un pasaje de descarga que conecta el orificio con el primer volumen y un pasaje de exhaustacion que conecta el orificio con la atmosfera. Una valvula de entrada se abre cuando la presion en el segundo volumen se incrementa en relacion a la presion en el pasaje de suministro. Una valvula de salida se abre cuando la presion en el segundo volumen disminuye en relacion a la presion en el pasaje de retorno. El piston es desviado en una posicion cerrada contra el primer extremo y define un pasaje a traves del cual el primer y segundo extremos se comunican. Cuando la presion se incrementa en el segundo volumen, la valvula