Valve assembly with vent port between supply port and control port

A valve assembly which receives working fluid from a working fluid source and then communicates said working fluid to and from a working device that is switchable from a first mode of operation to a second mode of operation at a predetermined pressure of said working fluid, said valve assembly comprising:

• a housing with a housing control bore extending along an axis, a supply port in fluid communication with said housing control bore which receives said working fluid from said working fluid source, a control port in fluid communication with said housing control bore which communicates said working fluid to and from said working device, and a vent port in fluid communication with said housing control bore which selectively returns said working fluid to said working fluid source, wherein said vent port is located at an axial position of said housing that is between said supply port and said control port;
• a valve seat assembly including a valve seat body disposed coaxially within said housing control bore, said valve seat body defining:
• a control chamber in constant fluid communication with said control port;
• a vent path from said control port to said vent port;
• and
• a vent valve seat in said vent path;
• a supply passage which provides constant fluid communication from said supply port to said control chamber;
• and
• a vent valve member which is selectively seated and unseated with said vent valve seat such that said working fluid passes from said control chamber to said vent port through said vent path when said vent valve member is unseated with said vent valve seat and such that said working fluid is prevented from being communicated to said vent port when said vent valve member is seated with said vent valve seat;
• wherein said valve seat body further defines a pressure regulating valve seat in said vent path fluidly between said vent valve seat and said vent port, said valve assembly further comprising:
• a pressure regulating valve member which is selectively seated and unseated with said pressure regulating valve seat based on pressure within said control chamber when said vent valve member is unseated with said vent valve seat such that said working fluid passes from said control chamber to said vent port through said vent path when said pressure regulating valve member is unseated with said pressure regulating valve seat and such that said working fluid is prevented from being communicated to said vent port when said pressure regulating valve member is unseated with said pressure regulating valve seat.