US 4,487,105 AGranted

Four position control valve for a pneumatically operated servomotor

AssigneeThe Bendix Corporation

InventorGregory K. Harrison

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Abstract

A retainer 226 for holding a control valve 656 of a servomotor 42 in a bore 90 of a hub 78. The hub 78 which is attached to a movable wall 56 has first 92 and second 96 passages that connect the bore to first 86 and second 88 chambers in the servomotor 42. The retainer 226 limits the movement of the control valve 656 in the bore 90 to establish a full release position whereby the pressure of the fluid in the first 86 and second 88 chambers equalize. In response to an input force, the control valve 656 moves to an actuation position where fluid under pressure is communicated to the second chamber 88 to create a pressure differential across the movable wall 56. The pressure differential acts on the movable wall 56 to develop an output force corresponding to the input force. On termination of the input force, the control valve 656 moves to the full release position where the fluid pressure equalization occurs. As equalization occurs, the retainer 226 cooperates with the hub 78 to allow the control valve 656 to move from the full release position to a fixed rest position adjacent the actuation position to reduce the valve travel required to reach the actuation position when an input force is applied to the control valve 656.

Claims8

Dependent claims

A retainer for holding a control valve of a servomotor in a bore of a hub, said hub being attached to a movable wall that separates the interior of the servomotor into a first chamber and a second chamber, said control valve engaging said retainer to establish a full release position whereby the first and second chambers are connected to each other to allow the fluid pressure therein to equalize, said control valve having an actuation position whereby the second chamber is connected to a source of fluid under pressure to develop a pressure differential across the movable wall and produce an output force corresponding to an input force applied to the control valve characterized by said retainer cooperating with said hub to permit said control valve to move from the full release position to a fixed rest position adjacent the actuation position to reduce the valve travel required to reach the actuation position in response to the input force;

said control valve having a plunger with a first end and a second end, said first end being connected to receive a reaction force corresponding to the output force;
an input member connected to said second end of said plunger;
a poppet located in said bore and having a first end secured to said hub and a second end free to move within said bore;
a first spring for urging said plunger toward the full release and rest positions;
a second spring for urging said free end of the poppet into engagement with said second end of said plunger during the full release and rest positions and with a seat on the hub on movement of the plunger to the actuation position;
said retainer having a cylindrical body fixed to the plunger adjacent said first end, said cylindrical body having a rib on the peripheral surface thereof that engages a first shoulder on the hub to limit the movement of the plunger in establishing said full release position;
and
a disc located on said plunger and urged into engagement with said cylindrical body by said first spring, said disc engaging a second shoulder on said hub on movement of the plunger to the fixed rest position to assure continued fluid communication between the first and second chambers in order that the fluid pressure therein remains equal.

5 more elements

A servomotor comprising:

a housing with a cavity therein;
a movable wall for dividing said cavity into a first chamber and a second chamber;
a hub connected to said movable wall having a bore therein, said hub having first and second passages for connecting the bore with the first and second chambers, respectively;
a first resilient member for urging the movable wall toward the second chamber;
a control valve located in said bore having a plunger and poppet member, said plunger and poppet having a full release position whereby the first and second chambers are connected to each other to equalize the fluid pressure therein, an actuation position where the second chamber is connected to a source of fluid under pressure through the bore and second passage, a static position where communication from the bore to both the first and second chambers is interrupted, and a fixed rest position adjacent the actuation position where said first and second chambers are connected;
an output member connected to the movable wall;
an input member responsive to an input force for moving said plunger from said fixed rest position to the actuation position to create a pressure differential across the movable wall between the fluid in the first and second chambers, said pressure differential acting on and moving the movable wall to overcoming said first resilient member to provide said output member with an output force, the resistance to movement of the output member providing a reaction force, said reaction force moving said plunger toward said poppet, said static position occuring when said reaction force is balanced with said input force, said reaction force moving the plunger and poppet member to the full release position on initial termination of said input force;
and
retainer means having a cylindrical member connected to said plunger, said cylindrical member engaging a first stop to limit the movement of the control valve by the reaction force to establish the full release position, said reaction force terminating as the fluid pressure in the first and second chambers equalizes as said first resilient member returns the movable wall toward the second chamber, said retainer means having a disc that surrounds said plunger and a second resilient member, said second resilient member urging said disc toward a fixed position with respect to said plunger, said source of fluid under pressure in said bore acting on said poppet and plunger by moving said plunger until said disc engages a second stop to establish said fixed rest position, said second resilient member opposing further movement of said plunger to maintain said fixed rest position in the absence of an input force.

6 more elements

Dependencies are inferred from the claim text.