Tandem servomotor partition

Claim 1

A tandem servomotor comprising: a housing having a front shell and a rear shell joined together to form a cavity therein; spacer means having a central web between an inner diameter section and an outer diameter section, said outer diameter section having a peripheral surface, said peripheral surface being located between the front shell and the rear shell, said central web dividing the cavity into a first portion and a second portion, said peripheral surface having a front face and a rear face, said spacer means having a first edge with a gripping surface attached to the front face of said peripheral surface, said peripheral surface having a narrow lip projecting from a stepped shoulder adjacent the rear face, said narrow lip having a series of slots substantially perpendicular to the rear face, said peripheral surface having a series of grooves extending along the interior thereof from adjacent said central web to said slots, said peripheral surface having a plurality of axial grooves extending to radial holes adjacent said first edge; a first flexible means having a frist external bead located between said gripping surface and the front shell and a first interior bead connected to a first wall, said first flexible means and said first wall dividing said first portion into a first vacuum chamber and a first power chamber; a second flexible means having an annular groove in a thickened second external bead adapted to receive the lip portion of said spacer means and a second internal bead connected to a second wall, said second flexible means and said second wall dividing said second portion into a second vacuum chamber and a second power chamber, said second external bead having an inwardly projecting rib at the end thereof adapted to abut the stepped portion of said spacer means; retaining means secured to said spacer means by surrounding said second external bead for holding said rib in said stepped portion, said retaining means having a portion engaging the rear shell to resiliently bias the first external bead between said gripping surface through the spacer means and the front shell; and actuation means connected to said first and second walls through which a vacuum is frelly communicated to said first and second vacuum chambers and vacuum and air under pressure selectively communicating to said second power chamber thence to said first power chamber by the axial grooves and radial holes in said spacer means, said actuation means moving in response to an input force permitting air under pressure to be communicated to the first and second power chambers establishing a pressure differential with the first and second vacuum chamber across the first and second walls, said pressure differential causing said first and second walls to move and drive an output member with a predetermined force, said air at atmospheric pressure in the second power chamber following a path around said rib through said slots and grooves along the interior of the peripheral surface of the spacer means into the second vacuum chamber with said rib away from the stepped portion of the spacer to negate the pressure differential across the second wall and reduce said output force to signal an internal malfunction of the servomotor upon initial assembly.