Tandem vacuum booster with extensible bellow air sleeve

Abstract

A tandem vacuum booster includes an internal air passage connection between primary and secondary high pressure chambers of the booster, and extending through a primary low pressure chamber of the booster. The internal air passage connection includes a tubular collar extending longitudinally from a divider separating the secondary high pressure and primary low pressure chambers, and an extensible air tube extending through and from a primary diaphragm of the booster, with the primary diaphragm defining the boundary between the primary high and low pressure chambers. The collar includes an outer surface thereof adapted for receiving a distal end of the extensible air tube extending over a portion of the outer surface of the collar. The distal ends of the collar and the air tube include elements for retaining and/or sealing the distal end of the extensible tube against the outer surface of the collar. The booster also includes a primary diaphragm support disposed for contacting a front surface of the primary diaphragm, and having a hole therein for passage therethrough of the extensible air tube, with the air tube including a locking bead on an outer surface thereof for engaging the primary diaphragm support around the hole, to thereby restrain movement of the extensible air tube relative to the diaphragm support and preclude chafing of the air tube that could occur if the air tube were not retained in the hole of the primary diaphragm support.

We claim:  
     
         1 . A tandem vacuum booster comprising: 
 a housing defining a longitudinal axis of the booster, the housing having a divider therein separating the interior of the housing into a primary and a secondary chamber and providing sliding support for a booster piston;    a booster piston supported by the divider for movement along the longitudinal axis;    a secondary diaphragm attached at an inner periphery thereof to the booster piston in the secondary chamber of the housing and extending radially outward to an outer periphery thereof attached to the housing, to thereby define a secondary low pressure chamber bounded by the housing, the piston and the secondary diaphragm, and further defining a secondary high pressure chamber bounded by the piston, the secondary diaphragm, and a front face of the divider;    a primary diaphragm attached at an inner periphery thereof to the booster piston in the primary chamber of the housing and extending radially outward to an outer periphery thereof attached to the housing, to define a primary low pressure chamber bounded by a rear face of the divider, the housing, the piston and the primary diaphragm, and further defining a primary high pressure chamber bounded by the housing, the piston, and the primary diaphragm;    the divider having a tubular collar extending longitudinally therefrom into the primary low pressure chamber, the collar defining a air passage conduit through the divider and an outer surface of the collar for receiving a sealing surface of an extensible air tube; and    an extensible air tube defining an air passage conduit through and extending longitudinally from the primary diaphragm to a distal end of the extensible air tube extending over and providing sealing attachment to the outer surface of the collar;    the tubular collar and extensible air tube thereby forming a longitudinally extensible air passage conduit passing through the primary low pressure chamber and providing air passage communication between the primary and secondary high pressure chambers of the booster.    
     
     
         2 . The booster of  claim 1  wherein the extensible air tube includes one or more annular convolutions disposed between the primary diaphragm and the distal end of the extensible air tube.  
     
     
         3 . The booster of  claim 2  wherein the air tube includes two or more annular convolutions forming a bellows.  
     
     
         4 . The booster of  claim 1  wherein the outer surface of the collar extending from the divider includes a radially enlarged section thereof for retaining the distal end of the extensible air tube.  
     
     
         5 . The booster of  claim 4  wherein the distal end of the extensible air tube defines a retaining lip for engaging the radially enlarged section of the outer surface of the collar.  
     
     
         6 . The booster of  claim 1  wherein the distal end of the extensible air tube includes a thickened annular wall section having a generally triangular cross section with one vertex of the triangular cross section connected to the extensible air tube, a second vertex of the triangular cross section forming an end of the extensible air tube, and the third vertex of the triangular cross section forming a contact surface adapted for receiving the outer surface of the collar.  
     
     
         7 . The booster of  claim 6  wherein the distal end of the extensible air tube further includes a sealing lip configured for pressure biased sealing against the outer surface of the collar by air pressure within the extensible air tube.  
     
     
         8 . The booster of  claim 7  wherein the distal end of the collar is flared to form a bell-mouth shape for retaining the sealing lip in contact with the outer surface of the collar.  
     
     
         9 . The booster of  claim 8  where the sealing lip is attached at one end thereof to an inner surface of the distal end of the extensible air tube and extends from the inner surface of the distal end of the extensible air tube in a direction toward the primary diaphragm.  
     
     
         10 . The booster of  claim 1  further comprising a primary diaphragm support attached to the piston in the primary low pressure chamber adjacent the inner periphery of the primary diaphragm and extending radially outward from the piston along a portion of a front surface of the primary diaphragm; 
 the primary diaphragm support having a hole therethrough for passage of the extensible air tube; and  
 the extensible air tube having a locking bead extending therefrom for longitudinally restraining the extensible air tube within the hole of the primary diaphragm support against longitudinal movement relative to the primary diaphragm support.  
 
     
     
         11 . A tandem vacuum booster comprising: 
 a housing defining a longitudinal axis of the booster, the housing having a divider therein separating the interior of the housing into a primary and a secondary chamber and providing sliding support for a booster piston;    a booster piston supported by the divider for movement along the longitudinal axis;    a secondary diaphragm attached at an inner periphery thereof to the booster piston in the secondary chamber of the housing and extending radially outward to an outer periphery thereof attached to the housing, to thereby define a secondary low pressure chamber bounded by the housing, the piston and the secondary diaphragm, and further defining a secondary high pressure chamber bounded by the piston, the secondary diaphragm, and a front face of the divider;    a primary diaphragm attached at an inner periphery thereof to the booster piston in the primary chamber of the housing and extending radially outward to an outer periphery thereof attached to the housing, to define a primary low pressure chamber bounded by a rear face of the divider, the housing, the piston and the primary diaphragm, and further defining a primary high pressure chamber bounded by the housing, the piston, the primary diaphragm;    the divider having a tubular collar extending longitudinally therefrom into the primary low pressure chamber, the collar defining a air passage conduit through the divider and a surface of the collar for receiving a sealing surface of an extensible air tube;    an extensible air tube defining an air passage conduit through and extending longitudinally from the primary diaphragm to a distal end of the extensible air tube providing sealing attachment to the surface of the collar;    a primary diaphragm support attached to the piston in the primary low pressure chamber adjacent the inner periphery of the primary diaphragm and extending radially outward from the piston along a portion of a front surface of the primary diaphragm;    the primary diaphragm support having a hole therethrough for passage of the extensible air tube; and    the extensible air tube having a locking bead extending therefrom for longitudinally restraining the extensible air tube within the hole of the primary diaphragm support against longitudinal movement relative to the primary diaphragm support.    the tubular collar and extensible air tube thereby forming a longitudinally extensible air passage conduit passing through the primary low pressure chamber and providing fluid communication between the primary and secondary high pressure chambers of the booster.    
     
     
         12 . The booster of  claim 11  wherein the extensible air tube includes one or more annular convolutions disposed between the primary diaphragm and the distal end of the extensible air tube.  
     
     
         13 . The booster of  claim 12  wherein the air tube includes two or more annular convolutions forming a bellows.  
     
     
         14 . The booster of  claim 11  wherein the collar extending from the divider defines an outer surface of the collar for receiving an inner surface of the distal end of the extensible air tube.  
     
     
         15 . The booster of  claim 14  wherein the outer surface of the collar further includes a radially enlarged section thereof for retaining the distal end of the extensible air tube.  
     
     
         16 . The booster of  claim 15  wherein the distal end of the extensible air tube defines a retaining lip for engaging the radially enlarged section of the outer surface of the collar.  
     
     
         17 . The booster of  claim 14  wherein the distal end of the extensible air tube includes a thickened annular wall section having a generally triangular cross section with one vertex of the triangular cross section connected to the extensible air tube, a second vertex of the triangular cross section forming an end of the extensible air tube, and the third vertex of the triangular cross section forming a contact surface adapted for receiving the outer surface of the collar.  
     
     
         18 . The booster of  claim 17  wherein the distal end of the extensible air tube further includes a sealing lip configured for pressure biased sealing against the outer surface of the collar by air pressure within the extensible air tube.  
     
     
         19 . The booster of  claim 18  wherein the distal end of the collar is flared to form a bell-mouth shape for retaining the sealing lip in contact with the outer surface of the collar.  
     
     
         20 . The booster of  claim 19  where the sealing lip is attached at one end thereof to an inner surface of the distal end of the extensible air tube and extends from the inner surface of the distal end of the extensible air tube in a direction toward the primary diaphragm.