Linear pump with sound attenuator

Abstract

A linear piston pump has a multi-cavity air intake providing improved sound attenuation characteristics. The air intake is formed between a cover mounted in spaced relation to a pump housing so as to define an air intake passage leading around the periphery of the cover to an outer cavity separated from an inner cavity by a partition. Flow orifices are formed in the partition as well as in the inner cavity for air to flow to the intake chamber. Intake air re-expands in the inner cavity to dissipate pulsations in the air flow from the rapidly action of the intake valve, and thereby reduces intake noise. A filter and air baffle filter retainer may also be included to further reduce intake noise.

1 . A linear pump, comprising an electro-magnetically driven piston reciprocating within a cylinder in communication with a multi-cavity air intake, the intake including a first cavity and a second cavity, the first cavity being in communication with ambient air and being in communication with the second cavity through a first orifice and the second cavity being in communication with a downstream section of the pump through a second orifice, wherein intake air re-expands in the second cavity before passing through the second orifice.  
   
   
       2 . The pump of  claim 1 , wherein the intake creates a first pressure drop through the first orifice and a second pressure drop through the second orifice.  
   
   
       3 . The pump of  claim 1 , wherein the second cavity is inward of the first cavity.  
   
   
       4 . The pump of  claim 1 , wherein at least the second cavity is defined by a pump housing.  
   
   
       5 . The pump of  claim 1 , further including partition defining the first orifice and sealing the second cavity from the first cavity.  
   
   
       6 . The pump of  claim 1 , wherein the first orifice is offset from the second orifice so that the intake air turns directions between the first and second orifices.  
   
   
       7 . The pump of  claim 6 , wherein there are a pair of first orifices and a pair of second orifices.  
   
   
       8 . The pump of  claim 1 , further including a cover mounted to a pump housing over the first cavity and defining an air passage from ambient to the first cavity between the cover and the pump housing.  
   
   
       9 . The pump of  claim 8 , wherein hold offs keep the cover spaced from the pump housing.  
   
   
       10 . The pump of  claim 8 , wherein the air passage extends along the periphery of the cover.  
   
   
       11 . The pump of  claim 1 , wherein the intake includes a filter member.  
   
   
       12 . The pump of  claim 11 , wherein the filter member is disposed in the first cavity.  
   
   
       13 . The pump of  claim 11 , wherein the filter member is held by a retainer having a plurality of spaced apart riser elements spacing the filter member from a base surface of the retainer such that intake air can pass from the first cavity through the filter member around the riser elements and into the second cavity through an orifice in the retainer and the first orifice.  
   
   
       14 . The pump of  claim 1 , wherein the pump includes a pump housing enclosing the piston and cylinder arrangement.  
   
   
       15 . The pump of  claim 1 , wherein the second orifice is spaced from the cylinder.  
   
   
       16 . The pump of  claim 1 , wherein the cylinder and an intake chamber are spaced from the intake.  
   
   
       17 . A linear pump having a pump housing containing an electro-magnetically driven piston reciprocating within a cylinder in communication with a multi-cavity air intake, the intake including: 
 a cover mounted to the pump housing to define an intake air passage;    an inner cavity defined in part by the pump housing having an inner orifice in communication with an intake chamber of the pump; and    an outer cavity defined between the cover and a partition mounted to the pump housing to seal off the inner cavity, the outer cavity being in communication with ambient air through the intake air passage and in communication with the inner cavity through an outer orifice in the partition which allows intake air to re-expand in the inner cavity before passing through the inner orifice.    
   
   
       18 . The pump of  claim 17 , wherein the outer orifice is offset from the inner orifice so that the intake air flow turns approximately 90 degrees between the outer and inner orifices.  
   
   
       19 . The pump of  claim 18 , wherein there are a pair of inner orifices and a pair of outer orifices  
   
   
       20 . The pump of  claim 17 , wherein the intake air passage extends along the periphery of the cover.  
   
   
       21 . The pump of  claim 17 , wherein the intake further includes a filter.  
   
   
       22 . The pump of  claim 21 , wherein the filter member is disposed in a retainer having a plurality of spaced apart riser elements spacing the filter member from a base surface of the retainer defining the outer orifice such that intake air can pass between the inner and outer cavities through the filter and around the riser elements.