Vibration dampening media in hydraulic power units

Abstract

A hydraulic power unit that uses a quantity of media within a cavity adjacent to and surrounding a hydraulic assembly in the housing of the hydraulic power unit to reduce the overall noise of the unit. Additionally, the cavity either seals the media from the moving parts of the hydraulic assembly or isolates the media from the moving parts of the hydraulic assembly to ensure damage to the hydraulic assembly does not result.

1 . A hydraulic power unit comprising:
 a housing having a hydraulic assembly with reciprocating pistons disposed therein;   at least a first cavity disposed within the housing adjacent the hydraulic assembly;   a quantity of media within the cavity to reduce noise produced by the hydraulic assembly;   wherein the cavity is enclosed by the housing, a tube that surrounds the hydraulic assembly and a swashplate of the hydraulic assembly so that the media is isolated from moving components of the hydraulic assembly.    
   
   
       2 . The hydraulic power unit of  claim 1  wherein the hydraulic assembly is actuated by an input shaft disposed through a cylinder block that houses the reciprocating pistons. 
   
   
       3 . The hydraulic power unit of  claim 1  wherein the hydraulic assembly is actuated by an electric motor. 
   
   
       4 . The hydraulic power unit of  claim 1  wherein the tube has at least one opening therein to provide fluid communication between oil of the hydraulic assembly and the media. 
   
   
       5 . The hydraulic power unit of  claim 1  further comprising a fill plug disposed through the housing and into the cavity to provide access to the cavity. 
   
   
       6 .- 7 . (canceled) 
   
   
       8 . The hydraulic power unit of  claim 1  wherein the quantity of media partially fills the first cavity. 
   
   
       9 . The hydraulic power unit of  claim 1  wherein the quantity of media completely fills the first cavity. 
   
   
       10 . The hydraulic power unit of  claim 1  wherein the media comprises a plurality of clean particles. 
   
   
       11 . The hydraulic power unit of  claim 1  wherein the media is selected from the group consisting of glass spheres, clean stone gravel, crushed hard rock, granite chips, sand, recycled glass and metal, polymer or ceramic particles. 
   
   
       12 . The hydraulic power unit of  claim 4  wherein the opening is of size and shape to isolate media from moving components of the hydraulic assembly. 
   
   
       13 . A hydraulic power unit comprising:
 a housing having a hydraulic assembly with reciprocating pistons disposed therein;   at least a first cavity disposed within the housing adjacent the hydraulic assembly;   a quantity of media within the cavity to reduce noise produced by the hydraulic assembly; and   a second cavity having at least one interconnected circuit board used to control the hydraulic power unit wherein a quantity of media is also disposed within the second cavity.