Center camshaft scroll pump

Abstract

A scroll pump includes a first scroll member having a first involute, a second scroll member scroll member having a second involute, and a camshaft rotatably connected to the first scroll member and to the second scroll member. A link is pivotably connected to the first scroll member and the second scroll member. The first and second scroll members cooperate to define a working volume wherein a working fluid is pressurized during operation of the scroll pump. The second scroll member is configured to equalize pressure across first and second opposed surfaces of an end plate thereof. The second scroll member includes a piston and cavity configured to bias the second scroll member toward the first scroll member in response to pressure across the first and second opposed surfaces of the end plate of the second scroll member.

1 . A scroll pump comprising:
 a first scroll member, the first scroll member comprising a first end plate and a first involute extending in an axial direction from a first side of the first end plate;   a second scroll member engaged with the first scroll member, the second scroll member comprising a second end plate and a second involute extending in an axial direction from a first side of the second end plate, wherein the first involute is interleaved with the second involute;   a link pivotably connected to the first scroll member and pivotably connected to the second scroll member, and   a camshaft having a first shaft portion having a first axis of rotation, the first shaft portion rotatably connected to the first scroll member, the camshaft further having a second shaft portion connected to the first shaft portion, the second shaft portion having a second axis of rotation parallel to and radially offset from the first axis of rotation, the second shaft portion rotatably connected to the second scroll member,   wherein rotation of the camshaft causes the second scroll member to travel in an orbital path with respect to the first scroll member, thereby causing the second involute to travel in an orbital path with respect to the first involute.   
     
     
         2 . The scroll pump of  claim 1  wherein:
 the first scroll member comprises a first pivot point; 
 the second scroll comprises a second pivot point; 
 a first portion of the link is pivotably connected to the first pivot point; and 
 a second portion of the link is pivotably connected to the second pivot point. 
 
     
     
         3 . The scroll pump of  claim 2  wherein the link substantially precludes rotation of the first scroll member with respect to the second scroll member. 
     
     
         4 . The scroll pump of  claim 3  wherein the first pivot point is located radially outward of the first involute. 
     
     
         5 . The scroll pump of  claim 3  wherein the second pivot point is located radially outward of the second involute. 
     
     
         6 . The scroll pump of  claim 3  further comprising a motor connected to and configured to rotate the first shaft portion of the camshaft. 
     
     
         7 . The scroll pump of  claim 1  wherein the first scroll member defines a first bearing pocket configured to receive from a second side of the first end plate opposite the first side of the first end plate, and not from the first side of the first end plate a first bearing configured to receive the first shaft portion of the camshaft in rotating engagement therewith. 
     
     
         8 . The scroll pump of  claim 1  wherein the first involute is in sealed engagement with the second end plate and the second involute is in sealed engagement with the first end plate. 
     
     
         9 . The scroll pump of  claim 6  further comprising a first tip seal in sealing engagement with a free axial end of the first involute and with the second end plate. 
     
     
         10 . The scroll pump of  claim 9  further comprising a second tip seal in sealing engagement with a free axial end of the second involute and with the first end plate. 
     
     
         11 . A scroll pump comprising:
 a first scroll member, the first scroll member comprising a first end plate and a first involute extending in an axial direction from a first side of the first end plate;   a second scroll member engaged with the first scroll member, the second scroll member comprising a second end plate and a second involute extending in an axial direction from a first side of the second end plate, wherein:
 the first involute is interleaved with the second involute, 
 rotation of the camshaft causes the second scroll member to travel in an orbital path with respect to the first scroll member, thereby causing the second involute to travel in an orbital path with respect to the first involute, 
 the second end plate has a first side and second side opposite the first side, 
 the second side of the second end plate defines a cavity having a sidewall, and 
 the second end plate defines a vent hole extending therethrough from the first side thereof to the second side thereof so that the cavity is in fluid communication with a working volume defined by cooperation of the first involute and the second involute, 
   the scroll pump further comprising a piston received within and in sealed engagement with the sidewall of the cavity,   wherein the piston axially fixed to the second shaft portion of the camshaft.   
     
     
         12 . The scroll pump of  claim 11  wherein the first side of the second end plate defines a first exposed surface area facing the first end plate and wherein the second side of the second end plate defines a second exposed surface area within the cavity. 
     
     
         13 . The scroll pump of  claim 12  wherein the second exposed surface area is greater than the first exposed surface area. 
     
     
         14 . The scroll pump of  claim 13  wherein the second scroll member floats axially with respect to the first scroll member and the camshaft. 
     
     
         15 . The scroll pump of  claim 14  wherein fluid pressure within the working volume and the cavity exerts a net axial force on the second end plate and wherein the net axial force biases the second end plate axially toward the first end plate. 
     
     
         16 . The scroll pump of  claim 15  wherein a first face of the piston facing the second end plate is exposed to the fluid pressure and not a second face of the piston opposite the first face is not exposed to the fluid pressure. 
     
     
         17 . The scroll pump of  claim 15  wherein the piston is sealingly enclosed within the cavity, and wherein the piston defines a second vent hole. 
     
     
         18 . The scroll pump of  claim 17  wherein a first face of the piston facing the second end plate and a second face of the piston opposite the first face are exposed to the fluid pressure. 
     
     
         19 . The scroll pump of  claim 11  further comprising a biasing spring configured to bias the second scroll member toward the first scroll member. 
     
     
         20 . The scroll pump of  claim 19  further comprising a first tip seal disposed between the first scroll and the second end plate and a second tip seal disposed between the second scroll and the first end plate. 
     
     
         21 . The scroll pump of  claim 20  wherein the biasing spring is configured to preload the second scroll member against the fixed scroll member to sealingly engage the first tip seal with the second end plate and sealingly engage the second tip seal with the first end plate. 
     
     
         22 . The scroll pump of  claim 19  wherein the biasing spring is disposed between the moving scroll member and the piston.