Abstract:
A peristaltic pump having a molded flow channel contained on an elastomeric sheet that is bonded or mechanically attached to a rigid substrate. The pump head rollers are mounted radially from the axis of rotation of the pump motor and compress the elastomeric flow channels against the rigid substrate.

Description:
This application is a continuation of U.S. patent application Ser. No. 09/437,392, filed Nov. 10, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to peristaltic pumps and more specifically to peristaltic pumps used in ophthalmic surgical equipment. 
     Most prior art peristaltic pumps work by compressing or squeezing a length of flexible tubing (sometimes between a fixed race) using a rotating roller head. As the roller head rotates, the rollers pinch off a portion of the tubing and push any fluid trapped in the tubing between the rollers in the direction of rotation. Peristaltic pumps are widely used in medical applications because of their predictable, constant flow properties. These prior art systems, however, typically require manual connection of the pump tube segment around the rotating roller head. 
     Prior art peristaltic pumps using rotating roller heads also typically impart unwanted pressure pulsations. Several pulsation damping devices have been developed to address this problem (see e.g., U.S. Pat. No. 4,921,477 (Davis)). 
     Accordingly, a need continues to exist for a peristaltic pump that reduces pressure pulsations and that is simpler and more economical to manufacture and use. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention improves upon prior art peristaltic pumps by providing a peristaltic pump having a molded flow channel contained on an elastomeric sheet that is bonded or mechanically attached to a rigid substrate. The pump head rollers are mounted radially from the axis of rotation of the pump motor and compress the elastomeric flow channels against the rigid substrate. 
     One objective of the present invention is to provide a peristaltic pump that uses molded elastomeric flow channels. 
     Another objective of the present invention is to provide a peristaltic pump having radially oriented pump rollers. 
     Yet another objective of the present invention is to provide a peristaltic pump having pump rollers that compress elastomeric flow channels against a rigid substrate. 
     These and other advantages and objectives of the present invention will become apparent from the detailed description, drawings and claims that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic top plan view of a first embodiment of the present invention, with the motor and roller head removed for clarity. 
     FIG. 2 is a schematic side elevational view of a first embodiment of the present invention, with the motor and roller head removed for clarity. 
     FIG. 3 is a cross-sectional view of the first embodiment of the present invention taken at line  3 — 3  in FIG.  1 . 
     FIG. 4 is a schematic top plan view of a second embodiment of the present invention, with the motor and roller head removed for clarity. 
     FIG. 5 is a schematic side elevational view of a second embodiment of the present invention, with the motor and roller head removed for clarity. 
     FIG. 6 is a schematic front elevational view of a second embodiment of the present invention, with the motor and roller head removed for clarity. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As best seen in FIGS. 1,  2  and  3 , in a first embodiment of the present invention, pump  10  of the present invention generally includes pump motor  12 , roller head  14 , containing one or more rollers  16  and cassette  18  having elastomeric sheet  20  applied to the exterior of relatively rigid body or substrate  22 . Pump motor  12  preferably is a stepper or D.C. servo motor. Roller head  14  is attached to shaft  24  of motor  12  so that motor  12  rotates roller head  14  in a plane generally normal or perpendicular to axis  25  of shaft  24 , and the longitudinal axes of rollers  16  are generally radial to the axis of shaft  24 . 
     Sheet  20  contains molded fluid channel  26  that is generally planar, arcuate in shape (within the plane) and having a radius approximating that of rollers  16  about shaft  24 . Fluid channel  26  fluidly connects ports  28  and  30 . Sheet  20  may be made of any suitably flexible, easily molded material such as silicone rubber or thermoplastic elastomer. Sheet  20  is attached or bonded to substrate  22  by any suitable technique such as adhesive, heat fusion or mechanical crimping. Substrate  22  preferably is made of a material that is rigid with respect to sheet  20 , such as a rigid thermoplastic, and may be made by any suitable method, such as machining or injection molding. 
     In use, cassette  18  is held in close proximity to roller head  14  so that rollers  16  compress channel  26  against substrate  22  as roller head  14  rotates. The longitudinal axes of the rollers are arranged so that roller  16  contact with channel  26  is generally parallel with the plane of channel  26 . Such an arrangement eliminates the need to loop a length of flexible tubing over the pump roller head and thus simplifies the loading of pump channel  26  against pump roller head  14 . Rollers  16  may be tapered along their axial length to accommodate the difference in path length traveled by the inner and outer sections of rollers  16  as roller head  14  rotates. Unwanted pressure pulsations could be minimized by providing channel transition regions  46  and  47  having internal cross-sections that taper from zero to the full cross-section of channel  26 . These regions minimize the abrupt change in displaced volume as rollers  16  transition on or off of channel  26 . 
     As best seen in FIGS. 4-6, in a second embodiment of the present invention, cassette  18 ′ may contain additional fluid channels that provide control of irrigation fluid as well as aspiration fluid. For example, cassette  18 ′ may contain aspiration inlet port  32  and aspiration outlet port  34  that are connected through channel  26 ′. Upstream of port  32 , cassette  18 ′ may contain pressure sensor  36 , which may be any of a variety of non-invasive pressure sensors such as those disclosed in U.S. Pat. No. 5,910,110 (Bastable) and U.S. Pat. No. 5,470,312 (Zanger, et al.), the entire contents of which being incorporated herein by reference. Cassette  18 ′ may also contain a vent pinch valve site  38  for allowing the venting of any vacuum from channel  26 ′. Irrigation fluid enters cassette  18 ′ through port  40  and exits cassette  18 ′ through port  42  and is controlled by valve or pinch valve site  44 , which may be actuated by a plunger (not shown). Vent  38  may be operated in a similar method. In addition, between port  40  and irrigation pinch valve site  44 , cassette  18 ′ may contain irrigation pressure interface  50 . Pressure interface  50  may be made from a thin molded membrane contained within elastomeric sheet  20 ′ over a fluid chamber (not shown) contained within substrate  22 ′. Such an interface allows detection of irrigation pressure in a non-invasive manner using a surface contact pressure transducer or calibrated load cell. 
     This description is given for purposes of illustration and explanation. It will be apparent to those skilled in the relevant art that modifications may be made to the invention as herein described without departing from its scope or spirit.