1. FIELD OF THE INVENTION
The present invention relates to fluid handling devices of the type which are capable of providing both pressure and vacuum and, more particularly, to bellows type mechanisms for aspirating fluid samples, such as blood, from a supply source into and through a sensing aperture for counting the individual items within the sample. The present apparatus specifically relates to and is employed with desk top mounted diluter equipment, for use in automated hematology to provide accurate, item counting.
2. DESCRIPTION OF THE PRIOR ART
Prior art includes the following U.S patents: U.S. Pat. No. 3,319,830 titled "Liquid Dispenser", which illustrates and describes liquid dispensing bellows means for mixing and dispensing beverages. The amount of liquid delivered to the mixing station of this apparatus is controlled by a rotatable selector disc having a plurality of variable length stop pins. The pins are designed to confront one end of movable slide members in order to control the amount of contraction of the bellows. The control disc is manually rotatable to select the desired type of beverage mix. The slides are cam actuated by means of a drive motor activated in response to operator selection.
U.S. Pat. No. 4,179,244 relates to a "Rotary Low Pressure Air Displacement Pump" and describes an assembly of multiple bellows radially disposed and activated by a singular rotary source of power, which imparts a cranking motion to connecting rods affixed to the bellows, which in turn supply individual conduits with equal or varying amounts of displaced air in accordance with the particular sizes of the individual bellows.
U.S. Pat. No. 4,305,211 relates to a "Vacuum Dryer" and describes a clothes dryer in which a drum is rotatably interconnected to multiple bellows, and to a swash plate which is disposed off axis and interconnects the drum with a plurality of bellows arranged between the drum and the angled swash plate. Rotation of the drum and swash plate provide vacuum inside the drum for withdrawing moisture, etc. from the drum and its contents.
U.S. Pat. Nos. 3,382,811; 4,060,178; 3,131,411; and 3,590,505 each describe a variety of bellows pumping mechanisms including cam actuation, wave actuation, and electrically and vacuum actuated pumping devices.
Prior art backwash systems for diluting apparatus include Coulter Electronics, Inc. U.S. Pat. Nos. 4,220,621; 4,148,859; and 3,976,429; 4,217,780; and British No. 2,095,403.
U.S. Pat. No. 4,631,483 titled "Particle Analyzing Apparatus and Method of Moving Particles in Suspension Through Such Apparatus", describes a particle analyzing apparatus having a fluid connection means for drawing a quantity of particles in suspension through a particle counting device including a source of vacuum. The source of vacuum is a bellows having an end, and a constant force means in the form of a freely movable weight connected to the end of the bellows means.
In operation of such prior art apparatus as that previously described, it is necessary to provide both pressure and vacuum means, since it is required to move fluids, both in volume as well as in predetermined, ordered segments, from a fluid sample supply to an examining station, and thereafter into a waste disposal receiving device. Most readily available apparatus for providing the foregoing features include compressors or vacuum pumps which are both costly and relatively noisy, requiring either vibration isolation and acoustic noise suppression, or long runs of fluid tubing so as to remotely separate the pumps from the examining hardware, thus using comparatively large volumes of fluids.
The present invention eliminates the need for these prior art units of hardware by providing a bellows pump and means for compressing and expanding the same in a selectively timed sequence depending upon the program requirements of the fluid testing and counting which is to be performed by the device. Additionally means is provided for preventing intersample contamination by the device which takes the sample from the sample container and places the sample in the segmenting and subsequently the counting device.