Patent Publication Number: US-6220487-B1

Title: Dispensing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of United States Provisional Application Ser. No. 60/104,558 filed Oct. 16, 1998 for a Dispensing Apparatus (abandoned). 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to dispensing apparatus and more specifically to dispensing apparatus capable of metering predetermined amounts of a material with accuracy. 
     2. Description of Related Art 
     Conventional positive displacement pumps available today for high accuracy dispensing applications are either piston-type or rotary screw-type pumps. Both types find uses in specific applications. For example, U.S. Pat. No. 5,499,745 (1996) to Derian et al. discloses an apparatus for mixing and dispensing two chemically reactive materials. This apparatus includes a metering unit for dispensing two-part polymeric materials from a dispensing module attached to the end of the robot arm. The metering unit includes a piston located concentrically about a shaft of a dual actuating piston assembly to provide the two polymeric materials in a fixed ratio. A variable rate dispenser compensates for changes in robot velocity or viscosity changes. 
     U.S. Pat. No. 5,819,983 (1998) to White et al. discloses a liquid dispensing system with a sealing augering screw. The augering screw serves both a metering function and a valving function and is axially movable between a position in which fluid can flow and a sealing position in which liquid flow through the nozzle is substantially prevented. The screw has a curved contour between its threads and a plurality of thread-defining channels to allow liquid to fill more completely around the screw thereby to dispense more liquid with fewer screw turns than prior designs. 
     U.S. Pat. No. 5,927,560 (1999) to Lewis et al. discloses a dispensing pump that dispenses a two-part epoxy and includes a pumping chamber in communication with a nozzle by means of a three-way valve. The pumping chamber includes an outlet, an internal volume, a pair of spaced directional seals located away from the outlet, an open volume residing between the seals and an external port opening the open volume to atmosphere. A stepped plunger extends axially within the pumping chamber. A first portion is sized to be received and aligned through a first directional seal so the plunger can move the first portion toward the outlet to close off the internal volume at the second seal. The second plunger portion is relatively smaller and transfers cross-sectional dimension than the inside diameter of the second seal to cooperate with the port to promote fluid removal from the internal volume during initial filling and priming of the pumping chamber. Once filled and primed, the plunger causes positive volume displacement of liquid from the pumping chamber and out of the nozzle, with very good repeatability and high fluid flow rates, independent of material viscosity, and/or temperature or viscosity changes. For refilling, the plunger is retracted by a volume which corresponds to the volume of material refilled into the internal volume. 
     U.S. Pat. No. 5,957,343 (1999) to Cavallaro discloses a controllable liquid dispensing device with a selectively adjustable material control device and a sealing device with a dispensing device. The sealing device is in communication with a switching device to move the sealing device between a first position and a second position. The first position of the sealing device allows the material control device to draw a volume of material into the dispensing device. The second position of the sealing device allows the material control device to force the volume of material to dispense from the dispensing device. 
     The foregoing patents disclose a number of possible approaches to various dispensing devices. However, they are not the best choices for many high accuracy and high throughput applications. Many such applications use high viscosity abrasive fluids that further exacerbate the problem because the materials tend to wear and increase the force or torque needed to drive the system to dispense material. Screw-type pumps lack the accuracy or the throughput needed for today&#39;s production processes. Although piston pumps offer better volumetric accuracy, they lack any feedback capability and are also slow. Piston pumps further generally have a large size, are difficult to use and impose real restrictions on the end user. 
     SUMMARY 
     Therefore it is an object of this invention to provide a positive displacement dispensing pump that meets high volume production demands. 
     In accordance with one aspect of this invention, a dispensing pump comprises a sleeve, a valve, a piston and a control. The sleeve has first and second ends and first and second spaced apertures through a side thereof. The valve mounts for rotation internally at a first end of the sleeve with first and second ports for alignment with the first and second apertures in first and second angular positions of the valve, respectively. The piston mounts at the other end of the sleeve for longitudinal motion between a first position abutting the valve and a second position displaced from the valve. The control rotates the valve and displaces the piston thereby to dispense a material from one of the spaced apertures. 
     In accordance with another aspect of this invention, a dispensing pump includes a manifold having an input port for connection to a material source, an output port and first and second input and output passages wherein the input passages connect to the input port and the output passages connect to the output port. Each of first and second sleeve assemblies attach to communicate with one pair of the input and output passages; each sleeve assembly has a structure for displacing material. An operator interacts with the displacing structure for moving material from the material source through the input passages and input ports into the sleeve assemblies and for moving material from the sleeve assemblies through the output ports and output passages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The appended claims particularly point out and distinctly claim the subject matter of this invention. The various objects, advantages and novel features of this invention will be more fully apparent from a reading of the following detailed description in conjunction with the accompanying drawings in which like reference numerals refer to like parts, and in which: 
     FIG. 1 depicts portions of a dispensing pump constructed in accordance with this invention; 
     FIG. 2 is an exploded view of certain portions of the apparatus shown in FIG. 2; 
     FIG. 3 is a diagram that depicts certain portions of the pump shown in FIG. 1 including the portions of FIG. 2; 
     FIG. 4 depicts four states of operation of the apparatus shown in FIGS. 1 through 3; and 
     FIG. 5 is an exploded view of the system shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     FIG. 1 depicts a dispenser  10  that includes two sleeve assemblies including sleeves  11  and  12  attached to a manifold  13  with an input, or supply, port  14  and an output, or dispensing, port, not visible in FIG. 1 but extending oppositely from the input port  14 . Each of the sleeves contains a longitudinally displaceable piston. Sleeve  11  contains piston  15 ; sleeve  12 , a piston  16 . The remaining mechanism in FIG. 1 drives the pistons  15  and  16 , preferably in an alternating fashion and actuates valves such as a valve  17  shown in FIG.  2 . 
     Referring to FIG. 2, the valve  17  is mounted for rotation internally of the sleeve  12  at a first end or bottom of the sleeve  12  and includes angularly displaced ports shown as an input port  18  and an output port  19 . In an input position of the valve  17 , the input port  18  aligns with an input aperture  20  through the sleeve  12  that in turn communicates with an input passage  34  from a face  22  of the manifold  13  to the input port  14 . Similarly, output port  19  allows material to be dispensed when it aligns with an output aperture  23  through the sleeve  12  that in turn aligns with an output passage  34  that communicates with the output port from a bottom surface  25  of the manifold  13 . A mechanism, described later, contacts an actuator  26  to rotate the valve  17  to one of three positions namely, (1) an input position in which the input port  18  aligns with input aperture  20 ; (2) an output position in which the output port  19  aligns with output aperture  23 ; and (3) an intermediate or neutral position in which neither input port  18  or output port  19  aligns with either with input aperture  20  or output aperture  23 . 
     The piston  16  mounts at the other end of the sleeve  12  and extends through a sealed aperture  27  and travels longitudinally between an upper position and a lower position defined when an end  28  of the piston  16  abuts an upper end  29  of the valve  17 . The sealed aperture  27  prevents any material from escaping from the sleeve  11 . If the piston  16  is withdrawn while the input port  18  is aligned with the input aperture  20 , material displaces into the sleeve  12 . When the piston  16  moves downwardly and the output port  19  aligns with the output aperture  23 , material within the sleeve displaces from the sleeve  11 . The volume dispensed corresponds to the volume displaced by the piston  16  during its downward travel. 
     FIG. 3 depicts in schematic form the sleeve  12  with the piston  16  attached to one side of the manifold  13  with the sleeve  11  and piston  15  being shown in phantom as attaching to passages  21  and  24  corresponding to input passage  21  and output passage  24  in FIG. 2. A supply  30 , that normally is pressurized, includes a coupling  31  to the input port  14  of the manifold  13 . An output coupling  32  extends from the outlet port of the manifold  13  formed in the bottom surface  25 . As will be apparent a pressurized supply is preferred because it increases the efficiency of a filling operation as the piston retracts thereby to maximize the filling force in the material being admitted into the sleeve 
     FIG. 4 more clearly depicts the operation of this dispensing system by showing in detail the operation of the assembly including the sleeve  12 . At State 1 in FIG. 4, the piston  16  is fully compressed and abuts the valve  17 . The operating mechanism has rotated the valve to a closed position. At State 2 the actuating mechanism rotates the valve  17  to an input position whereupon, as shown in FIG. 2, the input port  18  aligns with the input aperture  20  and the valve  17  blocks the output port  19 . Then the piston  16  is withdrawn to a position as shown in State 3. Assuming that the material supplied in the sleeve  30  of FIG. 3 is incompressible and all the components involved in the transfer of the material are not compressible, withdrawing the piston  16  increases the amount of material by the volume defined by the cross-sectional area of the piston  16  and the distance it travels during its upward movement. The pressurized supply  30  assures that the material fills this volume completely. 
     After reaching an upper limit of travel in State 3, the mechanism actuates on the valve  17  and rotates the actuating pin  26  to the position shown as State 4. The pin  26  provides an engagement means by which the mechanism interfaces with the valve  17 . This action closes the input port  18  and aligns the output port  19  in the valve  17  as shown in FIG. 2 with the output aperture  34 . Next the piston  16  is driven downward back to the position shown in State 1 of FIG. 4 where the piston  16  contacts the upper edge  29  of the valve  17  or any preprogrammed position in between. An equal amount of material displaces outwardly through the output coupling  32  shown in FIG.  3 . In such an application the piston  16  and valve  17  operate in a sequential or mutually exclusive fashion. 
     In use, and as described previously, the assemblies associated with the sleeves  11  and  12  preferably operate in an alternating fashion. That is, the upward movement of the piston  15  within the sleeve  11  enables material to enter the sleeve  11  as the piston  15  is withdrawn. Simultaneously, the piston  16  moves downward to dispense material. Upon completion of that operation the sequence reverses. The piston  16  is withdrawn while the piston  15  moves downward. As a result, the pistons associated with each of the sleeves  11  and  12  alternately eject material into the manifold  13  thereby providing a greater material throughput. 
     In one embodiment, the manifold  13  includes an output passage such as the output passage  24  shown in FIG. 2 with a corresponding output passage  33  as shown in FIG.  2 . Similarly the second input passage  34  connects internally to the input passage  21  with both connecting to the input port  14 . 
     Now referring to FIGS. 1 and 5, a set of rotary actuators  40  and  41  coact through shafts, typically coaxial shafts, with a gear mechanism  42  on a base plate  43  to move the actuator  26  associated with the sleeve  11 . If the actuators  40  and  41  are two-position rotary actuators, one of the rotary actuators shifts the actuator  26  between its blocking position and a position for input while the other actuator  41  shifts the actuator and its valve  17  from a blocking position to a position for dispensing. A similar set of rotary actuators  44  and  45  control an identical valve inside the sleeve  11 . 
     Still referring to FIGS. 1 and 5, a stepping motor  46  drives a nut  47  of the precision ball screw mechanism in response to rotation of the motor output shaft  48 . This translates rotary motion of the stepping motor  46  into longitudinal motion of the nut  47 . This nut  47  connects to a yoke  49  that carries a linear encoder  50  and that engages an upper end  51  of the piston by engaging a channel  52  shown most clearly in FIG.  2 . With the linear encoder  50  serving as a feedback device, precision motion of the nut  47  and yoke  49  between any two positions, including a position defined when the piston  16  abuts the valve  17 , can be obtained by conventional position control means. 
     A similar structure, including the rotary actuators  44  and  45  control the piston  15  and valve associated with the sleeve  11 . A computer-based system or other control system, not shown, controls the operation of this apparatus, especially the rotation of the valve  17  and the longitudinal displacement of the piston  16 . The design of such a system, given the disclosed inputs and outputs, is well within the capability of one of ordinary skill in the art. 
     As also shown in FIG. 1, a clamp  53  positions sleeves  11  and  12 . This facilitates cleaning operations. As many of the materials that will be dispersed have setting times, it is often desirable to clean any mechanism contacting the material being dispensed. In the structure shown in FIGS. 1 and 5, it is merely necessary to remove the clamp  53  and snap out the sleeves  11  and  12  with their valve and pistons for cleaning. 
     Certain materials must be maintained at elevated temperatures. In this connection it becomes a straightforward process to apply a heating element and thermocouple to the clamp  53 , manifold  13  and other related areas in order to maintain the temperature of the material at a proper temperature. Systems for providing such temperature control are also well known in the art. 
     The foregoing operation has been described in terms of dispensing a one-part material. If the manifold is modified so that each of the input passages, such as the input passages  21  and  24 , are routed to separate input ports that in turn are coupled to receive the two parts of the mixture, the pistons can operate in tandem thereby to pump the two parts through the passages  24  and  33  to be mixed as they move toward the output coupling. 
     Therefore, there has been described in the foregoing figures a dispenser that is readily adapted for high volume work including a wide variety of materials to be dispensed. Accuracy and repeatability in the volume dispensed is achieved by the use of the individual cylinders, such as sleeves  11  and  12 , and the control of piston displacement through conventional, but high-precision positioning systems. The sleeves, valves and pistons can all be composed of materials that are adapted to withstand the environment of a particular material. However, even if wear occurs, it will be apparent that it is a simple matter to replace those mechanisms without having to undertake any major maintenance functions. 
     This invention has been disclosed in terms of certain embodiments. It will be apparent that many modifications can be made to the disclosed apparatus without departing from the invention. Therefore, it is the intent of the appended claims to cover all such variations and modifications as come within the true spirit and scope of this invention.