VOLUMETRIC-DISPLACEMENT DEVICE HAVING MOLDED PISTONS AND CYLINDERS

Abstract: A volumetric-displacement-maximizing device includes a molded slider (12) bidirectionally movable within an elongate cavity (14) formed within a molded body (16). The body (16) also includes a port structure (18) with an output port (18a) and an input port (18b), each providing channels for communication between the cavity (14) and an extra body location. A power device (22) causes the slider (12) to move bidirectionally within the cavity (14), and the clearance between the slider (12) and the cavity (14) exceeds 0 - but is less than approximately 0.0003 inches. The device of the invention takes several alternative forms including a fluid mechanical device, and has several alternate applications as a pump, valve, or motor. The invention also includes various method features.

Description: VOLUMETRIC-DISPLACEMENT DEVICE HAVING MOLDED PISTONS AND CYLINDERS Cross-Reference to Related Applications This application claims priority from U.S. Provisional Patent Application Serial 60/052,839 entitled VOLUMETRIC-DISPLACEMENT DEVICE, filed on July 17, 1997. Background and Summary of the Invention This invention relates generally to the field of fluid mechanics, and in particular, to a novel volumetric-displacement-maximizing device (which may also be thought of as a fluid mechanical device), and to a process involved in making components thereof, which offers the opportunity of creating, in a relative sense, very small devices which are capable of operating in different conventional applications, such as fluid pumping applications, fluid motor applications, and fluid-flow control (valving) applications. As distinguished from conventional, generically alike, fluid mechanical devices such as fluid motors, fluid pumps and fluid control valves, the structure of the present invention distinguishes itself by featuring, essentially, two key and central components — a body in which there is a chamber for receiving and handling fluid, and a moveable element, such as a slider or a rotator disposed within that chamber which moves, either to influence and effect the flow, or to control the flow, of a fluid, or which moves in response to the application of externally applied pressure fluid. No independent seal structure is employed between the coacting and tightly contacting surfaces of these two devices, wherein, preferably, the chamber just mentioned has a generally circular cross section (though it could have another shape, such as an ovate shape), and wherein the moveable element, slider, valve spool, etc., has a close-tolerance matching outer, for example, circular, surface which fits snugly but in no sense bindingly with the inside surface of the chamber. According to the invention, it is preferable that the clearance space between these two surfaces, at all locations of confrontation, lies in the range of within about 0.0001-inches and about 0.0003-inches. Surprisingly, these surfaces can be produced in these components where one selects, as I have done, to form these components a suitable moldable plastic material, such as a structural thermoplastic material. I have discovered that the molding process itself yields surface characteristics which require no further machining or other treatment to assure that they can be brought into such close-tolerance contiguity, with assurance that they will slide or rotate relative to one another easily, and yet maintain, substantially indefinitely, an essentially leak-free seal capable, for example, and preferably, of sustaining a fluid-pressure differential across the movable element (slider, valve spool, etc.) of at least about one atmosphere. The present invention which involves the two-piece, central, co- acting structures just mentioned, and the method of molding the same, has opened the door to creation of quite small devices, for example devices wherein the "diameter" of the chamber and moveable element is, in each case, no greater than about 1-inch, and with the capability of performing, for example in fluid motor and in fluid pump applications, for handling and responding to an extraordinarily high volume of fluid movement over relatively short periods of time. These various features and other objects and advantages which are attained by the structure and by the method involved (both to be described below) upon which this invention rests, will become more fully apparent as the description that now follows is read in conjunction with the several drawing figures that form part of this disclosure. Brief Description of the Drawings Fig. 1A is a fragmentary, sectional view of a first prior art pump. Fig. IB is a schematic illustration of the volumetric displacement achievable with the prior art pump design shown in Fig. 1 A. Fig. 1C is a fragmentary, sectional view of a second prior art pump. Fig. 2 A is a fragmentary, sectional view of a pump version of the present invention. Fig. 2B is a schematic illustration of the volumetric displacement achievable with the pump shown in Fig. 2 A. Fig. 3 is a semi-schematic/semi-representational, fragmentary illustration of a first embodiment of the structure of the present invention. Fig. 4 is a semi-schematic/semi-representational, fragmentary illustration of a second embodiment of the structure of the present invention depicting a type of relative-motion, fluid-sealing, fluid displacement activity. Fig. 5 is a semi-schematic/semi-representational, fragmentary illustration of a third embodiment of the structure of the present invention depicting another type of relative-motion, fluid-sealing, fluid displacement activity. Fig. 6 is a schematic illustration of certain features of the present invention, which features may be included in any embodiment of the invention. Fig. 7 is a schematic illustration of certain additional features of the present invention, which features may be included in any embodiment of the invention. Fig. 8 is an isometric view of a fourth embodiment of the present invention. Fig. 9 is an exploded, isometric view of the fourth embodiment of the present invention shown in Fig. 8. Fig. 10 is a top view of the fourth embodiment of the present invention shown in Fig. 8. Fig. 11 is a side view of the fourth embodiment of the present invention shown in Fig. 8. Fig. 12 is an isometric view of one version of a reciprocation member component of the fourth embodiment of the present invention shown in Fig. 8. Figs. 13-16 are each sectional views through lines 13-13 in Fig. 8 which illustrate relative positioning of components during 360° rotation of crank/cam member. Fig. 17 is a sectional view through lines 17-17 of Fig. 8. Figs. 18-19 are isometric views of the fourth embodiment of the present invention shown in Fig. 8, with certain sections of the micro pump broken away to illustiate how the pistons move or change location within the cylinder. Fig. 20 is an exploded, isometric view of a second version of the fourth embodiment of the present invention shown in Fig. 8. Fig. 21 is a sectional view of the cam member through lines 21- 21 in Fig. 20. Fig. 22 is a sectional view of an alternate version of the cam member referred to in Fig. 21. Figs. 23-26 are each sectional views through lines 23-23 in Fig. 8 which illustrate relative positioning of components during 360° rotation of crank/cam member. Figs. 27 is an isometric view of a second version of a reciprocation member component of the fourth embodiment of the present invention shown in Fig. 8. Fig. 28 is a top view of a fifth embodiment of the present invention. Fig. 29 is a top view of an sixth embodiment of the present mvention. Fig. 30 is a top view of a seventh embodiment of the present mvention. Detailed Description of the Preferred Embodiment and the Preferred Manner of Practicing the Invention In addition to the following description of the above-identified drawings, the present application also includes attachment A which provides textual and graphic infoimation about the background of the invention, and a further description of the invention and how preferably to implement it. Before describing the invention, certain other preliminary matters should be understood. First, the drawings, particularly Figs. 3-7, provide illustrations allowing the reader to understand various, alternate versions of the invention. As will be understood, the invention may take various forms, including pump, valve and motor versions. Figs. 3-7 provide illustrations which allow the reader to understand each of these versions. Second, use of the prefix "micro" in the present application only describes size and does not imply micro-machining. Third, as will also be described, a present focus for applications of the invention is as a micro pump for a vital signs monitor which performs oscillometric noninvasive blood pressure measurement (NIBP). A commercial example of such a device is the PROPAQ ENCORE vital signs monitor manufactured by Protocol Systems Inc. of Beaverton, Oregon. The present disclosure also incorporates by reference the teachings of U.S. Patents Nos. 4,949,710 to Dorsett et al. and 5,339,822 to Taylor et al, and pending U.S. patent application serial numbers 08/673,318, 08/883,754, and 08/884,359, each to Nelson et al., and each for an NIBP MEASURING SYSTEM. Referring now to Figs. 1 A-C, certain prior art pumps are shown to focus the reader on to-be-described distinctive features of the invention. Fig. 1A shows a prior art diaphragm pump 1 with a reciprocating member 2 (reciprocating motion shown by arrow A) attached to a flexible diaphragm 3 for pushing the diaphragm in, toward a housing section HS, and out, away from section HS. The result of such operation is to force fluid, contained in an enclosure defined by diaphragm 3 and section HS, out through exit port 5a in the direction of the arrow, or to draw fluid into that enclosure via entry port 5b in the direction of the arrow (check valves for controlling entry and exit of fluid through the desired ports are not depicted). Fig. IB depicts schematically the volume of fluid that is displaced when diaphragm pump 1 is operated, with that volume having a length L, a height H, and a width (undepicted). Fig. 1C shows a wabble-type prior art pump 6 with a bulb- compressing member 7 that sequentially compresses flexible bulbs 8 for either forcing fluid out of (via exit ports 9a) or drawing fluid into (via entry ports 9b) respective enclosures, each defined by each bulb and housing section HS. From a volume-displacement viewpoint, the volume of fluid displaced by a wabble-type pump like pump 6 is equal to 2 x (0.5 x bulb height (BH) x bulb diameter). Fig. 2A shows the volumetric-displacement-maximizing device of the present invention at 10 including a molded slider 12 bidirectionally movable within an elongate cavity 14 formed within a molded body 16. Body 16 also includes port structure 18 with an output port 18a and an input port 18b, each providing channels for communication between the cavity and an extrabody location. A power device (undepicted) causes slider 12 to move bidirectionally within cavity 14, and the clearance between slider 12 and cavity 14 exceeds 0- but is less than about .0003-inches. Fig. 2B depicts schematically the volume of fluid displaceable using device 10, with that volume having a length L, a height H, and a width (undepicted). Assuming the widths are the same, it is easy to see how the present invention maximizes volumetric displacement of fluid compared to prior art pumps such as those shown in Figs. 1 A and lC. Compared to other micro pumps usable for vital signs monitors, it is presently estimated that the present invention affords a 280% increase in fluid displacement. It is important to focus on certain features of the invention, i.e. as will be described, the present invention obtains the schematically-depicted, superior volumetric displacement of fluid solely with molded components that meet the above clearance requirement to effect a to-be-further described interfacial, substantially leak-free seal. Device 10 does not use o-rings, sealant, or other sealing materials. Preferably, slider 12 and body 16 are formed of an injection molded plastic material such a that sold under the trademark ULTEM, which material is dimensionally stable, self-lubricating, and has an effective resistance to water absorption. As will be described further in connection with Figs. 8-14, device 10 may take the form of a molded micro pump for vital signs monitors. As will also be further described, the power device transfers power from an applied voltage, and wherein vaiying the voltage causes slider 12 to move bidirectionally within cavity 14. Preferably, slider 12 has a curved outer surface and cavity 14 is formed to have a cross-sectional shape chosen from the group consisting of a cylinder and an ellipse. Referring now to Figs. 3-7, the description shifts to various, alternate ways of thinking about the invention by viewing the semi- schematic/semi-representational illustrations contained in the to-be-described drawings. Referring to Fig. 3 for a first alternate description of the invention, there is shown what may be thought of as a fluid mechanical device 10 operable selectively in motor, pump and valve applications, with those applications including, selectively, control of and response to fluid-flow conditions. Device 10 includes a non-machined body 16 including an elongate fluid chamber 14 having a long axis LA, and an elongate, inside wall surface 16a circumsurrounding axis LA. An elongate, non-machined, movable slider 12 with spaced opposite ends 13a, 13b, has an outside surface 12a disposed in a to-be-further-described bare-clearance, reversible, sliding-fit condition within chamber 14. Slider 12 is in contact with wall surface 16a in a manner circumsurrov ding axis LA, and movable reversibly within the chamber along axis LA. Wall surface 16a and slider surface 12a contact one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non-leak-changing, fluid-pressure differential on spaced opposite ends 13a, 13b of slider 12, which differential is no less than about one atmosphere. Preferably, the material forming body 16 and slider 12 each has substantially the same coefficient of thermal expansion. Also, the body and the slider are preferably formed of the same moldable plastic material. Referring again to Fig. 3, there is now a shift to a second alternate description of the invention. A fluid-mechanical device 10 is operable selectively in motor, pump and valve applications, with each such application including, selectively, control of and response to fluid-flow conditions. Device 10 includes a molded body 16 including an elongate fluid chamber 14 having a long axis LA. Chamber 14 is at least partially defined by an elongate, cylindrical wall surface 16a having a first radius of curvature Rl and circumsuπounding axis LA. Axis LA defines the center of circularity of wall surface 16a. Still referring to Fig. 3, an elongate, molded, movable, cylindrical slider 12 is disposed in a bare-clearance, reversible, sliding-fit condition within chamber 14. Slider 12 includes an outer, cylindrical wall surface 12a having a radius of curvature R2 which is slightly less than radius of curvature Rl, and which is in effective sealing contact with wall surface 16a. Slider 12 is also movable reversibly within the chamber along axis LA in the direction of arrows A. The body's wall surface 16a and the slider's wall surface 12a contact one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non-leak-changing, pressure-fluid differential on spaced opposite ends 13a, 13b of slider 12, which differential is no less than about one atmosphere. Preferably, the difference in lengths between radii Rl and R2 lies within a range not exceeding about 0.0003-inches, and even more preferably within the range of about 0.0001-inches to about 0.0003-inches. In viewing Fig. 3, it should be understood that the slight difference in lengths of Rl and R2 is barely visible except when exaggerated by the lines extending to the left of Fig. 3 which are identified by arrows Rl and R2. Essentially, the image of slider 12 positioned within chamber 14 approximates two concentric circles, with the inner one (slider 12) having a radius of curvature that is slightly less than the radius of curvature for the outer one (chamber 14). Next, the present description shifts again to a third alternate way of considering the invention. A fluid-mechanical device 10 is operable selectively in motor, pump and valve applications, each of which include, selectively, control of and response to fluid-flow conditions. Device 10 includes an elongate, molded body 16, within which are two, elongate, generally cylindrical chamber structures 14a,- 14b each having corresponding inside wall surfaces 14a 1 and 14bl, and a long axis LA. Chamber structures 14a, 14b are disposed in spaced, generally axially aligned relationship, and are located generally adjacent different ends 17a, 17b of body 16. An elongate, molded movable sliders 13a, 13b for, and slidably disposed within, each chamber structures 14a, 14b, each slider having an outer, generally cylindrical outside wall surface 13al, 13bl arranged in direct, fluid- sealing, sliding contact with the inside wall surface 14al, 14bl of its respective, associated chamber structure 14a, 14b. Each slider and its associated chamber structure contact one another via their said wall surfaces in a mutually self- sealing condition, which condition is capable of sustaining, indefinitely, a non- leak-changing, fluid-pressure differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere. Continuing with the third alternate way of describing the invention while viewing Fig. 3, an elongate power transmitter 19, shown schematically by a dash-dot line (a representational example of a power transmitter is shown in Fig. 9) extends within body 16 intermediate, and power- transmissively connected to, each of sliders 13a, 13b for moving as an articulated, related-motion element with respect to said sliders, and in a fashion assuring that the sliders reciprocate reversibly in the direction of arrows A essentially as a unit to effect fluid flow with respect to each of chamber structures Ha, 14b. Shifting to a fourth alternate way of describing the invention while viewing Fig. 3, there is shown a fluid pump 10 including an elongate, molded body 16 within which are two elongate, generally cylindrical chamber structures Ha, 14b disposed in spaced, generally axially aligned relationship, one adjacent each end 17a, 17b of body 16, and each chamber structure including an inside, generally cylindrical wall surface Hal, Hbl. A molded piston 12 includes spaced subpistons 13a, 13b which are slidably disposed within chamber structures Ha, 14b. Piston 12 includes outside, generally cylindrical wall surfaces 12a (more specifically surfaces Dal, 13b 1 of subpistons 13) arranged in direct, fluid-sealing, sliding contact with a corresponding inside wall surface Hal, Hbl of associated chamber structures Ha, 14b. That sealing contact creates a sealed condition which is capable of sustaining, indefinitely, a non-leak-changing, pressure-fluid differential on opposite sides of each subpiston, which differential is no less than about one atmosphere. Pump 10 also includes an elongate driver 20, shown schematically by bolded dashed lines, extending within body 16 intermediate and drivingly connected to each of subpiston 13 a, 13b for driving them reciprocably in the direction of arrows A as a unit to displace fluid (undepicted) contained in chamber structures Ha, 14b. A suitable power-operated motor 22 (also shown schematically) drivingly connected to driver 20 via a power transmitter 19, is operable to impart reciprocating driving motion to driver 20, and therethrough simultaneously to subpistons 13a, 13b. Shifting to a fifth alternate way of describing the invention while viewing Fig. 3, there is shown a fluid-flow control valve including a molded valve body 16 that has formed within it fluid-flow-control chamber structure 14. Referring for a moment back to Fig. 2 A, fluid passage structure 18 communicates with chamber structure 14 and includes a pair of ports 18a, 18b opening to the chamber structure. An adjustably movable, molded valve spool 12 is disposed within chamber structure 14, and is selectively moveable under the influence of an applied motion force to change the degree of fluid intercommunication permitted between passage structure 18 and chamber structure 14 via at least one of ports 18a, 18b. Valve spool 12 and chamber structure 14, in corresponding regions not spanning at least one of ports 18a, 18b, are in direct sealing contact with one another in a condition capable, indefinitely, of sustaining, against any leakage, a fluid-pressure differential of at least about one atmosphere. Shifting to a sixth alternate way of describing the invention while viewing Fig. 3, there is shown a fluid motor 10 including a molded motor body 16, within which is formed fluid-displacement chamber structure 14. Molded motion-displacement structure 12 is disposed effectively within chamber structure 14, and movable cyclically therewithin in the direction of arrows A under the selected cyclic influence of applied pressure fluid (undepicted). Chamber structure 14 and motion-displacement structure 12 operate in relative- motion, fluid-sealing contact directly with each other in a circumstance exhibiting a continuous sealed condition capable, indefinitely, of sustaining, against any leakage, a fluid-pressure differential of at least about one atmosphere. Motor 10 also includes a power-output drive coupler 20 drivingly connected to motion-displacement structure 12, and operable to transmit drive- output power to a selected external instrumentality via, for example, a power transmitter like that shown schematically at 19. Shifting to a seventh alternate way of describing the invention while viewing Fig. 3, there is shown a fluid-mechanical device 10 operable selectively, inter alia, in motor, pump and valve applications, with those applications including, selectively, control of and response to fluid-flow- conditions. Device 10 includes a molded body 16 including an elongate fluid chamber 14 having a long axis LA and an elongate, inside wall surface 16a circumsuiTounding axis LA. An elongate, molded movable slider 12 has an outside wall surface 12a disposed in a direct-contacting, bare-clearance, reversible, sliding-fit condition within chamber 14, and in contact with inside wall surface 16a in a manner circumsurrounding axis LA, and movable reversibly within the chamber along axis LA. Chamber 14 and slider 12 are designed to perfoim in an operating environment wherein different fluid- pressure differentials within a defined range may exist across opposite ends of slider 12 (the opposite ends of slider 12 are depicted as subsliders 13a, 13b). In the absence of any external force tending to effect either compression or decompression with respect to fluid in chamber 14, movement of slider 12 in a defined distance L along axis LA results in the substantially exact, positive or negative, displacement of a volume (A » L) of fluid, where A is the surface area of that portion of the slider which is the effective working surface area of the slider relative to such displaced fluid, and L is the distance moved by the slider relative to chamber 14 during such displacement activity. Shifting to an eighth alternate way of describing the invention while viewing Fig. 3, there is shown a fluid-mechanical device 10 for effecting various fluid-flow conditions in motor, pump and valve applications, and the like. Device 10 includes a body foimed of a selected, suitable moldable material, and including an elongate fluid chamber 14 having a long axis LA and an elongate, inside wall surface 16a characterized by self-axis- circumsuiTOunding curvilinearity as viewed normally in a transverse plane which intersects both axis LA and inside wall surface 16a. That intersection with axis LA is substantially a right-angle intersection, and inside wall surface 16a has a mold-defined surface quality with a selected and determined local flatness offering a chosen and desired fluid-sealing capability when brought into mutually-cooperating, confronting, local-area, direct-contacting contiguity with another surface of like surface quality. Continuing with the description of the eighth alternate description, device 10 also includes an elongate slider 12 formed of the same, selected moldable material as that mentioned above for body 16, and has a long axis LA and an elongate, outside wall surface 12a also characterized by self- axis-circumsuiTounding curvilinearity as viewed normally in a transverse plane which intersects both the slider's long axis LA and outside wall surface 12a. That second-mentioned intersection with the slider's long axis LA is also substantially a right-angle intersection, and outside wall surface 12a has a mold-defined surface quality substantially matching that of the chamber's inside wall surface 16a. Slider 12 is also slidably disposed within chamber 14, with inside wall surface 12a and outside wall surface 16a, as a consequence, being in such mutually-cooperating, confronting, local-area, direct-contacting contiguity with one another that the desired fluid-sealing capability is realized, and is sufficient to prevent fluid leakage between the two wall surfaces under circumstances with a fluid pressure differential of up to about one atmosphere existing between opposite ends of slider 12 within chamber 14. The opposite ends of slider 12 are depicted as spaced apart subsliders 13a, 13b. Shifting to a ninth alternate way of describing the invention while viewing Fig. 3, there is shown a fluid-mechanical device 10 operable selectively for the control of, and or response to, certain fluid-flow conditions in different selected fluid-displacement applications. Device 10 includes a body 16 foi ed of a selected moldable material and includes a fluid chamber 14 which has, and is at least partially defined by, a fluid-impervious surface structure Ha. Also included is a relative-motion element 12 foimed of the same moldable material mentioned above and having a fluid-impervious surface structure 12a for relative-motion, fluid-sealing, fluid-displacement activity adjacent the chamber's surface stiiicture Ha. That fluid-displacement activity is characterized by a traveling line of fluid-sealing surfacial confrontation between said two surface structures, which line defines a fluid-sealed moving boundary for fluid present in said chamber. Fluid motion of that boundaiy, depending upon the direction of motion, effects positive or negative displacement of fluid with regard to chamber 14, and the sealed condition existing along that line is capable of sustaining, indefinitely, a non-leak- changing, fluid-pressure differential across the line of no less than about one atmosphere. In Fig. 3, an example of that traveling line of fluid-sealing surfacial confrontation is the distance between any two points along the interface between one of subelements 13a, 13b of relative-motion element 12 and wall surface 16a. The motion of element 12 may be various types, such as sliding or translational as shown in Fig. 3. A tenth alternate description involves referring to the ninth description immediately above and referring to Fig. 4. In Fig. 4, pertinent sections of a fluid-mechanical device 110 are shown including a annular relative-motion element 112 which revolves within a generally spherical chamber 114 so that the traveling line of fluid-sealing surfacial confrontation is endless. The illustration in Fig. 4 is like a sectional view of Fig. 3 along lines 4-4 except that certain, to-be-described differences exist between this embodiment and that described in Fig. 3. As with the description of Fig. 3, the reader should understand that there is a slight difference in the radius of element 112 and the radius of chamber 114. Also, as with the seventh alternate description above, arrow A identifies the surface area of that portion of the slider which is the effective working surface area of the slider relative to the displaced fluid. Element 112 has a channel 112b formed in it to allow communication with port 118, and thus to allow displacement of fluid from chamber 114. Remaining elements of device 110 would be the same as those for device 10 described immediately above in connection with the ninth alternate description. An eleventh alternate description involves referring to the ninth and tenth descriptions immediately above and referring to Fig. 5. In Fig. 5, pertinent sections of a fluid-mechanical device 210 are shown including a relative-motion element 212 operable to exhibit rolling, translational motion in a chamber 214 to produce the desired fluid displacement. Again, remaining elements of device 210 would be the same as those for device 10 described above in connection with the ninth alternate description. Referring back to Fig. 3, a twelfth alternate way of describing the invention involves a fluid-displacement device 10 with a molded body 16 defining a cavity 14 that contains a volume of fluid (undepicted). Device 10 includes an output port 18a that allows communication between cavity 14 and a desired extrabody location. Device 10 also includes molded fluid-sealing/fluid- displacement structure 12 fitted for relative movement within cavity 14. Structure 12 may include substructure 13a, 13b. Upon relative movement of body 16 and fluid-sealing/fluid-displacement structure 12, device 10 is selectively operable to prevent the volume of fluid from exiting the cavity via output port 18a (see position of substructure 13a shown by solid lines), and to allow the volume of fluid to exit the cavity via the output port (see position of substructure 13a shown by dot-dash lines). Device 10 further includes motion structure, such as driver 20, power transmitter 19 and motor 22, for causing the relative movement of structure 12 and body 16. Referring again to Fig. 3, a thirteenth alternate way of describing the invention involves a fluid-displacement device 10 which includes a molded body 16 defining a cavity 14 that contains a volume of fluid (undepicted). Device 10 also includes an output port 18a that allows communication between the cavity and a desired extrabody location, and molded fluid-sealing/fluid- displacement structure 12 which includes substructure 13a, 13b. Structure 12 is fittable and movable within cavity 14 to first (see solid line depiction of substructure 13a) and second (see dot-dash line depiction of substructure 13a) positions. Structure 12 is also selectively operable in the first position to prevent the volume of fluid from exiting cavity 14 via output port 18a, and in the second position to allow the volume of fluid to exit cavity 14 via output port 18a. Referring to Figs. 6-7, certain additional features of the various alternate descriptions are shown. These additional features show ways in which the slider (or piston) element may be moved. In Fig. 6, a single motor 22 causes crank 24 to move drivers 26a, 26b, which ultimately move subsliders 13a, 13b in desired directions. In Fig. 7, dual motors 22a, 22b cause corresponding cranks 24a, 24b to move drivers 26a, 26b which ultimately move subsliders 13a, 13b in desired directions. The features shown in these figures are described further in Attachment A. Referring now to Figs. 8-14, and attachment A, representational examples of the invention are shown as a micro pump suitable for application in vital signs monitors such as Protocol Systems' PROPAQ ENCORE monitor referred to above. In Figs. 8-11, a fourth embodiment of the invention is shown at 310 and takes the form of a micro pump for a vital signs monitor. Pump 310 includes a molded body 316 with a central region 316a and an output port 318a. Body 316 defines a chamber 314 including a cylinder 315 in which slider structure 312 (which includes subsliders or pistons 313a, 313b) is bidirectionally movable. Pistons 313a, 313b are joined by a driver 320 which is operably connected to crank shaft 328a of a motor 328 via a slider- reciprocation member 330 and a cam crank 332. Still referring to Fig. 9, the opposing rounded ends of driver 320 are suitably, fixedly attached to each piston 313a, 313b by being placed in a socket of each piston, such as socket 313al. Opposing, corresponding valve plates 334 and manifolds 336 enclose opposing outer ends of subsliders 313a, 313b, and are suitably joined to central region 316al such as by ultrasonic welding or other suitable joining methods. Suitable check valves 337 control fluid flow, and a motor mounting plate 338 is suitably joined to central region 316a. For assembly purposes, each check valve includes pointed ends which extend past a bulging region (Fig. 9). Those pointed ends are subsequently cut off with a suitable cutting device so that the pointed ends do not extend into the cavity defined by cylinder 315 (Figs. 13-16).- The resulting micro pump 310 is therefore a molded, preferably plastic device made from plastic material sold under the trademark ULTEM. Figs. 10-11 show top and side views of pump 310, respectively. Referring back to Fig. 9, certain other features of the invention are now described, micro pump 310 includes crank structure for causing the bidirectional movement of slider 312. The crank structure includes motor shaft 328a, reciprocation member 330 and crank/cam 332. Rotation of crank shaft 328a about an axis corresponding to the long axis of shaft 328a causes bidirectional movement of slider 312 via the following operatively connected components: cam 332, member 330, and driver 320. The arrangement of slider 312 with cylindrically shaped ends 313a, 313b joined by elongate driver 320 result in a barbell-like configuration with opposing ends (pistons) linked by a central bar (driver 320). Fig. 12 shows the side of slider-reciprocation member 330 nearest motor 328. From that view, there is shown a recess which receives cam crank 332. A pin 332a is offset from the rotational axis of motor shaft 328a and cam/crank 332, and extends through slot 333 formed in member 330. As will be seen from the description immediately following, that offset location causes pin 332a to drive translational movement of the pistons within the cylinder 315. Shifting now to Figs. 13-16, the way in which rotational motion of motor shaft 328a and cam/crank 332 causes bidirectional, translational motion of pistons 313a, 313b within cylinder 315 is shown. Fig. 13 shows what may be thought of as a stalling point where the crank of cam/crank 332 is pressing against the side of member 330 nearest piston 313b causing movement to one end of cylinder 315. Fig. 14 shows how the crank is positioned after 90° counterclockwise rotation of motor shaft 328a and cam/crank 332. Fig. 15 shows how the crank is positioned after another 90° counterclockwise rotation of motor shaft 328a and cam/crank 332, with the crank of cam/crank 332 pressing against the side of member 330 nearest piston 313a and causing movement to the end of cylinder 315 opposite that which the pistons moved to in Fig. 13. Fig. 16 shows how the crank is positioned after a fourth 90° counterclockwise rotation of motor shaft 328a and cam/crank 332. Of course, motor shaft 328a would normally be rotating continously, causing continuous reciprocation of the pistons within the cylinder, which in turn cause continuous intake of air through the check valves and output through output port 318a. The rotational movement could also be clockwise or counterclockwise. Figs. 18-19 illustiate in isometric views the piston positioning in cylinder 315 shown in Figs. 13 and 15, respectively. Fig. 20 is like Fig. 9 only that a second, alternate version of the cam/crank and slider-reciprocation member is shown. With this version, there is less likelihood that the slider-reciprocation member will rock relative to the cam crank. In Fig. 20, there is shown a cam member 332' with pin 332a', and a slider-reciprocation member 330'. All other components are the same as that described in connection with Fig. 9. Fig. 21 shows a sectional view of cam member 332' with pin 332a' being offset from the center of oval-shaped cam 332'. Fig. 22 shows a sectional view of another version of that cam member as cam member 332" with pin 332a" being offset from the center of circle-shaped cam 332". Both versions of the cam member are operable in a micro pump depending upon the duration, displacement and timing variables that are desired for a given application. Shifting now to Fig. 27 and then back to Figs. 23-26, the way in which rotational motion of motor shaft 328a and cam 332' causes bidirectional, translational motion of pistons 313a, 313b within cylinder 315 is shown. Fig. 27 shows the side of slider-reciprocation member 330' nearest motor 328. From that view, there is shown a recess which receives cam 332'. A pin 332a' is offset from the rotational axis of motor shaft 328a and cam 332', and extends through slot 333' formed in member 330'. As will be seen from the description immediately following, that offset location causes pin 332a' to drive translational movement of the pistons within the cylinder 315. Turning back to Fig. 23 shows what may be thought of as a starting point where cam 332' is pressing against the side of member 330' nearest piston 313b causing movement to one end of cylinder 315. Fig. 24 shows how the crank is positioned after 90° counterclockwise rotation of motor shaft 328a and cam 332'. Fig. 25 shows how the crank is positioned after another 90° counterclockwise rotation of motor shaft 328a and cam 332', with the cam pressing against the side of member 330' nearest piston 313a and causing movement to the end of cylinder 315 opposite that which the pistons moved to in Fig. 23. Fig. 26 shows how the crank is positioned after a fourth 90° counterclockwise rotation of motor shaft 328a and cam 332'. Of course, motor shaft 328a would normally be rotating continously, causing continuous reciprocation of the pistons within the cylinder, which in turn cause continuous intake of air through the check valves and output through output port 318a. The rotational movement could also be clockwise or counterclockwise. In Fig. 28, a fifth embodiment of the invention is shown as micro pump 410 with two pressure transducers 440a, 440b, and two valves 442a, 442b to accommodate use in measuring blood pressure in a vital signs monitor as described above. In Fig. 29, a sixth embodiment of the invention is shown as micro pump 510 with two ports 518a and two motors 528b, 528c to accommodate use in measuring blood pressure in a vital signs monitor as described above. In Fig. 30, a seventh embodiment of the invention is shown as micro pump 610 with two ports 618a, two pressure transducers 640a, 640b, and two valves 642a, 642b and two motors 628b, 628c, all to accommodate use in measuring blood pressure in a vital signs monitor as described above. With respect to the method of the invention, it is important to consider the five basic phases that an injection molded part undergoes to become created. The following is a list of those phases: 1. Part Design 2. Mold Design 3. Mold Construction/Fabrication 4. Injection Molding Process 5. Design For Assembly (DFA) For each of the above phases, several guidelines should be followed as described below. The listed guidelines are the presently known most important ones, but the lists are not meant to be exclusive. 1. Part Design - There must be thorough knowledge of each part's functional requirements and design rules and guidelines for a particular plastic must be followed. Examples of such requirements, rules and guidelines are listed below: • Uniform wall thickness • Material selection • Material limits • Functional requirements • Structural requirements • Theimal requirements • Design standards for the material 2. Mold Design - The mold design must ensure the heating and cooling is sufficient for the part as well as the function of the mold to avoid warpage and obtain part tolerances. Important considerations include: • Type of tool material • Tool cooling • Tool heating • Runner design • Feature creation (slides,cavity,core) • Parting line locks • Guided ejection • Sensors (temperature,pressure) 3. Mold Construction/Fabrication - The tooler must consider the different types of material fabrication that will result in the tolerances required. Tool hardness and temperature limits are related to tool life. Important considerations include: • Milling • grinding • EDM (Electric Discharge Machining) • Custom or standard geometry • Mold base (custom or standard) 4. Injection Molding Process - This is when the plastic meets the tool. All of the following parameters must be balanced to obtain the desired result. It is desirable to measure cavity pressure to verify the device is operating within the specified tolerances and that the cavity is consistently filled with fluid in a repeatable manner. Statistical process controls are implemented to verify and track the molding process. Important considerations include: Injection mold machine selection (tonnage, size) Material diying Injection temperature Injection speed Packing pressure Mold pressure Mold temperature • Hold time Testing (tolerance, geometty) Post processing (fixturing, annealing) 5. Design For Assembly - Testing procedures are placed throughout the assembly process to verify functional requirements are met as well as provide a means for statistical process control. Important considerations include: • Minimum parts • Low assembly costs • minimum handling • process flow • Assembly fixtures • Functional testing • Part packaging/shipping While the present invention has been shown and described with reference to the foregoing piefened embodiment, it will be apparent to those skilled in the art that other changes in foim and detail may be made therein without departing fi-om the spirit and scope of the invention as described further below. The invention is further described in the following numbered paragraphs: 1. A volumenϊc-displacement-maximizing, molded micro pump for vital signs monitors, comprising: a molded micro body including an output port, the micro body having an elongate cavity formed therein, and including channel structure to provide communication between the cavity and the output port; a molded slider bidirectionally movable within the cavity; a power device in communication with the slider for causing the slider to move bidirectionally within the cavity; and wherein the clearance between the slider and the cavity exceeds 0- but is less than about .0003-inches. 2. The micro pump of paragraph 1, wherein the power device transfers power from an applied voltage, and wherein vaiying the voltage causes the slider to move bidirectionally within the cavity. 3. The micro pump of paragraph 1, wherein the slider has a curved outer surface. 4. The micro pump of paragraph 3, wherein the cavity is foimed to have a cross-sectional shape chosen from the group consisting of a cylinder and an ellipse. 5. The micro pump of paragraph 1, wherein the micro body and the slider are formed from material that is dimensionally stable and self-lubricating, and have an effective resistance to water absorption. 6. The micro pump of paragraph 5, wherein the material is plastic. 7. The micro pump of paragraph 6, wherein the material is injection- molded. 8. The micro pump of paragraph 1, further including crank structure for causing the bidirectional movement of the slider, wherein the power device includes a motor operatively joined to the crank structure, and the crank structure is operatively joined to the slider, and wherein axial movement of the crank structure about a crank axis causes bidirectional movement of the slider. 9. The micro pump of paragraph 8, wherein the crank structure includes a crank shaft with an outer surface and a central region, and wherein the micro pump further includes volumeπϊc-displacement-maximizing structure engageable with the crank shaft to cause the crank axis of the crank shaft to be located adjacent the outer surface and away from the central region. 10. The micro pump of paragraph 9, wherein the slider is formed in a barbell-like configuration with opposing pistons linked by a central bar. 11. The micro pump of paragraph 1, wherein the power device includes first and second motors each being operatively joined to corresponding first and second crank structure, and wherein each crank structure is operatively joined to the slider. 12. The micro pump of paragraph 1, wherein a pneumatic capacitor is located in the channel structure. 13. A scalable, self-sealing, push-pull micro pump, comprising: a dimensionally stable, low-water-absorption, self-lubricating, injection-molded, high-density-plastic pump housing including an output port, the housing having a substantially cylindrical cavity formed therein, with the cavity in communication with the output port; a pair of spaced-apart, interconnected pistons bidirectionally movable within the cavity, the pistons each having corresponding outer piston surfaces; a power device in communication with the pistons for causing the pistons to move bidirectionally within the cavity; and wherein each outer piston surface exhibits a clearance within the cavity that exceeds 0- but is less than about .0003-inches. 14. A method of achieving optimal volumetric displacement in a micro pump, comprising: selecting piston structure fittable within cylinder structure, both for use in the micro pump; and controlling the clearance between the piston structure and cylinder structure so that the clearance between the piston structure and the cylinder structure is up to about .0003-inches. 15. The method of paragraph 14, further including the steps of selecting crank structure movable about a crank axis for causing movement of the piston structure within the cylinder structure, further selecting crank structure that includes a crank shaft with an outer surface and a central region, and locating the crank axis adjacent the outer surface and away from the central region. 16. A volumetiic-displacement-maximizing device, comprising: a molded body having an inner body surface defining an elongate fluid- containing cavity; a molded slider bidirectionally movable within the cavity, the slider having an outer surface that is located adjacent the inner body surface; and wherein an interfacial seal exists between the body and the slider, the seal having a first clearance threshold between the inner body surface and the outer surface, wherein the first clearance threshold has a coiresponding first motion-causing force and the second clearance threshold has a second motion-causing force, and wherein each motion-causing force causes relative motion for a set of operating conditions, with the second clearance threshold being less than the first clearance threshold. 17. A fluid-displacement-maximizing device, comprising: a molded body foimed with an elongate fluid-containing cavity; a molded slider bidirectionally movable within the cavity; and wherein an alignment exists relative to the slider and the cavity, and the alignment is characterized by a first clearance threshold between the slider and the cavity with a corresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a corresponding second motion- causing force that is less than the first motion-causing force. 18. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; and molding the fluid displacement device to include a slider and a fluid- containing cavity; and aligning the slider within the cavity so that alignment is characterized by a first clearance threshold between the slider and the cavity with a corresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a coiresponding second motion-causing force that is less than the first motion-causing force. 19. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; and molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity in such a way that there is a substantially time- indefinite, substantially leak-free, fluid-pressure condition that exists within the cavity. 20. The method of paragraph 19, wherein the molding step further includes molding in such a way that a substantially time-indefinite, substantially leak-free 15- psig fluid-pressure condition exists. 21. The method of paragraph 19, wherein the molding step further includes molding in such a way that a substantially time-indefinite, substantially leak-free 125- psig fluid-pressure condition exists. 22. The method of paragraphs 20 or 21, wherein the molding step includes molding a cylindrical cavity that is up to about 1-inch in diameter. 23. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity; and making a seal between the slider and the cavity solely by aligning the slider within the cavity so that alignment is characterized by a first clearance threshold between the slider and the cavity with a corresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a corresponding second motion-causing force that is less than the first motion-causing force. 24. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity; and making a seal between the slider and the cavity solely by molding the slider within the cavity so that the seal is characterized by a first clearance threshold between the slider and the cavity with a corresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a corresponding second motion-causing force that is less than the first motion-causing force. 25. A fluid-mechanical device operable selectively in motor, pump and valve applications, such applications including, selectively, control of and response to fluid-flow conditions, said device comprising a non-machined body including an elongate fluid chamber having a long axis, and an elongate, inside wall surface circumsurrounding said axis, and an elongate, non-machined, movable slider having an outside surface disposed in a bare-clearance, reversible, sliding-fit condition within said chamber, and in contact with said wall surface in a manner circumsurrounding said axis, moveable reversibly within the chamber along said axis, said wall surface and slider surface contacting one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non- leak-changing, fluid-pressure differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere. 26. The device of paragraph 25, wherein the material forming said body and that forming said slider each has substantially the same coefficient of theimal expansion. 27. The device of paragraph 26, wherein said body and said slider are formed of the same material. 28. The device of paragraph 27, wherein said material takes the form of a moldable plastic material. 29. A fluid-mechanical device operable selectively in motor, pump and valve applications, such applications including, selectively, control of and response to fluid- flow conditions, said device comprising a molded body including an elongate fluid chamber having a long axis and at least partially defined by an elongate, cylindrical wall surface having a first radius of curvature and circumsunounding said axis, with said axis defining the center of circularity of said wall surface, and an elongate, molded, movable, cylindrical slider disposed in a bare- clearance, reversible, sliding-fit condition within said chamber, and including an outer, cylindrical wall surface having a radius of curvature which is slightly less than said first-mentioned radius of curvature, and which is in effective sealing contact with said body's said wall surface, said slider being movable reversibly within the chamber along the chamber's said axis, said body's said wall surface and said slider's said wall surface contacting one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non-leak-changing, pressure-fluid differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere. 30. The device of paragraph 29, wherein the difference in lengths between said two mentioned radii lies within a range not exceeding about 0.0003-inches. 31. The device of paragraph 29, wherein the difference in lengths between said two-mentioned radii lies within the range of about 0.0001-inches to about 0.0003- inches. 32. A fluid-mechanical device operable selectively in motor, pump and valve applications such applications including, selectively, control of and response to fluid-flow conditions, said device comprising an elongate, molded body, within said body, two, elongate, generally cylindrical chamber structures each having an inside wall surface and a long axis, and disposed in spaced, generally axially aligned relationship, with said chamber structures being located generally adjacent different ends of said body, and an elongate, molded movable slider for, and slideably disposed within, each said chamber structure, each slider having an outer, generally cylindrical outside wall surface arranged in direct, fluid-sealing, sliding contact with the inside wall surface of its respective, associated chamber structure, and each slider and its associated chamber stiiicture contacting one another via their said wall surfaces in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non-leak-changing, fluid-pressure differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere, and an elongate power transmitter extending within said body intermediate, and power-transmissively connected to, each of said sliders for moving as an articulated, related-motion element with respect to said sliders, and in a fashion assuring that the sliders reciprocate reversibly essentially as a unit to effect fluid flow with respect to each of said chamber structures. 33. A fluid pump comprising an elongate, molded body, within said body, two elongate, generally cylindrical chamber structures disposed in spaced, generally axially aligned relationship, one adjacent each end of said body, and each including an inside, generally cylindrical wall surface, a molded piston for, and slidably disposed within, each chamber structure having an outside, generally cylindrical wall surface arranged in direct, fluid- sealing, sliding contact with the inside wall surface in its respective associated chamber structure, such sealing contact creating a sealed condition which is capable of sustaining, indefinitely, a non-leak-changing, pressure-fluid differential on opposite sides of each piston, which differential is no less than about one atmosphere, an elongate driver extending within said body intermediate and drivingly connected to each of said pistons for driving the same reciprocably as a unit to displace fluid in relation to said chamber structures, ' and a power-operated motor drivingly connected to said driver, operable to impart reciprocating driving motion to said driver, and therethrough simultaneously to said pistons. 34. A fluid-flow control valve comprising a molded valve body, fluid-flow-connOl chamber structure foimed within said body, fluid passage structure communicating with said chamber structure and including a pair of ports opening to the chamber stiiicture, an adjustably movable, molded valve spool disposed within said chamber structure selectively moveable under the influence of an applied motion force to change the degree of fluid intercommunication permitted said passage structure and said chamber structure via at least one of said ports, said valve spool and said chamber structure, in regions not spanning said at least one port, being in direct sealing contact with one another in a condition capable, indefinitely, of sustaining, against any leakage, a fluid-pressure differential of at least about one atmosphere. 35. A fluid motor comprising a molded motor body, fluid-displacement chamber stiiicture foimed within said body, molded motion-displacement structure disposed effectively within said chamber structure, and moveable cyclically therewithin under the selected cyclic influence of applied pressure fluid, said chamber stiiicture and said motion-displacement structure operating in relative-motion, fluid-sealing contact directly with each other in a circumstance exhibiting a continuous sealed condition capable, indefinitely, of sustaining, against any leakage, a fluid-pressure differential of at least about one atmosphere, and a power-output drive coupler drivingly connected to said motion- displacement structure, and operable to transmit drive-output power to a selected external instrumentality. 36. A fluid-mechanical device operable selectively, inter alia, in motor, pump and valve applications, such applications including, selectively, control of and response to fluid-flow-conditions, said device comprising a molded body including an elongate fluid chamber having a long axis and an elongate, inside wall surface circumsunounding said axis, and an elongate, molded movable slider having an outside wall surface disposed in a direct-contacting, bare-clearance, reversible, sliding-fit condition within said chamber, and in contact with said inside wall surface in a manner circumsurrounding said axis, moveable reversibly within the chamber along said axis, said chamber and said slider being designed to perform in an operating environment wherein different fluid-pressure differentials within a defined range may exist across opposite ends of said slider, and wherein, in the absence of any external force tending to effect either compression or decompression with respect to fluid in the chamber, movement of said slider a defined distance L along said axis results in the substantially exact, positive or negative, displacement of a volume (A»L) of fluid, where A is the surface area of that portion of the slider which is the effective working surface area of the slider relative to such displaced fluid, and L is the distance moved by the slider relative to said chamber during such displacement activity. 37. A fluid-mechanical device for effecting various fluid-flow conditions in motor, pump and valve applications, and the like, comprising a body foimed of a selected moldable material, and including an elongate fluid chamber having a long axis and an elongate, inside wall surface characterized by self-axis-circumsuirounding curvilinearity as viewed normally in a transverse plane which intersects both said axis and said wall surface, with such intersection with the axis being substantially a right-angle intersection, and said wall surface having a mold-defined surface quality with a selected and determined local flatness offering a chosen and desired fluid-sealing capability when brought into mutually-cooperating, confronting, local-area, direct-contacting contiguity with another surface of like surface quality, and an elongate slider foimed of the same, selected moldable material as that mentioned above for said body, and having a long axis and an elongate, outside wall surface characterized by self-axis-circumsuπounding curvilinearity as viewed normally in a transverse plane which intersects both said slider's said long axis and said outside wall surface, with such second-mentioned intersection with the slider's long axis being substantially a right-angle intersection, and said outside wall surface having a mold-defined surface quality substantially matching that of said chamber's said inside wall surface, said slider being slidably disposed within said chamber, with said inside and outside wall surfaces, as a consequence, being in such mutually-cooperating, confronting, local-area, direct-contacting contiguity with one another that said desired fluid-sealing capability is realized, and is sufficient to prevent fluid leakage between the two wall surfaces under circumstances with a fluid pressure differential of up to about one atmosphere existing between opposite ends of said slider within said chamber. 38. A fluid-mechanical device operable selectively for the control of, and/or response to, certain fluid-flow conditions in different selected fluid-displacement applications, said device comprising a body foimed of a selected moldable material and including a fluid chamber which has, and is at least partially defined by, a fluid-impervious surface structure, a relative-motion element foimed of the same moldable material mentioned above and having a fluid-impervious surface structure for relative-motion, fluid-sealing, fluid displacement activity adjacent said chamber's said surface structure, and wherein such activity is characterized by a traveling line of fluid-sealing surfacial confrontation between said two surface structures, which line defines a fluid- sealed moving boundaiy for fluid present in said chamber, with respect to which fluid motion of that boundaiy, depending upon the direction of motion, effects positive or negative displacement of fluid with regard to the chamber, and wherein the sealed condition existing along said line is capable of sustaining, indefinitely, a non-leak- changing, fluid-pressure differential across the line of no less than about one atmosphere. 39. The device for paragraph of 38, wherein the line is endless. 40. The device of paragraph 38, wherein the motion is translational. 41. The device of paragraph 38, wherein the motion is sliding. 42. The device of paragraph 38, wherein the motion is rolling. 43. A fluid-displacement device, comprising: a molded body defining a cavity that contains a volume of fluid, and including an output port that allows communication between the cavity and a desired extrabody location; molded fluid-sealing/fluid-displacement structure fitted for relative movement within the cavity; and wherein, upon relative movement of the body and fluid-sealing/fluid- displacement structure, the device is selectively operable to prevent the volume of fluid from exiting the cavity via the output port, and to allow the volume of fluid to exit the cavity via the output port. 44. The device of paragraph 43, further including motion structure for causing the relative movement. 45. A fluid-displacement device, comprising: a molded body defining a cavity that contains a volume of fluid, and including an output port that allows communication between the cavity and a desired extrabody location; and molded fluid-sealing/fluid-displacement structure fittable and movable within the cavity to first and second positions, and selectively operable in the first position to prevent the volume of fluid from exiting the cavity via the output port, and in the second position to allow the volume of fluid to exit the cavity via the output port.

Claims: I CLAIM: 1. A volumetric-displacement-maximizing device, comprising: a molded body having an inner body surface defining an elongate fluid- containing cavity; a molded slider bidirectionally movable within the cavity, the slider having an outer surface that is located adjacent the inner body surface; and wherein an interfacial seal exists between the body and the slider, the seal having a first clearance threshold between the inner body surface and the outer surface, wherein the first clearance threshold has a corresponding first motion-causing force and the second clearance threshold has a second motion-causing force, and wherein each motion-causing force causes relative motion for a set of operating conditions, with the second clearance threshold being less than the first clearance threshold. 2. A fluid-displacement-maximizing device, comprising: a molded body foimed with an elongate fluid-containing cavity; a molded slider bidirectionally movable within the cavity; and wherein an alignment exists relative to the slider and the cavity, and the alignment is characterized by a first clearance threshold between the slider and the cavity with a coiresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a coiresponding second motion- causing force that is less than the first motion-causing force. 3. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to form a fluid-displacement device; and molding the fluid displacement device to include a slider and a fluid- containing cavity; and aligning the slider within the cavity so that alignment is characterized by a first clearance threshold between the slider and the cavity with a corresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a coiresponding second motion-causing force that is less than the first motion-causing force. 4. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; and molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity in such a way that there is a substantially time- indefinite, substantially leak-free, fluid-pressure condition that exists within the cavity. 5. The method of claim 4, wherein the molding step further includes molding in such a way that a substantially time-indefinite, substantially leak-free 15- psig fluid-pressure condition exists. 6. The method of claim paragraph 4, wherein the molding step further includes molding in such a way that a substantially time-indefinite, substantially leak- free 125-psig fluid-pressure condition exists. 7. The method of claim 5, wherein the molding step includes molding a cylindrical cavity that is up to about 1-inch in diameter. 8. The method of claim 6, wherein the molding step includes molding a cylindrical cavity that is up to about I -inch in diameter. 9. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to foim a fluid-displacement device; molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity; and making a seal between the slider and the cavity solely by aligning the slider within the cavity so that alignment is characterized by a first clearance threshold between the slider and the cavity with a coiresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a corresponding second motion-causing force that is less than the first motion-causing force. 10. A method of optimizing fluid displacement in a molded fluid- displacement device that displaces fluid by movement of a slider through a fluid- containing cavity, comprising: selecting moldable material to form a fluid-displacement device; molding the fluid-displacement device to include an elongate slider and an elongate, fluid-containing cavity; and making a seal between the slider and the cavity solely by molding the slider within the cavity so that the seal is characterized by a first clearance threshold between the slider and the cavity with a coiresponding first motion-causing force, and a second clearance threshold between the slider and the cavity with a corresponding second motion-causing force that is less than the first motion-causing force. 11. A fluid-mechanical device operable selectively in motor, pump and valve applications, such applications including, selectively, control of and response to fluid-flow conditions, said device comprising a non-machined body including an elongate fluid chamber having a long axis, and an elongate, inside wall surface circumsmrounding said axis, and an elongate, non-machined, movable slider having an outside surface disposed in a bare-clearance, reversible, sliding-fit condition within said chamber, and in contact with said wall surface in a manner circumsurrounding said axis, moveable reversibly within the chamber along said axis, said wall surface and slider surface contacting one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non- leak-changing, fluid-pressure differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere. 12. The device of claim 1 1, wherein the material foiming said body and that forming said slider each has substantially the same coefficient of theimal expansion. 13. The device of claim paragraph 12, wherein said body and said slider are formed of the same material. 14. The device of claim 13, wherein said material takes the foim of a moldable plastic material. 15. A fluid-mechanical device operable selectively in motor, pump and valve applications, such applications including, selectively, control of and response to fluid- flow conditions, said device comprising a molded body including an elongate fluid chamber having a long axis and at least partially defined by an elongate, cylindrical wall surface having a first radius of curvature and circumsunounding said axis, with said axis defining the center of circularity of said wall surface, and an elongate, molded, movable, cylindrical slider disposed in a bare- clearance, reversible, sliding-fit condition within said chamber, and including an outer, cylindrical wall surface having a radius of curvature which is slightly less than said first-mentioned radius of curvature, and which is in effective sealing contact with said body's said wall surface, said slider being movable reversibly within the chamber along the chamber's said axis, said body's said wall surface and said slider's said wall surface contacting one another in a mutually self-sealing condition, which condition is capable of sustaining, indefinitely, a non-leak-changing, pressure-fluid differential on the spaced opposite ends of the slider, which differential is no less than about one atmosphere. 16. The device of claim 15, wherein the difference in lengths between said two mentioned radii lies within a range not exceeding about 0.0003-inches. 17. The device of claim 15, wherein the difference in lengths between said two-mentioned radii lies within the range of about 0.0001-inches to about 0.0003- inches.

Applicants: PROTOCOL SYS INC, PROTOCOL SYSTEMS, INC.
Application year: 1998
Main classification: F01B9
IPC codes: F01B1, F01B9, F01B31, F04B1, F04B9, F04B19, F04B27, F16J10