Showing papers on "Piston published in 1999"

Compact pump drive system

Abstract: An improved pump is provided for controlled delivery of fluids wherein the pump includes a reservoir and a movable piston. A plunger slide is in removable contact with the movable piston. A motor is operably coupled to a drive member, such as a drive screw. The motor is disposed in-line with the drive member and the plunger slide. The drive member is operably connected to the plunger slide and is disposed to be substantially enclosed by the plunger slide when the plunger slide is in at least one position. The drive member is adapted to advance the plunger slide in response to operation of the motor.

Automatic injection device

Abstract: The present invention provides an auto-injection device including a housing, a container from which a product is dispensed by advancing a piston, the container shiftably accommodated by the housing and carrying a needle, and a drive unit including a driven member, wherein the driven member is shiftably accommodated by the housing and, during an auto-injection, is adapted for inserting the needle and advancing the container to a predetermined frontal position in relation to the housing and advancing the piston within the container for dispensing of the product, wherein the driven member remains uncoupled with the piston until the container reaches its frontal position, and upon the container reaching its frontal position, the driven member detaches from the container and couples with the piston for advancing the piston within the container

A numerical study of a free piston ic engine operating on homogeneous charge compression ignition combustion

Abstract: A free piston, internal combustion (IC) engine, operating at high compression ratio (~30:1) and low equivalence ratio (φ~0.35), and utilizing homogeneous charge compression ignition combustion, has been proposed by Sandia National Laboratories as a means of significantly improving the IC engine’s cycle thermal efficiency and exhaust emissions. A zero-dimensional, thermodynamic model with detailed chemical kinetics, and empirical scavenging, heat transfer, and friction component models has been used to analyze the steady-state operating characteristics of this engine. The cycle simulations using hydrogen as the fuel, have indicated the critical factors affecting the engine’s performance, and suggest the limits of improvement possible relative to conventional IC engine technologies.

Acoustic recovery of lost power in pulse tube refrigerators

Abstract: In an efficient Stirling-cycle cryocooler, the cold piston or displacer recovers power from the gas. This power is dissipated into heat in the orifice of an orifice pulse tube refrigerator, decreasing system efficiency. Recovery of some of this power in a pulse tube refrigerator, without sacrificing the simplicity and reliability inherent in a system with no cold moving parts, is described in this paper. In one method of such power recovery, the hot ends of both the regenerator and the pulse tube are connected to the front of the piston driving the refrigerator. Experimental data is presented demonstrating this method using a thermoacoustic driver instead of a piston driver. Control of time-averaged mass flux through the refrigerator is crucial to this power recovery, lest the refrigerator’s cooling power be overwhelmed by a room-temperature mass flux. Two methods are demonstrated for control of mass flux: a barrier method, and a hydrodynamic method based on turbulent irreversible flow. At −55 °C, the ref...

Blood separation system particularly for concentrating hematopoietic stem cells

Abstract: A system for separating biological fluids into components, comprises a set of containers (40, 42-44) for the biological fluid to be separated and the separated components, optionally an additional container (41) for additive solution, and a hollow centrifugal processing chamber (20) having an axial inlet/outlet (7) for the biological fluid. The processing chamber contains a piston (21) movable to intake a selected quantity of biological fluid and express processed biological fluid components via the outlet. Optical means (60-69) monitor the position of piston (21) to control the amount of intaken fluid and the expression of components. A distribution valve arrangement (45-48) selectively communicates the processing chamber (20) and the containers (40-44) or places them out of communication. The system is arranged to operate in a separation mode and in a non-separation transfer mode, especially for adding preservative solution to separated blood stem cells. In the separation mode, fluids are intaken into processing chamber (20), centrifuged and separated into components, and the components expressed possibly through the use of a density gradient product. In the transfer mode, the processing chamber (20) intakes and expresses fluid with the chamber stationary, the valve actuation arrangement (45-48) transferring fluid from one container (40-44) to another via the processing chamber (20), by movement of the piston (21), without centrifugation or separation, and the means (60-69) for monitoring the piston's position controls the amounts of non-separated fluids transferred.

Generalized theory of the photoacoustic effect in a multilayer material

Abstract: In this work, a generalized expression of the photoacoustic (PA) effect in a multilayer material is derived. This expression takes thermal and optical properties and geometry of a multilayer structure, as well as the thermal contact resistances between layers into consideration. In addition, a composite piston model consisting of a thermal piston and a mechanical piston of the PA effect is developed and interpreted from the viewpoint of thermodynamics. Mistakes occurring in the thermal piston model and in the composite piston model developed before are pointed out and corrected. It is also shown that the PA effect has an isochoric character for the thermal piston and a polytropic character with a polytropic factor of (2−1/γ) for the mechanical piston. The theory developed in this work is in good agreement with the experimental results, and is applicable to a wide range of photoacoustic problems.

Shock absorber with positive and negative gas spring chambers

Abstract: A gas spring shock absorber (10A) includes a damping fluid cylinder (14A) telescopically housed within an air cylinder (12A). A shaft (16A) connects a sealable, outer end (18A) of the air cylinder with a vented piston (32A) movably mounted within the damping fluid cylinder. A first fluid seal (60) extends from the gas cylinder and contacts the outer surface (38A) of the damping cylinder while a second fluid seal (34A) extends from the damping cylinder and contacts the inner surface (36A) of the gas cylinder. The fluid seals create a sealed variable-volume air chamber (40A) which is divided into air positive and air negative spring chambers (62,64). The air negative spring chamber is defined between the two fluid seals and automatically balances the force on the damping unit from the pressurized gas in the first air chamber portion. A bypass channel (66) is provided to permit fluid to bypass the second fluid seal and automatically equalize the pressure in the air positive and air negative spring chambers when the second fluid seal is aligned therewith.

Quasi-isothermal Brayton Cycle engine

Abstract: An engine is disclosed. According to one embodiment of the present invention, the engine comprises a compressor, and combustor, and an expander. The compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The expander receives the exhaust gases from the combustor, and expands the exhaust gases. The compressor may be a gerotor compressor or a piston compressor having variable-dead-volume control. The expander may be a gerotor expander or a piston expander having variable-dead-volume control. In another embodiment, an engine comprises a piston compressor, a combustor, a piston expander, and a pressure tank. The piston compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The piston expander receives the exhaust gases from the combustor, and expands the exhaust gases. The pressure tank receives and stores the compressed air from the compressor. In another embodiment, a gerotor compressor or a gerotor expander comprises an inner gerotor, and an outer gerotor. The inner gerotor and the outer gerotor are driven so that they do not touch. The gerotors may be cantilevered or non-cantilevered.

Magnetorheological fluid damper

Abstract: A novel and improved magnetorheological fluid damper is provided which effectively secures a flux ring to a piston core in a manner which prevents relative axial and radial movement between the flux ring and the core throughout operation while minimizing the size of the piston assembly yet providing effective damping. Several connector devices are disclosed for both axially and radially securing the flux ring relative to the piston core at one end of the piston assembly in a simple manner without increasing the length of the piston assembly. The connector device may include an outer portion brazed to the flux ring, an inner portion connected to the piston core, bridge portions extending between the outer and inner portions, flow passages formed between the bridge portions and an inlet cavity formed adjacent an annular flow gap to permit unimpeded, enhanced laminar flow through the flow gap by improving the damping effect. Other connector devices may include elongated rivets extending through the flow gap axially along the piston assembly, and elongated pin and spacer tube connectors extending radially between the piston core and the flux ring. Various embodiments of radial support devices are disclosed for possible use in combination with the connector devices to enhance radial support by, for example, the use of balls, a washer with tabs, a coil bobbin with tabs, rivets and axially extending elongated pins.

Use of electrodynamic drivers in thermoacoustic refrigerators

Abstract: Some issues involved in matching electrodynamic drivers to thermoacoustic refrigerators are examined using an equivalent circuit model. Conclusions are that the driver should be chosen to have a large product (Bl)2/(ReRm); the suspension stiffness should be chosen to make the combined impedance of the mechanical and acoustical parts of the system entirely real at the operating frequency; and the piston area should be selected to maximize electroacoustic efficiency, or other desired parameter, by matching the acoustic load to the optimum mechanical load for the particular driver. Alternately, if the piston area is fixed, the operating frequency can be adjusted to make this same match.

Multi-disk friction device having forced lubrication on demand

Abstract: A friction device includes a clutch pack operable to connect and disconnect drive and driven members for transferring and interrupting torque therebetween. A piston is supported in the clutch housing and defines a first expandable chamber. The piston is responsive to the pressure of fluid in the expandable chamber to move between disengaged and engaged positions thereby actuating the clutch pack. An outer ring is slidably supported within the housing to form a second expandable chamber. The outer ring includes at least one orifice extending therethrough. The piston closes the orifice in the outer ring when the drive and driven members are disconnected and has a second position where the orifice is open. A second source of lubricant pressure separate from the piston actuating fluid flows into the second expandable chamber thence through the orifice and from the outer diameter of the clutch pack between the adjacent plates and disks to the inner diameter of the clutch pack for cooling the pack.

Thermodynamics of systems with internal adiabatic constraints: time evolution of the adiabatic piston

Abstract: The equations for the time evolution of the controversial adiabatic piston problem are obtained using a very primitive model of the fluids. It thus shows that the first and second laws of thermodynamics lead to equations of motion which determine uniquely the final equilibrium state, while this state cannot be predicted using only the laws of thermostatics.

Fluid mechanics analysis of a spring-loaded jet injector

Abstract: A syringe jet injector is a device designed to administer a drug quickly and painlessly through the skin. Though syringe jet injectors have been in use for almost 50 years, current designs still suffer from inconsistent performance. To better understand the fluid mechanics of jet injection and gain insight into how the design might influence performance, two theoretical analyses to determine the fluid pressure profile at the exit orifice were conducted. The first was a continuum analysis assuming static incompressibility. Results demonstrated that the maximum jet pressure was highly sensitive to the spring constant, initial piston velocity, and piston cross-sectional area while the time to achieve the maximum pressure was most sensitive to the injection chamber length, initial piston velocity, bulk modulus of the injectant, and the piston cross-sectional area. The second analysis was a shock wave analysis. Results demonstrated a stepwise pressure-time plot that was similar in magnitude to that for the continuum analysis assuming static incompressibility. Results from these two investigations are useful for design modification of the jet injector to achieve desired pressure-time profiles at the orifice. Control of pressure-time profiles may help to achieve a more consistent and effective injection process.

Patient-controlled medication delivery system

Abstract: A portable, patient-controlled medication delivery system includes an infusion pump, a catheter assembly and an extension tubing set. The infusion pump retains a treatment fluid and provides a drive mechanism for delivering the treatment fluid to a patient. The catheter assembly has a medicine catheter which penetrates directly into the treatment site of the patient and the extension tubing set has an extension tube which connects the medicine catheter and infusion pump. The infusion pump includes a fluid reservoir, a dosage chamber, and a displacement piston displacable within the dosage chamber. An elastic member is also positioned in the infusion pump to exert a displacement force on the displacement piston. The elastic member is alternately transitionable between a more stressed position and a less stressed position. The elastic member elastically displaces the displacement piston in a first direction to expand the dosage chamber and draw the treatment fluid from the fluid reservoir into the dosage chamber when the elastic member transitions from the more stressed position to the less stressed position. The displacement piston is manually displaced in a second direction to contract the dosage chamber and discharge the treatment fluid from the dosage chamber to the treatment site when the elastic member transitions from the less stressed position to the more stressed position.

Device for connecting a receptacle and a container and ready-for-use set comprising same

Abstract: The invention concerns a connecting device (1) comprising a base (5) mounted on the receptacle (2) and extended by a flange (9) forming an inner bore (A) and a piston (10) capable of sliding in said inner bore (A) between a released position relative to a plug (4) and a transfer position wherein a hollow needle (11) borne by the piston (10) passes through the plug (4) A sealing lip (22) is arranged on an internal surface (8d) of the bore (A) opposite the piston (10) or on a surface of the piston, said lip (22) being shaped to be urged to press sealingly against the piston (10d) or against an internal surface of the bore, in the transfer position

High torque, low speed mud motor for use in drilling oil and gas wells

Abstract: A mud motor (100) for use in oil and gas well drilling includes a reciprocating valve and piston arrangement that generates power using drilling fluid media (e.g., drilling mud) pumped through an inlet port (118) to form a differential across a piston seat (46). The differential pressure causes the valve and piston assembly to move down in an elongated body (111). Rollers (138, 142) then force telescoping, reciprocating fingers (56, 57) to rotate while absorbing the reciprocating up and down action of the valve and piston assembly. This clockwise rotation causes a transmission that includes a clutch shaft (134) and sprags (146) to engage a clutch housing (135) causing the drill bit (17) to turn. Thrust bearings (156) allow weight to be applied to the tool (100) to optimize drilling action. The apparatus can be used in well drilling or in the removal of obstructions (14) such as bridge plugs, metal and rubber from the well bore.

An historical review of studies of polymeric seals in reciprocating hydraulic systems

Abstract: This is a historical review of the literature, outlining the development of our understanding of the factors affecting the performance of reciprocating polymeric seals, rod seals and piston seals, for fluid power systems. Particular attention is paid to early seminal studies many of the findings from which have become an accepted part of the technology while others are sometimes overlooked.

Design and testing of a novel linear alternator and engine system for remote electrical power generation

Abstract: This paper examines the design and operation of a novel generation system that utilizes a linear, crankless, internal combustion engine in conjunction with a linear alternator. This system directly utilizes the linear motion of the piston to drive the alternator rather than first converting to rotary motion. The result is a more efficient, compact and reliable unit as the system has only one moving part. This makes the system ideal for remote power generation. This paper describes the overall system design as well as the subsystems including the engine and the alternator. A dynamic simulation is then presented which utilizes the developed model to determine the output voltage of the system. The prototype system was successfully tested and experiment results are also included.

Stationary motion of the adiabatic piston

Abstract: We consider a one-dimensional system consisting of two infinite ideal fluids, with equal pressures but different temperatures T1 and T2, separated by an adiabatic movable piston whose mass M is much larger than the mass m of the fluid particles. This is the infinite version of the controversial adiabatic piston problem. The stationary non-equilibrium solution of the Boltzmann equation for the velocity distribution of the piston is expressed in powers of the small parameter e= m/M , and explicitly given up to order e2. In particular it implies that although the pressures are equal on both sides of the piston, the temperature difference induces a non-zero average velocity of the piston in the direction of the higher temperature region. It thus shows that the asymmetry of the fluctuations induces a macroscopic motion despite the absence of any macroscopic force. This same conclusion was previously obtained for the non-physical situation where M=m.

A roll control system for a motor vehicle

Abstract: A roll control system (20) for installation between axially aligned wheels of a motor vehicle, the roll control system comprising a torsion bar (22); a damper (24) attached to one end (28) of the torsion bar and attachable to one of the wheels; and attachment means (25) attached to the other end (29) of the torsion bar and attachable to the other wheel; wherein the damper comprises an axially extending cylindrical housing (52); a piston (34) slidably mounted inside the housing; a piston rod (58) connected to the piston, extending out of one end (55) of the housing, and movable in an axial direction relative to the housing; a floating piston (35) slidably mounted in the housing between the piston and the other end of the housing; a compensation chamber (37) between the floating piston and the other end (54) of the housing containing a first pressurised fluid; a compression chamber (30) between the floating piston and the piston containing a second pressurised fluid; a rebound chamber (32) between the piston and the one end of the housing containing the second pressurised fluid; valve means (36) on the piston allowing restricted flow of the second pressurised fluid between the compression chamber and the rebound chamber; a rebound stop (60) positioned in the rebound chamber between the piston and the one end of the housing and providing a spring-effect on the movement of the piston towards the one end of the housing; and a compression stop (62) providing a spring-effect on the movement of the piston towards the floating piston Provides an improved passive roll controle system

Magneto-rheological fluid device

Abstract: A magneto-rheological fluid device including a housing defining a cavity, a piston slidably disposed in the cavity to divide the cavity into first and second portions, a passage defined on an exterior surface of the piston fluidly coupling the first and second portions of the cavity, a magneto-rheological fluid disposed in the cavity such that motion of the piston is damped by flow of the magneto-rheological fluid through the passage and a magnet disposed to produce a magnetic field within the cavity substantially parallel to the motion of the piston at the exterior surface of the piston.

Monitoring of the pressure of a product fluid to be administered in dosed amounts during infusion or injection

Abstract: The invention relates to a process for the monitoring of the pressure of a product fluid to be administered in dosed amounts during an infusion or injection, which is dispensable from a container that is received in or formed by a housing, by advancement of a piston received in the container. The reaction force exerted by the piston onto the housing, which serves as a measure for the fluid pressure, is hereby measured and fed to a control for a drive of the piston. The control compares the measured reaction force with a predetermined reference force and controls the drive of the motor under consideration of the result of the comparison. The reference force is a nominal value for the reaction force and a direct nominal/actual comparison is carried out between the measured reaction force and its nominal value. The invention further relates to an apparatus which is especially suited for carrying out the process.

Osmotic delivery system having space efficient piston

Abstract: An osmotic delivery system having a space efficient piston. The capsule has an interior holding the piston, a beneficial agent, and an osmotic agent. The piston is movable with respect to an interior surface of the capsule, and defines a movable seal with the interior surface of the capsule. The movable seal separates the osmotic agent from the beneficial agent. The piston has a recess that receives at least a portion of the osmotic agent. The osmotic agent imbibes liquid from a surrounding environment through a semipermeable body to cause the piston to move and in turn cause delivery of the beneficial agent from the capsule.

Output control apparatus for linear compressor and method of the same

Abstract: An output control apparatus for a linear compressor and a method of the same are disclosed. In the conventional art, when controlling an output of the linear compressor using a stroke, it is possible to implement a constant stroke. However, since the intermediate position of the piston is varied, it is impossible to constantly implement a top dead point. Therefore, an output control of the linear compressor is difficult, and a higher efficiency is not easily implemented. In addition, there is a problem for constantly controlling an output of the linear compressor. Therefore, in the present invention, the timing when the piston and discharge valve collide with each other is determined, and a certain degree of stroke is determined as a control reference stroke based on the thusly determined stroke for thereby controlling the stroke and driving a linear compressor, and then the linear compressor is driven by controlling the stroke, so that it is possible control an output having no deviation in accordance with the system, whereby a higher efficiency operation is implemented irrespective of the size of the load.

Pump dispenser having a locking system with detents

Abstract: Lotion pump has a stepped piston telescoping inside a stepped body to define a pumping chamber. The piston has a downward annular wall having inlet and discharge apertures, one above the other, to the pumping chamber. A stem integral with the actuator has a sealing head inside the annular wall which shuttles up and down between positions at which it covers one aperture or the other. Shuttling is implemented by lost-motion between the actuator spout/stem and piston. A spring urges the stem up at all times. The actuator can be turned to lock the head over the discharge aperture by nullifying the lost-motion. Further turning can lock the stem in lockdown position. One-directional turnback can liberate the head and unlock the lockdown. Detents control sequence of unlocking.

Multi-dose infusion pump

Abstract: A multi-dose infusion pump employs a piston (20) sliding within the internal chamber (12) of a pump housing (10) to dispense liquid from a port (14). The peripheral surface (25) of the piston (20) has a sequence of steps (24, 26, 28) in a radial pattern spaced at intervals along the longitudinal axis of the chamber (12). A cap (50) is rotatably mounted to the pump housing (10) and includes a stop (52, 54) that limits forward movement of the piston (20) by engaging a selected one of the steps (24, 26, 28) on the piston (20) at each rotational position of the cap (50). This causes a series of predetermined quantities of liquid to be dispensed as the cap (50) is rotated to align the stop (52, 54) with each step (24, 26, 28) in sequence. A spring (40) between the cap (50) and piston (20) urges the piston (20) forward in the chamber (12) to dispense liquid from the port (14). The peripheral surface (25) of the piston (20) can also be equipped with a series of guide surfaces (34-36) that allow the piston (20) to be initially retracted toward the cap (50) without engaging the steps (24, 26, 28) while the cap (50) is in an initial rotational position, and then guide the stop (52, 54) along the steps (24, 26, 28) in a predetermined order as the cap (50) is rotated through a progression of rotational positions.

Positioning device and lithographic projection apparatus comprising such a device

Abstract: A positioning device comprising a first part and a second part which is displaceable relative to the first part by means of a system of Lorentz-force motors, whereby, relative to the first part, the second part is supported in a Z-direction by means of at least one gas cylinder, said gas cylinder comprising a housing having a pressure chamber, which housing is coupled to the first part; and a piston which is coupled to the second part and which can be displaced in the pressure chamber in the Z-direction, said piston being journaled relative to said housing substantially at right angles to the Z-direction.

Precision sensor for a hydraulic cylinder

Abstract: A sensor mountable within a hydraulic cylinder provides a precision signal indicative of the position of the piston. The sensor includes a flexible connector attached between the cylinder piston and a converting element for sensing the piston displacement. The converting element comprises a pick-up spool, under tension, coupled to the other end of the connector and rotatable about an axis. A lead screw engages threads on the spool, and translates linearly when the spool rotates. A non-contacting electromechanical transducer senses the position of the lead screw, and provides an output signal proportional to the motion or position of the movable element. The transducer may be an LVDT or other transducer. A high-pressure seal assembly provides an electrical path between the sensor and an external connector. A piston stop prevents the piston from damaging the sensor. The sensor is held within the cylinder by port inserts threaded into standard cylinder hydraulic fluid ports and advanced inwardly to grip the sensor.

Die casting pump

Abstract: An apparatus for pumping molten metal includes a pump base comprised of non-metallic, heat resistant material and adapted to be submerged in a bath of molten metal. The pump base includes a molten metal inlet opening; a molten metal valve chamber in communication with the inlet opening; a molten metal pumping chamber; a passageway that communicates the valve chamber and the pumping chamber and a molten metal outlet opening that communicates with the pumping chamber. A first piston made of non-metallic, heat resistant material is adapted for reciprocal movement in the valve chamber. A second piston made of non-metallic, heat resistant material is adapted for reciprocal movement in the pumping chamber. A first connecting member extends upwardly from the first piston and a second connecting member extends upwardly from the second piston. At least one actuator is in communication with the first and second connecting members. The at least one actuator acts upon the first and second connecting members to effect the reciprocal movement of the first and second pistons. When used in a die casting apparatus, also featured is a shot chamber disposed near the discharge opening for receiving molten metal discharged from the conduit. A ram is disposed in the chamber for injecting the molten metal in the chamber into a die for casting the molten metal.