Abstract: A displacement pump has multiple gas compression stages and serial gas flow through the compression stages. The gas is initially compressed in a first compression stage by a first fluid displacement member. The gas from the first compression stage flows to a second compression stage. The gas in the second compression stage is compressed by a second fluid displacement member and output from the pump.

Abstract: A remote caging system and method for remote caging for semi-trailer brakes is provided. The remote caging system comprises a remote control device, and a remote caging apparatus including a transmitter/receiver. The remote caging apparatus is installed on a semi-trailer truck brake. The remote control device sends and receives signals to and from the transmitter/receiver to engage and disengage the brakes.

Abstract: A spring brake actuator is for braking a wheel of a vehicle. The spring brake actuator has an axially elongated housing having a parking brake chamber and a service brake chamber; a main compression spring in the parking brake chamber; a flexible diaphragm in the parking brake chamber; and a pressure plate in the parking brake chamber, the pressure plate located axially between the main compression spring and the flexible diaphragm. The flexible diaphragm has a contoured portion that inhibits radial shifting of the pressure plate with respect to the flexible diaphragm.

Abstract: A robotic orthosis device for assisting users to rotate their wrist with a pair of fabric-based helical actuators and a sleeve or rigid interfaces configured to attach to a user's forearm. Each of the helical actuators includes a cylinder and a pneumatic bladder configured to inflate the cylinder. Each cylinder includes an anisotropic sheet material and a base sheet material running the length of the cylinder. The anisotropic sheet material comprises elastomeric strands that enable the material to stretch in a direction parallel to the orientation of the elastomeric strands, but different than the longitudinal axis of the cylinder. The base sheet material, which is affixed to the anisotropic sheet material, is strain-limiting along the longitudinal axis. When the bladder is pressurized, the expansion of the bladder causes the cylinder to stretch and twist, thus generating a helical force on the user' wrist relative to the elbow.

Abstract: A method is disclosed wherein two sheets of a flexible, inelastic substance are sealed along a periphery thereof, creating an interior reservoir preferably containing two or more elongate chambers, organized normal to an axis of traction. The disclosed axis of traction is an axis along which the disclosed device reduces length as a medium is introduced into the reservoir. Further disclosed is a method by which one or more bladders of flexible, inelastic substance are woven through two or more preferably parallel strips or strings. The bladders are adapted to receive a preferably gaseous or liquid medium. As the medium is moved into the bladders, the flexible strips or stings are deformed to cause the strips or strings to have a reduced length along the axis of traction.

Abstract: A sintered bearing includes a bearing main body which has a substantially cylindrical shape and is made of a sintered material, a through-hole being formed in a center of the bearing main body; a sealing member in a disk shape, the sealing member being configured to be disposed such that one surface side of the sealing member is in contact with the bearing main body, and an opening being formed in a center of the sealing member; and a locking member in a block shape, the locking member being configured to be in contact with at least another surface side of the sealing member and holding the sealing member between the locking member and the bearing main body.

Abstract: A method is disclosed wherein two sheets of a flexible, inelastic substance are sealed along a periphery thereof, creating an interior reservoir preferably containing two or more elongate chambers, organized normal to an axis of traction. The disclosed axis of traction is an axis along which the disclosed device reduces length as a medium is introduced into the reservoir. Further disclosed is a method by which one or more bladders of flexible, inelastic substance are woven through two or more preferably parallel strips or strings. The bladders are adapted to receive a preferably gaseous or liquid medium. As the medium is moved into the bladders, the flexible strips or stings are deformed to cause the strips or strings to have a reduced length along the axis of traction.

Abstract: A brake actuator assembly including a pressure plate presenting an opening, a push rod that is coupled to the pressure plate, a diaphragm that is coupled to the pressure plate, and a retainer that engages the push rod. The push rod has an outer surface and at least one protrusion extending outward from the outer surface. The retainer engages the protrusion such that at least a portion of the diaphragm is positioned between the pressure plate and the retainer.

Abstract: The invention relates to an ergonomic foot pedal and to apparatuses for manual ventilation. In an embodiment, the invention provides a compact and integrated foot pedal that enables a care provider to provide positive pressure ventilation to a subject's airways and lungs, and to optionally apply suction for the purpose of aspirating mucous, secretions, meconium, blood, fluids or other such materials from a patient—specifically from airways.

Abstract: A snivel suction device includes a base plate, two pump cylinders, two pistons, two connection rods, a pedal and two casings. Each pump cylinder is provided with a manifold containing a suction check valve and a release check valve. Two suction pipes are connected between a suction tee and the suction check valves of the manifolds. Two release pipes are connected between a release tee and the release check valves of the manifolds. A relief valve is installed at one of the casings. The relief valve has a knob, an adjustment member, a bolt, a valve body, a spring, a plug and a sound member. By operating the two ends of the pedal alternately, the two pistons are operated to suck and release air. Particularly, the relief valve can be actuated when a higher vacuum pressure has occurred in the suction pipes so as to protect the user's nasal mucosa.

Abstract: A soft composite actuator is described, including a first elastomeric layer; a strain limiting layer; and a first radially constraining layer, wherein the first elastomeric layer is disposed between the first radially constraining layer and the strain limiting layer; and the elastomeric layer, the strain limiting layer, and the radially constraining layer are bonded together to form at least one bladder for holding pressurized fluid. Methods of using and making of the soft composite actuator are described.

Abstract: The present invention includes methods and apparatuses for operating and controlling AOD pumps (10, 10?, 10?, 100, 460, 580, 740) and other pumps.

Abstract: A diaphragm device that supports a diaphragm with sandwiching an annular attaching portion, in an axis direction, provided at outer circumference of a flexible film by the support member having a diaphragm mounting portion, wherein at least three protrusions are provided at an outer circumference of the annular attaching portion, and each of the at least three protrusions equally protrudes in a radial direction, and wherein when the annular attaching portion is compressed in the axis direction, each of the at least three protrusions contacts with an inner circumference of the diaphragm mounting portion which faces an outer circumference of the annular attaching portion.

Abstract: Diaphragm assemblies for use with fluid control devices are described. An example diaphragm assembly includes a body defining a plurality of chambers to be fluidly coupled to an outlet pressure of a fluid control device. Each of the chambers is spaced along a stem at least partially disposed in the chambers, and the stem is to move to control a flow of fluid through the fluid control device. Additionally, the example diaphragm assembly includes a first plurality of diaphragms, each of which is disposed in a corresponding one of the chambers, and each of which is coupled to the stem to move the stem in response to the outlet pressure of the fluid control device.

Abstract: The present invention relates to an actuator system comprising one or more expansion chambers comprising one or more cylindrical chambers serially connected through a connection channel. The present invention further relates to the use of an actuator according to the present invention for providing a linear or other type of displacement.

Abstract: There is provided an abnormality determination unit that determines whether or not an output measurement unit is abnormal, in order to determine abnormality of the output measurement unit. When the output measurement unit is abnormal, the operation of an elastic actuator is controlled not in accordance with a measurement result of the output measurement unit but in accordance with an internal state model.

Abstract: A combined service brake and the stored-energy brake cylinder is provided, in which a ventilation valve which forms or shuts off a flow connection between the spring chamber and the service brake chamber of the brake cylinder ensures that disruptive noise is avoided while also preventing loss of air volume for building up the service brake force.

Abstract: A barrier of a vacuum pump prevents contamination from entering a vacuum pump air line. The barrier separates parts of the pump and is moveable between an initial state and a distended state. The barrier is assembled within the pump with a pre-load. When the vacuum source is applied to the barrier, the barrier achieves a distended state and when the vacuum source is released, the barrier incrementally self returns to an initial state. The geometry and material construction of the barrier, along with the pre-load, assists in returning the barrier on its own to the initial state from the distended state.

Abstract: A by-pass control system for a meat injection system has a variable speed pump that transports fluid to a meat injection machine. Excess fluid is transported to a by-pass control valve. The valve has a moveable piston disposed therein that separates the valve into a fluid chamber and an air chamber. The piston moves back and forth based on the relationship between fluid pressure and air pressure. Sensors are disposed within or through the lid or the valve to sense the position of the piston. A controller is connected to the sensors and the variable speed pump and adjusts the speed of the pump based on the position of the piston.

Abstract: Concepts and technologies described herein provide for the creation of an actuating fluid flow utilizing a multi-stage actuator. According to one aspect of the disclosure provided herein, a fluid actuation system includes at least two stages, each stage having a plenum and one or two diaphragms acting on the plenum to create an actuating fluid flow. The diaphragms of each stage may be substantially aligned along an axis. The actuating flow is aggregated between stages and expelled into a fluid flow to be controlled. According to various aspects, the diaphragms may include piezoelectric discs.

Abstract: The rubber compositions described herein have been found to have an exceptionally long life as a spring-biased actuator diaphragm material that maintains its position compressed, e.g., bolted, between opposed flanges, while maintaining excellent compressibility, low temperature flexibility, hydrocarbon resistance, abrasion resistance and mechanical strength. The compositions include a copolymer rubber component; a plasticizer for the copolymer rubber; a vulcanizing agent for the copolymer rubber; a silica filler; and a coupling agent, such as a silane coupling agent, capable of coupling the silica filler to the copolymer rubber.

Abstract: A brake actuator system of a vehicle comprising a diaphragm design with a hole and sealing element in the center. The design allows for the sealing element to seal and slide on the outer diameter of the center pushrod for the exposed length. This eliminates the need for a fixed joint to permanently attach the diaphragm to the center pushrod, and allows for the pushrod to be attached to the spring piston or a separate fixed plate and reduces stress of the diaphragm at its interface.

Abstract: A pump module for use in a medical fluid dispensing system is provided that includes a pump body having first and second portions where at least one of the first and second portions includes first and second fluid chambers. The module further includes at least one membrane operably associated with the fluid chambers, and first and second actuators operably associated with this membrane for the purpose of displacing the membrane and further for displacing fluid from the first and second chambers.

Abstract: An expansible chamber pneumatic system, for example a fluid pump system, includes two or more double-acting diaphragm pumps, each with symmetrical left and right pump housings, each housing including an air chamber and a fluid chamber separated by a movable diaphragm. The diaphragms are connected for reciprocating movement in unison to pump fluid through their respective fluid chambers. Each pump includes an air valve actuated by Control air to direct Process air into one of the air chambers, simultaneously releasing used Process air from the other air chamber to thereby move the diaphragms, thereby to pump fluid. A pilot valve directs Control air to the air valve to position the air valve. The pilot valve is responsive to diaphragms reaching their travel limit in one direction to direct Control air to reverse the directions of Process air flow through the air valve to thereby reverse the movement of the pump diaphragms. Control air exhausts through the pilot valve to atmosphere.

Abstract: In order to improve its durability, a fluid pressure type actuator is comprises an expansible/contractible body having opposite ends sealed by plug members and expands/contracts when fluid is supplied to and discharged from the body; a wrapping body for wrapping the outer peripheral surface of the expansible/contractible body and having its opposite ends fastened and fixed to the plug members; an inlet/outlet for fluid formed in the plug members; and an auxiliary member for preventing or suppressing local deformation in which the wrapping body expands outward when the fluid is supplied to the expansible/contractible body.

Abstract: An air driven diaphragm pump includes two diaphragms affixed to a common shaft. The shaft extends through an air valve providing reciprocating pressurized air to the diaphragms through associated air chambers. A pump chamber with intake and exhaust valves is associated with one of the two diaphragms while a further air chamber replaces a pump chamber and is associated with the other of the diaphragms. A passage extends through the shaft and is in communication with the air chamber adjacent to the pump chamber and with the further air chamber converted from the pump chamber.

Abstract: The rubber compositions described herein have been found to have an exceptionally long life as a spring-biased actuator diaphragm material that maintains its position compressed, e.g., bolted, between opposed flanges, while maintaining excellent compressibility, low temperature flexibility, hydrocarbon resistance, abrasion resistance and mechanical strength. The compositions include a copolymer rubber component; a plasticizer for the copolymer rubber; a vulcanizing agent for the copolymer rubber; a silica filler; and a coupling agent, such as a silane coupling agent, capable of coupling the silica filler to the copolymer rubber.

Abstract: A pump having a linearly movable shaft, a rotatable hub operably connected to the shaft, and shape memory actuator operably connected to the rotatable hub, and a fuel cell system including the same.

Abstract: A cellular actuator device suitable for a control surface of an aircraft or space craft has a number of elementary cells which are combined to a common arrangement and are formed by pressure-tight chambers. The elementary cells can be acted upon by a pressure medium and, when acted upon by the pressure medium, can be deformed in at least one work direction while changing their length. The elementary cells are coupled for combining their length changes in the at least one working direction to an overall movement of the elementary cell arrangement. The actuator device is particularly suitable for actuating a control surface of an aircraft or spacecraft.

Abstract: A tandem brake booster has a housing defined by a front shell that is joined to a rear shell to create an interior cavity. The interior cavity is divided by first and second diaphragm assemblies that are separated by a partition member to respectively isolate a first chamber from a second chamber and a third chamber from a fourth chamber. The first and third chambers are connected to fluid having a substantially constantly first pressure while the second and fourth chambers are connected to selectively receive the fluid at the first pressure or fluid at a second pressure. The partition member is characterized by a disc with a cylindrical body extending from a ledge formed on a peripheral surface of the disc and a flange located on the cylindrical body between the ledge and an end face of the cylindrical body.

Abstract: A membrane pump (104) with an operating membrane (1) delimiting a conveying space (2), and a supplemental membrane (3) arranged on the side of the operating membrane (1) facing away from the conveying space (2), with a membrane interspace (4) provided between the operating membrane (1) and the supplemental membrane (3) as well as with a pump drive for oscillating movement of the operating and the supplemental membranes (1, 3) in the same direction. The membrane interspace (3) is joined with at least one suction channel (7) for relieving pressure of the membrane interspace (4). The membrane interspace (4) is pneumatically joined through the at least one suction channel (7) with the suction side of this membrane pump (104). The membrane pump of the invention (104) has a high suction capacity without the problem of buckling of the elastic operating membrane (1) in the intake phase.

Abstract: A pair of flexible actuators according to the present invention is supported by a fixture made of a hard rubber at base ends of the flexible actuators. Each flexible actuator includes a movable unit that is capable of bending, a pump unit integrally connected to the movable unit at an end thereof, to control transfer of work fluid sealed in the movable unit, and a pump driver that controls driving of the pump unit. The movable unit includes two long and narrow tubes that each have an accordion wall, a core that maintains the tubes in parallel with each other, and a thin-film-bag-like cover that covers the tubes. The tube, which comes into contact with an object, is made of a soft material. The movable unit that is provided with the tube softly comes into contact with the object at a plurality of plane-contact portions of action of the movable unit, thereby holding the object without scratching the same.

Abstract: A pump that has a flexible liner located adjacent to a diaphragm. The liner provides structural support for the diaphragm. The flexible liner can slide relative to the diaphragm. This relative movement reduces the stiffness of the diaphragm/liner assembly. The diaphragm/liner assembly is therefore both flexible and strong. Additionally, the liner provides a thermal insulator for the diaphragm. The flexible liner may be constructed from a low friction material to lower the friction between the liner and a wobble plate of the pump. Lowering the friction reduces the heat generated within the pump. The structural reinforcement, thermal insulation and lower friction features of the liner increase the life of the diaphragm and the pump.

Abstract: A power booster for a brake system including a housing having an interior and a pair of diaphragms separating the interior of the housing into three chambers. A power piston assembly is coupled for movement with the diaphragms and includes an output member. A reaction member is coupled to the power piston assembly, and an input member is adapted to be coupled to a movable brake pedal. An air valve assembly moves between open and closed positions to selectively admit atmospheric air into selected ones of the chambers. This induces an output force on the diaphragm that is transferred to the output member of the power piston assembly. The triple booster adds an additional working chamber with an added approximately 45% increase in power boost. The triple power booster retains many of the same components as prior dual or tandem boosters to provide an economical solution to increase booster output without the need for new tuning procedures or added booster diameter.

Abstract: A fluid actuator applicable to high load with small space, comprising a core with an output shaft and two discs; and a cylinder casing which receives the core in a hollow, an upper end of the upper shaft projecting out of an upper opening and the core is set free. The cylinder casing includes an annular protrusion projecting into an air gap between the discs, wherein a small seal member which seals upper and lower spaces is provided between a portion of the core located between the discs and an annular protrusion and a large seal member which seals upper and lower spaces is provided between an inner peripheral surface of the cylinder casing, and an outer peripheral surface of the discs. The interior of the cylinder casing is divided into four small cavities abutting on one another vertically and an effective pressure-receiving area of the large seal member is larger than that of the small seal member to each of the small cavities.

Abstract: A motor vehicle tandem brake power booster with two booster units each including a vacuum chamber and a working chamber each arranged in a partition divided housing. The pressure difference between the pressure in the vacuum chamber and the pressure that can be influenced by a switching device in the corresponding working chamber in each booster unit acts on a piston separating the vacuum chamber from the working chamber. The forces, which are proportional to the pressure difference and act on the pistons are bundled via mechanical intermediate members by at least one transmission element each with the forces applied by the driver of the vehicle to a corresponding brake pedal.

Abstract: A power booster for a brake system including a housing having an interior and a pair of diaphragms separating the interior of the housing into three chambers. A power piston assembly is coupled for movement with the diaphragms and includes an output member. A reaction member is coupled to the power piston assembly, and an input member is adapted to be coupled to a movable brake pedal. An air valve assembly moves between open and closed positions to selectively admit atmospheric air into selected ones of the chambers. This induces an output force on the diaphragm that is transferred to the output member of the power piston assembly. The triple booster adds an additional working chamber with an added approximately 45% increase in power boost. The triple power booster retains many of the same components as prior dual or tandem boosters to provide an economical solution to increase booster output without the need for new tuning procedures or added booster diameter.

Abstract: A brake booster (10) comprising a housing (12); a diaphragm (16,18) mounted within the housing to define front and rear chambers (30-36) within the housing; and a cylindrical component (38) mounted within the housing and having an end (42) which passes through a sealing aperture (40) during installation within the housing to make a seal with the cylindrical component; wherein the cylindrical component has a plurality of fingers (46) extending away the said end, the fingers being circumferentially spaced apart around the end, and the outer surface (48) of each finger being chamfered such that the free ends (50) of each finger lie on a circle having an outer diameter (D1) which is less than the inner diameter (D2) of the sealing aperture prior to installation. Easier installation of the cylindrical component during booster assembly, especially where blind installation is required.

Abstract: A tandem vacuum servo unit includes a movable power piston having a supporting portion and a front movable wall member having a first engaging portion for engaging the movable power piston. The first engaging portion has an input side face that engages the output side face of the supporting portion along a first contacting portion. A rear movable wall member has a second engaging portion whose input side face engages the output side face of the first engaging portion along a second contacting portion. The first contacting portion is spaced radially outwardly of the second contacting portion. This construction of the vacuum servo unit increases the durability of the front movable wall member.

Abstract: A spring brake actuator (10), with a large-force compression spring (82) in a second spring chamber (78) of the housing, has vent openings (100) in the housing communicating with the second spring chamber (78). A filter assembly (134) covers the vent openings (100). Weep holes (62), (104), (102), and (100) in a sleeve (50) of an push rod (18), in a spring brake actuator rod (84), and in a spring brake housing portion (68) together permit fluid compressed in a first service brake chamber (30) to flow through a conduit define by these weep holes out of the brake actuator (10) wherein it is filtered by the filter assembly (134).

Abstract: A multiple diaphragm actuator for exerting linear forces of precise and repeatable amounts in opposite directions with no friction and no fluid leakage.

Abstract: A tandem brake booster having a housing with a first front chamber separated from a first rear chambers by a first wall and a second front chamber separated from a second rear chamber by a second wall. The first and second front chambers are connected to the first and second rear chambers through passages in a hub which retains a control valve. In a first or ready mode of operation, the first and second front and rear chambers have a substantially identical first fluid pressure while in a second or actuation mode of operation, the control valve responds to an input force to allow a second fluid pressure to be communicated to the first and second rear chambers and create a pressure differential with the first fluid in the first and second front chambers. The pressure differential develops an output force which moves the first and second walls as a function of the input force applied to the control valve.

Abstract: A power booster includes a housing with a rear housing section and a front housing section defining an internal cavity. A housing wall separates the internal cavity into a first chamber and a second chamber with an opening formed in the housing wall, wherein it is desirable to extend a component through the opening. A tube has an end secured in the opening in the housing wall. The tube's end includes a radially directed wall extending from the end of the tube that extends to an axially extending wall positioned concentrically with the tube and terminating with an outwardly turned segment. The axially extending wall is positioned within the opening in the housing wall with a seal positioned between the axially extending wall and the housing wall wherein the distance between the front housing section and the rear housing section is minimized, by extending the component through the tube.

Abstract: A tandem pneumatic booster having a shell body, the inside of which is divided into two, front and rear, chambers by a center shell. Each chamber includes a negative pressure chamber and a working pressure chamber. A valve body is slidably fitted in the shell body and the center shell with seal members therebetween. The valve body is provided with an air passage for communication between the front and rear working pressure chambers. A valve mechanism is actuated in association with an input shaft to introduce atmospheric air into the front and rear working pressure chambers through the air passage so as to apply thrust to front and rear power pistons. The diaphragm of the front power piston has a bead on an inner periphery thereof. The valve body has a groove on an outer periphery thereof. A portion of the air passage which leads to the front working pressure chamber has a main passage portion extending axially in the valve body, and a bypass extending radially outward from the main passage portion.

Abstract: An automatic brake booster having the functioning of an automatic brake, or more specifically, an improvement of bellows contained in a shell thereof is disclosed. The bellows comprises a stepped tubular member having portions of different diameters, namely, a reduced diameter, a medium diameter and an increased diameter. By using a reinforcing ring having a rigidity in the step, an expansion to increase the diameter of the bellows when the atmosphere is introduced into the internal space of the bellows can be prevented. Different diameters of the portions of the bellows allows the likelihood to be minimized that an output loss of the brake booster may be caused by contact of bellows portions to each other as the bellows is axially shrunk. As compared with an accordion-like bellows, the stepped tubular bellows can utilize a simplified die assembly and manufacturing steps and thus can be manufactured inexpensively.

Abstract: An apparatus generates power at micro-scale dimensions that is sufficient to simulate the muscle activity required by the joints of robotic fingers. The apparatus includes a bellows device for generating a motion stimulus in response to pressure changes within the bellows. A configuration of programmable micromachined valves is used to regulate the flow of pressurized fluid within the bellows. A microprocessor is responsive to motion commands for controlling the operation of the apparatus. The apparatus is configured as an integrated device that is coupled to the articulations of a robotic hand via suitable attachment mechanisms.

Abstract: To prevent a rolling diaphragm (13), which forms the movable wall (4) of a vacuum brake booster along with a metallic diaphragm disk (12), from becoming detached from an annular groove (52) accommodating a radially inner bead (32) of the rolling diaphragm (13), the rolling diaphragm is connected to the edge of the bead (32) located away from the (first) diaphragm disk (12). By connecting the rolling diaphragm (13) to the edge of the bead (32) located away from the (first) diaphragm disk (12), a pneumatic space (27) is defined by the rolling diaphragm (13) and the (first) diaphragm disk (12). Pressure occurring in the vacuum chamber(s) (28, 30) can be admitted to the pneumatic space (27).

Abstract: A tandem vacuum booster includes a front shell and a rear shell which are connected to each other to form a housing, a front movable wall having an outer circumferential portion that is fit in a fluid-tight manner between the front shell and the rear shell, and a rear movable wall having an outer circumferential portion that is fixed to the rear shell. A fixed wall has an outer circumferential portion that is fit between the front movable wall and the rear shell, with the fixed wall including a bent portion which presses the outer circumferential portion of the rear movable wall to the rear shell.

Abstract: A long-stroke fail-safe spring brake assembly for heavy duty vehicles comprises aligned first and second cups secured adjacent one another to form a housing for a compressed power spring which biases a spring piston, a hollow tubular push rod having one end open and sealingly secured, preferably by press fitting, to the spring piston and the other end closed and extending sealingly through the second cup for reciprocal control of a brake actuator by the power spring, an annular-shaped flexible diaphragm having an outer periphery radially-sealingly secured adjacent between the cups and an inner periphery sealingly secured adjacent the outer periphery of the spring piston, the intermediate portion of the diaphragm being disposed radially-outwardly of the spring piston. The spring piston is disposed to compress the compressed spring still further toward the first cup under the influence of a compressed fluid medium, the push rod, and the spring piston being sealingly secured to each other.

Abstract: A fluid-operated brake actuator having a hollow actuator rod between a spring chamber of a spring brake housing and a spring chamber of a service brake housing incorporates a valve within the actuator rod. The valve isolates the two spring chambers from each other in normal operation and releases a vacuum in the spring brake housing spring chamber when the spring brake is activated. A separate one-way check valve mounted in a well of the spring brake housing permits fluid to exhaust from the spring chamber to atmosphere and prevents contaminants in the atmosphere from entering the spring chamber.