Abstract: A hands-free breast pump that includes a balanced push-pull reciprocating drive system that applies pumping force to a vacuum chamber formed by a breast interface cup during inward and outward pump strokes. The breast pump includes a breast cup that has a resilient bellows structure that partially collapses the volume of the vacuum chamber during the inward stroke and recovers the volume of the vacuum chamber during the outward stroke. The pump mechanism includes a cam drive system that translates rotary electric motor power into reciprocating linear action of an actuator arm that drives the bellows structure. The bellows structure acts like a spring that charges (resists the pump force) during the inward stroke and discharges (assists the pump force) during the outward stroke, and the shape of the cam track is designed to produce a desired operating profile for the pump.

Abstract: A motorised head (3) for a breast pump comprising a motor unit (35) including a motor and a drive mechanism (22) for driving a pump, a body mounting portion which is fixedly mountable to a body of a breast pump, a motor mounting portion (39) on which the motor and drive mechanism (22) are disposed, and a resiliently deformable member (49) connecting the body mounting portion and the motor mounting portion such that the resiliently deformable member reduces the transfer of vibration caused by the motor or drive mechanism to a breast pump body to which the body mounting portion is mounted.

Abstract: In an apparatus for recognizing couplings between a first and a second component of a system, one of the two components is provided with an identification unit. A checking unit is operatively connected to the second component. The identification unit contains an item of information relating to the first component. The checking unit is designed for recognizing and processing this item of information. The checking unit moreover is designed such that, as a function of a result of the processing of the item of information, it allows or prevents coupling between the first and the second component. This apparatus enables a combined use of system components only in the case of an admissible coupling thereof.

Abstract: A breast receiving funnel (5) for a breast pump (1) comprising an expandable layer (18) formed from a hydrogel which is configured to expand such that an inner surface of the breast receiving funnel (5), against which a user's breast is locatable, swells towards said user's breast to apply a positive pressure thereto and aid the expression of milk therefrom.

Abstract: Inner and outer shield parts of a breastshield are joined to form an enclosure defining a pressurizable chamber. The inner shield part has at least a portion thereof movable relative to the outer shield part when the chamber is subject to a negative or a positive pressure. A first pressure port is in communication respectively with the chamber for connection with a fluid pressure source of a first pressure. A second pressure port is in communication with the interior for connection with a pressure source of a second pressure. The breastshield is thus capable of being subjected to two different pressures, such as a positive pressure to move (expand) the chamber into the interior, so as to compress or massage the nipple/breast, and a negative pressure in the interior to draw the nipple/breast further therein for the expression of milk. The pressures can be independently controlled.

Abstract: A breast cup assembly for a breast pump has a generally funnel-shaped support member with an open wide end, an open narrow end, a tapered central passage extending between the wide end and the narrow end. A liner is positioned at least in part in the support member. The liner has a first noncircular opening therein for receiving at least a portion of a breast including a nipple, a second opening spaced from the first noncircular opening, and a tubular passageway between the first noncircular opening and the second opening for allowing milk expressed from the breast received in the liner to pass through the liner. The liner is configured for movement between an opened configuration of the noncircular opening and a collapsed configuration of the noncircular opening.

Abstract: A breast pump system (1) comprises a breast pump arranged to extract milk from a user; and a breathing guidance means configured to provide a suggested breathing pattern to the user. The breathing guidance means may be produced by a motorised breast pump unit (10), or may be a series of stimuli at a stimuli frequency, which are perceivable by the user. The system (1) may include a heart rate monitor for measuring the heart rate of the user, and the suggested breathing pattern may be coupled to the measured heart rate.

Abstract: A milk extraction device including at least one extraction part with an intermediate piece that is, or can be, detachably fastened on the opening of a receptacle and that is linked with a breast piece in a vacuum-tight manner so as to exert a sucking effect on the breast. The device also includes a cap that is, or can be, linked with the intermediate piece in a vacuum-tight manner. An elastic, liquid-tight separating membrane is inserted in the cap and transmits a varying vacuum from the pump unit to the interior of the intermediate piece and the breast piece. The cap is detachably connected to an adapted coupling section of the intermediate piece by a coupling counter-section, thereby meeting increased hygienic standards and simplifying the use of the milk extraction device.

Abstract: The connector of the present invention provides fewer connections and attachments to a breastpump configured for expressing breast milk from both of a woman's breasts simultaneously, thereby facilitating easier use of the breast pump and yielding fewer pieces for the user to carry or misplace. The connector includes a manifold with four ports. Individual tubes extend from three of the four ports and each has a plug member. One tube engages with a vacuum source and the remaining two tubes engage with a breastshield assembly for double breast pumping. When single breastpumping is desired, one of the two tubes connected to the breastpump assemblies is disconnected and engaged with the dock port of the manifold.

Abstract: The present invention provides a breastshield for use in a breastpumping system for expressing milk, the breastshield being of such a construction that substantially limits the amount of air between the breast/nipple and the breastshield surrounding the breast/nipple, and most preferably virtually eliminates any air at least in the area of the breast and nipple. In some embodiments, any air in the breastpumping system is substantially eliminated. With the amount of air limited, the mechanism used for generating the pressure difference in the breastshield (e.g., vacuum or negative pressure), such as a diaphragm pump, does not need to do as much work. Less energy is required for the expression of milk, and thus the size of pump used can be decreased, thereby reducing the overall cost of the device.

Abstract: The present invention provides a device and method for measuring the amount of milk supplied to a feeding infant. The device (10) comprises a cap (13) having a nipple-shaped region (10) with an inner surface (14) and an outer surface (16) and a duct (18) extending therebetween. The duct has an inlet (20) at the inner surface and an outlet (22) at the outer surface. The cap is adapted to be mounted on the nipple region of a woman's breast with the inner surface facing the woman's breast and to allow breast-milk to pass through the duct. The device further comprises a sensor (24) associated with the duct for measuring at least milk volume passing through the duct and providing data indicative of the volume.

Abstract: A breastpump is provided with one or more novel suction sequences which are considered to produce advantageous particularized results. Such sequences include a suction method for increased milk production and an improved suction method in general.

Abstract: An adapter for use in connecting a vacuum source with a breast shield is disclosed including a housing with at least one female coupling component formed therein, at least one male coupling component that is adapted to attach to a tube at one end for conveying pressure from the vacuum source, while the other end is sized and shaped to be received in the female coupling component. A passageway extends between the first end and the second end of the male coupling component for conveying the pressure. The female coupling component is defined therein by an interior sidewall that has a channel formed therein open to the female coupling component at least somewhere along the interior sidewall. When the male coupling component is inserted in the female coupling component, a sealing portion of the male coupling component engages the interior sidewall surface such that ambient air is prevented from entering the channel and disrupting optimal vacuum pressure.

Abstract: The invention relates to a disposable breast cup set which comprises a coupling element (2) to be coupled to a milk collection receptacle (1) and a breast cup connecting element (3) to be coupled to a breast cup funnel (5). The coupling element (5) and the breast cup connecting element (3) are interlinked via a tamper-evident element (4), said connection being destroyed when the coupling element (2) is for the first time separated from the breast cup connecting element (3) and preventing re-use of the set.

Abstract: A device for treatment of engorgement or edema of the breast has an orifice within which a breast nipple is received, a force-applying surface that presses against the adjacent breast to push fluid away from the nipple, and a part to which a motive force is applied to press the force-applying surface against the breast. The device can be used manually, worn within a bra, or used with a breastshield of a breastpump.

Abstract: The present disclosed subject matter provides a breast pump in which, by means of an operation performed by a user, the negative pressure (suctioning pressure) can be adjusted in accordance with the amount of the operation in a linear fashion without the occurrence of a steep gradient, and the negative pressure can be readily adjusted even during the expression of milk.

Abstract: Breast pump for expressing milk from a breast, comprising at least one breast cup (2) for receiving a breast, a pumping system (10) in fluid connection (11) with the at least one breast cup (2) for applying a negative pressure on said breast and a detection unit (3) comprising at least one sensor for measuring a parameter during use of the breast pump (1), wherein the breast pump (1) is adapted for optimising breast pump settings by actively controlling at least one breast pump pumping property, based on measurements of the at least one sensor (4, 5), during a period of use of the breast pump (1), in order to personalise operation of said breast pump (1) for a particular user.

Abstract: A breast milk collection apparatus includes a milk collection bottle, a breast shield, and a suction transfer assembly for mounting on the bottle. The suction transfer assembly includes a housing for connecting to the vacuum pump and the breast shield. Included in the suction transfer housing is a reversible diaphragm made of a deformable elastomeric material configured with a spiral undulatory configuration. The breast shield includes a unitary funnel member from a relatively rigid polymer as well as an annular deformable lip for enhanced comfort. In one preferred construction, a pump enclosure defines a well for receiving a bottle with deformable gripping projections which adapt to changes in bottle size.

Abstract: An electronically controlled breast pump for generating cyclical suction includes a cumulative vacuum pump and a plurality of switches including at least an expression mode cycle time selection switch, a peak vacuum level selection switch, and a stimulation mode switch. A controller coupled to the cumulative vacuum pump controls the apparatus which optionally further includes a four-layer assembly of the various features, an adjustable safety valve, and/or a pump head with a groove traversing top dead center of the pump head.

Abstract: A manual breast pump, including a housing; a funnel connected to the housing and forming a passage for breast milk; a cup for receiving a breast; a lid connected to an upper portion of the housing; a handle assembly connected to the lid; a substantially semi-circular finger grip connected to the housing; a piston movably connected to the handle assembly and reciprocally movable within the housing to create a negative pressure for the expression of breast milk from the breast; a flexible insert sealably secured to the cup and forming an isolated air volume between the cup and the flexible insert. A valve is removably connected to a lower portion of the housing; and a receptacle for receiving the breast milk, the receptacle being removably attached to a lower portion of the housing. The isolated air volume expands and contracts as the piston moves reciprocally within the housing, causing the flexible insert to move.

Abstract: A manually actuated breast pump is provided. The breast pump has a breast cup, pump mechanism and a container. The components of the breast pump are easily assembled and disassembled to facilitate use, cleaning, manufacture and transport. The breast pump can apply a negative pressure, a positive pressure or both to a user's breast. The breast pump provides fluid isolation between the pressure source and the expressed milk.

Abstract: The present invention relates to a breast pump including a cylindrical housing encapsulated by an insulated thermal layer; the housing includes an outer wall and an open top in communication with an interior chamber. Superimposed on the open top is a removable pump assembly having a pair of outlet tubes extending therefrom. At a distal end of each tube is a conical suction cup for placing over a nursing mother's breast nipple. Any one of a plurality of varying sized auxiliary containers, such as a conventional baby bottle, can be placed within the interior chamber to receive and store breast milk extracted from the breasts.

Abstract: A breast pump comprises a breast cup and a source of positive and vacuum to the breast cup. The pressure and vacuum are set to an initial value for a fixed period of time, and they are not adjusted by a user. The initial values are selected to allow the breast cup to be repositioned by a user before higher levels of pressure and vacuum are applied.

Abstract: A hands-free breast pump that includes a balanced push-pull reciprocating drive system that applies pumping force to a vacuum chamber formed by a breast interface cup during inward and outward pump strokes. The breast pump includes a breast cup that has a resilient bellows structure that partially collapses the volume of the vacuum chamber during the inward stroke and recovers the volume of the vacuum chamber during the outward stroke. The pump mechanism includes a cam drive system that translates rotary electric motor power into reciprocating linear action of an actuator arm that drives the bellows structure. The bellows structure acts like a spring that charges (resists the pump force) during the inward stroke and discharges (assists the pump force) during the outward stroke, and the shape of the cam track is designed to produce a desired operating profile for the pump.

Abstract: An adapter for use in connecting a vacuum source with a breast shield is disclosed including a housing with at least one female coupling component formed therein, at least one male coupling component that is adapted to attach to a tube at one end for conveying pressure from the vacuum source, while the other end is sized and shaped to be received in the female coupling component. A passageway extends between the first end and the second end of the male coupling component for conveying the pressure. The female coupling component is defined therein by an interior sidewall that has a channel formed therein open to the female coupling component at least somewhere along the interior sidewall. When the male coupling component is inserted in the female coupling component, a sealing portion of the male coupling component engages the interior sidewall surface such that ambient air is prevented from entering the channel and disrupting optimal vacuum pressure.

Abstract: The connector of the present invention provides fewer connections and attachments to a breastpump configured for expressing breast milk from both of a woman's breasts simultaneously, thereby facilitating easier use of the breast pump and yielding fewer pieces for the user to carry or misplace. The connector includes a manifold with four ports. Individual tubes extend from three of the four ports and each has a plug member. One tube engages with a vacuum source and the remaining two tubes engage with a breastshield assembly for double breast pumping. When single breastpumping is desired, one of the two tubes connected to the breastpump assemblies is disconnected and engaged with the dock port of the manifold.

Abstract: A disclosed reclining breast pumping system includes a breast shield that forms a passageway. Material of the breast shield adjacent to a first end of the passageway is shaped to fit over an area surrounding the areola and nipple of a woman's breast. Material of the breast shield that extends from a second end of the passageway is formed into a tube. When the breast shield is fitted onto a woman's breast, the part of the passageway closest to but not touching the nipple of the breast extends in a direction that is non-perpendicular to the areola. Variations and methods are also disclosed.

Abstract: An apparatus (1) for extracting milk from a breast, comprising means (2,3) for receiving at least a portion of a breast and its nipple; a container (5) for collecting the milk operatively connected to said means (2,3) for receiving at least partially a breast and its nipple; a pump unit (100) operatively connected to said means (2,3) for receiving at least partially a breast and its nipple, said pump unit (1009 being operated manually to generate at least an aspiration able to cause a suction on the breast by imposing a predetermined degree of vacuum within said means for receiving the breast and the nipple. The manually operated pump unit (100) comprises means for regulating the degree of vacuum that is generated. Pump unit (100) operated manually and connectable to a kit for collecting milk from a breast.

Abstract: A device that supports a breast pump in a “hands-free” manner is disclosed. The device includes a cover with an opening and strap that connects the cover to an article of clothing such as a nursing bra. When connected, the device securely orients a breast shield of a breast pump over the breast of a user.

Abstract: A manual breast pump, including a housing; a funnel connected to the housing and forming a passage for breast milk; a cup for receiving a breast; a lid connected to an upper portion of the housing; a handle assembly connected to the lid; a substantially semi-circular finger grip connected to the housing; a piston movably connected to the handle assembly and reciprocally movable within the housing to create a negative pressure for the expression of breast milk from the breast; a flexible insert sealably secured to the cup and forming an isolated air volume between the cup and the flexible insert. A valve is removably connected to a lower portion of the housing; and a receptacle for receiving the breast milk, the receptacle being removably attached to a lower portion of the housing. The isolated air volume expands and contracts as the piston moves reciprocally within the housing, causing the flexible insert to move.

Abstract: The device according to the invention for connecting a suction hose has a connecting piece which is designed in such a way that the suction hose can be pushed over a region of the connecting piece in a sealing manner. The device also comprises a sleeve which can be pushed over the aforementioned region of the connecting piece, at least partially covering said piece and leaving room between the sleeve and the connecting piece for the suction hose. The connection between the sleeve and the connecting piece can only be separated by the destruction of at least one of said two parts. The design of the exterior of the sleeve prevents a second suction hose from lying in a sealing manner against the sleeve. A suction hose that is connected in a sealing manner to the claimed device can therefore not be removed without destroying the device. In addition, it is impossible to push a hose with a greater diameter onto the sleeve in a sealing manner.

Abstract: A portable, hands-free and user friendly breast pump for facilitating breast-feeding, incorporates a dome-shaped housing having a servomotor mechanism; a hat-shaped flange having a chamber portion, a brim portion and an outlet, the chamber portion being formed so as to be placed over a nipple on a breast so as to define a chamber between the flange and the breast, and the brim portion being formed to surround the nipple and thereby form a suction seal therebetween; and a one-way venting element formed to operatively communicate with the chamber so as to vent pumped milk from the chamber via the outlet. The housing, the flange and the venting element are connected into an integral device held against the breast and underneath clothing so as to keep the integral device hidden. Breast milk is collected via a plastic collection bag that connects directly with the pump underneath clothing such that the milk is isolated from any contaminants in the air and may be easily stored immediately after being collected.

Abstract: A portable, hands-free and user friendly breast pump for facilitating breast-feeding, incorporates a dome-shaped housing having a servomotor mechanism; a hat-shaped flange having a chamber portion, a brim portion and an outlet, the chamber portion being formed so as to be placed over a nipple on a breast so as to define a chamber between the flange and the breast, and the brim portion being formed to surround the nipple and thereby form a suction seal therebetween; and a one-way venting element formed to operatively communicate with the chamber so as to vent pumped milk from the chamber via the outlet. The housing, the flange and the venting element are connected into an integral device held against the breast and underneath clothing so as to keep the integral device hidden. Breast milk is collected via a plastic collection bag that connects directly with the pump underneath clothing such that the milk is isolated from any contaminants in the air and may be easily stored immediately after being collected.

Abstract: A manual breastpump has a pump mechanism for use in one mode of operation to produce an ejection (letdown) reflex in a nursing mother and in a separate mode of operation for the general expression of breastmilk. The breastpump further provides a pump mechanism having an expansible chamber device carried by the handle, which is operated by moving the handle relative to a handle mount. A double-pivot for the handle yields letdown mode as well as the general pumping mode.

Abstract: The present invention provides a suction sequence which is considered to produce advantageous results, particularly for mothers with newborn infants. The sequence comprises a process of stimulation, expression, and pausing to closely mimic a newborn's sucking pattern.

Abstract: A breast cup for use with a breast pump for expressing breast milk is provided. The breast cup sealingly separates the air flow from the breast milk, provides a barrier against impingement of the flexible insert by the user's breast and provides a massaging member for facilitating expression of the breast milk.

Abstract: A manually actuated breast pump is provided. The breast pump has a breast cup, pump mechanism and a container. The components of the breast pump are easily assembled and disassembled to facilitate use, cleaning, manufacture and transport. The breast pump can apply a negative pressure, a positive pressure or both to a user's breast. The breast pump provides fluid isolation between the pressure source and the expressed milk.

Abstract: The invention relates to a breast cap part for a breast pump, which is disposed on an areola of a female breast when used. The breast cap includes a truncated base body (1) having a large rear opening (13) and a small front opening (14), the base body being embodied in order to receive a breast cap (6) in a funnel. The truncated base body (1) is at least partially made of a heat accumulating and/or heat conducting material and is heated when required. The heating does not exclusively occur when the body temperature of the female breast is transmitted. Other means for heating the breast cap part are used.

Abstract: A milk pump for pumping milk from a woman's breast comprises a breast hood for receiving tightly a woman's breast. Furthermore, there is a milk collecting arrangement for receiving milk pumped from said woman's breast. This milk collecting arrangement includes a support and a downwards directed opening in the support for providing a suction communication to the breast hood. Moreover, the milk collecting arrangement comprises a manual pumping unit above the said opening. The manual pumping unit includes a wall forming and surrounding a displacement space which comprise a front wall and a peripheral wall extending in longitudinal direction. A suction device is displaceable inside the displacement space to provide suction through the opening, wherein the displacement is provoked by an actuation device. Furthermore, there is a latching arrangement for releasably connecting at least part of the wall of the displacement space to the support for an easy exchange.

Abstract: The present disclosure provides a breast pump support for securing first and second milk intake components of a breast pump to the nipples of a user's breasts. The breast pump support includes an elongated band securable around the user's chest. The elongated band is defined by at least first and second opposing pieces of folded over elastic material having first and second elongated folded edges. The first and second elongated folded edges are secured to one another along their length except for along first and second sections defining first and second openings in the elongated band. The breast pump support may further include first and second means for reinforcing the elongated band adjacent to the first and second openings.

Abstract: A breast pump can include a breast pump main body having a milking portion and negative pressure generating structure for generating negative pressure. The milking portion can include a shape maintaining portion and a negative pressure generating portion that serves as a part of the negative pressure generating structure and can be attached to and detached from an inner side of the shape maintaining portion. At least one end of the negative pressure generating portion on an enlarged diameter side can include a flexible diaphragm portion and a pressing portion formed when a folded-back portion of the diaphragm portion passes an imaginary line of extension of a contact portion contacting the breast to press the breast, while the other end of the negative pressure generating portion is connected to the opening/closing structure.

Abstract: A hand held breast pump comprises a powered head (1), a body (7) including a diaphragm pump, a breast engaging portion (23) and a bottle coupling (24). The powered head (1) may be exchangeable for a manual head (4).

Abstract: A breast pump, including a housing container, a breast pump body having an attachment and detachment part, a negative pressure generating member attached to the breast pump body, and an operation unit. The breast pump body includes a diameter-expanded milking part, a small valve chamber, and an attachment part communicating with the small valve chamber and attaches thereto the negative pressure generating member that creates the negative pressure needed to express milk; the negative pressure generating member includes a connector to which the operation unit is connected, a comparatively soft attachment and detachment part having elasticity and attached detachably to the attachment part, a wall part having such rigidity that an external shape can be kept, and a deformable part provided on the inside of the wall part integrally with the wall part, is less thick than the wall part, and is deformed to create the negative pressure.

Abstract: A chair powered breast pump apparatus has at least one breast shield adapted to fit over a nipple of a breast, a pump having a stationary portion and a reciprocating portion engaged for reciprocating movement, one or more suction lines connected in series between the stationary portion and the breast shield, a first connecting bracket configured to secure the reciprocating portion to a first portion of a chair movement mechanism, and a second connecting bracket configured to secure the stationary portion to a second portion of a chair movement mechanism, the first and second portions being relatively movable, whereby movement of the chair by a user seated in the chair reciprocates the reciprocating portion in and out of the stationary portion so as to apply suction to the breast shield.

Abstract: A portable breast pump has a suction unit and a collecting unit which is connected to this suction unit via a flexible suction line. The collecting unit comprises a breast shield, a milk-receiving container and a coupling element which connects the breast shield to the milk-receiving container. The suction unit has a housing with an operating means for operating the pump and a fastening means for fastening the housing on a carrying means, which can be fastened on the mother's body. This breast pump is easy to operate, allows the milk to be expressed even in confined areas with no set-down surfaces and, in addition, does not hinder the mother's mobility.

Abstract: A manual breastpump has a pump mechanism for use in one mode of operation to produce an ejection (letdown) reflex in a nursing mother and in a separate mode of operation for the general expression of breastmilk. The breastpump further provides a pump mechanism having an expansible chamber device carried by the handle, which is operated by moving the handle relative to a handle mount. A double-pivot for the handle yields letdown mode as well as the general pumping mode.

Abstract: A nipple coating member and a milking device for gathering mother's milk effectively. The pad of a milking device comprises a tubular frame having a large diameter side opening for inserting the nipple formed on one end side and a small diameter side opening formed on the other end side, a first flexible portion provided at a part in the circumferential direction between the large diameter side opening and the small diameter side opening of the tubular frame, and a second flexible portion provided at a position opposing the first flexible portion independently thereof. The first flexible portion can be deformed inward of the tubular frame by a pressing force from the outside of the pad, and the second flexible portion can be deformed outward of the tubular frame by a pressing force from the inside of the pad.

Abstract: The invention provides a system and a method of eliciting milk from all mammals that possess teats, including but not limited to dairy animals and humans. A system may be comprised of an elastic system and a vacuum supply. A method may include a milk elicitation system comprised of an elastic system and a vacuum supply. Through the application of vacuum, the elastic system forms, differentiates, seals and adapts to a teat, from the area it ends until up to where the udder ends and it begins, without coming in contact with the teat-end sphincter/lactiferous duct(s). The elastic system interacts proportionately according to the tendencies expressed by teat physiology and dynamics according to the milk pressure change, blood flow, and the effects of applied vacuum, throughout the milk elicitation process, resulting in continuous and complete milk elicitation and supporting the physiological teat return, after the process.

Abstract: A breast pump has at least one collection assembly for engaging at least a portion of a breast surrounding a nipple and a vacuum pump for applying a vacuum to the collection assembly and thereby to at least the nipple of the breast. A controller is operable to cyclically operate the vacuum pump between a maximum vacuum pressure in the range of about 70 mm Hg to about 150 mm Hg and a latching pressure of about 30 mm Hg.

Abstract: Inner and outer shield parts of a breastshield are joined to form an enclosure defining a pressurizable chamber. The inner shield part has at least a portion thereof movable relative to the outer shield part when the chamber is subject to a negative or a positive pressure. A first pressure port is in communication respectively with the chamber for connection with a fluid pressure source of a first pressure. A second pressure port is in communication with the interior for connection with a pressure source of a second pressure. The breastshield is thus capable of being subjected to two different pressures, such as a positive pressure to move (expand) the chamber into the interior, so as to compress or massage the nipple/breast, and a negative pressure in the interior to draw the nipple/breast further therein for the expression of milk. The pressures can be independently controlled, and may furthermore alternate being negative and positive through the same pressure port.