QUICK COUPLER FOR A BIDIRECTIONAL CHECK VALVE AND A FLUID COUPLING COMPRISING TWO SUCH QUICK COUPLERS

TECHNICAL FIELD

The present invention relates to a quick coupler for a bidirectional check valve and a fluid coupling comprising two such quick couplers.

PRIOR ART

WO 03/087638 A1 discloses a bi-directional check valve controlling the movement of a fluid. A valve body has an opening at one side, a further opening at the opposite side of the valve and a passage connecting the opening and the further opening. A movable poppet defines a cavity and is disposed within the passage of the valve body. A spring is coupled to the movable poppet. A further poppet is disposed within the cavity, and a further spring is coupled to the movable poppet and to the further poppet, which further spring is opposite to the spring. When fluid passes through the opening in the valve body and exerts a force on the movable poppet that is greater than the spring force, the further portion of the outer surface of the movable poppet is directed away from the further portion of the wall of the passage and permits the fluid to flow from the opening in the valve body through a channel and to the further opening in the valve body. When fluid passes through the further opening in the valve body and exerts a force on the further poppet that is greater than the further spring force, the further portion of the outer surface of the further poppet is directed away from the further opening in the valve body to open a further channel in the movable poppet and permit the fluid to flow from the further opening in the valve body through the further channel and a plurality of flutes or recesses in an outer surface of the further poppet to the opening of the valve body.

US 2017/191 595 A1 discloses a coupling including a coupler and nipple. The nipple has a valve in a normally-closed position and an outer peripheral surface with a plurality of spaced-apart, close-ended cam paths. The coupler has a valve in a normally-closed position and includes a set of latching balls for engagement with the cam paths to secure the coupler to the nipple. The coupler further includes a sleeve mounted thereon and movable between forward and retracted positions. In the forward position, the latching balls are forced into an inward position that prevents release of the latching balls from the cam paths, and in the retracted position, the latching balls are permitted to extend to an outward position enabling initial engagement with or disengagement from the cam paths. The coupler also includes a set of locking balls that prevents movement of the sleeve to the retracted position.

Furthermore, US 6,354,564 B1 discloses a ball detent fluid coupling for liquid and gas applications with a ball-retaining sleeve on the socket that is retractable by hand for joining and for separating the socket and plug and comprises a pressure-actuated check valve mounted on a valve guide within the flow path to preclude backflow into the supply side of the coupling. The valve also operates to shut off the flow when the mating parts of the coupling are disconnected or when flow through the coupling is shut off. A conventional valve can be mounted in the fluid flow passageway opposite the pressure-actuated check valve to urge the mating plug and socket to decouple when the sleeve releases the ball detents from engagement with the plug and to stop flow in the discharge line.

US 5,540,250 A discloses a further ball detent fluid coupling for gas fuel for appliances and the like equipment with push-to-connect and pull-to-disconnect features as well as a heat responsive breakaway feature,

EP 1 148 285 A2 A quick-action fluid coupling for connecting two fluid-conducting lines includes a plug for attachment to one of the lines and a socket for attachment to the other. The socket has a tubular body and includes a valve having a valve sleeve and a fixed valve stem coaxially disposed within the tubular body. The valve sleeve is moved axially upon connection of the plug and socket so as to open a fluid flow passage between the valve sleeve and the valve stem. The outer surface of the valve stem defines a plurality of circumferentially spaced depressions therein. A circumferential groove is defined in an inner surface of the tubular body and is spaced radially outward of and in axial alignment with the depressions in the valve stem. A plurality of separately formed, discrete retaining elements are respectively engaged partly in the depressions in the valve stem and partly in the groove in the tubular body. Each retaining element is captively retained between forwardly and rearwardly inclined surfaces of the corresponding depression and between forwardly and rearwardly inclined surfaces of the groove. Thus, the retaining elements cooperate with the surfaces of the groove and of the depressions to prevent axial movement of the valve stem. The plug includes a valve member that is slid to an open position by engagement with the valve stem of the socket when the plug is inserted into the socket.

Further documents relating to this technical field are EP 2 376 741 B1 , US 1 ,331 ,720 A and GB 2,571 ,933.

SUMMARY OF THE INVENTION

Based on this prior art it is an object of the invention to provide a quick coupler for fluidconducting lines which can be easily used in fluid couplers.

Such a quick coupler comprises a tubular body having an external sleeve surface, an internal reception cavity, an axial fluid flow passage therethrough and a valve seat , an expansion body having an axial fluid flow passage therethrough and an external sleeve surface, and a valve comprising a valve ball, a stem and a compression spring. The external sleeve surface of the expansion body is oversized in view of the internal reception cavity of the tubular body for creating an outwards directed force on the external sleeve surface of the tubular body when introduced into the tubular body. The valve ball is positioned between the spring and the stem, wherein the spring is positioned to pretension the valve ball against the valve seat and closing the axial fluid flow passage through the quick coupler for any pressure on the valve ball from the direction of the stem lower than a predetermined threshold, wherein the stem is extending beyond the front surface of the tubular body when the valve ball is in contact with the valve seat and wherein the axial fluid flow passage through the quick coupler is open when the stem is pushed in the direction of the valve ball hat the front surface of the stem is flush with the front surface of the tubular body, wherein the spring and the valve ball are at least partially positioned in a cylindrical housing which is attached to the tubular body.

The stem can have a flange having a greater diameter than the guiding bore of the expansion body.

The housing can have a side opening near its attachment portion to the tubular body allowing a fluid ball passing the valve ball to leave the housing. The housing can have a first inner diameter near the attachment portion to the tubular body adapted to accommodate and guide the valve ball and a second inner diameter on the side opposite to the attachment portion to the tubular body adapted to accommodate and guide the spring.

Then, the housing can have an open bottom surface and/or side openings along its portion with the second diameter.

Furthermore, the first diameter can then be larger than the second diameter and a tapering section is provided between the two portions of different diameter.

The axial fluid flow passage inside the expansion body can comprise at least one, preferably a number of axial through holes in the expansion body in a radial distance from the longitudinal axis of the expansion body.

A fluid coupling for fluid-conducting lines comprises a first and a second quick coupler according to the invention and a male and a female hydraulic connector. The male hydraulic connector has an axial fluid flow passage therethrough, a reception cavity with the diameter of the tubular body of the first quick coupler and having a rear end for connection with a first fluid-conducting line and an opposite forward end and comprising a coupling end. The female hydraulic connector has an axial fluid flow passage therethrough including a reception cavity with the diameter of the tubular body of the first second quick coupler and having a rear end for connection with a second fluid-conducting line and an opposite forward end as well as a reception cavity for the coupling end of the male hydraulic connector. The first and second quick coupler are positioned in the male and female hydraulic connectors with the front surface not extending beyond the front surface or beyond the inner wall surface of the reception cavity of the male and female hydraulic connector, respectively, when the expansion bodies of the quick couplers are fully positioned in the respective quick couplers. The male and female hydraulic connectors are configured such that the forward end of the male hydraulic connector can be axially inserted into the forward end of the female hydraulic connector for establishing a continuous fluid flow path between the hydraulic connectors.

Such a fluid coupling can have the male hydraulic connector as well as the female hydraulic connector comprising a connection device, especially a screw. In one coupling system, the fixing of the male connector to the female connector is achieved by means of a tightening screw placed on one side of the connector. This can introduce a tilt angle in the opening force applied to the check valves, making it not perfectly aligned along the longitudinal axis of symmetry. In a different solution, a the straight, axysym metrical geometry of the connectors is chosen, wherein the engagement of the cylindrical surfaces of the male and female connectors, together with the axysymmetrical engagement of the thread on a nut - as a part of the connection device - with a complementary thread on the female connector, ensures a perfect in-line application of the opening force along the longitudinal axis of symmetry.

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows a schematic cross-section view of a fluid control element according to an embodiment of the invention in the closed position of the valve when not coupled;

Fig. 2 shows the schematic cross-section view of the fluid control element of Fig. 1 , when the valve is in the open position, i.e. when the fluid control element is coupled;

Fig. 3 shows a schematic cross-section view of two fluid control elements according to Fig. 1 positioned in the male and female hydraulic connectors of a bidirectional check valve one in face of the other;

Fig. 4 shows the schematic cross-section view of Fig. 3, when the bidirectional check valve is closed;

Fig. 5 shows a view on the front surface of the fluid control element;

Fig. 6 shows a perspective view of the fluid control element of Fig. 1 ;

Fig. 7 shows a schematic cross-section view of two fluid control elements according to Fig. 1 positioned in the male and female hydraulic connectors of a further bidirectional check valve one in face of the other; and

Fig. 8 shows the schematic cross-section view of Fig. 7, when the further bidirectional check valve is closed.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a schematic cross-section view of a fluid control element 100 according to an embodiment of the invention in the closed position of the valve when not coupled. Fig. 2 shows a schematic cross-section view of the fluid control element 100 of Fig. 1 when the valve is in the open position, i.e. when the fluid control element 100 is coupled. It is noted that Fig. 1 and Fig. 2 show the fluid control element 100 with a fully inserted expansion pin 2 blocking effectively the blow-out of the fluid control element 100 from the respective female 22 or male 23 hydraulic connector in which it is functionally inserted.

The flow control element 100 according to the invention is a quick coupling element that is to be inserted into coupling members, especially an hydraulic connection 200 of a male and a female hydraulic connector 22, 23 between two hoses 25, 25' or at the junctions inside an hydraulic system as will be seen in Fig. 3 and Fig. 4, showing the coupling element 100 in a fully inserted state as explained below.

The quick coupling element 100 comprises a sleeve-shaped or tubular base body 3, an expansion pin 2, a sealing sphere 4, a loading spring 6, a housing 5 for the loading spring 6 and the sealing sphere 4, and an opening piston 1 . All these elements are provided around the longitudinal axis 10 of the quick coupling element 100 which will be at the same time the longitudinal axis 10 of the female 22 and male 23 hydraulic connector. The tubular base body 3 comprises a reduced diameter shoulder 31 within which a reception for the housing 5 is provided as well as a matching curvature seat 18 for the sealing sphere 4. On the outer side of the reception for the housing 5 is provided a circumferential extension 37 or a plurality of longitudinal extensions around the circumference which is/are bent to the center line 10 to fix the position of the housing 5.

The housing 5 is a hollow cylinder with a diameter to accommodate the loading spring 6. It may have an open bottom and/or side openings along the spring 6. The diameter of the housing 5 can have an increase to accommodate a sealing sphere 4 with a greater diameter than the spring 6. Since the sphere 4 is guided for its longitudinal movement against the force of the spring 6 through the push of the opening piston by the housing, there is provided at least one side channel 11 allowing the fluid entering through the coaxial cavity 12 flowing around the sphere 4 and leave the housing 5.

Two identical quick coupling elements 100 can be inserted inside an installation bore 30, 30' of the two hydraulic connectors 23, 22 of an hydraulic connection 200 featuring a diameter restricting shoulder section or step-like section 26, 26’ that allows its installation from the side of the outer face 27, 27' of the hydraulic connectors 23, 22. During installation, when the step-shaped feature or shoulder 31 of the base body 3 gets in touch with the counter step feature or shoulder 26, 26' of the installation bore 30, 30', a pushing force applied on the expansion pin 2 allows to insert this element inside the base body 3, resulting in an outfacing radial force that causes the plastic expansion of the inner walls 20 of the hollow part of the base body 3. This plastic deformation is transmitted to the outer surface 19 of the base body 3 that gets pressed tight against the bore surface 32, 32’ of the respective male 22 and female 23 hydraulic connectors, therefore providing in the fully installed state shown in Fig. 3 and Fig. 4 both the functions of anchoring and sealing between the external surface 19 of the base body 3 and the walls of the bore 32, 32’ of the respective male 22 and female 23 hydraulic connectors. The front surfaces 38 of the base bodies 3 are then flush with the above-mentioned front surfaces of the hydraulic connectors 23, 22, respectively; and therefore the reference numeral 38 and 27 are used for the center near and center distance parts of this front surface.

The closed state of the quick coupling element is shown in Fig. 1 and Fig. 3. In this closed state, the spring 6 pushes the sphere 4 against the base body 3 and a thin spherical section of the sphere 4 gets in contact with a correspondingly thin spherical section 18 on the base body 3 with a matching curvature radius. In the configuration shown in Fig. 3, a fluid especially a liquid at a defined pressure is present in the circuit 25, 25’ and applies a pressure on the back side of the quick coupling element 100, which is called a reverse pressure. This reverse pressure pushes the sphere 4 tight against the base body 3 on the thin spheroid section 18, providing a sealing function and zero leakage of the liquid. In this configuration, the opening piston 1 doesn’t offer any resistance to the movement of the sphere 4 and lies in the rest position shown in Fig. 1. The quick coupling element 100 has reduced dimensions compared to prior art solutions, that make it suitable for high-pressure applications and that the sealing of the liquid is achieved without the use of any plastic O- ring.

The open state of the quick coupling element is shown in Fig. 2 and 4. This situation occurs when a male hydraulic connector 23 with an inserted and expanded quick coupling element 100 is plugged to a female hydraulic connector 22 with another opposite-facing, inserted and expanded quick coupling element 100. In this configuration, the outer surface 34 of the male connector 23, together with the inner surface 33 of the female connector 22, forms a guiding system that forces the alignment of the two counterfacing quick coupling elements 100 along their common main longitudinal axis 10 of symmetry which is, in turn, also coincident with the main longitudinal axis 10 of symmetry of the male 23 and female 22 connector system in their plugged state in Fig. 4.

During the close-to-open transition, when the male connector 23 and female connector 22 get plugged together, which is shown by a transition between Fig. 3 and Fig. 4, the outermost front surfaces 21 of the pistons 1 are the first elements of the quick coupling 100 that get in touch to each other. Further connection of the two plugs 23 and 22 up to the final position where the front face 27 of the male connector 23 gets in contact with the back face 27' of the female connector 22, causes the sphere 4 to be pushed back via the contact surface 16 between the sphere 4 and the piston 1 , causing a compression of the spring 6 in the housing 5 and bringing the two opposing quick coupling elements 23 and 22 in their fully open state as shown in Fig. 4. The expansion pin 2 features a central hole 17 that guides the piston 1 during its forward and backward movements, in such a way that it is always centered to the main longitudinal symmetry axis 10 of the quick coupling element 100. This is achieved due to a tolerance between the diameter of the middle section 8 of the piston 1 and the diameter of the central hole 17 of the expansion pin 2. In Fig. 2 the reference numeral 17 of the central hole seems to indicate towards the cylindrical surface of the opening piston 1 , but there is a sliding tolerance distance between the piston 1 and the expansion pin 2. This guidance ensures the reliability of the functioning of the quick coupling element 100 over several opening-closing circles, by ensuring a reliable contact of the piston back surface 16 to the sphere front surface, symmetrically centered with respect to their common axis of symmetry 10.

The reliability of the quick coupling opening-closing mechanism is also enhanced thanks to the larger diameter and flange 9 of the front section of the piston 1 , which increases the contact surface 21 of the portion of the piston 1 responsible for opening the quick coupling element. The flange 9 can be a disk. When pushed inside the expansion pin 2, the backside of the flange 9 can abut against the inner front surface or front side 15 of the expansion pin 2, influencing on the maximum opening displacement of sphere 4.

Furthermore, the piston 1 is characterized by a sphere adjacent portion 7, whose diameter is slightly larger than the diameter of the middle section 8 of the piston 1 which is guided through the expansion pin 2. Whereas the difference of diameter between the middle section 8 and the flange 9 of the piston 1 is of course directly visible in the drawings, the difference in thickness between the middle section 8 and the sphere adjacent portion 7 is small and not well visible in Fig. 1 and Fig. 2. This difference of diameter forces the piston 1 to move within the allowed boundaries and prevents it from escaping the quick coupling element 100 due to the forces acting on the pin 1 during standard operation. Indeed, the back section 7 of the piston 1 with the contact surface is designed with a finely tuned diameter that prevents it from passing through the central hole 17 of the expanding pin 2. During the opening phase, while the sphere 4 is pushed backwards through actuating flange 9, reference numeral 29 designates a section following the coaxial channel 12 for the flowing of the liquid opens at the position that in the closed state of the quick coupling element 100 corresponded to the sealing point provided by the tight contact as thin spherical section 18 between the sphere 4 and the base body 3. The compression of the loading spring 6 during the opening phase, is guided thanks to the housing element 5, whose geometry features a side channel 11 for the passage of the fluid.

The passage of the fluid through the expansion pin 2 happens through a pattern of circular holes 14 that connect the front side 15 of the quick coupling 100 to the back side of the expansion pin 2. To summarize, in the fully open configuration shown in Fig. 4, the flow channel is provided through the opening sections 15, 14, 13, 12, 29, 11. The same open channels are found on the opposing quick coupling element, just mirrored with respect to the contact plane 35 between the male and female connectors. At the backside of the expansion pin 2 is provided a flow allowing cavity 13 which can be a circumferential cavity around the pin 1 with a diameter allowing for a fluid flow out of the circular holes 14 into this cavity 13.

The channels are then going further through installation bore 30, 30' into hoses 25, 25, respectively., crossing from one quick coupling 100 to the adjacent quick coupling 100 which form together a bidirectional check valve 200 when the outer surface 34 of the male hydraulic connector 23 is inserted into the corresponding cavity 28 of the female hydraulic connector 22 until the coupling of the hydraulic connection 200 takes place, which can be effected by bayonet, cam follower, complimentary threads etc. . It can also comprise an Coring positioned in the recess 24 in the outer surface 34 of the male hydraulic connector and a screw or bolt connection in corresponding openings. Finally, at disconnection as being the transition from Fig. 4 to Fig. 3, the quick couplings 100 gradually close at both sides when the two front surfaces 21 of the pistons 1 of the fluid coupling elements 100 are separating, providing sealing of the liquid with negligible liquid loss during the transient phase in the circuits 25 and 25', respectively, since the thin spherical section 18 with matching curvature radius of the sphere 4 blocks the connection at central channel 29.

Fig. 5 shows a view on the front surface of the fluid control element 100. The opening piston 1 is positioned on the central longitudinal axis 10 with his outermost front surface 21 extending beyond the based body 3 (out of the drawing plan). The front surface 27 of the base body 3 is also flush with the front surface of the expansion pin 2 when fully encased in the base body 3. There are provided six circular holes in the expansion pin. Of course, there might be only one or two but the flow distribution will be less disturbed when the sphere 4 is moving back from the thin spherical section 18.

Fig. 6 shows a perspective view of the fluid control element 100 of Fig. 1. The housing 5 has the side channel 11 opening. The flange 9 is larger than the middle section 8 of the piston 1. The middle section 8 has a slightly larger diameter than the sphere adjacent section 7 to allow the introduction of the piston 1 under pressure but ensures that the piston 1 cannot glide out of the fluid control element 100 when the fluid control element 100 is oriented with its flange 9 downwards.

Fig. 7 shows a schematic cross-section view of two fluid control elements 1 according to Fig. 1 positioned in the male and female hydraulic connectors 123, 122 of a further bidirectional check valve one in face of the other; and Fig. 8 shows the schematic crosssection view of Fig. 7, when the further bidirectional check valve is closed. Features of the embodiment shown in Fig. 7 and Fig. 8 which are identical to features of the embodiment of Fig. 3 and 4 have received the same reference numerals.

Two identical quick coupling elements 100 can be inserted inside an installation bore 30, 30' of the two further hydraulic connectors 123, 122 of an hydraulic connection 210 featuring a diameter restricting shoulder section or step-like section 26, 26’ like in the embodiment of Fig. 3 that allows its installation from the side of the outer face 27, 27' of the hydraulic connectors 123, 122. During installation, when the step-shaped feature or shoulder 31 of the base body 3 gets in touch with the counter step feature or shoulder 26, 26' of the installation bore 30, 30', a pushing force applied on the expansion pin 2 allows to insert this element inside the base body 3, resulting in an outfacing radial force that causes the plastic expansion of the inner walls 20 of the hollow part of the base body 3. This plastic deformation is transmitted to the outer surface 19 of the base body 3 that gets pressed tight against the bore surface 32, 32’ of the respective male 122 and female 123 hydraulic connectors, therefore providing in the fully installed state shown in Fig. 7 and Fig. 8 both the functions of anchoring and sealing between the external surface 19 of the base body 3 and the walls of the bore 32, 32’ of the respective male 122 and female 123 hydraulic connectors.

A male connector 123 and a female connector 122 of cylindrical shape are fixed together by means of a threaded nut 130. The cylindrical nature of the male-female connectors 123, 122 ensures higher control on tighter tolerances than a conical shaped connector. This aspect, when the back and front surfaces 127' and 127 of the male and female connectors get engaged, allows for a symmetric and reproducible opening of the quick coupling system 210.

The nut 130 with a threaded inner surface 131 engages the threaded outer surface 135 of the female connector 122. This engagement mechanism ensures a progressive and smooth opening of the two check valves that form, together, the quick coupling system 210.

An O-ring 150 is provided in a circular groove on the outer surface of the male connector 123, preferably in the front half of this surface. It is used to make a pre-sealing before the coupling system 210 opens. Indeed, the O-ring 150 engages the inner surface 133 of the female connector 122 before the opening of the quick coupling system 210. Further engagement of the nut thread 132 with the thread 135 on the female connector 122 opens the quick coupling system 210; when the outermost front surfaces 21 of the two pistons 1 , preferably of the respective flange 9 of the pistons 1 of the male and female hydraulic connectors 123 and 122 come into contact one with the other and are pushed back into the fluid coupling element 100. This ensures, at any stage during this opening phase, zero leakage of the fluid to the outside, thanks to the sealing provided by the O-ring 150.

The presence of a step-like feature 140 on the male connector 123 ensures controlled and optimal opening of the quick coupling system 210 at full closure, when the front surface 127 of the female connector 122 gets blocked against the front surface 127' of the step 140.

The closed state of the quick coupling element is shown in Fig. 1 and Fig. 7. In this closed state, the spring 6 pushes the sphere 4 against the base body 3 and a thin spherical section of the sphere 4 gets in contact with a correspondingly thin spherical section 18 on the base body 3 with a matching curvature radius. In the configuration shown in Fig. 7, a fluid especially a liquid at a defined pressure is present in the installation bores 30, 30' on the axis of symmetry 10 which can be connected to a circuit 25, 25’ (as shown in Fig. 3 which can be described in Fig. 7 through the bores 30 and 30') and applies a pressure on the back side of the quick coupling element 100, which is called a reverse pressure. This reverse pressure pushes the sphere 4 tight against the base body 3 on the thin spheroid section 18, providing a sealing function and zero leakage of the liquid. In this configuration, the opening piston 1 doesn’t offer any resistance to the movement of the sphere 4 and lies in the rest position shown in Fig. 1.

It is noted that the front surface of the nut 130 extends further along the axis 10 than the front surface 21 of the flange 9 of the piston 1 , thus protecting the piston 1 .

The open state of the quick coupling element is shown in Fig. 2 and 8. This situation occurs when a male hydraulic connector 123 with an inserted and expanded quick coupling element 100 is plugged to a female hydraulic connector 122 with another opposite-facing, inserted and expanded quick coupling element 100. In this configuration, the outer surface 132 of the male connector 123, together with the inner surface 133 of the female connector 122, forms a guiding system that forces the alignment of the two counterfacing quick coupling elements 100 along their common main longitudinal axis 10 of symmetry which is, in turn, also coincident with the main longitudinal axis 10 of symmetry of the male 123 and female 122 connector system in their plugged state in Fig. 8.

A groove in the outer surface 132 of the male connector 123 comprises the O-ring 150 which is engaged by the inner surface 133 of the female connector 122, avoiding any leaks when and before the final configuration of Fig. 8 is reached. The nut 130 is turned around its symmetry axis 10 and moves the male connector 123 and the female connector 122 together until the front surface 127 of the female connector 122 is in contact with the front shoulder of the step 140.

During the close-to-open transition, when the male connector 123 and female connector 222 get plugged together, which is shown by a transition between Fig. 7 and Fig. 8, the hollow sleeves of the quick couplings 100 are the first elements of the quick coupling 100 that get in touch to each other and the O-ring 150 of the male connector 123 is engaged by the female connector 122 before the outermost front surfaces 21 of the pistons 1 are touching each other. Further connection of the two plugs 123 and 122 up to the final position causes the sphere 4 to be pushed back via the contact surface 16 between the sphere 4 and the piston 1 , causing a compression of the spring 6 in the housing 5 and bringing the two opposing quick coupling elements 123 and 122 in their fully open state as shown in Fig. 8. The expansion pin 2 features a central hole 17 that guides the piston 1 during its forward and backward movements, in such a way that it is always centered to the main longitudinal symmetry axis 10 of the quick coupling element 100. This is achieved due to a tolerance between the diameter of the middle section 8 of the piston 1 and the diameter of the central hole 17 of the expansion pin 2.

The reliability of the quick coupling opening-closing mechanism is also enhanced thanks to the larger diameter and flange 9 of the front section of the piston 1 , which increases the contact surface 21 of the portion of the piston 1 responsible for opening the quick coupling element. The flange 9 can be a disk. When pushed inside the expansion pin 2, the backside of the flange 9 can abut against the inner front surface or front side 15 of the expansion pin 2, influencing on the maximum opening displacement of sphere 4.

The passage of the fluid through the expansion pin 2 happens through a pattern of circular holes 14 that connect the front side 15 of the quick coupling 100 to the back side of the expansion pin 2. To summarize, in the fully open configuration shown in Fig. 8, the flow channel is provided through the opening sections 15, 14, 13, 12, 29, 11 as referenced in Fig. 1 and 2. The same open channels are found on the opposing quick coupling element, just mirrored with respect to the contact plane between the male and female connectors 123 and 122. At the backside of the expansion pin 2 is provided a flow allowing cavity 13 which can be a circumferential cavity around the pin 1 with a diameter allowing for a fluid flow out of the circular holes 14 into this cavity 13.

LIST OF REFERENCE SIGNS opening piston 28 cavity expansion pin 29 central channel sleeve-shaped base body 30, 30' installation bore sphere 31 shoulder housing 32, 32' bore surface loading spring 33 inner surface sphere adjacent portion 34 outer surface middle section 35 contact plane flange of piston 36 locking openings axis of symmetry 37 extension side channel 38 front surface coaxial cavity 100 fluid coupling element back side 122 female hydraulic connector circular holes 123 male hydraulic connector127 front side front surface of female contact surface connector central hole 127' front surface of male thin spherical section with connector matching curvature radius 130 threaded nut outer surface 131 inner threaded surface inner wall 132 nut thread outermost front surface 133 inner surface female hydraulic connector 134 outer surface male hydraulic connector 135 outer threaded surface recess for O-ring 140 step with front shoulder, 25' circuit I hose 150 O-ring , 26' shoulder section 200 hydraulic connection front face 210 hydraulic connection ' back face