This application claims the right of foreign priority to German Application No. 100 61 953.3-24 filed on Dec. 8, 2000, which is incorporated herein by reference in its entirety.
The invention relates to a coupling device for transferring fluid pressure from a first coupling element to a second coupling element, wherein both coupling elements comprise end faces facing each other which are movable against each other, wherein each of the coupling elements comprises a cavity that runs into an opening at the end face and which can be coupled with the cavity of the other coupling element for transferring fluid pressure, wherein in each of said cavity a piston is guided movably in axial direction, wherein both cavities at the respective side facing the other coupling element comprise a sealing surface which is connected to the opening of the end face and against which the piston is sealable by a counter surface, wherein each of the pistons is biased into the direction of the respective other piston by a biasing means toward a sealing position within which each respective piston rests by its sealing surface against the counter surface, and wherein means is provided for moving at least one of the pistons against the action of the biasing means into the direction of an opening position within which a fluid communication is enabled for transferring fluid pressure via the cavity and the opening of the end face from one coupling element into the opening of the other coupling element.
Such a coupling device is known from DE 32 28 140 A1.
In the known coupling device, each of both pistons protrudes in the sealing position outwardly beyond the sealing surface, thereby sealing with its cone surface against a mated inner cone surface of the cavity of the coupling device.
The opening of the valves formed in this way is effected when both coupling elements are moved with their sealing surface against each other, whereby both pistons come to rest against each other with their end faces and thus are axially moved with respect to the sealing position, thereby releasing a fluid communication between the outer surfaces of the pistons and the inner surfaces of the respective cavities of the coupling elements.
The known coupling device serves to connect hose or tube lines for the pressure medium supply of machines and machine parts, in particular in mining excavation facilities.
A drawback of the known device rests in the fact that the coupling is immediately opened by axial movement of the pistons, in particular before a sealed connection between both coupling elements is reached. This leads to the consequence that, before a closed connection between both coupling elements is effected, fluid, for instance oil, may leak from the coupling place, this having disadvantages.
Such coupling devices are needed for numerous applications to transfer a fluid pressure from one coupling element to another coupling element. For instance, in hydraulic clamping, it is common to separate hydraulic clamping units from the oil supply. This is done, for instance in hydraulic exchanger units, such as in clamping adapters or clamping chucks in various working machines. To this end, self-sealing coupling elements are necessary for transferring the hydraulic pressure. Herein, the coupling device shall be as tolerant as possible with respect to radial positioning errors of both coupling elements with respect to each other.
It is a first object of the invention to provide an improved coupling device for transferring fluid pressure from a first coupling element to a second coupling element.
It is a second object of the invention to provide an improved coupling device which is self-sealing when separating both coupling elements from each other.
It is another object of the invention to provide an improved coupling device which does not require exact radial positioning of the coupling elements.
It is still another object of the invention to provide an improved coupling device which is suitable to retain a high fluid pressure in a receiving coupling element when the coupling element supplying the fluid pressure is removed.
These and other objects of the invention are achieved in a coupling device of the afore-mentioned kind in that the means for moving at least one piston comprises a retaining room that acts to move the piston against the action of the biasing means into the opening position, when subjected to fluid pressure.
According to the invention, the fluid pressure itself is utilized to effect an axial piston displacement into the opening position, when both coupling elements rest against each other, thereby releasing a fluid channel between both coupling elements.
In addition, it is made possible that both pistons move into their sealing positions under the action of the biasing means, if both coupling elements are separated from each other, thereby sealing each of the coupling elements. Also a flush or recessed arrangement of the pistons, respectively, can be obtained so that no parts protrude beyond the end surface. Thereby, the danger of damage and of contamination to each coupling element is reduced considerably. At the same time, it is avoided that fluid may leak from input or output pipes already under pressure during effecting the coupling connection
According to a further development of the invention, the piston of at least one of the coupling elements is terminated at its end facing the other coupling element by a head section which comprises the counter surface coacting with the sealing surface and which is terminated at its end face by a head surface that faces the other coupling element.
Thereby, a fluid pressure which can be transferred in the opening position via a gap between the counter surface and the sealing surface can act beyond the opening of one coupling element onto the end face of the other coupling element, to thereby displace the latter against the action of its biasing device into the opening position. Thus, by the fluid pressure of one coupling element supplying the fluid pressure, the piston of the other coupling element can be moved into the opening position. Thereby, the coupling element receiving the fluid pressure closes by its own under action of its biasing device, if the coupling element supplying the fluid pressure is closed or removed from the other coupling element, respectively.
In an advantageous improvement of this design, the head face is made substantially flush or recessed with respect to the end face of the coupling element when being in the sealing position.
This allows to make the surfaces of the coupling elements completely flat, thus substantially reducing the danger of contamination.
According to an improvement of the invention, at least one piston of the coupling elements comprises a central fluid channel which communicates via a connecting channel with the retaining room, the central fluid channel being provided between the wall of the cavity and the piston to effect a movement of the piston against the action of the biasing means into the opening position, if subjected to fluid pressure, within the opening position a fluid communication from the central fluid channel to the opening of the end face of the other coupling element being provided via the connecting channel, the retaining room and a gap between the sealing surface and the counter surface toward the opening of the end face of the other coupling element.
Thereby, a particularly simple and reliable construction is achieved.
According to a further development of the invention, the biasing device of at least one of the coupling elements is configured as a spring means which is being fixed between the piston and a terminating element that is mounted at the side of the wall of the cavity opposite the other coupling element.
By this measure, a strike limitation for the piston can be effected in a particularly simple way.
According to a further development of the invention, the piston of at least one coupling element comprises a hollow cylindrical extension arranged at the end opposite the other coupling element, the outer surface of which is guided displaceably in a bore of the terminating element and is configured sealed thereto.
With these features the fluid transfer through the central fluid channel within the hollow cylindrical extension into the retaining room can be effected in a simple way.
According to a further development of the invention, the sealing surface at the end of the cavity of at least one of the coupling elements is configured as an inner cone surface following to the retaining room and running into the opening at the end face of the coupling element, wherein the counter surface of the piston is configured as an outer cone surface mated thereto.
Thereby, the communication between the retaining room and the sealing surface and the counter surface can be effected in a particularly simple way.
According to an additional development of the invention, the cavity of at least one of the coupling elements is arranged in a coupling insert that is received in a recess of a base body.
Thereby, the assembly of the respective parts to the coupling element is substantially simplified.
According to a further embodiment of the invention, a sealing element, preferably an annular sealing, is provided at the end face of at least one of the coupling elements, for sealing the region about both openings in the sealing position.
If both end faces of the coupling elements rest against each other, thereby a sealing of the region surrounding the opening of the coupling elements to the outside can be effected so that fluid pressure from one coupling element can be transferred to the other coupling element without leakage.
In a preferred improvement of the invention, both coupling elements are configured substantially identical and arranged symmetrical to each other, apart from the sealing element at the end face of one coupling element.
Thereby, the design of the coupling device is substantially simplified, since rather identical parts can be utilized for both coupling elements.
According to a further embodiment of the invention, the biasing device of the coupling element supplying the fluid pressure has a lower retention force than has the biasing device of the other coupling element.
In case the fluid supply is interrupted, thereby it can be guaranteed that first the piston of the other coupling is moved back into the sealing position before also the piston of the coupling element supplying the fluid pressure is closed. Thereby, it is ensured that any leakages after separation of both coupling elements can be avoided substantially.
It should be understood that the afore-mentioned features and the features to be subsequently explained cannot only be used in the given combination, but also in other combinations, or by its own, without leaving the scope of the invention.