One pipe flange is provided with a sealing element and a vertical, external coupling wedge, while the other pipe flange has a sealing face and a connecting claw fitting to the external coupling wedge.

Heretofore sewage collecting tanks have been components made of concrete or prefabricated concrete elements, and their assembly on location has been labor-intensive, time-consuming and involved substantial expense.

Consequently, such sewage collecting tanks or transfer tanks have been in most cases prefabricated plate structures which merely needed to be positioned in previously excavated pits.

It has been a further simplification that the pre-assembled pump unit could be positioned in many transfer tanks by using a rapid coupling. This has simplified not only the establishment of the transfer system, but its maintenance as well, since any reparation of the pump unit could be performed after its removal from the tank, rather than working on the pump unit within the tank under significantly uncomfortable and polluted conditions. The known rapid couplings are generally formed of a fixed pipe flange secured to an end of the pressure conduit and a coupling pipe flange secured to the pressure pipe of the pump. On the upper part of the fixed pipe flange a vertical, wedge-shaped guide element is provided, to which fits a claw mounted on the coupling pipe flange.

The fixed pipe flange and the coupling pipe flange are clamped together by the weight of the pump unit, thus ensuring a seal. Such solutions are described, for

example, in Hungarian Utility Model No. 1984 or Published PCT Application No.

WO 84/02512.

Since the conduits of the pressurized sewage collecting systems have a relatively small diameter, care has to be taken in a simple manner to avoid possible clogging. For this purpose the pump units often include"back-wash" pipes which are conduits joining the pressure pipes and which may be coupled to a source of compressed air or high-pressure water externally of the tank for cleaning the clogged connecting conduits. The pressure conduit of the pumps generally contains a check valve to ensure that in the course of such back- washing operation the high-pressure medium is admitted only into the pressure conduit and to further ensure that after removal of the pump no sewage can flow back from the pipe network into the tank.

Numerous elements, including T-joints, are conventionally required for the installation of the rapid coupling, the check valve and the back-wash conduit. All these contribute to an increase of manufacturing expenses as well as to the possibilities of malfunctions and furthermore increase the spatial requirement of the pump unit.

The conventional rapid coupling also involves the problem that the pressure conduits in the network are cleaned-particularly in case of clogging- with water under high pressure. In systems of low pressure, however, the operational load is generally 2.5 bar at the most. Consequently, during cleaning with high-pressure water, the rapid coupling elements which are suspended above the pipe flanges and which are maintained in a closed state solely by the weight of the pump unit, tilt off the sealing surface and blow which means that impermissible sewage backflow definitely occurs.

Accordingly, the present invention has for its object a solution which prevents the rapid coupling elements from separating from one another and which makes possible a maximum reduction of the number of the necessary elements of the pump unit.

The above object is solved according to the invention by means of a rapid coupling which comprises a fixed pipe flange secured to an end of the pressure conduit and a coupling pipe flange secured to pressure pipe joining the pump. One of the pipe flanges is provided with a sealing element and a vertical, external coupling wedge, whereas the other of the pipe flanges has a sealing face and a connecting claw which fits to the external coupling wedge.

The fixed pipe flange has, at both ends of its horizontal diameter, a respective external coupling wedge, whose wedge faces are oriented in a direction pointing away from the coupling pipe flange. Further, adjacent such wedge faces additional, vertically directed, lateral guide faces are provided which are oriented radially outward. The coupling pipe flange includes bilaterally arranged connecting claws which are provided with faces that fit to the wedge faces of the coupling wedges and with guide faces that fit to the vertical, lateral guide faces of the coupling wedges.

The guide faces of the connecting claws fitting to the coupling wedges are vertical and in given circumstances may be provided at the bottom with a chamfer extending obliquely outward from sealing face. The lateral guide faces of the fixed pipe flange may be wedge-shaped surfaces or may be the outer superficies of the pipe flange. The wedges provided on the rapid coupling have a wedge angle which is expediently lager than that needed for self-locking.

In an expedient embodiment of the rapid coupling according to the invention, the coupling pipe flange is integral with a coupling housing which is a T-joint accommodating a check valve, expediently a ball-type check valve.

According to the invention, the spatial requirement of the pump unit may be reduced, its manufacture and operation is less expensive and simpler, the number of possibilities of malfunctions is decreased, and maintenance work on practically all elements belonging to the tank may be performed externally thereof after removal of the pump unit.

Further details of the invention will be discussed by means of exemplary embodiments in conjunction with the drawing, where Figure 1 is an illustration of a transfer tank provided with a pump unit having a conventional rapid coupling, Figure 2 is an illustration of a transfer tank provided with a pump unit having a rapid coupling according to the invention, Figure 3 is a perspective view of a rapid coupling according to the invention, Figure 4 is a top plan view of one part of the rapid coupling shown in Figure 3, Figure 5 is a sectional view taken along line A-A of Figure 4 and Figure 6 is a sectional view of a rapid coupling structured as a check valve.

In a conventional transfer tank 1 illustrated in Figure 1, a fixed part 2a of a rapid coupling 2 is supported by a bracket 3 secured to the wall of the transfer tank 1. The pressure pipe 4 of a pump unit contains three separate components: a coupling part 2b of the rapid coupling 2, a check valve 5 and a T-joint 6 for providing a connection with a back-wash pipe 7.

As seen in Figure 2, in the pump unit according to the invention all the coupling and shut-off functions are present in a sole combined coupling element. As a result, the pump unit is significantly simpler, smaller and less expensive than the solution shown in Figure 1.

Furthermore, it is expedient to structure the pump unit such that at the end of the back-wash pipe 7 a handle 9 is provided for a simple removal and lowering of the pump unit. In the illustrated embodiment the handle 9 is a part of the back-wash pipe 7 and may be an elbow fitting which may be easily grasped.

Figure 3 illustrates an expedient embodiment of the rapid coupling according to the invention. The rapid coupling 2 comprises a fixed pipe flange 10 and a coupling pipe flange 11. The fixed pipe flange 10 may be attached by

means of a threaded connection to an end of the pressure conduit of the transfer tank, while the coupling pipe flange 11 is integral with a coupling housing 12. Connecting claws 13 extend bilaterally from the coupling pipe flange 11. In the operational state the coupling housing 12 has a vertical orientation, and the connecting claws 13 extend horizontally from the mid portion of the coupling housing 12. The connecting claws 13 fit to coupling wedges 14 formed on the fixed pipe flange 10. A lateral guidance of the connecting claws 13 is ensured by lateral guide faces provided on the fixed pipe flange 10. The coupling wedges 14 are formed at opposite ends of the horizontal diameter of the fixed pipe flange 10, and their wedge faces are oriented in a direction pointing away from coupling pipe flange 11. In the illustrated example the lateral guide faces are wedge faces 15 projecting from the superficies of the fixed pipe flange 10. Further, guide faces 16 are formed on the bent-back branches of the connecting claws 13.

Figure 4 shows a top plan view of one of the connecting claws 13 of the rapid coupling 2 illustrated in Figure 3, while Figure 5 is a sectional view of Figure 4, taken along line A-A. It is seen that the guide face 16 of the connecting claw 13 has a vertical part 17 at the top and a chamfer 18 at the bottom. This arrangement ensures an essentially line-contact between the coupling wedge 14 and the guide face 16 in the vicinity of the center line of the coupling wedge 14 and the connecting claw 13. This arrangement increases the reliability of the connecting process and the immobilization of the rapid coupling.

It is, however, feasible to provide a vertical or arcuate guide face 16.

The centering of the coupling pipe flange 11 of the rapid coupling 2 is ensured during the coupling motion by the cooperation between the wedge faces 15 provided laterally on the fixed pipe flange 10 and the inner faces 19 of the connecting claws 13. Thus, during establishment of the coupling from above, the mutually engaging faces of the fixed pipe flange 10 and those of the coupling pipe flange 11 are gradually clamped to one another by the coupling wedges 14 and the guide faces 16, while at the same time the wedge faces 15

of the fixed pipe flange 10 and the faces 19 of the connecting claws 13 ensure a central positioning in a horizontal direction.

Figure 6 illustrates a sectional view of an embodiment of the rapid coupling 2 according to the invention, where the fixed pipe flange 10 and the coupling pipe flange 11 join one another along their end faces 20 in the operating state. A sealing ring 21 is inserted in the end face 20 of one of the pipe flanges, while the end face 20 of the other pipe flange is formed as a sealing face. In the shown embodiment the sealing ring 21 is provided in the coupling pipe flange 11, while the sealing face is formed on the fixed pipe flange 10.

In the illustrated embodiment the coupling housing 12 is structured as a check valve ; that is, the rapid coupling 2 constitutes a combined unit which ensures a coupling, on the one hand, and a shutoff in the proper direction of the pressure conduit, on the other hand. The check valve proper is formed by a valve ball 22 positioned in the coupling housing 12. In its lower position the valve ball 22 is seated on a valve seat 24 provided in a threaded cap nut 23 closing the coupling housing 12. In its upper position the valve ball 22 is urged by pressure against the valve seat 25 formed on the inner surface of the coupling housing 12. As a result of this arrangement, during operation of the pump, the liquid pressure presses the valve ball 22 against the upper valve seat 25, allowing liquid to flow into the pressure conduit of the network. If, in case clogging occurs, liquid or air flows through the back-wash pipe 7, the valve ball 22 assumes its position on the valve seat 24 and thus shuts off the flow path toward the pump.

As further seen in Figure 6, the establishment of a smooth fitting contact between the fixed pipe flange 10 and the coupling pipe flange 11 is assisted by a chamfer 26 which is provided on an upper part of the fixed pipe flange 10 and which facilitates the guidance of the coupling pipe flange 11 into contact with the fixed pipe flange 10. It is to be understood that such a chamfer may also be formed on a lower portion of the coupling pipe flange 11.

The described and illustrated exemplary embodiments well demonstrate that the pump unit according to the invention renders the making and operation of transfer tanks safer and more economical and reduces the number of likely malfunctions.

It is to be understood that the discussed embodiments merely represent exemplary solutions according to the invention, and that numerous other solutions may be feasible within the scope of the attached claims.