CA1318904C

CA1318904C - Plugable safety coupling, in particular for pressure air lines

Info

Publication number: CA1318904C
Application number: CA000590064A
Authority: CA
Inventors: Albrecht Wuthrich
Original assignee: Individual
Current assignee: HANS OETIKER AG MASCHINENE- und APPARATEFRABRIK
Priority date: 1988-02-03
Filing date: 1989-02-03
Publication date: 1993-06-08
Anticipated expiration: 2010-06-08
Also published as: EP0327494A1; ES2048861T3; KR970009020B1; WO1989007222A1; CH675619A5; KR900700816A; UA13304A; DE58906605D1; AU2929289A; EP0353272A1; JPH02503109A; ATE99786T1; SU1808065A3; BR8905295A; JP2730598B2; EP0327494B1

Abstract

ABSTRACT OF THE DISCLOSURE

A safety coupling three component parts; a shaped part, a coupling barrel in which the shaped part is rotatably supported, and a plug. The shaped part is a blocking element with a bore that passes diametrically through the cylindrical body. The plug can be inserted through an opening in the housing in a position that varies from the working direction. If the plug is rotated through an angle, the bore moves into a working position and a cylindrical bore in the coupling barrel aligns with the bore in the shaped part. A shoulder area on the plug rests against a stop in the housing and holds the plug in a desired position.

Description

~l31~4 The present invention relates to a plug-type safety coupling for lines used for pressure media, with a coupling barrel which has in its interior a locking element. It is possible to bring this locking element from a locking position into a working position or the reverse by rotating it. Both compressible and non-compressible fl~lid media can be used as the pressure median For the convenience, t:he embodiment in which the pressure medium is air will be considered herein.

Plug-type security couplings are known in numerous variations and are commercially available. Their constructions differ, although most of them have numerous individual components arrange~ axially, one behind the other, with respect to the line that is to be coupl~d, and moveable in this direction.
The operation of such plug-type couplings includes two elements that are functionally coupled:
1. the securing or blocking or unblocking of the plug in the coupling barrel, and 2. the opening or closing a valve that acts in an axial direction.

Despite costly solutions involving the most varied and complex components, known plug-type safety couplings still have dangerous aspects and are somewhat less than user-friendly.
In many safety couplings, the plug is only locked in the coupling barrel once the blocking element has already opened either partially or completely. Thus, at such moment, the plug can be forceably ejected from the coupling barrel.

In known safety couplings the operation of the plug-type coupling must be effected against the pressure exerted by the media that is to be conveyed in order to mova the blocking element in an axial direction and thus release or unblock the lines. Pressure lines with a large internal diameter can scarcely be coupled in this way at normal working pressures of 5 to 10 bar. This also applies at the corresponding negative ~k , ,, 131~9~

pressures or vacuums. In these cases, today one words with blocking valves that are arranged on both sides of the coupling and which remain independent of such a coupling, so that the coupling procedure itself is carried out when there is no pressure. In most cases, these blocking valves are automatic valves, mostly one-way valves. However, such valves reduce the ~ree flow of the medium to a considerable extent.
For this reason, it is understandable that the pressure loss produced by such usual safety couplings can restrict the operation of the apparatuses and equipment that are to be operated, which are located at the end of the line.

In many compressed air couplings, a particularly dangerous situation occurs during the uncoupling procedure. In normal couplings, the line is blocked only shortly after the plug has been unlocked. If the line i~ not held with tha plug securely in the handt the plug is forceably ejected from the coupling by the compressed air forces acting on it. But even in those cases in which, during the uncoupling procedure, the blocking element or the valve is closed and the unlocking is effected after this, the pressure of the compressed air that still remains in the uncoupled line cannot drop and the plug is forceably ejected from the coupling barrel.

Various proposals have been made in the past in order to solve these problems. The most elegant of these incorporates a plug-type safety coupling that has, on one side, a plug that incorporates an enclosing, square cross section bead, and, on the other side, a coupling barrel that is built up ~rom a multi-part housing, in the interior o~ which there is a spherical blocking element to accommodate the plug. The blocking element is so arranged as to be rotatable. The spherical blocking element has a continuous bore into which the plug can be inserted. The spherical blocking element can be pivoted into the operating position by a rotating movement o~ the plug that has been inserted. The plug i9 then secured in the housing in this working position by its bead and thus 1 3 ~

is secur~d against accidental withdrawal or against falling out. Rotation in the opposite direction brings the spherical blocking element into a locking position, whereupon the opening of the continuous drilling also passes over a release port, through which any air that is still under pressure and remains in the plug can escape, wherea~ter the plug can be withdrawn from the spherical blocking element when it is in an unpressurized state.

Because of the fact that the blocking element in these couplings is a sphere on a ball, the housing of the coupling barrel must consist of a plurality of parts in order that the spherical blocking element can be sealed therein. In one embodiment~ the housing consists of two halves with appropriately concave inner surfaces, both of these halves being sealed together. This connection of the two halves is accomplished by riveting.

In another embodiment, the housing consists of a shaped part in the interior of which the spherical blocking element is held by parts that are screwed into the shaped part. These parts have at one end a sealing element with a concave outer side which press this against the spherical blocking element.
Because of the use of a sphere or a ball as a blocking element in the ahove couplings, the housing of the coupling barrel must be built from a plurality of parts. It is understandable that, for this reason, fabrication of this coupling involves a great deal of work and is correspondingly costly. On on~
hand, the individual parts are relatively intricate and accordingly ~re costly to produce, and on the other hand, the assembly of the finished coupling involves a great deal of costly assembly labor because of the plurality of parts. In addition, it is difficult from the technical point of view to support a sphere or a ball so as to seal it. These known couplings have a tendency to leak under high pressures~

~ 8~

For khis reason, the present invention provides a plug-type safety coupling that is of a particularly simple design, is simple to produce, and which works under high pressure without leaking.

According to one aspect o~ the present invention ther~ is provided a plug-type safety coupling for pre!ssure lines, comprising: a plug and a coupling barrel having a housing, a blocking element sealably mounted and secured within said housing, said blocking element rotatable between a blocking position in which the plug may be inserted, and a working position into which the blocking element may be swiveled by means of swiveling the inserted plug, said housing comprising a one-piece shaped part that can be screwed on to a pressure line end piec~, and said blocking element having either a cylindrical or a slightly conical shape and having either a straight.line or a curved line passing through it for the insertion of the plug, said blocking element being sealed against the housing by means of a sealing forming at least - one loop, said seal laying within a corresponding groove taken out of the surface of either the blocking element or out of the inner surface of the housing, and said blocking element being secured in said housing with at least one clamping ring.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a horizontal cross section through the housing and the blocking element , ....

~L31~

Figure 2 is a ve.rtical cross section through the housing and the. blocking element when used as a safety coupling with an inserted plug in the blocked position;

Figure 3 is a vertical cross section of the same, but with the blocking element rotated into the working position;

Figure 4 is a preferred one-piece housing in perspeckive view with the associated blocking element in exploded view;

Figure 5 shows the blocking element with a special seal; and Figure 6 shows a safety coupling for use under particularly high pressure in perspective, in an exploded view.

In essence, the plug-type coupling includes a coupling barrel 1 and an associated plug 20. As can be seen from figure 1, - 4a -~3~9~
the coupling barrel 1 has a threaded hole 3 in the housing 2.
The threaded hole 3 accommodates a threaded nipple of the supply line. It continue~ in a paraxial central bore 4 that forms the connec~ion betw2en the threaded hole 3 and a receiver bore 5 that passes through the housing 2 and is perpendicular to the threaded hole 3. With the thread2d hole 3 and the central bore 4 aligned, one can recognize the outlet opening 6 on the opposite side of the coupling barrel 1. The coupling barrel 1 has an essentially square shape and is curved only on an outlet side. There is a shaped part 10 in the receiver bore 5, this being in the shape o~ a cylindrical body and supported so as to be able to rotate. The shaped part 10 fits exactly so as to seal the recei~er bore 5 in the housing 2 of the coupling barrel 1 and serves as a blocking element for compressed air. A diametrical bore 11 passes through this and intersects the axis of rotation A at right angles. The diametrical bore 11 comprises three areas with diameters that increase incrementally. If one views the diametrical bore 11 in the direction D, one sees the first area 12 with the smallest diameter, the width of which corresponds to the diameter of the cylindrical bore 4. The area 12 is followed in the direction D by a lonyer area 13 with a larger diameter. Within this area therP is an annular groove 15 that is used to accommodate a seal, for example, an 0-ring 17. Continuing in the direction D, finally there is an even wider area 14 that is of even greater diameter. The dimensions o~ th~ diameter of the area 13 and 14 are matched to the plug 20 that is described in greater detail below on the basis of f igure 2.

~his comprises a tubular sleeve 21 and, viewed in the direction D, has saw-tooth serrations at its end. These serrations prevent the compressed air hose (not shown herein), which is pushed onto this and additionally secured by means of a clamp, from being ~orced o~f. ~he sle2ve 21 of the plug 20 has a shoulder section 22 which, when coupled, is accommodated ~3~ 8~0~
completely by the housing 2 or by the blocking element 10.

When coupled, the shaped blocking element 10, which forms the blocking element, blocks the passage for the medium. The shaped blocking element 10 i5 then in such a rotated position that the continuous diametrical bore 11 deviates from the direction D. The angle between these two directions amounts preferably to somewhat less than 90. In this position, the diametrical bore 11 does not communicate with the cylindrical bor~ 4 in the housing 2, so that the shaped part 10 seals off the cylindrical bore ~. In the blocking position that is shown in figure 2 the wider section 14 of the diametrical bore 11 is exactly aligned with an opening 16 in the housing 2 of the coupling barrel 1. The diameter of the opening 16 is exactly equal to the diameter of that area 14 and is slightly greater than the outside diameter of the shoulder section 22 of the plug 20. Thus, when not under pressure, the plug 20 can be inserted through this opening 16 at most until the plug 20 stops on the shoulder between the area 12 with the smallest diameter and the area 13 with the median diameter of the diametrical bore 11. If the sleeve 21 is relatively short from its shoulder section 22 up to its input side end~ then the shoulder section 22 will ~irst come to r~st on the shoulder at the transition area between the mean 13 and the maximum diameter area 14 of the diametrical bore ~1. This is usually the case. The end piece 23 of the sleeve 21 is sealed relative to the blocking element 10 by at least one annular seal 17. Within the area 14 of the diametrical bore 11 there is a compression spring 24 that lies against the shoulder saction 22 on the plug 20 and forces the plug ~0 outwards.

The opening 16 forms one end of an elongated slot 18 that extends in the direction of rotation of the plug 20 along the periphery of the housing 2 so that the plug 20 can be rotated until the diametrical bore 11 is exactly aligned with the cylindrical bore 4 in the housing 2. The width of the ~3:1g9~
elongated slot 18 is less than the diameter of the shoulder portion 22 on the sleeve 21. The lower end of the elongated slot 18 forms the outlet opening 6. Thus, this design permits a completely pressure-ree coupling of the plug 20 into the coupling barrel 1. As soon as the plug 20 has been introduced completely into the coupling barrel 1, the plug 20 can be rotat~d in t~e direction of rotation S. Even with the slightest deviation of the plug 20 from thle insertion position, the shoulder of the shoulder section 22 lies against the inner side of the housing 2 alongside 1the elongated slot 18 and prevents any unintentional release of the plug 20. It is never necessary to overcome the pressure o~ the compressed medium or air when the plug 20 is rotated into the direction D.

It can be seen from figure 3 that, when in the unlocked state, the pressure medium can flow through the whole coupling in a straight line without any obstruction, for the threaded bore 3, the cylindrical bore 4, the diametrical bore 11 and the sleeve 21 of the plug 20 are precisely aligned with each other. In the transition area between the cylindrical bore 4 and the shaped part 10 there is a seal 19.

In order that the plug 20 does not rotate unintentionally from the working position, there is a recess 30 in the receiver bore 5 for the rotatable shaped part 10, and the plug 20 entars into detent in this with its shoulder section 22 when in the working position. The pressure of the compressed air that acts on the face of the plug sleeve is sufficient to force the plug 20 into the recess 30 and thus secure the plug 20. The spring 24 provides additional ~orces for such arrangement. Only in the event o~ a major drop in pressure in the feed line, for example because of a leak, is the plug 20 secured in the desired position by means of the spring 24 alone.

1318~

In order to release the coupling, the plug 20 is rotated from the working position shown in figure 3 into the blocked position as shown in figure 2. ~he plug 20 is first moved against the pressure and the force o~ the spring 24 opposite the direction D. This means that it is released and can be rotated together with the blocking element 10. This closes the cylindrical bore 4 in the manner o~ a cap. When this is done, it must be remembered that there is still pressure in the plug 20 and in the line that is to be uncoupled. This pressure would still be ~ufficient to effect the forceable ejection of the plug 20 from the coupling :barrel 1 as soon as it is in alignment with the opening 16. HDwever, this is prevented by at least one pressure release port 31, four being shown in the drawing, which passes through the housing 2 and open out into the receiving bore 5.

The pressure release ports 31 are so arranged that during the rotational movement of the shaped part 10 they communicate with the diametrical bore 11 in at least one intermediate position. It takes a specific, even though short time, for the pressure to drop. In order to ensure this time during the uncoupling pro~ess, there is in the receiving bore 5 a second recess 32 that is not quire as deep as the recess 30. The plug 20 snaps into this second recess 32 when rotated into this intermediate position/ in which the diametrical bore 11 communicates with the pressure release ports 31. Only when the pressure has dropped can the plug 20 be moved out of this detent and into the final position and thus be withdrawn from the coupling barrel 1 without risk. It is, of course, understood that the shaped par-t 10 has to be secured against any lateral movement in the housing 2. The cylindrical shaped part 10 is secured Gn both sides against falling out. This is done in a simple manner with safety rings in the ~orm of C-clips. As a variation, it is also possible to configure the coupling barrel with a conically shaped blocking element 10.
This is thus then conical and need be secured only on one side ~3~ 89~

within a corresponding conical bore in the housing.

Figure 4 shows a parti¢ularly elegant housing 2 for a coupling barrel 1. This is produced in one piece from a section of round steel by turning, milling, drilling, and cutting work and has an essentially spherical element 7 and a cylindrical element 8. The cylindrical element 8 incorporates a threaded hole 3 that makes it possible to screw the coupling barrel 1 onto the nipple of a hose or tube end piece~ However, this cylindrical element 8 can, of course, be provided with an external thread. This means that the coupling barrel 1 can be screwed into a bushing or coupler on the e~d piece of a hose or tube. The round element 7 has a receiving bore 5 that is transverse to the longitudinal axis of the cylindrical element 8. The receiving bore 5 is intended to accommodate the locking element 10 that is shown alongside. There is an annular groove 9 in the end edges of the receiving bore 5 and a safety ring 33 can be installed in this in order to secure the inserted blocking element 10 within the receiving bore 5.
Within the round element 7 there is also an elongated slot 18 that extends approximately 90 around the axis of the receiving bore S. This elongated slot 18 runs ints a somewhat larger opening 16 in the housing 2 that serves as a receptacle for the plug 20 in the blocked position of the blocking element lU.

The round element 7 of the housing 2 is flattened parallel to the radial plane of the opening 16. On the opposite side, the round element 7 of the housing 2 is also flattened. Because of this ~lattening, the coupling barrel 1 can be screwed tightly onto a tube nipple with a wrench. In addition, within the interior of the round eIement 7 of the housing 2 there is also a blind hole 25 that is aligned with the axis of the cylindrical element 8. This blind hole 25 is of a greater diameter than the elongated slot 18 and the threaded hole 3.
For this reason, it must be milled or turned out. This blind ,, ~318~
hole 25 accommodates the sealing element 19. The sealing element 19 is essentially in the form of a hollow cylinder and on one side it has an outer side that is curved concavely in one direction so that it lies snugly against the inserted shaped part 10 so as to seal it. In one variation, the blind hole 25 can also be omitted and the blocking element 10 can be sealed hy means that are shown in figure 5. Here, the shaped part 10 has a specially shaped groove 34 on its cylinder wall, this being cut out of the shaped part.

The groove 34 consists of two annular grooves 35, 36 that have a common piece. One annular groove 35 passes about the opening of the diametrical bore 11, whereas the other groove 36 is adjacent in the peripheral direction to the annular groove 35 and, as has been discussed, has a common piece with this. A seal 47 that is specially made is installed in this annular groove 34 and fits exactly in said groove. Using such a seal, the connection between the cylindrical bore 4 and the diametrical bore 11 is effectively sealed when in the working position. On the other hand, in each position of the blocking element 10 that deviates ~rom the working position, the cylindrical bore 4 is sealed.

Finally, figure 6 shows an exploded view of another embodiment o~ the safety coupling according to the present invention, this being particularly suited for high pressure and larger line diameters. In this, the coupling barrel 1 consists of an essentially cylindrical housing 37 that is machined out to approximately one-half to form a hollow cylinder 38 and a further cylindrical shaped part 39 that fits into the interior of the hollow cylinder 38. Within the housing 37, there is a bore 40 and a feed line and an additional bore 41 as a release port. These bores 40, 41 both extend in a direction that is parallel to the axis of the cylinder. The centers of the drillings 40, 41 that also set equidistantly from the axis of the cylinder, so that the drillings 40, 41 are arranged on a ~3~8~

circle khat is concentric, relative to the axis of the cylinder. The opening of the drilling 41, which serves as a feed line, is surrounded by an annular groove 42 that communicates with another annular groove around the outlet of the release drilling. This is achieved by means of an annular groove that encircles both annular grooves but which, as discussed above, communicates with both annular grooves, even though this is not absolutely essential. l'he bore 40 is threaded and this thread makes it possible to screw the coupling barrel onto the nipple on a feed line.

The hollow cylindrical element 38 of the cylinder 37 has an elongated slot 44 in its outer casing and this extends along the peripheral direction of the hollow cylinder 38. At one end, this elongated slot 44 runs into a hole 45, this hole 45 being of a somewhat larger diameter. Relative to the axis of the cylinder, altogether this elongated slot 44 extends through an angle of rotation that corresponds to the angle between the centers of the two bores 40, 41.

The cylindrical shaped part 3g incorporates a curved hole ~6 that comprises, for example, a drilling in the radial plane and a drilling in the axial direction, these two communicating with each other. The drilling that extends in the radial plane is configured similarly to the ~iametrical bore 11 in the locking element 10 as in. figure 2 and i5 configured so as to accommodate a suitable plug 20. The cylindrical shaped part 39 is secured in its position in the interior of the hollow cylinder 38 when inserted by means of the safety ring 33 but remains rotatable within this. To this end, the safety ring 33 is inserted into the groove 4g in the inner side of the hollow cylinder 38. The safety coupling shown in figure 6 can be produced in a particularly simple manner and can be made large without any problem. For this reason, it is particularly well suited for high pressures and large line diameters. It is, of course, understood that at high ~3~8~

pressures and large line diameters the force necessary to rotate the blocking element 39 increases proportionally. This can be remedied in that between the locking element 39 and the safety ring 33 there is an axial pressure bearing so that the frictional forces of the locking element 39 on the safety ring 33 are eliminated, to a great extent. In addition, on its side that remains free, the locking element 10 can also have a lever to assist in locking and unlocking. These means to assist rotation can also be in the form of a rotation shaft that extends in an axial direction and which is provided with a handle.

A further problem that may occur in the case o high pressures and large line diameters is the rapidly increasing force that is needed in order to keep the plug pressed in as it is rotated in the locking element 10. This inward force is necessary in order to release the plug 20 from its detent, which then permits this rotation. In the case of smaller versions of the coupling barrel 1, and at pressures in the order of only a few bars, the plug 20 can easily be pressed in against the existing pressure and, if necessary, against the force of a suitable spring 24 (figure 2) and then into the locking element 10, and thus ~oved out of its detent. It can easily be held in this position by hand. If, as has been discussed above there are high pressures and/or large line diameters or plugs, this becomes a problem for operating the safety coupling. This can be remedied in that the locking element 10 has a bore 49 that intersects in part the drilling that accommodates the plug perpendicular to the axis of this drilling, as is shown in figure 5.

A safety pin 50 can be inserted into this drilling 49 which, when the plug 20 is fully inserted, engages in a special annular groove in the plug 20 and secures this in this position. Then it can be rotated by hand without having to be constantly pressed into the locking element 10.

Claims

1. A plug-type safety coupling for pressure lines, comprising: a plug and a coupling barrel having a housing, a blocking element sealably mounted and secured within said housing, said blocking element rotatable between a blocking position in which the plug may be inserted, and a working position into which the blocking element may be swiveled by means of swiveling the inserted plug, said housing comprising a one-piece shaped part that can be screwed on to a pressure line end piece, and said blocking element having either a cylindrical or a slightly conical shape and having either a straight line or a curved line passing through it for the insertion of the plug, said blocking element being sealed against the housing by means of a sealing forming at least one loop, said seal laying within a corresponding groove taken out of the surface of either the blocking element or out of the inner surface of the housing, and said blocking element being secured in said housing with at least one clamping ring.

2. A plug-type safety coupling for pressure lines according to claim 1, wherein said blocking element has a diametrical bore with a diameter which is enlarged twice in increments and which has in an area of a median diameter at least one annular groove to accommodate a sealing ring for sealing the bore against the inserted plug, and in an area of a greatest diameter of said diametrical bore said diametrical bore accommodates a compression spring which pushes the thickened section of the inserted plug - when the plug is in its working position - into a recess in the receiver drilling for the blocking element.

3. A plug-type safety coupling according to claim 2, further comprising one said annular groove positioned around an opening of said diametrical bore where said diametrical bore is of a smallest diameter, said one annular groove being machined out of a cylinder wall of said blocking element and said one annular groove opening out into another said annular groove that extends in a peripheral direction and has a common piece with said one annular groove, and a suitable formed common sealing element fitting into a common groove formed by said one and said another annular grooves.

4. A plug-type safety coupling according to claim 2, wherein said housing encloses a cylindrical part and a round part adjacent thereto at one end of said cylindrical part, said cylindrical part has a threaded hole and said round part has a drilled hole transverse to a longitudinal axis of said cylindrical part for accommodating said blocking element and which has in end edges of said round part a circular groove, and in said round part there is an elongated slot at right angles to a bore axis of said diametrical bore, which extends through an angle of at least 60° about said round part.

5. A plug-type safety coupling according to claim 4, wherein a slot boring axis of a slot boring at one end of said elongated slot aligns with a threaded hole axis of said threaded hole, and wherein said round part at an opposite end of said elongated slot is flattened externally at a right angle to the axis of the drilling of the elongated slot.

6. A plug-type safety coupling according to claim 4, wherein said round part has at least one release port for releasing the compressed air within said plug before its uncoupling, positioned opposite said elongated slot, and a slot edge of said round part defining said elongated slot opposite said release port has a recess acting as a detent for a plug in order to hold it in the position where it communicates with the release port.

7. A plug-type safety coupling according to claim 6, wherein said housing at the transition form said round part into said cylindrical part, when viewed from said round part, has a blind hole with a blind hole axis of said blind hole extending lengthwise with respect to said threaded hole of said cylindrical part, a blind hole diameter of said blind hole is greater than a slot diameter of said elongated slot and said blind hole diameter is intended to accommodate a sealing element.

8. A plug-type safety coupling according to claim 1, wherein said housing is a cylindrical casing machined out approximately halfway to form a hollow cylindrical cavity, said cylindrical casing has an elongated slot extending along a periphery of said cylindrical casing at a right angle with respect to a cylinder axis of said cylindrical casing by at least 60° around said cylindrical casing, and a remaining part of said cylindrical casing incorporates a release port and a pressure supply bore, both of which have an outlet at a face end into the interior of said hollow cylindrical cavity, an annular groove extending about each of both said outlets, and each said annular groove forming a part of a common annular groove that encloses said annular grooves and accommodates a correspondingly shaped one-piece seal.

9. A plug-type safety coupling according to claim 8, wherein said blocking element is said cylindrical shaped part, one end of which opens out radially from said cylindrical shaped part and an opposite end of which opens out in an axial direction from a face end such that an outlet of said face end, in an operating position, communicates with a pressure line boring, and in the intermediate position, communicates with a release boring in said housing.

10. A plug-type safety coupling according to claim 3, wherein said blocking element has on at least one flat side of said blocking element one of a lever and a pivot shaft with a handle that extends in an axial direction, and said handle is used to rotate the blocking element.

11. A plug-type safety coupling according to claim 4, wherein said housing at a transition from said round part into said cylindrical part, when viewed from said round part, has a blind hole with a blind hole axis of said blind hole extending lengthwise with respect to said threaded hole of said cylindrical part, a blind hole diameter of said blind hole is greater than a slot diameter of said elongated slot and said blind hole diameter is intended to accommodate a sealing element.

12. A plug-type safety coupling according to claim 1, wherein said blocking element has on at least one flat side of said blocking element one of a lever and a pivot shaft with a handle that extends in a radial direction, and said handle is used to rotate said blocking element.