Locking arrangement for a fluid insertion connection

Locking arrangement of a fluid insertion connection between a fluid line and a connection member, in particular between a hydraulic line and a hydraulic cylinder, the fluid line having an insertion part at one end and the connection member being provided with an insertion opening which is open at the circumferential surface of the connection member and receives the insertion part of the line. Furthermore, locking means are provided, which engage on an abutment surface of the insertion part of the fluid line in order to prevent the insertion part of the line from being pulled out of the insertion opening. The locking means comprise a ring, which is positioned around the connection member at the position of the insertion opening and is movable with respect to the connection member. The ring has a slot extending between its inside and its outside, which slot comprises a first slot part, through which the insertion part of the fluid line fits when the first slot part of the ring is aligned with respect to the insertion opening, and a second slot part, which is connected to the first slot part and is narrower than the first slot part, so that when the second slot part of the ring is aligned with respect to the insertion opening, part of the ring engages on the abutment surface of the insertion part which has been inserted into the insertion opening, as a result of which the insertion part is locked so that it cannot be pulled out.

BACKGROUND OF THE INVENTION 
The present invention relates to a locking arrangement for a fluid 
insertion connection. 
A locking arrangement of this kind is disclosed by German Patent 38 17 472. 
In this known locking arrangement, the locking means comprise a U-shaped 
metal clamp, which is pushed into a slot which is formed in the connection 
member parallel to the insertion side of the insertion opening. 
This known locking arrangement has the drawback that the metal clamp is 
complicated to manufacture, which results in undesirably high costs. A 
further drawback is that additional milling operations are required on the 
connection member in order to make a slot for receiving the clamp. It is 
also disadvantageous that a separate clamp, which is relatively small, can 
easily be lost or damaged. 
The present invention aims to eliminate the abovementioned drawbacks and in 
particular to provide a locking arrangement which can be produced 
considerably more cheaply than the known locking arrangement. Furthermore, 
the present invention aims to provide a locking means which can be mounted 
and removed very simply, preferably manually without tools. 
The present invention therefore provides a locking arrangement of the type 
mentioned in the preamble of claim 1, which is characterized in that the 
locking means comprise a ring, which is positioned around the connection 
member at the position of the insertion opening and is movable with 
respect to the connection member, the ring having a slot extending between 
its inside and its outside, which slot comprises a first slot part, 
through which the insertion part of the fluid line fits when the first 
slot part of the ring is aligned with respect to the insertion opening, 
and a second slot part, which is connected to the first slot part and is 
narrower than the first slot part, so that when the second slot part of 
the ring is aligned with respect to the insertion opening, part of the 
ring engages on the abutment surface of the insertion part which has been 
inserted into the insertion opening, as a result of which the insertion 
part is locked so that it cannot be pulled out. 
Further advantageous embodiments of the invention are described in the 
claims and the following description, in which the invention will be 
explained in more detail with reference to exemplary embodiments of the 
locking arrangement of a fluid insertion connection according to the 
invention which are depicted in the appended drawing.

DETAILED DESCRIPTION OF THE INVENTION 
Part of a linear hydraulic cylinder 1, which comprises a metal cylinder 
tube 2 and a metal endpiece 3 which is mounted sealed in one end of this 
cylinder tube 2, is shown in FIGS. 1 and 2. Piston rod 5 of the cylinder 1 
projects into the endpiece 3 through central axial bore 4. For the sake of 
simplicity of reproduction, the usual seals between the piston rod 5 and 
the endpiece 3 are omitted. 
For the purpose of connecting the piston rod-side working chamber 6 of the 
cylinder 1 to a flexible hydraulic hose (not shown), an essentially 
cylindrical insertion opening 7 is formed in the endpiece 3. The insertion 
side of the insertion opening 7 lies on the outer circumference of the 
endpiece 3. 
For the purpose of connecting a flexible hydraulic hose, an elbow-shaped 
coupling component 9, which is depicted in detail in FIG. 4, is provided. 
The coupling component 9 has the flexible-hose receiving part 10 which is 
provided with ribs and grooves, is positioned at right angles and onto 
which a flexible hydraulic hose (not shown) can be pushed. At right angles 
to the part 10, the coupling component 9 has a cylindrical part 11, an 
insertion part 12 of which fits into the insertion opening 7 in the 
cylinder 1. In an embodiment of the coupling component which is not shown, 
the insertion part and the flexible-hose receiving part are in line with 
one another, i.e. in this case it is a "straight" coupling component. 
In order to obtain a good seal between the cylinder 1 and the insertion 
part 12, a circumferential groove 13, in which a sealing ring 14 is 
located, is formed at a distance from the insertion end of the insertion 
part 12. Furthermore, the coupling component 9 has a laterally outwardly 
projecting thickened portion in the form of annular flange 15, which is 
positioned around the insertion part 12 and also extends outwards with 
respect thereto. 
In order to receive the flange 15 of the coupling component 9 in a 
countersunk manner with respect to the circumferential surface of the 
endpiece 3, the insertion opening 7 on its insertion side forms a 
receiving cavity of corresponding dimensions for the flange 15. 
The flange 15 of the coupling component 9, at its side which is remote from 
the insertion end of the insertion part 12, delimits an abutment surface 
16, positioned around the insertion parts 12 in an annular manner, of the 
coupling component 9. In the embodiment depicted here, the abutment 
surface 16 is in the shape of an annular segment of a spherical surface, 
the radius of said spherical surface advantageously corresponding to the 
outer diameter of the endpiece 3 which is of cylindrical design at the 
location of the insertion opening 7. 
Locking means are provided in order to secure the insertion part 12, which 
has been placed in the insertion opening 7 of the endpiece 3, of the 
coupling component 9 against being pulled out. These locking means 
preferably consist solely of a ring 20, which is positioned around the 
part of the endpiece 3 which is of cylindrical design at the location of 
the insertion opening 7. The ring 20 has an inner diameter which is such 
that the ring 20 positioned around the endpiece 3 can be moved manually, 
i.e. is displaceable in the longitudinal direction of the cylinder 1 and 
rotatable about the endpiece 3 of the cylinder 1. 
The design of the ring which is rotatable about the endpiece 3 is depicted 
in detail in FIG. 3. 
The ring 20 is a single body which is preferably produced in the form of a 
(plastic) injection-moulded product. In a very advantageous embodiment, 
the ring 20 is injection-moulded from glass-fibre-reinforced plastic. A 
ring of this kind can be produced considerably more cheaply than the 
U-shaped locking clamps described in DE 38 17 472. Furthermore, the ring 
20 can reliably accommodate the changing stresses which occur as a result 
of the continually altering pressure in the hydraulic system. 
The ring 20 has a slot 21 which extends between its inside and its outside 
and comprises a first slot part 22, through which the insertion part 12 
and the thickened portion 15 formed thereon of the coupling component 9 
fit when the first slot part 22 of the ring 20 is aligned with the 
insertion opening 7 in the cylinder 1. In the exemplary embodiment shown 
in FIGS. 1, 2, 3 and 4, the slot part 22 forms an essentially circular 
opening in the ring 20. Furthermore, the slot 21 comprises a second slot 
part 23 which is connected to the first slot part 22 and is narrower than 
the first slot part 22, so that, when the second slot part 23 of the ring 
20 is aligned with the insertion opening 7, part of the inside of the ring 
20 engages on the abutment surface 16 of the insertion part 12 which has 
been placed in the insertion opening 7. As a result, the insertion part 12 
is effectively locked so that it cannot be pulled out. 
In the exemplary embodiment shown in FIGS. 1, 2, 3 and 4, the slot part 23 
forms an essentially circular cutout having a diameter which is slightly 
larger than the diameter of the cylindrical portion of the coupling 
component 9 projecting through the slot part 22. 
The slot 21 in the ring 20 furthermore also comprises a third slot part 24, 
which connects the first slot part 22 and the second slot part 23 to one 
another. The third slot part 24 delimits at at least one location a narrow 
passage 25 having a dimension which is smaller than the corresponding 
dimension of the part of the coupling member 9 (dimension "d", cf. FIG. 3) 
which passes through the third slot part 24 when the ring 20 is moved. In 
practice, the narrow passage only has to be slightly narrower than the 
corresponding dimension of the part of the coupling component passing 
through it, for example 0.2 mm for a diameter of the cylindrical part 11 
of approximately 4 mm, in order to provide the surmountable resistance. In 
this example, the third slot part 24 is an essentially straight channel 
with parallel boundary walls. In a variant embodiment (not shown), the 
third slot part can be a straight channel which is narrowed only locally. 
In FIG. 5, it can be seen that the third slot part can also be of bent 
design. 
The ring 20 is designed such that the boundary walls of the narrow passage 
25 can move apart in an essentially elastically resilient manner for the 
passage of the insertion part 12. In this example, this is advantageously 
realized by a suitable selection of the dimensions of the ring 20 and the 
stiffness of the material of the ring 20. In an embodiment which is not 
shown, the elastically resilient movability of the narrow passage of the 
third slot part could be obtained by designing the ring to be weaker near 
this narrowed section, for example by providing additional slots in the 
region of the narrowed portion or by providing a locally thinned section. 
In order to receive the ring 20, the endpiece 3 of the cylinder 1 only has 
to be of cylindrical design at the location of the ring 20, which can be 
achieved simply and inexpensively. 
The spherical design of the abutment surface 16 means that good securing is 
achieved in every position of the coupling component 9. 
Preferably, the ring 20 is designed such that it is possible to rotate the 
ring 20 around the endpiece 3, for the purpose of securing or also 
unlocking the coupling component 9, manually without difficulties. 
FIG. 5 shows a ring 50 which is suitable for the same purpose as the ring 
20 in FIGS. 1 and 2. The ring 50 likewise has a slot 51 with a first slot 
part 52, a second slot part 53 and a third slot part 54 connecting these 
two slot parts 52, 53. The dimensions of the first slot part 52 make it 
possible for an insertion part of a line to be inserted in this slot part 
52 in a corresponding insertion opening. The second slot part 53 has 
dimensions which are such that, when the insertion part of the line is 
inserted in the insertion opening and the second slot part 53 is aligned 
with respect to this insertion opening, the insertion part of the line is 
effectively prevented from being pulled out of the insertion opening. 
The difference between the ring 50 and the abovedescribed ring 20 is that 
the third slot part 54 here does not form a straight channel, as in the 
case of the ring 20, but is designed as a (sharp) bend. In the embodiment 
shown, the third slot part 54 comprises two sections, sections 55 and 56 
respectively, which adjoin one another at an angle. As a result of the 
shape of the third slot part 54 differing from the straight channel shape, 
the ring 50 has to be moved in a specific manner in order to lock or 
unlock an insertion connection which is thus secured. The risk of the ring 
50 being inadvertently unlocked is reduced compared to the ring 20. This 
risk can obviously be reduced further by providing the third slot part 54 
with a narrowed portion, as described above, in this case too. 
FIG. 6 shows a ring 60 which differs from the ring 20 solely by the fact 
that the ring 60 is essentially rectangular and is intended to be 
positioned around a rectangularly designed part of a connection member. 
Owing to this rectangular shape, it is not possible to rotate the ring 60, 
for which reason the slot 61 extends in the axial direction of the ring 
60.