A plug connection of the aforementioned kind is known from WO 2006/018384 A1, which is based on a known locking principle, according to which a C-shaped retaining section of a retaining part encases and thus fixes retaining ribs of coupling parts in a positively locking manner. The retaining part is configured and is or can be undetachably preassembled in such a way that it is axially fixed with very little play and radially securely fixed, on the one hand, and can be elastically radially moved, on the other hand, in order to reduce the danger of loss of the retaining part and simplify an assembly, in particular also in applications in which only a small surrounding space is available at the assembly location, or in which at least one valve is to be integrated in the coupling parts. The retaining part in the area of the retaining section as well as the retaining rib of the other coupling part must be configured in adaptation to each other in order to form a positive snap-on connection acting in the insertion direction, in such a way that the retaining section is moved radially outwardly by the retaining rib moving relative thereto when the coupling parts of the retaining section are plugged into each other and subsequently encompasses the retaining rods of the two coupling parts for locking purposes by means of the radial return movement toward the inside in the inserted state. The retaining part is preferably configured as a one-piece annular part having an axially and radially continuous slot interruption at one point of the periphery. This known plug connection makes possible an easy, fast and convenient as well as also secure single-hand assembly. In order to reduce the danger of detachment when the retaining part is detached from the coupling parts, WO 2006/018384 provides to undetachably connect the retaining part to a coupling part via an additional, in particular ribbon-like or string-like locking element attachable at one end to the coupling part and at the other end to the retaining part.
A plug connection of a similar kind as the one initially described is known from WO 2009/156399 A1. In this document, the additional locking element is considered disadvantageous. In order to facilitate a positioning of the retaining part and the reassembly with low danger of detachment of the retaining part and with reduced complexity, while eliminating such an additional locking element, the retaining part is provided with a ring-shaped configuration, wherein the retaining part is fixed on at least one of the two coupling parts with a circumferentially closed annular contour in a preassembled state and encompasses at least one of the two coupling parts in the assembled state. The retaining part in this case can be preferably undetachably preassembled on a plug part, wherein it can be fixed in two positions, the preassembly position and the assembly position. It arrives from the preassembly position into the assembly position by means of a radial displacement or for disassembly from the assembly position back into the original position by means of a mutually opposite displacement. A particularly preferred configuration herein has an annular opening enclosed by the annular contour and is formed by a first circular partial opening with a central point in the area of the retaining section and a second circular partial opening, whose central point is located within a retaining section of the retaining part, wherein the two partial openings intersect. The retaining part has necessarily an enlarged radial extension, which is considered particularly disadvantageous when only very little installation space is available.
It is an object of the invention to improve a plug connection of the initially mentioned kind as well as a retaining part for such a plug connection in such a way that the assembly and disassembly can be further simplified, while retaining the advantages of the known locking principle, and namely also in applications in which only a very small surrounding space is available at the installation location in particular for the disassembly, wherein a low danger of detachment of the retaining part is to be ensured.
According to the invention, this is achieved for the plug connection and the retaining part by configuring the collars of the retaining part with different size and/or shape in such a way that a collar, which abuts against the retaining rib of one coupling part in assembled state, releases this retaining rib of the coupling part out of the assembled state with an outward radially elastic movement of the retaining section, while the other collar still engages at least in some areas behind the retaining rib of the other coupling part against which it abuts.
The advantages of the known generic locking principle are combined, on the one hand, with the advantages of a snap-fit principle in the plug connection according to the invention. If the retaining part is undetachably preassembled on the one coupling part, the other coupling part only needs to be axially inserted for assembly, which makes possible a simple, fast, easy to operate and secure automated or single-hand assembly. There is no need, on the other hand, to carry out a highly space-consuming radial displacement for disassembly of the retaining part in the embodiment according to the invention when the connection is disengaged, which is of particular advantage at installation locations with only small surrounding space in radial direction. One particular advantage is the possibility for single-finger unlocking.
A radial expansion, which again suffices to axially draw a coupling part out of the connection, can preferably be produced at the retaining part according to the invention by actuating or pressing the pressure-loaded area in an—especially elastic—actuating area of the retaining element located circumferentially between two retaining sections. One of the two collars of the retaining section, which additionally engages behind the retaining rib of the other coupling part against which it abuts in assembled state, remains axially fixed in an annular groove of the coupling part, whereby the retaining part is further retained on this coupling part.
A comparable technical solution for a plug connection similar to that of the above-mentioned type has also already been proposed in the German patent application DE 10 2012 104 288.8, in which however the retaining part does not have an open, but a circumferentially closed annular contour. In this previously proposed technical solution, it can be particularly provided that one of the two collars of the retaining part is provided with a socket-like circumferentially running, preferably additionally radially inwardly curved attachment, by means of which it differs in size and shape from the other collar and by which it protrudes—seen in axial projection—with respect to the other collar. Aside from this attachment, both collars are otherwise preferably configured identically, in particular—seen in plan view—preferably congruent. While the radial expansion, which can be produced, for example, also by means of pulling or levering with a tool in the actuation area, takes place in connection with an integral deformation of the entire retaining part, only a spreading of the retaining sections with respect to each other takes place according to the invention as a result of the annular contour, so that a detachment of the retaining part from the coupling part on which it is supposed to remain can be even more securely prevented.
The distance of the actuating section to the longitudinal axis of the coupling parts or also the distance to the collars of the coupling parts, in particular to an outer edge of the collar of a coupling part configured as a plug part, can advantageously be configured smaller than was proposed by the earlier technical solution by means of the expansion mechanism of the spreading. This is important insofar as the distance of the actuating section to the collars of the coupling parts represents the actuation path for release of the connection and determines the size of the installation space of the plug connection.
The open annular contour of the retaining part can be formed in particular in that the retaining part is provided with a slot on the side located diametrically opposite to the actuating area.
In contrast to the relatively large slot interruption, such as the one provided on the retaining part with a plug connection of the kind known from WO 2006/018384 A1, this slot is characteristically only very small. It can preferably have a size than can be preferably specified—with reference to a longitudinal axis of the retaining part—by means of an angle at center that is smaller than 15°, preferably smaller than 5°.
According to the invention, the two collars of the retaining part are preferably configured identically only in some areas—seen in plan view—and are especially preferably not congruent. They can especially have different wrap angles—with indeed approximately the same width and thoroughly identical circumferential, in particular circular arched curvature—for the coupling part located between them and for this reason a different circumferential length.
Other advantageous embodiment features of the invention are included in the following description.