Plug fitting and assembly method

Abstract

The invention relates to a plug fitting (1) for externally-sealing connecting, usually in a tool-free manner, to a pipe end (32) with a smooth outer side, wherein the plug fitting (1) has a main body (2) for receiving the pipe end (32) and a coupling sleeve (22) which is adjustably connected to the main body (1) in the axial direction for example by means of a thread (4), as a result of which the plug fitting (1) can be brought into different configurations. A basic configuration (G) predetermined in the preassembly state is provided, in which, if the pipe end is within the tolerances (e.g. is not too unround), the connection can be produced so as to be permanently sealing by simply inserting the pipe end (32). If, however, tightness problems occur, a subsequent pressing configuration (NP) can be set to improve the sealing effect. Furthermore or alternatively, a disassembly configuration can be provided. The plug fitting (1) has a slotted retaining element (28) with barbs and a sealing element (20). The invention also relates to an assembly method for a plug fitting (1) with the possibility of subsequent pressing.

Description

[0001] Push-in fitting and assembly procedures

[0002] The present invention relates to an externally sealing push-in fitting for a quick connection to externally smooth pipe ends of various types, such as with socketless water, sewage, gas or district heating pipes made of plastic or with smooth pipes made of copper, steel, aluminum or (multi-layer) composite material, whereby the connection can basically be made without the use of tools by pushing the push-in fitting onto the pipe end and then generally providing a permanent seal.

[0003] Push-in fittings are becoming increasingly popular due to their quick and tool-free assembly, particularly, but not only, in the do-it-yourself sector, and are widely replacing traditional connection methods such as soldering or compression joints.

[0004] Press-fit connections typically require a special, cost-intensive pressing tool with dedicated pressing jaws for each pipe diameter to be pressed, as well as sufficient working space to position this tool at the installation site, which limits the application possibilities of the pressing in difficult-to-access and tight installation situations. With press-fit connections, there is also the latent risk that the pressing could have been carried out inadvertently or incompletely, which is why press-fit connections have been developed that are always leaky when not pressed. Another disadvantage of the press-fit connection is that it is usually impossible to remove without causing damage due to the plastic bond between the pipe end and the press sleeves.

[0005] The term "fitting" refers to all possible connecting pieces for a pipe end, e.g., for changing the direction (e.g., 90° or 30° angle), for (plug-in) connections with other pipe ends (e.g., T-pieces), or for creating one or more other types of connections, e.g., via a screw thread. In particular, one and the same fitting can also be designed for a plug-in connection with multiple pipe ends by using multiple pieces of the individual elements described below to create the connection. In conventional plug-in fittings, the tensile strength of the connection is usually provided by a retaining element, e.g., a slotted ring made of spring steel with internal teeth in the form of barbs that grip the outside of the pipe end when the fitting is pushed onto it.

[0006] When tension is applied to the pipe end, the barbs tend to penetrate further into the outer circumference of the pipe ("self-blockage"), so that the push-in fitting can no longer be removed from the pipe end or can only be removed with great force and often no longer without causing damage.

[0007] The actual sealing of such plug-in fittings, ie the prevention of the escape of the liquid or gaseous medium transported in the pipe, is ensured in known externally sealing plug-in fittings on the outside by means of a sealing element, in particular by means of at least one O-ring made of an elastic material, such as rubber or plastic.

[0008] This O-ring extends radially into the insertion path of the pipe end by a predetermined amount, allowing the pipe end to still be inserted over the O-ring. The O-ring is expanded by a predetermined amount by the inserted pipe end, or compressed within the groove in which the O-ring is located. The O-ring then presses fully against the outer wall of the pipe with a certain radial preload.

[0009] This blocks the leakage path leading from the front end of the pipe end - which is normally not sealed against the fitting - along the outside of the pipe (both on the outside of the pipe and also at the bottom of the O-ring groove) and the connection is completely tight.

[0010] Externally sealed fittings have the advantage over fittings with a nozzle extending into the pipe end (internally sealed) that the cross-section in the fitting area is not reduced, thus largely avoiding increased flow losses in the fitting area. With conventional internally sealed press fittings with nozzles, the diameter reduction for small pipe diameters can be up to 50% (due to the fact that the support sleeve must be particularly stable against the pressing forces applied), which can obviously lead to considerable flow resistance and thus pressure losses. In principle, the externally sealed seal with known plug-in fittings functions reliably and is also long-term stable – with the limitations described below.

[0011] However, an essential criterion for tightness is compliance with specified tolerances for the pipe end to be connected.

[0012] In many cases, leaks are caused by the pipe end being out of round (e.g., elliptical). Such problems can arise during transport or storage of the pipes due to excessive mechanical stress, or a non-round profile can occur when cutting to length with tools that cause excessive crushing of the pipe end.

[0013] Such out-of-roundness - as long as it is located in the area in which the O-ring is to come into contact - can only be compensated to a limited extent by the O-ring, since the permissible radial compression of an O-ring is limited on the one hand by the O-ring itself and the criterion that the pipe end must still be able to be inserted past the O-ring by hand.

[0014] Other causes of possible leaks could be non-vertical pipe cuts or cuts that are not sufficiently deburred, whereby the burrs can damage the O-ring or particles can become lodged between the outside of the pipe and the O-ring.

[0015] Damage or contamination of the pipe's outer surfaces can also lead to leaks. Less commonly, production-related dimensional deviations in the pipe's outer diameter are the cause of leaks in push-in fitting connections.

[0016] Another problem with conventional push-in fittings is that once a pipe end has been inserted, it is often no longer possible to remove it from the fitting without causing damage.

[0017] There are push-in fittings that can be released with special tools (special pliers) by removing the self-blocking action of the slotted retaining element with barbs, allowing the pipe end to be pulled out again. However, as mentioned above, this requires a specially adapted tool, usually dependent on the pipe diameter, which is not always readily available. In many cases, the pipe end is damaged and mechanically deformed by the retaining element's barbs, some of which are still active, to such an extent that it would no longer be suitable for reconnection.

[0018] In practice, the problems described above when dismantling commercially available push-in fittings mean that the pipe must be cut to length to create a new push-in connection. This usually results in a previously assembled pipe section being too short, so the entire pipe section must be reassembled and reconnected on both sides. This is particularly disadvantageous when a T-shaped push-in fitting needs to be corrected, as this often requires three new pipe sections to be manufactured and connected.

[0019] The invention is based on the object of providing a push-in fitting and an assembly method therefor, by means of which a quick, simple and reliably sealing, essentially tool-free connection is made possible both in normal cases and in exceptional cases, such as when pipe ends do not fully correspond to the specified tolerances and / or in the event of a need for correction.

[0020] The above-mentioned object is achieved by means of a plug-in fitting having the features of patent claim 1 or by means of a method having the features of patent claim 14.

[0021] Advantageous embodiments of the invention are described in the dependent claims.

[0022] A push-in fitting according to the invention for a sealed connection to at least one pipe end with a smooth exterior comprises at least the following elements: a base body with an approximately cylindrical cavity for internally receiving the pipe end to be connected, wherein the base body has an internal stop against which the pipe end to be connected abuts when connected; and a union sleeve that is connected to the base body so as to be adjustable in the axial direction, whereby the push-in fitting can be brought into different configurations by this adjustment. As will be the case below, the term "axial" refers to the direction of the central axis of the pipe end, whereby this axis simultaneously represents a rotational symmetry axis for several elements of the fitting.

[0023] The term "radial" shall mean a direction perpendicular to the said central axis.

[0024] The two elements, base body and union sleeve, should therefore be axially adjustable relative to each other, for example by means of a threaded screw connection provided between the components, as will be explained further below.

[0025] One idea of ​​the invention is that in a setting of the axial position between the base body and the union sleeve, referred to as the basic configuration, which corresponds to the delivery or at least the pre-use or pre-assembly state of the fitting without further user intervention, a plug-in connection with pipe ends that correspond to specified mechanical tolerances can be produced in a long-term sealing manner by simply plugging in (without tools).

[0026] The aforementioned "specified mechanical tolerances" refer to the factors mentioned above for the quality of the pipe end to be connected, which are necessary for a permanently tight plug-in connection, in particular a pipe end cross-section that is not too irregular, a straight, properly deburred cut surface and a smooth, undamaged pipe outer wall with the specified external dimension.

[0027] In addition to this basic configuration, according to the invention, either a post-pressing configuration can be set, which allows optional post-pressing to improve the sealing effect, in particular in the case of a pipe end that does not or does not fully comply with the mechanical tolerances and cannot be reliably sealed in the basic configuration.

[0028] This optional re-pressing option also allows for slightly larger tolerances for the fitting itself, thus reducing manufacturing costs. Re-pressing is still possible in the event of an unfavorable match between the pipe end and the fitting's tolerances. In addition to or as an alternative to the re-pressing configuration, a disassembly configuration can be implemented in which the union sleeve is removed from the base body without the use of a special tool, allowing the pipe end to be removed from the push-in fitting without damaging it if necessary.

[0029] The term "special tools" refers in particular to pliers supplied specifically for the fittings to release the self-blocking device. Wrenches, screwdrivers, or pipe wrenches of different sizes are not considered special tools. Such standard tools are generally required for disassembling the union sleeve within the scope of the invention.

[0030] The plug-in fitting according to the invention further comprises a preferably slotted retaining element with radially inwardly directed barbs, which can self-lock a pipe end to be connected.

[0031] Furthermore, the plug-in fitting according to the invention has on the inside of one of its sleeves - preferably on the inside of the base body - a sealing element (e.g. one or more O-rings) which seals the pipe end to be connected on the outside, which sealing element can already reliably seal pipe ends in accordance with the mechanical tolerances in the basic configuration and which, if a post-pressing configuration is provided, exerts a stronger radial sealing force on the pipe end in this post-pressing configuration than in the basic configuration.

[0032] Bringing the push-in fitting into the post-pressing configuration - via a suitable mechanical coupling, see below and preferably without the need for special tools - therefore at least results in an increase in the sealing element compression.

[0033] The user of the fitting according to the invention can therefore initially establish the plug connection in the basic configuration without tools.

[0034] If the user then discovers a leak during a subsequent pressure test or during regular operation, or if the user suspects that the connection may be leaking, for example, because the pipe was not cut to length satisfactorily, they can place the fitting into a post-pressing configuration in which increased sealing forces are applied. By only setting the post-pressing configuration after the pipe end has already been inserted in the basic configuration, problems caused by increased radial pressure forces on the sealing element are avoided, particularly blocking the insertion of the pipe end or an increased risk of damage to the sealing element when inserting the pipe end.

[0035] To prevent accidental adjustment from the basic configuration provided during delivery, pre-use, or pre-assembly, a locking and / or marking element is also provided so that any adjustment from the defined basic configuration is clearly perceptible and does not occur accidentally or unintentionally (before or after assembly). This is because an inadvertent change from the basic configuration to a post-pressing configuration could make inserting the pipe end more difficult and potentially expose the sealing element to the risk of damage. An inadvertent change to a disassembly configuration could jeopardize the tightness or stability of the pipe connection.

[0036] In a preferred embodiment, the base body and the cap sleeve can be rotated relative to one another by means of a threaded connection or by means of a bayonet-type element and can thus be axially displaced and brought into the different configurations.

[0037] In order to be able to operate a thread or a bayonet lock, the base body and / or the union sleeve preferably have attachment structures for suitable conventional adjustment tools, e.g. an external hexagon for a suitable open-end wrench, knurling for the attachment of pliers or a radial (threaded) bore for the attachment of pin-shaped tools, by means of which the two elements can be rotated against each other.

[0038] Alternatively, other axial distance adjustment options are also conceivable, e.g. by means of adjusting screws arranged parallel to the axis.

[0039] The adjustment between the base body and the union sleeve, i.e., the change between different configurations—which is generally only necessary for a configuration change from the basic configuration—can preferably be performed without special tools (i.e., using only standard tools such as open-end wrenches, pipe wrenches, etc.). If a very fine thread is provided, tool-free adjustment "by hand" might also be conceivable in certain configurations, although the subsequent compression forces required and any locking forces that may have to be overcome (see below) would likely make adjustment without an additional tool lever rather difficult. Furthermore, the adjustment is preferably designed to be completely reversible and non-destructive.In contrast to press connections, there is no significant plastic deformation in the area of ​​the sealing element, but rather an essentially elastic deformation, so that if necessary, the post-pressing or disassembly configuration can be changed back to the basic configuration.

[0040] In a preferred embodiment, the sequence of elements in a push-in fitting according to the invention is selected such that, starting from the stop on the base body side and axially in the direction of the pipe, the sealing element is provided first, surrounded by the base body, followed by the slotted retaining element, surrounded by the union sleeve. The sealing element is thus located near the stop, so that bending forces acting on the pipe end influence the sealing effect of the sealing element as little as possible, and the pipe end is optimally supported by the surrounding cylindrical hollow body of the fitting up to the sealing element.

[0041] Preferably, the sealing element is designed as at least one O-ring arranged in an inner groove of the push-in fitting, which in the pre-assembled state in the basic configuration projects radially into the insertion path of the pipe end to be connected and is compressed by the pipe end when inserted in such a way that a relatively smooth insertion ("by hand") of the pipe end over the O-ring up to the stop is possible with a simultaneous permanent radial sealing effect, at least if the pipe end corresponds to the mechanical tolerance specifications.

[0042] If a post-pressing configuration is provided, it can be provided in a preferred embodiment of the invention that an axial displacement of the union sleeve from the basic configuration to the post-pressing configuration causes a reduction in the groove width of the groove for receiving the O-ring, whereby the O-ring is compressed axially (more strongly) and the radial sealing forces acting on the outside of the pipe end are thus increased, so that existing tolerances, e.g. out-of-roundness, can then still be reliably sealed by the O-ring.

[0043] The aforementioned reduction of the groove width in the post-compression configuration can be achieved by means of a spacer sleeve, one end face of which rests laterally against the O-ring arranged in the region of the base body, and the other end face of which abuts the union sleeve, so that an axial movement of the union sleeve relative to the base body (during which the base body and union sleeve are moved towards each other) is converted into an axial compression of the at least one O-ring, wherein the maximum radial compression of the at least one O-ring is mechanically limited preferably to a maximum of 30% of the cord width of the O-ring, most preferably to a maximum of 20%. The limitation to be preferably implemented results from the maximum permissible load data of the O-ring used. By limiting the additional compression, mechanical failure of the O-ring due to excessive post-compression is avoided.

[0044] The above-mentioned spacer sleeve may have a cylindrical sleeve shape or a cylindrical sleeve shape with an L-shaped cross section and a stop collar in the region of the abutment area of ​​the union sleeve.

[0045] Preferably, the axial compression of the O-ring caused by the radial compression of the O-ring when inserting the pipe end is also applied to the slotted retaining element via the spacer sleeve with an axial preload. This possible additional function of the spacer sleeve, which is already effective in the basic configuration, allows the barbs of the slotted retaining element to be brought into direct contact with the outer pipe wall when the pipe end is inserted, so that the slotted retaining element holds the pipe end securely through self-locking with minimal axial play when tensile load is applied to the pipe end.

[0046] In addition to a single O-ring as a sealing element, one embodiment of the invention can also provide two consecutive O-rings (or more) to achieve the specified sealing effect or to provide a redundant sealing layer in the event of one of the O-rings failing. In the case of two O-rings, these are preferably separated by an axially movable separating disk, so that uniform axial and radial compression of both O-rings can occur during subsequent compression.

[0047] The self-locking action of the preferably slotted retaining element is preferably achieved or supported by the fact that it has a cone on the outside, which interacts with a complementary cone on the inside of the union sleeve in such a way that the pipe end is self-lockingly locked. Due to the preferably provided slotting, the retaining element can slide along this cone and, when subjected to tensile stress at the pipe end, reduces its inner diameter, so that the barbs may work deeper into the pipe end, making non-destructive removal generally impossible.

[0048] In this context, it can preferably be further provided that, upon axial displacement of the cap sleeve relative to the base body during the subsequent compression, the retaining element is also subjected to greater radial compression. This can be achieved by the spacer sleeve abutting the retaining element, which transmits the axial compression force of the sealing element to the retaining element, as explained below with reference to the figures.

[0049] To ensure that the standard basic configuration, which is usually preset upon delivery of the fitting, is not inadvertently adjusted towards the post-pressing configuration or - which would be even more detrimental to the sealing effect - towards the disassembly configuration (e.g. during storage handling of the push-in fitting), a detent can be provided as a locking and / or marking element between the base body and the union sleeve. This detent can be perceived and overcome upon axial displacement between the elements and clearly marks the basic configuration for the user. When adjusting the axial distance, the user must therefore overcome a certain, noticeable locking resistance in order to move out of the basic configuration. An additional detent can also be provided in a post-pressing configuration.

[0050] Furthermore, an annular elastic element can be provided in an external groove between the base body and the cap sleeve to achieve an surmountable frictional connection between the base body and the cap sleeve. This elastic element thus acts as a type of anti-twist device to prevent unintentional adjustment from the basic configuration, acting as a locking and / or marking element. Increasing compression of the elastic element when moving into the post-compression configuration also generates increasing rotational resistance (until the aforementioned stop is reached), allowing intermediate positions for post-compression to be set.

[0051] In one embodiment of the invention, the elastic element mentioned can additionally assume an indicator function in that the annular elastic element is visible in the basic configuration and is completely or partially concealed by a projection in a post-pressing configuration, thereby clearly indicating whether the push-in fitting is in the basic configuration or in a post-pressing configuration. For this purpose, the elastic element can, for example, also be made of a strikingly colored material. This allows the user to see at a glance which fittings have already been subjected to the post-pressing option, and before assembly, it would be immediately apparent if a fitting were not in the basic configuration.

[0052] Furthermore, within the scope of the present invention, a method for sealingly connecting a pipe end to a push-in fitting is proposed, wherein the push-in fitting can optionally be brought into a post-pressing configuration that allows an increase in the contact pressure of the sealing elements of the push-in fitting compared to a basic configuration. The method can be used, for example, with a push-in fitting as described above, but could also be used for other push-in fittings if they offered an optional post-pressing option.

[0053] The method comprises the following steps: a) inserting the pipe end to be connected into the push-in fitting in the basic configuration without tools, whereby a permanently tight connection is already established for pipe ends that comply with the mechanical tolerances, and b) if after step a) - immediately or at a later time - a leak is detected or predicted; bringing the push-in fitting into the post-pressing configuration to achieve and / or ensure permanent tightness.

[0054] If the tightness cannot still be achieved by the subsequent pressing in step b), the push-in fitting can be put into the disassembly configuration and, for example, the pipe end can be replaced.

[0055] Preferably, the post-compression step for creating the sealing connection is not mandatory, but can only be used optionally.

[0056] The invention is explained in more detail below with reference to the embodiments shown in the drawings.

[0057] They show:

[0058] Figure 1 shows a half axial section of a loosely assembled push-in fitting without a pipe end inserted into it;

[0059] Figure 2 shows a half axial section of the push-in fitting after insertion of a pipe end and in the basic configuration;

[0060] Figure 3 shows a half axial section of the push-in fitting with the pipe end inserted in a post-pressing position;

[0061] Figures 4 to 6 are representations analogous to Figures 1 to 3 of a modified embodiment of the invention;

[0062] Figures 7 to 9 are representations analogous to Figures 4 to 6 of a further modified embodiment of the invention; and

[0063] Figure 10 shows a half axial section of the push-in fitting in a design with double O-rings.

[0064] The externally sealing push-in fitting shown in Figure 1 in a semi-axial section and designated overall by 1 has a central longitudinal axis (not shown), which can be imagined as a horizontal line below Figure 1; this also applies to the other figures. The fittings 1 in the figures each have a pipe connection area in the right-hand part, described in more detail below, and a connection area 6 in the left-hand part, which in Figures 1 to 3 is designed only as an example as an externally circumferential threaded connection 4.

[0065] The invention encompasses all possible connection area variants for one or more pipe ends, e.g., for changing the direction (e.g., 90° or 30° angle), for (plug-in) connections with other pipe ends (e.g., T-pieces), or for creating one or more other types of connections, e.g., via a screw thread. For example, instead of the threaded connection area shown in the figures, a mirror-symmetrical pipe connection area with the same or different cross-section (in the sense of a coupling piece) can be provided.

[0066] As further evident in the figures, the fitting 1 according to the invention preferably has no cross-sectional constriction in the fitting area, which is made possible by the external sealing concept explained below. If, for example, adaptation to different pipe diameters is desired, a cross-sectional constriction can of course be provided regardless.

[0067] The plug-in fitting 1 comprises a base body 2 with an approximately cylindrical cavity (with certain steps described in more detail below) for receiving the pipe end 32 to be connected (Figure 2).

[0068] From the connection area 6, the outer diameter of the base body 2 decreases in an outer step forming an outer groove boundary 8 to a cylindrical section with a smaller outer diameter, which is provided with an external thread 5a indicated by dashed lines closer to its axial end and ends in an end face 10 of the base body 2.

[0069] Approximately at the beginning of the connection area 6, the inner diameter of the base body 2 increases from the inner surface of the generally hollow-cylindrical section of the base body 2 in a second inner stage, which forms an annular stop 12 for the pipe end 32 to be connected, to an intermediate section with a cylindrical inner surface 14 and an inner diameter matching the outer diameter of a pipe 32 to be connected. The inner diameter of the intermediate section 14 increases in a first inner stage 16 to an end section 18 with a cylindrical inner surface and an inner radius that is larger than the inner radius of the intermediate section by less than the cord thickness of an O-ring 20 fitting into the cylindrical inner surface of the end section 18. The end section 18 ends at the end face 10 of the base body 2.

[0070] The plug-in fitting further comprises a union sleeve 22, whose outer diameter may be equal to or larger than the outer diameter of the base body 2, and whose outer circumference may be hexagonal, for example. The union sleeve 22 has a bore at one axial end provided with an internal thread (indicated by dashed lines) that matches the external thread 5a of the base body 2, with which it is loosely screwed onto the base body 2 in the figure. Overall, the threaded connection 5a, 5b between the base body and the union sleeve 22 is designated 4.

[0071] At an end facing away from the base body 2, the inner diameter of the bore of the union sleeve 22, provided with an internal thread 5b, decreases to a smaller inner diameter in a sleeve step 24. This smaller inner diameter gradually decreases with increasing distance from the internal thread 5b in the axial direction to form a conical inner surface 26, which is adjoined by a short cylindrical end section whose inner diameter is as large as, or slightly larger than, the inner diameter of the intermediate section. The pitch of the conical inner surface 26 is exaggerated in the figures and is actually only a few degrees relative to the longitudinal axis.

[0072] The push-in fitting 1 further comprises a retaining ring 28 having a conical outer surface 30 corresponding in circumference and pitch to the conical inner surface 26 of the union sleeve 22. Inwardly directed barbs are formed on a generally cylindrical inner surface of the retaining ring 28, forming a type of shark tooth pattern, with the barbs projecting radially inward to such an extent that their inner diameter is slightly smaller than the outer diameter of a pipe 32 to be connected. The retaining ring 28 is slotted and can move within limits along the inner cone 26 of the union sleeve 22 with a variable diameter.

[0073] The plug-in fitting further comprises a spacer sleeve 34 with a longitudinally L-shaped wall cross-section, although other designs of the spacer sleeve 34 (simple ring) are also possible. The spacer sleeve 34 can be a turned metal part or an injection-molded plastic part.

[0074] An axial section of the spacer sleeve 34, which forms a long leg of the L-shape, fits with clearance into the cylindrical inner surface of the end section 18 of the base body 2 and ends with an end face 36 that forms a groove wall for the O-ring 20. An axial section of the spacer sleeve 34, which forms a short leg of the L-shape, including its connection to the long leg, has an outer diameter that is larger than the inner diameter of the end section and slightly smaller than the inner diameter of the internal thread 5b in the union sleeve 22.

[0075] The inner surface of the end portion 18 of the base body 2 has an axial length which is less than the cord thickness of the inner O-ring 20 greater than the axial length of the axial portion of the spacer sleeve 34 which forms the long leg of the L-shape without its connection to the long leg.

[0076] The push-in fitting also comprises an outer elastic element 38 (usually also an O-ring) which fits onto the cylindrical section with a smaller outer diameter adjoining the outer step 8 of the base body 1.

[0077] The base body 2 and the cap sleeve 22 can be made of metal or of a plastic (as an injection-molded part), depending on the specified mechanical requirements.

[0078] The specific dimensioning, number, and hardness of the O-rings 20, as well as the overall dimensioning of the push-in fitting 1 according to the invention, depend on the pipe diameter to be pressed, the desired compressive strength, the pipe material (especially the outer surface), the wall diameter, and the rigidity of the pipe to be pressed. Even though the fitting according to the invention is generally suitable for a wide range of pipe materials and diameters, different fittings may be required for different pipe types (e.g., purely metallic pipes vs. plastic pipes).

[0079] In the state shown in Figure 1, the push-in fitting 1 is loosely assembled and is in a basic configuration G, which is indicated by the marked axial distance between the base body 2 and the union sleeve 22 in Figure 1. In a relaxed state, the retaining ring 28 sits loosely between the inner surface 26 of the union sleeve 22 and an end face 42 of the section of the spacer sleeve 34, which forms the short leg of the L-shape.

[0080] To connect to an end portion of a pipe 32, the push-in fitting 1 is pushed axially onto the pipe 32 "by hand" (without tools) (or, depending on the installation situation, the pipe end 32 is pushed onto the fitting conversely), whereby the pipe end 32 presses the inner O-ring 20 against the inner surface of the end section 18 and thereby compresses it radially until an end face of the pipe 32 strikes the stop 12, as shown in Figure 2. The fitting 1 is still in the basic configuration G.

[0081] The components of the push-in fitting are designed in such a way that in the state thus achieved, the O-ring 20 is radially compressed to such an extent (see the slightly elliptical cross-sectional shape of the O-ring 20 in Figure 2 in comparison to the round initial shape in Figure 1 ) that the O-ring 20 then seals the pipe end 32 on the outside in a long-term stable manner when the pipe end 32 meets the mechanical tolerance specifications.

[0082] In particular, the O-ring 20 blocks a leak path that extends from the pipe end that rests against the stop (unsealed) on the outside of the pipe end 32 along the gap between the pipe end 32 and the base body 2, by the O-ring 20 that rests flat against the outside of the pipe and at the same time rests flat against the groove base in the base body 2.

[0083] By compressing the O-ring 20, as shown in Figure 2, a radial pressure is exerted on the spacer sleeve 34, which abuts against the retaining ring 28 via the end face 42 and additionally presses the latter against the cone, thereby improving the hold of the pipe end 32, see arrow 50 in Figure 2. A leak test is then carried out, and if this confirms the tightness of the connection, the connection is completed.

[0084] If the leak test fails or if there is a risk of leakage for other reasons (e.g. if the pipe end could not be cut to length without causing any crushing), the push-in fitting 1 can optionally be changed from the basic configuration (G) to a post-pressing configuration (NP), whereby the contact pressure of, among others, the O-ring 20 can be increased.

[0085] For this purpose, the union sleeve 22 is moved axially in the direction of the base body 2 using a tool via the threaded connection 4, wherein the sleeve step 24 in the union sleeve 22 presses against the short leg of the L-shape of the spacer sleeve 34 and presses this even deeper into the end section 18 of the base body 2 until the side of the short leg of the L-shape of the spacer sleeve 34 facing the base body 2 strikes the end face 10 of the base body 2.

[0086] This post-injection configuration NP is shown in Figure 3.

[0087] Even if in Figure 3 the union sleeve in the post-pressing configuration almost abuts the base body 2, i.e. a maximum post-pressing is set, an intermediate position between the position in basic configuration G and in the post-pressing configuration NP shown can in principle also be selected for the post-pressing in order to compress the O-ring 20 only as far as necessary, whereby the sleeve geometry ensures that the O-ring 20 is not compressed beyond the permissible extent (for example, a maximum of 20% of its cord thickness).

[0088] In a post-pressing configuration NP achieved in this way, the inner O-ring 20 is more axially compressed, as shown in Figure 3, which is converted into a stronger radial compression due to the elasticity of the O-ring 20.

[0089] At the same time, the reduction in distance between the base body 2 and the union sleeve 22 in the post-pressing configuration NP results in greater contact pressure on the inner conical surface 26 of the union sleeve 22, whereby the retaining ring 28, with its barbs, digs even more firmly into the outside of the pipe end 32, which also leads to an even stronger fixation of the pipe end 32. In the state thus achieved, the distance between the end face 10 of the base body 2 corresponds to the axial length of the axial section of the spacer sleeve 34, which forms the short leg of the L-shape. The stop thus formed limits the possible axial displacement of the spacer sleeve 34 to a maximum travel and thus prevents excessive compression of the O-ring 20, which could otherwise destroy it. Furthermore, this prevents the pipe end 32 from being plastically deformed by the push-in fitting - apart from scoring caused by the barbs of the retaining ring 28.

[0090] The retaining ring 28 may be configured to allow the push-in fitting and the pipe end 32 to be separated from each other again without excessive force, if necessary, when the union sleeve 22 is released again in a disassembly configuration in which the union sleeve is completely unscrewed (not shown).

[0091] Furthermore, Figures 1 to 3 show an elastic element 38 provided on the outside in a groove between the base body 2 and the union sleeve 22. This element 38 can also be an O-ring, but does not primarily serve a sealing function. Instead, it is intended to generate a certain amount of friction as the distance between the base body and the union sleeve 22 decreases when the thread is actuated, in order to prevent accidental loosening or actuation. In the post-pressing configuration NP of Figure 3, the elastic element 38 is accordingly more strongly compressed by the end face 40 of the union sleeve 22 than in the basic configuration according to Figures 1 and 2.

[0092] Figures 4 to 6 show an embodiment of a plug-in fitting 1 according to the invention which is slightly modified compared to Figures 1 to 3, wherein elements with the same function are identified by the same reference numerals.

[0093] Here too, the top figure 4 shows the pre-assembly state in the basic configuration G, the middle figure 5 shows the state after insertion of the pipe end 32, also in the basic configuration, and the bottom figure 6 shows the fitting after it has been brought into the optional post-pressing configuration NP.

[0094] The main difference between the embodiment in Figures 4 and 6 and that according to Figures 1 to 3 lies in a modified spacer sleeve 34a, which does not have a rectangular L-shape, but rather a conical outer cross-sectional enlargement on its end face facing the retaining ring 28. The base body 2 has a corresponding bevel on the inside.

[0095] Figures 7 to 9 show an embodiment of a push-in fitting according to the invention which is similar to Figures 4 to 6, wherein Figure 7 again shows the fitting 1 in the pre-assembly state in the basic configuration G, Figure 8 shows the fitting with the mounted pipe end 32, also in the basic configuration G, and Figure 9 shows the fitting 1 in the post-pressing configuration NP.

[0096] In this embodiment according to Figures 7 to 9, the oversleeve 22 ends in a locking lug (shown exaggerated in dimension), which, in the basic configuration G, engages a corresponding locking recess in the base body 2, thus marking the basic configuration to prevent accidental departure from the basic configuration. By turning the thread, the cap sleeve 22 can be moved into the post-pressing configuration NP despite the locking mechanism, or it can also be disassembled in the other direction; however, the locking mechanism 46 is clearly noticeable in this case.

[0097] The locking lug shown in Figures 7 to 9 engages in a further elongated recess in the base body in the post-pressing configuration NP, so that a certain locking can also be provided in the post-pressing configuration A / P.

[0098] Furthermore, in the embodiment according to Figures 7 to 9, the elastic element 38 is designed such that it can be at least partially covered by the end face of the union sleeve 22 in the post-pressing configuration A / P. If the elastic element 38 is colored, for example, it can be seen at a glance whether a fitting 1 has already been post-pressed or not, and it can be verified that the fitting 1 is actually in the basic configuration G before the pipe end 32 is inserted.

[0099] Figure 10 shows an embodiment of the push-in fitting according to the invention in the post-pressing configuration NP, in which, instead of a single O-ring 20, two consecutive O-rings 20a, b are provided, which are separated by an axially movable separating disk 44, whereby both O-rings 20a, b are additionally axially compressed in the post-pressing configuration. The spacer sleeve 34b is significantly shortened in this embodiment. List of reference symbols

[0100] 1 push-in fitting

[0101] 2 basic bodies

[0102] 4 screw thread connection area

[0103] 5a, b external thread, internal thread

[0104] 6 Connection area

[0105] 8 Outside step, outside groove limitation

[0106] 10 Front face of the base body

[0107] 12 stops

[0108] 14 cylindrical inner surface of the intermediate section

[0109] 16 first interior level

[0110] 18 final section

[0111] 20; 20a, b O-ring, O-rings

[0112] 22 cap sleeve

[0113] 24 sleeve level

[0114] 26 conical inner surface

[0115] 28 slotted retaining ring, retaining element

[0116] 30 conical outer surface

[0117] 32 pipe end to be connected

[0118] 34; 34a, b spacer sleeve

[0119] 36 Front face of the long leg of the spacer sleeve

[0120] 38; 38a outer elastic element (O-ring)

[0121] 40 Front face of the union sleeve

[0122] 42 Front face of the short leg of the spacer sleeve

[0123] 44 cutting disc

[0124] 46 locking step

[0125] 50 arrows

[0126] G Basic configuration

[0127] NP post-injection configuration

Claims

Patent claims 1. A push-in fitting (1) for a sealing connection to at least one pipe end (32) with a smooth exterior, wherein the push-in fitting (1) comprises at least the following: a base body (2) with an approximately cylindrical cavity for the internal reception of the pipe end (32) to be connected, wherein the base body has an internal stop (12) against which the pipe end (32) to be connected abuts in the connected state; a union sleeve (22) which is connected to the base body (1) so as to be adjustable in the axial direction, wherein the push-in fitting (1) can be brought into different configurations by this adjustment, wherein one configuration represents a basic configuration (G) which is already set in the pre-use state and in which the pipe end (32), provided it conforms to predetermined mechanical tolerances, can be sealingly connected and fixed to the push-in fitting (1) by tool-free insertion,and wherein, as a further configuration, a post-pressing configuration (NP) can be set for optional post-pressing to improve the sealing effect, in particular in the case of a pipe end (32) that does not correspond to the mechanical tolerances and cannot be reliably sealed in the basic configuration, and / or a disassembly configuration can be realized in which the union sleeve (22) is removed from the base body (2) without the use of a special tool, so that the pipe end (32) can be removed from the plug-in fitting (1) again without causing any damage if necessary;, wherein the plug-in fitting (1) further comprises a preferably slotted retaining element (28) with radially inwardly directed barbs, which can self-lockingly lock a pipe end (32) to be connected; an inside sealing element (20) which seals the pipe end (32) to be connected on the outside and which, even in the basic configuration (G), can reliably seal pipe ends (32) in the connected state which correspond to the mechanical tolerances, and which, if a post-pressing configuration (NP) is provided, exerts a stronger radial sealing force on the pipe end (32) in this post-pressing configuration (NP) than in the basic configuration (G); and a locking and / or marking element to prevent accidental adjustment from the basic configuration (G).

2. Plug-in fitting (1) according to claim 1, characterized in that The base body (2) and the cap sleeve (22) can be rotated relative to one another by means of a threaded connection (4) or by means of a bayonet-type element and can thus be axially displaced and brought into different configurations.

3. Plug-in fitting (1) according to claim 1 or 2, characterized in that, starting from the stop (12) axially in the direction of the pipe, first the sealing element (20), surrounded by the base body (2), and subsequently the retaining element (28), surrounded by the union sleeve (22), is provided.

4. Push-in fitting (1) according to one of claims 1 to 3, characterized in that the sealing element is designed as at least one O-ring (20) arranged in an inner groove of the push-in fitting, which in the pre-assembled state in the basic configuration (G) projects radially far into the insertion path of the pipe end (32) to be connected and is compressed by the pipe end (32) when inserted in such a way that the pipe end (32) can be easily inserted over the O-ring (20) up to the stop (12) with a simultaneous permanent radial sealing effect for pipe ends (32) corresponding to the mechanical tolerances.

5. Push-in fitting (1) according to claim 4, characterized in that, if a post-pressing configuration (NP) is provided, an axial displacement of the union sleeve (22) from the basic configuration (G) into the post-pressing configuration (NP) causes a reduction in the groove width of the groove for receiving the O-ring (20), whereby the O-ring (20) is axially compressed and the radial sealing forces acting on the outside of the pipe end (32) are thus increased.

6. Push-in fitting (1) according to claim 5, characterized in that the reduction of the groove width in the post-pressing configuration (NP) takes place by means of a spacer sleeve (34) which bears laterally with one end face (36) against the O-ring (20) arranged in the region of the base body (2), and which abuts the union sleeve (22) with its other end face (42), so that an axial movement of the union sleeve (22) relative to the base body (2) is converted into an axial compression of the at least one O-ring (20), wherein the maximum radial compression of the at least one O-ring (20) is mechanically limited preferably to a maximum of 30%, particularly preferably to a maximum of 20% of the cord width of the O-ring (20).

7. Plug-in fitting (1) according to claim 6, characterized in that the spacer sleeve (34) has a cylindrical sleeve shape or a cylindrical sleeve shape with an L-shaped section and a stop collar (42) in the region of the abutment region of the union sleeve (22).

8. Plug-in fitting (1) according to claim 6 or 7, characterized in that the axial compression of the O-ring (20) caused by the radial compression of the O-ring (20) when inserting the pipe end (32) applies an axial prestressing force to the retaining element (25) via the spacer sleeve (34).

9. Plug-in fitting (1) according to one of claims 4 to 8, characterized in that either one O-ring (20) or two O-rings (20a, b) are provided, wherein, if two O-rings are provided, these are separated by an axially movable separating disc (44) so ​​that a radial compression of both O-rings (20a, b) takes place in the post-pressing configuration.

10. Plug-in fitting (1) according to one of claims 1 to 9, characterized in that the preferably slotted retaining element (28) has a cone (30) on the outside, which cooperates with an inside complementary cone (26) of the union sleeve (22) in such a way that the pipe end (32) is locked in a self-locking manner, wherein in the event of an axial displacement of the union sleeve (22) relative to the base body (2) during the subsequent pressing, the retaining element (28) is also compressed more radially. 1 1. Plug-in fitting (1) according to one of claims 1 to 10, characterized in that a detent (46) which can be overcome in the basic configuration (G) and is perceptible during an axial displacement between the elements is provided as a detent and / or marking element between the base body (2) and the union sleeve (22) in order to mark the basic configuration (G) and / or to prevent accidental adjustment from the basic configuration (G).

12. Plug-in fitting (1) according to one of claims 1 to 11, characterized in that an annular elastic element (38) is provided in an external groove (8) between the base body (2) and the union sleeve (22) to achieve an surmountable frictional connection between the base body (2) and the union sleeve (22).

13. Push-in fitting (1) according to claim 12, characterized in that the annular elastic element (38) is visible in the basic configuration (G) and is completely or partially covered by a projection in a post-pressing configuration (NP), thereby marking whether the push-in fitting (1) is in the basic configuration (G) or in a post-pressing configuration (NP).

14. A method for sealingly connecting a pipe end (32) to a push-in fitting (1), wherein the push-in fitting (1) can optionally be brought into a post-pressing configuration (NP) which allows an increase in the contact forces of the sealing elements (20) of the push-in fitting (1) compared to a basic configuration (G) in which a permanently sealed connection can already be produced with pipe ends (32) corresponding to the mechanical tolerances, in particular a method for connecting a pipe end (32) to a push-in fitting (1) according to one of the preceding claims, characterized by the steps: a) tool-free insertion of the pipe end (32) to be connected into the push-in fitting (1) in the basic configuration (G), whereby a permanently tight connection is already established with pipe ends (32) corresponding to the mechanical tolerances, and b) if after step a) - immediately or at a longer time interval - a leak is detected or predicted; bringing the push-in fitting (1) into the post-pressing configuration (NP) to achieve and / or ensure permanent tightness.

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