Patent Publication Number: US-2023160410-A1

Title: Telescopic system

Description:
FIELD 
     The invention concerns a telescopic system having at least two profile rails which are linearly guided against each other in the longitudinal direction and which are moveable relative to each other over a distance and which each have a longitudinal profile having longitudinal grooves and/or longitudinal ribs, wherein provided at each profile rail is at least one sliding element, by way of which the at least two profile rails bear slidingly displaceable against each other and which is arranged axially fixedly at least with respect to the longitudinal direction on the longitudinal profile of the profile rails associated therewith. 
     BACKGROUND 
     A telescopic system of the general kind set forth is disclosed in DE 10 2016 103 566 A1. The telescopic system has two hollow profiles which are guided one within the other and between which a respective sliding element is injected directly into an intermediate space between the hollow profiles by means of an injection molding lance in situ at certain locations, wherein the sliding element for a better holding action engages with a base into an internal groove in the radially outer hollow profile or an outer groove in the radially inner hollow profile. That is elaborate in terms process technology and complicated in respect of assembly. In addition the sliding element can become loose in use, can be displaced longitudinally in the groove or can even become detached therefrom. 
     A further telescopic system having two hollow profiles which are guided within each other and which are supported against each other by way of hollow-cylindrical sliding elements is known from DE 10 2004 010 503 A1. The sliding elements are respectively secured against axial displacement by transverse bolts engaging into transverse bores. Accordingly structural modifications in the profile rails are required with the transverse bores for fixing the sliding element. 
     The catalog “dry-tech Lagertechnik” from the applicant, dating from 2015, page 840, presents a telescopic system in which the sliding element is of a rail-like configuration and is slidingly displaceably mounted between the two and at the two profile rails. As the sliding element is telescopic it is correspondingly heavily flexurally loaded when fully extended. Such a telescopic system is therefore not suitable for heavier loads to be carried. 
     SUMMARY 
     An object of the present invention is to provide a telescopic system of the general kind set forth, which is of a simple structure and easier to assemble. In addition the invention seeks to provide that the sliding element is non-displaceably held to the respectively associated profile rail. Furthermore the invention seeks to provide that no structural modification to the profile rails is required for fixing the sliding element. In addition the aim of the invention is to provide that the telescopic system is suitable for carrying greater load moments. 
     The object of the invention is already attained in that the sliding elements is connected to a clamping element in displaceably fixed relationship on the profile rail at least with respect to a sliding plane defined by the longitudinal direction and a first transverse direction perpendicularly to the longitudinal direction, wherein the clamping element is arranged with a clamping fit on the longitudinal profile of the profile rail, more specifically in or at a longitudinal groove and/or on a longitudinal rib. 
     The clamping fit of the clamping element on the longitudinal profile does not require any further precautions or structural modifications to the profile rails. That simplifies construction and assembly of the telescopic system. By virtue of the clamping fit by way of a clamping element on the longitudinal profile the sliding element can be held non-displaceably to the respectively associated profile rail. As at least one clamping element is associated with each profile rail the at least two profile rails in the installed position are arranged guided slidably on each other at the at least two sliding elements. 
     In the present invention the profile rails alone form the telescopic members. A change in length achieved by the telescopic system is effected solely by way of the profile rails. Therefore the telescopic system can also be designed for greater load moments. No further processing of the respective profile rail is necessary for inserting the sliding elements into or fixing them in the telescopic system and/or for axially non-displaceably fixing the sliding element to the respective profile rail. For example no bores have to be provided for receiving the sliding element, into which or to which the sliding elements are fitted or screwed. Therefore the profile rail can be cut to a given length from a profile section and installed in the telescopic system without further precautionary measures. 
     In the installed position the profile rails can be arranged to bear slidingly displaceably against each other solely by way of the at least two sliding elements. In particular one of the at least two sliding elements can be axially non-displaceably fixed to the one of the at least two profile rails and the other of the at least two sliding elements can be axially non-displaceably connected to the other of the at least two profile rails. The two profile rails can be arranged to engage into each other by way of a groove-and-tongue connection. In the tongue-and-groove connection the longitudinal grooves can form the groove and the longitudinal projections can form the tongue. Likewise the profile rails can be arranged to engage into each other by way of the associated sliding elements in the form of the tongue-and-groove connection. The longitudinal grooves of the longitudinal profile can form the groove and the longitudinal ribs of the longitudinal profile can form the tongue. That association of longitudinal grooves and longitudinal ribs in the tongue-and-groove connection implies that the two profile rails can have longitudinal profiles which are admittedly different but adapted to each other. 
     Preferably the profile rails are made from metal, in particular an aluminum alloy, in particular a high-strength aluminum alloy. That choice of material makes it possible to carry and transmit relatively large loads. The profile member is preferably extruded but can also be injection molded. In that case the profile member can have the complete longitudinal profile which is intended for forming the telescopic system with at least two profile rails respectively cut to length on a profile member. 
     Desirably in terms of force mechanics the sliding element arranged non-displaceably on the profile rail can be arranged to be supported with respect to the longitudinal direction over its entire axial length on that profile rail. The sliding element can be arranged to be held fixedly in the telescopic system in the installed position with respect to that profile rail without any degree of freedom. The clamping fit permits a play-free arrangement of the sliding element on the profile rail. 
     In the installed position the longitudinal groove and/or longitudinal rib can be designed to be open laterally towards the respective sliding connection partner or can be arranged to extend thereto. The longitudinal groove can be opened laterally perpendicularly or approximately perpendicularly to the sliding plane. In a corresponding fashion the longitudinal rib can extend with its free end region perpendicularly or approximately perpendicularly to the sliding plane. The direction perpendicular or approximately perpendicular to the sliding plane defines a second transverse direction. That can be perpendicular or approximately perpendicular to the first transverse direction and to the longitudinal direction. The longitudinal groove can be laterally delimited by two longitudinal ribs or by a longitudinal rib and an inside wall. The longitudinal rib can also be referred to as a longitudinal projection of the longitudinal profile. To save weight the longitudinal rib can be in the form of a hollow rib. 
     The clamping element can engage into or on the longitudinal groove perpendicularly to the sliding plane laterally or axially with respect to the longitudinal direction into the longitudinal groove. The clamping element can be introduced into the longitudinal groove in the longitudinal direction or perpendicularly thereto in lateral relationship. Similarly the clamping element can be fitted over the longitudinal projection perpendicularly to the sliding plane or can be axially pushed into place thereon with respect to the longitudinal direction. 
     As usual the profile rails which are mounted slidingly displaceably against each other can be arranged in the telescopic system in spaced relationship by way of the sliding element, thereby forming a sliding gap. Because of advantageously smaller structural heights the sliding gap can be equal or approximately equal to an average wall thickness of the sliding element. The magnitude of the spacing can be defined by the geometry, in particular by the wall thickness, of the sliding element. 
     In a development of the telescopic system the sliding element and the clamping element can be arranged fixed to each other in positively locking relationship and/or force-locking relationship at least with respect to the longitudinal direction or the sliding plane. The sliding element and the clamping element can bear against each other remaining loose in positively locking relationship. The sliding element can be arranged to be clamped between two clamping elements, thereby providing a force-locking relationship, wherein the two clamping elements are each arranged in the clamping fit on the longitudinal profile. Advantageously by virtue of a firmer connection it can be provided that the sliding element and the clamping element latch to each other, preferably with the formation of a spring force. For latching purposes it is possible to provide on the sliding element and the clamping elements mutually adapted usual latching means like a dome-like raised portion which engages into a correspondingly trough-like recess, or also an undercut configuration into which a suitably matched projection engages. In particular the sliding element and the clamping element can be connected together by way of a positively locking connection. Desirably in terms of construction and assembly the sliding element can be arranged to engage axially over the clamping element with respect to the longitudinal direction and can be arranged to bear against the clamping element axially at both ends of the clamping element. The sliding element can be arranged to be non-displaceable and non-rotatable perpendicularly to the first transverse direction or perpendicularly to a second transverse direction perpendicular to the first transverse direction, and can be held non-rotatable with respect to the longitudinal direction. Both transverse directions can be oriented perpendicularly or at least approximately perpendicularly to the longitudinal direction. In the installed position in the telescopic system forces and force moments in or in relation to all directions can be carried by the sliding element. 
     The clamping element can be of an elongate shape. It can be of a cylindrical, part-cylindrical, semi-cylindrical, prismatic, ellipsoidal, lens-like or ball-like shape. The clamping element can also be in the form of a bolt, pin or ball. The clamping element may have a surface structure like increased roughness or peripheral ribs to increase friction. The clamping element can have radially outwardly peripheral surface structures similar to those of a grooved, screw or notched nail. In particular bolts or pins can have a male thread which preferably extends over the entire axial length of the bolt or pin. The bolt or pin can be of a conically tapering configuration at least at one of its two end regions for easier introduction into and clamping fast in the longitudinal groove. Similarly the ball in the installed position can taper in the longitudinal direction by for example being of an ellipsoidal configuration. 
     The sliding element can advantageously be simply coupled, in particular connected, by way of a push-in connection or a plurality thereof, in particular on the basis of the tongue-and-groove principle, to the longitudinal profile of the respectively associated profile rail. In a development of the telescopic system the sliding element can be in the form of a profile part with a longitudinal profile extending in the longitudinal direction in the installed position. Similarly to the profile rails the longitudinal profile can have longitudinal grooves and/or in particular rib-like longitudinal projections for engagement into an associated longitudinal groove of an associated profile rail. 
     For clamping the sliding element to an associated profile rail the clamping element can be arranged in the associated longitudinal groove with a clamping fit therein. For its axially non-displaceable connection at least in respect of the longitudinal direction to the one profile rail associated therewith, the sliding element can engage into the longitudinal groove of said one profile rail, that has the clamping element, and/or into the longitudinal groove of the other profile rail, that has the clamping element. The sliding element can have at least one rib-like longitudinal projection having a receiving recess. In the installed position the rib-like longitudinal projection can engage into the longitudinal groove associated therewith with the clamping element with the clamping element being received in the receiving recess. Conversely the profile rail can also have a longitudinal rib which engages into a longitudinal groove on the sliding element, wherein the clamping element is arranged at the longitudinal rib, for example with lateral clamping embracing thereof. The clamping element can be received in the receiving groove with resilient expansion thereof. The sliding element can thus be held to the clamping element in force-locking relationship in addition to the positively locking relationship. 
     The engagement of the clamping element into the receiving recess can be effected in positively locking relationship at least with respect to the longitudinal direction. The receiving recess can be in the form of an interruption, gap or incision in the rib-like longitudinal projection. The receiving recess can be adapted in respect of the longitudinal direction to the axial length of the clamping element. In the installed position the rib-like longitudinal projection of the sliding element can extend with its free end region in the second transverse direction. In the installed position the longitudinal directions of the profile rail, the sliding element and the clamping element can be the same. 
     The sliding element can be of a flat basic shape with a base parallel to the sliding plane, wherein at least the one rib-like longitudinal projection and/or a rib-like further projection can extend as a prolongation of the base in the first transverse direction from one side of the base perpendicularly to the sliding plane. In the installed position the base can be arranged to extend parallel to the sliding plane. In the flat basic shape the height of the sliding element, that extends in the second transverse direction in the installed position, can be substantially less, for example three to ten times less, than the extent of the sliding element in the first transverse direction. The sliding element can be arranged in positively locking relationship in an additional longitudinal groove in the one profile rail, which groove is open laterally in the second transverse direction. The sliding element can lie with its base in flat surface relationship on the bottom of the additional longitudinal groove. In addition it can be supported in the additional longitudinal groove at both sides with respect to the first transverse direction. The two longitudinal projections can extend away from the groove bottom in the direction of the lateral opening of the additional longitudinal groove. 
     The wall thickness of the sliding element can be the same or at least approximately the same in all of its regions. Amongst other things a gap dimension of a gap can be set by way of the wall thickness of the base, by way of which gap the profile rails are held spaced from each other perpendicularly to the sliding plane. The at least one rib-like longitudinal projection and the rib-like further projection of the sliding element can be arranged spaced from each other with respect to the first transverse direction. 
     In a further embodiment of the telescopic system the sliding element can have two rib-like longitudinal projections. One of the two longitudinal projections can be coupled to the longitudinal profile of the profile rail, to which the sliding element is fixed in the installed position. The other of the two longitudinal projections can be coupled to the longitudinal profile of the profile rail which bears slidably against the sliding element in the installed position. 
     The two longitudinal projections can be arranged to extend away from the same side of the base in a common direction perpendicularly or approximately perpendicularly to the sliding plane. The two longitudinal projections can be arranged completely at that side. One of the two longitudinal projections can extend in that common direction. That longitudinal projection which is referred to as the first longitudinal projection can extend with its free end region in that common direction. In addition a longitudinal projection referred to as the second longitudinal projection can be of a hook-like curved configuration. In particular the second longitudinal projection can be bent over in a hook-shaped configuration about an axis of curvature parallel to the longitudinal direction at its free end region, thereby forming a receiving groove for a longitudinal rib of an associated profile rail. The receiving groove can be laterally open in the opposite direction to the common direction. The second longitudinal projection can extend with the free end region of the hook-like shape in the opposite direction to that common direction towards the side. Preferably the free end of the hook-like shape remains spaced in relation to the side of the base, from which the second longitudinal projection extends. The second longitudinal projection can be curved in a hook-shaped configuration about an axis of curvature parallel to the longitudinal direction to less than 90%, preferably less than or equal to 60% of its extent in the longitudinal direction. The two longitudinal projections can each have a receiving means for the clamping element, which is desirable in regard to universal positioning of the sliding element in the telescopic system. Preferably associated with each longitudinal projection of the sliding element is a longitudinal groove in the longitudinal profile of the associated profile rail. 
     All sliding elements used in the telescopic system can be of the same structure. In addition they can be in one piece. The axial extent of the sliding element, with respect to the longitudinal axis, can be less than or equal to 40%, less than or equal to 20% or less than or equal to 5% of the corresponding axial length of the associated profile rail. 
     The rib-like further projection of the sliding element can have a free end region which defines a further receiving groove which is open laterally in the first transverse direction for a receiving rib of an associated profile rail. The receiving groove can be defined by the hook-like curvature of the free end region. The free end region of the rib-like further projection of the sliding element can be bent over hook-like parallel to the longitudinal direction. The rib-like further longitudinal projection can be curved in a hook configuration over up to less than 90%, preferably less than 60% of its extent perpendicularly to the longitudinal direction. A corresponding axis of curvature can be oriented parallel to the longitudinal direction. The rib may also be a longitudinal rib defining a longitudinal groove. 
     The rib-like further projection can engage into a further longitudinal groove in an associated profile rail in the first or approximately in the first transverse direction. The further longitudinal groove can advantageously be arranged outwardly with respect to the first transverse direction. The further longitudinal groove can be laterally open towards the center with respect to the first transverse direction. Advantageously, the profiles of the further longitudinal groove and the further longitudinal projection can be of a mutually matching configuration. 
     The further rib-like longitudinal projection can be designed to be resilient, primarily perpendicularly to the sliding plane. In particular the rib-like further longitudinal projection can be of a leaf spring-like configuration. To be able to move the sliding element with its receiving means relative to the sliding plane over the clamping element associated therewith the sliding element, in a first step, can be introduced with its resilient further longitudinal projection into the further longitudinal groove of the associated profile rail, with angular positioning relative to the sliding plane at the end thereof. The sliding element can then be displaced axially in the further longitudinal groove until the receiving means is arranged aligned with the clamping element with respect to the second transverse direction. In a further step the sliding element can be pivoted over its further longitudinal projection that projects into the further longitudinal groove, with the clamping element being simultaneously received in its receiving means, towards the sliding plane. In that situation latching of the sliding element to the clamping element can additionally be effected. 
     To secure the profile rails to prevent relative movement perpendicularly to the sliding plane it can be provided that the other profile rail as a sliding partner in relation to the one profile rail engages with a receiving projection into the receiving groove thereof. The receiving groove of the one profile rail, the receiving projection of the other profile rail and the further projection of the sliding element can be dimensioned in mutually matching relationship such that in particular they bear against each other over sliding guide surfaces facing in the second transverse direction, preferably without play or approximately without play. By virtue of the engagement of the receiving projection of the other profile rail by way of the longitudinal groove in the sliding element into the receiving groove of the one profile rail the longitudinal groove can be urged with at least parts of its wall at the inside against the wall of the receiving groove. The two profile rails can bear against each other slidingly displaceably, in particular without play or almost without play, by way of the sliding elements in sliding guide surfaces described in greater detail hereinafter. The components profile rail and sliding element can slide against each other at the sliding guide surfaces, with simultaneous guidance thereof. Associated with each sliding guide surface of the sliding element there can be a corresponding sliding guide surface of one of the at least two profile rails. 
     In addition the receiving groove can have an undercut configuration which is operative preferably in the first transverse direction and in particular radially inwardly with respect to the longitudinal direction. The further projection which is adapted to the receiving groove can be arranged to be held against a possible relative movement in the first transverse direction in positively locking relationship at the undercut configuration in the receiving groove. By virtue of those measures the two sliding partners and the sliding element which embraces the receiving projection can be at least stabilized in position in relation to a relative movement in the first transverse direction. In particular they can bear against each other without play or almost without play with respect to the first transverse direction. 
     The at least one rib-like longitudinal projection or the two rib-like longitudinal projections can be arranged spaced from the rib-like further projection of the sliding element with respect to the first transverse direction. The sliding element can thus have two axially separate regions in relation to the first transverse direction and/or the longitudinal direction. The one longitudinal projection or the two longitudinal projections can be arranged in an axially inward region. They can have first sliding guide surfaces perpendicular to the first transverse direction. Arranged axially at the edge in the other of the two axial regions the further longitudinal projection can have the above-mentioned second sliding guide surfaces which are parallel to the sliding plane. Amongst other things those structural measures mean that all sliding elements can be of the same structural configuration. 
     The sliding element can be made from plastic, in particular friction-reducing, also wear-resistant plastic. In particular it is possible to use a tribopolymer as the material for the sliding element. By virtue of solid lubricants which are incorporated into the compound it is possible to provide for lubricant-free dry running which is also suitable for use for example in foodstuff sectors. In addition it is possible to achieve a relative movement of the profile rails, involving a low noise level. The sliding element can be produced by injection molding. It can also be inexpensively cut to length from a profile member which is prefabricated for example by extrusion or injection molding. The sliding element thus permits a sliding bearing configuration for the two profile rails which are displaceable relative to each other. The sliding bearing configuration is corrosion-resistant as well as maintenance-free and lubricant-free by virtue of the material pairing. 
     In particular at least some of the sliding guide surfaces can be cooperating at least in pair-wise relationship or at least in threes. The sliding guide surfaces of each sliding guide surface pair or triple can be arranged parallel to each other and facing towards or away from each other. In particular some sliding guide surfaces which are in the form of first sliding guide surfaces can be provided perpendicularly to the first transverse direction or some sliding guide surfaces in the form of second sliding guide surfaces can be perpendicular to the second transverse direction. At least one longitudinal projection of the sliding element can have first sliding guide surfaces, in particular all first sliding guide surfaces provided on the sliding element, which is simple in terms of construction and assembly. In addition the further longitudinal projection and the base of the sliding element can have second sliding guide surfaces, in particular all second sliding guide surfaces provided on the sliding element. The first sliding guide surfaces can be arranged spaced relative to the second sliding guide surfaces, with respect to the first transverse direction. 
     For assembly it is proposed that the profile rails be pushed into each other at the ends in the longitudinal direction. Because of the sliding element which is already pre-fitted and the advantageously tighter guidance of the profile rails in each other, which is play-free or almost play-free, the profile rails in practice have to be “threaded” into each other. 
     An insertion aid can be provided for the assembly of two profile rails which are each provided with the desired number of sliding elements, to form a play-free or almost play-free assembly of the profile rails. The insertion aid can include one or more measures to facilitate the respective phase of assembly in which the profile rails are pushed into each other in the longitudinal direction at the ends, provided with the sliding elements. A measure which has already been described hereinbefore for that purpose can be that the first sliding guide surfaces are arranged spaced relative to the second sliding guide surfaces, with respect to the first transverse direction. A further measure can provide that the narrow end of the wall with the sliding guide surfaces is arranged spaced perpendicularly to the first transverse direction with respect to the longitudinal direction or displaced relative to the narrow end of the wall with the sliding guide surfaces perpendicularly to the second transverse direction. That displacement can be provided in and/or in opposite relationship to the longitudinal direction. The narrow ends of the sliding guide surfaces, that face in the longitudinal direction, can reach the end of the profile rail which is to be displaced over the sliding element, in displaced relationship corresponding to the axial displacement of the ends thereof. Interengagement of two profile rails as sliding partners can be effected with successive orientation at the various sliding guide surfaces like for example the sliding guide surfaces perpendicularly to the second transverse direction and then the sliding guide surfaces perpendicularly to the first transverse direction. As a further measure it can be provided that the ends of the sliding guide surfaces, that face in the longitudinal direction, are each preferably beveled at both sides. They can have inclined insertion surfaces which respectively act as an inclined plane. That beveling can be provided on both ends of the sliding elements, that face in the longitudinal direction. The above-described measures permit universal use of the sliding elements in the telescopic system. As a result the sliding elements of the telescopic system can also be of an identical structure. 
     The at least two sliding elements arranged between the at least two profile rails can be arranged in collinear and axially mutually spaced relationship with respect to the longitudinal direction. The two sliding elements can be positioned on a central axis extending in the longitudinal direction. The two sliding elements can be arranged centrally in the telescopic system with respect to the first transverse direction. 
     There can also be three sliding elements between the two profile rails. Advantageously in terms of force mechanics, they can be arranged at the corner points of an isosceles triangle with respect to the sliding plane. In an advantageous development of the telescopic system there can be four sliding elements, by way of which the two profile rails bear slidingly displaceably against each other. The sliding elements can be arranged and/or oriented in mirror-image symmetrical relationship with each other with respect to a central first plane of mirror-image symmetry perpendicularly to the first transverse direction. Correspondingly at least the parts of the longitudinal profiles of both profile rails, with which the sliding elements are coupled, can be of a mirror-image symmetrical configuration with respect to that first plane of mirror-image symmetry. The sliding elements can be combined together to form two sliding element pairs each having two sliding elements. The two sliding element pairs can be arranged spaced from each other with respect to the longitudinal direction. In particular the sliding elements of preferably each sliding element pair can be arranged at the same level with respect to the longitudinal direction. Desirably the one sliding element pair of the at least two sliding element pairs can be axially non-displaceably connected to the one of the at least two profile rails and the other sliding element pair of the at least two pairs can be axially non-displaceably connected to the other of the at least two profile rails. Particularly when greater widths in the first transverse direction of the profile rail are involved sliding element triples can be provided for improved support thereof at the sliding elements. 
     The longitudinal grooves for receiving the clamping element of the one profile rail can be arranged axially spaced with respect to the first transverse direction in relation to the longitudinal grooves for receiving the clamping element of the other profile rail. In the installed position the longitudinal grooves of the one profile rail can be arranged axially inwardly with respect to the first transverse direction, in relation to the longitudinal grooves of the other profile rail. 
     In particular the sliding elements can be respectively arranged in an end region of the respectively associated profile rail in relation to the longitudinal direction. They can also terminate flush at their ends with the respectively associated end of the profile rail. The bases of the sliding elements disposed between the two profile rails can be arranged in a common plane parallel to the sliding plane. 
     The telescopic system according to the invention can thus be produced and assembled very easily. To produce a telescopic system with for example two profile rails they can be provided by each being cut to length from a profile member. In that case, as described above, the longitudinal profiles of the two profile members are so adapted to each other that in the installed position they engage into each other in a tongue-and-groove connection. Furthermore it is possible to provide at least two sliding elements which can be cut to length from a single profile member. The at least two sliding elements can thus be of the same structure and in one piece. Furthermore at least one clamping element can be provided per sliding element. The clamping elements can be cut to length from an elongate portion. The clamping elements can be of the same structure and in one piece. 
     In a first assembly step one of the two sliding elements can be fixed to a profile rail and the other sliding element can be fixed to the other profile rail each at least axially non-displaceably with respect to the longitudinal direction. For that purpose in a first sub-step one of the clamping elements can be introduced into the longitudinal groove associated therewith in one of the two profile rails and the other clamping element can be introduced into the longitudinal groove associated therewith in the other of the two profile rails, in each case in a clamping fit. In a further sub-step the two sliding elements can be moved over the respective clamping element associated therewith. For that purpose, they can each be pushed into the further longitudinal groove with their further longitudinal projection pivotably about a pivot axis parallel to the longitudinal direction until they are each moved axially with their receiving means over the associated clamping element, with respect to the longitudinal direction. The sliding element can then be lowered over the clamping element with a pivotal movement and in that case receive the clamping element in the receiving opening. The sliding element can thus be arranged slidingly displaceably for assembly thereof with its further longitudinal projection in the longitudinal direction and pivotably about a pivot axis parallel to the longitudinal direction in the further longitudinal groove. 
     In a further assembly step the two profile rails respectively provided with at least one sliding element can be pushed into each other at the ends so that they bear against each other by way of the at least two sliding elements. 
     In a development of the telescopic system an abutment device can be provided to limit the linear travel. That can have at least two end abutments. The end abutments can form the above-described sliding elements. Additional end abutments are viewed as being mechanically more stable. They can be arranged in a further longitudinal groove of the respective profile rail. In addition there can be a abutment element cooperating with the end abutments. The abutment element can be arranged slidingly displaceably or fixed in position in the further longitudinal groove of the other profile rail. The abutment element can be held axially non-slidably in the further groove associated therewith by means of a clamping element. In both cases the clamping element can be held in a clamping fit in the associated further longitudinal groove. In addition the travel can be set by way of the longitudinal extent of the abutment element. Advantageously in terms of construction and assembly the clamping element can be exactly identical to the clamping element described hereinbefore and hereinafter, which is used for non-displaceable mounting of the sliding element. That means that the end abutments can be heavily loaded. 
     The abutment groove can have at least one buffer element arranged between the abutment element and one of the two end abutments and at least one buffer element arranged between the abutment element and the other end abutment. The buffer elements can be guided freely displaceably in the abutment groove and/or can be fixed at the ends to the abutment element. The provision of the buffer elements can increase the service life of the end abutments and/or the abutment element. The abutment element can engage latchingly into the further abutment groove. It can have at least one guide groove which extends in the longitudinal direction and into which the abutment element engages with a longitudinal projection adapted to the guide groove. 
     For final assembly in a first sub-step firstly only one end abutment can preferably be positioned at the desired location and the for example two profile rails, as described above, can be pushed at the ends into an assembly device. In a further sub-step the second end abutment can also be moved in the assembly direction in a clamping fit into the further longitudinal groove. A single abutment device can be provided for each two profile rails which are mounted slidingly displaceably against each other. It can be arranged at the edge on the profile rails in relation to the longitudinal direction. 
     Usually the profile member for producing a profile rail can be provided at the factory with openings equally spaced in the longitudinal direction for fixing the profile rails which have been cut to length from the profile member to components or the like. In that case the spacings and number of the openings can be so selected that each profile rail cut to length from the profile member has at least two openings. 
     A further embodiment of the telescopic system can have three profile rails which are mounted to each other linearly displaceably relative to each other, two outer profile rails and a central profile rail mounted relatively displaceably between the two outer profile rails. They can be arranged slidably against each other in the longitudinal direction relative to each other in the longitudinal direction and parallel to the sliding plane. The central profile rail can thus be connected towards both sides to a respective one of the outer profile rails slidably displaceably in the longitudinal direction. For that purpose the central profile rail can have a longitudinal profile, by way of which it can be mechanically coupled towards both outer profile rails with the respective outer profile rail. 
     By virtue of the tongue-and-groove connection provided between the profile rails their longitudinal profiles differ from each other. To provide the sliding displaceable connection two respective longitudinal profiles of differing configuration can be connected together. In that case the two outer profile rails each have an identical longitudinal profile while the central profile rail has a longitudinal profile which is adapted at both sides in relation to the second transverse direction to that of the outer profile rails and in particular of the same structure. The two outer profile rails can be of the same structural configuration. 
     The central profile rail may have an identical profile at each of its sides towards the two outer profile rails. The central profile rail can be of a mirror-image symmetrical structure with respect to the central first plane of mirror-image symmetry perpendicularly to the first transverse direction and with respect to a central second plane of mirror-image symmetry perpendicularly to the second transverse direction. It can have a transverse bar arranged parallel to the sliding plane, with guide grooves at both ends with respect to the transverse direction. The arrangement and configuration of the guide grooves can be the same at both ends of the transverse bar. 
     As a continuation in the possible options for enlargement of the telescopic system it can have for example six profile rails of which the two outer profile rails can also be of the same profile which extends from one side substantially in the second transverse direction. The remaining four profile rails between the two outer ones can each be of the same longitudinal profile at both sides. Profile rails which in the installed position are adjacent to each other with respect to the second transverse direction can each involve different longitudinal profiles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In advantageous embodiments the telescopic system has one or more of the above-indicated features, more specifically in any combination. Further details and advantages of the invention will be apparent hereinafter, without restriction on the scope of protection, from the description of preferred embodiments with reference to the accompanying drawings. All terminology for describing location like up, down, front, back, right and left are intended as they are shown in the respective Figure itself, unless it is specifically defined otherwise. In the drawings: 
         FIGS.  1 A- 1 D  each show a view of an embodiment of a telescopic system with three profile rails as telescopic members, more specifically in an extended position, 
         FIGS.  2 A- 2 D  each show a view of the embodiment of the telescopic system of  FIGS.  1 A- 1 D  but in a retracted position, 
         FIGS.  3 A- 3 C,  4 A- 4 B and  5 A- 5 B  show views with side views and sectional views relating to the assembly of two profile rails with sliding elements in three steps, 
         FIGS.  6 A- 6 C  show a side view and sectional views of the sliding element, 
         FIG.  7    shows a side view of a further embodiment of the telescopic system with two telescopic rails, 
         FIG.  8    shows a side view of a further embodiment of the telescopic system with five telescopic rails, 
         FIGS.  9 A- 9 C  each show a view of the embodiment of the telescopic system of  FIGS.  1 A- 1 D  in the extended position but with an abutment device, and 
         FIGS.  10 A- 10 C  each show a view of the embodiment of the telescopic system of  FIGS.  9 A- 9 D  but in the retracted position. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  through  5  and  7  through  10    show various views and sectional views of different embodiments of a telescopic system  1 . The telescopic system  1  has at least two profile rails  2  which are guided linearly against each other in a longitudinal direction  1  and which are moveable relative to each other over a travel distance w shown in  FIG.  5 A . The profile rails  2  are each provided with a longitudinal profile  21  having longitudinal grooves  22  and longitudinal ribs  23 . As shown in  FIGS.  7  and  8    the telescopic system  1  has two and five respectively relatively mutually moveable profile rails  2 . In the other views showing the telescopic system  1  there are three profile rails  2 , two outer first profile rails  2   a,  each here of a C-shaped profile, and a central second profile rail  2   b  arranged between the two outer first profile rails  2   a.    
     In this arrangement provided between each two profile rails  2  which are guided linearly against each other are four sliding elements  3 , by way of which those two profile rails  2  bear against each other slidingly displaceably.  FIGS.  6 A- 6 C  each show an individual view of a sliding element  3 . The sliding element  3  is in the form of a profile portion with a longitudinal profile  32  extending in the longitudinal direction l in the installed position. The sliding elements  3  shown in the various embodiments of the telescopic system  1  are of the same construction and are in one piece. In addition they are cut to length from a plastic profile member (not shown) comprising a tribopolymer with solid lubricants incorporated in the compound, for lubricant-free dry running. The profile rails  2  are each cut to length from a profile member (not shown here) of an aluminum material. By virtue of the tongue-and-groove connection the profile rails  2  which are coupled as sliding partners are each of another longitudinal profile  21 . 
     The sliding elements  3  are respectively connected non-displaceably to a clamping element  4  at the associated profile rail  2  with respect to a sliding plane G defined by the longitudinal direction l and a first transverse direction q 1  perpendicular to the longitudinal direction l. The clamping element  4  is arranged in a clamping fit here in a longitudinal groove  22  in the longitudinal profile  21  of that profile rail  2 . By virtue of the clamping fit of the clamping element  4  the sliding element  3  can be held non-displaceably to the respectively associated profile rail  2 . All sliding elements  3  are respectively connected by way of a clamping element  4  to the respectively associated profile rail  2 . By virtue of that measure the profile rails  2  remain unchanged in their configuration in each case in spite of the fixing of the sliding elements  3  to the longitudinal profile  21 . 
     In the embodiment shown here of the telescopic system  1  the sliding elements  3  are arranged in pairs between the at least two profile rails  2 . The sliding elements  3  of the one sliding element pair  31  are axially non-displaceably connected to the one of the at least two profile rails  2  and those of the other sliding element pair  31  are axially non-displaceably connected to the other of the at least two profile rails  2 . To have a travel distance w which is as great as possible the sliding elements  3  are respectively arranged in an end region with respect to the longitudinal direction l, here even at the ends, in flush relationship with the profile rail  2  associated therewith. In addition the sliding elements  3  are arranged to be supported at that profile rail  2  in each case over their entire axial length in relation to the longitudinal direction l. Both measures can be seen by way of example in  FIGS.  1 B,  1 C and  2 B . In addition the sliding elements  3  of the sliding element pair  31  are arranged and oriented in mirror-image symmetrical relationship perpendicularly to the first transverse direction q 1 , in relation to a first plane of mirror-image symmetry S 1 . Correspondingly the parts of the longitudinal profiles of both profile rails with which the sliding elements are coupled are of a mirror-image symmetrical configuration in relation to that first plane of mirror-image symmetry. 
     The sliding element  3  and the clamping element  4  are also fixed to each other in positively locking relationship in relation to the longitudinal direction l and in addition the sliding plane G. As can be seen for example from  FIGS.  4 A through  4 C  the clamping element  4  here is in the form of a threaded pin of a circular-cylindrical basic shape. The sliding element  3  has a longitudinal profile  32  extending in the longitudinal direction l in the installed position, here with two rib-like longitudinal projections  33 , each with a receiving recess  331 . In the case of fixing the sliding element  3  to an associated profile rail  2  the sliding element  3  engages with one of its longitudinal projections  33  and more specifically with its receiving recess  331  over the clamping element  4  arranged with a clamping fit in the longitudinal groove  22 . The clamping element  4  is disposed here with simultaneous latching axially at both ends in positively locking relationship and is thus non-displaceable in the receiving recess  331  on the sliding element  3 . 
     The sliding element  3  here has two rib-like longitudinal projections  33  each with a receiving recess  331 . Both rib-like longitudinal projections  33  engage into an associated longitudinal groove  22  of the longitudinal profile  21  of the profile rails  2 . In this case the associated clamping element  4  is arranged with a clamping fit in the longitudinal groove  22  of the one profile rail  2 , to which the sliding element  3  is fixed. In the installed position the clamping element  3  is arranged non-displaceably with respect to the longitudinal direction l in the receiving recess  331  by way of the clamping element  4 . The other of the two longitudinal projections  33  engages only slidingly displaceably in the associated longitudinal groove  22  of the other profile rail  2 . 
     The longitudinal grooves  22  in the profile rails  2 , that are associated with the longitudinal projections  33  of the sliding element  3 , are laterally open in the second transverse direction q 2 . Correspondingly in the installed position the rib-like longitudinal projection  33  extends with its free end region  331  in the second transverse direction q 2 . As can be seen for example from  FIG.  4 C  the receiving recess  331  is in the form of an incision  332 , here of a right-angled longitudinal profile. 
     The sliding element  3  is of a basic shape which is flat with respect to the second transverse direction q 2 . The sliding element  3  has a base  34 . In the installed position it is arranged here parallel to the sliding plane G. The bases  34  of all sliding elements  3  used in the telescopic system  1  extend here parallel to the sliding plane G. The bases of the sliding elements  3  which are arranged between two profile rails  2  coupled slidingly displaceably by way of said sliding elements  3  extend in the same plane parallel to the sliding plane G. The sliding elements of two profile rails  2  which are slidingly displaceably coupled together by way of those sliding elements are arranged and oriented in mirror-image symmetrical relationship in relation to a first plane of mirror-image symmetry S 1 . 
       FIG.  7    shows an end view of a telescopic system  1  which has only two profile rails  2 , a first profile rail  2   a  which here is arranged downwardly and a second profile rail  2   b  which here is arranged upwardly. The two profile rails  2  bear slidingly displaceably against each other by way of two sliding element pairs  31  each with two sliding elements  3 , wherein one sliding element pair  31  is in non-displaceable contact with the here upper profile rail  2  and a sliding element pair  31  is in non-displaceable contact with the here lower profile rail  2 . The sliding elements  3  shown in the end view in  FIG.  7    are connected non-displaceably to the here lower profile rail  2 . As can be clearly seen in both sliding elements  3  the two longitudinal projections  33  extend jointly from one side of the base  34  in the second transverse direction q 2  and more specifically here inwardly with respect to the second transverse direction q 2 . In relation to both sliding elements  3  a respective longitudinal projection  33  referred to as the first longitudinal projection  332  extends with its free end region  333  in that common direction and engages into an associated longitudinal groove  22  of the profile rail  2  which is the upper rail in  FIG.  7   . As can be seen from  FIG.  7    by means of the blackening surrounding the free end region  333  of that longitudinal projection  33  and representing a clamping element  4  a clamping element  4  is arranged with a clamping fit in that longitudinal groove  22  of the upper profile rail  2 . Docked thereto is the longitudinal projection  33  and therewith the respectively associated sliding element  3  in itself non-displaceably with respect to the sliding plane G. The other longitudinal projection  33  referred to as the second longitudinal projection  334  extends from the base  34  with a portion  337  in the direction towards the here upper profile rail  2 . In a free end region  333  adjoining the portion  337  the longitudinal projection is bent over in a hook-like configuration about an axis of curvature parallel to the longitudinal direction l, forming a receiving groove  335 . The free end region  333  of the second longitudinal projection  334  extends towards the lower profile rail  2  in  FIG.  7   . The free end region  333  engages into an associated longitudinal groove  22  in that lower profile rail  2 . As can be seen from the blackening which here is incomplete no clamping element  4  is provided at that end, shown in  FIG.  7   , of the telescopic system  1  in the longitudinal groove  22 . Accordingly the two sliding elements  3  are slidingly displaceably connected at that location to the here lower profile rail  2 . The longitudinal grooves  22  associated with those longitudinal projections  33  are respectively laterally open in the second transverse direction q 2 . 
     As can further be seen from  FIG.  7    the second longitudinal projection  334  extends with its portion  337  in the second transverse direction q 2  here between the longitudinal groove  22  of the upper profile rail  2  for the first longitudinal projection  332  and the longitudinal groove  22  of the lower profile rail  2  for the second longitudinal projection  334 . In that region the sliding element  3  and the respective longitudinal groove  22  bear play-free or almost play-free against each other by way of sliding guide surfaces  5  here referred to as first sliding guide surfaces  51 . Those sliding guide surfaces  51  are here arranged perpendicularly to the first transverse direction q 1  or, with respect to  FIG.  7   , vertically. In that way the two profile rails  2  are held against each other in securely guided relationship with respect to the first transverse direction q 1  by way of the sliding element at the first sliding guide surfaces  51 . 
     As can be seen inter alia from  FIGS.  6  and  7    a rib-like further longitudinal projection  336  extends in a prolongation of the base  34 , more specifically parallel to the sliding plane G and in the embodiments of the telescopic system  1  shown in the Figures radially outwardly with respect to the longitudinal direction l. The rib-like further longitudinal projection engages into a further longitudinal groove  221 , which here is radially outward, in an associated profile rail  2 , as shown in  FIG.  7    the lower profile rail  2 . That further longitudinal groove  221  is open radially inwardly laterally in the first transverse direction q 1 , more specifically here with respect to the longitudinal direction l. Similarly to the second longitudinal projection  334  the further longitudinal projection  336  in its free end region  333  is bent over in a hook-like configuration parallel to the longitudinal direction l. In that way it defines a further receiving groove  338 . That further receiving groove  338  is identical to the further longitudinal groove  221  in the first transverse direction q 1  and here more specifically is of a radially inwardly laterally open configuration with respect to the longitudinal direction l. A receiving rib  231  provided at the upper profile rail  2  in  FIG.  7    engages into the further receiving groove  338  in the installed condition. The further longitudinal projection  336  is defined radially inwardly in relation to its axial extent in the first transverse direction q 1  at least over the axial extent of its further receiving groove  338  with respect to the longitudinal direction l. Accordingly the two longitudinal profiles  2  bear play-free or almost play-free in the region of the further receiving groove  338  against the wall of the further longitudinal groove  221  of the lower profile rail  2  and the wall of the receiving rib  231  of the upper profile rail  2 , more specifically by way of the further longitudinal projection  336  of the sliding element  3 . The surfaces at which that play-free or almost play-free contact occurs are here in the form of sliding guide surfaces  5  referred to as second sliding guide surfaces  52 . The second sliding guide surfaces  51  extend in or in opposite relationship to the second transverse direction q 2 . They are arranged horizontally in the Figures. Accordingly the two profile rails  2  are arranged held against each other in securely guided relationship with respect to the second transverse direction q 2  by way of the sliding element  3 . 
     In assembly one of the two longitudinal projections  33 , associated with that longitudinal groove  22 , is displaced with its receiving recess  331  axially over the clamping element  4  and is lowered into the receiving recess  331  towards the clamping element  4  with positively locking mounting of the clamping element  4 .  FIGS.  3 A- 5 C  show side views and sectional views of various assembly steps for assembling two profile rails  2  to form the telescopic system  1 .  FIGS.  3 A- 3 C  and  FIGS.  4 A- 4 B  show the assembly of the sliding element pair  31  respectively associated with a profile rail  2 . In this case as already previously the required clamping elements  4  are moved into a clamping fit at the appropriate locations in the respective longitudinal groove  22 . In  FIG.  3 A  the sliding element  3  which here is at the right is already non-displaceably connected to the lower profile rail  2 , by the sliding element  3  being connected in positively locking relationship to the associated clamping element  4 . In  FIG.  3 B  the sliding element  3  at the left is firstly brought into engagement with the further longitudinal groove  221  with its further longitudinal projection  336 . Parallel thereto the sliding element  3  is pivoted upwardly here at the further longitudinal groove  221  so that it can be slidingly displaced in the further longitudinal groove  221  with its second longitudinal projection  334  having the receiving recess  331 , by way of the associated clamping element  4 , and is positioned with its receiving recess  331  relative to the second transverse direction q 2  in aligned relationship with the clamping element  4 . That is shown in  FIG.  3 B . Then the sliding element  3  is pivoted down over the clamping element  4  whereby the clamping element  4  is connected to the sliding element in positively locking relationship. That is shown in  FIG.  3 C . 
     The procedure is similar when mounting the sliding element  3  to the other profile rail  2  shown in  FIGS.  4 A- 4 B . Here the sliding element  3  which is at the right is already non-displaceably connected to the other profile rail  2  while the sliding element  3  at the left is still involved in being fitted. For that purpose the sliding element  3  at the left is pushed with the receiving groove  335  of the its further longitudinal projection  336  on to the receiving rib  231  of the other profile  2  in the longitudinal direction and at the same time pivoted on the receiving rib  23  in the second transverse direction q 2  until here too the receiving recess  231  is positioned in alignment with the associated clamping element  4  with respect to the second transverse direction q 2 . Then the sliding element  3  is again pivoted down over the clamping element  4  with positively locking fitment thereof. 
     An effective tongue-and-groove connection is achieved inter alia in the first transverse direction q 1  with the engagement of the two longitudinal projections, that is to say the first longitudinal projection and the second longitudinal projection, of the sliding element  3  respectively in the second transverse direction q 2  into the respectively associated longitudinal groove  22  of the respective profile rail. A tongue-and-groove connection which is operative inter alia with respect to the second transverse direction q 2  is achieved with the engagement of the further longitudinal projection  336  of the sliding element  3  into the associated further longitudinal groove  221  and of the rib  231  into the further receiving groove  338  of the further longitudinal projection  336 . That means that the two profile rails have to be pushed into each other at the ends in the longitudinal direction l in the assembly procedure. In  FIGS.  5 A- 5 C  the two profile rails  2  equipped with the sliding elements  3  are pushed at the ends into each other. To facilitate that assembly procedure, a number of measures are afforded, as described hereinbefore. One of these is that the sliding guide surfaces  5  of the sliding elements  3  each have a bevel operative in the longitudinal direction l, in the form of inclined insertion portions  35 . In addition the inclined insertion portions  35  of the first sliding guide surfaces  51  are arranged spaced in relation to the inclined insertion portions  35  of the second sliding guide surfaces  52  by the amount a shown in  FIG.  6 C  in the longitudinal direction l. In that way the operation of “threading in” the profile rails  2  at the respective sliding guide surfaces  51 ,  52  is displaced in location with respect to an axial insertion path of movement relative to the longitudinal direction l, over the axial extent of the sliding elements  3 . In addition the first sliding guide surfaces  51  are arranged radially inwardly with respect to the longitudinal direction l and the second sliding guide surfaces  52  are arranged radially outwardly, which also permits displaced threading-in engagement at the first sliding guide surfaces  51  relative to the second sliding guide surfaces  52 . 
     The further longitudinal groove  221  has an undercut configuration  339  operative in the first transverse direction q 1 . At that undercut configuration, the further longitudinal projection  332  adapted to the further longitudinal groove is arranged held in positively locking relationship to prevent a possible relative movement in the first transverse direction q 1 . By virtue of those measures, the two profile rails  2  as well as the sliding element which embraces the receiving rib  231  can be at least stabilized in position in relation to a relative movement in the first transverse direction. 
     An additional longitudinal groove  222  which is open laterally in the second transverse direction q 2  is provided to afford anti-tipping security, in the longitudinal profile of the lower profile rail  2  in  FIG.  7    for the sliding element  3 . The sliding element  3  is arranged in positively locking relationship in the additional longitudinal groove  222 . For that purpose it bears with its base  34  in surface contact against the bottom of the longitudinal groove  222  and in the first transverse direction q 1  at both sides. The support effect is afforded at the one side by way of its further longitudinal projection  336  in the further longitudinal groove  221 . At the other side the support is provided externally at the longitudinal groove  22  associated with the second longitudinal projection  334 , more specifically by way of the portion  337  of that longitudinal projection  336 . 
     To delimit the travel distance w of two profile rails  2  which are guided against each other and which are moveable relative to each other there is an abutment device  6  which is shown primarily in  FIGS.  9 A- 10 C . The abutment device  6  has two end abutments  61  axially spaced with respect to the longitudinal direction l and an abutment element  62  cooperating with the end abutments  61 . Here clamping elements which are like the above-described clamping elements  4  serve as the end abutments  61 . In addition the clamping elements  4  which are not shown here have dampers operative in the longitudinal direction l. The clamping elements  4  are respectively fixed in the end region of one of the two profile rails  2  in the abutment groove  63 . The abutment element  62  is here fixed centrally with respect to the longitudinal direction l in a further abutment groove  64  by means of a further clamping element  4 . The abutment element  62  projects for abutting against the two end abutments  61  out of the further abutment groove  64  between the two end abutments  61  into the abutment groove  63 . As can be seen for example from  FIG.  2 C  the further abutment groove  63  has two guide grooves  65  which are provided in the second transverse direction q 2  and which are in mirror-image symmetrical relationship with the sliding plane G and into which the abutment element  62  latchingly engages upon assembly. For assembly purposes the clamping element  4  is clamped fast at a given location in the further abutment groove  63 . Then the abutment element  62  is put over the clamping element  4  in the first transverse direction q 1  with latching engagement in the guide grooves  65  with its receiving recess  331 . 
     Referring to  FIGS.  1 A- 5 C and  8 A- 9 C  the telescopic system  1  has three profile rails  2 , that is to say two first profile rails  2   a  which here are arranged outwardly and a second profile rail  2   b  which is arranged between the two first profile rails  2   a.  It is generally sufficient to provide two profile rails  2  only on one side of the longitudinal profile  21 . Because of the abutment grooves  63 ,  64 , with an arrangement of the abutment device  6  at one side, there is an asymmetry in regard to the cross-section of the lower first profile rail  2   a.  Referring to  FIG.  2 D  the abutment device  6  for limiting the travel movement between the upper outer profile rail  2  and the central profile rail  2  is arranged at the left-hand side of the telescopic system  1  and the abutment device  6  for limiting the travel movement between the lower outer profile rail  2  and the central profile rail  2  is arranged at the right-hand side of the telescopic system  1 . Nonetheless the two outer first profile rails  2   a  can be of identical structure insofar as they are arranged with their longitudinal profiles  21  facing towards each other and rotated relative to each other through  180 ° about the second transverse axis. At its sides towards the two outer first profile rails  2   a  the central second profile rail  2   b  has a respective identical longitudinal profile  21  which is the same as the longitudinal profile  21  of the upper second profile rail  2   b  described with reference to  FIG.  7   . 
     The telescopic system  1  shown in an end view in  FIG.  8    has five telescopic rails  2 : two outwardly arranged first profile rails  2   a,  a centrally arranged first profile rail  2   a,  provided at both sides with identical longitudinal profiles  21 , and two second profile rails  2   b  respectively between one of the outwardly arranged first profile rails  2   a  and the centrally arranged first profile rail  2   a,  provided at both ends with identical longitudinal profile  21 . It will be clear therefrom that the number of profile rails  2  can be enlarged by the profile rails  2  which are mounted slidingly displaceably against each other by way of the sliding elements being combined in such a way that at one of the mutually facing sides they have a longitudinal profile  21  of the first profile rail  2   a  and at the other of the mutually facing sides a longitudinal profile  21  of the second profile rail  2   b.    
     LIST OF REFERENCES 
     
         
           1  telescopic system 
           2  profile rail 
           21  longitudinal profile 
           22  longitudinal groove 
           221  further longitudinal groove 
           222  additional longitudinal groove 
           23  longitudinal rib 
           231  receiving rib 
           2   a  first profile rail 
           2   b  second profile rail 
           3  sliding element 
           31  sliding element pair 
           32  longitudinal profile 
           33  longitudinal projection 
           331  receiving recess 
           332  first longitudinal projection 
           333  free end region 
           334  second longitudinal projection 
           335  receiving groove 
           336  further longitudinal projection 
           337  portion 
           338  further receiving groove 
           339  undercut configuration 
           34  base 
           35  inclined insertion portion 
           4  clamping element 
           5  sliding guide surface 
           51  first sliding guide surface 
           52  second sliding guide surface 
           6  abutment device 
           61  end abutment 
           62  abutment element 
           63  abutment groove 
           64  further abutment groove 
           65  guide groove 
         G sliding plane 
         S 1  first plane of mirror-image symmetry 
         S 2  second plane of mirror-image symmetry 
         a spacing 
         l longitudinal direction 
         q 1  first transverse direction 
         q 2  second transverse direction 
         w travel distance