[0001] The invention relates to a ventilation and/or flue gas discharge system for coupling
               thereto one or more combustion devices and/or one or more ventilation devices or ventilation
               grilles.
 
            [0002] Separate or combined ventilation and flue gas discharge systems are installed in
               practice for ventilation purposes, such as for instance for supplying and/or discharging
               fresh air to and/or from a space, for discharging flue gases from heating devices
               or other combustion devices such as ovens, and for instance for supplying combustion
               air thereto.
 
            [0003] These ventilation and flue gas discharge systems are constructed nowadays from plastic
               or metal tubes or pipes, such as tubes or pipes of polypropylene, aluminium or stainless
               steel. The pipe material to be selected depends here on, among other factors, the
               type of combustion device, i.e. the type of combustion material such as gas, oil or
               wood, the final temperature of the flue gas to be discharged, which in higher efficiency
               devices will be lower than in the case of lower efficiency devices, and the degree
               of condensation in the pipe system.
 
            [0004] Not only ventilation and flue gas discharge channels to be replaced but also those
               to be newly installed are constructed in practice in the form of pipe systems assembled
               from mutually coupled pipe segments.
 
            [0005] An example of a single pipe system is described in, among others, the non-prepublished
               Netherlands patent application 
1041532, filed simultaneously in the name of applicant, with the title: "Pipe system, coupling
               piece and method for installing the pipe system in a shaft of a building".
 
            [0006] In an embodiment of this pipe system the tubular coupling pieces are provided with
               at least one connecting opening for connection thereto of a branch pipe or branch
               pipe part. The branch pipe then leads to an appliance to be connected to the pipe
               system.
 
            [0007] Known from the British patent 
GB 287 335, the American patent 
US 4 781 402 and the European patent application 
EP 1 795 804 are ventilation and/or flue gas discharge systems consisting of a coaxially or concentrically
               mounted inner pipe and outer pipe which engage each other by means of respectively
               screw threaded connections, hook connections and screw connections, whereby the assembly
               of such ventilation and/or flue gas discharge systems is laborious and time-consuming.
 
            [0008] The invention has for its object to provide a solution for installing a combined
               ventilation and flue gas discharge system consisting of a coaxially or concentrically
               mounted inner pipe and outer pipe, particularly for a segment-wise assembling of such
               combined ventilation and/or flue gas discharge system.
 
            [0009] The invention provides for this purpose a ventilation and/or flue gas discharge system
               comprising an inner pipe and outer pipe connectable by at least one locking element,
               wherein the or each locking element is attached to one of the inner pipe or outer
               pipe and wherein the other of the inner pipe or outer pipe is provided with at least
               one coupling element co-acting with a locking element such that in mounted state of
               the inner pipe in the outer pipe the or each locking element engages a coupling element
               and the inner pipe is coupled locked in longitudinal direction to the outer pipe,
               characterized in that, the or each locking element is mounted pivotally in at least
               one of tangential, radial or axial direction of an inner pipe or outer pipe.
 
            [0010] The pivoting action with which the locking element engages on the coupling element
               makes it possible, by a respective relative movement of the inner pipe and outer pipe,
               to easily mount the inner pipe in and remove same from the outer pipe.
 
            [0011] Such an assembly of a coupled inner pipe and outer pipe can also be provided from
               factory as a single integrated unit or be mounted if necessary on site. The invention
               then makes it possible to couple such units in simple and flexible manner in order
               to assemble a complete concentric ventilation and/or flue gas discharge system.
 
            [0012] In an embodiment the at least one locking element is attached resiliently to one
               of the inner pipe or outer pipe in radial direction thereof and the or each locking
               element and a coupling element co-acting therewith are designed relative to each other
               such that in mounted situation a locking element engages a respective coupling element
               in a form-locking and, through the resilient action, also in a force-locking manner,
               whereby a firm and durable locking is obtained.
 
            [0013] The resilient, pivoting action of the locking element in axial and radial direction
               of one of the inner pipe or outer pipe achieves that, when the inner pipe is introduced
               into the outer pipe in longitudinal or axial direction from a first end thereof, at
               the position of the coupling element the locking element can engage the coupling element
               and that during engagement, movement of the inner pipe in longitudinal direction of
               the outer pipe is blocked.
 
            [0014] In a further embodiment is the outer pipe, on its inner peripheral wall, provided
               with at least one coupling element in the form of a cam-like element protruding inward
               in radial direction, and the inner pipe is provided on its outer peripheral wall with
               at least one resilient locking element coupled thereto.
 
            [0015] In an embodiment of the invention the at least one cam-like element is particularly
               a cam running around in tangential direction, in particular a substantially semi-circular
               cam-like protrusion formed from the material of the peripheral wall wherein the locking
               element is provided with a correspondingly dimensioned semi-circular recess in radial
               direction of the inner pipe for receiving the peripheral cam in a form-locking manner
               therein.
 
            [0016] The semi-circular shape of the cam and recess in the locking element facilitate engagement
               of the cam and the locking element when the inner pipe is received in longitudinal
               direction or axial direction in the outer pipe.
 
            [0017] In an embodiment in which the inner pipe comprises a tubular coupling piece, such
               as a coupling piece formed as a sleeve for mutual coupling of inner pipe segments,
               the or each locking element is coupled to the coupling piece.
 
            [0018] A tubular coupling piece suitable for use with the invention is disclosed in the
               above-mentioned non-prepublished Netherlands patent application 
1041532 filed simultaneously in the name of applicant with the title: "Pipe system, coupling
               piece and method for installing the pipe system in a shaft of a building", and in
               the non-prepublished Netherlands patent application 
1041526 filed simultaneously in the name of applicant with the title: "Tubular coupling piece
               and branch pipe, particularly for use in a pipe system of a ventilation or flue gas
               discharge channel".
 
            [0019] In a further embodiment the invention provides a ring element attachable to the outer
               peripheral wall of the inner pipe and/or to the outer peripheral wall of a tubular
               coupling piece, wherein the at least one locking element is coupled to the ring element.
 
            [0020] Through the use of such a ring element, for instance in the form of a clamping ring
               for clamping around an inner pipe or coupling piece, configured for mounting of a
               locking element thereon or with a locking element mounted thereon, the inner pipe
               can consist of a per se known and commercially available cylindrical pipe.
 
            [0021] Although the locking element can be attached fixedly to the inner pipe, outer pipe
               or to a tubular coupling piece or to the ring element, the invention provides an embodiment
               wherein the at least one locking element is releasably attached.
 
            [0022] Such a releasable coupling or attachment of the locking element, particularly wherein
               the locking element is uncoupled when the inner pipe is moved out of the outer pipe
               in the direction opposite to the direction in which the inner pipe has been introduced
               into the outer pipe, facilitates disassembly of the assembled ventilation and/or flue
               gas discharge system.
 
            [0023] For a stable concentric or coaxial mounting of the ventilation and/or flue gas discharge
               system it is preferable to apply at least two locking elements arranged at a distance
               from each other in tangential direction. In a preferred embodiment the invention provides
               for the use of four locking elements spaced 90 degrees apart in tangential direction.
 
            [0024] In an embodiment the locking element is of approximately rectangular shape with two
               side surfaces located at a distance from each other, with a recess on a long side
               thereof for engagement therein of a cam-like coupling element, and with a resilient
               tongue protruding outward in the direction away from the recess.
 
            [0025] The resilient action of the tongue operates such that in mounted situation a resilient
               force acts in radial direction on the locking element for engaging the locking element
               in force-locking manner on a coupling element.
 
            [0026] In a further embodiment the resilient tongue protrudes outward from a short side
               of the locking element and another short side of the locking element is provided with
               a receiving opening for receiving an attaching element clampingly therein, between
               the side surfaces, for attaching the locking element movably in radial direction to
               an attaching element.
 
            [0027] The attaching element or plurality of attaching elements can be mounted here on the
               outer periphery of the inner pipe, on the inner periphery of the outer pipe or form
               part of a tubular coupling piece or form part of the ring element as described above.
 
            [0028] In yet another embodiment, wherein the attaching element is mounted on the inner
               pipe or a coupling piece of the inner pipe, the receiving opening connects on the
               other short side of the locking element to an open space which is formed between the
               side surfaces from the other long side and which, as seen from the receiving opening,
               diverges outward at the end and wherein the attaching element tapers at the end in
               the direction away from the peripheral wall of the inner pipe such that, when the
               attaching element is received in the open space of the locking element in longitudinal
               direction from the receiving opening, the locking element moves radially outward.
 
            [0029] The tapering form of the attaching element and the open space in the locking element
               are adapted to each other such that, when the inner pipe is placed from a first end
               into the outer pipe and the locking element engages on the coupling element, the locking
               element is pressed in radial direction toward the coupling element and coupled firmly
               to the attaching element as the inner pipe is carried further into the outer pipe
               such that the inner pipe cannot be moved further in the outer pipe.
 
            [0030] During movement of the inner pipe in reverse direction the coupling is broken. Particularly
               in the embodiment in which the locking element engages clampingly on the attaching
               element the inner pipe can be removed easily from the outer pipe again by exerting
               force.
 
            [0031] The invention also provides an inner pipe constructed from pipe segments coupled
               in longitudinal direction as described in particular in the above stated non-prepublished
               Netherlands patent applications in the name of applicant, the content of both of which
               is deemed as included herein.
 
            [0032] The outer pipe can also be constructed from pipe segments coupled in longitudinal
               direction, wherein according to the invention each outer pipe segment has a smaller
               diameter at a second end than at a first end thereof, or has a greater diameter at
               the first end than at the second end, for the purpose of receiving with the second
               end an outer pipe segment in the first end of another outer pipe segment, wherein
               the at least one locking element or coupling element is located close to the first
               end or close to the second end in an outer pipe segment.
 
            [0033] In order to facilitate mounting of outer pipe segments, i.e. mounting thereof at
               a desired length, each outer pipe segment is provided in an embodiment of the invention
               with a graduation scale running on the outer periphery of a pipe segment from the
               second end in the direction of the first end.
 
            [0034] In an embodiment the outer pipe, or an outer pipe segment, is provided in its peripheral
               wall, between the position where the at least one locking element or coupling element
               is located and the second end, with at least one connecting opening and/or passage
               opening for connection thereto and/or passage therethrough of a branch outer pipe
               to be connected to the ventilation and/or flue gas discharge system.
 
            [0035] In yet another embodiment of the ventilation and/or flue gas discharge system a branch
               outer pipe to be connected to the connecting opening on the outer periphery of an
               outer pipe engages fluid-tightly on the outer periphery of the outer pipe by means
               of a saddle gasket. The saddle gasket has an upright slot-like edge for receiving
               an end of the branch outer pipe therein.
 
            [0036] The branch outer pipe does not then protrude in the outer pipe, whereby removal of
               an inner pipe from the outer pipe is not obstructed, for instance during later renovation
               wherein the inner pipe system has to be replaced.
 
            [0037] The branch outer pipe can be fixedly attached by screws or the like by means of for
               instance tongues attached on the edge of the connecting opening or passage opening
               to the wall of the outer pipe or formed therefrom.
 
            [0038] The invention also provides an assembly of at least one coupled inner pipe and outer
               pipe locked in longitudinal direction as described in the foregoing.
 
            [0039] The invention also provides an outer pipe segment for a ventilation and/or flue gas
               discharge system as described in the foregoing and a locking element for a ventilation
               and/or flue gas discharge system as described in the foregoing.
 
            [0040] The invention is now elucidated by way of example in more detail with reference to
               the accompanying figures. The invention is by no means limited to the embodiment of
               the invention shown in the figures. The same or similar elements also have the same
               reference numerals in the figures.
               
               
Figure 1 shows schematically and in partial cross-section a ventilation and/or flue
                  gas discharge system constructed from mutually connectable concentric inner pipe segments
                  and outer pipe segments according to an embodiment of the invention and installed
                  in a building consisting of multiple storeys.
               Figure 2 shows schematically and in perspective on enlarged scale a detail of the
                  ventilation and/or flue gas discharge system according to figure 1 wherein the outer
                  pipe segments are shown partially broken-away.
               Figure 3 shows schematically and in perspective on enlarged scale a detail of the
                  ventilation and/or flue gas discharge system according to figure 1 wherein the outer
                  pipe segments, inner pipe segments and pipe coupling are shown partially broken-away
                  as seen along the line III-III in figure 2.
               Figure 4 shows schematically and in perspective a cross-section of a locking element
                  as shown in figures 1, 2 and 3 coupled to an attaching element of a coupling piece.
               Figures 5A-F show schematically and in perspective the successive assembly and disassembly
                  of an inner pipe in an outer pipe in accordance with an embodiment of the invention.
               Figure 6 shows schematically and in perspective on enlarged scale a detail of two
                  coupled outer pipe segments as shown in figure 1.
               Figure 7 shows schematically, in perspective and not to scale an annular element with
                  attaching elements for locking elements.
 
            [0041] Shown schematically in figure 1 is an assembled ventilation and/or flue gas discharge
               system 10 according to an embodiment of the invention in a building consisting of
               multiple storeys 11, 12. The ventilation and/or flue gas discharge system 10 comprises
               two pipe systems placed concentrically or coaxially relative to each other, viz. an
               outer pipe system 14 and an inner pipe system 15 received in the outer pipe system.
 
            [0042] In the shown example the outer pipe system 14, as seen in the direction from the
               ground floor 11 to the roof 13, is constructed from pipe segments coupled in longitudinal
               direction, viz. a first cylindrical outer pipe segment 23, a second cylindrical outer
               pipe segment 24 and a third cylindrical outer pipe segment 25.
 
            [0043] The second outer pipe segment 24 is received fitting with an end in an end of the
               first outer pipe segment 23. The third outer pipe segment 25 is received fitting with
               an end in another end of the second outer pipe segment 24 and the other end of the
               third outer pipe segment 25 ends on the roof 13 of the building in an end 19 of the
               outer pipe system 14 which is open to the outside air.
 
            [0044] In the example shown the inner pipe system 15, as seen in the direction from the
               ground floor 11 to the roof 13, is likewise constructed from pipe segments coupled
               in longitudinal direction, viz. a first cylindrical inner pipe segment 26, a second
               cylindrical inner pipe segment 27 and a third cylindrical inner pipe segment 28.
 
            [0045] The inner pipe segments 26, 27, 28 are mutually coupled respectively via intermediate
               tubular coupling pieces, viz. a first cylindrical tubular coupling piece 29, a second
               cylindrical tubular coupling piece 30 and a third cylindrical tubular coupling piece
               31. The first inner pipe segment 26 is received fitting with an end in the first coupling
               piece 29 and received fitting with another end in the second coupling piece 30. The
               second pipe segment 27 is received fitting with an end in the second coupling piece
               30 and received fitting with another end in the third coupling piece 31. The third
               pipe segment 28 is received fitting in an end of the third coupling piece 31 and the
               other end of the third pipe segment 27 ends on the roof 13 of the building in an end
               32 of the pipe system 15 which is open to the outside air.
 
            [0046] Although the ventilation and/or flue gas discharge system 10 can be constructed in
               each case by coupling separate inner pipe segments and outer pipe segments, according
               to the invention the shown ventilation and/or flue gas discharge system 10 can advantageously
               also be constructed in each case from assemblies, to be coupled to each other, of
               an already coupled respective inner pipe segment and outer pipe segment 23, 26; 24,
               27 and 25, 28.
 
            [0047] Assembly substantially always takes place in practice in the situation where only
               the floors and walls of storeys 11, 12 have been built, wherein the lowest assembly
               can for instance be placed by means of floor supports (not shown) at a desired height
               and/or by means of fixing brackets or floor brackets 65 which rest on a party floor
               and which engage on a respective outer pipe segment, such as the outer pipe segment
               23.
 
            [0048] In the shown example the inner pipe system 15 functions as flue gas discharge system
               and the outer pipe system 14 functions as ventilation system or combustion air supply
               system for combustion devices 16, 17, 18 connected to the ventilation and/or flue
               gas discharge system 10. Located on the ground floor 11 in the shown embodiment are
               two combustion devices 17, 18, such as a central heating boiler and/or a hot water
               appliance. Situated on the first floor 12 of the building in the shown embodiment
               is a single combustion device 16.
 
            [0049] The combustion devices 16, 17, 18 are connected via respective concentric branch
               pipes or branch pipe parts 22, 21, 20 to the ventilation and/or flue gas discharge
               system 10. The concentric branch pipes 20, 21, 22 each consist of a branch inner pipe
               part 33 lying concentrically in a branch outer pipe part 34. The branch inner pipe
               parts 33 are connected here via a respective coupling piece 29, 31 to the inner pipe
               segment 15 through a passage opening or connecting opening 69 in the peripheral wall
               of an outer pipe segment. The branch outer pipe parts 34 are connected via the peripheral
               wall of a respective outer pipe segment 23, 24 to the outer pipe system 14. No devices
               are connected to the second coupling piece 30. In the shown embodiment this coupling
               piece functions solely for the purpose of connecting the first and second inner pipe
               segments 26, 27.
 
            [0050] Figure 2 shows by way of example on enlarged scale a detail of the ventilation and/or
               flue gas discharge system 10 according to figure 1, comprising the third tubular coupling
               piece 31. In the shown embodiment the branch outer pipe part 34 engages fluid-tightly
               on the outer periphery of the outer pipe segment 24 by means of a saddle gasket 66
               located around the passage opening or connecting opening 69. The saddle gasket 69
               has an upright slot-like edge 67 here for receiving an end of the branch outer pipe
               part 34 therein. The branch outer pipe part 34 does not then protrude into the outer
               pipe segment 24, whereby removal of an inner pipe from the outer pipe is not obstructed,
               for instance during later renovation wherein the inner pipe system has to be replaced.
 
            [0051] The branch outer pipe part 34 can be fixedly attached by screws 68 or the like by
               means of for instance tongues 70 attached on the edge of the connecting opening or
               passage opening 69 to the wall of the outer pipe segment 24 or formed therefrom (see
               figure 3).
 
            [0052] Although the combustion devices 16, 17, 18 are all shown mounted at the same height,
               it should be understood that these devices and their branch pipe parts 20, 21, 22
               to the ventilation and/or flue gas discharge system 10 on the various floor levels
               11, 12 can be located at different heights.
 
            [0053] Although not shown, the end 35 of the inner pipe system 15 and/or the outer pipe
               system 14 can be connected to an outlet for discharging fluid which has accumulated
               in a pipe system, such as condensed water from flue gas to be discharged and/or combustion
               air to be supplied. Although not shown explicitly, it will be understood that the
               ventilation and/or flue gas discharge system 10 can also be installed in an existing
               flue gas discharge shaft of a building.
 
            [0054] Although the outer pipe system 14 is applied as combustion air supply channel in
               figure 1, it should be appreciated that the outer pipe system 14 can also be used
               as ventilation channel, wherein one or more of the devices 16, 17, 18 are for instance
               air discharge devices or air grilles.
 
            [0055] The first, second and third coupling pieces 29, 30, 31 may substantially each be
               of differing form. From the viewpoint of costs and convenience of mounting it is advantageous
               to couple the pipe segments to each other by means of a uniform coupling piece and
               to connect the various devices hereto via a uniform branch pipe part.
 
            [0056] As shown in figure 2, the coupling piece 31 has a cylindrical, tubular and elongate
               peripheral wall 36 which extends between an inlet end 37 and the outlet end 38 of
               the coupling piece 31. The inlet end 37 and the outlet end 38 are suitable for receiving
               therein a pipe segment of the inner pipe system 15, such as respectively the third
               28 and second pipe segment 27 as shown in figure 1. Attaching elements 42 spaced apart
               in tangential direction and protruding outward from the peripheral wall 36 are arranged
               close to the inlet end 37 of the coupling piece 31. The coupling piece 31 is provided
               in similar manner at its outlet end 30 with attaching elements 43 protruding outward
               from the peripheral wall 36.
 
            [0057] Between the inlet end 37 and the outlet end 38 the coupling piece 31 is provided
               in its peripheral wall 36 with first and second opposite connecting openings 40, 41
               for connection of a branch inner pipe 33 thereto. In the shown embodiment the branch
               inner pipe 33 is connected via a self-positioning releasable screw coupling to the
               connecting opening 40. The connecting opening 41 is closed using a cover 39, this
               as described in the non-prepublished Netherlands patent application 
1041526 filed simultaneously in the name of applicant with the title: "Tubular coupling piece
               and branch pipe, particularly for use in a pipe system of a ventilation or flue gas
               discharge channel".
 
            [0058] Designated with the reference numeral 45 is a semi-circular cam running all-around
               in tangential direction and protruding inward in radial direction in the outer pipe
               segment 24 on its inner peripheral wall 44 as embodiment of a coupling element co-acting
               with the locking element 46. The cam 45 is formed in this embodiment as a cam-like
               protrusion which is directed inward out of the material of the outer pipe segment
               24 and on which according to the invention different locking elements 46 located at
               a distance from each other in tangential direction engage in form-locking and force-locking
               manner. These locking elements 46 are of approximately rectangular form in the shown
               embodiment, with a semi-circular recess 47 formed in a long side thereof and dimensioned
               in accordance with the cam 45 for receiving the peripheral cam 45 form-lockingly therein.
               The semi-circular recess 47 runs in radial direction of the inner pipe segments 27,
               28.
 
            [0059] Each locking element 46 has two side surfaces 48, 49 located at a distance from each
               other and connected to each other via an upper 53 and lower short side 54. The recess
               47 for receiving the cam 45 therein is located on a front long side 51 of the locking
               element 46. A resilient tongue 50 extends outward from the lower short side 54 of
               the locking element 46 in the direction away from the recess 47, in this case away
               from the front long side 51. The other upper short side 53 of the locking element
               46 is provided with a receiving opening 55 for receiving an attaching element 42,
               43 between the side surfaces 48, 49 for coupling a locking element 46 to an attaching
               element 42, 43 for movement in radial direction of the inner pipe or the coupling
               piece 31.
 
            [0060] The side surfaces 48, 49 are disposed at a distance relative to each other and the
               locking element 46 is formed from a resilient plastic material such that the locking
               element 46 can be placed clampingly onto an attaching element 42, 43. That is, an
               attaching element 42, 43 is coupled clamped between the side surfaces 48, 49 to the
               locking element 46.
 
            [0061] The pivoting coupling of a locking element 46 to an attaching element 43 is shown
               in more detail in figure 3. Via the above described clamping coupling of an attaching
               element 43 between their side surfaces 48, 49 the locking elements 46 are coupled
               releasably to an attaching element 42, 43. The resilient tongue 50 achieves that the
               locking element 46 is pivotally resilient in axial and radial direction of the concentric
               pipe system in that the resilient tongue 50 pushes with its free end against the outer
               peripheral wall 36 of an inner pipe segment 26, 27, 28. In mounted situation of the
               inner pipe system 15 in the outer pipe system 14 the resilient tongue 50 ensures that
               the locking elements 46 engage under resilient force in force-locking manner on the
               cams 45, whereby the inner pipe system 15 is locked in longitudinal direction to the
               outer pipe system 14 via the coupling pieces 29, 30, 31.
 
            [0062] In the shown embodiment the force acting in radial direction on a locking element
               46 for the purpose in mounted situation of firm engagement thereof on the cam 45 of
               an outer pipe is further increased in that the receiving opening 55 on the upper short
               side 53 of the locking element 46 connects to an open space 56 formed between the
               side surfaces 48, 49 from the rear long side 52. This open space 56, as seen from
               the receiving opening 55, diverges outward at the end in wedge form 57. The attaching
               elements 42, 43 taper at the end in wedge form 58 in the direction away from the peripheral
               wall 36 of the inner pipe or the coupling piece 31, this as illustrated in a cut-away
               detail drawing on enlarged scale of a locking element 46 in the situation mounted
               and coupled to an attaching element 43 in figure 4. Also shown herein is that for
               strengthening purposes the side walls 48, 49 of a locking element 46 are connected
               to each other via internal transverse ribs 59.
 
            [0063] When an attaching element 42, 43 is received in longitudinal direction in the open
               space 56 of the locking element 46 from the receiving opening 55, the locking element
               46 is moved outward in radially, axially pivoting manner by the shearing force action
               which the wedge-shaped ends 57, 58 exert here on each other. That is, the recess 47
               of the locking element is pressed firmly against the cam 45. Due to the releasable
               coupling of a locking element 46 to an attaching element 42, 43 it is also easy to
               remove a mounted inner pipe segment again from an outer pipe segment.
 
            [0064] Figures 5A-F illustrate in stepwise manner the assembly and respective disassembly
               of, by way of example, an inner pipe or inner pipe segment 27 in an outer pipe or
               outer pipe segment 24. The inner pipe segment 27 is attached here to a coupling piece
               31 and the locking elements 46 are embodied as discussed with reference to figures
               1 to 4. The full arrows indicate in each case the direction of movement of the inner
               pipe segment 27.
 
            [0065] Figure 5A shows the inner pipe segment 27 with the coupling piece 31 and the locking
               elements 46 clamped to the attaching elements 43 thereof. The cross-sectional dimensions
               of the inner pipe segment, the dimensions of the radially outward protruding locking
               elements 46 and the cross-sectional dimensions of the outer pipe segment 24 are adapted
               to each other such that the inner pipe segment 27 with the locking elements 46 fits
               closely into the outer pipe segment 24 from the first end 63 thereof. The locking
               elements 46 are oriented inclining slightly downward in order to facilitate insertion
               of the inner pipe segment 27 and the locking elements 46 into the outer pipe segment
               24 from the first end 63 thereof.
 
            [0066] Figure 5B shows the inner pipe segment 27 received so far into the outer pipe segment
               27 that the locking elements 46 lie with their recess 47 against the internal cam
               45 of the outer pipe segment 27.
 
            [0067] As the inner pipe segment 27 is placed further into the outer pipe segment 24, the
               locking elements 46 pivot and block at the position of the cam 45 because the cam
               45 engages in the recesses 47 of the locking elements 46, as shown in figure 5C. The
               attaching elements 43 have not yet been wholly received here from the receiving opening
               55 in the open space 56 of the locking elements 46.
 
            [0068] Figure 5D shows a fully mounted assembly 71 of an inner pipe segment and outer pipe
               segment of the pipe system, wherein the inner pipe segment 27 per with the coupling
               piece 31 is received wholly coaxially or concentrically in the outer pipe segment
               24 and wherein the locking elements 46 are urged in radial direction firmly against
               and into engagement with the cam 45 by the wedge-shaped parts 57, 58 acting on each
               other of respectively a locking element 46 and an attaching element 43.
 
            [0069] The inner pipe segment 27 is in this way locked firmly on the outer pipe segment
               24 and locked against downward movement in longitudinal direction of the outer pipe
               segment 24, i.e. in the direction of the solid arrow. Both pipe segments 24, 27 are
               dimensioned such that a connecting opening 40, 41 of the coupling piece 31 lies in
               mounted situation against a connecting opening 69 of the outer pipe segment 24 for
               the purpose of connecting a respective branch pipe part 22 as shown in figures 1,
               2 and 3.
 
            [0070] Owing to the coupling of a further outer pipe segment, such as the third outer pipe
               segment 25 shown in figure 3, to the outer pipe segment 24 in longitudinal direction
               thereof, a further inner pipe segment, such as the third inner pipe segment 28, can
               in turn be coupled to the second inner pipe segment 27 and locked to the third outer
               pipe segment 25, etc. The ventilation and/or flue gas discharge system 10, i.e. the
               concentric inner pipe system 15 and the outer pipe system 14, can in this way be constructed
               floor by floor or storey by storey.
 
            [0071] It will be understood that complete mounted assemblies or units 71 can also be mounted
               on each other to form a combined ventilation and/or flue gas discharge system 10.
 
            [0072] In the case of assembly in an existing shaft, the concentric ventilation and/or flue
               gas discharge system 10 can be built up segment by segment in the shaft from the roof
               of an apartment by lowering one mounted part of the ventilation and/or flue gas discharge
               system 10 at a time into the shaft and subsequently coupling the following part thereto,
               etc.
 
            [0073] Because the locking elements 46 are coupled releasably to the attaching elements
               43, the inner pipe segment 27 can easily be removed again from the outer pipe segment
               24 by moving the inner pipe segment 27 in the direction of the broken arrow in longitudinal
               direction, or axially, relative to the outer pipe segment 24 as shown in figure 5E
               and figure 5F.
 
            [0074] During the upward movement of the inner pipe segment 27 in the arrow direction the
               locking elements 46 remain in the first instance in engagement with the cam 45, whereby
               the attaching elements 43 release from the locking elements 46. The inner pipe segment
               27 can then be removed from the outer pipe segment 24 and the detached locking elements
               46 drop downward in the outer pipe segment 24 under the influence of gravitational
               force and can if desired be reused. Figure 5F shows the falling locking elements 46.
 
            [0075] Figure 6 illustrates a possible coupling of outer pipe segments 24, 25. Each outer
               pipe segment 24, 25 has for this purpose a second end 64 with a slightly smaller diameter
               than the first end 63 thereof. The second end 64 of the one outer pipe segment 25
               can hereby be received in the other outer pipe segment 24 over a distance from the
               first end 63 thereof. See also figures 2 and 3. The first end 63 can of course alternatively
               be provided with a slightly larger diameter than the second end 64.
 
            [0076] As shown in figure 6 and also in figures 2 and 3, the movement of the outer pipe
               segment 25 in the outer pipe segment 24 is blocked by a clamping ring 61 which engages
               over the first end 63 of the outer pipe segment 24. For the purpose of setting a desired
               length of the outer pipe system 14 each outer pipe segment is provided on its second
               end 64 with a graduation scale 62 running over a length along the peripheral wall.
 
            [0077] Figure 6 also shows that the outer pipe segment 24 is provided in its peripheral
               wall between the position where the cam 45, or the at least one cam-like element,
               is located and the first end 63 with at least one connecting opening and/or passage
               opening 69 for connection thereto and/or passage therethrough of branch pipes 33,
               34 to be connected to the ventilation and/or flue gas discharge system 10.
 
            [0078] As can be seen from the outer pipe segment 23 in figure 1, the at least one connecting
               opening and/or passage opening 69 can also be provided in the peripheral wall of the
               outer pipe segment between the position where the cam 45, or the at least one cam-like
               element, is located and the second end 64.
 
            [0079] It is further also noted that, instead of a concentric or coaxial embodiment 72 of
               a branch inner pipe part 33 and branch outer pipe part 34 as shown in figure 6, the
               branch pipe parts can each be connected separately at different locations.
 
            [0080] It will be understood that the peripheral cam 45 can consist of different individual
               cams which can lie spaced apart not only in tangential direction but for instance
               also in longitudinal direction of an outer pipe or outer pipe segment for the purpose
               of engaging locking elements likewise in spaced-apart distribution in for instance
               longitudinal direction and coupled to an inner pipe segment and/or coupling piece.
 
            [0081] The locking elements can further also be coupled directly to an inner pipe segment
               or via for instance an annular element, such as a clamping ring or the like, to be
               coupled to the inner pipe. Figure 7 shows an example of a clamping ring 60 provided
               with attaching elements 43 for coupling locking elements 46. The clamping ring 60
               is arranged here around the outer peripheral wall of an inner pipe segment 28. It
               will be appreciated that the clamping ring 60 can also be arranged around the outer
               peripheral wall of a coupling piece.
 
            [0082] The locking engagement of a locking element and coupling element can, with the same
               advantage as described for the locking elements pivoting in axial, radial direction,
               also be achieved with locking elements mounted pivotally in tangential, radial direction
               of an inner pipe or outer pipe. For instance wherein the attaching elements 42, 43
               are mounted rotated through a quarter turn compared to the embodiment as shown in
               figure 2 and figure 3 and the locking elements 46 engage on a cam-like coupling element
               45 formed in longitudinal direction of the outer pipe.
 
            [0083] In a practical embodiment use is for instance made of pipe segments or assemblies
               with fixed lengths in the range of 100-200 cm, preferably with a length of about 160
               cm, for use in buildings with storey heights of for instance 270-300 cm. The coupling
               pieces 29, 30, 31 can have a length here in the range of 40-60 cm, preferably about
               50 cm.
 
            [0084] Usual for the inner pipe segments are diameters in the range of 80-250 mm, and the
               outer pipe segments have in practice diameters of 100-400 mm. Systems with diameter
               combinations of 100/160, 130/200, 160/250 and 200/350 mm are preferably supplied,
               wherein the smaller diameter relates in each case to the inner pipe and the larger
               diameter relates to the outer pipe.
 
            [0085] The diameter of a coupling piece at a respective end 27, 28 is of course adapted
               here to the diameter of a pipe segment to be received therein. The branch inner pipe
               parts have for instance a diameter in the range of 30-80 mm, preferably a diameter
               of 32 mm or 75 mm, adapted to standard connecting diameters for combustion devices.
               The branch outer pipe parts can have diameters in the range of for instance 50-100
               mm.
 
            [0086] The coupling pieces, inner pipe segments, branch inner pipe parts and locking elements
               can be manufactured from, among other materials, polypropylene, PP, polybutylene terephthalate,
               PBT, or polyvinylidene fluoride, PVDF, with wall thicknesses of for instance 2-3 mm.
 
            [0087] The outer pipe segments and if desired the branch outer pipe parts are preferably
               manufactured from aluminium or stainless steel with a wall thickness of for instance
               1-2 mm.
 
          
         
            
            1. A ventilation and/or flue gas discharge system (10) comprising an inner pipe (15;
               26, 27, 28) and outer pipe (14; 23, 24, 25) connectable by at least one locking element
               (46), wherein the or each locking element (46) is attached to one of the inner pipe
               or outer pipe and wherein the other of the inner pipe or outer pipe is provided with
               at least one coupling element (45) co-acting with a locking element (46) such that
               in mounted state of the inner pipe in the outer pipe the or each locking element (46)
               engages a coupling element (45) and the inner pipe is coupled locked in longitudinal
               direction to the outer pipe, characterized in that, the or each locking element (46) is mounted pivotally in at least one of tangential,
               radial or axial direction of an inner pipe or outer pipe.
 
            2. The ventilation and/or flue gas discharge system (10) according to claim 1, wherein
               the at least one locking element (46) is resiliently attached (50) to one of the inner
               pipe or outer pipe in radial direction thereof, and wherein the or each locking element
               (46) and a coupling element (45) co-acting therewith are formed relative to each other
               such that in the mounted state a locking element (46) engages a respective coupling
               element (45) in a form-locking and through the resilient action also in a force-locking
               manner.
 
            3. The ventilation and/or flue gas discharge system (10) according to claim 2, wherein
               the outer pipe is provided on its inner peripheral wall (44) with at least one coupling
               element (45) in the form of a cam-like element protruding inward in radial direction,
               and the inner pipe is provided on its outer peripheral wall (36) with at least one
               resilient locking element (46) coupled thereto, particularly wherein the at least
               one cam-like element is a cam running around in tangential direction, in particular
               a substantially semi-circular cam-like protrusion formed from the material of the
               peripheral wall (44) wherein the locking element (46) is provided with a correspondingly
               dimensioned semi-circular recess (47) in radial direction of the inner pipe for receiving
               the peripheral cam in a form-locking manner.
 
            4. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, wherein the inner pipe comprises a tubular coupling piece (29;
               30; 31) and the at least one locking element (46) is attached to the coupling piece.
 
            5. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, comprising a ring element, such as a clamping ring, attachable
               to the outer peripheral wall (36) of the inner pipe or to the outer peripheral wall
               of a tubular coupling piece (29; 30; 31) of the inner pipe, wherein the at least one
               locking element (46) is attached to the ring element.
 
            6. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, wherein the at least one locking element (46) is releasably
               attached.
 
            7. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, comprising at least two locking elements (46) arranged at a
               distance from each other in tangential direction.
 
            8. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, wherein a locking element (46) is of approximately rectangular
               shape with two side surfaces (48, 49) located at a distance from each other, with
               a recess (47) on a long side (51) thereof for engagement therein of a cam-like coupling
               element (45), and with a resilient tongue (50) protruding outward in the direction
               away from the recess (47).
 
            9. The ventilation and/or flue gas discharge system (10) according to claim 8, wherein
               the resilient tongue (50) protrudes outward from a short side (54) of the locking
               element (46) and wherein another short side (53) of the locking element (46) is provided
               with a receiving opening (55) for receiving an attaching element (42; 43) of one of
               the inner pipe or outer pipe clampingly therein between the side surfaces (48, 49)
               for attaching the locking element (46) movably in axial direction to an attaching
               element (42; 43), particularly wherein the attaching element (42; 43) forms part of
               a tubular coupling piece (29; 30; 31) of the inner pipe or forms part of a ring element,
               such as a clamping ring, attachable to the outer peripheral wall of the inner pipe
               or a coupling piece.
 
            10. The ventilation and/or flue gas discharge system (10) according to claim 9, wherein
               the receiving opening (55) connects on the other short side (53) of the locking element
               (46) to an open space (56) which is formed between the side surfaces (48, 49) from
               the other long side (52) and which, as seen from the receiving opening (55), diverges
               outward at the end (57) and wherein the attaching element (42; 43) tapers at the end
               (58) in the direction away from the outer peripheral wall (36) of the inner pipe such
               that, when the attaching element (42; 43) is received in the open space (56) of the
               locking element (46) in longitudinal direction from the receiving opening (55), the
               locking element (46) moves radially outward.
 
            11. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, comprising at least two assemblies of a coupled inner pipe (15)
               and outer pipe (14) connected in longitudinal direction, in particular wherein the
               inner pipe (15) comprises inner pipe segments (26, 27, 28) coupled by at least one
               coupling piece (30; 31) and wherein the outer pipe (14) comprises outer pipe segments
               (23, 24, 25) coupled in longitudinal direction, wherein each outer pipe segment (23,
               24, 25) has a smaller diameter at a second end (64) than at a first end (63) thereof
               for the purpose of receiving with the second end (64) an outer pipe segment (25) in
               the first end (63) of another outer pipe segment (24).
 
            12. The ventilation and/or flue gas discharge system (10) according to claim 11, comprising
               a graduation scale (62) running on the outer periphery of an outer pipe segment (25)
               from the second end (64) in the direction of the first end (63).
 
            13. The ventilation and/or flue gas discharge system (10) according to one or more of
               the preceding claims, wherein an outer pipe (23, 24) is provided in its peripheral
               wall, between the position where the at least one locking element (46) or coupling
               element (45) is located and the first end (63) or the second end (64), with at least
               one connecting opening and/or passage opening (69) for connection thereto and/or passage
               therethrough of a branch outer pipe (34) to be connected to the ventilation and/or
               flue gas discharge system (10), particularly wherein a branch outer pipe (34) to be
               connected to the connecting opening (69) on the outer periphery of an outer pipe (23,
               24) engages fluid-tightly on the outer periphery of the outer pipe (23, 24) by means
               of a saddle gasket (66), wherein the saddle gasket (66) has an upright slot-like edge
               for receiving an end of the branch outer pipe (34).
 
            14. An outer pipe segment (23, 24, 25) for a ventilation and/or flue gas discharge system
               (10) as described in one or more of the preceding claims.
 
            15. A locking element (46) for a ventilation and/or flue gas discharge system (10) as
               described in one or more of the preceding claims.