EXTENDABLE STRUCTURE

Description

Field of the Invention

[0001] The present invention relates to an extendable structure or pole. Such a pole may be used as a mast, for example to support lighting units for temporary external lighting applications or may be used for other purposes where an elongate tool or support is required to be compactable for example for transport or storage.

Background to the Invention

[0002] There is a need in this field of technology for an extendable pole which is strong, yet compact and light so that it can be transported easily and with the minimum of fuel use. It should also be easy to extend and must be stable and any rotation when in use should be controllable, particularly when used as a mast to support equipment such as lighting which is directional.

[0003] Known extendable poles use a series of telescopically interconnected coaxial hollow tubular sections. The telescopic construction means that the unextended pole occupies relatively little space and can be moved and transported relatively easily. The tubes are typically made of square or multi-faceted construction to prevent them turning relative to each other in use. Such an extendable structure according to the preamble of claim 1 is known from US 5 615 855 A.

[0004] They may be extended and retracted mechanically. Hydraulic operation is also known such that when fluid is pumped into the sections under pressure, the tubes slide past each other to extend the length of the pole (or the height of the mast). However in known hydraulic versions the hydraulic fluid is pumped into separate internal hydraulic cylinders to avoid the problems of sealing multi-faceted structures.

Summary of the Invention

[0005] According to the present invention there is provided an extendable structure comprising a plurality of coaxially arranged telescopic elongate hollow segments, wherein each segment comprises: an elongate tube; a base arranged at one end of the tube; a gland arranged at the other end of the tube; and an elongate bar having one end fixed to the base and another opposite end fixed to the gland, and being positioned inside the tube, so that each bar is located between two adjacent tubes, and wherein a groove is located in the circumference of the base so that when the segments are moved in a telescopic manner each base slides along the bar of the outwardly adjacent segment.

[0006] This arrangement provides that each section is effectively interlocked to adjacent sections to stop rotation of the sections relative to each other. Any number of sections may be used to suit the application.

[0007] Preferably two bars are provided for each segment, arranged diametrically opposite each other relative to the tube. The bars are preferably generally planar and have a small width relative to the diameter of the tube. They may have chamfered ends for ease of assembly and they are held in place in the pole segment in slots provided in the base at one end and in the gland at the other end. The tube is preferably fixed to the base and to the gland by screws so that the segment can be easily dismantled for servicing and repair, but the parts could be fixed together by other means such as riveting or welding or gluing.

[0008] The tube is preferably of circular cross section. This is relatively easy to machine or mould to a high tolerance and easier to seal. The resulting structure is also less resistant to wind.

[0009] Seals are preferably provided for each segment to restrict, and preferably prevent, leakage of hydraulic fluid out of each segment. The seals may take the form of pressure seals, excluder seals and o-rings and are arranged between each tube and its respective base and gland, as well as between adjacent segments.

[0010] The gland is preferably formed of two parts for ease of assembly and servicing. A first gland part, which normally forms the upper part of the gland when the pole is vertical, has an outer diameter larger than the diameter of the tube so that when the mast is contracted and the tubes are telescopically parked the first gland parts rest close to or adjacent each other. The tube fits in a circular trench in the first part of the gland and is fastened by radially oriented screws around the outer circumference of the first gland part. A U-shaped pressure seal seats in a recess at the top of the first gland part to seal against an adjacent inside tube to prevent leakage of hydraulic fluid from the top of the first gland part. It has one arm of the U abutting the tube and the open side of the U facing the space between the adjacent tubes, i.e. toward the hydraulic fluid in the tubes in use. This pressure seal is supplemented by a circular excluder seal in a second recess in the first gland part, which acts as a wiper seal. Alternatively a one-piece combined seal may be used.

[0011] The present invention can provide for a compact, lightweight extendable mast which is easy to transport and erect, is stable in use and in which the sections do not rotate relative to each other so that the direction of orientation along the length of the pole can be controlled from one end.

Description of Drawings

[0012] The present invention will now be described by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side view of the pole of the invention in a non-extended form; figure 1a shows the top of the pole in more detail and figure 1b shows the bottom of the pole in more detail;

Figure 2 is a cut-away view of figure 1; figure 2a is an enlarged view of the top and figure 2b an enlarged view of the bottom of the pole;

Figure 3 is a view of the pole of the invention in an extended form;

Figure 4 us a cross-sectional view of the pole of figure 3;

Figure 5 is an enlarged view of the top of the pole of figure 4;

Figure 6 is an enlarged view of a connection between two segments of the pole of figure 4;

Figure 7 is an enlarged view of the bottom of the pole of figure 4;

Figures 8a1, 8a2, 8b, 8c and 8d show a base of an outermost segment of the pole of the invention in more detail;

Figures 9a, 9b, 9c and 9d show a part of a gland of a segment of the pole in more detail;

Figures 10a, 10b, 10c, 10d, 10e and 10f show another part of the gland of a segment of the pole in more detail;

Figure 11a is a plan view of a bar of a segment of the pole and Figure 11b is an end view of the bar of Figure 11a.

Figures 12a, 12b, 12c and 12e show a base of an internal segment of the pole in more detail.

[0013] The telescopic pole 1 is shown in Figures 1 and 2 in a contracted, non-extended state and in figures 3 and 4 in an extended state. The pole 100 comprises a plurality of coaxial tubes 1 through 7 of circular cross section and declining diameter. In this example there are seven tubes but any number can be used. The innermost tube 7 has a top mounted platform 33 at one end and a base 14 at the other end. Items such as lights can be attached to the platform 33, depending upon the application for which the pole is being used.

[0014] Each of the other tubes 1 through 6 have a base 8 to 13 respectively at the lower end and a two part gland at the top end. Each gland comprises a gland top 15 through 20 and a gland bottom 21 to 25 respectively. Each of the tubes 1 through 6 also has two flat bars 27 to 32 respectively arranged diametrically opposite each other inside and parallel to the respective tube 1 to 6. Each flat bar is anchored at one end in the respective base 8 through 13 and is anchored at the other end in the respective gland bottom 21 to 25. Each tube, gland, base and pair of bars forms a segment of the pole 100 and each segment is able to slide inside the next adjacent segment.

[0015] Figure 1a is an enlarged view of part of Figure 1 showing the external construction of the upper part of the pole 100 in more detail. The outermost tube 1 is shown with the respective gland top 15 which is fixedly attached to the tube 1 by a series of hex head screws 37. An excluder seal 50 around the upper circumference of the gland top 15 seals against the next adjacent tube 2. Tube 2 is fixed to its respective gland top 16, again by hex head screws 37 and is sealed against the next adjacent tube 3 by an excluder seal 48. This arrangement is repeated for tubes 3 through 6 with respective gland tops 17 through 20 and excluder seals 46, 44, 42 and 40. Seal 40 seals gland top 20 against the innermost tube 7 to which the platform 33 is attached on one side with a hex head bolt 60 and a bright metal washer 61, and on the other side by a hex nut with torque part 62 and a bright metal washer 61.

[0016] Figure 2a shows the upper part of the pole 100 in cut away form and illustrates an arrangement of bars within the tubes as well as showing more detail of the seals between the gland tops and the tubes.

[0017] It can be seen that each tube 1 through 6 fits into a circumferential recess in the respective gland top 15 through 20 and is fixed in place by the hex head screws 37. This is shown in more detail in Figure 9 where the recess is referenced 151 and the hole for the screw 57 is shown as 152. Quadrings 51 through 56 and orings 57 to 59 seal each gland top to its respective tube.

[0018] Each excluder seal 50, 48, 46, 44, 42 and 40 sits in an upper recess (153 in Figure 9) in the respective gland top 15 through 20 and an additional circumferential U-shaped pressure seal 49, 47, 45, 43, 41 is shown in a second circumferential recess (154 in Figure 9) of the respective gland top.

[0019] The lower circumference of each gland top 15 through 20 fits with the upper edge of a respective gland bottom 21 to 26 (shown in more detail in Figures 10) and an upper end of a flat bar 27 through 32 is connected to the lower edge of each gland bottom 21 to 26 at each side of the respective tube.

[0020] The arrangement at the lower end of the pole 100 is shown in Figures 1b and 2b. The flat bars 27 through 32 are anchored at their bottom end in respective bases 8 through 13 which are also connected to the bottom ends of their respective tubes 1 through 6. Tube 1 is connected to its base 8 by hex head screw 36 and tubes 2 to 6 are connected to their bases by slotted dog screws 38 (figure 1b). The innermost tube 7 is connected to its base 14 by a slotted dog screw 38 but does not have the additional flat bars of the other tubes. A plug 34 for the innermost tube 7 has a first o-ring seal 58 around its circumferential edge which seals against the inside surface of the tube 7, and a second o-ring seal 57 in its bottom surface to seal against the base 14 of the innermost tube 7. Circumferential o-ring seals seated in the bases seal against the inside surface of the tubes as shown for base 8 and tube 1 where the o-ring seal is referenced 59.

[0021] A mast rotation stop 35 comprising a peg in the lowermost base 8 is used to engage in a track on a mounting for the mast (not shown) and stops the mast rotating as a whole in use.

[0022] Each base 8 through 14 has a channel 120 formed in its centre for receiving hydraulic fluid into the tubes. The fluid may be any suitable fluid and can preferably be water since this is easily available, inexpensive and environmentally friendly and safe in the case of spillage or leakage. The water is pumped into the channel 120 into the innermost tube 7 and the action of the pressure against the platform 33 pushes the platform 33 and the innermost tube 7 in a longitudinal direction - for example upwards in the case where the pole is used as a vertical mast. The innermost tube slides along the inside of the flat bars 32 of the adjacent tube 6 until the tube 7 is fully extended and the base 14 of the innermost tube 7 contacts the gland bottom 26 for tube 6. This prevents further extension of tube 7 and as more hydraulic fluid is pumped into the channel 120 then tube 6 moves upwardly sliding past the flat bars 31 for tube 5 until it is fully extended and so on until the pole is extended to the required height or is fully extended as shown in figures 3 and 4.

[0023] Figure 4 is a cross section of the extended pipe 100 of Figure 3. Figures 5, 6 and 7 are enlarged views of the areas marked B. C and D in Figure 4 and like parts are referenced with like numbers.

[0024] The construction of the base 8 for outermost tube 1 is shown more clearly in figures 8 in which figure 8a1 is a bottom perspective view, figure 8a2 is a top perspective view, figure 8b is a side view, figure 8c is a side cross sectional view, figure 8d is a plan cross sectional view and figure 8e is an enlarged cross section of part B of figure 8c.

[0025] The fluid channel 120 passes through the middle of the base 8 and there is a protruding circumferential ledge 81 around the bottom against which the tube 1 abuts. There are radial holes 82 for receipt of the screws 38 which hold the tube 1 to the base 8. Adjacent the screw holes 82 is a circumferential recess 83 for receipt of the oring seal 59 to seal against the bottom of the tube 1. Two slots 80 are formed in the base at diametrically opposed positions for receipt of the bottom ends of the bars 27. The top ends of the flat bars 27 are located in two slots 101 in the lower circumference of the gland bottom shown in figures 9.

[0026] The base 9 for the adjacent inner tube 2 is shown more clearly in figures 12 in which figure 12a is a solid perspective view, figure 12b is a side view, figure 12c is a side cross sectional view, figure 12d is a plan view and figure 12e is a side view in a perpendicular direction compared to figure 12b. This base 9 is similar to the base 8 but has two cut-out grooves in the outer lip 81 aligned with the slots 80. These cut-out grooves locate the bars 27 of the outwardly adjacent tube 1 so that the tube 9 can slide longitudinally along the bars and is prevented from rotating.

[0027] Each of the tubes 3 to 6 have bases of the same general construction as base 9. The base 14 for the innermost tube 7 is also similar but does not have the grooves 80 since it does not need to accommodate bars within the innermost tube 7.

[0028] Figure 9a is a perspective solid view from the top of the gland bottom 21 for tube 1, figure 9b is a side view, figure 9c is a cross sectional view of figure 9b and figure 9d is an end view. The top circumference 91 of the gland bottom 21 is stepped in its longitudinal profile and the steps are referenced 92. This stepped shape corresponds to a complimentary stepped profile on the lower surface of the gland top 15 and enables a hard joint to be formed between the two parts of the gland. The gland top 15 is shown in more detail in figures 10.

[0029] Figure 10a is a perspective solid view from the bottom of the gland top 15, figure 10b is a side view, figure 10c is a cross section of figure 10b, figure 10d is a bottom view and figures 10e and 10f are enlarged views of the parts of figure 10c labelled E and F respectively.

[0030] The gland top 15 has a longitudinally extending circumferential recess 151 for receipt of the tube 1 which is held in place by the screws 37 in the holes 152. The figures also show the circumferential recess 151 in which is located the o-ring seal 59 to seal outwardly against the tube 1 and two further recesses 153 and 154 in which are located seals to seal inwardly against the adjacent tube 2. The diametrically located steps 160 engage with the corresponding steps 92 in the lower gland 21.

[0031] The construction of the gland is particularly advantageous in that all the seals are located in the gland top so that they can be easily removed and replaced for example when worn or for regular servicing. The use of tubes with a circular cross section makes the tubes cheaper to make and makes them easier to seal effectively with standard sealing techniques.

[0032] Figure 11 shows the shape of one of the bars 27 which has chamfered ends 130 for ease of assembly of the bars into the slots 101 in the lower gland 21 at one end and in the slots 80 in the base 8 at the other end.

[0033] The tubes and bars are preferably made of stainless steel but can also be made of any material suitable to the application, for example, aluminium or carbon fibre depending upon strength and weight requirements.

[0034] The interaction of the tubes with the glands and the bars forms an internal mechanical interlocking device between each adjacent pair of tubes which effectively interlocks all of the sections against rotation relative to each other.

Claims

1. An extendable structure (100) comprising a plurality of coaxially arranged telescopic elongate hollow segments (38), wherein each segment comprises: an elongate tube (1); a base (8) arranged at one end of the tube; a gland (40,42) arranged at the other end of the tube; characterized in that it further comprises an elongate bar (7) having one end fixed to the base and another opposite end fixed to the gland, and being positioned inside the tube, so that each bar is located between two adjacent tubes, and wherein a groove (83) is located in the circumference of the base so that when the segments are moved in a telescopic manner each base slides along the bar of the outwardly adjacent segment.

2. An extendable structure (100) according to claim 1 wherein each segment (38) comprises two bars (27-32) arranged diametrically opposite each other relative to the tube (1).

3. An extendable structure (100) according to claim 1 or 2 wherein the bars (27-32) are generally planar.

4. An extendable structure (100) according to claim 1, 2 or 3 wherein the bars (27-32) have a small width relative to the diameter of the tube (1).

5. An extendable structure (100) according to any one of the preceding claims wherein the bars (27-32) have chamfered ends.

6. An extendable structure (100) according to any one of the preceding claims wherein the bars (27-32) are held in place in the segment in slots (80) provided in the base at one end and in the gland at the other end.

7. An extendable structure (100) according to any one of the preceding claims wherein the tube is fixed to the base and to the gland by screws, or by riveting or by welding or by gluing.

8. An extendable structure (100) according to any one of the preceding claims wherein the tube is of circular cross section.

9. An extendable structure (100) according to any one of the preceding claims comprising seals (59) arranged between each tube and its respective base and gland to restrict leakage of hydraulic fluid out of each segment.

10. An extendable structure (100) according to any one of the preceding claims comprising seals (59) arranged between adjacent segments.

11. An extendable structure (100) according to claim 9 or 10 comprising pressure seals, or excluder seals, or o-ring seals.

12. An extendable structure (100) according to any one of the preceding claims wherein the gland is formed of two parts, and comprises a first gland part, which normally forms the upper part of the gland (15) when the structure is vertical, having an outer diameter larger than the diameter of the tube so that when the mast is contracted and the tubes are telescopically parked the first gland parts rest close to or adjacent each other.

13. An extendable structure (100) according to claim 13 comprising a circular trench formed in the first part of the gland to accommodate the tube, or wherein the tube is fastened by radially oriented screws (38) around the outer circumference of the first gland part.

14. An extendable structure (100) according to claim 12 or 13 comprising a U-shaped pressure seal (59) seated in a recess at the top of the first gland part to seal against an adjacent inside tube to prevent leakage of hydraulic fluid from the top of the first gland part, wherein one arm of the U-shaped seal is arranged to abut the tube and the open side of the U faces the space between the adjacent tubes.

15. An extendable structure (100) according to claim 14 wherein the pressure seal (59) is supplemented by a circular excluder seal (59) seated in a second recess in the first gland part, arranged to act as a wiper seal.

Ansprüche

1. Verlängerbare Struktur (100), umfassend mehrere koaxial angeordnete, teleskopische, langgestreckte, hohle Segmente (38), wobei die Segmente jeweils Folgendes umfassen: eine langgestreckte Röhre (1), einen an einem Ende der Röhre angeordneten Fuß (8); eine am anderen Ende der Röhre angeordnete Stopfbüchse (40, 42); dadurch gekennzeichnet, dass sie weiter eine langgestreckte Stange (7) umfasst, deren eines Ende an dem Fuß fixiert ist und ein anderes gegenüberliegendes Ende an der Stopfbüchse fixiert ist und die in der Röhre positioniert ist, so dass sich die Stangen jeweils zwischen zwei benachbarten Röhren befinden und wobei sich in dem Umfang des Fußes eine Rille (83) befindet, so dass, wenn die Segmente auf teleskopische Weise bewegt werden, die Füße jeweils an der Stange des nach außen benachbarten Segments entlang gleiten.

2. Verlängerbare Struktur (100) nach Anspruch 1, wobei die Segmente (38) jeweils zwei Stangen (27-32) umfassen, die relativ zu der Röhre (1) einander diametral gegenüber liegend angeordnet sind.

3. Verlängerbare Struktur (100) nach Anspruch 1 oder 2, wobei die Stangen (27-32) allgemein ebenflächig sind.

4. Verlängerbare Struktur (100) nach Anspruch 1, 2 oder 3, wobei die Stangen (27-32) relativ zu dem Durchmesser der Röhre (1) eine kleine Breite aufweisen.

5. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, wobei die Stangen (27-32) abgeschrägte Enden aufweisen.

6. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, wobei die Stangen (27-32) in Schlitzen (80) in dem Segment festgehalten werden, die an einem Ende in dem Fuß und am anderen Ende in der Stopfbüchse vorgesehen sind.

7. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, wobei die Röhre durch Schrauben oder durch Nieten oder durch Schweißen oder durch Kleben an dem Fuß und an der Stopfbüchse fixiert ist.

8. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, wobei die Röhre einen kreisförmigen Querschnitt aufweist.

9. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, umfassend Dichtungen (59), die zwischen jeder Röhre und ihrem jeweiligen Fuß und ihrer jeweiligen Stopfbüchse angeordnet sind, um das Auslaufen von Hydraulikfluid aus jedem Segment einzuschränken.

10. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, umfassend Dichtungen (59), die zwischen benachbarten Segmenten angeordnet sind.

11. Verlängerbare Struktur (100) nach Anspruch 9 oder 10, umfassend Druckdichtungen oder Verschlussdichtungen oder O-Ring-Dichtungen.

12. Verlängerbare Struktur (100) nach einem der vorangehenden Ansprüche, wobei die Stopfbüchse aus zwei Teilen gebildet ist und ein erstes Stopfbüchsenteil umfasst, das normalerweise den oberen Teil der Stopfbüchse (15) bildet, wenn die Struktur vertikal ist, und einen Außendurchmesser aufweist, der größer ist als der Durchmesser der Röhre, so dass, wenn der Mast eingefahren ist und die Röhren teleskopisch geparkt sind, die ersten Stopfbüchsenteile nah beieinander oder aneinander angrenzend liegen.

13. Verlängerbare Struktur (100) nach Anspruch 13 [sic], umfassend eine in dem ersten Teil der Stopfbüchse gebildete kreisförmige Furche zum Aufnehmen der Röhre oder wobei die Röhre durch radial orientierte Schrauben (38) um den äußeren Umfang des ersten Stopfbüchsenteils herum befestigt ist.

14. Verlängerbare Struktur (100) nach Anspruch 12 oder 13, umfassend eine U-förmige Druckdichtung (59), die in einer Aussparung oben an dem ersten Stopfbüchsenteil sitzt, um gegen eine benachbarte innere Röhre zu dichten, um das Auslaufen von Hydraulikfluid oben aus dem ersten Stopfbüchsenteil zu verhindern, wobei ein Arm der U-förmigen Dichtung dazu angeordnet ist, an die Röhre zu stoßen und die offene Seite des U dem Zwischenraum zwischen den benachbarten Röhren zugewandt ist.

15. Verlängerbare Struktur (100) nach Anspruch 14, wobei die Druckdichtung (59) durch eine kreisförmige Verschlussdichtung (59) ergänzt wird, die in einer zweiten Aussparung in dem ersten Stopfbüchsenteil sitzt und dazu angeordnet ist, als Abstreifdichtung zu wirken.

Revendications

1. Structure extensible (100) comportant une pluralité de segments creux allongés télescopiques arrangés de manière coaxiale (38), dans laquelle chaque segment comporte : un tube allongé (1) ; une base (8) arrangée au niveau d'une extrémité du tube ; un fouloir (40, 42) arrangé au niveau de l'autre extrémité du tube ; caractérisée en ce qu'elle comporte par ailleurs une barre allongée (7) ayant une extrémité fixée à la base et une autre extrémité opposée fixée au fouloir, et étant positionnée à l'intérieur du tube, de sorte que chaque barre est située entre deux tubes adjacents, et dans laquelle une rainure (83) est située dans la circonférence de la base de sorte que, quand les segments sont déplacés de manière télescopique, chaque base coulisse le long de la barre du segment adjacent vers l'extérieur.

2. Structure extensible (100) selon la revendication 1, dans laquelle chaque segment (38) comporte deux barres (27 - 32) arrangées chacune de manière diamétralement opposée par rapport au tube (1).

3. Structure extensible (100) selon la revendication 1 ou la revendication 2, dans laquelle les barres (27 - 32) sont généralement planes.

4. Structure extensible (100) selon la revendication 1, la revendication 2 ou la revendication 3, dans laquelle les barres (27 - 32) ont une petite largeur par rapport au diamètre du tube (1).

5. Structure extensible (100) selon l'une quelconque des revendications précédentes, dans laquelle les barres (27 - 32) ont des extrémités chanfreinées.

6. Structure extensible (100) selon l'une quelconque des revendications précédentes, dans laquelle les barres (27 - 32) sont maintenues en place dans les segments dans des fentes (80) mises en oeuvre dans la base au niveau d'une extrémité et dans le fouloir au niveau de l'autre extrémité.

7. Structure extensible (100) selon l'une quelconque des revendications précédentes, dans laquelle le tube est fixé à la base et au fouloir par des vis, ou par rivetage ou par soudage ou par collage.

8. Structure extensible (100) selon l'une quelconque des revendications précédentes, dans laquelle le tube présente une coupe transversale circulaire.

9. Structure extensible (100) selon l'une quelconque des revendications précédentes, comportant des joints (59) arrangés entre chaque tube et sa base et son fouloir respectifs pour limiter toute fuite de fluide hydraulique hors de chaque segment.

10. Structure extensible (100) selon l'une quelconque des revendications précédentes, comportant des joints (59) arrangés entre des segments adjacents.

11. Structure extensible (100) selon la revendication 9 ou la revendication 10, comportant des joints sous pression, ou des joints d'exclusion, ou des joints toriques.

12. Structure extensible (100) selon l'une quelconque des revendications précédentes, dans laquelle le fouloir est formé de deux parties, et comporte une première partie de fouloir, qui constitue normalement la partie supérieure du fouloir (15) quand la structure est verticale, ayant un diamètre extérieur supérieur au diamètre du tube de sorte que, quand le mât est contracté et quand les tubes sont immobilisés de manière télescopique, les premières parties de fouloir viennent prendre appui à proximité ou de manière adjacente les unes par rapport aux autres.

13. Structure extensible (100) selon la revendication 13 [sic], comportant une tranchée circulaire formée dans la première partie du fouloir pour recevoir le tube, ou dans laquelle le tube est attaché par des vis orientées dans le sens radial (38) autour de la circonférence extérieure de la première partie de fouloir.

14. Structure extensible (100) selon la revendication 12 ou la revendication 13, comportant un joint sous pression en U (59) situé dans un évidement au niveau de la partie supérieure de la première partie de fouloir à des fins d'étanchéité contre un tube intérieur adjacent pour empêcher toute fuite de fluide hydraulique depuis la partie supérieure de la première partie de fouloir, dans laquelle un bras du joint en U est arrangé pour venir en butée contre le tube et le côté ouvert du U fait face à l'espace entre les tubes adjacents.

15. Structure extensible (100) selon la revendication 14, dans laquelle le joint sous pression (59) est complété par un joint d'exclusion circulaire (59) situé dans un second évidement dans la première partie de fouloir, arrangé pour tenir lieu de joint racleur.

Drawing