The invention relates to a telescope of the kind intended to accommodate bending moments, and wherein at least one tele¬ scopic member is adapted to be displaced by a hydraulic piston cylinder.

Often, telescopes of the kind indicated have a rectangular cross-section in order to achieve a favourable proportion between weight and resistance against bending in the main direction of the load. Also, through the use of a non- circular cross-section, it is obtained that the telescopic members cannot rotate mutually about the axis thereof. Such telescopes are used e.g. in manipulator arms and lifting equipments, where it is important that the telescope has the ability of accommodating bending moments, contrary to tele¬ scopic lifting cylinders where most importance is attached to the attainment of a large axial force.

A telescope comprises an outer hollow profile, typically in the form of a rectangular pipe surrounding one or more dis¬ placeable telescopic members.

In a telescope comprising one telescopic member, it is easy to dispose a hydraulic cylinder for displacing the telescopic member in the hollow profile surrounding it. A hydraulic piston cylinder can be mounted internally within the tele¬ scope or externally.

In multi-divided telescopes it is difficult to dispose a hydraulic piston cylinder for each telescopic member. One known way to effect this, is to dispose a telescopic hydrau¬ lic cylinder of a type corresponding to the one used in lif¬ ting cylinders. This gives a very heavy and expensive struc¬ ture. Another way is to mount several hydraulic cylinders in series, or to use one single cylinder of sufficient length to cause the telescope to take a position of full length. A dis¬ advantage of this approach is that the smallest length of the telescope increases.

The object of the invention is to provide a simple and rela¬ tively light-weighted telescope adapted to accommodate ben¬ ding forces, and wherein said disadvantages are avoided.

The object is achieved by means of features as defined in the following description and following claims.

The invention is explained by means of a non-restricting examplary embodiment, reference being made to the attached drawings, wherein:

Figure 1 shows in a cross-sectional view, seen from an end, an assembly of a rectangular pipe surrounding two telescopic members designed and shaped as hollow profiles;

Figure 2 shows in a side elevational view, partly in section, a telescope in which the hollow profiles of figure 1 are included;

Figure 3 shows in a side elevational view, partly in section and a in greater scale, a hydraulic piston and a portion of its piston rod;

Figure 4 shows in a side elevational view, partly in section, a portion of a piston rod and a piston rod fastener;

Figure 5 shows a liner for a rectangular telescopic member;

Figure 6 shows a liner for a telescopic member having a smaller rectangular cross-section;

Figure 7 shows an assembly of a rectangular pipe surrounding two telescopic members in a similar way as in figure 1, but where the telescopic members have an alternative cross-sectional shape.

In figure 1, reference numeral 1 denotes an outer pipe having a rectangular cross-section. A hollow profile 2 having an externally rectangular shape constitutes a first telescopic member and is adapted to be displaceable in the pipe 1. The hollow profile 2 has a rectangular barrel 3. A hollow profile 4 having an externally rectangular shape, is adapted to be displaceable in the barrel 3 of the hollow profile 2 and con¬ stitutes a second movable telescopic member.

Further, the hollow profile 2 has a circular barrel 5 and a smaller barrel or channel 6. Correspondingly, the hollow pro¬ file 4 has a rectangular barrel 7 and a circular barrel 8. Advantageously, the hollow profiles 2, 4 may be made as extruded metal profiles, preferably in aluminum.

Further, reference is made to figure 2, showing a telescope as seen in side elevational view, incorporating the pipe 1 and the hollow profiles 2, 4. The telescope is shown substan¬ tially shortened. Figure 2 contains details somewhat diffi¬ cult to see clearly and for these, reference is made to figures 3 and 4 drawn on larger scale.

Between the pipe 1 and the hollow profile 2 a clearance exists, a corresponding clearance existing between the hollow profile 2 and the hollow profile 4. Advantageously, in said clearances, linings 9 , 10 can be mounted, in order to give the hollow profiles 2, 4 a stable, slidable mounting.

A cover 11 having a packer 12 seals the circular barrel 5 at the free end of the hollow profile 2. A similar cover 13 having a packer 14 seals the cylindrical barrel 8 at the free end of the hollow profile 4.

In the cylindrical barrel 5 of the hollow profile 2, a piston 15 is disposed, sealing against the barrel 5 with a packer 16. The piston 15 divides the barrel 5 into an inner chamber 17 and an outer chamber 18. The piston 15 is attached to the outer end of a tubular piston rod 19 extending out through the inner end of the hollow profile 2.

Correspondingly, as in the case of the barrel 5, in the cylindrical barrel 8 of the hollow profile 4, a piston 20 is disposed, sealing against the barrel 8 by means of a packer 21. The piston 20 divides the barrel 8 in an inner chamber 22 and an outer chamber 23. The piston 20 is attached to the outer end of a tubular piston rod 24 extending out through the inner end of the hollow profile 4.

Through the piston 15 and the piston rod 19 is passed a cen¬ tral pipe 25. A packer 26 seals between the piston 15 and the pipe 25. In the piston 15, at the piston rod side, channels 27 are disposed, passing into an annulus 28 between the tubu¬ lar piston rod 19 and the pipe 25. In this way, the piston rod 19 may conduct hydraulic liquid through the annulus 28 and the channels 27 to the chamber 17 and through the pipe 25 to the chamber 18, see figure 3, from where it also appears that the piston 15 is attached to the piston rod 19 by means of complementary screw threads 29 in piston 15 and piston rod 19.

Correspondingly, through the piston 20 and the piston rod 24, a central pipe 30 is inserted, a packer 31 sealing between the piston 20 and the pipe 30. In the piston 20, at the pis¬ ton rod side, channels 32 are disposed, extending into an annulus 33 between the tubular piston rod 24 and the pipe 30. In this way, the piston rod 24 may conduct hydraulic liquid

through the annulus 33 and the channels 32 to the chamber 22 and through the pipe 30 to the chamber 23, see figure 3, from which it also appears that the piston 20 is attached to the piston rod 24 by means of complementary screw threads 34 in piston 20 and piston rod 24.

To the inner end of the piston rod 19 and the pipe 25, is attached a hydraulic coupling 35 of a type known per se. The coupling 35 has a circular cross-section and is adapted to be inserted into a hole in a coupling block 36 in order to, as previously known, to conduct hydraulic liquid between a chan¬ nel 37 in the coupling block 36 and the annulus 28 in the piston rod 19 and between a channel 38 in the coupling block 36 and the pipe 25 in the piston rod 19. The coupling block 36 is attached within the pipe 1 at the inner end thereof, where bores 39, 40 in the wall of the pipe 1 lead inwards to the end of the channels 37, 38 in the coupling block 36. The channels 37, 38 are as previously known coupled to a hydrau¬ lic pressure system, not shown, by means.of couplings, not shown. The coupling 35 is provided with a threaded bolt 41 projecting out through the coupling block 36, so that the coupling 35 can be inserted into and attached to the coupling block 36 with a nut 42. The coupling 35 is provided with two external annular grooves 43 and 44 which, as previously known, are defined laterally by means of three annular packers 45, 46 and 47. The groove 43 is in hydraulic communication with the annulus 28 in the piston rod 19 through channels 48 and

49 in the coupling 35. The groove 44 communicates hydrauli- cally with the pipe 25 in the piston rod 19 through channels

50 in the coupling 35. When the coupling 35 is in position in the coupling block 36, the packers 45, 46, 47 seal against the coupling block 36, and the channels 37, 38 open into the annular grooves 43 and 44 completely defined thereby. The channel 37 communicates, thus, with the chamber 17 at the piston rod side of the piston 15 through the groove 43, the channels 48, 49, the annulus 28 and the channels 27. The channel 38 communicates with the chamber 18 at the opposite side of the piston 15 through the groove 44, the channels 50

and the pipe 25. Reference is made to figure 4 which is drawn on a larger scale, and from where it appears that the piston rod 19 is attached to the coupling 35 with a threaded connec¬ tion, the piston rod 19 and the coupling 35 being provided with complementary threads 51. The threaded connection between the piston rod 19 and the coupling 35 must be pressure-tight, and it is recommended to coat the threads with a sealing agent of a type known prior to mounting. Further, the pipe 25 is also pressure-tightly attached to the coupling 35 by means of a glue of a type known.

To the inner end of the piston rod 24 and the pipe 30 is, in a way corresponding to the piston rod 19, attached a hydrau¬ lic coupling 52 adapted to be inserted into a coupling block 53 and conduct hydraulic liquid between a channel 54 in the coupling block 53 and the annulus 33 in the piston rod 24,and between a channel 55 in the coupling block 53 and the pipe 30 in the piston rod 24. The coupling block 53 is attached with¬ in the hollow profile 2 at the inner end thereof, a portion of the material surrounding the barrel 5, being removed. The coupling block 53 constitutes also an end wall for the cylin¬ drical barrel 5 and is provided with a passage for the piston rod 19. A packer 56 in the coupling block 53 is adapted to seal slidingly against the piston rod 19, and a packer 57 is adapted to seal against the barrel 5. The channel 54 is in hydraulic communication with the chamber 17 in the barrel 5. The channel 55 communicates hydraulically with the chamber 18 in the barrel 5 through the channel 6 in the hollow profile 2, see figure l also, a substantially lateral channel 58 being disposed between the barrel 5 and the channel 6 adjacent the outer end of the barrel 5. The cover 11 seals against the outer end of the channel 6. A packer 59 between the coupling block 53 and the hollow profile 2 secures pressure-tight connection between the channel 6 and the channel 55.

In a similar way as for the coupling 35, the coupling 52 is provided with two external annular grooves 60, 61 laterally defined by three annular packers 62, 63 and 64. The groove

60 communicates hydraulically with the annulus 33 in the piston rod 24 through channels 65 and 66 in the coupling 52. The groove 61 communicates hydraulically with the pipe 30 in the piston rod 24 through channels 67 in the coupling 52. When the coupling 52 is in position in the coupling block 53, the packers 62, 63, 64 seal against the coupling block 53, and the channels 54, 55 open into the grooves 60 and 61 thusly fully defined annularly. Thus, the channel 54 commu¬ nicates with the chamber 22 at the piston rod side of the piston 20 through the groove 60, the channels 65, 66, the annulus 33 and the channels 32. The channel 55 communicates with the chamber 23 at the opposite side of the piston 20 through the groove 61, the channels 67 and the pipe 30. Reference is made to figure 4. The piston rod 24 and the pipe 30 are pressure-tightly fastened to the coupling 52, the pis¬ ton rod 24 and the coupling 52 being provided with mutually complementary threads 68, while the pipe 30 is glued to the coupling 52, as described for the coupling 35. The coupling 52 is provided with a threaded bolt 69 projecting out through the coupling block 53, so that the coupling 52 may be inser¬ ted into and attached to the coupling block 53 with a nut 70.

An end piece 71 for the cylindrical barrel 8 is mounted in the hollow profile 4 at the inner end, some of the material surrounding the barrel 8 being removed. The end piece 71 is provided with a passage for the piston rod 24. A packer 72 is adapted to seal slidingly against the piston rod 24, and a packer 73 is adapted to seal against the barrel 8.

When the telescope is to be extended, hydraulic liquid under pressure is conducted into the channel 38. The liquid is passed through the coupling 35 and the pipe 25 to the chamber 18 where the liquid pressure acts against the piston 15 and the cover 11. Thereby, a force is created seeking to push the hollow profile 2 out from the pipe 1. Simultaneously, liquid is conducted further from the chamber 18 through the channel 58 to the channel 6 in the hollow profile 2 and further to

the channel 55 in the coupling block 53 and from there further through the coupling 52 to the pipe 30 and the chamber 23 in the barrel 8. The pressure in the liquid acts against the piston 20 and the cover 13. Thereby, a force is created seeking to push the hollow profile 4 out from the hollow profile 2.

The telescope is shortened by supplying pressurized hydraulic liquid to the channel 37 in the coupling block 36. The liquid is conducted through the coupling 35 to the annulus 28 and through the channels 27 to the chamber 17 in the barrel 5. Further, the liquid is conducted through the channel 54 in the coupling block 53 to the coupling 52, through the chan¬ nels 65, 66 to the annulus 33 and through the channels 32 to the chamber 22 in the barrel 8. Thereby, a hydraulic force is created seeking to push the hollow profile 2 into the pipe 1 and the hollow profile 4 into the hollow profile 2.

In practice, if the barrel 5 has a small diameter, it may be difficult to position the channel 54 past the packer 57 so that the channel 54 is in communication with the chamber 17. This can be relieved by arranging an extra channel, corres¬ ponding to the channel 6, parallel to the barrel 5, and establish a connection between the chamber 17 and said extra channel, and between the channel 54 in the coupling block 53 and said extra channel.

Hollow profiles for use in telescopes according to the inven¬ tion, may advantageously have a cross-section having a mate¬ rial thickness as equal as possible. Figure 7 shows in sec¬ tion an end view of a preferrred embodiment. In figure 7, reference numeral 81 denotes a rectangular pipe surrounding a hollow profile 82 having a rectangular barrel 83 surrounding a hollow profile 84. The hollow profile 82 has a circular barrel 85 which may be incorporated in a hydraulic piston cylinder and a channel 86 for conducting hydraulic liquid. The hollow profile 84 has a substantially rectangular barrel 87 and a cylindrical barrel 88. Further, in the hollow

profile 82, an extra channel 89 for hydraulic liquid is shown. The channel 89 is used as explained. Between the pipe 81 and the hollow profile 82, linings 90, 91, 92 and 93 are shown at the outer corners of the hollow profile 82. Between the hollow profile 82 and the hollow profile 84, linings 94, 95 are shown externally at the short sides of the hollow profile 84.