GB2075567A - Telescopic mast - Google Patents

Abstract

A mast, such as for a radio antenna, is shown having ten telescopically arranged mast sections 6 to 24. Each mast section is raised and lowered by means of a chain 76 which runs in close confinement within, and raises and lowers, a guide tube 66. This is in turn connected to a selector tube 62 which carries a collar 60. The latter can be angularly turned by means of a handle 74 and through the intermediary of a control tube 68, so as to engage dogs 56 and 58 on the mast section to be raised or lowered. The use of the confined chain enables the mast sections to be positively lowered as well as positively raised. <IMAGE>

Description

SPECIFICATION Telescopic mast The invention relates to masts which can be raised and lowered, and more particularly to telescopic masts such as, for example, for supporting radio antennae.

Various novel features of the invention will be apparent from the following description, given by way of example only, of a telescopic radio antenna mast embodying the invention, reference being made to the accompanying diagrammatic drawings in which: Figure 1 is a diagrammatic side elevation of the mast; Figure 2 is an enlarged view of a vertical crosssection through part of the mast; and Figure 3 is a perspective view, partly broken away, of the internal mechanism of the mast.

More specifically to be described below is a mast comprising a plurality of telescopically arranged mast sections, a flexible elongate member, means confining the member over a part of its path of travel so as to prevent its flexing with respect thereto and thereby enabling it to transmit forces in both directions along its path of travel, and means for selectively linking the flexible member with each of the mast sections whereby movement of the flexible member along its path of travel drives the selected mast section in the same direction.

Advantageously the flexible member is a chain.

In such a case, the means confining the flexible member may comprise a guide tube extending within the mast and parallel with the axial direction thereof and being of such cross-sectional size and shape as to prevent flexing of the chain.

The means for selectively connecting the flexible member to each of the mast sections may comprise a dog clutch.

Preferable, the guide tube is connected to the chain so as to be positively moved in the axial direction of the mast by corresponding movement of the chain, and the means for selectively connecting the flexible member to each of the mast sections comprises a first dog clutch member attached to the guide tube so as to move therewith in the said axial direction, and a respective second dog clutch member on each of the said mast sections, and means enabling the first dog clutch member to be turned angularly with respect to its said axial direction of movement so as to enable it to engage and lock with the second dog clutch member on the selected one of the mast sections, whereby subsequent movement of the chain and guide tube in the said axial direction moves the mast section correspondingly.

In a more specific sense, there will be disclosed a mast, comprising a plurality of telescopically arranged hollow tubular mast sections, a guide tube positioned on the axis of the mast and moveable therealong relative to the mast sections, a chain of which part is confined against flexing within, and is attached to, the guide tube, means for moving the chain along its length in either direction whereby to move the guide tube axially of the mast sections, a first dog clutch member linked with the guide tube so as to move axially therewith but being angularly movable relative to the said axis, a respective second dog clutch member on each of the mast sections adjacent the innermost end thereof, and means for angularly moving the first dog clutch member relative to the said axis so as to enable it to engage any selected one of the second dog clutch members, whereby subsequent movement of the chain causes axial movement of the mast section associated with the selected second dog clutch member.

Advantageously, means are provided for locking each mast section in its axial position relative to the other mast section.

The foregoing are exemplary of and not exhaustive of the various features of the mast now to be more specifically described with reference to the drawings.

As shown in Figure 1 , the mast comprises ten (in this example) telescopically arranged hollow tubular sections 6 to 24. As shown in Figure 1, the largest section 6 is fixed to a base 25 which is articulated, by means of a joint 26 shown diagrammatically, on a platform 28 resting on the ground. Stays, of which two, referenced 30 and 32, are shown, support the section 6 vertically.

In the particular example being described, a radio antenna (not shown) is supported on the top of the uppermost mast section 24. However, the mast is not limited to such use and may be used for other purposes.

Figure 1 shows the mast with the sections 8 to 22 in their lowered positions and with the section 24 partially raised. The upper end of each of the sections, except the uppermost section 24, carries a clamp by means of which it can be locked (for example, frictionally locked) to the next smaller section. Each of these clamps may take any suitable form, for example the form shown in our co-pending British Patent Application No. 50640/76. The clamps are not illustrated in detail in the Figures but each clamp is manually operable by means of a respective handle 34.

In operation, and in a manner to be described in detail below, the mast is raised by initially releasing all the clamps, and then raising the mast section 24 to its fullest extent. After the clamp on the upper end of the mast section 22 has been closed, so as frictionally to grip the lower end of the raised mast section 24, the mast section 22 is then raised to its fullest extent. After closing the clamp at the upper end of the mast section 20, so as to lock that mast section to the lower end of the raised mast section 22, mast section 20 can be raised; and so on, in turn, for all the remaining sections, except section 6, until finally the mast is fully extended. The manner in which the mast sections are raised will be explained below.

It is not necessary for the mast sections to be raised separately. For example, one or more of the clamps may initially be in the closed position so that two or more of the mast sections are raised together; but in this case of course the mast will not be raised to its fullest extent.

Figures 2 and 3 explain the construction and operation of the mast in greater detail.

As shown, each mast section terminates in a respective annulus 36 to 54. The inner circumference of each annulus, except the annulus 36 of the mast section 6, has two inwardly projecting dogs 56 and 58. These are shown more clearly in Figure 3 for the annulus 54 at the bottom of the smallest mast section 24. The dogs 56 and 58 can be engaged by mating portions of a collar 60 which is rigid with a selector tube 62.

Tube 62 runs vertically upwards within the mast sections and has a closed end 64 which is fixed to the top of a guide tube 66 which has a hollow square or rectangular cross-section for a purpose to be described. A control tube 68 is positioned between the selector tube 62 and the guide tube 66 and has a key 70 engaging a vertical keyway running substantially the whole length of the selector tube 62. Therefore, the- control tube 68 is locked against rotation relative to the selector tube 62, but the two can move vertically with respect to each other. At its lower end, the control tube 68 terminates in a ring 72 to which is attached a handle 74 projecting outwardly through an open arcuate slot in the base 25.

By means of the handle 74, therefore, an operator can turn the control tube 68 about the vertical axis through the mast, and, through the intermediary of the key 70 and its keyway, this turns the selector tube 62 and thus the collar 60.

A chain 76 runs around a sprocket 78 rotatably supported in a housing 80 attached to the base 25 (Fig. 1) and extends upwardly within the guide tube 66. A rod 82 is attached to the uppermost link 76A of the chain and also to the closed end 64 of tube 62. As shown, the links of the chain are a relatively tight fit within the guide tube 66. The other end of the chain 76 leads into a hopper 84 (Fig. 1).

The sprocket 78 can be rotated by means of an operator's handle 85 and gearing (not shown) within a gearbox 86 (Fig. 1).

Figure 3 shows the formation of the collar 60 in more detail.

As shown, the collar 60 comprises upper and lower ring portions 90 and 92 which are each in the form of dogs interrupted by gaps of sufficient size to allow the dogs 56 and 58 to pass through with clearance.

In operation, when a particular mast section, mast section 24 for example, is to be raised, the operator operates the handle 85 (Fig. 1) so as to turn the sprocket 78 in an anti-clockwise direction (as viewed in Fig. 2) and thus to displace the chain 76 into the hopper 84. This therefore pulls -downwardly on the rod 82 and therefore lowers the tubes 62 and 66.

At the same time, the operator turns the handle 74 thereby turning the control tube 68 and thus the selector tube 62. The operator turns the handle 74 by an appropriate amount so that, as the collar 60 is lowered with the tube62, the dog 58 passes through the gap 90A (Fig. 3) in the collar, and the dog 56 passes through a corresponding gap (not shown) in a diametrically opposite position on the collar. The dog 58 will therefore abut the dog 92A (and dog 56 will abut a corresponding dog at a diametrically opposite position on the collar). The operator then turns the handle 74 slightly so as to turn the collar 60 until the dog 58 is in the position shown dotted at "X" in Fig. 3, that is, between the dog 92A of the upper ring portion 92 and a dog 90B of the lower ring portion 90.This will also position the dog 56 between corresponding dogs on the other side of the collar.

The operator then operates the handle 85 so as to turn the sprocket 78 in a clockwise direction and the chain 76 is thereby displaced upwardly within the mast. Because the chain links are confined relatively tightly within the guide tube 66, this displacement of the chain 76 will lift the guide tube 66, and thereby lift the selector tube 62. The positions of the dogs 56 and 58 within the collar 60 lock the collar 60, and therefore the selector tube 62, against vertical movement relative to the mast section 24, which is therefore raised by the upward movement of the chain.

When the mast section 24 has reached its uppermost position, the clamp on the upper end of the mast section 22 is closed so as to lock that upper end to the lower end of the raised mast section 24.

The operator then turns the handle 74 in an anti-clockwise direction (as viewed in Figure 3) so as to position the dog 58 in alignment with the gap 92B in the ring portion 92, and to position the dog 56 in alignment with a corresponding gap on the other side of the collar.

He then operates the handle 85 so as to turn the sprocket 78 in an anti-clockwise direction and to displace the chain into the hopper 84. The chain therefore pulls the guide tube 66 downwardly and thus also the selector tube 62, with the dogs 56 and 58 therefore passing through the gaps in the ring portion 92 with which they are in alignment.

In this way, the collar 60 is brought towards the annulus 52 (Fig. 2) at the bottom end of the next mast section 22. By means of appropriate operation of the handles 74 and 85, the operator can turn and lower the collar 60 until the dogs 56 and 58 on the annular 52 become located in positions corresponding to position "X" in Fig. 3.

Mast section 22 can then be raised by operation of the handle 85 to raise the chain vertically within the mast. The other mast sections are raised similarly.

The arrangement is advantageous because the use of a chain running in close-fitting relationship with a guide tube (as opposed, for example, to a flexible wire) enables the mast sections to be both raised and lowered positively; that is, the system does not rely on gravity for lowering the mast sections. This is important because adverse weather conditions, particularly freezing conditions, can prevent or retard the lowering of mast sections under the influence of gravity and there may be many applications, particularly military applications, where the ability to lower the mast rapidly is very important.

At the same time, of course, the use of a chain is advantageous because its flexibility simplifies the mechanical construction considerably, as compared for example with a system of rods and levers.

The raising and lowering operations, and the angular turning of the selector tube may be motorised.

The mast sections 6 to 24 need not be of circular cross-section. It may be advantageous for them to be of some other cross-sectional shape ("D" section, for example) to prevent them turning with respect to each other because such turning would undesirably turn the radio antenna. In such a case of course, means could be provided to enable the mast sections, and thus the antenna, to be turned deliberately by specific amounts.

Although the description above has referred to the use of the mast for supporting a radio antenna, this is merely by way of example and the mast may be used for any other suitable purpose instead.

Claims (9)

1. A mast, comprising a plurality of telescopically arranged mast sections, a flexible elongate member, means confining the member over a part of its path of travel so as to prevent its flexing with respect thereto and thereby enabling it to transmit forces in both directions along its path of travel, and means for selectively linking the flexible member with each of the mast sections whereby movement of the flexible member along its path of travel drives the selected mast section in the same direction.

2. A mast according to claim 1, in which the flexible member is a chain.

3. A mast according to claim 2, in which the means confining the flexible member comprises a guide tube extending within the mast and parallel with the axial direction thereof and being of such cross-sectional size and shape as to prevent flexing of the chain.

4. A mast according to any preceding claim, in which the means for selectively connecting the flexible member to each of the mast sections comprises a dog clutch.

5. A mast according to claim 3, in which the guide tube is connected to the chain so as to be positively moved in the axial direction of the mast by corresponding movement of the chain, and the means for selectively connecting the flexible member to each of the mast sections comprises a first dog clutch member attached to the guide tube so as to move therewith in the said axial direction, and a respective second dog clutch member on each of the said mast sections, and means enabling the first dog clutch member to be turned angularly with respect to its said axial direction of movement so as to enable it to engage and lock with the second dog clutch member on the selected one of the mast sections, whereby subsequent movement of the chain and guide tube in the said axial direction moves the mast section correspondingly.

6. A mast, comprising a plurality of telescopically arranged hollow tubular mast sections, a guide tube positioned on the axis of the mast and moveable therealong relative to the mast sections, a chain of which part is confined against flexing within, and is attached to, the guide tube, means for moving the chain along its length in either direction whereby to move the guide tube axially of the mast sections, a first dog clutch member linked with the guide tube so as to move axially therewith but being angularly moveable relative to the said axis, a respective second dog clutch member on each of the mast sections adjacent the innermost end thereof, and means for angularly moving the first dog clutch member relative to the said axis so as to enable it to engage any selected one of the second dog clutch members, whereby subsequent movement of the chain causes axial movement of the mast section associated with the selected second dog clutch member.

7. A mast according to claim 8, including means for locking each mast section in its axial - position relative to the other mast section.

8. A mast substantially as described with reference to the accompanying drawings.

9. A mast according to any preceding claim, supporting a radio antenna.