GB2055481A - Staying system for a mast - Google Patents

Abstract

This invention relates to the control and adjustment of the tension in stays used for locating tall structures such as radio masts. A tension sensing device 15 is connected between a stay cable 12 and an anchor 13. The device includes a piston/cylinder unit which acts on a crosshead to which the cable 12 is attached. The crosshead is slidably mounted on a chassis which acts together with it as the normal tension connection between the cable 12 and anchor 13. The sliding movement available to the crosshead provides sufficient lost motion to enable the piston/cylinder unit to take over the tensile force. The pressure in the piston/cylinder unit gives an indication of the tensile force in the cable 12. Modifications of the device 15 are described, which are additionally capable of tensioning the cable 12. <IMAGE>

Description

SPECIFICATION Staying system for a mast This invention relates to the control and adjustment of the tension in stays used for locating tall structures such as radio masts.

Such staying systems require to be carefully adjusted to locate the structure initially in the required vertical attitude or subsequently to correct any out of balance in the tension forces in the system. For this purpose each stay may be provided with a tensioning device usually adjacent its lower end where it is connected to a fixed anchorage. By use of survey instruments such as theodolites, it is possible to gauge when the mast is vertical and to adjust the different stays until this is achieved. However, it is also important that the tension in each individual stay should be gauged: even if the mast is properly positioned there may be considerable imbalance in the tension forces in the stays. Accordingly, it is an object of the invention to provide an improved staying system which will allow the tension forces to be gauged and controlled.

Broadly stated the invention comprises a staying system for a mast or other structure, comprising a plurality of tension stays extending from the structure to respective spaced anchorages, means for adjusting the effective length of a stay, detachable means for sensing the tension in the stay, including a fluid piston and cylinder assembly, means for attaching the two assembly components respectively to adjacent portions of the stay, means for pressuring the cylinder and sensing the pressure therein, and further means for providing a tension connection between the said two parts of the stay.

In one form of the invention the said further connection includes a lost motion coupling which permits relative limited movement when the cylinder is pressurised. Additionally, this further connection may include the adjusting device for the effective length of the stay.

In a particular preferred construction the piston cylinder unit is located between a pair of crossheads connected or connectable to adjacent sections of the stay, and including a pair of tension links between the two crossheads on opposite sides of the cylinder.

According to another aspect of the invention there is provided a stay for a mast or other structure including means for adjusting the effective length of the stay comprising a chassis or body, one end of which is attachable to one of an anchor or stay component, at least one element movably and lockably mounted on the chassis or body and being attachable to the other of an anchor or stay component and means for moving said element towards the one end of the chassis or body to shorten the effective length of the stay.

The invention may be performed in various ways and one specific embodiment, with some possible modifications, will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation illustrating a typical mast staying system, Figure 2 is a further diagram illustrating one of the ground anchors with associated tension control and sensing devices, Figure 3 is a diagrammatic plan view of one of the tension sensing devices, Figure 4 is a side elevation of the device of Figure 3, Figure 5 is a plan view of an alternative form of tension sensing device, Figure 6 is a cross-section on the line VI--VI in Figure 5, and Figure 7 is a plan view of a tensioning and tension sensing device.

Referring first to the system illustrated in Figure 1 , the mast 10 is supported on a ground anchorage point 11 via some form of universal thrust pivot or bearing, and it is supported and located by a plurality of stays or guys cable 12 each attached to the mast at its upper end and to a fixed ground anchor 1 3 at its lower end.

As shown in Figure 2, the ground anchor is connected to a length adjusting device in the form of a turn-buckle 14, which is itself connected to a tension sensing device 15, attached in turn to the end of the stay cable 12.

One of these tension sensing devices is illustrated in Figures 3 and 4. It includes an hydraulic cylinder 20 containing a piston 21 attached to a piston rod 22 passing through a seal at the end of the cylinder. The cylinder has a projecting lug 24, which is connected by a pin 25 to a crosshead 26, which has a pair of apertured lugs 27, by which it can be coupled to the cable 12. The piston rod 22 is likewise connected by a pin 29 to a second crosshead 30, which is attached to the turn-buckle 1 4. Between the two crossheads 26, 30 extend a pair of parallel tension links 31, 32 each of which has an elongated slot 33 at each end embracing the end of a gudgeon pin or bolt 34 passing through the respective crosshead. This provides a form of lost motion coupling between the two crossheads and, therefore, allows some movement of the piston and cylinder unit.

The effective lengths of the piston and cylinder unit can be reduced by admitting hydraulic pressure through a port 36 from a power operated or manual pump (not illustrated). Assuming that the stay system is under tension, the tensile force will be initially carried by the two links 31,32 and the hydraulic unit can be inserted between the links and engaged by locating the two gudgeon pins 25, 29, these being retained by clips 37. By introducing pressure fluid into the cylinder to contract the unit the load is transferred from the links to the hydraulic unit and the pressure can then be read directly off a gauge 38, which provides an accurate indication of the tensile force in the particular stay.This can be achieved with only microscopic movement of the pins 34 within the slots 33 so that the overall length of the unit remains substantially unaltered and the tension in the stay is therefore unaffected.

After taking a tension reading, the hydraulic unit can easily be removed and inserted in position in another stay or, if preferred, a number of these units may be positioned simultaneously in the several stays of a single mast.

In the alternative construction illustrated in Figures 5 and 6, similar parts are indicated by the same reference numerals and will not need further description. The main difference is that the two links 31, 32 of the previous example are replaced by screw threaded adjusting rods 40, 41 each of which has a head 42 at one end engaging the end face of the respective crosshead 30a, the rod being slidable in the respective bore 43. At the other end each of these rods is screw threaded and is provided with an adjusting nut 44 and locknut 45. These rods, therefore, provide both a lost motion connection and also a length adjusting device and accordingly the turn-buckle 14 can then be omitted.

Figure 7 shows a device, which is similar in construction to that of Figure 5 and 6 but in which the piston unit can provide the full length adjustment needed to tension the stay during erection, and hence the device replaces the turnbuckle 14 and tension sensing device 1 5 in Figure 1.

In the Figure 7 construction the piston unit is releasably connected between a pair of crossheads 46, 47, which are slidably mounted on rods 41 and 42 and lockable thereon by fore and aft lock nuts 48 and 49. The cable 12 is connected to crosshead 46, whilst fixed crossed head 30a is connected to the anchor point 13. In use cable crosshead 46 is initially locked on the rods 40, 41, and the piston unit expanded by means of the pump to move the intermediate crosshead 47 along rods 41,42. Crosshead 47 is then locked in position by means of its lock nuts 48, 49, and aft lock nuts 49 of crosshead 46 are loosened and moved along rods 40, 41 towards crosshead 47.

The piston unit is then contracted pulling crosshead 46 along rods 40, 41 and hence shortening the effective length of the stay.

Crosshead 46 is then locked in position by its lock nuts and the tensioning process is repeated until the required tension is reached. As before the tension in the stay can be read off the pressure gauge 38.

The piston unit and pump can then be removed for use elsewhere and the stay will be held in tension by crossheads 43 and 30a and rods 40, 41. If it is subsequentiy desired to check and/or adjust the tension the piston unit is reconnected.

It will be appreciated that the piston unit should have low friction characteristics and that a range of piston units may be used depending on the required stay tension.

Preferably rods 40, 41 are of the order of 12 foot long. Suitable means other than the lock nuts may be used for locking the crossheads to the rods 40, 41, in which case the rods 40, 41 need not necessarily be threaded.

Claims (13)

1. A staying system for a mast or other structure, comprising a plurality of tension stays extending from the structure to respective spaced anchorages, means for adjusting the effective length of a stay, detachable means for sensing the tension in the stay, including a fluid piston and cylinder assembly, means for attaching the two assembly components respectively to adjacent portions of the stay, means for pressuring the cylinder and sensing the pressure therein, and further means for providing a tension connection between the two parts of the stay.

2. A staying system as claimed in claim 1 wherein said further connection includes a lost motion coupling which permits relative movement when the cylinder is pressurised.

3. A staying system as claimed in claim 1 or claim 2 wherein the further connection includes the means for adjusting the effective length of the stay.

4. A staying system as claimed in any one of the preceding claims wherein the piston cylinder unit is located between a pair or crossheads connected or connectable to adjacent sections of the stay and wherein the means for providing a tension connection include a pair of tension links extending between the crossheads on opposite sides of the cylinder.

5. A stay for a mast or other structure including means for adjusting the effective length of the stay comprising a chassis or body, one end of which is attachable to one of an anchor or stay component, at least one element movably and lockably mounted on the chassis or body and being attachable to the other of an anchor or stay component and means for moving said element towards the one end of the chassis or body to shorten the effective length of the stay.

6. A stay as claimed in claim 6 wherein the adjusting means includes a further element movably and iockably disposed on the chassis or body intermediate the first mentioned element and the one end of the body and wherein the means for moving the one element is constituted by means acting between the elements for drawing the first mentioned element towards the further element when the latter is locked on the chassis or body.

7. A stay as claimed in claim 5 or claim 6, wherein the means for drawing the first mentioned element can also move the further element away from the first element when the latter is locked on the body.

8. A stay as claimed in any one of claims 5 to 8, wherein the means for moving comprises a fluid piston cylinder assembly.

9. A stay as claimed in claim 8 wherein the fluid piston cylinder assembly is detachable and wherein the chassis or body holds the stay in tension on removal of the assembly.

10. A staying system including at least one stay as claimed in any one of claims 5 to 9 and means for determining the force applied by the means for moving to the first mentioned element to provide an indication of the tension in the stay.

11. A stay for a mast or other structure as hereinbefore described with reference to Figures 1 and 2, or Figures 1 and 2 as modified by Figures 3 and 4, Figures 5 and 6 or Figure 7.

12. A staying system for a mast or other structure as hereinbefore described with reference to and as illustrated in Figures 1 and 2, or Figures 1 and 2 as modified by Figures 3 and 4, Figures 5 and 6 or Figure 7.

13. A tension sensing device as hereinbefore described with reference to and as illustrated in Figures 3 and 4, Figures 5 and 6 or Figure 7.

1 4. A stay tensioning device as herebefore described with reference to Figure 7.