PERRY SLINGSBY SYSTEMS LTD. (Ings Lane Kirbymoorside York YO62 6EZ, GB)
Spencer, Allan (12 Ingsgarth Pickering North Yorkshire YO18 8DA, GB)
| 1. | A telescopic mast assembly having a plurality of mast sections nested within one another, a drive member connected to at least one of said mast sections, drive member storage means for storing the drive member and mechanical actuation means connected to the drive member storage means for paying out and retracting the drive member, wherein. the drive member is constructed from a material having a first state with a flat cross section and a second state with a curved cross section such that the drive member is in its first state when contained on the storage means and is in its second state when it has been paid out. |
| 2. | A telescopic mast assembly as claimed in Claim 1 wherein the drive member experiences a biasing force to retain it in its first state. |
| 3. | A telescopic mast assembly as claimed in Claim 1, wherein the material of the drive member comprises a textile ribbon having a plurality of woven fibres embedded in a matrix, the fibres being arranged at an angle relative to the textile ribbon length such that when the biasing force is released, the textile ribbon is reshaped from its first state to its second state. |
| 4. | A telescopic mast assembly as claimed in Claim 1 or Claim 2, wherein the textile ribbon is of a type described in International Patent Application W097/35706. |
| 5. | A telescopic. mast assembly as claimed in any preceding Claim, wherein the storage means comprises a housing within which the drive member is wound upon itself. |
| 6. | A telescopic mast assembly as claimed in any preceding Claim, wherein the mechanical actuation means comprises a motor coupled to a worm and a sprocket wheel, said sprocket wheel having a plurality of teeth on its circumference which are engageable with a length of the driver member. |
| 7. | A telescopic mast assembly as claimed in any preceding Claim, wherein said drive member contains a plurality of engagement means, spaced along the length of the driver member so as to be engageable with the teeth of the sprocket wheel. |
| 8. | A telescopic mast assembly as claimed in any preceding Claim, wherein the telescopic mast further comprises means for determining the position of the drive means paid out from the storage means. |
| 9. | A telescopic mast assembly as claimed in Claim 8, wherein the means for determining the position of the drive means comprises an optical coder used to count the drive member engagement means as the drive member is paid out. |
Telescopic masts are well known as such and commonly consist of a plurality of interconnected mast sections which can move relative to one another along a common longitudinal axis to extend and retract the mast. Mechanical actuation of the expansion and retraction of the mast can be achieved in a number of ways. Masts can be pneumatically operated, however, such masts are required to be gas-tight and the mast can be rendered inoperable by the presence of small cracks or holes in the mast sections. In addition, pneumatic systems used with such masts are bulky, and therefore lack manoeuvrability.
US Patent No 5,718,087 (Featherstone et al) discloses a telescopic mast with a drive mechanism. In this case, the mast is attached to a drive member, which is in turn connected to a motor for paying out and retracting the drive member. The drive member is made from a stainless steel strip of foil, which, in its retracted position is rolled-up on a drum. In use, the drive member is retracted by the action of a drive wheel connected to the drive motor, the drive wheel rotates the drum causing the drive member to be retracted and rolled onto the drum.
The drive member of US 5,718,0. 87 has a planar cross section when contained on the drum, however, when the drive member is paid out by rotation of the drum, the drive member passes through a contour forming means which changes the shape of the drive member from having a planar cross section to one with a circular cross section.
The use of a contour forming means such as a mold or a set of die to deform the drive member is costly and its presence adds to the weight and size of the telescopic mast. The fact that the drive member passes through a contour forming means will induce, after a small number of cycles, fatigue problems in the drive member. Also, the motor drives a support wheel rather than the drive member itself, reducing the efficiency of the system due to friction.
In accordance with a first aspect of the invention there is provided a telescopic mast having a plurality of mast sections nested within one another, a drive member connected to at least one of said mast sections, drive member storage means for storing the drive member and mechanical actuation means connected to the storage means for paying out and retracting the drive member, wherein the drive member is constructed from a material having a first state with a flat cross section and a second state with a curved cross section such that the drive member is in its first state when contained on the storage means and is in its second state when it has been paid out.
Preferably, the drive member experiences a biasing force to retain it in its first state.
Preferably the material of the drive member comprises a textile ribbon having a plurality of woven fibres embedded in a matrix, the fibres being arranged at an angle relative to the textile ribbon length such that when the biasing force is released, the textile ribbon is re-shaped from its first state to its second state.
Preferably, the textile ribbon is of a type described in International Patent Application W097/35706.
The storage means may comprise a housing within which the drive member is coiled upon itself.
Alternatively, the storage means may comprise a reel upon which the drive member is wound.
Preferably, the mechanical actuation means comprises a motor coupled to a worm and a sprocket wheel, said sprocket wheel having a plurality of teeth on its circumference which are engageable with a length of the driver member.
Preferably, said driver member contains a plurality of engagement means, spaced along the length of the driver member so as to be engageable with the teeth of the sprocket wheel.
Preferably, the telescopic mast further comprises means for determining the position of the drive means paid out from the storage means.
Preferably, the means for determining the position of the drive means comprises an optical coder used to count the drive member engagement means as the drive member is paid out.
The present invention will now be described by way of example only with reference to the accompanying drawings in which: Fig 1. shows a side view of a telescopic mast in accordance with the present invention ;
Fig 2. shows a schematic view of the drive mechanism used in the embodiment of Fig. 1 ; Fig 3a. shows a cross sectional view of the drive member contained on the drive member storage means, Fig 3b. shows a cross sectional view of the drive member once it has been paid out in a first drive member configuration, Fig 3c shows a cross sectional view of a second drive member configuration once it has been paid out, and Fig. 3d shows an optional edge configuration of the drive member ; and Fig. 4 shows a schematic view of a second embodiment of a drive mechanism means for detecting the position of the drive means.
Fig 1. shows a telescopic mast assembly 1 forming one embodiment of the present invention. The mast 3 in this embodiment is made up of five mast sections 5a to 5e, sections 5d to 5a are progressively smaller in diameter and allow these sections to be nested together in a known manner. Pivot 9, mounted. on a support member 11, allows the mast to pivot in the vertical direction. In this example, the maximum angle of tilt is 182.5° and the minimum angle of tilt is 15°. The mast can also pivot horizontally, this mechanism is not shown in Fig 1.
The mast sections 5a to 5e are hollow and, in this example, manufactured from a carbon composite material to give the fully extended mast 3 a highly
favourable strength to weight ratio in comparison to other similar masts.
The lowermost part of the mast between the mast section 5e and the pivot 9 forms a drive housing 40 which contains the drive member and mechanical actuation means which are described with reference to Fig 2. Mast end 7 is attached to mast section 5a and contains electrical and mechanical connectors which allow apparatus to be secured to the mast end 7 and operated remotely.
The drive member is denoted by three reference numerals. Reference numeral 10 denotes the entire drive member, reference numeral 17 denotes the drive member in its first state when contained on the drive member storage means and reference numeral 18 denotes the drive member in its second state.
Fig 2. shows the drive housing 40 containing the drive member 17 which is made from a textile ribbon. wound upon itself within a housing 15.
The textile ribbon of the drive member 10 consists of woven fibres embedded in a matrix to form a fibre- reinforced composite. The fibres are arranged within the matrix such that when a force, keeping the textile ribbon in its first state is removed from the textile ribbon, the positioning of the fibres causes the textile ribbon to assume a second state or shape.
Details of the textile ribbon used can be found in International Patent Application No PCT/GB97/00839.
In the present invention, the first state of the textile ribbon of the drive member 17 occurs when the drive member 17 is stored in the housing 15 and has a flat cross section. This is shown in Fig 3a. The second state of the ribbon of which the drive member 10 is made is shown when the drive member 18 is paid out from the reel 15. The drive member 18 has a crescent cross sectional shape in its second state as can be seen from Fig 3b. Fig 3c shows a drive member 33 with a substantially circular cross sectional shape.
The degree to which the. cross section of the textile ribbon is curved can be engineered by alteration of the angle of the fibres relative to the longitudinal axis of the textile ribbon. In addition, the textile ribbon can be engineered in order to control the speed at which the textile ribbon changes from its first state to its second state. This can be done by choosing a combination of tensile and low compression modulus fibres and the appropriate resin for use in making the textile ribbon.
The textile ribbon used for the drive member 10 contains a series of holes 16 (Fig. 3a and Fig. 3b) punched along its neutral axis so as to be engageable with the teeth 27 of a sprocket wheel 21. The textile ribbon of the drive member 10 can incorporate
electrical power and data cables to monitor the equipment carried on the mast end 7.
The drive housing 40 contains mechanical actuation means for paying out and retracting the drive member 10. The mechanical actuation means consists of a planetary gear 19 with power supply connector 35.
The planetary gear 19 is connected, via a rotatable shaft 20 with a worm 23 located on its end, to the sprocket 21 which has teeth 27. A pinch roller 29 is provided below the sprocket 21 and is arranged for abutment with the teeth 27 of the sprocket 21 in order to improve grip on the drive member 10. In this example, the planetary gear 19 is connected to a 70 watt DC Motor and the mechanical actuation means is designed to provide a maximum deployment speed of 0.25mus-1. The drive housing 40 is also provided with an umbilical coupling 31 and is designed to be weatherproof and rain resistant.
In use, the telescopic mast assembly 1 of the present invention can be extended and retracted in the following manner. Starting from the position in which the mast is fully retracted, the mast sections 5a to 5d are nested inside mast section 5e to give a total mast length of slightly greater than the length of mast section 5e. In the example shown in Fig 1. the maximum extended length of the mast is 1910 mm and the minimum retracted length is 510mm. It will be appreciated that masts made in accordance with the
present invention can be made of different maximum/minimum lengths.
The drive member 18 is connected to mast member 5a at or near mast end 7. In order to pay out the drive member 17, the motor is actuated, which turns the planetary gear and sprocket 21. The sprocket teeth 27 are arranged to be engageable with the holes 16 in the textile ribbon of the drive member 10 and also to co-operate with the pinch roller 29. As shown in Fig 2, the sprocket 21 is driven in the anti-clockwise direction in order to pay out the drive member. The drive member 17 contained within the housing 15 has a flat cross sectional shape first state (Fig 3a). As the drive member 17 is unwound, the force applied to the textile ribbon of the drive member 17 to keep it flat is removed and the textile ribbon changes into its curved cross sectional shape (second state Fig 3b) as indicated by reference numeral 18.
Reference numeral 37 shows the point at which this process begins. The teeth 29 engage with the holes 16 in the textile ribbon along the central longitudinal axis of the drive member 10. The drive member 10 is paid out until the telescopic mast 3 is fully extended. The telescopic mast 3 can be partially extended by paying out a portion of the drive member 10 and will remain static on removal of power from the sprocket 21.
In order to retract the telescopic mast 3, the direction of turn of the sprocket 21 is reversed to
be clockwise. This causes the drive member 10 to be wound into the housing 15 and pull the mast 3 back to its minimum size (not shown).
The second state of the textile ribbon 10 may be an arcuate curve less than a full circle, or a full circle, or greater than a full circle with longitudinal edges overlapping (as seen in Fig. 3c).
Where the longitudinal edges overlap, it is possible to provide for these to interengage. Fig. 3d shows one example of this, the longitudinal edges being formed with interlocking castellations 41.
The mast is designed such that all torsional, bending and shear loads are experienced by the mast sections 5a to 5e and the drive member 10 experiences an axial compressive load.
Testing has shown that a 2m length of textile ribbon can withstand axial compressive loads in excess of 40kg without buckling. The sprocket 21 is capable of driving the drive member in either direction when loaded axially with 24kg.
Fig. 4 shows a second embodiment of the present invention. Identical reference numerals to those in Fig. 2 have been used where parts are similar. Fig. 4 shows means for detecting the position of the drive means, provided adjacent to the drive housing, by an optical encoder 39. The optical encoder 39 provides
data such as the length of extension of the mast and the number of times the mast has been extended and retracted. This result is achieved by having the optical encoder 39 count the holes 16 (Fig 3a and Fig. 3b) in the drive member as they pass the optical encoder 39. This data is used by control and instrumentation software to give a read-out of the mast length and information on the number of times the mast has been extended and retracted which is useful in repair and maintenance checks.
The embodiments described have a number of advantages. The drive motor acts directly on the drive member, which allows the mechanism to be simplified. Since the sprocket wheel pushes onto the drive member, the distance necessary to reach the second stable state is dramatically reduced and thus the axial length of the mechanism is greatly reduced.
The drive mechanism makes use of a low component count, with the components being standard items such as DC motor. with planetary gearhead, sprocket wheel, and pinch roll.
The invention enables the production of telescopic masts meeting the requirements for use onshore or underwater: cost effective, light, small size, simple maintenance, and long lifetime.
Improvements and modifications may be incorporated herein without departing from the scope of the invention.
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