P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention title: Hook stick actuator The invention is described in the following statement: 1 Hook Stick Actuator Field of the Invention The present invention relates to a hook stick actuator. The invention is particularly useful in relation to operating overhead air-break switches, enclosed switches, reclosers, and 5 sectionalisers (switches) in power distribution networks. However, it should be understood that the invention is intended for broader application and use. Background of the Invention Switches are commonly used in the field of electric power transmission and distribution to manage the distribution network, to shift loads across the network, to interrupt power while 10 maintenance occurs, or to turn off an area of the network to make it safe. Industry standards recognise the following three main classifications of switches, which are suitable for different applications in power transmission and distribution networks: 1 Circuit breaker - which is capable of repetitive switching of full load currents and limited repetitive switching of fault currents. These switches are commonly used 15 for network protection and load switching. Modern circuit breakers generally use Sulphur Hexafluoride gas or a vacuum as the electrical breaking medium, whereas older designs may use air and oil. 2 Disconnector - normally designed for the purposes of electrical isolation and is generally not intended or designed for load current switching. 20 3 Switches - intended for load current switching for substantially less switching cycles than a circuit breaker. Depending on the class rating of the switch it may have limited or no fault current switching capability. Overhead distribution networks traditionally use ground level pole-mounted operating handles that are connected to air-break switch or disconnector mechanisms by means of an 25 insulated downrod. It is generally intended that these devices are only operated under no load, no fault, conditions. However, this does not always occur in practice, and in the event that an air-break disconnector is opened or closed under load or fault conditions, the 2 switchgear can be damaged or destroyed due to arcing. It also presents a significant safety risk to the operator who may otherwise be showered with molten metal. In early implementations of such pole-mounted devices, the operating handle was positioned at ground level and secured with a simple locking device such as a padlock. It 5 was soon realised that padlocks (and similar locking devices) could be easily removed, and that unauthorised users could operate the handle and cause switching of the overhead air break device. This presented both an inconvenience to the power network (due to network outages and infrastructure damage), and a significant safety risk to an unauthorised user who could be severely injured as a result of electric shock or burns from molten metal. 10 Furthermore, the positioning of the operating handle at ground level required the device to be earthed in order to prevent injury to authorised users whilst conducting routine switching operations. Ground level metalwork requires an earth connection which is generally made of copper. However, theft of the copper earth wire is a common occurrence, and one that exposes operators and the public to a potential electric shock 15 hazard. Modifications to this existing design included mounting the operating handle at a higher position on the pole in order to make the operating handle inaccessible to unauthorised users. By positioning the operating handle at mid-pole height, earthing of the device was no longer required. However, these designs did not improve upon the security aspects of 20 the device, as access to the operating handle was still only prevented by a padlock or similar rudimentary locking device. Furthermore, these devices did not address the safety risks associated with inadvertent switching of the air-break disconnector by an authorised operator. In view of these limitations, there is a need for a hook stick actuator that provides an 25 improved level of safety to an operator. There is also a need for a hook stick actuator with improved security features to prevent unauthorised use whilst allowing efficient operation by authorised users. In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of 30 knowledge or any combination thereof was at the priority date, publicly available, known 3 to the public, part of the common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned. Summary of the Invention The present invention provides a hook stick actuator for safely operating overhead 5 distribution switches or disconnectors in overhead electric power distribution systems. According to an aspect of the present invention, there is provided a hook stick actuator for operating overhead switchgear in power distribution networks, said hook stick actuator comprising: (a) an actuating arm being pivotable between at least: 10 (i) a first position corresponding to an open state of said overhead switchgear; (ii) a second position corresponding to a closed state of said overhead switchgear, and (b) a housing unit including locking means, said locking means being switchable between 15 (i) a first locking state wherein said actuating arm is substantially restricted to rotation in a first direction; and (ii) a second locking state wherein said actuating arm is substantially restricted to rotation in a second direction (not being the same as the first direction). The first direction may be a clockwise direction, and the second direction may be an 20 anticlockwise direction. Alternatively, the first direction may be an anticlockwise direction, and the second direction may be a clockwise direction. Preferably, the actuating arm is fixed to a pivotable driving shaft that extends through an opening in the housing unit. The housing unit may be a salable metal box that is mounted to a power distribution pole using conventional bolts, bands or screw fixings. The opening 25 through which the driving shaft extends is preferably located on a front surface of the housing unit, and the actuating arm is fixed to the driving shaft about its central point.
4 The actuating arm may be a longitudinal strip of metal, preferably galvanized steel, that includes an upward facing hook portion at each of its ends. It is preferable that when the actuating arm is the first position or the second position, it rests at an angle of approximately 45 degrees to the horizontal. Therefore, one of the hook portions will 5 naturally be positioned higher than the other. It is desirable that an operator will use a conventional power industry standard insulated hook stick to engage this higher hook portion and pull the actuating arm down in order to open or close the overhead air-break switch. A ratchet member may be axially mounted to the driving shaft, and preferably the ratchet 10 member is a ratchet wheel. The ratchet wheel may be provided with a plurality of evenly spaced teeth and positioned within the housing unit. The locking means preferably includes a pawl member adapted to engage with the ratchet wheel. The pawl member may be axially mounted to a locking shaft that extends through a further opening in the housing unit. Desirably, the further opening through which the 15 locking shaft extends is also located on a front surface of the housing unit. The locking means preferably includes biasing means capable of biasing the rotation of the pawl member in either the first or second (e.g. clockwise or anticlockwise) direction. The biasing means may include an over-centre spring attached to the pawl member in order to bias the pawl member in either the first or second direction. 20 The pawl member may include a first pawl tooth adapted to engage the ratchet member such that the ratchet member is substantially restricted to rotation in the first direction; and a second pawl tooth adapted to engage the ratchet member such that the ratchet member is substantially restricted to rotation in the second direction. The locking shaft may include a locking arm located externally from the housing unit to 25 allow access by an operator. The locking arm may be rotated by an operator using a conventional insulated hook stick. Desirably, the locking arm allows an operator to switch the locking means between the first locking state and the second locking state. The insulated hook stick may be inserted into designated openings in the locking arm to facilitate switching between locking states. Advantageously, switching of the locking 5 means between the first locking state and the second locking state reverses the rotational biasing of said pawl member. The locking means may further include a locking plate axially mounted to the locking shaft. In addition, the locking means may include a locking bar axially mounted to a 5 vertical locking shaft, the vertical locking shaft being rotatably supported by a bearing assembly. Preferably, the locking bar is adapted to engage with a detent on the locking plate to lock the rotational position of the actuating arm. Advantageously, the rotational position of the actuating arm is capable of being locked in either the first position or the second position. 10 The locking bar may be biased to automatically engage with the detent when the actuating arm rotates to either the first position or the second position. Desirably, the vertical locking shaft includes a key slot to allow an operator to rotate the vertical locking shaft and disengage the locking bar from the detent. The hook stick actuator may further comprise a bevel gear arrangement including a first 15 gear axially mounted to said driving shaft; and a second gear axially mounted to a coupling shaft that extends through an aperture in said housing unit, wherein rotation of said actuating arm causes rotation of said coupling shaft. Advantageously, a distal portion of the coupling shaft includes a coupling member to allow connection of the coupling shaft to an overhead downrod. 20 In an embodiment of the invention, the aperture may be in a side surface of said housing unit. Rotation of the coupling shaft may cause vertical movement of the overhead downrod. Desirably, the overhead downrod is fixed to the coupling such that when the coupling shaft rotates through a given range of motion, the downrod either moves upward or downward depending on the configuration of the overhead air-break switch. 25 In a further embodiment of the invention, the aperture is in a top surface of the housing unit. Rotation of the coupling shaft may cause rotation of said overhead downrod.
6 Brief Description of the Drawings Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. These embodiments are given by way of illustration only and other embodiments of the invention are possible. Consequently, the particularity of the 5 accompanying drawings is not to be understood as superseding the generality of the preceding description. In the drawings: Figure 1A is a perspective view line drawing of a hook stick actuator according to a preferred embodiment of the present invention, with the actuating arm in a first position. Figure lB is a perspective view line drawing of the hook stick actuator of Figure 1A, 10 showing the actuating arm is a second position. Figure 2 is a partial sectional rear view line drawing of the hook stick actuator according to Figure 1A. Figure 3A is a rear view photograph of the hook stick actuator according to Figure 1A. Figure 3B is a further rear view photograph of the hook stick actuator according to Figure 15 1A. Figure 4 is a perspective view line drawing of a hook stick actuator according to a further embodiment of the present invention. Description of Preferred Embodiments Embodiments of the hook stick actuator will now be described with reference to the 20 accompanying drawings. The invention is particularly useful in relation to operating overhead air-break switches (and disconnectors) in power distribution networks and it will therefore be convenient to describe the invention in that environment. However, it should be understood that the invention is intended for broader application and use. Referring to the drawings, Figures 1A and lB illustrate a hook stick actuator according to a 25 preferred embodiment of the present invention. The hook stick actuator 100 comprises a housing unit 104 that is fixed to an electrical distribution pole 180 using conventional bolts 152, bands or screw fixings. Preferably, the housing unit 104 is fixed to the distribution pole 180 at such a height that access by unauthorised users is prevented. The mounting 7 height of the hook stick actuator 100 is determined by the electrical utility company in accordance with its engineering standards, operating policies, and occupational health and safety policies. The housing unit 104 is preferably manufactured from galvanised steel, although it should be understood that other suitable materials could also be used. 5 The hook stick actuator 100 also comprises an actuating arm 102, external to the housing unit 104, which is fixed to a pivotable driving shaft 106. The driving shaft 106 extends through an opening in a front surface of the housing unit 104 and is mounted in the opening using a bearing mechanism 170 that allows the driving shaft 106 and actuating arm 102 to pivot. The actuating arm 102 is a longitudinal strip of galvanised steel, having 10 upward facing hook portions 150 at each of its ends. The actuating arm 102 is rotatable between a first position (as illustrated in Figure 1A) corresponding to an open state of an overhead air-break switch (not shown), and a second position (as illustrated in Figure IB) corresponding to a closed state of the overhead air break switch (not shown). When the actuating arm 102 is in the first position or the second 15 position, it rests at an angle of approximately 45 degrees to the horizontal. However, it should be understood that other angles may also be suitable depending on the specific air break switch or disconnector used. Due to the angle of the actuating arm 102, one of the hook portions 150 will naturally be positioned higher than the other. It is desirable that an operator will use a conventional power industry standard insulated hook stick to engage 20 this higher hook portion 150 and pull the actuating arm 102 downward in order to open or close the overhead air-break switch. The switching operation is complete when the actuating arm 102 has rotated to the opposite orientation of approximately 45 degrees to the horizontal. Within the housing unit 104, as shown in Figure 2 and Figures 3A and 3B, a ratchet wheel 25 120 is axially mounted to the driving shaft 106. The ratchet wheel 120 includes a plurality of teeth 122 that are evenly-spaced around the circumference of the ratchet wheel 120. The housing unit 104 also includes locking means that are switchable between a clockwise locking state wherein the actuating arm 102 is substantially restricted to rotation in a clockwise direction, and an anticlockwise locking state wherein the actuating arm 102 is 30 substantially restricted to rotation in an anticlockwise direction. The locking means comprises a pawl member 124 (as seen in Figures 3A and 3B) that is mounted to a locking 8 shaft 110 within the housing unit 104, and adapted to engage the teeth 122 of the ratchet wheel 120. The locking shaft 110 extends through an opening in a front surface of the housing unit 104, and is mounted in the opening using a bearing mechanism 170 that allows the locking shaft 110 to rotate. 5 The pawl member 124 includes a first pawl tooth (not shown) adapted to engage the teeth 122 of the ratchet wheel 120 and substantially restrict rotation of the ratchet wheel 120 to the clockwise direction. The pawl member 124 also includes a second pawl tooth 126 adapted to engage the teeth 122 of the ratchet wheel 120 and substantially restrict rotation of the ratchet wheel 120 to the anticlockwise direction. The locking means includes a 10 biasing means that biases the rotation of the pawl member 124 in either the clockwise or anticlockwise direction. Preferably, the biasing means is a spring member that can be switched to provide a bias to the pawl member 124 in either the clockwise or anticlockwise direction. As the ratchet wheel 120 is fixed to the driving shaft 106, which in turn is fixed to the 15 external actuating arm 102, restricting the rotation of the ratchet wheel 120 in a given direction (either clockwise or anticlockwise) also restricts rotation of the actuating arm 102 in the same direction. The locking shaft 110 also includes a locking arm 108 that is located externally from the housing unit 104. As with the actuating arm 102, the locking arm 108 is also rotatable 20 between two discrete positions, corresponding to the clockwise and anticlockwise locking states of the actuating arm 102. The locking arm 108 allows an operator to rotate the pawl member 124 and disengage an engaged pawl tooth from the ratchet wheel 120. Once the rotation of the pawl member 124 proceeds beyond a given point, the biasing means switches (or reverses) and applies a bias to the pawl member 124 in the opposite direction. 25 Reversal of the rotational bias causes the pawl member 124 to rotate further such that the opposing pawl tooth (i.e. the pawl tooth not previously engaged with the ratchet wheel 120) engages with the teeth 122 of the ratchet wheel. The locking arm 108 also comprises two switching openings 156 which can be engaged by an operator, using a conventional insulated hook stick, in order to rotate the locking arm 30 108 to the desired locking state. In a particularly preferred embodiment of the present invention, the rotational position of the locking arm 108 may be locked using a padlock 9 160 which is inserted through a lock opening in the locking arm 108 and a corresponding lock opening in the housing unit 104. Desirably, the padlock 160 prevents any unauthorised operation of the hook stick actuator 100. However, it should be understood that a similar configuration could also be used to lock the rotational position of the 5 actuating arm 102. The locking means also comprises a locking plate 128 that is axially mounted to the locking shaft 110 and positioned adjacent to the pawl member 124, although the locking plate 128 does not engage with the ratchet wheel 120. The locking plate 128 includes two detents 130 in its outer edge. The locking means further comprises a locking bar 132 10 axially mounted to a vertical locking shaft 134 that is rotatably supported by a bearing mechanism 170. The locking bar 132 is adapted to engage with the detents 130 of the locking plate 128 and is rotatable between two discrete locking positions. When the actuating arm 102 is in either the first position or second position, an end of the locking bar 132 will be engaged with one of the detents 130 of the locking plate 128. When the 15 locking bar 132 is engaged with either of the detents 130, rotation of the locking plate 128 will be prevented. Furthermore, given that the locking plate 128 is fixed to the locking shaft 110, rotation of the pawl member 124 is also prevented while the locking bar 132 is engaged with a detent 130. By locking the rotational position of the pawl member 124 (and particularly the pawl tooth 126), rotation of the ratchet wheel 120 and thus the 20 actuating arm 102 are also substantially prevented. The vertical locking shaft 134 includes a key slot 112 that is accessible to an operator from the outside of the housing unit 104. An operator can insert a keyed end of a conventional hook stick into the key slot 112 and rotate the locking shaft 134 until the locking bar 132 becomes disengaged from the detent 130 of the locking plate 128. Preferably, the operator 25 must turn the locking shaft 134 through a quarter turn. However, it should be understood that other configurations could also be used. Once the locking shaft 134 has been sufficiently rotated, the locking bar 132 will be held in a neutral position (i.e. a position wherein the locking bar 132 is not engaged with the detents 130) by means of a spring 136. Once an operator has completed a switching operation of the locking arm 108 and the 30 actuating arm 102, the spring 136 will cause the locking bar 132 to automatically rotate and engage with a detent 130. It is preferable that each end of the locking bar 132 will always only engage with a specific detent 130 of the locking plate 128.
10 In a particularly preferred embodiment of the present invention, the hook stick actuator 100 also comprises a funnel-shaped guide means 114 surrounding the key slot 112. The guide means 114 assists an operator to insert a keyed end of an insulated hook stick into the key slot 112, and thereafter perform the required rotation of the vertical locking shaft 134. 5 The hook stick actuator 100 also comprises a bevel gear arrangement (as shown in Figures 1A to 3B) that is contained within the housing unit 104. The bevel gear arrangement includes a first gear 140 axially mounted to the driving shaft 106, and a second gear 142 axially mounted to a coupling shaft 116 that extends through an aperture in a top surface of the housing unit 104. The coupling shaft 116 is mounted in the opening using a bearing 10 mechanism 170 that allows the coupling shaft 116 to rotate. The first gear 140 is mounted to the driving shaft 106 and is positioned substantially adjacent to the ratchet wheel 120. As the first gear 140 is fixed to the driving shaft 106, it rotates as the actuating arm 102 is rotated by an operator. Similarly, when the rotational position of the ratchet wheel 120 is locked (by locking engagement of the pawl tooth 126 15 with the teeth 122 of the ratchet wheel 120), rotation of the first gear 140 is also prevented. The second gear 142 engages with the first gear 140, by meshing of the teeth of the first gear 140 and the second gear 142, such that rotation of the first gear 140 causes rotation of the second gear 142. The coupling shaft 116 extends through an aperture in a top surface of the housing unit 104 and includes a coupling member 118 attached to its distal end. The 20 coupling member 118 preferably allows for attachment of a fixing 154 which can be connected to an overhead downrod (not shown) in order to implement switching of an overhead air-break switch or disconnector. In this configuration, the fixing 154 and attached downrod (not shown) rotate in response to rotation of the actuating arm 102 by an operator. It is therefore preferable that the overhead air-break switch or disconnector can 25 be operated in response to the rotational movement of the downrod. In an alternate embodiment of the present invention, as illustrated in Figure 4 of the drawings, the bevel gear arrangement includes a first gear 140 axially mounted to the driving shaft 106, and a second gear 142 axially mounted to a coupling shaft 116 that extends through an aperture in a side surface of the housing unit 104. The coupling shaft 30 116 is mounted in the opening using a bearing mechanism 170 that allows the coupling shaft 116 to rotate. As with the previous embodiment, the coupling shaft 116 includes a 11 coupling member 118 attached to its distal end. The coupling member 118 preferably allows for attachment to an overhead downrod (not shown) in order to implement switching of an overhead air-break switch or disconnector. In this configuration, rotation of the actuating arm 102 by an operator causes vertical movement of the downrod. That is, 5 rotation of the actuating arm 102 in one direction will cause the downrod to move upwards, whereas rotation of the actuating arm 102 in the opposite direction will cause the downrod to move downwards. In accordance with this embodiment, it is preferable that the overhead air-break switch or disconnector can be operated in response to the vertical movement of the downrod. 10 In relation to either of the described embodiments of the invention, operation of the hook stick actuator 100 (i.e. switching an overhead air-break switch to either an open or closed state) by an authorised operator is performed according to the following steps: 1. If a padlock 160 has been applied to the locking arm 108, then it is firstly necessary for the operator to remove this padlock 160 using an appropriate key 15 provided to authorised operators. 2. The operator then inserts a keyed end of a conventional hook stick into the key slot 112 (using the guide means 114 to direct the keyed end into the key slot 112), and rotates the locking shaft 134 through a quarter turn in order to disengage the locking bar 132. 20 3. The operator then removes the hook stick from the key slot 112, and inserts a branch of the hook stick into the higher of the two switch openings 156. A downward force is then applied by the operator until the locking arm 108 rotates to the desired opposing position. 4. The branch of the hook stick is then removed from the switch opening 156 in the 25 locking arm 108 and inserted into the higher of the two hook portions 150. A downward force is then applied by the operator until the actuating arm 102 rotates to the desired opposing position. 5. If the hook stick actuator 100 is to remain in this state, the operator may then apply the padlock 160 to the locking arm 108.
12 The word 'comprising', and forms of the word 'comprising', when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 5 As the present invention may be embodied in several forms without departing from the essential characteristics of the invention, it should be understood that the above described embodiments should not be considered to limit the present invention but rather should be construed broadly. Various modifications, improvements and equivalent arrangements will be readily apparent to those skilled in the art, and are intended to be included within 10 the spirit and scope of the invention.