WHEEL, Frank (68 Avocet Island Quays, Wannanup, Western Australia 6210, AU)
LEONARD, Wayne (3 Alice Street, Bassendean, Western Australia 6054, AU)
HORTON, Ramon (5 Wattle Place, Canning Vale, Western Australia 6155, AU)
WHEEL, Frank (68 Avocet Island Quays, Wannanup, Western Australia 6210, AU)
LEONARD, Wayne (3 Alice Street, Bassendean, Western Australia 6054, AU)
The Claims Defining the Invention ar© as Follows:
1. A torque reaction mechanism associated with a rotatable element, the torque reaction mechanism comprising a first coupling element for location adjacent the rotatable element, the first coupling element being adapted to cooperate with a second coupling element on a powered driving tool for delivering rotational torque to the rotatable element, whereby cooperation between the two coupling elements is adapted, to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
2. A torque reaction mechanism according to claim 1 wherein the first coupling element comprises a sleeve and the second coupling element comprises a block for mounting on the body of the driving tool, the block being adapted to be received in the sleeve for sliding movement therealong.
3. A torque reaction mechanism according to claim 1 or 2 wherein sleeve is of rectangular cross-section and the block is of a matching cross-section to allow the sliding movement therealong while being constrained against rotation therein.
4. A torque reaction mechanism according to claim 2 or 3 wherein the sleeve is rigidly mounted about the rotatable element and the block is provided on a non-rotatable part of the powered driving tool.
5. A torque reaction mechanism associated with a rotatable element and a powered driving tool having a rotary drive portion drivingly engageable with the rotatable element for delivering rotational torque to the rotatable element, the torque reaction mechanism comprising a first coupling element located adjacent the rotatable element and a second coupling element on a non- rotatable part of the powered driving tool, the first coupling element being adapted to cooperate with the second coupling element whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
6. A torque reaction mechanism according to claim 5 wherein the first coupling element comprises a sleeve disposed about the rotatable element and the second coupling element comprises a block for mounting on the body of the driving tool, the block being adapted to be received in the sleeve for sliding movement therealong.
7. A torque reaction mechanism associated with a rotatable element and a powered driving tool having a rotary drive portion drivingly engageable with the rotatable element for delivering rotational torque to the rotatable element, the torque reaction mechanism comprising a first coupling element disposed about the rotatable element and a second coupling element on a non-rotatable part of the powered driving tool, the first coupling element being adapted to cooperate with a second coupling element on a powered driving tool whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation, wherein first coupling element comprises a sleeve and the second coupling element comprises a block which is mounted on the body of the driving tool and which is adapted to be received in the sleeve for sliding movement therealong.
8. A torque reaction mechanism associated with a rotatable element and a powered driving tool for delivering rotational torque to a rotatable element, the torque reaction mechanism comprising a coupling element on the powered driving tool, the coupling element being adapted to cooperate with a corresponding coupling element associated with the rotatable element, whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
9. A torque reaction mechanism according to claim 8 wherein the coupling element comprises a block for mounting on the body portion and the corresponding coupling element comprises a sleeve which is adapted to receive the block for sliding movement therealong. 10. A powered driving tool for delivering rotational torque to a rotatable element, the powered driving tool comprising a body portion adapted to be held by a user, a rotary drive portion adapted for driving engagement with the rotatable element, and a coupling element fixedly mounted on the body portion, the coupling element being adapted to cooperate with a corresponding coupling element associated with the rotatable element, whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation. 11. A powered driving tool according to claim 10 wherein the coupling element comprises a block which is mounted on the body portion and the corresponding coupling element comprises a sleeve which is adapted to receive the block for sliding movement therealong.
12.A torque reaction mechanism substantially as herein described with reference to the accompanying drawings. |
Torque reaction mechanism for a valve arrangement
Field of the Invention
This invention relates to a torque reaction mechanism.
Background Art
A powered driving tool such as a torque gun can be used to deliver rotational torque to a rotatable element such as, for example, a rotary drive input for a mechanism. At typical example of a mechanism having a rotary drive input is an operating mechanism for a valve commonly used in alumina processing plants. Traditionally, such valves have required forces much greater than those achievable by an operator without mechanical intervention to operate the valve handles and so it has been common to use an impact device (such as a sledge hammer) to strike the handles to cause them to turn.
The need to operate the valve handles manually by striking them with means such as a sledge hammer can be exhausting, and also dangerous, for an operator. An operator can, for example, develop injuries through having to swing a heavy sledge hammer for prolonged periods. Further, injuries can also be sustained in cases where an operator does not strike the targeted handle correctly, with the result that the sledge hammer deflects from the handle, or misses the handle altogether, and hits the operator or other personnel, or equipment, in the vicinity. Accordingly, there haves been various proposals for mechanisms which would allow valves to be operated in a manner which is less manually intensive. At least one proposal involves drive inputs for operating the valves, with rotational torque being delivered to each drive input as required by a portable torque gun which is drivingly connected to the drive input.
Reaction torque is generated during operation of the torque gun and so it is advantageous that there be a mechanism for transferring the reaction torque away from the operator of the torque gun rather than the operator having to resist the reaction torque.
The present invention seeks to provide such a torque reaction mechanism.
Disclosure of the Invention
According to a first aspect of the invention there is provided a torque reaction mechanism associated with a rotatable element, the torque reaction mechanism comprising a first coupling element for location adjacent the rotatable element, the first coupling element being adapted to cooperate with a second coupling element on a powered driving tool for delivering rotational torque to the rotatable element, whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
With this arrangement, reaction torque arising from operation of the powered driving tool is transferred through the second coupling element on the tool to the first coupling element. In this way, an operator holding the powered driving tool merely has to guide the tool during its operation and does not have to counteract any reaction torque.
The first coupling element may comprise a sleeve and the second coupling element may comprise a block on the body of the driving tool adapted to be received in the sleeve for sliding movement therealoπg.
The sleeve may be of rectangular cross-section and the block may be of a matching cross-section to allow the sliding movement therealong while being constrained against rotation therein.
Typically, the sleeve is rigidly mounted about the rotatable element and is restrained against rotation.
According to a second aspect of the invention there is provided a torque reaction mechanism associated with a rotatable element and a powered driving tool having a rotary drive portion drivingly engageable with the rotatable element for delivering
rotational torque to the rotatable element, the torque reaction mechanism comprising a first coupling element located adjacent the rotatable element and a second coupling element on a non-rotatable part of the powered driving tool, the coupling element being adapted to cooperate with a second coupling element on a powered driving tool whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
According to a third aspect of the invention there is provided a torque reaction mechanism associated with a rotatable element and a powered driving tool have a rotary drive portion drivingly engageable with the rotatable element for delivering rotational torque to the rotatable element, the torque reaction mechanism comprising a first coupling element disposed about the rotatable element and a second coupling element on a non-rotatable part of the powered driving tool, the first coupling element being adapted to cooperate with a second coupling element on a powered driving tool whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation, wherein first coupling element comprises a sleeve and the second coupling element comprises a block which is mounted on the body of the driving tool and which is adapted to be received in the sleeve for sliding movement therealong.
According to a fourth aspect of the invention there is provided a torque reaction mechanism associated with a powered driving tool for delivering rotational torque to a rotatable element, the torque reaction mechanism comprising a coupling element on the powered driving tool, the coupling element being adapted to cooperate with a corresponding coupling element associated with the rotatable element, whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
Preferably, the coupling element comprises a block for mounting on the body of the driving tool and the corresponding coupling element comprises a sleeve which is adapted to receive the block for sliding movement therealong.
According to a fifth aspect of the invention there is provided a powered driving tool for delivering rotational torque to a rotatable element, the powered driving tool comprising a body portion adapted to be held by a user, a rotary drive portion adapted for driving engagement with the rotatable element, and a coupling element fixedly mounted on the body portion, the coupling element being adapted to cooperate with a corresponding coupling element associated with the rotatable element, whereby cooperation between the two coupling elements is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool while constraining the two coupling elements against relative rotation about the axis of rotation.
Preferably, the coupling element comprises a block which is mounted on the body portion and the corresponding coupling element comprises a sleeve which is adapted to receive the block for sliding movement therealong.
Brief Description of the Drawings
The invention will be better understood by reference to the following description of one specific embodiment as shown in the accompanying drawings in which:
Figure 1 is a schematic sectional side view of a conventional .drain valve intended to be modified by apparatus which utilises a torque reaction mechanism according to the embodiment;
Figure 2 is a sectional view of the apparatus which utilises the torque reaction mechanism according to the embodiment and which is fitted on to the conventional drain valve;
Figures 3 to 6 are views similar * to Figure 2 except that in each case the powered driving tool incorporating part of the torque reaction mechanism according to the embodiment is shown connected to the apparatus;
Figure 7 is a schematic elevational view of the apparatus fitted onto the drain valve;
Figure 8 is an elevational view of the base plate;
Figure 9 is a sectional view of the base plate;
Figure 10 is a further sectional view of the base plate;
Figure 11 is an elevational view of the casing;
Figure 12 is a sectional view of the casing;
Figure 13 is an elevational view of the hub adapted to be fitted to the yoke bush of the drain valve;
Figure 14 is a sectional view of the hub;
Figure 15 is a sectional view of the first rotatable element;
Figure 16 is an end view of the first rotatable element;
Figure 17 is a perspective view of the nut forming part of the restraining means for the valve stem;
Figure 18 is a sectional view of the nut;
Figure 19 is a a perspective view of a block section forming part of the restraining means for the valve stem;
Figure 20 is an eievational view of the driving tool;
Figure 21 is an elevational view of a coupling element, the coupling element forming part of the torque reaction mechanism; and
Figure 22 is a side elevational view of the coupling element.
Best Modβ(s) for Carrying Out the Invention
The embodiment is directed to torque reaction mechanism for use with apparatus 10 for modifying a conventional long stem drain valve 11 to convert it into a valve having provision for selectively performing the functions of valve opening, valve closing, valve unlocking, and valve locking.
The torque reaction mechanism according to the embodiment comprises a coupling arrangement 170 operable between the apparatus 10 and a powered driving tool 160 for delivering rotational torque to a rotary drive input of the apparatus, as will be explained in more detail later.
Before describing the apparatus 10, it is necessary to consider the conventional drain valve 11 which is to be modified by way of the apparatus. The description of the conventional drain valve 11 will be made with reference to Figure 1.
The conventional drain valve .11 comprises a valve body 13 having an inlet 15, an outlet 17 and a flow path 18 from the inlet 15 to the outlet 17. The body 13 incorporates an annular valve seat 19 adjacent the inlet 15. A valve member 21 is movable into and out of sealing engagement with the valve seat 19 for closing and opening the flow path 18 extending between the inlet 15 and the outlet 17. The valve member 21 comprises a valve stem 23 and a valve disc 25 supported on one end of the valve stem, the valve disc 25 being adapted for sealing engagement with the valve seat 19. The valve stem 23 extends through an opening in the valve body 13 and is supported within a yoke 27 mounted on the valve body 13. The yoke 27 rotatably supports a yoke bush 29 through which the valve stem 23 passes. The yoke bush 29 has a portion 30 incorporating an internal screw thread which engages with an external screw thread on the valve stem 23.
The outer end of the valve stem 23 is fitted with an operating handle 33. Specifically the outer end of the valve stem 23 has a drive spigot 24 with which the operating handle 33 drivingly engages. The operating handle 33 is retained in position by retaining nut 34.
A locking handle 35 is connected to the yoke bush 29. The locking handle 35 has a central hub portion 36 which fits onto a portion 32 the yoke bush 29 and is fixed thereto by a key 37. A lock nut 38 engages the yoke bush 29 to retain the locking handle 35 in position. A lock washer 39 locks the nut 38 in position.
Modification of the conventional valve 11 to accommodate the apparatus 10 first involves removal of the operating handle 33, the locking handle 35, the lock nut
38, the key 37, and the lock washer 39. The operating handle 33, the locking handle 35, and the lock washer 39 are discarded, and the lock nut 38 and the key
37 retained for subsequent use with installation of the apparatus 10. Once these parts of the conventional valve 11 have been removed to provide a stripped version of the valve, various parts of the apparatus 10 are then fitted, as will be described later. With the operating handle 33 removed, drive spigot 24 on the free end of the valve stem 23 is exposed.
The apparatus 10 comprises an operating mechanism 40 which includes a gear assembly 41 and a mounting means 43 incorporating two mounting plates 45, 47 The operating mechanism 40 has provision for restraining the valve stem 23 against rotation while allowing axial movement, as will be explained in more detail later.
The gear assembly 41, which is best shown in Figure 2, includes a gear train 61 supported on a base plate 63. The gear train 61 includes a hub 65 adapted to be mounted onto the yoke bush 29, the latter having been retained on the valve stem 23 in the stripped valve 11. The hub 65 is fixed against rotation with respect to the yoke bush 29 by yoke key 37 (which was also retained from the original valve). The hub 65 has a peripheral flange 69 which is configured as a spur gear 71. The yoke bush nut 35 (from the original valve) retains the hub 65 in position
on the yoKe bush 29. The yoke bush nut 35 is retained in position by lock washer
77.
The gear train 61 further comprises an operating gear 91 in meshing engagement with the spur gear 71. The operating gear 91 is configured as part of a first rotatable element 93. The first rotatable element 93 is also configured to provide an intermediate gear 95 and a shaft section 97 which is rotatably supported within a support sleeve 99 attached to the opposed side of the base plate 63. A bush 101 of appropriate low-friction material is provided between the shaft section 97 and the support sleeve 99.
The first rotatable element 93 has an axis of rotation and two axial end sections 102, one of which is configured to define a first operating drive input 103 and the other of which is configured to define a second operating drive input 105. The first operating drive input 103 comprises an operating drive socket 104, and the ' second operating drive input 105 comprises an operating drive socket 106. In this embodiment, the two operating drive sockets 104, 106 are each configured as a female square drive facility.
The intermediate gear 95 is in meshing engagement with a pinion 111 which forms part of a second rotatable element 113. In the arrangement shown, the second rotatable element 113 is assembled from two parts adapted to interconnect to provide a driving connection therebetween. The second rotatable element 113 has a shaft section 114 which is rotatably supported within a support sleeve 116 mounted on the base plate 63.
The second rotatable element 113 has an axis of rotation and two axial end sections 115, one of which is configured to define a first unlocking drive input 117 and the other of which is configured to define a second unlocking drive input. 119. The unlocking drive input 117 comprises an unlocking drive socket 118, and the unlocking drive input 119 comprises an unlocking drive socket 120. In this embodiment, the two unlocking drive sockets 118, 120 are each configured as a female %" drive facility.
Each unlocking drive socket 118, 120 operates through a ratchet mechanism 121 which provides for torque transmission in a direction corresponding to valve unlocking only. The ratchet mechanism 121 is arranged to transmit rotational torque to the second rotatable element 113 (and hence to the pinion 111) upon rotation in one direction (to unlock the valve) and to free-wheel upon rotation in the other direction so as not to transmit any rotational torque to the second rotatablθ element 113.
The gear train 61 thus drivingly connects both the operating drive sockets 104, 106 and the unlocking drive sockets 118, 120 to the yoke bush 29.
Either one of the two unlocking drive sockets 118, 120 can be used for unlocking the valve; that is, to move the valve member 21 into a "just open" or throttled position (in which the valve disc 25 is out of sealing engagement with the valve seat 19) without rotation of the valve stem 23.
Further, either one of the two operating drive sockets 104, 106 can be used for opening and closing the valve, as well as valve locking.
The separate unlocking drive sockets 118, 120 are provided for unlocking the valve as greater torque is required for that operation. By way of explanation, the torque required to rotate the yoke bush 29 in order to unlock the valve from the closed condition can be significantly greater than the torque required to open and close the valve (including locking the valve in the closed condition to effect sealing engagement). In order to accommodate the different torque requirements, the gear ratio between the yoke bush 29 and the unlocking drive sockets 118,120 is different from the gear ratio between the yoke bush 29 and the operating drive sockets104, 106. More particularly, the presence of the pinion 111 and intermediate gear 95 in which it is meshing engagement provide the additional torque requirements. The ratchet mechanisms 121 associated with the unlocking drive sockets 118, 120 to ensure that they can only be used for unlocking the valve. Because the ratchet mechanisms 121 do not transmit rotational torque when the unlocking drive sockets 118, 120 are rotated in the other direction, the unlocking drive sockets cannot be utilised for locking the valve. This is a safety
feature, as us© of the unlocking drive socket 119 to lock the valve could exert such a compression force between the valve member 21 and the valve seat 19 that extreme torque may be necessary in order to subsequently unlock the valve (having regard to the fact that torque requirements to unlock a valve are significantly greater than the torque requirements for locking a valve).
The gear assembly 41 also includes a casing 123 which provides a protective shroud about the gear train 61 ,
The mounting plates 45, 47 are positioned on opposed sides of the yoke 27 and clamped in position by way of clamping bolts 131. As the yoke 27 is a casting, it may be necessary to grind the opposed faces of the casting to ensure that they are sufficiently flat in order to receive the mounting plates 45, 47.
The base plate 63 is attached to the mounting plates 45, 47 in a manner permitting variation to the orientation of the base plate with respect to the mounting plates. In the arrangement shown, the mounting plates 45, 47 each have a mounting flange 48 to which the base plate 63 is releasably attached by means of mounting bolts 125. The mounting bolts 125 pass through aligned bolt holes in the flanges 48 and in the base plate 63. The mounting bolts 125 threadingly engage in holes incorporated in a backing plate 128 which is positioned against the base plate 63. The use of the backing plate 128 avoids the need for a nut for each bolt 125 and thereby makes assembly easier.
The base plate 63 incorporates a plurality of available bolt holes 127 through which the mounting bolts 125 can pass, as best seen in Figure 8. In this way, the orientation of the base plate 63 (and that the operating mechanism 41 attached thereto) can be predetermined according to the particular bolt holes 127 selected for attaching the base plate 63 to the mounting plates 45, 47.
This is particularly advantageous, as it allows the overall apparatus 10 to be oriented in order for the various drive sockets to be conveniently accessible to an operator. Further, it accommodates various orientations of the valve 11.
Further, because there are two operating drive sockets 104, 106 in opposed relation, and also two unlocking drive sockets 118, 120 also in opposed relation, an operator can access the apparatus 10 from either side thereof according to what is more convenient,
As alluded to above, the valve stem 23 is restrained against rotation while allowing axial movement thereto in response to rotation of the yoke bush 29. The restraint is provided by restraint means 130 comprising a first element 131 and a second element 132. The first element 131 comprises a nut assembly 133 threadingly engaging the threaded shank of the valve stem 23. The nut assembly 133 comprises a nut section 135 threaded on the valve stem and a block section 137 fixed to the nut section and also fixed to the valve stem. More particularly, the block section 137 is fixed to the nut section 135 by cap head screws (not shown). The block section 137 is fixed to the rectangular spigot portion provided at the free end of the valve stem 23 such that there is restraint against any relative rotation between the valve stem 23 and the block section 137. The second element 132 cooperates with the first element 131 to allow relative displacement of the first element 131 in a direction corresponding to the axis of the valve stem 23 and to also block rotation of the first element 131 relative to the second element 132 about the axis of the valve stem. The second element 132 comprises a sleeve 141 which is mounted on the casing 123 and within which the block section 137 is accommodated for sljding movement therealong. The sleeve 141 is of rectangular cross-section and the block section 137 is of a matching cross section to allow the sliding movement therealong while being constrained against rotation therein.
The various drive sockets are each adapted to receive a powered driving tool 160 which an operator can use to deliver driving torque thereto. The driving tool 160 can be applied to any one of the operating drive sockets 104, 106 and unlocking drive sockets 118, 120 at the time that rotational torque is required to be delivered thereto. In this embodiment, the driving tool 160 has a square drive spigot 161 for mating engagement with the various drive sockets. While the driving tool 160 can take any appropriate form, it is particularly convenient that it be an air-operated torque gun. In Figures 3 to 6 the driving tool 160 is shown connected to a respective one of the various drive sockets available.
Reaction torque is generated during operation of the powered driving tool 160 and so it is necessary that there be a mechanism for transferring the reaction torque away from the operator of the powered driving tool rather than the operator having to resist the reaction torque.
For this purpose, the operating mechanism 40 further comprises the coupling arrangement 170 according to the embodiment operable between the powered driving tool 160 and the operating mechanism 40 for transferring the reaction torque away from the operator of the powered driving tool. The coupling arrangement 170 according to the embodiment comprises a first (fixed) coupling element 171 associated with each of the operating drive inputs 104, 106 and the unlocking drive inputs 118, 120, and a second (corresponding) coupling element 172 on the powered driving tool 160. The arrangement is such that cooperation between the two coupling elements 171 , 172 is adapted to allow displacement therebetween in the direction corresponding to the axis of rotation of the driving tool 160 while constraining the two coupling elements against relative rotation about the axis of rotation. With this arrangement, reaction torque arising from operation of the powered driving tool 160 is transferred through the coupling element 172 on the tool to the respective fixed coupling element 171. In this way, an operator holding the powered driving tool 160 merely has to guide the tool during its operation and does not have to counteract any reaction torque.
Each first coupling element 171 comprise a sleeve 175 mounted on the casing 123 around the respective drive socket 104, 106, 118, 120. The second coupling element 172 comprise a block 177 which is rigidly mounted on the body 163 of the driving tool 160 and which is adapted to be received in the sleeve 175 for sliding movement therealong. The sleeve 175 is of rectangular cross-section and the block 177 is of a matching cross-section to allow the sliding movement therealong while being constrained against rotation through interaction between the sleeve 175 and the block 177 accommodated therein.
The operator can access the respective drive socket though the hollow interior of the sleeve 175 associated with the drive socket.
In this embodiment, the block 177 comprises a body 179 having a central opening 181 into which part of the body 163 of the tool 160 is received. The opening 181 has splines 183 which engage with matching splines (not shown) provided on the body 163 of the tool, interaction between the splines fixes the block 177 against rotation relative to the tool body 163 which is held by the operator.
With this arrangement, the operator merely needs to insert the tool 160 into the respective sleeve 175 to engage the drive spigot 161 on the tool to the respective drive socket. In doing this, the operator needs to align the block 177 with the sleeve 175 so that the block can enter the sleeve. The block 177 is slidable along the sleeve 175 to allow engagement between the drive spigot 161 on the tool 160 and the respective drive socket, but interaction between the block and the sleeve prevents rotation of the block within the sleeve upon operation of the driving tool (which involves powered rotation of drive spigot on the tool to deliver rotational torque to the drive socket with which the drive spigot is engaged).
In this way, reaction torque generated by operation of the tool 160 is transferred through the interconnection between the block 177 and the sleeve 175 to the casing 123. The interconnection between the bock 177 and the sleeve 175 prevents rotation of the tool body 163 in response to the reaction torque and so alleviates the operator of the need to resist the reaction torque as he or she operates the tool.
It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described.
While the torque reaction mechanism according to the embodiment has been described with reference to operation of rotary drive inputs on a valve operating mechanism, it should be appreciated that the invention may be applicable to any other mechanism having a rotary drive input or indeed any mechanism having a rotatable element to which rotation torques needs to be delivered by a powered driving tool.
Modifications and changes may be made without departing from the scope of the invention.
Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.