GB2420304A

GB2420304A - Open headed two-way ratchet spanner

Info

Publication number: GB2420304A
Application number: GB0510377A
Authority: GB
Inventors: Matteo Mazzeo
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-23
Filing date: 2005-05-20
Publication date: 2006-05-24
Also published as: GB0510377D0; GB0425706D0

Abstract

An open headed ratchet spanner having a two-way ratchet mechanism is provided. The spanner comprises: a handle 2; an open-headed spanner head 3, rotatably connected to the handle 2 about an axis of rotation; a rack comprising ratchet teeth 6 and being joined to the spanner head 3; a single pawl mechanism having a pawl 7; and a controlling mechanism 8 for the pawl 7. The mechanism (figure 12, 8) is such that the pawl 7 can engage with the ratchet teeth 6 to restrict rotational movement of the spanner head 3 relative to the handle 2, so that anticlockwise or clockwise rotation is prevented depending on the state of the controlling mechanism (figure 12, 8). Other modifications may include the use of a chain drive mechanism (figure 14; 17, 18) and bearings (Figure 14, 5).

Description

S -1- 2420304

OPEN HEADED TWO-WAY RATCHET SPANNER

The present invention relates to an open headed two-way ratchet spanner The term "spanner" refers to a device intended to turn a nut or the head of a bolt It should be taken to include all types of spanners (or "wrenches" as the term is used in the USA) The spanner of the present invention is equipped with a two-way ratchet and paw! mechanism that enables rotation of the spanner head relative to the spanner hand!e to be restricted such that in the one case anti-clockwise rotation is allowed and clockwise rotation is prevented, and in another case clockwise rotation is allowed and anti-clockwise rotation is prevented Various mechanisms for effecting this two-way ratchet and pawl mechanism are described.

Hand tools such as drivers for socket sets with two way ratchet mechanisms are known. This type of tool has a handle and a short shaft rotatably attached to a head allows connection of sockets of varying sizes to the head This shaft is connected to a ratchet mechanism which allows rotational movement of the shaft relative to the head to be restricted In some cases, such as US 5,178,047 and US 1,957,462, the shaft is directly attached to the ratchet wheel and there is a pawl in a recess in the hand!e The devices disclosed in these documents are shown in Figure 1 and Figure 2 respectively In these devices the pawl is provided with two pairs of teeth disposed so that in a first paw! position one pair of teeth may be brought into engagement with the ratchet wheel when it is desired to prevent rotation of the wheel in one direction, and in a second pawl position the other pair of teeth may be brought into engagement with the ratchet wheel when it is desired to prevent rotation of the wheel in the opposite direction A sprung retaining means is provided to hold the pawl in engagement with the ratchet wheel The user is able to move the pawl from one position to the other by rotating a lever. The sprung retaining means engages with one of two recesses provided on the pawl to ensure that the paw! sits securely in the first or second position.

In other cases, such as US 3,337,014, the ratchet teeth are formed on the interior of a recess in the spanner head, and the pawl is connected to the rotatable shaft and sits within the ratchet. As shown in Figure 3, in the device disclosed in US 3,337,014 the pawl has a set of teeth at each end and is pivoted at its centre so that the teeth can engage with the ratchet teeth to restrict the movement of the shaft relative to the head. A sprung plunger presses against a camming surface on the pawl and rotates the paw! to bring one of the sets of pawl teeth into contact with the ratchet teeth The plunger orientation can be changed by the user to reverse the direction in which movement of the shaft relative to the head is restricted Two-way ratchet mechanisms for closed headed spanners are also known. In contrast to the socket set driver, these spanners have a hole or recess in the head with a shape and size designed to fit onto a nut or bolt Typically, the hole is formed in the ratchet wheel itself, which is rotatably connected to the handle US 5,857,390 discloses a spanner of this type with a ratchet and pawl mechanism similar to that in US 5,178,047 and US 1,957,462 as discussed above, see Figure 4 US 6,282,992 discloses a spanner of this type with an alternative type of ratchet and paw! mechanism. This is shown in Figure 5. The device disclosed in this document has a ratchet wheel with a hole through its centre for engaging with a fastener (such as a nut) The ratchet wheel is rotatably mounted in the head of the spanner, and has teeth around its exterior A crescent shaped pawl is mounted in a recess in the web between the handle and the head, and has teeth on one side for engaging with the ratchet teeth, and a cavity on the opposite side to the teeth Two V- shaped channels are defined between the sides of the recess and the circumference of the ratchet wheel A spring is engaged at one end in the cavity in the pawl, and at the other end in a rotatable mount To prevent the ratchet from turning clockwise, the spring is turned using the rotatable mount so that it pushes the pawl toward the clockwise channel. If the ratchet is turned clockwise then the pawl is wedged within the channel between the ratchet and the side wall of the recess As the pawl teeth are engaged with the ratchet teeth the ratchet cannot turn clockwise, but anti-clockwise rotation is possible as the pawl can be pushed back against the spring allowing the ratchet teeth to pass the paw! teeth. To prevent the ratchet from turning anti - clockwise, the spring is turned so that the pawl is pushed toward the anti-clockwise channel Open headed spanners are those with a head that is open on one side The opening can be big enough to clear the flats of a hexagonal nut or bolt so that the spanner can be placed to engage the flats of the nut from side on, i e in a radial direction rather than in an axial direction, or the opening may only be large enough to clear the thread on which the nut is fixed US 6,810,773 and GB 1 454 776 disclose examples of such a spanner with a larger opening and a one way ratchet mechanism The spanner head can be fitted onto a nut, the handle moved to tighten the nut, and then the handle can be moved back along the ratchet mechanism and the nut can be tightened again without removing the spanner head from the nut Continued operation of the ratchet beyond a certain point is not possible as the ratchet is formed only along part of the outer surface of the spanner head Therefore the nut can only he tightened so far using the ratchet before the spanner head needs to be removed from the nut and the ratchet re- set The device disclosed in GB 1 454 776 is shown in Figure 6 Open ended spanners with a continually operable ratchet are disclosed in WO 00/09293, US 6,318,215, GB 2 197 234 and US 5,388,479 Various different one- way ratchet mechanisms are used In US 6,3 18,215, as shown in Figure 7, this is achieved by a number of small sprockets, one side of which engages the ratchet teeth, and the other side a pawl. Each sprocket has its own pawl This arrangement ensures that there is always contact between some of the sprockets and the ratchet, and allows the opening in the spanner head to be relatively large In GB 2 197 234 a simpler pawl mechanism is used, consisting of a pawl with saw teeth biased by a spring to 1 5 contact saw teeth on the ratchet. This device is shown in Figure 8. In this case the size of the opening in the spanner head is limited by the width of the pawl as this restricts the size of the portion that may be removed from the ratchet wheel.

In US 5,388,479, as shown in figure 9, an alternative type of pawl mechanism is used in an open headed ratchet spanner In the device disclosed in this document, the ratchet teeth are on the upper or lower outer edge of the spanner head, instead of on the circumference as in the other prior art discussed above The pawl is a crescent shape and is placed axially of the spanner head, rather than radially as in the other systems discussed above The paw! is biased by a spring so that teeth on the pawl engage with those on the ratchet wheel A cam or pin can be used to move the pawl away from the ratchet teeth and allow free rotation of the spanner head This document also discloses a two-way movement, as shown in Figure 10 This two-way device uses two separate pawis, one on the upper edge of the spanner head, and one on the lower edge, and two corresponding sets of ratchet teeth formed on the spanner head By engaging or releasing the pawis the spanner head movement can be restricted to be anti-clockwise or clockwise only. In both the single and double ratchet mechanisms the spanner head can rotate continually, and as the pawl extends a large distance around the edge of the spanner head the opening in the spanner head can be large A problem with closed headed spanners and socket set devices is that they require easy access to the end of the nut or bolt or of the thread to which it is attached.

If access is restricted, then it becomes difficult or impossible to use the tool because the closed head devices must be placed onto the nut axially. This problem also occurs when the nut is mounted on a pipe and there is no access to either end of the pipe.

Furthermore, it may not be possible to use socket sets if too long a length of thread protrudes from the nut, as there may not be sufficient clearance inside the socket In contrast, if an open headed spanner is used then the opening in the spanner head allows it to pass over a thread or a pipe, or if the opening is large enough, allows it to fit directly onto the flats of a nut approaching from the radial direction Thus access along the axial direction of the nut or bolt is not required As can be seen from the above discussion of the prior art, open headed spanners with one-way ratchet mechanisms are known Having a ratchet is advantageous as it allows the nut or other fastening to be turned a greater distance without the need for the spanner head to be removed from the nut. Ratchet mechanisms allowing the spanner head to rotate 3600 so that continuous tightening can occur are known, but these devices are usually complex or difficult to manufacture Two-way ratchet mechanisms are used in some closed head spanners but are particularly known in drivers for socket sets By adjusting a lever or similar the direction of motion of the ratchet can be reversed This allows a nut or bolt to be tightened or loosened without the need for a different orientation of the spanner head Thus the need to place the spanner head onto the nut in a specific orientation is avoided. Additionally, the user can switch from tightening to loosening with the spanner head on the nut, for example if the nut has been over-tightened. 1-lowever, despite the numerous uses of two-way ratchets in socket sets and closed head spanners, the two-way ratchet mechanisms do not appear to have been incorporated into open head spanners apart from in US 5,388,479 as discussed above In the known one- way continually rotatable pawl mechanisms as discussed above, it is difficult to have a large opening in the spanner head, as the size of the opening is limited by the interaction between the ratchet and the pawl. In order to overcome this problem multiple contact points are used between the ratchet and other elements In WO 00/09293 this is achieved by means of two levers with teeth that engage with the ratchet teeth If the opening in the spanner head is adjacent to one of the levers, then the other lever still has contact with the ratchet in US 6,318,215 as discussed above, a number of sprockets maintain contact with the ratchet However, despite the range of known mechanisms, only US 5,388,479 considers the possibility of enabling continual rotation of the spanner head in both directions.

As discussed above, US 5,388,479 discloses an open headed ratchet spanner capable of continual rotation of the spanner head in either direction A problem with this known open headed two-way spanner is that the mechanism is bulky and complex and requires the use of two separate pawls, one on either side of the ratchet Additionally, as the pawis are placed axially of the ratchet, the spanner head is especially bulky along the rotational axis of the spanner head Thus, if access to the full axial depth of the nut is restricted, such as in the case where the nut is closely positioned a plate, then this device may not be able to operate effectively due to the extra bulk of the pawis There is therefore a need for an open headed ratchet spanner capable of two - way movement, with a simple and less bulky mechanism It would also be advantageous to have such a spanner which is capable of continual rotation of the spanner head It would also be advantageous to have an open headed ratchet spanner that could be used with a range of different sizes of nut Viewed from a first aspect the present invention provides an open headed ratchet spanner having a two-way ratchet mechanism comprising: a handle, an open headed spanner head which is rotatably connected to the handle about an axis of rotation, a rack comprising ratchet teeth and being joined to the spanner head, a single pawl mechanism having a pawl, and a controlling mechanism for the pawl, wherein the pawl can engage with the ratchet teeth to restrict rotational movement of the spanner head relative to the handle such that anticlockwise or clockwise rotation is prevented depending on the state of the controlling mechanism.

As there is just a single pawl mechanism having a single piece pawl that controls the rotation in both directions, the construction of this spanner is simpler than the prior art two-way open headed spanner of US 5, 388,479 A reduced number of moving parts are required Thus manufacture is cheaper and easier, there is less risk of mechanical faults, and the spanner as a whole can be smaller and more compact The features of an open headed spanner head and a two-way ratchet have the advantages as discussed above The ratchet teeth preferably extend substantially in a radial direction from the axis of rotation in a plane perpendicular to the axis In this way, the pawl may be placed radially of the ratchet. This allows the spanner head to be thin along its rotational axis, and enables better access to thin or obstructed fastenings.

In a preferred embodiment the ratchet teeth are on a portion of the circumference of the spanner head, and the pawl is attached to a pivot placed radially of the spanner head, wherein the pawl interacts with the ratchet teeth by rotating about the pivot. In one embodiment, the ratchet teeth are provided on a circumferential region of the perimeter extending over a section between 90 - 180 preferably about 120 In another embodiment, the ratchet teeth extend around the entire available circumferential perimeter from jaw to jaw of the spanner In a preferred embodiment the controlling mechanism comprises a pivotally mounted pawl and at least two releasable stopping members, the paw! is biased such that at rest an engaging end of the pawl extends from the pivot toward the centre of the spanner head and engages with the ratchet teeth, a first releasable stopping member that prevents the pawl from rotating clockwise to restrict rotation of the spanner head in one direction, and a second releasable stopping member that prevents the pawl from rotating anti-clockwise to restrict rotation of the spanner head in the opposite direction In this embodiment restricting the direction of rotation of the spanner head is achieved by releasing or engaging the stopping members Releasing both stopping members allows free movement of the spanner head in both directions and engaging both restricts rotation of the spanner head in both directions Preferably, the stopping members comprise pins that are mounted to be displaced in a direction which is substantially parallel to the axis of rotation of the spanner head.

The paw! mechanism is simple and consists of only three moving parts in its most basic form; the rotating paw! and two stopping members A reduced number of parts leads to higher reliability compared to a more complex system. Furthennore, there is no need for very accurately shaped components, as this mechanism does not rely on a closely toleranced interaction of the parts Thus, this mechanism is easy to manufacture and assemble Preferably, the stopping members can block movement of the pawl from its resting position, so that with one stopping member in place and the other released rotation of the spanner head in one direction will be prevented by the ratchet teeth Pushing against the engaging end and the pawl pushing against the stopping member, whereas rotation of the spanner head in the opposite direction is able to occur as the pawl rotates so that the ratchet teeth can pass the engaging end In another preferred embodiment the controlling mechanism comprises a plunger which is biased to extend toward the pivot, and a camming surface on the pawl which contacts the plunger, the pawl has a first engaging end extending from the pivot toward a clockwise portion of the spanner head, and a second engaging end extending from the pivot toward an anti-clockwise portion of the spanner head, wherein the plunger can act on the camming surface to bias the pawl to rotate such that either the first engaging end engages with the ratchet teeth to prevent anti- clockwise rotation of the spanner head, or the second engaging end engages with the ratchet teeth to prevent clockwise rotation of the spanner head In this embodiment the pawl mechanism requires only two moving parts; the rotating pawl and the plunger A reduced number of parts leads to higher reliability compared to a more complex system Furthermore, there is no need for very accurately shaped components, as this mechanism does not rely on a closely toleranced interaction of the parts Thus, this mechanism is easy to manufacture and assemble Preferably, the camming surface includes recesses, the plunger can sit in a first recess to bias the pawl to rotate such that the first engaging end engages with the ratchet teeth or the plunger can sit in a second recess to bias the pawl to rotate such that the second engaging end engages with the ratchet teeth S -Il- There may be a recess which allows the plunger to bias the paw! to be in a position where neither engaging end engages with the ratchet teeth In a preferred embodiment the ratchet teeth are on the circumference of the spanner head, the paw! is placed radially of the spanner head and the spanner comprises a chain drive, which engages with the ratchet teeth along a length of the circumference of the spanner head. The chain preferably loops round along a curved route positioned radially outward of the spanner head. The paw! is able to "engage" with the ratchet teeth by engagement of the pawl with the chain The use of a chain in this way allows a simple pawl mechanism to be used in a two-way ratchet spanner where the spanner head is capable of continual rotation in either direction The chain ensures a positive connection with a portion of the ratchet teeth at all times and it can be used with any suitable paw! mechanism. As the chain can contact a large extent of the circumference of the spanner head, the opening in the spanner head can be widened compared to known devices. In fact, contact between the chain and the ratchet teeth at either side of the opening will not be lost unless the opening is larger than the extent of the chain, allowing the opening to extend around the circumference of the spanner head for greater than 90 and preferably up to 135 The large contact length between the ratchet teeth and the chain allows greater forces to be transmitted without overloading the teeth or the chain.

The opening is preferably wide enough to fit over the flats of a nut so that the nut can be approached in the radial direction The size of the nut that can be fitted in this way is limited by the diameter of the spanner head, and the width of material necessary between the edge of the recess for the nut and the ratchet teeth, but it will he appreciated that the device can be scaled up to fit larger nuts or other fastenings In a preferred embodiment the chain is supported by a plurality of sprockets placed around the circumference of the spanner head The chain mechanism may be housed in a recess in the handle of the spanner The spanner head in the embodiments described above may comprise an adjusting mechanism to change the size of the opening so that the spanner head can fit different sized fastenings This mechanism may be any conventional mechanism, as used on known adjustable open headed (non-ratchet) spanners Alternatively, the spanner head may be shaped to fit inserts, and the inserts may have recesses to fit a wide range of nut and other fastenings or varying sizes.

The spanner head in the embodiments described above may be supported by a bearing. There may be a bearing on either side of the spanner head The spanner handle in the embodiments described above may have a hinge which allows the spanner head to be placed in different orientations relative to the handle Preferably the hinge extends in a direction perpendicular to the axis or rotation of the spanner head.

Preferred embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which.

Figure 1 shows a prior art two-way ratchet in a driver for a socket set; Figure 2 shows an alternative prior art arrangement to that in Figure 1, Figure 3 shows a prior art two-way ratchet with the ratchet teeth are formed on the interior of a recess in the spanner head; Figure 4 shows a prior art closed headed spanner with a two way ratchet; Figure 5 shows a prior art closed headed spanner with an alternative two way ratchet mechanism, Figure 6 shows a prior art open ended spanner with a one-way ratchet having limited movement, Figure 7 shows a prior art open ended spanner with a one-way ratchet which is able to continually rotate, Figure 8 shows an alternative prior art open ended spanner with a one-way ratchet which is able to continually rotate; Figure 9 shows an alternative prior art open ended spanner with a one-way ratchet which is able to continually rotate; Figure 10 shows a prior art open ended spanner as in Figure 9, with two pawis allowing a two way ratcheting movement; Figure 11 shows a preferred embodiment of the present invention, having a two-way ratchet and ratchet teeth extending around only part of the spanner head, Figure 12 shows a preferred ratchet mechanism, Figure 13 shows an alternative preferred ratchet mechanism; Figure 14 shows a preferred embodiment with bearings supporting the spanner head, and a chain engaging with the ratchet teeth; Figure 15 shows bearings supporting the spanner head, and a hinge in the handle; and Figure 16 shows a spanner head with an adjustable opening Figure 11 shows an open headed ratchet spanner having a two-way ratchet mechanism 1. The spanner has a handle 2 and an open headed spanner head 3 rotatably connected to the handle 2 by connection 4. On the circumference of the spanner head 3 a rack is formed having a number of ratchet teeth 6 A single pawl mechanism 7 is placed radially of the rack, and engages with the ratchet teeth 6 to restrict rotational movement of the spanner head relative to the handle such that anti - clockwise or clockwise rotation is prevented depending on the state of the controlling mechanism 8, which Figure 1 does not show in any great detail In this embodiment the spanner head 3 is connected to the handle 2 by a pin The spanner head 3 could simply rotate around the pin 4, with the rack formed as a locus about the pin 4, or the spanner head 3 can have a slot allowing it to rotate about a centre of rotation closer to the axis of rotation of the nut In this embodiment, the slot forms a track which guides the pin. In some embodiments, the spanner head 3 is supported by bearings 5 Bearings are advantageous as they allow a smooth and controlled motion of the spanner head, and will operate effectively even when large forces are applied.

The spanner shown in figure 11 has only a small number of moving parts, which makes it easy to manufacture. As the pawl 7 is placed radially of the spanner head 3, the head of the device can be thin along its rotational axis, and this enables better access to thin or obstructed fastenings.

In Figure 12 a preferred embodiment of the ratchet mechanism 1 is shown. In this embodiment there is a controlling mechanism 8 in which the pawl 7 is mounted on a pivot 9 and there are two releasable stopping members 10, 11 Springs 12, 13 bias the paw! 7 such that in a resting position an engaging end 14 of the pawl 7 extends from the pivot 9 toward the centre of the spanner head 3 and engages with the ratchet teeth 6 When the first stopping member 10 is in place it prevents the pawl 7 from rotating clockwise, and therefore prevents the spanner head 3 from rotating anticlockwise When the second stopping member 11 is in place it prevents the pawl 7 from rotating anti-clockwise and therefore prevents the spanner head 3 from rotating clockwise.

The stopping members 10, 11 are pins that are mounted to be displaced in a direction which is substantially parallel to the direction of the axis of rotation of the spanner head 3 They can be engaged and released by any known mechanism, such as spring biased catches, and can be released by the user The stopping members 10, 11 could be removed completely from the spanner when they are released, but preferably they remain connected to avoid them being lost or damaged Releasing both stopping members 10,11 allows free movement of the spanner head 3 in both directions and engaging both restricts rotation of the spanner head 3 in both directions As can be seen, the ratchet and pawl mechanism 1 is simple and consists of only three main moving parts, the rotating paw! 7 and two stopping members 10, 11 In this embodiment the stopping members 10, 11 block movement of the paw] 7 from its resting position, so that with one stopping member in place and the other released rotation of the spanner head 3 in one direction will be prevented by the ratchet teeth 6 pushing against the engaging end 14 and the pawl pushing against the stopping member, whereas rotation of the spanner head 3 in the opposite direction is able to occur as the pawl 7 rotates so that the ratchet teeth 6 can pass the engaging end 14 The spring pushes the pawl 7 back toward the resting position Thus, movement of the spanner head 3 is well controlled, and there is limited slack movement in the system.

The paw! has a surface that extends substantially perpendicular to a line going from the pivot 9 to the engaging end 14, and the stopping members 10, 11 are placed to contact with this surface.

Other arrangements of the stopping members 10, 11 and the paw! are of course possible The paw! 7 could be elongated and substantially rectangular or lozenge shaped, with the pivot 9 connected at one end or in the centre, and the stopping members 10, 11 could be on either side of the paw! 7 above or below the pivot 9 re!ative to the spanner head 3 Figure 13 shows another preferred embodiment of the ratchet and pawl mechanism 1 In this embodiment the controlling mechanism 8 has a plunger 15 which is biased by a spring 16 to extend toward a pivot 9 The pawl 7 has a camming surface which contacts the plunger 1 5 and allows the plunger 1 5 to set the pawl 7 in two different positions. The paw! 7 can contact the ratchet teeth 6 at two points A first engaging end 14 extends from the pivot 9 to the left in figure 13, i e following a clockwise direction of rotation of the spanner head 3 and extending toward a clockwise portion of the spanner head 3. A second engaging end 142 extends from the pivot to the right in figure 13, i.e. following an anti - clockwise direction of rotation of the spanner head 3 and extending toward an anti-clockwise portion of the spanner head 3. The camming surface in this embodiment has a central protrusion with a recess on either side. The plunger 15 takes the form of a ball which is pushed toward the pawl 7 by the spring 16, and can rest in a stable position on either side of the protrusion. Thus the plunger 15 will act on the side of the protrusion to push the pawl 7 either clockwise or anti-clockwise. When the plunger 15 is in the recess on the left of the protrusion, as shown in figure 13, it pushes the paw! 7 anti-clockwise and the second engaging end 142 engages with the ratchet teeth 6 This prevents clockwise rotation of the spanner head 3 To change the direction of operation of the ratchet and pawl mechanism I the paw! 7 is rotated clockwise, the protrusion pushes the plunger back against the spring 16, and when the plunger 15 has slid passed the protrusion it sits in the right hand recess. In this orientation the plunger 15 pushes the pawl 7 clockwise and the first engaging end 141 engages with the ratchet teeth 6 to prevent anti-clockwise rotation of the spanner head 3 As can be seen in figure 13, the pawl mechanism requires only two main moving parts; the rotating paw! 7 and the plunger 15 In another embodiment, there is arecess that allows the plunger 15 to bias the paw! 7 to be in a position where neither engaging end 1412 engages with the ratchet teeth 6 If this feature was added to the embodiment shown in figure 13 then the protrusion would become a "W" shape with the neutral recess located between the left and right recesses.

In the embodiments shown in figures 11, 12 and 13 the ratchet teeth 6 are on only part of the circumference of the spanner head 3 In figure 11 for example, the ratchet teeth 6 extend around about 120 of the circumference, and thus the spanner head 3 can rotate about 120 along the ratchet. In alternative embodiments, the ratchet teeth 6 extend around the entire available circumferential perimeter from jaw to jaw of the spanner If this is the case then the spanner head 3 can rotate on the ratchet for as long as the ratchet teeth 6 extend around the circumference of the spanner head 3 Once the pawl 7 reaches the opening in the spanner head 3 there are no ratchet teeth and the spanner head will be able to rotate freely in either direction.

In this instance if the connection between the spanner head 3 and the handle 2 allows it, then 360 rotation of the spanner head 3 is possible However, to regain ratchet control of the rotation the handle 2 needs to be rotated relative to the spanner head 3 past the point where the pawl 7 is in the opening, so that the paw! can engage with the ratchet teeth 6 on the other side of the opening This is not an ideal situation, as there is no control of rotation when the pawl 7 is in the opening in the spanner head 3 Additionally, there will be situations where it is not possible to turn the handle far enough to re-engage the paw! 7 on the other side of the opening.

Figure 14 shows an embodiment that overcomes these problems The figure shows in exploded view the spanner head 3 and a chain drive 17, which engages with the ratchet teeth 6 along a length of the circumference of the spanner head 3 The chain 17 in figure 14 is not completely drawn in, but you can see that it loops round along a curved route positioned radially outward of the spanner head 3 toward the grip of the handle 2, which would be downward from the spanner head 3 as seen in figure 14 The pawl 7 interacts with the ratchet teeth 6 by engaging with the chain 17 This engagement could happen at the point P shown in figure 14 The chain 17 allows a simple paw! mechanism to be used in a two-way ratchet spanner where the spanner head 3 is capable of continual rotation in either direction, without any loss of control. The chain 17 ensures a positive connection with a portion of the ratchet teeth 6 at all times and it can be used with any paw! 7 The paw! 7 is always in contact with the chain 17 and so control is maintained at all times As can be seen in figure 14, contact between the chain 17 and the ratchet teeth 6 at either side of the opening will not be lost unless the opening is larger than the extent of the chain 17. In figure 14 the opening in the spanner head 3 is about 120 of the circumference and is wide enough to fit over the flats of a nut, the nut in this case having a diameter of about 1/2 of the diameter of the spanner head 3 The chain 17 extends around about 240 of the circumference of the spanner head 3 Thus only about half of the extent of contact between the chain 17 and the ratchet teeth 6 is lost when the chain 17 bridges the opening The chain 17 is supported by a plurality of sprockets 18 placed around the circumference of the spanner head In figure 14 bearings 5 support the spanner head 3 from either side This prevents tilting or wobbling movement of the spanner head 3 out of its plane of rotation, and ensures smooth motion of the spanner head 3 when force is applied The bearing 5 is placed between the spanner head 3 and a suitably formed mounting at the top of the handle 2 The chain mechanism would be housed in a recess also formed at the top of the handle 2 Similar bearings 5 to those shown in figure 14 could be used with ratchet and pawl mechanisms I that do not include the chain 17 In the embodiments described above the engaging end 14 and engaging ends 141,2 of the pawl 7 are not described in any detail These portions can be contoured where they contact the ratchet teeth 6 or the chain 17, for example in an involute profile. As is known in the art, suitable profiling of parts that connect under force in this way can reduce wear and stresses, and extend the working life of the parts The ratchet teeth 6 would therefore have a conesponding profile where they contact the chain 17 or the pawl 7 The pawl and the ratchet teeth should be made of a suitably strong and hard wearing material The paw! and the ratchet teeth could be made of the same material or a different material. Suitable materials include toughened steels with hardened contact surfaces, such as tool steels having additions of Mn, Cr, Mo, V and/or Co, for

example

Figure 1 5 shows an additional feature, which could be used with some of the embodiments described above. An adjusting mechanism 19 can be used to change the size of the opening so that the spanner head 3 can fit different sized nuts As shown in figure 15 this mechanism can be a conventional mechanism, as used on known adjustable open headed (nonratchet) spanners.

In an alternative embodiment the spanner head 3 is shaped to fit inserts with openings to fit a wide range of nuts This arrangement could be used with a continually rotating spanner head 3 Figure 16 shows a further embodiment, with a hinge mechanism 20 in the handle 2 which allows the spanner head 3 to be placed in different orientations relative to the handle 2 This means that nuts or bolts which are not accessible directly can be tightened or loosened easily from above or below, without any significant loss of control. Figure 16 also shows a spanner head 3 mounted on bearings 5. This spanner head 3 has an opening that extends around 90 of its circumference, and if a chain 17 was used, it could extend around 220 or more of the circumference. Therefore in this case less than half of the contact between the chain 17 and the ratchet teeth 6 would be lost when the opening was on the chain 17.

Figure 16 does not show the ratchet and pawl mechanism 1, but any of the mechanisms described above could be used.

Although not shown in any detail in figures 11 to 16, the ratchet and pawl mechanism I is preferably housed in a recess in the handle 2. Covering the moving parts reduces the risk of injury to the user or damage to the parts. However, a removable cover could be provided to allow access to clean or maintain the mechanism As will be appreciated from the foregoing, the invention provides, at least in its preferred embodiments, a spanner with a two-way ratchet mechanism which is slim, lightweight, and manoeuvrable. It can be easily used in awkward places for both tightening and unscrewing nuts, bolts and the like The spanner provides accessibility and manoeuvrability along with two way operation, and will therefore be useful in any workplace or manufacturing establishment

S

Claims

An open headed ratchet spanner having a two-way ratchet mechanism corn prising a handle, an open headed spanner head which is rotatably connected to the handle about an axis of rotation, a rack comprising ratchet teeth and being joined to the spanner head, a single pawl mechanism having a pawl, and a controlling mechanism for the pawl, wherein the pawl can engage with the ratchet teeth to restrict rotational movement of the spanner head relative to the handle such that anti- clockwise or clockwise rotation is prevented depending on the state of the controlling mechanism.
2. A spanner as claimed in claim 1, wherein the pawl is placed radially of the rack of ratchet teeth
3. A spanner as claimed in claim I or 2, wherein the ratchet teeth are on a portion of the circumference of the spanner head, the pawl is attached to a pivot placed radially of the spanner head, and the pawl interacts with the ratchet teeth by rotating about the pivot
4 A spanner as claimed in claim 1, 3 or 3, wherein the ratchet teeth are provided on a circumferential region of the perimeter of the spanner head extending over a section of between 9001800
5 A spanner as claimed in claim 4, wherein the ratchet teeth are provided on a circumferential region of the penmeter extending over a section of about 1200
6 A spanner as claimed in claim 1, 2 or 3, wherein the ratchet teeth extend around the entire available circumferential perimeter of the spanner head from jaw to jaw of the spanner.
7 A spanner as claimed in claim 6, wherein the spanner head can rotate 360 .
8. A spanner as claimed in any preceding claim, wherein the controlling mechanism comprises a pivotally mounted paw! and at least two releasable stopping members, the pawl is biased such that at rest an engaging end of the pawl extends from the pivot toward the centre of the spanner head and engages with the ratchet teeth, a first releasable stopping member that prevents the pawl from rotating clpckwise to restrict rotation of the spanner head in one direction, and a second releasable stopping member that prevents the pawl from rotating anti-clockwise to restrict rotation of the spanner head in the opposite direction.
9 A spanner as claimed in claim 8, wherein the stopping members comprise pins that are mounted to be displaced in a direction which is substantially parallel to the axis of rotation of the spanner head
10 A spanner as claimed in claim 8 or 9, wherein the stopping members can block movement of the pawl from its resting position, so that with one stopping member in place and the other released rotation of the spanner head in one direction will be prevented by the ratchet teeth pushing against the engaging end and the pawl pushing against the stopping member, whereas rotation of the spanner head in the opposite direction is able to occur as the pawl rotates so that the ratchet teeth can pass the engaging end.
11 A spanner as claimed in claim 8, 9 or 10, wherein the pawl has a camming surface, and the stopping members are placed to contact with this camming surface.
12. A spanner as claimed in claim 11, wherein the camming surface extends perpendicular to a line going from the pivot to the engaging end of the pawl 13 A spanner as claimed in claim 11, wherein there are two camming surfaces on opposite sides of the paw! 14 A spanner as claimed in any of claims 8 to 13, wherein the pawl is biased by means of one or more springs.

A spanner as claimed in any of claims 8 to 13, wherein the stopping members are radially further from the spanner head than the pivot is 16 A spanner as claimed in any of claims 8 to 14, wherein the stopping members are radially closer to the spanner head than the pivot is 17. A spanner as claimed in any of claims Ito 7, wherein the controlling mechanism comprises a plunger which is biased to extend toward the pivot of the paw! and contacts a camming surface on the pawl, the pawl has a first engaging end extending from the pivot toward a clockwise portion of the spanner head and a second engaging end extending from the pivot toward an anti-clockwise portion of the spanner head, and wherein the plunger can act on the camming surface to bias the pawl to rotate such that either the first engaging end engages with the ratchet teeth to prevent anticlockwise rotation of the spanner head, or the second engaging end engages with the ratchet teeth to prevent clockwise rotation of the spanner head 18 A spanner as claimed in claim 17, wherein the camming surface includes recesses, the plunger can sit in a first recess to bias the pawl to rotate such that the first engaging end engages with the ratchet teeth or the plunger can sit in a second recess to bias the pawl to rotate such that the second engaging end engages with the ratchet teeth.

19 A spanner as claimed in claim 17 or 18, wherein the plunger can sit in a neutral recess in the camming surface, which allows the plunger to bias the pawl to be in a position where neither engaging end engages with the ratchet teeth 20 A spanner as claimed in any preceding claim, wherein the ratchet teeth are on the circumference of the spanner head, the pawl is placed radially of the spanner head, and the spanner comprises a chain drive, which engages with the ratchet teeth along a length of the circumference of the spanner head. I0

21 A spanner as claimed in claim 20, wherein the chain loops round along a curved route positioned radially outward of the spanner head 22 A spanner as claimed in claim 20 or 21, wherein the pawl engages with the ratchet teeth by engaging with the chain 23 A spanner as claimed in claim 20, 21 or 22, wherein the open head of the spanner head defines an opening and the relative size of the opening and the extent of contact between the chain and the ratchet teeth ensures that contact between the chain and the ratchet teeth is maintained when the chain bridges the opening.

24 A spanner as claimed in claim 23, wherein the size of the opening ensures that less than half of the extent of contact between the chain and the ratchet teeth is lost when the chain bridges the opening.

A spanner as claimed in any of claims 20 to 24, wherein the spanner head opening is wide enough to fit over the flats of a nut.

26 A spanner as claimed in any of claims 20 to 25, wherein the chain is supported by a plurality of sprockets placed around the circumference of the spanner head.

27 A spanner as claimed in any of claims 20 to 26, wherein the chain mechanism is housed in a recess in the handle of the spanner.

28 A spanner as claimed in any preceding claim, wherein the pawl is contoured where it contacts the ratchet teeth or the chain 29 A spanner as claimed in any preceding claim, wherein the pawl has a gear tooth profile such as an involute profile where it contacts the ratchet teeth or the chain A spanner as claimed in any preceding claim, wherein the ratchet teeth have a gear tooth profile such as an involute profile 3 1 A spanner as claimed in any preceding claim, wherein the pawl mechanism is in a recess in the spanner handle.

32 A spanner as claimed in any preceding claim, wherein the spanner head comprises an adjusting mechanism to change the size of the opening in the spanner head 33 A spanner as claimed in any of claims ito 31, wherein the spanner head is shaped to fit inserts, and the inserts may have openings of varying sizes and/or shapes.

34 A spanner as claimed in any preceding claim, wherein the spanner head is supported by a bearing A spanner as claimed in any preceding claim, wherein there is a bearing on either side of the spanner head.

36 A spanner as claimed in any preceding claim, wherein the handle comprises a hinge which allows the spanner head to be placed in different orientations relative to the handle 37 A spanner as claimed in any preceding claim, wherein the spanner head can rotate 3600 38. A spanner substantially as hereinbefore described and with reference to figures ii and 12, 11 and 13 or 11 and 14