Patent Description:
Ratchet wrenches may comprise a wrench head that houses a driven member. The driven member may be provided with an aperture shaped to receive an item that is to be driven. For example, the aperture may be a hexagonal aperture sized to receive a particular size of fastener head/nut. Alternatively, the driven member may comprise a spigot that projects from the wrench head to allow the wrench head to be connected to a drive socket or the like. The driven member may have a circumferentially extending surface provided with a series of teeth that are engageable by the teeth of a pawl that is located within a recess within the wrench head. The leading edge of the pawl is generally wedge shaped, as is the ends of the recess that the pawl is situated in. The engagement between the pawl and teeth is such that if the wrench head is turned in a first direction, the rotation of the wrench head is transmitted to the driven member in a locking manner as the pawl is driven into engagement with a ramp surface in the pawl recess. If the wrench head is turned in a second (opposite) direction, the pawl slides over the teeth on the driven member against a spring that is used to urge the pawl against the driven member teeth. The wrench head may have multiple pawls.

By this means the wrench can apply a torque to an item by turning the wrench head in the first direction and the wrench handle can be repositioned with respect to the item by turning the wrench head in the second direction. Wrenches of this type may be provided with a pair of pawls or a pawl with ramps at either ends, the pawl being selectively engageable with the driven member by means of a switch. The torque applying and handle repositioning directions of the wrench can be reversed by operation of the switch.

The majority of current prior art switchable wrench ratchets incorporate a central drive element portion having a circular toothed circumference which engages a corresponding toothed pawl which is appropriately spring biased in the chosen direction by a switch against two appropriately angled wedge ramp faces formed in the ratchet head housing against which the wedge-shaped pawl can be resiliently urged. The switch shaft further incorporates a bore containing a spring and plunger, the plunger is in contact with the back of the pawl opposite its front engagement teeth. The plunger, pawl contact area is formed into an arced cam with end walls such that the rotation of the switch with its incumbent spring and plunger urges the plunger against the end wall from one end wall to the other resiliently projecting the particular pawl wedge shaped outer contact portion against the required housing wedge shaped ramp portion in order to provide a suitable locking function when the ratchet is utilized in the chosen drive direction as the wedging of the pawl usefully urges the pawl teeth against the teeth of the drive portion effectively locking the drive portion within the housing. In the chosen reverse or reposition direction the housing wedge shaped ramp is caused to separate from the pawl wedge shaped ramp by the drive element teeth acting upon the pawl teeth, the switch spring and plunger resiliently urging the pawl teeth against the drive portion teeth, the typical ratchet clicking noise is caused by the corresponding teeth disengaging and engaging as they travel over one another in the reverse direction. In the drive direction the pawl as it is projected against its corresponding housing wedge shaped ramp, however the pawl teeth only truly robustly engage at or near the actual wedge shaped end contact areas, hereinafter termed engagement ramps, equivalent to approximately <NUM> deg. or less of the drive element teeth, the normal point of failure of most ratchets is due to over torque usage, wear or fouling of the ratchet pawl teeth, the more or larger the teeth completely engaged the less the wear or over torque problem. As correctly illustrated in <FIG> <CIT> Hu when a bi-directional pawl is utilized less than half of the pawl teeth completely engage the analogous drive element teeth, furthermore this is also a similar characteristic of single direction ratchets, if the pawl and housing recess engagement ramp angles were to be modified in order to substantially improve the teeth engagement, the pawl would tend to problematically jam against the pawl recess engagement ramp, empirical testing over many years having led to this compromise. The current useable lifecycle of such a ratchet using a prior art pawl is two years in a busy professional automotive workshop environment, the pawl and its spring being classed as a consumable item.

Prior art ratchet wrenches cannot always be utilized in confined spaces because of their required depth or widths preventing sufficient access. <CIT>, <CIT> Buchanan illustrate a switchable direction ratchet mechanism utilizing a pseudo-laminate like construction, a deformable partly toothed clutch ring forming the mid-part of a construction comprising an outer housing and a drive element. This resultant laminate like construction of the drive element, clutch and housing enables an inherently strong reduced depth or alternatively a slightly reduced width ratchet but not both. The clutch ring encompassing the drive element in the drive sequence being propelled inwards upon the drive element by the clutch abutment angles in that particular direction acting upon the corresponding housing ramp contact angles, therefore forcefully constricting the said clutch ring, upon the drive element in a locking manner. The compression and locking force increasing according to the torque applied to the handle portion, the housing inner surface being in equal contact force with the majority of the said clutch outer surface and the said clutch inner surface in equal contact force with the majority of the drive outer surface, thereby substantially distributing the inward and outward forces in a laminate like manner within the housing during use. <CIT>) discloses a similar ratchet mechanism, albeit a single direction one. This design allows a slim ratchet head width, but with a conventional depth.

<FIG>shows a quality prior art ratchet wrench. The teeth <NUM> of the pawl <NUM> are engaged with corresponding teeth <NUM> of a driven member <NUM>. It can be seen that the pawl teeth <NUM> typically only fully engage with the facing teeth <NUM> of the driven member <NUM> at and near the leading edge of the said pawl <NUM>.

It is an object of the present invention to at least partially alleviate the above-mentioned disadvantages, or to provide an alternative to existing products.

A wrench according to the preamble of claim <NUM> is disclosed by <CIT>. The engagement profiles are projections with rounded ends that engage notional ramp surfaces defined by a continuous curved wall. The arrangement of the engagement profiles on the pawl, the curved wall and a spring that biases the engagement profiles into engagement with the continuous arcuate wall is such that pawl can move into and out of engagement with the drive element to provide a ratcheting action in one direction of rotation. The provision of multiple engagement profiles engaging the curved wall spreads the load applied by the pawl so as to prevent stress concentration at only one point on the curved wall.

The invention provides a ratchet wrench as specified in claim <NUM> to <NUM>.

Embodiments of the invention may provide a slimmer profiled ratchet wrench than any other currently available on the market, whilst attaining or exceeding the current torque standards. They may also allow the manufacturers to produce more cost effective and reliable products.

The invention also includes a ratchet wrench comprising a driven member. A housing having an aperture in which said driven member is received, an elongate handle or operating member having a hand grip end and a levered head portion end. The head portion having a generally centrally disposed circular housing, the inner surface of which adjoining the handle portion is provided with a recess comprising a plurality of engagement ramp surface arranged not unlike low angled teeth within the recess arc. A pawl is located within the recess, the pawl has corresponding engagement ramp profiles abutting ramp surfaces and an inner facing toothed face of similar corresponding pitch and profiles as the drive element teeth in order that they can mechanically mesh into one another when operated in the drive direction. The rear pawl face incorporates a flange capable of side movement within a suitable corresponding undercut adjacent said recess for the containment of the pawl flange and the recess undercut further comprising a suitable connection between the switch plunger and the pawl flange biasing profile. The pawl flange biasing profile further incorporates two opposite end stops with a guide face between them. Optionally there is provided a direction biasing switch which may be similar to that in the prior art switch, the switch axle capable of rotation within the head portion switch bore, the switch axle having a further blind cavity cross bore for the sliding fit of the further plunger cylinder and its outwardly biasing plunger spring, the switch being rotatable within an arc allowing the said sprung plunger to be switched as required between the said two pawl end stops in order to bias in the required direction the pawl engagement ramp profiles against the respective ramp surfaces in order to provide clock or anti-clockwise drive directions.

The first embodiment may comprise a head portion comprising a generally circular drive element housing, the inner surface of which adjoining the handle portion having a further recess provided with a plurality of ramp surfaces arranged not unlike low angled gear teeth within the recess arc. A pawl is located within the recess, the pawl having a corresponding plurality of engagement ramp profiles abutting the ramp surfaces and incorporating an inner facing toothed face of similar corresponding pitch and profiles as the drive element teeth in order that they can mechanically mesh into one another when required, the pawl inward force being substantially evenly distributed along the pawl toothed front face by the use of the several similar engagement ramp profiles urging the pawl into the required locking engagement simultaneously. This arrangement usefully allows a superior number of pawl teeth to be capable of full engagement with the drive element teeth during the drive sequence yet with the correct angles chosen and effortless disengagement from the pawl engagement ramp profiles from the ramp surfaces in the reverse or reposition direction. The pawl engagement ramp profiles have a suitable gap from the ramp surfaces during the reverse or reposition action to allow the pawl teeth to adequately disengage from the drive element teeth.

A second embodiment may have corresponding engagement ramp profiles may be arranged not unlike low angled teeth or mirrored in profile in order that the ratchet action can be utilized in both the clockwise or anticlockwise direction.

A third embodiment may have engagement ramp profiles that are single toothed or shark fin like profiled in order that the ratchet action can be utilized in only one direction whereas no switch function is required.

A fourth embodiment of the invention defined by claim <NUM> may have a portion of the head portion housing wall width that can be usefully reduced, in order to provide a useful resiliently deformable wall portion. When the reduced profile ratchet is operated in the drive direction the pawl engagement ramp profiles are projected against the pawl recess engagement profiles further robustly projecting the pawl toothed face inwardly against the annular drive element toothed portion locking the said drive element within the head portion. The present drive element is further designed to be capable of limited lateral movement against the housing inner surface, whereas the drive element toothed portion can robustly contact the said housing inner surface opposing the pawl recess, according to the force applied to levering end of the handle by the operator, the said drive element contact according to the said operator drive force applied usefully deforming the said head portion resiliently deformable wall portion inwardly upon the drive element toothed portion resulting in a further superior clamping force area between the said drive element toothed portion and the opposing housing wall. The drive element may have flat topped teeth as an aid to the further useful locking action so provided between the drive element and the housing inner surface.

A fifth embodiment may have a pawl toothed face circumference angle truly available to effectively and robustly mesh with the drive element toothed circumference is enhanced by the use of the said pawl having a plurality of engagement ramp profiles abutting the correspondingly similar recess engagement ramp profiles. Whereby the true said pawl to said drive element toothed engagement can be substantially improved over that in the prior art from at best <NUM> deg. to <NUM>-<NUM> deg. As the pawl teeth are the major wear or torque failure problem in prior art ratchet wrenches or socket drives this is a most important improvement to the art as it is a major contribution to reducing manufacturing, servicing and warranty costs.

Furthermore, the thickness of the pawl toothed front face to that of its pawl rear face can be further usefully reduced as the pawl is now usefully urged into locking engagement in the drive direction when required by a plurality of engagement ramps over its length instead of singly in the drive direction as in the prior art.

A sixth embodiment may be capable of a usefully low height profile in order to perform in restricted areas unavailable to prior art ratchets. The drive element toothed portion within the housing is substantially the same height as the head portion housing wall. The corresponding pawl toothed front face depth is also is substantially the same height as the head portion housing wall, thereby maximising the pawl to drive element tooth to pawl tooth engagement contact area. The toothed drive element being further located between two thin washer-like flanges, the washer like flanges retain the drive element within the head portion housing whilst usefully allowing the drive element to rotate as required and move latterly according to the tolerances given. A further aid to locking engagement being the tops of the drive element teeth are preferably radiused or near flat topped, the "flat top" being substantially the same circumferential profile as the housing inner sidewall. Furthermore, if the outer radiuses of the drive element teeth have minimal radii, their locking engagement with the smooth housing inner sidewall will be measurably enhanced. This embodiment allows the operation of the present invention in situations unavailable to other prior art production ratchets, whilst still passing the relevant torque standards.

A seventh embodiment may have a usefully reduced width profile in order to perform in restricted areas unavailable to prior art ratchets. As the drive element is no longer held and rotated using axle portions between conventional housing plain bearing surfaces and the drive element is no longer secured by the use of clips within housing grooves there is less of a requirement for a thick housing wall. For example, a high-quality thin profile conventional <NUM>/<NUM>" ratchet will have a wall thickness of between four to six millimetres, whereas the present invention can have a wall thickness of two millimetres whilst achieving similar torque ratings. This embodiment allows the operation of the ratchet wrench in situations unavailable to other prior art production ratchets, whilst still passing the relevant torque standards.

In an eighth embodiment the toothed drive element may be situated between two washer-like flanges. The washer like flanges retain the drive element within the head portion housing whilst allowing rotation as required within the housing. Preferably the drive element retaining flange can be incorporated within the drive element which is preferably made by high pressure moulding HPM or metal injection moulding MIM in order to further reduce the production cost. This process allows the parts to be mass produced in great numbers with great precision, the drive teeth can easily be over <NUM> in number whilst the profiles of the teeth remain accurate. The closure washer can be stamped and usefully further achieve the enclosure of the drive portion by the use of screws which can also be conveniently removed in order to usefully access or service the internal ratchet mechanism.

In a ninth embodiment the ratchet mechanism can be completely sealed in order to prevent harmful moisture or detritus ingress. The toothed drive element being located between two washer-like flanges, the washer like flanges retain the drive element within the head portion housing whilst usefully allowing the drive element to rotate as required or move latterly according to the tolerances given. The inner surface of the flange or washer lips can further usefully incorporate a groove near their periphery, in which an appropriate seal can be located, the seals usefully acting against the upper and lower smooth flat housing faces outwardly of the pawl recess, in order to provide an efficient method of preventing detritus or moisture damaging the ratchet mechanism. A further groove and seal can be located within the circular shaft of the switch in order to advantageously complete the sealing action when a switch is fitted.

A tenth embodiment may be configured as a un-switched or single direction ratchet the pawl can be resiliently urged into engagement by a low cost torsion type spring positionally retained by a suitable pin through the spring loop, one end of the said spring resiliently acting against the undercut sidewall, the opposing end of the said spring usefully resiliently acting against the pawl rear protrusion.

In an eleventh embodiment, the size and shape of the ramp surfaces and corresponding pawl engagement ramp profiles are chosen to ensure that they cannot completely disengage from one another when the ratchet is used in the reverse direction.

In a twelfth embodiment, under applied torque situations causes the drive element, pawl and head portion housing wall to take the form of a partly pseudo laminate construction when utilized in the said drive direction. This structure provides the method whereby there is achieved an inherently stronger mechanism size for size compared to the prior art, thus permitting superior torque or useful head size reduction. Laminates being inherently stronger than similar thickness materials when using metal grain structures in dissimilar grain directions (cross grain), the resultant compression forces applied to the drive element are substantially dissipated around its circumference. The resultant part pseudo laminate like construction of the drive element, pawl and housing enables a proportionately far stronger or a thinner lighter device. Furthermore, the head portion strength is enhanced by the fact that the main locking forces are directed inwards upon the inherently strong circular drive element surface.

In a thirteenth embodiment, the drive element closure washer and optionally the retaining flange are secured against one another by rivet upstands incorporated within the drive element mating surface, the closure washer having a countersunk hole for the retention of the rivet head profile. By incorporating the rivet fixing within the drive element mating face and thereby virtually obviating the chance of a separate rivet or screw coming loose from the drive element the device is ideal for use in the aerospace industry as the incidence of foreign objects being left in problem areas is further reduced. The rivet protrusions could be further usefully enhanced by the use of central countersunk holes for the ease of precision splaying during the production process.

In a fourteenth embodiment, either the closure washer or retaining flange can usefully incorporate a thumbwheel profile for the convenient and speedy rotation of the drive element by the operator.

At rest the pawl toothed portion may be biased into the corresponding drive element teeth by the switch or torsion spring in order to provide as far as possible instantaneous engagement between the drive element and pawl teeth in such a way to be meshed in circumferential unison when utilized in the ratchet drive direction.

An embodiment of the invention comprises a ratchet mechanism wherein the head portion housing depth for a <NUM>/<NUM> inch square drive is less than <NUM>. , whilst still passing the relevant torque standards.

An embodiment of the invention furher comprises a ratchet mechanism wherein the head portion housing depth for a <NUM>/<NUM> inch square drive is less than <NUM>. , whilst still passing the relevant torque standards.

An embodiment of the invention comprises a ratchet mechanism wherein the head portion housing depth for a <NUM>/<NUM> inch square drive is less than <NUM> whilst still passing the relevant torque standards.

Following is a listing of the various components used in the best mode preferred embodiment and alternative embodiments. For the ready reference of the reader the reference numerals have been arranged in ascending numerical order.

In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the drawing in which:.

There follows a description of embodiments of the invention. It is to be understood that the disclosed embodiments are merely examples of the implementation of the invention, which may be embodied in various other forms within the scope of the claims. The figures are not necessarily to scale, as some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are to aid understanding of the invention and not interpreted as being limiting.

<FIG> illustrate the embodiments of a ratchet wrench <NUM> comprising a head portion <NUM> having a generally circular drive element housing <NUM> in which a drive element <NUM> is at least partially received, an elongate handle <NUM> having a hand grip end <NUM> and a head end <NUM>. A pawl recess <NUM> extends from the inner surface <NUM> of drive element housing <NUM> towards the head end <NUM> of the handle <NUM>. The pawl recess <NUM> is provided with a plurality of ramp surfaces <NUM> configured as low angled teeth. A pawl <NUM> is located within the pawl recess <NUM>.

The pawl <NUM> is provided with a plurality of engagement ramp profiles <NUM> abutting the ramp surfaces <NUM>. The pawl <NUM> has a toothed face <NUM> facing into the drive element housing <NUM>. The teeth <NUM> of the toothed face <NUM> are configured to mesh with drive element teeth <NUM> of a circumferentially extending toothed portion <NUM> of the drive element <NUM> so that the toothed face <NUM> can transmit a torque input via the handle <NUM> to the drive element when a turning force in the drive direction D is applied by a user. The rear face <NUM> of the pawl is provided with a flange <NUM> disposed within a recess <NUM>. The recess <NUM> opens into the pawl recess <NUM> and is disposed between the pawl recess and the head end <NUM>. The flange <NUM> defines a biasing face <NUM> that comprises two end stops <NUM>, <NUM> disposed at opposite ends of the biasing flange and a guide face <NUM> disposed between the end stops.

<FIG> and <FIG> illustrate two versions of a ratchet wrench <NUM> having the same ratchet mechanism. The example shown in <FIG> has a drive element <NUM> with a spigot <NUM> and the example shown in <FIG> has a drive element <NUM> with a fastener operating profile <NUM> configured to receive and engage a fastener.

Optionally a direction setting switch <NUM> is provided. The switch <NUM> comprises an operating lever <NUM> which may be similar to operating levers of prior art switches and a switch axle <NUM> disposed for rotation within a switch bore <NUM> provided in the head portion <NUM>. The switch axle <NUM> is provided with a blind cross bore <NUM> that houses a pressing member <NUM> and a biasing spring <NUM> that biases the pressing member outwardly with respect to the open end of the cross bore <NUM>. The pressing member <NUM> is a sliding fit in the cross bore <NUM>. The pressing member <NUM> comprises a shaft <NUM> disposed within the spring <NUM> and an operating face <NUM> disposed externally of the cross bore <NUM>. The operating lever <NUM> of the switch <NUM> is disposed within a switch lever recess <NUM> defined in the head portion <NUM>. The switch lever <NUM> is rotatable back and forth in the switch lever recess <NUM> to move the pressing member <NUM> between the end stops <NUM>, <NUM> in order to bias the engagement ramp profiles <NUM> of the pawl <NUM> against the ramp surfaces <NUM> in the pawl recess <NUM> in order to set a clock or anti-clockwise drive direction D. The pawl <NUM> is resiliently urged into pawl engagement PE with the drive element <NUM> by the biasing spring <NUM> and pressing member <NUM> resiliently acting against the pawl biasing face <NUM>.

In the reverse, or reposition, direction R, the pawl <NUM> is propelled in the pawl disengagement direction PD so that the drive element teeth <NUM> can slide over the pawl teeth <NUM> against the biasing force of the switch spring <NUM>. As shown in <FIG> and <FIG>, when the ratchet mechanism is configured as an un-switched, or single direction, mechanism, the pawl <NUM> may be resiliently urged into engagement PE with the drive element teeth <NUM> by a low-cost torsion type spring <NUM> positionally retained by a suitable pin <NUM>. One end <NUM> of the spring <NUM> acts against the undercut sidewall of the recess <NUM> and the opposing end <NUM> acts against a biasing face <NUM> of a rearwardly facing flange <NUM> of the pawl. In the reverse, or reposition, direction R, the pawl <NUM> is propelled in the pawl disengagement direction PD allowing the drive element teeth <NUM> to slide over the teeth <NUM> of the pawl <NUM> against the biasing force of the torsion spring <NUM>.

<FIG> is an exploded perspective view of the ratchet wrench <NUM> of <FIG>. The parts shown include the handle <NUM> and its hand grip end <NUM>, the head portion <NUM>, head portion outer surface <NUM>, housing wall <NUM>, inner surface <NUM>, pawl recess <NUM>, pawl recess dual direction engagement ramp profiles <NUM>, recess <NUM>, switch bore <NUM> and switch arm recess <NUM>. The drive element <NUM> has a circumferentially extending toothed portion <NUM> having teeth <NUM>, a spigot <NUM>, retaining flange <NUM>, sealing ring groove <NUM>, seal <NUM>, flange <NUM>, thumbwheel profile <NUM>, retaining screws <NUM> and screw holes <NUM>. The pawl <NUM> toothed face <NUM> having teeth <NUM>, dual direction engagement ramp surfaces <NUM>, rear face <NUM>, flange <NUM>, biasing face <NUM>, first and second end stops <NUM>, <NUM> and the guide face <NUM> between. The switch <NUM> with its operating lever <NUM>, axle <NUM>, pressing member <NUM> and biasing spring <NUM>.

Referring to <FIG>, the ratchet wrench <NUM>, a potential width reduction of the housing wall <NUM> of the head portion <NUM> is shown. The housing wall <NUM> may be made from suitable spring steel in order to provide a resiliently deformable wall portion <NUM>. When the ratchet wrench <NUM> is operated in the drive direction D, the pawl <NUM> is driven in the pawl engagement PE direction so that the pawl engagement ramp profiles <NUM> (<FIG> and <FIG> versions) or <NUM> (<FIG> and <FIG> version) are pressed against the pawl recess ramp surfaces <NUM> (<FIG> and <FIG> versions) or <NUM> (<FIG> and <FIG> version) so that the toothed face <NUM> of the pawl <NUM> is driven inwardly with respect to the drive element housing <NUM> against the circumferentially extending drive element toothed portion <NUM> to lock the drive element <NUM> within the head portion <NUM>. The drive element <NUM> is configured so as to be capable of limited lateral movement against the inner surface <NUM> of the drive element housing <NUM> so that the drive element teeth <NUM> can firmly engage the inner surface <NUM> of the central housing <NUM> opposite the pawl recess <NUM> (see <FIG>). When a force is applied to hand grip end <NUM> of the handle <NUM> in the drive direction D, the inward force IF exerted by the drive element <NUM> may deform the resiliently deformable wall portion <NUM> of the head portion <NUM> inwardly upon the toothed portion <NUM> of the drive element <NUM> resulting in a superior clamping force CF action between the drive element and the abutting portion of the housing wall <NUM>. The teeth <NUM> of the drive element <NUM> may have substantially flat tips <NUM> as an aid to the clamping force CF gripping action provided between the drive element toothed portion <NUM> and the housing inner surface <NUM> of the housing resiliently deformable wall portion <NUM>, so that the drive element <NUM>, pawl <NUM> and head portion housing wall <NUM> form of a pseudo-laminate structure when utilized in the drive direction D. This structure provides an inherently stronger ratchet mechanism and wrench head portion size-for-size compared to prior art wrench head portions, thus permitting superior torque transmission by relatively smaller head portions <NUM>. The pseudo-laminate like structure of the drive element <NUM>, pawl <NUM> and drive element housing <NUM> enables the provision of a proportionately far stronger or a thinner lighter wrench head. Furthermore, the head portion <NUM> strength is enhanced by the fact that the main locking forces IF, CF are directed inwards onto the inherently strong circular drive element toothed portion <NUM>. A further aid to locking engagement between the housing inner surface <NUM> and the drive element toothed portion <NUM> is obtained by the teeth <NUM> having tips that are radiused so as to be near flat and having the same profile as the inner surface <NUM> of the drive element housing <NUM>.

<FIG>, <FIG> and <FIG> show the drive element toothed portion <NUM> will be substantially the same height as the head portion housing wall <NUM>. The depth, or height of the toothed face <NUM> of the pawl <NUM> is also is substantially the same as the height of the head portion housing wall <NUM>, thereby further maximising the pawl <NUM> to drive element tooth <NUM> to pawl tooth <NUM> engagement contact area.

The drive element <NUM> is retained in the drive element housing <NUM> between two relatively thin flanges <NUM>, <NUM> (best seen in <FIG>). Preferably, one of the retaining flanges <NUM> is integral with the drive element <NUM>. The other flange <NUM> is defined by a closure washer releasably secured to the drive element <NUM> by screws <NUM> that engage in screw holes <NUM> provided in the drive element. The configuration of the parts is such as to allow the drive element <NUM> to move laterally within the drive element housing <NUM> according to the specified tolerances. The use of screws <NUM> to secure the flange <NUM> to the drive element <NUM> allows it to be conveniently removed in order to access or service the ratchet mechanism.

<FIG> further illustrate how the flange <NUM> may be secured against one another by rivet upstands <NUM> incorporated within the drive element mating surface <NUM>, the closure washer <NUM> preferably having countersunk holes <NUM> for the retention of the splayed rivet head <NUM>. By incorporating the rivet fixing <NUM> within the drive element mating face <NUM> and thereby virtually obviating the chance of a separate rivet <NUM> or screw <NUM> coming loose from the drive element <NUM> the ratchet wrench is ideal for use in the aerospace industry as the incidence of foreign objects being left in problem areas is further reduced. The rivet protrusions <NUM> could be further usefully enhanced by the use of central holes <NUM> for the ease of precision splaying during the production process.

<FIG>, <FIG> and <FIG> further illustrate the ratchet wrench <NUM>, which can be completely sealed in order to prevent harmful moisture or detritus ingress. The drive element <NUM> is retained in the head portion <NUM> between two flanges <NUM>, <NUM>. The flanges <NUM>, <NUM> retain the drive element <NUM> within the drive element housing <NUM> whilst usefully allowing the drive element <NUM> to move laterally according to the allowed tolerances. The inner surface of the flanges <NUM>, <NUM> may be provided with respective grooves <NUM>, <NUM> near their periphery, in which an appropriate seal <NUM> can be located. The seals <NUM> usefully act against the upper and lower smooth flat housing faces <NUM> outwith the pawl recess <NUM>, in order to provide an efficient method of preventing detritus or moisture damaging the wrench head. A further groove <NUM> and seal <NUM> can be located within the switch axle <NUM> of the switch <NUM> in order to advantageously complete the sealing action when a switch <NUM> is fitted.

Claim 1:
A ratchet wrench comprising:
a handle (<NUM>) having a head end (<NUM>);
a head portion (<NUM>) connected to said head end (<NUM>) and provided with a circular drive element housing (<NUM>), said head portion having a pawl recess (<NUM>) disposed between said drive element housing and said head end;
a drive element (<NUM>) at least partially housed in said drive element housing (<NUM>) and having a toothed portion (<NUM>) comprising teeth (<NUM>) disposed circumferentially about said drive element; and
a pawl (<NUM>) located within the pawl recess (<NUM>), the pawl having a plurality of engagement profiles (<NUM>; <NUM>) configured to engage a facing surface (<NUM>; <NUM>) provided in said pawl recess and a toothed face (<NUM>) facing into said drive element housing (<NUM>) and provided with a plurality of teeth (<NUM>) configured to mesh with oppositely disposed teeth (<NUM>) of said drive element toothed portion (<NUM>),
wherein the arrangement is such that, in use, when a drive force is applied to said handle (<NUM>), a plurality of said engagement profiles (<NUM>; <NUM>) engage with the facing surface (<NUM>; <NUM>) to urge the pawl (<NUM>) into locking engagement with the drive element (<NUM>),
characterised in that said drive element housing (<NUM>) is partially defined by an arcuate wall (<NUM>) of the head portion (<NUM>) that is configured to be resiliently deformable when, in use, said pawl (<NUM>) lockingly engages said drive element (<NUM>),
and it that said engagement profiles comprise engagement ramp profiles (<NUM>; <NUM>) that engage respective facing ramp surfaces (<NUM>; <NUM>).