Power tools are advantageously used in many situations where rapid manipulation of engineering elements are required. Such power tools are usually operated by electric, pneumatic, hydraulic or mechanical means.

A particularly useful type of power tool comprises a power or ratchet wrench. Such a power, tool allows nuts, bolts and like fasteners to be readily tightened or loosened and can also be -used to tighten fasteners to a predetermined torque.

The advantage of providing such power tools with a ratchet mechanism is that fasteners are caused to be rotated in one direction only;

Prior art power tools incorporating ratchet mechanisms are disclosed in the following patent specifications: AU90083/82, US4770071, US4854197, US4744271, US4669338, US4770072, US4589307, OS4566356, US4529071, 0S4425828, US4748875, US4347767, US4409865, US4339968, US4336727, US4308769, US4307632, US4U6093, US3958470, US3930776, EP246262, EP230461, EP202130, GB2148767, DE3514381. However these prior art power tools are not believed to be relevant to the present invention.

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A type of ratchet spanner known as the through ratchet by SHINANO TOOL COMPANY comprises a ratchet ring rotatably mounted within a ratchet yoke - The ratchet ring is

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2 configured to accept a socket adaptor to which can be mounted a variety of different socket sizes thereby allowing the tool to be used in association with a large number of different sized nuts or bolts. The ratchet yoke is caused to reciprocate or oscillate by a crank mechanism and this in turn rotates the ratchet ring through a plurality of ratchet teeth on the ratchet ring which engage with a first pawl mounted on the ratchet yoke. All of the aforementioned components are located in a single ratchet housing which incorporates a pair of aligned apertures which provide access to the ratchet ring located therebetween.

In order to prevent reciprocation of the ratchet ring upon reciprocation of the ratchet yoke, a second pawl is located within the ratchet housing and in operative engagement with the ratchet ring. The first pawl can be envisaged as a "driving" pawl to rotate the ratchet ring upon reciprocation of the ratchet yoke and the second pawl functions to prevent reciprocation of the ratchet ring thereby ensuring that the ratchet ring rotates only in a desired direction.

A disadvantage of this known ratchet spanner is that the assembly requires at least two pawls to ensure rotation of the ratchet ring in one direction. This in turn requires a complex assembly of components making the power tool complex to manufacture and expensive to produce. The increased complexity of this known ratchet spanner results in

3 increased manufacturing costs and an increased possibility of breakdown due to wear and tear.

A further disadvantage of the SHINANO spanner is that difficulties are experienced in obtaining access to the internal components in the case of maintenance or repair.

It is an object of the invention to provide a power tool having a simplified assembly, and which may alleviate the abovementioned disadvantages.

In one form, the invention resides in a power tool for rotating fasteners such as nuts and bolts, said power tool comprising a housing, a rotatable member mounted in said housing for engagement with the fastener, a reciprocatable member associated with said rotatable member for causing rotation of said rotatable member, and operating means for causing reciprocation of the reciprocatable member, characterised in that there is provided bearing means to place the rotatable member under a load to resist in rotation in one direction.

The housing suitably comprises a plurality of separate components (eg. two, three or four, for example) which can be secured together. The components are preferably releasably secured to each other through suitable fasteners such as screws.

Suitably, the housing comprises a pair of housing components which can be mirror images of each other.

4 Each of the pair of housing components may comprise a head portion, a tail portion and an intermediate portion.

The head portion may include an opening to allow the rotatable member to engage with or to a fastener. The tail portion may be configured to facilitate coupling to a drive means. In this regard, the tail portion may define a half chamber which upon assembly with the other housing component defines an open ended chamber to couple with a drive means. The intermediate portion may comprise a shank having an outer configuration adapted to allow an operator to grasp the tool.

Each of the housing components may be provided with recesses to accommodate various internal components of the power tool such as the rotatable member and the reciprocatable member.

The rotatable member suitably comprises a disk like body. The disk like body may be solid or hollow. Preferably, the disc like body is hollow to define a ring. The ring may be formed with an internal configuration to enable engagement with a fastener. Thus, in one embodiment, the internal configuration of the ring is polygonal and preferably hexagonal to allow the rotatable member to engage with a fastener having an hexagonal configured head portion. In an alternative embodiment, the rotational member may be formed with a projection which may engage with a recess or slot located on the fastener. Thus, the projection may include a blade to engage with a slot on a screw, or the

5 projection may be configured to allow it to engage with a

"phillips head" type screw or the projection may have a polygonal configuration to allow it to engage with a fastener having an "ALLEN" head. In yet a further alternative, the rotational member may be provided with means to allow it to be operatively connected to a large number of sockets. Thus, the rotational member or each respective socket may be provided with a projection or recess which can mate with each other thereby allowing a large number of different sockets to be operatively associated with the rotational member.

The rotational member is suitably formed with a plurality of σircumferentially spaced projections which may comprise teeth evenly spaced about the rotatable member. The rotatable member may also include one or a pair of end abutments for bearing engagement with an adjacent internal surface of the housing.

The reciprocatable member may comprise a yoke having a substantially annular body partially locatable within a suitable recess in each housing component. The annular body may be dimensioned to allow the rotatable member to be at least partially accommodated therein.

The operating means may comprise a drive member operatively associated with the reciprocatable member. The drive member may comprise a drive bushing which is locatable within and slidable along a first recess formed on the reciprocatable member.

The drive bushing may be reciprocated by being

6 mounted to an offset projection or pin on an axial face of an associated rotatable drive shaft.

The rotatable member may be caused to rotate within the reciprocatable member upon reciprocation of the latter by an advancement means.

The advancement means may comprise a ratchet pawl. The ratchet pawl may be located in an accommodating recess or slot in the reciprocatable member.

In order to maintain rotation of the rotational member and to prevent reciprocation thereof, the housing upon assembly, causes a load to be placed on the rotatable member.

Suitably, this load is applied to one or both end abutments of the rotatable member by the bearing means. The bearing means may be in the form of sliding friction contact between each end abutment and adjacent internal surfaces of each housing component. Alternatively the bearing means may comprise one or a pair of intermediate members such as a bearing washer.

The invention will be more fully understood by reference to the following description of a preferred embodiment thereof in which

Figure 1 is an exploded view of a power tool according to an embodiment of the invention.

Figure 2 is a plan view of the power tool of figure 1 with the upper portion of the housing removed.

Figure 3 is a side elevation view of the power tool of figure 2.

Figure 4 is a perspective view of the tail section

7 o f the power tool according to one alternative o f the invention .

Figure 5 is a perspective view of the tail portion o f the power according to a second alternative of the invention.

Figure 6-8 are plan views of the operation of the power tool.

Referring to .figure 1, there is disclosed a power tool comprising a pair of housing components 10a,10b which can be fastened together through fasteners 11 (only one shown) . Fasteners 11 pass through openings 12 in housing components 10a,10b. One of the corresponding openings has a smooth bore while the other of the corresponding openings is provided with an internal thread to mate with the thread of fasteners 11.

Each housing component comprises a head portion 13, tail portion 14, and intermediate portion 15.

Head portion 13 is formed with an internal recess

16 provided with a circular opening 17 extending through the wall of each housing component 10a, 10b.

The intermediate portion 15 includes an internal recess 18 linking head portion 13 and tail portion 14 which recess can accommodate a drive shaft 19 which shall be described in greater detail below. Tail portion 14 when the two housing components

10a, 10b are assembled define an open ended chamber (more clearly shown in figures 4 and 5) to which can be coupled a drive source (not shown) .

8 Recess 16 accommodates a reciprocatable member 20 which comprises a yoke having a substantially annular body. Reciprocatable member 20 is maintained within recess 16 upon assembly of housing components 10a, 10b. Reciprocatable member 20 includes a thickened portion 21 extending along a part thereof. Thickened portion 21 is formed with a first recess or slot 22 communicating with an exterior part of the annular body and a second recess or slot 23 which communicates with the interior portion of the annular body.

Rotatable member 24 is dimensioned to allow it to be accommodated at least partially within the annular body of reciprocatable member 20.

Rotatable member 24 comprises a ratchet ring having a hollow circular disc like body.

The internal passageway 25 of rotatable member 24 is hexagonal in cross section to allow it to engage with fastening elements having an hexagonal head.

It should be appreciated however that the passageway 25 may be formed with various other cross- sectional configurations.

R o t a t a b l e m e m b e r 2 4 i s f o r m e d w i t h circumf erentially spaced teeth 26 which extend about the rotatabl e member . Teeth 2 6 are spaced inwardly from respective end faces of rotatable member 24 to define a pair of end abutments 27a , 27b .

The operating means to cause reciprocation of reciprocatable member 20 comprises a drive bushing 28 which

9 locates within recess 22. Drive bushing 28 locates over an offset pin 29 located on an axial face of drive shaft 19.

Drive shaft 19 is mounted "for rotation within recess 18 of housing components 10a,10b and rotation is facilitated by providing needle bearings 30,31 which are located at adjacent ends of drive shaft 19.

To prevent drive shaft 19 from being displaced axially within recess 18, a locating pin 32 is provided on housing component 10b which locates within a groove 33 on drive shaft 19.

Rotatable member 24 is caused to rotate within reciprocatable member 20 upon reciprocation of the latter by an advancement means. The advancement means comprises a pawl 34 which locates within recess 23. Pawl 34 is biassed into engagement with teeth 26 by a spring 35 which is positioned between pawl 34 and the wall of recess 23.

To maintain rotation of rotatable member 24 upon reciprocation of reciprocatable member 20, a load is applied to rotatable member 24 adjacent end abutments 27a,27b. The load is provided by assembling housing components 10a, 10b to sandwich rotatable member 24 between the housing components. A bearing washer 36 is located over one end abutment 27a or 27b which facilitates providing an even load to rotatable member 24 upon assembly of housing components 10a, 10b. The load is in the form of sliding friction contact between rotatable member 24 and bearing washer 36 and may also include sliding friction contact between a portion of recess 16 and an end abutment 27a,27b.

10 It should be appreciated however that bearing washer 36 may be provided on both end abutments 27a,27b.

The operation of the power tool will now be described with particular reference to figures 6-8. In figure 6, reciprocatable member 20 is in a first extreme position in recess 16. In figure 7, reciprocatable member 20 has been reciprocated to the other extreme position within recess 16. In figure 8, reciprocatable member 20 is at a position between the extreme positions as illustrated in figures 6 and 7.

Reciprocatable member 20 is caused to reciprocate by rotation of drive shaft 19 in the direction of the arrow. Upon rotation of drive shaft 19, offset pin 29 (shown in phantom) is caused to rotate in an offset manner. Drive bushing 28 is mounted over pin 29 and also locates within recess 22 on reciprocatable member 20.

Thus, upon rotation of drive shaft 19, offset pin 29 and drive bushing 28 rotate from the position illustrated in figure 6 to the position illustrated in figure 7 and cause reciprocatable member 20 to move from the first extreme position as illustrated in figure 6 to the second extreme position as illustrated in figure 7. Of course, as pin 29 and drive bushing 28 rotate, drive bushing 28 also moves along recess 22. Upon further rotation of drive shaft 19, offset pin

29 and drive bushing 28 will continue rotation in the direction of the arrow (in fig 6) to move reciprocatable member 20 back from the position illustrated in figure 7 to

11 the position illustrated in figure 6 and through the position illustrated in figure 8.

When viewed in plan, this action results in reciprocation of reciprocatable member 20 within recess 16. Rotatable member 24 locates within the confines of the annular body of reciprocatable member 20 and is freely rotatable relative to the reciprocatable member 20.

However, reciprocatable member 20 includes pawl 34 located within slot 23 and which is biassed into engagement with the circumferentially spaced teeth 26 located on rotatable member 24.

Thus, upon movement of reciprocatable member from the position illustrated in figure 6 to the position illustrated in figure 7, rotatable member 24 will also initially be rotated in the direction of the arrow due to its engagement with spring loaded pawl 34.

Due to this positive connection between rotatable member 24 and reciprocatable member 20 through spring loaded pawl 34 and reciprocatable member 20 and rotatable shaft 19 through drive bushing 28, the rotatable member 24 is rotated notwithstanding the load applied to it by bearing washer 36 (not shown) which is in sliding engagement with one or both of the end abutments 27a,27b of the rotatable member.

Upon further rotation of drive shaft 19, reciprocatable member 20 will return from its position illustrated in figure 7 to its position illustrated in figure

6. At this stage, the load applied to rotatable member 24 is sufficient to prevent counter-rotation of the rotatable

12 member upon return of reciprocatable member 20. Spring loaded pawl 34 is instead caused to ride over the circumferentially spaced teeth 27 on rotatable member 24 to locate behind an adjacent tooth. " Upon further rotation of drive shaft 19, the process is repeated and spring loaded pawl 34 once again rotates rotatable member 24 against the effects of the load applied to it and upon return of the reciprocatable member 20, the load applied to rotatable member 24 is sufficient to result in spring loaded ■ pawl 34 riding over teeth 27 to locate behind an adjacent tooth.

It can be seen that upon continued rotation of drive shaft 19, the above described process will repeat itself to result in rotatable member 24 being rotated in one direction only.

Drive member 19 extends into the open ended chamber formed in the tail portion 14 of housing components 10a,10b and can thereby be coupled to a drive source. The drive source may be electric, hydraulic, pneumatic or mechanical. Figures 4 and 5 show alternative arrangements of the open ended chamber. In figure 4, the drive source (not shown) locates within the open ended chamber 37 and couples to the end of drive shaft 19.

In figure 5, there is disclosed an alternative arrangement whereby the drive source (not shown) mounts into chamber 37 are also about the outer periphery of chamber 37. This latter arrangement prevents any separation of housing components 10a, 10b upon coupling of the power tool to a drive

13 source .

The power tool according to the invention eliminates the requirements of intricate springs and pins and a plurality of pawls to ensure rotation of the rotatable member which in turn reduces assembly time and therefore cost of the tool.

In the embodiment, the components of the power tool are fully enclosed within housing components 10a, 10b which protects the interior components from ingress of dirt and foreign matter.

The power tool is compact in configuration thereby allowing the tool to be used in confined spaces and the tool is further high in torque performance.

The housing can comprise an angled head to facilitate attachment to fasteners in certain situations.

It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit and scope of the invention as defined in the appended claims.