GB2614543A

GB2614543A - A shaft lock

Info

Publication number: GB2614543A
Application number: GB2200091.3A
Authority: GB
Inventors: Skenfield Geoffrey
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-01-06
Filing date: 2022-01-06
Publication date: 2023-07-12

Abstract

Apparatus 100 for locking on a shaft, comprises an annular member 102 (see Fig. 1b) having a central aperture 106 (see Fig. 1b) and a central axis with at least one through bore 108 extending from an outer surface of the annular member and into the central aperture. An axis of the bore 108 is oriented substantially perpendicular to and offset from the central axis of the annular member. The axis of the bore 108 is substantially parallel to a tangent of the central aperture and is located on or inside the tangent line with respect to the central axis. At least one locking element 114 is moveable along the bore 108 and comprises at least one bearing surface 115 for engagement with the shaft. At least one actuator 116is provided for selectively moving the locking element 114 towards the shaft to engage the at least one bearing surface 115 therewith and lock the apparatus 100 on the shaft.

Description

A SHAFT LOCK

The present invention relates to apparatus for locking an annular member, such as a nut or collar, to a plain or threaded shaft.

Shaft collars can be found in virtually any type of machinery, most notably motors and gearboxes, and are frequently accessories to other components. Capable of fulfilling many roles, shaft collars often hold bearings and sprockets on shafts, situate components in motor and gearbox assemblies, and serve as mechanical stops.

Shaft collars are used in industrial equipment and machines as well as in light duty applications, such as coat racks, home gym equipment, and even football tables.

A shaft collar typically includes a solid annular body defining a central aperture for sliding the collar over and along a shaft, and a set screw located in a threaded bore extending through the annular wall of the collar and oriented perpendicularly with respect to an axis of the central aperture, wherein the axis of the threaded bore intersects the central axis of the collar such that the threaded bore opens into the central aperture. In use, the set screw is tightened and forced against the shaft to lock the collar thereto. However, the set screw can damage the outer surface of the shaft, particularly the threads of a threaded shaft, which can cause the outer surface of the shaft to locally flare up and in turn make the collar particularly difficult, if not impossible, to adjust or remove from the shaft. A flat, non-threaded region is often provided on a threaded shaft in an attempt to address this problem but the location of the screw on the shaft is limited to that single location and locating the screw on the flat region is carried out blindly in view of the flat region being hidden when the collar is in situ on the shaft.

Another form of shaft collar includes a threaded bore extending through the annular wall of the collar and oriented perpendicularly with respect to an axis of the central aperture, wherein the axis of the threaded bore is offset from the central axis of the collar such that the diameter of the threaded bore does not intersect the diameter of the central aperture of the collar. A slot extending parallel with the axis of the threaded bore is provided between the central aperture and the threaded bore to allow a wedge portion of a locking element located in the threaded bore to extend into the central aperture. The locking element is configured to slidably move along the threaded bore of the collar responsive to rotation of a screw engaged in a threaded bore of the locking element to thereby urge the wedge portion of the locking element towards or away from a shaft to respectively lock or unlock the collar with respect to the shaft. However, this wedge type of shaft collar is particularly limited in its design and function. Firstly, a single locking element is pulled towards the shaft by rotation of the screw which limits the locking force applied to the shaft. Furthermore, the single locking element which is offset from the central axis of the collar engages one side of the shaft which creates an unbalanced rotational locking arrangement. Additionally, this form of shaft collar relies on the threaded bore extending through the wall of the collar so the wall of the collar must be sufficiently thick (in a perpendicular direction to the central axis) to fully accommodate the threaded bore extending therethrough whilst ensuring sufficient material remains around the threaded bore to prevent the collar failing in use. In turn, the size of screw, and the locking force applied to the shaft, is limited to the thickness of the collar, and the collar must be overly large, particularly for heavy duty applications requiring a relatively large locking element and screw, which undesirably adds weight and increases space requirements for the collar/s and the associated assembly including the collar/s.

It is an aim of certain embodiments of the present invention to therefore provide apparatus for locking an annular member, such as a nut or collar, on a shaft, which addresses one or more of the abovementioned limitations.

It is an aim of certain embodiments of the present invention to therefore provide apparatus for locking an annular member, such as a nut or collar, on a shaft, wherein a locking force applied to the shaft by a locking element of the apparatus is maximised for that particular application and is not limited by a thickness of the annular member.

It is an aim of certain embodiments of the present invention to therefore provide apparatus for locking an annular member, such as a nut or collar, on a shaft, wherein a locking force applied to the shaft by a locking element of the apparatus is substantially balanced with respect to an axis of the shaft.

It is an aim of certain embodiments of the present invention to therefore provide apparatus for locking an annular member, such as a nut or collar, on a shaft, whilst preventing, or at least minimising, a risk of the shaft becoming damaged by the apparatus.

It is an aim of certain embodiments of the present invention to therefore provide apparatus for locking an annular member, such as a nut or collar, on a shaft, wherein a locking element of the apparatus may be repeatedly locked on and released from the shaft, whilst being located at any position around the shaft.

According to a first aspect of the present invention there is provided apparatus for locking on a shaft, comprising: an annular member having a central aperture and a central axis; at least one through bore extending from an outer surface of the annular member and into the central aperture, wherein an axis of the bore is oriented substantially perpendicular to and offset from the central axis of the annular member, and wherein the axis of the bore is substantially parallel to a tangent of the central aperture and is located on or inside the tangent line with respect to the central axis; at least one locking element moveable along the bore and comprising at least one bearing surface for engagement with the shaft; and at least one actuator for selectively moving the locking element towards the shaft to engage the at least one bearing surface therewith and lock the apparatus on the shaft.

Optionally, the at least one bearing surface is angled for engagement with an outer surface region of the shaft.

Optionally, the at least one bearing surface is curved and has a radius of curvature substantially corresponding to the outer surface region of the shaft.

Optionally, the at least one bearing surface comprises a plurality of elongate and spaced apart projections for engagement with a thread of the shaft.

Optionally, the elongate projections define roots and troughs therebetween and each have angled bearing surfaces and a crest.

Optionally, each crest is truncated and each trough extends into the locking element beyond the angled bearing surfaces.

Optionally, the elongate projections define a thread form substantially corresponding to a thread of the shaft.

Optionally, the at least one actuator and locking element are configured and arranged such that the actuator pushes the locking element towards the shaft to force the at least one bearing surface against the shaft.

Optionally, the at least one actuator comprises a locking screw and the at least one bore comprises a threaded region proximal to the outer surface for rotatably engaging the locking screw and a non-threaded region proximal to the central aperture for slidably supporting the locking element.

Optionally, the locking screw comprises a substantially flat abutment surface for engagement with a correspondingly flat abutment surface of the locking element to urge the same towards the shaft.

Optionally, the at least one through bore comprises a first bore disposed opposite and axially aligned with a second bore, wherein a first locking element and a first actuator are located in the first bore, and wherein a second locking element and a second actuator are located in the second bore such that the bearing surfaces of the first and second locking elements are selectively engageable against opposed sides of the shaft by the respective actuators.

Optionally, a common axis of the first and second bores is located between the tangent line of the central aperture and the central axis of the annular member.

Optionally, the at least one through bore comprises a first bore disposed adjacent to and parallel with a second bore, wherein a first locking element and a first actuator are located in the first bore, and wherein a second locking element and a second actuator are located in the second bore, such that the bearing surfaces of the first and second locking elements are selectively moveable in the same direction towards the shaft by the respective actuators.

Optionally, the axes of the first and second bores are each located between a respective tangent line of the central aperture and the central axis of the annular member.

Optionally, the at least one through bore comprises a single through bore extending across the annular member and a pair of opposed actuators are located in the through bore for selectively moving a locking element disposed therebetween in a respective axial direction along the bore to engage the shaft.

Optionally, the locking element is substantially elongate and comprises a concave arcuate bearing surface for engagement with the shaft.

Optionally, the at least one through bore comprises a single through bore extending across the annular member, wherein a first locking element and a first actuator are located in a first end region of the through bore, and wherein a second locking element and a second actuator are located in a second end region of the through bore, such that the bearing surfaces of the first and second locking elements are selectively engageable against opposed sides of the shaft by the respective actuators.

Optionally, the axis of the through bore is located on the tangent line of the central aperture.

Optionally, the annular member comprises a further bore extending from the outer surface into the through bore, wherein the further bore is oriented perpendicularly to the through bore.

Optionally, the further bore comprises a screw thread for receiving a correspondingly threaded screw configured to engage adjacent end regions of the first and second locking elements and release the same from the shaft.

Optionally, the release screw comprises a tapered end region for engagement with opposed tapered surfaces of the end regions of the locking elements.

According to a second aspect of the present invention there is provided an assembly comprising apparatus according to the first aspect of the present invention, and a 10 shaft.

Optionally, the shaft comprises a threaded portion or a non-threaded portion on which the apparatus is lockable.

Optionally, the annular member comprises a nut or a collar.

According to a third aspect of the present invention there is provided a method of locking an annular member to a shaft, comprising: slidably locating an annular member on a shaft, wherein the annular member comprises a central aperture, a central axis, and at least one through bore extending from an outer surface of the annular member and into the central aperture, wherein an axis of the bore is oriented substantially perpendicular to and offset from the central axis of the annular member, and wherein the axis of the bore is substantially parallel to a tangent of the central aperture and is located on or inside the tangent line with respect to the central axis; and via at least one actuator, moving a locking element along the through bore and towards the shaft to engage the at least one bearing surface on the shaft and lock the apparatus to the shaft.

Description of the Drawings

Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure la illustrates an exploded cross section through a locking nut according to a first embodiment of the present invention; Figure lb illustrates a cross section through the locking nut of Figure 1a when in an 10 assembled state; Figure lc illustrates the locking nut of Figures la and lb mounted on a threaded shaft; Figure ld illustrates a locking element of the locking nut of Figures la to 1c; Figures le and if illustrate how a thread form of the locking element of Figure 1d interacts with the threaded shaft; Figure lg illustrates a schematic force diagram to calculate the holding torque on a plain shaft; Figure lh illustrates the increase in locking torque of an offset locking screw on a locking nut compared to a locking screw on the centreline of the locking nut; Figure 2a illustrates an exploded cross section through a locking nut according to a second embodiment of the present invention; Figure 2b illustrates a cross section through the locking nut of Figure 2a when in an 30 assembled state; Figure 2c illustrates the locking nut of Figures 2a and 2b mounted on a threaded shaft; Figure 3a illustrates an exploded cross section through a locking nut according to a third embodiment of the present invention; Figure 3b illustrates a cross section through the locking nut of Figure 3a when in an assembled state; Figure 3c illustrates the locking nut of Figures 3a and 3b mounted on a threaded shaft; Figure 3d illustrates the increase in locking torque provided by the locking nut of Figures 3a to Sc compared to the locking nut of Figures la to 1d; Figure 4a illustrates an exploded cross section through a locking collar according to a fourth embodiment of the present invention; Figure 4b illustrates a cross section through the locking collar of Figure 4a when in an assembled state; Figure 4c illustrates the locking collar of Figures 4a and 4b mounted on a threaded 20 shaft; Figure 4d illustrates a locking element of the locking collar of Figures 4a to 4c; Figure 5a illustrates an exploded cross section through a locking collar according to a fifth embodiment of the present invention; Figure 5b illustrates a cross section through the locking collar of Figure 5a when in an assembled state; Figure 5c illustrates the locking collar of Figures 5a and 5b mounted on a threaded shaft; Figure 5d illustrates a locking element of the locking collar of Figures 5a to 5c; Figure 6a illustrates an exploded cross section through a locking collar according to a sixth embodiment of the present invention; Figure 6b illustrates a cross section through the locking collar of Figure 6a when in 5 an assembled state; Figure 6c illustrates the locking collar of Figures 6a and 6b mounted on a threaded shaft; and Figure 6d illustrates a pair of opposed locking elements of the locking collar of Figures 6a to 6c.

Detailed Description

As illustrated in Figures la to ld, apparatus 100 according to a first embodiment of the present invention includes an annular member 102 in the form of a locking nut having six flat outer surfaces 104 and a central threaded aperture 106 defining a central axis 107. The nut 102 includes a bore 108 which extends from at least one of the outer surfaces of the nut and opens into the central aperture of the nut. The bore is circular in cross section and is partially threaded along its length starting from the opening in the outer surface/s to define a threaded region 110 and a non-threaded region 112. The bore 108 defines a bore axis 109 which is oriented substantially perpendicular to the central axis 107 of the nut and vertically offset therefrom. The axis 109 of the bore is substantially on a mid-axis 103 of the nut.

The apparatus further includes a locking element 114 which is circular in cross section and sized to slidably move along the non-threaded region 112 of the bore 108. The locking element is located in the bore via the opening in the side of the nut. The locking element 114 has a substantially flat first end surface 113 and a substantially curved second end surface 115 which has a radius of curvature substantially corresponding to the threaded shaft for corresponding engagement therewith as described further below. Alternatively, the radius of curvature of the second end surface 115 may be greater than that of the shaft or the second end surface 115 may be substantially flat and tapered to increase the locking force on the shaft.

The locking element 114 is supported in the non-threaded region 112 of the bore and is slidably moveable therealong. The locking element 114 may comprise at least one projection or axial slot/recess for respective engagement with a corresponding axial slot/recess or elongate projection in the bore to guide the locking element axially along the bore whilst preventing the same rotating in the bore. For example, the locking element 114 may be splined for corresponding engagement with a plurality of circumferentially arranged and axially oriented slots in the bore to help guide the locking element along the bore whilst preventing the same rotating therein. The locking element 114 may be non-circular in cross section, such as oval or trilobular, to allow the same to slide along the correspondingly shaped bore whilst being prevented from rotating therein. A non-circular and/or splined configuration may also be desirable to increase the engagement surface area and in turn friction to hold the locking element in the bore whilst the apparatus is being assembled or installed. Further alternatively, the locking element may be trilobed or include a plurality of axially oriented serrations arranged around its outer surface which engage with the substantially smooth and non-threaded inner surface of the bore such that the surface interference area, and in turn friction, is reduced to thereby reduce the force required to urge the locking element along the bore, whilst being sufficient to retain the locking element in the bore during assembly, installation or adjustment.

The apparatus further includes an actuator 116 in the form of a threaded set screw having a head end configured to receive a suitable tool, such as an Allen key, to selectively rotate the screw in the threaded bore 108. The threaded shank of the screw 116 terminates at a substantially flat end surface 117 for engagement with the flat first end surface 113 of the locking element 114 when the screw is rotated in a first direction (aptly clockwise) to thereby urge the curved bearing surface 115 of the locking element 114 towards the shaft 150 on which the apparatus 100 is mounted in use, as illustrated in Figures lb and lc. Further rotation of the screw 116 in the first direction urges the bearing surface 115 of the locking element 114 against the shaft 150 and applies a locking force thereto to lock the apparatus with respect to the shaft in both axial and rotational directions. Alternatively, the end surface 117 of the screw may be domed or pointed for engagement with a recess or cup in the end surface of the locking element 114 to reduce rotational friction therebetween.

With reference to Figure 1g, the holding torque Tv subject to a standard plain (non-threaded) shaft by a conventional shaft collar can be calculated based on the following equations: F= TN = 2RF TN = 2R[I.117 (1) The gripping force (P) produced by a locking screw of a conventional shaft collar can be calculated using the following equation: TG (2) P= ro tan(a+A)+7).112 By substituting for P from equation 2 into equation 1, the holding torque TN on a plain shaft with a locking screw disposed on the centreline of the shaft collar can be approximately calculated using the following equation: TN= rc, tan(a + A) + r1 R2 The holding torque on a screwed shaft with the locking screw on the centreline is calculated using the following equation: TN= (r0 tan(a + + r1 p2) cos 0 2RitiTG 2Rbt1TG The holding torque on a threaded shaft with an offset locking screw in accordance with certain embodiments of the present invention is approximately calculated using the following equation: TN = (ro tan(a + A) + ri p.2) cos 9 cos 0 wherein for the abovementioned equations: lo P -Force applied by locking element on shaft R -Shaft/Screw radius ro -Mean radius of locking screw ri -Effective friction radius of locking screw -Coefficient of friction between locking element and nut A -Thread friction angle of locking screw a -Thread pitch angle of locking screw TG -Torque applied to locking screw TN -Torque applied to turn the nut 0 -Half included angle of nut thread 0 -Locking element average contact angle F -Frictional force between shaft/screw shaft and nut 1_12-Coefficient of friction between locking screw and locking element As illustrated in Figure lh, experimental testing by the applicant has shown that the locking torque achieved by offsetting the locking screw from the centre line of a locking nut is significantly greater than the locking torque achieved when the locking screw is located on the centre line of the nut.

As illustrated in Figure ld, a thread form 120 is provided on the curved bearing surface 115 of the locking element 114 which substantially corresponds in terms of at least pitch and thread angle to the thread of the shaft 150. The thread form may 2RptiTG also correspond in terms of helix angle to the shaft thread. Alternatively, if the locking element is relatively small compared to the shaft itself, the thread form may be provided by a plurality of elongate and spaced apart projections, such as ribs, each having a crest and defining roots and troughs therebetween, wherein the thread form engages with a relatively small region of the shaft thread. The spaced apart ribs are aptly parallel to each other. The thread form 120 allows the locking element to securely engage with the threaded shaft when the locking element is in the locked position and provides a greater bearing surface area than that of a single bearing surface which increases the bearing load applied to the surface of the shaft thread by the locking element and in turn increases the frictional locking force and the locking torque. This also avoids damage to the threaded shaft when the locking screw is tightened whilst allowing the locking nut to be repeatedly locked and released in any rotational and axial position on the threaded shaft.

As illustrated in Figures le and 1f, the thread form 120 of the locking element 114 is configured such that the crests 122 of the thread form are each truncated to ensure the same do not engage in the base regions/roots of the corresponding troughs 152 defined by the thread on the shaft 150. Furthermore, a recess 124 is provided at the root of each of the troughs defined by thread form 120 to thereby extend each trough further into the locking element 114 to prevent the crests 154 of the shaft thread engaging with the troughs of the thread form of the locking element 114. This arrangement in turn ensures the bearing load is transferred between the flanks (angled surfaces) of the thread form and the shaft thread as opposed to the crests and roots. This further increases the bearing load applied to the surface of the shaft thread by the locking element and in turn the frictional locking force and locking torque.

As illustrated in Figures la to lc, the axis 109 of the threaded bore 108 is offset from the central axis 107 of the central aperture of the nut, and in turn the shaft when coaxially arranged with the nut, towards a tangent line 111 of the central aperture which is parallel to the axis 109 of the threaded bore. Furthermore, the axis 109 of the threaded bore is located between the central axis 107 and the tangent line 111, i.e. it is located inboard of the tangent line 111 with respect to the central axis 107. Aptly, an outer limit of the inner surface of the threaded bore is substantially aligned with the inner surface of the central aperture. This arrangement further increases the locking force of the locking element on the shaft, and in turn the locking torque, in combination with the angled/curved bearing surface 115 of the locking element against the shaft.

As illustrated in Figures 2a to 2c, apparatus 200 according to a second embodiment of the present invention includes an annular member 202 in the form of a locking nut having a central aperture 206 defining a central axis 207. The nut has a pair of axially aligned yet opposed threaded bores 240,242 extending substantially centrally from a respective side of the nut and through the wall of the nut and into the central aperture. The bores are axially aligned and extend in opposed directions towards each other. The common axis 209 of the threaded bores is offset from the central axis 207 of the central aperture of the nut towards a tangent line 211 of the central aperture which is parallel to the common axis of the threaded bores. Furthermore, the common axis 209 of the threaded bores is aptly located between the central axis 207 and the tangent line 211.

Each bore is configured to accommodate a respective locking element 260,262 and a locking screw 270,272. The configuration of each locking element and locking screw is substantially the same as the embodiment illustrated in Figures la to ld.

The locking torque capacity is significantly increased with a pair of opposed locking elements applying a locking force to the shaft 250 on opposed sides of the central plane of the nut which extends through the central axis. The locking arrangement is also substantially balanced which provides secure locking of the nut with respect to the shaft in both rotational directions.

As illustrated in Figures 3a to Sc, apparatus 300 according to a third embodiment of the present invention includes an annular member 302 in the form of a locking nut having a central aperture 306 defining a central axis 307. The nut has a pair of threaded bores 340,342 each located on a central plane of the nut and extending from the same side of the nut with respect to the central axis and through the wall of the nut and into the central aperture. The respective axes 309a,309b of the bores are parallel but are located on different sides of the central axis, as illustrated in Figures 3a and 3b. The bore axes 309a,309b are equally spaced from the central axis and each bore axis is offset from the central axis 307 towards a respective tangent line 311a,311b of the central aperture which is parallel to the corresponding bore axis 309a,309b, whilst each bore axis is located between the central axis 307 and the respective tangent line 311a,311b.

Each bore is configured to accommodate a respective locking element 360,362 and a locking screw 370,372. The configuration of each locking element and locking screw is substantially the same as the embodiment illustrated in Figures la to ld and Figures 2a to 2c. Each locking element is urged by their respective locking screws in the same direction towards the shaft. The locking torque capacity is significantly increased with a pair of locking elements applying a locking force to the shaft in the same direction but on different sides of the central plane of the nut which extends through the central axis. The locking arrangement is also substantially balanced which provides secure locking of the nut with respect to the shaft in both rotational directions.

As illustrated in Figure 3d, experimental testing by the applicant has shown that the locking torque achieved by providing a pair of locking screws and locking elements in accordance with the embodiment shown in Figures 3a to 3c, is significantly greater (around 70%) than the locking torque achieved with a single offset locking screw and locking element.

As illustrated in Figures 4a to 4d, apparatus 400 according to a second embodiment of the present invention includes an annular member 402 in the form of a locking collar having a threaded central aperture 406 defining a central axis 407. The collar has a through bore 440 extending substantially centrally through the wall of the nut and communicates with the central aperture. An axis 409 of the through bore 440 is substantially parallel with a horizontal plane 480 (for illustration purposes) of the collar extending through the central axis and is vertically offset therefrom. The bore axis 409 is located on a tangent line 411 of the central aperture, wherein the tangent line is substantially parallel with the horizontal plane.

The through bore 440 is configured to define a non-threaded central region 441 located between threaded end regions 443,445. The central region 441 is configured to slidably accommodate an elongate locking element 460 which is circular in cross section and has opposed flat end surfaces for engagement with a corresponding locking screw 471,472 located in a respective one of the threaded end regions 443,445 of the bore 440. The configuration of each locking screw is substantially the same as the above-described embodiments. A central region of the locking element 460 defines a substantially concave bearing surface 463 having a radius of curvature which is substantially the same as that of the shaft 450. A single elongate locking element 460 allows the same to be easily released from the shaft should it become wedged in use and also ensures the locking element remains captive during assembly, installation or adjustment.

As illustrated in Figure 4d, a plurality of elongate projections/ribs 420, to define for example a thread form, is provided on the curved bearing surface 463 of the locking element 460 which corresponds in terms of at least pitch and thread angle to the thread of the shaft 450. This thread form 420 allows the locking element to securely engage with the threaded shaft when the locking element is in the locked position and provides a greater bearing surface area than that of a single bearing surface which increases the bearing load applied to the surface of the shaft thread by the locking element and in turn increases the frictional locking force and the locking torque. This also avoids damage to the threaded shaft when the locking screws are tightened whilst allowing the collar to be repeatedly locked and released in any rotational and axial position on the threaded shaft.

In use, first one of the locking screws is screwed into an end region of the through bore and the locking element is slidably inserted into the central region of the through bore to abut against the first locking screw. The first locking screw may be adjusted such that curved bearing surface of the locking element is substantially aligned with the curvature of the shaft. The second locking screw is then located in the other end region of the through bore to abut the corresponding end surface of the locking element. The collar is then mounted on to the shaft and located in a desired position and orientation thereon. The first locking screw may then be loosened off slightly to allow the second locking screw to be tightened by a corresponding amount to axially move the locking element along the through bore such that the curved bearing surface is offset from the vertical central plane 490 (for illustration purposes) and a locking force and torque is applied to one half of the shaft to securely lock the collar on the shaft. An alternative embodiment of this arrangement is wherein the curved bearing surface 463 of the locking element 460 is substantially smooth and not threaded for engagement with a threaded or non-threaded, plain shaft. Further alternatively, a non-threaded bearing surface may include a plurality of gripping features, such as grooves or ribs, to increase the frictional element of the locking force applied to the shaft.

As illustrated in Figures 5a to 5d, a locking collar 500 which is substantially the same as the locking collar of Figures 4a to 4d, albeit having a non-threaded central aperture 506, may be used with a pair of axially aligned and opposed locking elements 560,562 and corresponding locking screws 570,572 to lock the collar on a non-threaded, plain shaft 550. As illustrated in Figure 5d, each locking element is substantially similar to the locking elements shown in Figure 2b, albeit being slightly longer and the curved bearing surface 563 thereof having a greater radius of curvature to accommodate for the bore axis 509 being further offset from the central aperture of the collar, i.e. on the tangent line 511, compared to the bore axis of the collar illustrated in Figure 2b for example which is located between the central aperture and the tangent line. As illustrated, an optional release bore 595 may be provided extending perpendicularly to the bore axis into the bore 540 and aligned with the central axis 507 to allow a suitable tool, such as a screw driver, rod or wire, for example, to be inserted therein and release one or both of the locking elements 560,562 from the shaft 550 if required to thereby unlock the collar from the shaft.

As illustrated in Figures 6a to 6d, apparatus 600 similar in configuration to the apparatus of Figures 5a to 5d may include a collar 602 including an optional release bore 695 which is threaded to receive a locking screw 696 having a tapered end region 697 for engagement with corresponding angled end regions 698 of the locking elements 660,662 to thereby urge one or both locking elements outwardly (when one or both locking screws 670,672 have been removed) and away from the shaft when the locking screw is rotated in the release bore to engage with the angled surfaces 698 of the locking elements. This release arrangement may be included on a locking collar or nut according to certain embodiments of the present invention for mounting on a threaded or non-threaded shaft.

Certain embodiments of the present invention therefore provide a locking nut or collar configured to securely lock to a threaded or non-threaded shaft in any position along the shaft and in any rotational orientation with respect to the shaft. Desirably, a locking force applied to the shaft by a locking element of the apparatus is maximised and is not limited by a thickness of the nut or collar. Furthermore, a locking force applied to the shaft by a locking element of the apparatus is substantially balanced with respect to an axis of the shaft on which the apparatus is mounted. The apparatus according to certain embodiments of the present invention is configured to prevent, or at least minimise, a risk of the shaft becoming damaged by a locking element of the apparatus, and the apparatus is configured to be repeatedly locked on and released from the shaft, whilst being located at any position or orientation on the shaft. The apparatus may be particularly suitable for harsh environments subject to vibration, high temperature and corrosion. For example, the relatively high clamping and friction forces provided by the apparatus make it particularly suitable for applications subject to vibration and by suitable material selection the apparatus can be resistant to heat and corrosion.

Claims

Claims 1. Apparatus for locking on a shaft, comprising: an annular member having a central aperture and a central axis; at least one through bore extending from an outer surface of the annular member and into the central aperture, wherein an axis of the bore is oriented substantially perpendicular to and offset from the central axis of the annular member, and wherein the axis of the bore is substantially parallel to a tangent of the central aperture and is located on or inside the tangent line with respect to the central axis; at least one locking element moveable along the bore and comprising at least one bearing surface for engagement with the shaft; and at least one actuator for selectively moving the locking element towards the shaft to engage the at least one bearing surface therewith and lock the apparatus on the shaft.
2. The apparatus according to claim 1, wherein the at least one bearing surface is angled for engagement with an outer surface region of the shaft.
3. The apparatus according to claim 2, wherein the at least one bearing surface is curved and has a radius of curvature substantially corresponding to the outer surface region of the shaft.
4. The apparatus according to claim 2 or 3, wherein the at least one bearing surface comprises a plurality of elongate and spaced apart projections for engagement with a thread of the shaft.
5. The apparatus according to claim 4, wherein the elongate projections define roots and troughs therebetween and each have angled bearing surfaces and a crest.
6. The apparatus according to claim 5, wherein each crest is truncated and each trough extends into the locking element beyond the angled bearing surfaces.
7. The apparatus according to any of claims 4 to 6, wherein the elongate projections define a thread form substantially corresponding to a thread of the shaft.
8. The apparatus according to any preceding claim, wherein the at least one actuator and locking element are configured and arranged such that the actuator pushes the locking element towards the shaft to force the at least one bearing surface against the shaft.
9. The apparatus according to any preceding claim, wherein the at least one actuator comprises a locking screw and the at least one bore comprises a threaded region proximal to the outer surface for rotatably engaging the locking screw and a non-threaded region proximal to the central aperture for slidably supporting the locking element.
10. The apparatus according claims 8 and 9, wherein the locking screw comprises a substantially flat abutment surface for engagement with a correspondingly flat abutment surface of the locking element to urge the same towards the shaft.
11. The apparatus according to any preceding claim, wherein the at least one through bore comprises a first bore disposed opposite and axially aligned with a second bore, wherein a first locking element and a first actuator are located in the first bore, and wherein a second locking element and a second actuator are located in the second bore such that the bearing surfaces of the first and second locking elements are selectively engageable against opposed sides of the shaft by the respective actuators.
12. The apparatus according to claim 11, wherein a common axis of the first and second bores is located between the tangent line of the central aperture and the central axis of the annular member.
13. The apparatus according to any of claims 1 to 10, wherein the at least one through bore comprises a first bore disposed adjacent to and parallel with a second bore, wherein a first locking element and a first actuator are located in the first bore, and wherein a second locking element and a second actuator are located in the second bore, such that the bearing surfaces of the first and second locking elements are selectively moveable in the same direction towards the shaft by the respective actuators.
14. The apparatus according to claim 13, wherein the axes of the first and second bores are each located between a respective tangent line of the central aperture and the central axis of the annular member.
15. The apparatus according to any of claims 1 to 10, wherein the at least one through bore comprises a single through bore extending across the annular member and a pair of opposed actuators are located in the through bore for selectively moving a locking element disposed therebetween in a respective axial direction along the bore to engage the shaft.
16. The apparatus according to claim 15, wherein the locking element is substantially elongate and comprises a concave arcuate bearing surface for engagement with the shaft.
17. The apparatus according to any of claims 1 to 10, wherein the at least one through bore comprises a single through bore extending across the annular member, wherein a first locking element and a first actuator are located in a first end region of the through bore, and wherein a second locking element and a second actuator are located in a second end region of the through bore, such that the bearing surfaces of the first and second locking elements are selectively engageable against opposed sides of the shaft by the respective actuators.
18. The apparatus according to any of claim 15 to 17, wherein the axis of the through bore is located on the tangent line of the central aperture.
19. The apparatus according to claim 17, wherein the annular member comprises a further bore extending from the outer surface into the through bore, wherein the further bore is oriented perpendicularly to the through bore.The apparatus according to claim 19, wherein the further bore comprises a screw thread for receiving a correspondingly threaded screw configured to engage adjacent end regions of the first and second locking elements and release the same from the shaft.The apparatus according to claim 20, wherein the release screw comprises a tapered end region for engagement with opposed tapered surfaces of the end regions of the locking elements.An assembly comprising apparatus according to any preceding claim and a shaft.The assembly according to claim 22, wherein the shaft comprises a threaded portion or a non-threaded portion on which the apparatus is lockable.The assembly according to claim 22 or 23, wherein the annular member comprises a nut or a collar.A method of locking an annular member to a shaft, comprising: slidably locating an annular member on a shaft, wherein the annular member comprises a central aperture, a central axis, and at least one through bore extending from an outer surface of the annular member and into the central aperture, wherein an axis of the bore is oriented substantially perpendicular to and offset from the central axis of the annular member, and wherein the axis of the bore is substantially parallel to a tangent of the central aperture and is located on or inside the tangent line with respect to the central axis; and via at least one actuator, moving a locking element along the through bore and towards the shaft to engage the at least one bearing surface on the shaft and lock the apparatus to the shaft. 20. 21. 22. 23. 24. 25.