GB2466129A - Shock absorbing handle for manual tool - Google Patents

Abstract

A handle for a manual instrument such as a broom 10 or hoe, which is formed of an elongate shaft 30 with a sleeve 40, which is fixed at one end of the shaft and able to slide along it otherwise. The user grips the sleeve 40 and pushes along the axis of the handle, such that the sleeve resiliently deforms and applies force to the shaft and hence the implement of the tool 20. As the sleeve is resilient/elastic it can distort and acts a shock absorber so as to negate any jarring motion to the user of the handle. The sleeve may have a concertina or castellated form and may be formed of plastics or rubber material. The sleeve may be fixed to the shaft by use of a pin (fig 2, 60), staples or compression band, and one or more elongate slits (42) in the sleeve may also be provided.

Description

Improved handle The present invention is directed to an improved handle, in particular an improved handle for manual tools having a long cylindrical elongate handle wherein the tool is predominantly used by movement of the tool along the principal axis of the handle, i.e. that corresponding to its length. It has become increasingly apparent in recent years that when carrying out manual tasks, such as tasks using a tool, there is the risk of repetitive strain injury. Such injury may arise when a particular action is performed many times in a very similar manner. The risk of such injury is increased when the particular operation results in particular stress points, such as when a jarring or impact occurs at some point in the task. This is particularly so where it is necessary to grip a tool strongly so as to supply sufficient force to the tool to carry out its task. In such situations a user will tend to grasp a tool handle even harder when a jarring or impact is likely to occur so as to effectively use the tool, thus exacerbating the transfer of any jarring force to the user.

There is therefore the need for a means of reducing the risk of repetitive strain injuries, particularly when using tools subject to a jarring effect in use.

Further, this need is particularly present in such tools where it is not possible to readily form a specific handle grip since it may be necessary to hold the tool at a number of different positions, such as along the length of an elongate handle so as to use the tool in a number of different situations or by a number of different people, such as people of different height.

The present invention provides a handle for a manual tool the manual tool having an elongate handle, wherein, in use, the tool is used by movement of the tool in the direction of the principal axis of the handle wherein the handle comprises: i) a shaft having a principle axis in the direction of its length and a substantially constant cross-section perpendicular to the principal axis along an at least first portion of said length; ii) a sleeve around all or part of said first portion of said length; iii) an implement proximate at least one end of the shaft; means for retaining the sleeve on the shaft, such as by means of friction and/or a fastener; wherein the sleeve on the shaft forming the handle is configured so as to, in use, distort so as to absorb force when the tool, gripped by a user about the sleeve, encounters a jarring motion imparted along the principal axis of the handle.

The sleeve on the shaft forming the handle is configured so as to, in use, distort, that distortion is preferably by extension or lengthwise contraction, preferably by concertinaing, more preferably by extension most preferably concertina type extension.

Whilst the present invention is preferably applicable manual tools having no motive power (e.g. an electric or pneumatic motor) the present invention is considered useful for mitigating similar injurious effects in motorised manual tools, such as from vibration effects in pneumatic tools and vibratory tools such as compaction plates.

The manual tool is preferably a hand tool.

The present invention is particularly applicable to tools predominantly used by movement of the tool along the principal axis of the handle of the tool (i.e. the length of a handle is the main dimension and thus defines the principle axis). An example of this includes a broom or a wheelbarrow.

A preferred manual tool in which the present invention may be incorporated is a tool selected from a broom, wheelbarrow, a hoe, a garden fork, a pick axe and a spade, preferably wherein those tools are not in the form were in the handle has a lateral crosspiece, such as at an upper end of the tool. The implement is therefore, respectively, a brush head, the bucket of a wheelbarrow, a hoe blade, a fork, the head, or the blade of a spade. The preferred implement is a brush head or wheelbarrow, most preferred is a hoe. An example of a shaft for use in the present invention would be a broom stave, that is an elongate cylindrical shaft. The stave is preferably made of An example of a sleeve for use in the present invention is a plastics material which is resiliently deformable. The sleeve may comprise one or more elongate slits in the sleeve, such as a single elongate slits traversing the length of the sleeve so that the sleeve may be opened and clipped' around a shaft thus enabling use with an existing shaft having enlarged ends over which a sleeve of my not otherwise be readily slid.

When the sleeve is secured to the shaft by means of a fastener it is essential that the sleeve is elastic in nature. This enables the sleeve to stretch, or be compressed, so as to absorb force, such as an impact on the implement. It is preferable that the sleeve is able to stretch as the force applied to the sleeve can then be more evenly distributed around the shaft as kinking of the sleeve can occur upon compression. The sleeve is preferably capable of changing length by means of a concertina action, be that from such as a zigzag or preferably a castellated profile, which has fewer pressure points on the hands, implicit in the concertina profile being angularity.

The sleeve is preferably made of a plastics material, the plastics material of the sleeve when secured to the shaft by means of a fastener may be a rubber, such as butyl rubber or natural rubber. By rubber is meant a material being substantially elastically deformable, such as preferably defined by having a Young's modulus of less than 1 Gpa, more preferably less than 0.5GPa, most preferably in the range 0.01 to 0.1GPa.

When the sleeve is retained upon the shaft by friction the coefficient of friction between the sleeve and shaft is preferably greater than 0.2, more preferably greater than 0.3 most preferably in the rate range 0.4 to 0.8. This enables the sleeve to slide along the slack shaft to some extent but not so readily as to make the handle ineffective for transferring force from a hand gripping the sleeve to the shaft such as to provide a useful amount of work at the implement.

However, it has been found that when a concertina profile is used a less elastomeric material may be used, such as polypropylene or polyethylene. Such materials have a lower coefficient of friction and bind less on the shaft, thus giving a more effective handle.

When the sleeve is retained upon the shaft by means of a fastener the coefficient of friction between the sleeve and the shaft is preferably less than 0.3, and preferably in the range 0.2 to 0.1, in which region it is possible to modify the force applied to the implement by means of gripping the sleeve attached to the shaft by gripping the sleeve more tightly whilst the sleeve makes still slides along the shaft so as to make use of the elasticity of the sleeve.

When the sleeve is retained upon the shaft by means of a fastener the internal radius of the sleeve is preferably from 5 to 10% greater than the external radius of the shaft.

This enables the sleeve to readily traverse the shaft without the sleeve being unduly distorted when gripped. Further, the external diameter of the sleeve is preferably no more than 10 to 20% greater than the external diameter of the shaft. The sleeve is therefore more readily capable of the distortion to facilitate grip by a user. If the sleeve does not encompass the full length of the shaft then such a size disparity also means that it is practical to grip both the sleeve and the shaft as alternatives without one being too large or too small.

The fastener may be in the form of a pin or pins, a staple or staples or a compression band or bands (such as a steel band). A compression band is preferred as this does not require penetration of the shaft.

The diameter of the shaft of the present invention is in the region of 1 cm to 5 cm, preferably in the range 2 to 4 cm.

By a jarring motion is meant the effect of an impact or other sudden change in force.

By the term "to absorb force" is meant the conversion of force, such as from the jarring motion in to an elastic deformation of the sleeve and/or in to heat dissipation by frictional movement of the sleeve along the shaft, which ever are/is relevant is defending upon the particular construction of the handle. Further, the amount of force intended by this phrase is in the order of 25%, preferably 50% or more of the increase in force over the force applied to the sleeve along the principal axis of the handle prior to the jarring action.

In one embodiment of the present invention the handle the handle of a manual vibratory tool, in which case the sleeve may preferably be secured at either end and be of concertina profile. This acts to effectively absorb small but violent movements effectively. The shaft may be formed of a metal tube. The sleeve is conveniently able

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to distort so as to take up imperfections of distortions in the shaft and yet still function.

The present invention will now be illustrated by means of the figures which illustrate preferred embodiments of the present invention and in which: Figure 1 shows a broom utilising a handle of the present invention; Figure 2 shows a cross section through a sleeve and that sleeve when applied to an inner handle or stave: Figure 3 shows the present invention in operation when applied to a broom; and Figure 4 shows the present invention in operation when applied to a hoe.

Figure 1 shows a broom 10 utilising the present invention, the broom 10 comprises a head 20 in the form of a conventional bush and from the head 20 extends a cylindrical stave 30 around which is wrapped a sleeve 40. Figure lB shows a cross-section of the handle comprising cylindrical stave 30 surrounded by sleeve 40. The sleeve 40 is retained on the stave 30 and is in movable frictional engagement with the sleeve 40 such that when a user gripping sleeve 40 exerts a predetermined force along the principal axis of the handle 52 static friction is overcome and the sleeve 40 rides along the stave 30 so as to absorb any impact.

Figure 2A shows one embodiment of the sleeve 40 in cross-section (perpendicular to the principal axis of the sleeve), the sleeve having longitudinal slits 42 such that a user using the device can effects the force exerted by the sleeve 40 on the stave 30 such that both static and dynamic friction are increased and hence the user has some degree of control over how easily the sleeve 40 slides along the stave 30. By increasing grip on the sleeve 40, slit 42 is closed and the sleeve 40 will grip the stave 30 more strongly in the area at which the pressure is applied.

Figure 28 shows a further cross section, perpendicular to the principal axis of the handle 50, adjacent the upper end 44 of the sleeve 40 were the sleeve 40 is optionally secured to the stave 30 by means of pin 60. The pin may preferably be in the form of one or more staples for ease of manufacture and duplication of the securing points.

Pin 60 penetrates the sleeve 40 and the stave 30 so as to be secured in the stave 30 and retain the sleeve 40 at its upper end 44 in place on the stave 30. This feature is optionally combined with the longitudinal slits 42 for the reasons mentioned above. In embodiment of the invention in which the sleeve 40 is secured at an upper and 44 to the stave 30 the sleeve need not be in direct contact with the stave 30 throughout its length as the sleeve is retained on the stave by a fixing means such as pin 60 or compression collar (not shown).

The sleeve 40 is preferably resiliently deformable along its principal axis, for which purpose the sleeve has, optionally, a castellated or wavy, preferably castellated profile having raised regions 46 and depressed regions 48 (i.e. a concertina profile) such as to increase the effective surface area of the sleeve 40 and therefore to increase the potential for elastic extension of the sleeve 40 when slid longitudinally along the principal axis of the stave 30, such as when the tool is used manually and gripped at a point on the sleeve below position 44 at which it is secured to the stave 30.

Figure 3 shows the effect of the invention in use. The tool is positioned as it would be when held by a user the user gripping sleeve 40 and pushing forwards and downwards pushes the broom 10 along a floor to sweep in a conventional manner. In use, on impacting an obstacle 60 the broom will come to an abrupt halt but the hands of the user will not need to absorb the shock of the impact as sleeve 40 will elongate in a section between where the user (not shown) grips the sleeve 40 and the retaining part 48 at the upper end 44 of the sleeve, thus absorbing energy and protecting the user from the shock of the impact. On moving the tool 10 back again the elasticity of the sleeve 40 will serve to restore the sleeve 40 in to its original position and the user can continue pushing in a conventional manner. The provision of an elongate slits 42 enables the user to continue to apply a high level of force, a level of force greater than that which would otherwise cause elastic extension of the sleeve 40, when the user gripped the sleeve 40 tightly so as to create additional static and/or dynamic friction between the sleeve 40 and the stave 30 over that under a light grip.

Figure 4 shows an application of the present invention to a hoe 100 the sleeve 140 is wrapped around the stave 130 in one of the embodiment of the present invention as described above, preferably in the form of a resilient tube attached at an upper end 144 of the sleeve to the stave 130, the resilient tube optionally being deformable by the grip of a user.

Claims (4)

1. Claims 1. A handle for a manual tool the manual tool having an elongate handle, wherein, in use, the tool is used by movement of the tool in the direction of the principal axis of the handle wherein the handle comprises: i) a shaft having a principle axis in the direction of its length and a substantially constant cross-section perpendicular to the principle axis along an at least first portion of said length; ii) a sleeve around all or part of said first portion of said length; iii) an implement proximate at least one end of the shaft; means that for retaining the sleeve on the shaft, such as by means of friction and/or a fastener; wherein the sleeve on the shaft forming the handle is configured so as to, in use, distort so as to absorb force when the tool, gripped by a user about the sleeve, encounters a jarring motion imparted along the principal axis of the handle.
2. 2. The handle of claim one when the tool is a broom.
3. 3. A broom comprising the handle of claim 1.
4. 4. A hoe comprising the handle of claim 1.