WO2003049911A2

WO2003049911A2 - Hand tool

Info

Publication number: WO2003049911A2
Application number: PCT/GB2002/005608
Authority: WO
Inventors: Peter James Walters
Original assignee: Sheffield Hallam University
Current assignee: Sheffield Hallam University
Priority date: 2001-12-11
Filing date: 2002-12-11
Publication date: 2003-06-19
Anticipated expiration: 2004-06-11
Also published as: GB0129587D0; AU2002350936A1; WO2003049911A3

Abstract

A hand tool (10) comprising a first handle section (12) having an integral fist jaw (14), a second jaw (18) pivotably mounted on the first handle section (12) and a drive lever (20) pivotable mounted on a second pivot (26) on the first handle section (12). Wherein the second jaw (18) and the drive lever (20) engage on another, and wherein movement at the drive lever (20) relative to the first handle section (12) is operable to cause movement of the second jaw (18).

Description

HAND TOOL

Field of the Invention

This invention relates to a hand tool, particularly, but not exclusively, a cutting hand tool.

Background to the Invention

Various studies have shown that the populations of western countries are aging and that the average wealth of the aging population is increasing also. Thus, there is a demographic shift towards older people with disposable income and also more free time than their younger counterparts. Much free time is spent gardening or in other DIY activities such as metal work.

It is also apparent that older users of hand tools typically have more difficulty using such tools due to age related problems such as disability or general weakening of hands, wrists and arms.

It has also been shown that the effectiveness and strength of a person's hand/wrist is optimised for using hand tools if they hold their wrist in a straight position, rather than the wrist being bent to one side or the other.

It is an object of the present invention to address the above-mentioned disadvantages. It is a further object of the present invention to provide a hand tool that increases the effective strength of a user's hand or wrist and/or is more comfortable to use.

Summary of the Invention

According to a first aspect of the present invention a hand tool comprises:

a first handle section having an integral first jaw;

a second jaw pivotably mounted on a a first pivot on the first handle section; a drive lever pivotably mounted on a second pivot on the first handle section, wherein the second jaw and the drive lever engage one another, and wherein movement of the drive lever relative to the first handle section is operable to cause movement of the second jaw.

The hand tool may include a second handle section pivotably mounted on the first pivot.

The drive lever may engage the second handle section, preferably at an end of the drive lever opposite to the second pivot. The drive lever may engage a slot in the second handle section. The slot may be provided to accommodate relative motion of the second handle section about the first pivot and the drive lever about the second pivot. Preferably, movement of the second handle section causes movement of the drive lever.

The drive lever and the second handle section preferably engage by means of intermeshing teeth. The engagement preferably provides a gear ratio between the drive lever and the second handle section, said gear ratio being in the region of between approximately 1.5 and 3 to 1 , more preferably 2 to 1.

Preferably, clockwise movement of the drive lever causes anticlockwise movement of the second jaw, and vice versa.

Preferably, the second jaw and the drive lever are both located on a first side, for example, a left side, of the hand tool. Thus, movement of the drive lever on the first side of the hand tool causes movement of the second jaw on the first side. An anticlockwise movement of the second handle section and/or the drive lever relative to and towards the first handle section preferably causes a clockwise movement of the second jaw relative to and towards the first jaw. The sense of rotation may be reversed in the previous statement. Thus in distinction to prior art hand tools such as pliers and secateurs, the movement of handles and jaw in the present hand tool occurs on the same side of the tool, as opposed to movement of a left hand causing movement of a right jaw in prior art devices.

Preferably, the first and second jaws are blades.

Preferably, the hand tool is a cutting tool.

Preferably, the second pivot is approximately in line with a closed angle made by the first and second handle sections at the first pivot.

Preferably, the first pivot includes a resilient bias adapted to urge the first and second handle sections apart, and thus preferably force the first and second jaws apart.

Preferably, the resilient bias is a torsion spring.

Preferably, the first and second jaw make an angle with the first and second handle sections.

Preferably, the angle made at the first pivot between an intersection of distal ends of the jaws and a closed angle of the first and second handle section at the first pivot is approximately in the region of 50° to 90°, more preferably approximately 60° to 80°, more preferably approximately 65° to 75°.

The jaws or blades may be curved.

The first handle section may have a hand protector, which may be in the form of a loop, into which a user may place his hand. According to a second aspect of the present invention, a hand tool comprises a first handle section having an integral first jaw;

a second jaw pivotably mounted on a first pivot on the first handle section; and

a second handle section pivotably mounted on the first pivot, wherein an angle made between an intersection of distal ends of the jaws and a closed angle of the first and second handle sections at the first pivot is approximately in the region of 50° to 90°.

According to a third aspect of the present invention, a hand tool comprises a first handle section with an integral first jaw;

a second jaw pivotably mounted on a first pivot on the first handle section and a second handle section also mounted on the first pivot, wherein a resilient bias is located at the first pivot and is operable to urge the first and second handle sections, and thus the first and second jaws apart.

The resilient bias may be located in a recess surrounding the first pivot.

The resilient bias is preferably a torsion spring.

All of the features disclosed herein may be combined with any of the above aspects, in any combination.

According to a fourth aspect of the present invention, a pair of wire cutters comprising a first handle member and a first jaw positioned in a substantially fixed orientation relative to each other:

a second handle section configured to be usable in combination with said first handle member; a second jaw member configured to be usable in combination with said first jaw member;

a plurality of pivots offset from each other and about which one or more of said members are mounted;

said hand tool characterised in that it comprises:

a drive lever pivotably mounted upon said first handle member at a first pivot;

said second jaw member pivotably mounted upon said first handle member at a second pivot;

wherein said second jaw member and said drive lever engage one another; and

wherein movement of said drive lever relative to said first handle member is operable to cause movement of said second jaw member.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Figure 1 is a schematic side view of a hand held cutting tool in a closed configuration;

Figure 2 is a schematic exploded view of the hand held cutting tool shown in Figure 1 ; Figure 3 is a schematic view form the side of the hand held cutting tool in an open configuration; and

Figure 4 is a schematic view of the forces acting on three levers of the cutting tool.

Detailed Description of the Best Mode for Carrying Out the Invention

There will now be described by way of example the best mode contemplated by the inventors for carrying out the invention. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.

A cutting tool 10 comprise a first handle 12 having an integral first blade 14, a second handle 16, a second blade 18 and a driving lever 20.

The first handle 12 and first blade 14 will be referred to as the first handle/blade portion 22.

The first handle/blade portion 22, the second handle 16 and the second blade 18 are all mounted on a first pivot 24. The mounting of the three parts on the first pivot 24 is shown schematically in Figure 2 by the dashed lines linking the three parts.

The driving lever 20 is mounted on a second pivot 26 located on the first handle/blade portion 22. The driving lever 20 also slidingly engages in a slot 28 in the second handle portion 16. The end of the driving lever 20 secured to the second pivot 26 has a head section 30 having teeth 32 arranged about the second pivot 26. The teeth 32 of the driving lever 20 are arranged to intermesh with corresponding teeth 36 located on a head section 34 of the second blade 18. The teeth 32 have a gear ratio of 2: 1 with the teeth 36.

A torsion spring 38 is located in a recess at the first pivot 24. The torsion spring urges the first and second handle sections 12 and 16 apart.

A keeper hook 40 is located at a distal end of the first handle section 12. It has a pivot mounting and is used to engage a pin 42 on the second handle 16 to hold the secateurs 10 closed when not in use.

The first blade 14 makes an angle of approximately 70° with the length of the first handle 12. Or more specifically, the angle at the first pivot 24 between the intersection of the first and second blade ends and a closed angle of the first and second angles 12, 16 at the first pivot 24 is approximately 70°.

The second pivot 26 line of a closed angle of the first and second handles 12, 16 at the first pivot 24.

In use, movement of the second handle 16 away form the first handle 12 causes rotation of the driving lever 20 about the second pivot 26 by virtue of the engagement in the slot 28. The teeth 32 of the driving lever 20 engage with the teeth 36 of the second blade 18 to thereby cause movement of the second blade

18 away form the first blade 14. The cutting tool 10 can then be used for cutting by moving the second handle 16 back towards the first handle 12, thereby causing movement of the second blade 18 towards the first blade 14 to therby allow the blades to cut by a shearing action, as is well known with existing secateurs and/or scissors. Releasing the handles 12, 16 causes separation thereof and of blades 14, 18 due to the action of the torsion spring 38.

Figure 3 shows a comparison between the action of the cutting tool 10 disclosed herein and the action of existing prior art secateurs.

The mechanical advantage offered by existing secateurs is provided by considering the ratio of moments between on the one hand a load 46 and the first pivot 24 and the location of effort at the point 44 and the first pivot 24 on the other hand. By using the measurements shown in Figure 3 a ratio of 50mm to 25mm, i.e. 2:1 is achieved.

Making the same comparison with the cutting tool 10 and taking an example effort force of 10 Newtons (N) the force shown by the arrow marked F acting on the driving lever 20 represented by F is driven by F=10 cos 17 = 9.6N. The moment around the second pivot and its teeth 32 is given by 9.6 N times 40 (the length of the driving lever 20 in millimetres) which equals 384Nmm.

For a gear ratio of 2:1 the moment around the larger gear, N equals 2x384 which equals 768Nmm.

Thus, the cutting force acting at 25 millimetres from the first pivot 24 is 768 divided by 25 which equals 30.72N. Thus, the mechanical advantage is 30.72 divided by 10 which equals approximately 3:1.

Thus, the cutting tool 10 described herein have a mechanical advantage of 3:1 , compared to a mechanical advantage of 2:1 for the same measurements of secateurs but driven by the existing single pivot method.

Figure 4 shows schematically the movement of the second handle 16 and the driving lever 20 relative to a schematic representation of the second blade 18. The diagram shows that when a 20° movement of the second handle 16 relative to the first pivot 24 is made the representation of the blade 18 moves by 15° about the first pivot 24. Similarly a movement of the handle 16 through 40° results in a movement of the second blade 18 of 30°. Thus, the mechanical advantage of 3:1 discussed above is shown in the relative movement of the second handle 16 and the second blade 18.

Also, Figure 4 shows more clearly how the relative movement of the first handle 16, the driving lever 20 and the second blade 18 is achieved.

The cutting tool 10 described herein have a number of significant advantages.

Firstly, the use of a compound lever in the form of the driving lever 20 acting on the second blade 18 provides a significant mechanical advantage over existing secateurs. This has the advantage, particularly for people with weak arms or wrists, that to achieve the same cutting force as obtainable with prior art cutting tools less force needs to be exerted by the user.

Also, the angle between the blades 14, 18 and the handles 12, 16 advantageously allows a user to keep his wrist straight whilst operating the cutting tool 10. This allows the user to use the cutting tool in a more comfortable manner. Also, his wrist is used to maximum effect at its strongest. The angle of 70°, or more generally in the range of 60° to 90°, is found to be advantageous.

The provision of a torsion spring 48 at the first pivot 24 is also advantageous in keeping the spring out of harms way, compared to the usual expansion spring creating an arc between the two handles in the prior art secateurs. The latter having the disadvantage that it is easy for a user to trap their finger or part of their hand in the gap between the handles close to the spring. The inventors believe such a cutting tool 10 described herein would be suitable for cutting many materials and would be particularly suited to use as garden secateurs or high tensile wire cutters.

Claims

Claims:

1. A hand tool comprises:

a first handle section having an integral first jaw;

a second jaw pivotably mounted on a first pivot on the first handle section;

a drive lever pivotably mounted on a second pivot on the first handle section, wherein the second jaw and the drive lever engage one another, and wherein movement of the drive lever relative to the first handle section is operable to cause movement of the second jaw.

2. A hand tool as claimed in claim 1 , which includes a handle section pivotably mounted on the first pivot.

3. A hand tool as claimed in claim 2, in which the drive lever engages the second handle section, at an end of the drive lever opposite to the second pivot.

4. A hand tool as claimed in claim 3, in which movement of the second handle section causes movement of the drive lever.

5. A hand tool as claimed in any one of claims 2 to 4, in which the drive lever and the second handle section engage by means of intermeshing teeth.

6. A hand tool as claimed in any preceding claim, in which clockwise movement of the drive lever causes anticlockwise movement of the second jaw, and vice versa.

7. A hand tool as claimed in any preceding claim which the second jaw and the drive lever are both located on the first side of the hand tool.

8. A hand tool as claimed in any preceding claim which is a cutting tool.

9. A hand tool as claimed in any preceding claim which is configured for the use as a high tensile wire cutter.

10. A hand tool as claimed in any preceding claim which is configured for use as a garden secatuers.

11. A hand tool as claimed in any preceding claim, in which the second pivot is approximately in line with a closed angle made by the first and second handle sections at the first pivot.

12. A hand tool as claimed in any one of claims 2 to 11 , in which the first pivot includes a torsion spring adapted to urge the first and second handle sections apart, and thus force the first and second jaws apart.

13. A hand tool as claimed in any one of claims 2 to 12 in which the first and second jaws make an angle with the first and second handle sections.

14. A hand tool as claimed in claim 13, which the angle made at the first pivot between an intersection of distal ends of the jaws and a closed angle of the first and second handle sections at the first pivot is approximately in the region of 50° to 90°.

15. A hand tool comprises a first handle section having an integral first jaw;

a second jaw pivotably mounted on a first pivot on the first handle section; and a second handle section pivotably mounted on the first pivot wherein an angle made between an intersection of distal ends of the jaws and a closed angle of the first and second handle sections at the first pivot is approximately in the region of 50° to 90°.

5

16. A hand tool comprises a first handle section with an integral first jaw;

a second jaw pivotably mounted on a first pivot on the first handle section 0 and a second handle section also mounted on the first pivot, wherein a resilient bias is located at the first pivot and is operable to urge the first and second handle sections, and thus the first and second jaws, apart.

17. A hand tool as claimed in claim 16, in which the resilient bias is 5 located in a recess surrounding the first pivot.

18. A hand tool as claimed in either claim 16 or claim 17, in which the resilient bias is a torsion spring.

0 19. A hand tool substantially as described herein with reference to the accompanying drawings.

20. A pair of wire cutters comprising a first handle member and a first jaw positioned in a substantially fixed orientation relative to each other: 5 a second handle section configured to be usable in combination with said first handle member;

a second jaw member configured to be usable in combination with said first o jaw member; a plurality of pivots offset from each other and about which one or more of said members are mounted;

said hand tool characterised in that it comprises:

5 a drive lever pivotably mounted upon said first handle member at a first pivot;

said second jaw member pivotably mounted upon said first handle l o member at a second pivot;

wherein said second jaw member and said drive lever engage one another; and

15 wherein movement of said drive lever relative to said first handle member is operable to cause movement of said second jaw member.