WO1990000464A1

WO1990000464A1 - Hand tools

Info

Publication number: WO1990000464A1
Application number: PCT/GB1989/000798
Authority: WO
Inventors: Jacek Lech Basista; Stephen Paul Hughes; Ian Ellis Wood
Original assignee: James Neill Holdings Plc
Priority date: 1988-07-13
Filing date: 1989-07-13
Publication date: 1990-01-25
Also published as: GB8816604D0; AU4035289A; GB2220606A

Abstract

A hand tool has two jaws, which may be cutters and which are pivotally interconnected, each jaw having a respective member extending beyond the pivot, and a force amplifying lever which is pivotally connected to one of the members at a point remote from the jaws and is so coupled to the other member that, upon pivotal movement of the force amplifying lever relative to the one member, the jaws are moved relative to one another.

Description

HAND TOOLS

This invention relates to hand tools, including for example secateurs and other cutting or shearing tools, and pliers and other gripping tools.

Such tools commonly have two jaws or cutters carried on respective operating members which are pivotally con¬ nected and have handgrip portions associated with the jaws or cutters.

Whilst the disposition of the handgrip portions relative to the jaws or cutters and the pivotal connection of the operating members is such that a useful amplication of the hand forces applied to the handgrip portions is provided in these known arrangements, such arrangements suffer from the disadvantage that the first and second fingers of a user's hand (the strongest fingers) engage the handgrip portions at positions of the least leverage, so that the first and second fingers contribute less effectively than the other fingers to the production of the closing forces which are applied to the jaws or cutters by a user.

The present invention seeks to overcome this dis¬ advantage.

In an embodiment of the present invention to be described, a hand tool has first and second jaws or cutters which are operable by first and second pivotally connected operating members respectively, the first operating member having a portion to be gripped by a user's hand and the second operating member being coupled to a force amplifying lever which is pivotally connected to the first operating member at a position remote from the jaws or cutters, the arrangement being such that a squeezing hand pressure applied between the first operating member and the force amplifying lever causes the jaws or cutters to be closed.

The second operating member may be coupled to the force amplifying lever by a pivot means which is carried by the second operating member and is slidably engaged with the force amplifying lever.

The pivot means may be constituted by a curved pivot surface formed at the free end of the second operating member and arranged to slide along a slideway formed in the force amplifying lever.

Alternatively, the pivot means may comprise a pivot pin carried either in an operating member and arranged to slide along a slideway formed in the force amplifying lever, or In the force amplifying lever and arranged to slide along a slideway in an operating member.

The coupling of the second operating member with the force amplifying lever may, on the other hand, be provided by a link which is pivotally connected at its ends to the second operating member and the force ampli- fying lever respectively.

Other features of the present invention will become apparent from a reading of the description that follows hereafter.

Various embodiments of the present invention will now be described by way of example and with reference to the accompanying diagrammatic drawings in which: -

Figures 1 and 2 show in similar part-sectional views a first pair of secateurs with its cutting members in the closed and open conditions respectively;

Figures 3, 4 and 5 show in similar part-sectional views a second pair of secateurs with its cutting members in closed, open and intermediate conditions respectively;

Figure 6 shows in a modification of Figure 3 a modi¬ fication of part only of the secateurs of Figure 3;

Figure 7 shows an external view of a third pair of secateurs with its cutting members in the open condition; and

Figure 8 shows an external view of a fourth pair of secateurs with its cutting members in the open condition.

For convenience and simplicity's sake, in the des¬ cription that follows corresponding parts in the various embodiments will be accorded the same reference number. Referring now to the Figures 1 and 2, two cutter operating members 10, 12 carry integral cutting members 14, 16 (hereafter referred to as "cutters") and are pivotally connected by a pin 18. The operating member 10 has a U-shaped cross section, and the member 12 is sandwiched between the side plates of the member 10.

Remotely from the cutters 14, 16, the member 10, carries a handgrip 20, and has an extension 22 in which is secured a pivot pin 24.

A force amplifying lever 26 (likewise of U-shaped cross section) is pivotally carried on the pivot pin 24, and extends towards the cutters. A curved free end 28 of the operating member 12 rests in a slot 30 defined by the side plates of the lever 26, and is retained there by a guide pin 32 secured in the lever 26.

A locking latch ("safety catch") 34 is pivoted on the operating member 10 and when in the position shown serves to hold the free end of the lever 26 in the "cutters- closed" position, and the cutters in the closed condition when they have been brought to that condition.

The cutters are biased to the open condition as shown in Figure 2 by a leaf spring 36 which is secured in the first operating member 10, and of which the free end bears against the second operating member 12.

The free end of the force amplifying lever 26 is shaped to form a handgrip 38 in which the first and second fingers of the user's hand may engage.

The handgrip 20 of the first operating member 10 is shaped in the manner shown so as to fit snugly into the angle between the thumb and fore-finger of the user's hand.

The abutting surfaces of the curved end 28 of the second operating member 12 and the lever 26 act in the manner of a loose pivotal coupling 40 which permits movement of the pivot position along the lever 26 as the cutters move between their extreme positions.

The shape of the curved end 28 of the operating mem¬ ber 12 may be varied to provide any desired relationship between the pivotal movement of the lever 26 and the travel of the cutters 14, 16.

The use of the lever 26 pivoted at a position remote from the cutting blades enables the strong first and second fingers of the user's hand to apply a blade-closing pres¬ sure at a position of maximum leverage, instead of (as in the case of a conventional pair of secateurs) at a position of minimum leverage.

Moreover, the movement of the curved end 28 of the operating member 12 along the lever 26 towards its fulcrum pin 24 progressively enhances the leverage of those two

I fingers as the blades close together. Thus, with this arrangement the first and second fingers contribute more effectively than hitherto to the blade-closing force applied to the cutters through the operating members 10 and 12.

Referring now to the Figures 3 to 5, the secateurs shown there are of a construction generally similar to that of the secateurs of the Figures 1 and 2, and have -

(a) first and second blade operating members 10, 12 carrying cutting blades 14, 16 and being pivotally connected by a pivot pin 18;

(b) a force amplifying lever 26 pivotally connected to the extension 22 of the first operating member 10 at a pin 24, and to the free end of the second operating member 12;

(c) a biasing spring 36; and

(d) a locking latch 34.

However, in this embodiment, the slidable pivotal connection of the lever 26 with the second operating member 12 has been replaced by a fixed pivotal connection provided by a pivot pin 50 which passes through both the lever 26 and the operating member 12. The loose pivotal coupling has been transferred to the pivot pin 24 in that it is secured in the end of the lever 26 and is arranged to slide in open-ended slots 52 formed in the extension 22 of the operating member 10. The secateurs of Figures 3 to 5 may be modified in the manner shown in Figure 6, so as to incorporate a retractable limit stop for limiting the travel of the cutter 16 relative to the cutter 14,when the user relaxes his squeezing pressure on the handgrip portions, to a pre¬ determined proportion of the maximum cutter travel.

In the modification of Figure 6, the limit stop is constituted by a transverse pin 54 which is carried by a two-position rocker switch 56, which is itself pivotally mounted in the operating member 10. In one position of that switch, the pin 54 occupies the position indicated, in which position it lies in the arcuate path of an abut¬ ment 58 formed on the operating member 12, and prevents further movement of the cutter 16 beyond a predetermined intermediate position.

Movement of the switch to its alternative position withdraws the limit pin 54 from the path of the abutment 58, so that the cutters may move to their fully-open condition.

In the arrangement of Figure 7, the construction, of the secateurs is generally analogous to that of the Figures 1 and 2. However, in this embodiment the pivotal coupling of the force amplifying lever 26 with the free end of the second operating member 12 is by way of a pivot pin 60 which is secured in the operating member 12 and which is slidably engaged in an arcuate slot 62 formed in the lever 26 .

In the arrangement of Figure 8, the construction is generally similar to that of the Figures 1 and- 2. However, in this embodiment the pivotal coupling of the second operating member 12 with the lever 26 takes the form of a short link 64 which is pivotally connected at its respec¬ tive ends with the operating member 12 and the lever 26 respectively.

Whereas in the above embodiments,the secateurs are shown to be of the "anvil type" in which a single cutter blade 16 carried by the operating member 12 is brought into cutting contact with a cutter anvil 14 of a softer material carried by the operating member 10, in other forms of secateur (the "by-pass type"), one cutting blade 16 operated by operating member 12 is brought into over¬ lapping, shearing relationship with another cutting blade 14 operated by the operating member 10.

Whereas the above embodiments of the present invention have comprised secateurs, the invention may equally well be applied to other forms of cutting tool, and moreover to pliers and other forms of gripping tool. In the latter case, the cutter blades 14, 16 of the secateurs would be replaced by appropriately-shaped jaws for gripping objects.

It will be understood that, although the invention has been described, by way of example, with reference to particular embodiments, variations and modifications may be made within the scope of the invention.

Claims

1. A hand tool including a first jaw or cutter, a first member associated with the first jaw or cutter, a second jaw or cutter, a second member associated with the second jaw or cutter, the first and second jaws or cutters being pivotally interconnected, and a force amplifying lever, the force amplifying lever being pivotally connected to one of the members at a point remote from the jaws or cutters and being so coupled to the other member that, upon pivotal movement of the force amplifying lever relative to the one member, the first and second jaws are moved relative to one another.

2. A hand tool as claimed in claim 1 in which the first and second jaws are moved relative to one another con¬ tinuously by an amount dependent upon the pivotal movement of the force amplifying lever relative to one of the members.

3. A hand tool as claimed in claim 1 or claim 2 in which the force amplifying lever is slidably engaged with the one member.

4. A hand tool as claimed in any one of the preceding claims in which the force amplifying lever is pivotally coupled to the other member by a curved pivot surface of the other member and in which the curved pivot surface slides on the force amplifying lever.

5. A hand tool as claimed in any one of claims 1 to 3 in which the force amplifying lever is pivotally coupled r to the other member by means of a pivot pin.

6. A hand tool as claimed in claim 5 in which the pivot pin slides in a slot in either the force amplifying lever or the other member.

7. A hand tool as claimed in any one of claims 1 to 3 in which the force amplifying lever is pivotally coupled to the other members by means of a link which is pivotally connected at its ends to the force amplifying lever and the other member respectively.

8. A hand tool as claimed in anyone of the preceding claims including means which are adjustable to limit the amount of the relative movement between the first and second jaws.