GB2119695A

GB2119695A - Pliers

Info

Publication number: GB2119695A
Application number: GB08212921A
Authority: GB
Inventors: Kenneth Robert Scott
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-05
Filing date: 1982-05-05
Publication date: 1983-11-23

Abstract

A pair of pliers has two body members 1, 2 each comprising a handle 3, 4 a pivot portion 5, 6 and a jaw portion 7, 8 and which are of glass sphere filled nylon material. The members are pivoted together by a pivot pin 9. Mating faces of the pivot portions define an annular chamber in which is accommodated a coil spring 17 for biassing the jaw portions 7, 8 together as shown. The jaw portions are provided with metallic jaw elements 29, 30 holding circlip engaging pins 33. <IMAGE>

Description

SPECIFICATION Pliers The present invention relates to a pair of pliers.

Traditionally pairs of pliers have been made of steel. Recently, pliers have been produced with their metallic handles sheathed with plastics or rubber material or with entire handles of moulded plastics material into which is forced a tang of a vestigial metal handle. Such pliers are of particular usefulness to electricians on account of the insulating nature of their handles.

Where in specialised pliers, such as circlip pliers, it is desirable to incorporate a spring to bias the jaws of the pliers to an open, or closed, position, it has been usual practice to utilize an external spring acting between the handles of the pliers. Such an arrangement is shown in United States Patent Specification No. 4,023,450 where a spring acts between the remote ends of the handles. This pair of pliers has its handles and jaws moulded as unitary members of plastics material. It is a little duty pair of pliers in which the jaws are designed to deflect to restrict the force which can be applied with the jaws.

The pliers of present invention have been developed to provide an improved design of pliers.

According to the invention, there is provided a pair of pliers comprising: two unitary body members of moulded plastics material, each member incorporating a handle, a pivot portion and a jaw portion; a pivot pin pivotally connecting together the body members at the pivot portions; an annular chamber defined by the pivot portions around the pivot pin axis; a spring accommodated in the annular chamber and. biasing the handles apart; and two metallic jaw elements, each being attached to its own jaw portion.

Arrangement of the spring in an annular chamber around the pivot pin axis is particularly convenient because the pivot pin should normally be larger than it might be in all metal-pliers to keep the stresses acceptably low for the plastics material. Further, to keep the stresses low it is expeditious for the pivot portions to have a greater diameter, radially from the pivot pin axis, than in all metal pliers. Thus a convenient position for the spring in the annular chamber is available.

Although it is envisaged that they may differ, preferably the two unitary body members are identical with the annular chamber being formed as a recess in a mating face of each member.

Making the body members identical has the advantage that separate moulds are not required, which is not only economical but assists in ensuring the body member mate correctly.

Although other arrangements are envisaged to be possible, preferably the metallic jaw elements are conveniently attached in recesses in the opposed faces of the jaw portions. Conveniently the jaw elements are actually attached by rivets passed through side parts flanking the recesses and the jaw elements themselves. The jaw elements are conveniently machined from rectangular stock and the recesses are then rectangular to match.

Preferably the pivot pin comprises a male part and a female part having a spigot diametrically dimensioned to be freely rotatable in the pivot portions. Conveniently the length of the spigot is such that when the parts are press-fitted together the separation of two heads, one on each part, is such that the pivot portions are held closely together without binding. This has the advantage that a closely controlled force is not required to obtain the correct separation of the heads. It is envisaged that the spigot could abut a suitable recess in or extension from the male head as opposed to the under-surface thereof.

The handles are conveniently of I-beam crosssection for economy of material and good stress distribution.

To help understanding of the invention a pair of pliers in accordance therewith will now be described with reference to the accompanying drawings in which Figure 1 is a plan view of the complete pair of pliers; Figure 2 is a cross-section on the line Il-Il in Figure 1; Figure 3 is a cross-section on the line Ill-Ill in Figure 1; Figure 4 is a cross-section on the line IV--IV in Figure 1; Figure 5 is a plan view of one of the body members of the pair of pliers of Figure 1; Figure 6 is a view similar to Figure 4 of one of the body members of a modified pair of pliers, and Figure 7 is a view similar to Figure 5 of an alternative pivot pin for use in the pair of pliers.

Referring first to Figures 1 to 5, the pair of pliers has two unitary body members 1, 2, each including a handle 3, 4, a pivot portion 5, 6 tthe portion 6 being hidden below the portion 5) and a jaw portion 7, 8. The body members 1, 2 are of glass sphere filled nylon, although other plastics materials may be used. A pivot pin 9 extends through central apertures 10, 11 in the pivot portions, pivotally connecting the portions and holding them together with its heads 1 2.

In mating faces 13, 14 of the pivot portions are provided annular recess 15, 16 which together form an annular chamber accommodating a coil spring 17. Each end 18, 1 9 of the spring engages in a notch 20, 21 in its own pivot portion whereby the handles 3, 4 are biassed apart. In this pair of pliers this sense of bias biasses the jaw portions 7, 8 apart. Stops 22, 23 are moulded on the opposed sides of the handles adjacent the pivot portions to limit the approach of the handles towards each other. To limit the movement of the body members in the opposite direction abutments 24 between each jaw portion and the other body member's handle are provided.

The jaw portions 7, 8 have recesses 25, 26 in their opposed faces 27, 28 in which recesses are received metallic jaw elements 29, 30. Each jaw element is attached in position by a pair of rivets 31 extending through the side parts 32 flanking the recesses 25, 26. As shown the jaw elements are provided with circlip engaging pins 33 locked in bores 34 by grub screws 35. However, the jaw elements could be provided with cutter blades to strip electric cable for instance.

The handles are of I-beam cross-section as shown in Figure 5.

Figure 6 shows one of the body members 1, 2.

Figure 7 shows a- similar body member for a pair of circlip pliers for opening an external circlip as opposed to for closing an internal circlip as the pliers of Figure 1 are intended. it will be appreciated that identical jaw elements can be used with either form of pliers which is an economy.

Figure 7 shows an alternative pivot pin 40 which may replace the conventional-rivet type pin 9. Pin 40 comprises a male part 41 and a female part 42, each having heads 43 which hold the pivot portions 5, 6 of the pliers together. The female part 42 has a spigot 44 having a central axial bore 45. The outside diameter of the spigot 44 is a clearance fit in the central apertures 10, 11 in the pivot portions. The male part has a stem 46 which is an interference fit in the female bore 45.

When the parts 41, 42 are assembled together, the stem 46 is pushed into the bore 45 until the end 47 of the female spigot abuts the underside of the head of the male part 41, whereby the gap between the two heads is controlled to avoid binding of the pivot portions 5, 6. A clearance 48 is provided between the end of the stem and the bottom of the bore 45.

The invention is not intended to be restricted to -the described embodiments. For instance it is possible for a nut and bolt type pivot pin to be used.

Claims

1. A pair of pliers comprising: two separate unitary body members of moulded plastics material, each member incorporating a handle, a pivot portion and a jaw portion; a pivot pin pivotally connecting together the body members at the pivot portions; an annular chamber defined by the pivot portions around the pivot pin axis; a spring accommodated in the annular chamber and biasing the handles apart; and two metallic jaw elements, each being attached to its own jaw portion,

2. A pair of pliers as claimed in claim 1 wherein the two body members are identical to each other, with the annular chamber being formed as a recess in a mating face of each body member.

3. A pair of pliers as claimed in claim 2 wherein a notch is provided opening into the recess in each body member for holding a respective end of the spring.

4. A pair of pliers as claimed in claim 1, claim 2 or claim 3 wherein the spring biasses the jaw portions together and the jaw portions are moved apart on closure together of the handles.

5. A pair of pliers as claimed in claim 1, claim 2 or claim 3 wherein the spring biasses the jaw portions apart and the jaw portions are moved together on closure together of the handles.

6. A pair of pliers as claimed in any preceding claim wherein each pivot portion is provided with a respective stop for restricting closure of the handles so that the handles do not meet.

7. A pair of pliers as claimed in any preceding claim wherein the two body members are of glass sphere filled nylon material.

8. A pair of pliers as claimed in any preceding claim wherein the jaw portions each have a recess in a respective opposed face, the jaw elements being attached to the recesses.

9. A pair of pliers as claimed in claim 8 wherein each jaw element is retained in its recess by one of more rivets passing through side parts of the jaw portion flanking the recess and through the jaw element.

10. A pair of pliers as claimed in claim 8 or claim 9 wherein the jaw elements are machined from rectangular stock and the recesses are complementarily rectangular.

11. A pair of pliers as claimed in any preceding claim wherein the pivot pin comprises a male part and a female part press-fitted together, the female part having a spigot with a diameter such that the pivot pin is freely rotatable in the pivot portions, the male part and/or the female part being so dimensioned that a head on the female part and a head on the male have a predetermined separation on press-fitting together so that the body parts are not bound together.

12. A pair of pliers as claimed in claim 11 wherein the spigot of the female part is dimensioned to provide the said predetermined separation by abutment with the male part, the male part having a stem shorter than a bore in the spigot in which the stem engages whereby the stem does not interfere with the said predetermined separation.

13. A pair of pliers as claimed in any preceding claim wherein the jaw elements each hold a respective circlip opening pin.

14. A pair of pliers substantially as hereinbefore described with reference to Figures 1 to 5 of the drawings or as modified in Figure 6 or as modified in Figure 7.