WO2005105380A1

WO2005105380A1 - Pliers

Info

Publication number: WO2005105380A1
Application number: PCT/SE2005/000612
Authority: WO
Inventors: Gustav Jansson
Original assignee: Gustav Jansson
Priority date: 2004-04-29
Filing date: 2005-04-28
Publication date: 2005-11-10
Also published as: SE526071C2; SE0401100L; SE0401100D0; DE112005000982T5

Abstract

A pair of pliers with two hand grip shanks (2, 3) that are joined in a junction (8), around which the shanks may be pivoted in an opening and a closing direction, the pliers including an elongated opening spring, preferably a leaf spring, which has an opening effect on the shanks and which is strained when the shanks are moved towards each other. A first end of the opening spring is fixedly arranged on the inside of the first shank and the second end is adapted to slide along the inside of the second shank when the shanks are moved in the opening and in the closing direction. A lateral guide is arranged on the inside of the second shank (3), in which guide the second end (4B) of the opening spring may slide longitudinally along the shank.

Description

Pliers

BACKGROUND OF THE INVENTION

The present invention generally relates to a pair of pliers, and more specifically to a pair of pliers with two hand grip shanks joined at a junction, around which the shanks may be pivoted in an opening and a closing direction, the pliers including an elongated opening spring, preferably a leaf spring, which has an opening effect on the shanks and which is strained when the shanks are moved towards each other, a first end of the opening spring being fixedly arranged on the inside of the first shank and the second end being adapted to slide along the inside of the second shank when the shanks are moved in the opening and in the closing direction.

Pliers of this kind open automatically upon the effect of the spring when the hand grip on the shanks is loosened, whereby operation of the pliers is facilitated.

PRIOR ART US-A-4 739 552 shows an example of a known pair of pliers of this kind. The sliding end of the opening spring bears against the inside of the second shank by intermediation of a plastic sliding element, which is affixed onto the opening spring.

A problem with these known pliers and other similar ones, with or without sliding elements on the sliding free end of the opening spring, is that this end has a tendency to move laterally when the shanks are opened and closed. Under these conditions it may end up beside the second shank so that it no longer can transmit any opening force to this shank. Above all, it is the affixation of the stationary end of the opening spring that is critical. This has to do with the fact that the opening spring typically is fastened with a screw. Even when properly tightened, the screw has a tendency to gradually loosen somewhat due to the effect of the forces it is exposed to from the spring during repeated opening and closing movements, whereby the sliding end of the spring is able to move laterally. This tendency is particularly strong if the shanks are provided with an elastic plastic cover, against which the fixed end of the opening spring abuts.

SUMMARY OF THE INVENTION

An object of the present invention is to address this problem. That object is obtained with the pliers according to claim 1. With the solution in accordance with the invention the opening spring is limited to sliding only in the longitudinal direction of the shank.

Preferred embodiments of the invention are set forth in the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS

By way of example, a preferred embodiment of the invention will be described below with reference to the accompanying drawings, on which:

Figure 1 shows a pair of pliers according to the preferred embodiment of the invention, in an open position;

Figure 2 shows the pliers according to figure 1 in a closed position with a drawn opening spring;

Figure 3 shows the pliers according to figure 1 when the opening spring has opened the shanks;

Figure 4 shows in larger scale a part of the shank and the opening spring seen as indicated by arrow IV in figure 2; and Figure 5 shows a cross section along the line V-V in figure 4.

DETAILED DESCRIPTION OF THE INVENTION Figures 1-3 show the preferred embodiment of the pliers 1 according to the present invention in three different positions. Here, the pliers illustrated are a pair of cutting pliers. The pliers have two shanks 2, 3 that are pivotally connected at a junction 8 and have two cutting jaws 2A, 3 A at their front end. An elongated opening spring, represented as a leaf spring 4 in the figures, is at a first end 4A fixed to the inside of the first shank 2, in this case by means of a screw 5, and extends from the point of affixation at the screw 5 obliquely forward towards the inside of the second shank 3.

Here the term "opening spring" refers to a spring device that is fixed onto one of the shanks 2 and is adapted to glide on and yield against the other shank 3. A preferred embodiment of such a spring device is a leaf spring, which has been chosen in the illustrated preferred embodiment. Other conceivable embodiments, such as thread- or rod- shaped or other elongated resilient elements, are however also included in the concept of an opening spring. A leaf spring is advantageous as it is easily bent in the direction, in which resiliency is desired, i.e. the direction in which the shanks are reciprocally movable, while it is stiffer in the opposite direction.

In figure 1 , the shanks of the pliers are bent outwards in the maximum opening direction and is thus completely open, while no force is exerted on the opening spring 4, and the second end 4B of the spring, i.e. the end facing away from the point of affixation, does not reach the second shank 3, but is free. In figure 2, the pliers are completely closed and the opening spring 4 is put under maximum stress, i.e. as much stress as it can be put under during normal use of the pliers. In figure 3, the drawing force of the opening spring has brought the shanks 2, 3 of the pliers apart to an intermediate position where the free end 4B of the spring abuts on the shank 3.

In the shown preferred embodiment of the invention the opening spring is fixed to the first shank 2 at a point, a certain distance from the junction 8 and oriented obliquely forward in such a way that its contact surface against the second shank 3 is placed closer to the junction than the point of affixation.

Due to a slide guide, which is located where the opening spring 4 abuts on the second shank 3, the opening spring 4 is prevented from departing from its intended position when the shanks are brought together. In figures 4 and 5 a preferred embodiment of this slide guide is shown, which consists of a longitudinal track 6 formed by two sidewalls 10 and a base surface 11, and in which the second end 4B of the opening spring is able to slide. The base surface 11 is shaped like an arc seen from the side and forms a support against which the second end 4B of the opening spring may slide. The distance between the sidewalls 10 is somewhat larger than the width of the spring end 4B, which enables it to easily fit inside the track without touching the side walls. The opposing sidewalls 10 are, in the shown embodiment, essentially parallel with each other and extend in the longitudinal direction of the shank. However, the track may be formed in such a way that its width is larger at the end that is farthest from the junction 8 of the shanks, gradually decreasing towards the other, inner end of the track. Additionally, the track may be formed with a gradually decreasing width towards its base, making it wider at its opening than at its base. However, the opening spring is not intended to bear against the side walls other than when it, for some reason, parts from its sliding position and diverges laterally, as such abutment would increase the friction. Therefore, it is preferable that the base is slightly concave in the lateral direction of the shank, whereby the tendency of the opening spring to touch the sidewalls can be decreased.

The entire track may also be shaped in a form reminiscent of a part of an ellipsoid or other elongated oval body and thus lack well defined transitions between the base- and sidewalls. Throughout the duration of its abutment upon the shank 3, from when contact is first made until complete closing of the pliers, the free end 4B of the opening spring 4 should be within the track 6 in order to limit its lateral movement.

In another, not shown, embodiment, the guide consists of two elongated projections placed on the inside of the shank on either side of the contact surface of the opening spring, the track thus being formed out of the sidewalls of the projections and the surface between them.

In order to reduce friction between and wear of those surfaces of the opening spring 4 and the second shank 3 which come into contact with each other along the contact surfaces of the opening spring 4 and the second shank 3, i.e. the sliding end 4B of the opening spring 4 and the base surface 11 of the track, at least one of the surfaces may be provided with a coating of wear resistant and/ or friction reducing material. It may also be advantageous to provide the sidewalls of the guide member with such material so that the opening spring may slide smoothly against these, if it should diverge from its intended sliding path.

Preferably, the shanks are both provided with easy to grip casings 7, e.g. plastic casings, which preferably may be threaded onto the shanks. Such casings may complicate the affixation of the opening spring 4. The elasticity of the casing renders the attachment troublesome, as it introduces a certain play at the point of affixation of the spring. However, the guide member according to the present invention has proven itself effective even when the opening spring is fixed onto a resilient coating on the shank. Due to the fact that the opening spring 4, thanks to the guide member, is properly guided laterally and is always exposed to equal stresses when compressed, the efforts/ stress at the point of affixation will always be the same and will have no component that tends to turn the spring laterally. Thus, gradual deterioration or, in a worst case scenario, cessation of the affixation can be avoided.

The opening spring 4 is preferably affixed with a screw 5, which is arranged at a distance from the lower end of the spring and driven through the casing 7 of the first shank 2. A peg which is arranged below the screw, compensates for lateral movement of the opening spring and partly relieves the screw from stress. The design and stiffness of the spring may be adapted so that the pliers open to an adequate extent and with adequate force.

The invention is not limited to the preferred embodiment. Other embodiments within the scope of the invention as it is presented in the following claims are feasible.

Claims

1 A pair of pliers with two hand grip shanks (2, 3) that are joined in a junction (8), around which the shanks (2, 3) may be pivoted in an opening and a closing direction, the pliers including an elongated opening spring (4), preferably a leaf spring, which has an opening effect on the shanks (2, 3) and which is strained when the shanks are moved towards each other, a first end (4A) of the opening spring being fixedly arranged on the inside of the first shank (2) and the second end (4B) being adapted to slide along the inside of the second shank (3) when the shanks are moved in the opening and in the closing direction characterized in that a lateral guide is arranged on the inside of the second shank (3), in which guide the second end (4B) of the opening spring may slide longitudinally along the shank.

2 The pliers according to claim 1, characterized in that the lateral guide is formed of sidewalls (10) of a track (6) that extends longitudinally along the shank, in which track the second end (4B) of the opening spring is adapted to slide.

3 The pliers according to claim 2, characterized in that the sidewalls (10) of the track (6) are essentially parallel to the longitudinal direction of the second shank (3) and in that the track has an arcuate base (11) that forms a support for the second end (4B) of the opening spring (4).

4 The pliers according to claims 2 or 3, characterized in that the track (6) is widest at the end that is farthest from the junction (8) of the shanks (2, 3) and gradually narrows towards its other end.

5 The pliers according to claims 2, 3 or 4, characterized in that the track (6) is widest at its opening and gradually narrows towards its base (11).

6 The pliers according to any one of claims 2 to 5, characterized in that the base of the track is coated with a wear resistant and/ or friction reducing layer.

7 The pliers according to any one of the preceding claims, characterized in that said other end (4B) of the opening spring (4) is coated with a wear resistant and/ or friction reducing layer.

8 The pliers according to any one of the preceding claims, characterized in that the shanks (2, 3) are provided with a resilient casing (7), the opening spring (4) being arranged outside the casing.