WO2008101259A1

WO2008101259A1 - Locking pliers

Info

Publication number: WO2008101259A1
Application number: PCT/AM2008/000003
Authority: WO
Inventors: Karen Gasparyan; Patvakan Hakhinyan
Original assignee: Karen Gasparyan; Patvakan Hakhinyan
Priority date: 2007-02-22
Filing date: 2008-02-13
Publication date: 2008-08-28

Abstract

The invention is related to hand-operated locking pliers that enable locking of the jaws (5, 14) during clamping. The locking pliers comprise an elongated frame (1), one end of which forms a stationary handle (2), a jointed operating lever (3) one end of which forms a moveable handle (4), two jaws (5, 14), a grip-and-release mechanism, a locking mechanism and an adjustment mechanism for the resting point (10) of the frame (1). The grip-and-release mechanism is implemented as a four-bar linkage mechanism, one of the links of which is the first jaw (5). The second jaw (14) is kinematicly connected to the first jaw (5). Said kinematic connection can be implemented via toothing, a four-bar linkage, rocker or other mechanism. There are scale divisions (28) on the side of the frame (1) and a mark on the jaw for initial adjustment of the jaws (5, 14) opening.

Description

LOCKING PLIERS

Technical Field

The present invention is related to hand-operated locking pliers that enable locking of the jaws while clamping a workpiece and can be widely used for various clamping applications. Background Art

Locking pliers are known in the prior art comprising an elongated frame, one end of which forms a stationary handle, a jointed operating lever, one end of which forms a moveable handle, two jaws, a grip-and-release mechanism and an adjustment mechanism for the resting point of the frame. One jaw is fixed to the frame while the other jaw is moveably mounted on the frame by means of the first pivot. The moveable jaw is jointed to the operating lever by means of the second pivot and therefore a turn of the moveable handle brings about a turn of the moveable jaw (disclosed in US 5,351,585, B25B7/12, 1994).

A number of locking pliers with a similar kinematic scheme are also known in the prior art, wherein one jaw is fixed to the frame while the other jaw is jointed to the moveable handle (US 4,541,312, US 4,546,680, US 4,709,601, US 4,730,524).

A disadvantage of all known locking pliers is that an unintentional change in the position of a clamped workpiece is likely to occur while closing the moveable jaw which can damage the surface of the clamped workpiece or affect its positioning relative to other workpieces. The reason for said disadvantage is that one of the jaws is stationary and the moveable jaw turns about it.

To eliminate said disadvantage, the user has to move his hand in an oncoming direction which is considered an inconvenience of use. The referred above locking pliers (US 5,351,585) solve this problem by designing the working surfaces of the jaws as complex profiles for workpieces with a round cross section which, however, offers no solution to the problem of the maintaining the position of a clamped workpiece. Moreover, the adjustment of the resting point of the frame takes place after positioning a workpiece between the jaws which not only affects the centering of the clamped workpiece, but also causes considerable inconvenience to the user.

The initial adjustment of the resting point can be only approximate and finalized after 2 or more trials which is rather ineffective.

The closest analogue to the present invention is locking pliers comprising an elongated frame, one end of which forms a stationary handle, a jointed operating lever, one end of which forms a moveable handle, two jaws, a grip-and-release mechanism and a frame resting point adjustment mechanism, wherein one jaw is supported on the frame via the first pivot and is jointed to the front end of the operating lever via the second pivot, while the other jaw is fixed to the frame (disclosed in US 6 227 080, B25B7/12, 2001).

These locking pliers also have all the disadvantages discussed above. Disclosure of Invention It is the object of the present invention to maintain the positioning of a clamped workpiece during clamping and advance convenience of use.

The present invention solves the problem of maintaining of the positioning of a clamped workpiece by implementing both jaws as moveable, kinematicly connected to each other and having the same degree of kinematic freedom. Structure and the essence of the present invention is locking pliers comprising an elongated frame, one end of which forms a stationary handle, a jointed operating lever, one end of which forms a moveable handle, two jaws, a grip-and-release mechanism, a locking mechanism, and an adjustment mechanism for the resting point of the frame, in which one jaw is mounted on the frame via a first pivot and jointed to the front end of the operating lever via a second pivot, the grip-and-release mechanism is comprised of an operating lever and a link, the toothed end of which is pivoted to the center of the operating lever, while the other end is pivoted to the resting point of the frame, the link, the frame, the first jaw and the operating lever form a four-bar linkage mechanism, one of the moveable bars of which is spring-loaded, the locking mechanism comprises a button jointed to operating lever so as the button tooth can engage with the link tooth and one end of the button forms a trigger that is positioned within reach of the user's forefinger and can be pushed, the adjustment mechanism for the resting point of the frame comprises a support nut and a adjusting bolt positioned in said nut along the stationary handle, characterized by that the second jaw is jointed to the frame and kinematicly connected to the first jaw. The second feature of the present invention is that the kinematic connection between the jaws is implemented via gearing, a four-bar linkage mechanism, a rocker or any other mechanism that provides counter motion of the jaws during the grip and release operation.

The third feature of the present invention is that there are scale divisions on the side of the frame and a mark on either jaw, and the scale has end markings for indicating the opening extremes of the jaws.

The fourth feature of the present invention is that the button comprises a safety lock that is positioned on the moveable handle and can engage with the trigger of said button.

The annexed drawings, which are incorporated in and form part of the specifications, illustrate the preferred embodiments of the present invention, and together with the descriptions serve to explain the structure, operation and essence of the invention. Fig. 1 schematically shows the present invention with open jaws;

Fig. 2 schematically shows the present invention with closed jaws;

Fig. 3 schematically shows the preferred embodiment of the present invention comprising a four-bar linkage mechanism to connect the jaws; Fig. 4 schematically shows the preferred embodiment of the present invention comprising a rocker mechanism to connect the jaws;

Fig. 5 shows a general view of the present invention, including scale divisions and the mark.

The preferred embodiment of the present invention comprises the elongated frame (1), one end of which forms the stationary handle (2) and the operating lever (3), one end of which forms the moveable handle (4) and two jaws. The first jaw (5) is mounted on the frame (1) by means of a pivot (6) and jointed to the far end of the operating lever (3) by means of a pivot (7). One end of the link (8) is jointed to the center of the operating lever (3) by means of a pivot (9), while the other end is jointed to the frame (1) at the resting point (10) of the frame (1). The adjustment mechanism of the resting point (10) of the frame (1) comprises the support nut (11) fixed to the stationary handle (2) and the adjusting bolt (12) positioned in the support nut (1 1) along the stationary handle (2).

The grip-and-release mechanism comprises the operating lever (3) and the link (8). The spaces between the link (8), the resting point (10) and the pivot (6), between the pivots (6) and (7) of the jaw (5) and between the pivots (7) and (9) of the operating lever (3) form a four-bar linkage mechanism, one of the moveable joints of which is spring-loaded. Figs. 1 and 2 show a spring (13) as a means for spring-loading the pivot (7); said spring can be also positioned between the pivot (9) and the frame (1).

The second jaw (14) is mounted on the frame (1) by means of a pivot (15) and kinematicly connected to the first jaw (5). The kinematic connection is chosen so that to provide counter motion of the jaws while gripping or releasing. Thus both jaws are moveable and have the same degree of kinematic freedom.

Figs. 1 and 2 show the preferred embodiment of the present invention comprising gearing as the kinematic connection between the jaws. The preferred gearing ratio is minus 1 and preferred module of the teeth is l,5-3mm.

The kinematic connection between the jaws can be implemented by means of other mechanisms which meet aforementioned criteria.

Fig. 3 shows the preferred embodiment of the present invention comprising a four-bar linkage mechanism to connect the jaws kinematicly; wherein the lines joining the central points of the pivots (6) and (15), of the pivot (6) and the pivot (17) of the joint lever (16), of the pivots (17) and (18) of the joint lever (16), and of the pivot (18) of the joint lever (16) and the pivot (15) form antiparallel link mechanism in which the gearing ratio is minus 1.

Fig. 4 shows the preferred embodiment of the present invention comprising a rocker mechanism to connect the jaws kinematicly; wherein one of the jaws has a protrusion (19) and the other has a hollow (20). The preferred embodiment of the present invention illustrated in Fig.

4 has the protrusion (19) on the first jaw (5) and the hollow (20) in the second jaw (14), however the counter positioning of the protrusion and the hollow is also possible.

The locking mechanism comprises a button (21) that is positioned on the operating lever

(3) by means of a pivot (22). The button tooth (23) is positioned so that it can engage with the tooth of the link (8). The engagement takes place when the pliers lock, as shown in Fig. 2. The link (8) also comprises a limiting tooth (25) which can engage with the button tooth (23) when the jaws are open, as shown in Fig. 1 , and serves to limit the opening between the handles (2) and (4).

The other end of the button (21) is implemented as a trigger (26) which is positioned within the reach of the user's forefinger. A safety lock (27) is positioned on the moveable handle

(4) to engage with the trigger (26) and serves to prevent an unintentional release of the jaws (5) and (14).

The present invention comprises a means for initial adjustment of the opening between the jaws (5) and (14) which is designed as scale divisions (28) on the frame (1) and a mark (29) made on either jaw (5) and (14). In the embodiment shown in Fig. 5 the mark (29) is on the jaw (14), however it can be placed on the jaw (5) with equal ease. The end markings on the scale correspond to the opening extremes of the jaws (5) and (14).

The levers (2) and (4) can comprise moveable handles (30) to advance convenience of use, as shown in Fig. 5. The operation of the present invention is discussed below.

To lock a piece it is put between the jaws (5) and (14) and force levers (2) and (4) to close. As a consequence, positioning of the pivots (6), (7), (9) and (10) comprising the four-bar linkage mechanism is changed and the jaw (5) turns about the pivot (6). Fig. 1 shows counter-clockwise turn of the jaw (5). Meanwhile, the jaw (14) turns about the pivot (15) in the opposite direction due to the kinematic connection between the jaws (5) and (14). The shift of the pivots (6), (7), (9) and (10) of the four-bar linkage mechanism results in that the button tooth (23) slides over the tooth (24) of the link (8) and engages with it. In such a position (shown in Fig. 2) the angle formed by the pivots (7), (9) and (10) is about 178 degrees which provides big clamping force. The user then utilizes the safety lock (27) which fixes the button (21) and prevents an unintentional interruption of the clamping operation. To release the workpiece, the user pushes the button (21) which turns about the pivot (22) and disengages the teeth (23) and (24). Said four-bar linkage mechanism resumes its initial arrangement under the influence of the spring (13). The handles (5) and (14) stop moving apart the moment the limiting tooth (25) engages with the button tooth (23), as shown in Fig. 1. The initial size of the opening between the jaws (5) and (14) is conditioned by the position of the resting point (10) which is adjusted by turning the handle (31) of the bolt (12).

The user turns the handle (31) until the mark (29) reaches the scale division (28) fitting the dimensions of a workpiece to be clamped. It minimizes the threat of the position shift during the clamping and reduces the number of unsuccessful attempts, which consequently advances convenience of use.

Claims

1. Locking pliers comprising an elongated frame, one end of which forms a stationary handle, a jointed operating lever, one end of which forms a moveable handle, two jaws, a grip-and-release mechanism, a locking mechanism, and an adjustment mechanism for the resting point of the frame, in which one jaw is mounted on the frame via a first pivot and connected to the front end of the operating lever via a second pivot, the grip-and- release mechanism is comprised of an operating lever and a link, the toothed end of which is pivoted to the center of the operating lever, while the other end is pivoted to the resting point of the frame, the link, the frame, the first jaw and the operating lever form a four-bar linkage mechanism, one of the moveable bars of which is spring-loaded, the locking mechanism comprises a button jointed to operating lever so as the button tooth can engage with the link tooth and one end of the button forms a trigger that is positioned within reach of the user's forefinger and can be pushed, the adjustment mechanism for the resting point of the frame comprises a support nut and a adjusting bolt positioned in said nut along the stationary handle, characterized by that the second jaw is jointed to the frame and kinematicly connected to the first jaw, there are scale divisions on the side of the frame having end markings for indicating the opening extremes of the jaws.

2. Locking pliers according to claim 1, characterized by that the kinematic connection between the jaws is implemented as gearing.

3. Locking pliers according to claim 2, characterized by that the gearing ratio is minus 1.

4. Locking pliers according to claim 1, characterized by that the kinematic connection between the jaws is implemented as a four-bar linkage mechanism.

5. Locking pliers according to claim 4, characterized by that the four-bar linkage mechanism is implemented as an antiparallel link mechanism.

6. Locking pliers according to claim 5, characterized by that the transmission ratio in the antiparallel link mechanism is minus 1.

7. Locking pliers according to claim 1, characterized by that the kinematic connection between the jaws is implemented as a rocker mechanism.

8. Locking pliers according to claim 1, characterized by that they comprise a safety lock positioned on the moveable handle so that to engage with the trigger of the button.