SELF-TIGHTENING WRENCH

Abstract: A pipe wrench/ wrench consisting of a shank with an involute jaw and a loose jaw pivotally connected hereto which can be plane or consist of planes forming angles to each other. The jaws can be toothed. The centre of the circle belonging to the involute lies on or close to the axis of rotation. During the relative rotation of the jaws, the point of the involute (relative to the loose jaw) which touches pipes of a diameter corresponding to the jaw gap will always lie on the same straight or almost straight line as intersects the involute at right angles, and it is possible to use either the concave or the convex side of the involute as jaw face. Pipes which are actuated will, at intervals of approx. 120`, receive a chiefly radially directed normal force K which is proportional to the moment actuating the pipe, irrespective of the pipe diameter.

Description: S elf- ightening wxench The invention relates to a pipe wrench . Self-tightening tongs " and wrenches consisting of two linked parts , one of which has a shank and handle , have been known for many years . Most frequently, these wrenches are designed so that the shank - part has a jaw which - when viewed from the side - is limited by a circle or a curve with a variable curva¬ ture , while the jaw face of the other part can be plane or con¬ sist of pl anes forming angles to each other ; for example , so . that the jaw fits hexagon nuts . Wrenches most often bear the stamp of the curved jaw limit of the shank part being a com¬ promise which does not hold equally well on to all nut sizes ' or pipe diameters withi ' n the ranges accomodatβi by the wrenches . The curvature of some wrenches has been designed by determina¬ tion of a few usable points through which the curves have been drawn . The pipe wrench according to the invention is characterized in that the centre in th-e shank part for the relative rotation of the parts is also the centre of a circle , the involute of which forms the exact limit of the jaw of the shank part . A study of line 1 of the side view ( a delineation of a plane at right angles to the axis of rotation ) , which line is normal to the jaw face of the other loose jaw part or is an angle bi¬ sector relative to two of the jaw faces of the part, shows that because of the involute all the pipes of the diameters accomodated by the wrench contact the involute exactly where it is inter¬ sected by line 1 when the centre of rotation of the loose jaw part is at a distance from 1 which is radius of the circle be¬ longing to the involute . In order to allow for hexagonal parts , the point of contact can be moved a small distance Δ r tangentially in the direction of rotation by the centre of rotation of the loose jaw part being moved the distance Δ r closer to 1 when 1 is angle bisector relative to two jaw faces forming an angle of 60° to each other in the loose jaw part . OMPI The wrenc h works in the way that pipes or parts inserted be¬ tween its jaws are " firmly fixed between these when the handle is pulled , and they are at the same time actuated by a moment. The normal force between pipe and jaw is determined by the moment of the shank and the moment arm r which is the same for all pipe diameters as a result of the inv olute design . The effect is that no matter the diameter of the pipe actuated there will always be a proportionality between the moment acting on the pipe and the normal force . Since the force K between the involute jaw and the pipe relative to the loose jaw will always act along the same line 1, or a line parallel with 1 , it. is most expedient that the loose jaw shall be ' V-shaped with 60° between the sides to which 1 is the angle bisector since the actuated pipe will then receive the normal force K at three points at 120° intervals which partly reduces the risk of flattening and partly permits transmission of a moment which is 50 p . c . higher as compared to a design where the normal force K acts at two points on the pipe at in¬ tervals of 180° . Because of this 60° V-shaped loose jaw the wrench will also be suitable for hexagonal parts , " and as mentioned in the foregoing the point of contact and hence the line of application of the force K can be moved a .distance Δr tangentially in the direction of rotation which , when Δ r is small , does not change the fact to any considerable degree that parts are actuated at three points at 120° intervals since, in actual practice , these "points" are faces of a size of a few millimetres . According to known . principles , the wrench can be provided with adjustment facilities since a possible shifting in the direction of line 1 on the loose jaw of its axis of rotation will extend the diameter range covered by the wrench . The drawing shows a wrench according to the invention since Fig . 1 shows the wrench seen from one side and gripping a heavy pipe ,, and OMPI Fig. 2 shows the wrench seen from one side and gripping a thin pipe, a ' nd Fig. 3 shows the wrench in perspective. The wrench consists of a shank with an involute, possibly a toothed, jaw a and a loose jaw b pivotally connected hereto. Fig. 1 shows the radius r of the circle c belonging to the in¬ volute as well as r, 1, and K mentioned in the foregoing. Fig. 4 shows a design where the concave side of the involute is utilized as a jaw curve for the shank. OM?I . WIPO " ~

Claims: C L A I M S A pipe wrench/wrench consisting of a shank with a curved jaw and a -jaw pivotally connected to the shank, characterized in that the curved jaw of the shank has the shape of an involute , possibly with teeth, the centre of the circle belonging to this involute lying on or close to the axis of rotation of the pivot¬ ally connected jaw, the active face of this jaw being plane oir V-shaped and facing the side of the involute utilized as jaw on the shank which can be either the concave or the convex side of the involute. O PI

Inventors: LARSEN E
Applicants: LARSEN E
Application year: 1980
Main classification: B25B13
IPC codes: B25B13