US3057063A - Hand tools - Google Patents

Description

Oct. 9, 1962 R. GRIFFITHS ET AL 3,057,063

HAND TOOLS Filed March 1, 1961 2 Sheets-Sheet l INVENTdRS ,Qypgpr /FF/TA/J L/H/v $55107 Q0/1040 ATTORNEY Oct. 9, 1962 R. GRIFFITHS ETAL HAND TOOLS 2 Sheets-Sheet 2 Filed March 1, 1961 ToD E! 0 ./T M5 W i% ZY rnm m w 6 G. H

" tent ,7 3,057,053 Patented Oct. 9, 1962 flee 3,057,063 HAND TOOLS Rupert Griiliths, London, and John Albert Radford, Ashford, England, assignors of one-half to Wilkinson Sword Limited, London, England, a British company, and one-half to Harry Beckharn Randolph, London, England Filed Mar. 1, 1961, Ser. No. 92,551 Claims priority, application Great Britain Mar. 1, 1960 7 Claims. (Cl. 30-266) This invention relates to hand tools of the kind in which two co-operating members are moved together and apart by handles which are coupled to the respective co-operating members. While of broad application, the invention is particularly applicable to cutting or shearing tools such as scissors, pruners, or secateurs, garden shears, metal cutters, etc.

According to the present invention there is provided a hand tool of the kind comprising two co-operating members which are moved together and apart by handles wherein the two co-operating members are coupled by engagement of surfaces which are inclined at van acute angle to the planes in which the co-operating members move together and apart, the arrangement being such that the reaction of work being operated on by the co-operating members causes relative movement of the inclined surfaces in a direction normal to said planes.

The invention also provides a hand tool of the kind comprising two co-operating members which are movable about bearing surfaces of a connecting pivot under the control of associated handles for effecting cutting, wherein for opposing separation of said co-operating members in a direction parallel to the pivotal axis said bearing surfaces are inclined at an acute angle to the pivotal axis, whereby a reactive force resulting from cutting tends to produce relative movement of said bearing surfaces in a direction which produces movement of said co-operating members towards one another in a direction parallel to the pivotal axis.

There is further provided by the invention a hand tool of the kind comprising two co-operating members which are movable about a connecting pivot under the control of associated handles, the pivot being so constructed that the reactive force resulting from said co-operating members operating upon a work piece tends to produce a movement of said co-operating members relative to said pivot which opposes separation of said co-operating members in a direction parallel to the pivotal axis.

The invention still further provides a hand tool of the kind comprising two co-operating members which are movable about a connecting pivot under the control of associated handles, the pivot being arranged to permit a restricted amount of relative translational movement between the members and having co-operating surfaces inclined to a plane normal to the pivot axis such that, when a workpiece is operated upon between said cooperating members, said surfaces tend to slide relative to one another in a sense to move the members closer together in a direction parallel to the pivotal axis.

One construction of hand tool in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

FIGURE 1 is a front elevation of the tool in the open position;

FIGURE 2 is a side elevation of the tool in the closed position;

FIGURES 3 and 4 are front views of the upper portion of the two parts of the tool respectively, shown separated from one another;

FIGURE 5 is a sectional side view of the pivot portion of the tool with the two parts shown separated from one another;

FIGURE 6 is an end view of the pivot spring; and

FIGURE 7 is a section taken along the line VII-VII in FIGURE 2.

The hand tool to be described is designed for use as an all-purpose shear, that is a tool having many uses, for example for household purposes for cutting a variety of different materials such as paper, textiles, string, wire and so on.

The shear comprises a pair of members 10, 11 each having a handle portion 10a, 11a and a shear blade 10b, Mb. The handle portions 10a, 11a are substantially straight and can be clasped in the palm of the hand to give simple and comfortable hand loading in contrast to the method of loading conventional scissors which involves a finger, thumb and palm of the hand. The blades 18b, 11b are substantially flat and of a hard metal and are secured to backing portions formed integral with the handles 10a, 11a which may be of alight material, such as aluminium alloy. The backing of the blades 10b, 11b assists in avoiding flexing apart of the blades 16b, 11b under load. The two members 10, 11 being pivotally coupled together at a suitable intermediate position so that the shear blades 10b, 11b may be opened and closed by corresponding movement of the handle portions 10a, 11a in normal manner.

In place of a conventional pivot bolt, the members 10, 11 are coupled by a bolt 12 (FIGURES 3 and 5) secured to the shear blade 11b by a shank 12a which passes through a hole 11b1 in the shear blade 11b and is secured by a nut 13 accommodated in an aperture 110 in the member 11. The head of the bolt 12 has an undersurface 12b, which forms part of a truncated cone. When the shear is assembled the head of the bolt 12 lies in the space bounded by the mouth 1001 of an opening in the blade 10b and a recess 10a in the member 10 with the undersurface 12b adjacent a corresponding truncated conical bearing surface formed in the shear blade 16b. The portion 12a1 of the shank 12 immediately adjacent the conical surface 12b is of smaller diameter than the month 1001 of the bearing surface 100 so that there is a small clearance therebetween. The axial length of the shank portion 12a1 is such that with the shear assembled and the blades 1%, 11b pressed together there is a small clearance between the bolt undersurface 12b and the bearing surface 10c when the longitudinal axis of the bolt 12 is coaxial with the bearing surface 100.

When the shear is in use and the action of cutting produces a reactive force tending to separate the two blades, the reactive force causes relative movement between the longitudinal axis of the bolt 12 and the longitudinal axis of the surface 10c. This results in relative movement between the two surfaces 12b and 100 such that the bolt undersurface 12b rides up the bearing surface liic thereby drawing the adjacent surfaces of th two blades 10b, 11b closer together. When the shear blades 10b, 11b are opened and closed without any material between them, the two blades 16b, 1112, move freely relative to one another due to the clearanc referred to above between the shank portion 12x11 and the mouth 1001. However, when a reactive force is produced between the two blades due to the resistance of a material being cut, and which would normally tend to cause separation of the blades 16b, 1111, the aforesaid movement of the bolt 12 relative to its co-operating bearing surface 10c draws the two blades 1%, 11b together thereby opposing separation. In this way the pivot arrangement 12b, 10c, wedges the blades 10b, 11b together in proportion to the load being cut and returns to a free fit on release of the load at the end of the cutting stroke, so that only a light spring is needed for opening the blades. Furthermore, the blades can be substantially flat and need not be set (that is twisted from the flat) as is necessary with conventional scissors so that a light return spring is suflicient to open the blades at the end of the cutting stroke.

It will be understood that although reference has been made to the use of co-operating truncated conical surfaces, the abutting surfaces may hav other shapes provided the displacement of the longitudinal axis of the bolt 12 relative to the longitudinal axis of the bearing surface 190 serves to draw the two blades 10b, 11b together; for example, one surface may be a cap of a sphere.

A further feature of the invention is that, to facilitate cleaning, the bolt 12 and the bearing surface 10c may be shaped in plan view as shown in FIGURES 3 and 4 so so that the two members 10, 11 key together over the normal range of cutting movement, but by moving the handles 10a, 11a further apart the fish-tail portions of the bolt 12 can be withdrawn through the keyhole-like apertures 1002 to eparate the members 19 and 11 for cleaning or to permit either member to be used individually as a knife. Of course, such interlocking over the operative range of movement could be provided by other suitable constructions. A catch 15 is provided for securing the blades 10b, 11b in the closed position when the tool is not in use.

A spring may be provided normally drawing the two members together along the axis of the pivot and also serving as an opening spring which urges the two handles apart in a direction perpendicular to the axis of the pivot. However, for certain uses of such hand tools, for example in the case of all-purpose shears required to cut relatively soft or thin material which produces only a small reaction to the cutting, it is advantageous to employ a spring which pre-loads the shear to cause the bolt surface 12b to rise up the bearing surface 10c, thereby holding the two shear blades 10b, 11b suflictiently close together readily to cut materials of the aforesaid kind.

If a conventional torque spring is used for urging the two handles 10a, 11a apart, each end of the spring which extends tangentially outwards will exert a single force on the respective blade 10b, 1112. This force will be converted by the conical pivot arrangement 10c, 12b into a large force pulling the two blades 1%, 11b together along the axis of the bolt 12. This will increase the friction between the blades ltlb, 11b which may be so great as to prevent the opening action of the spring. T o overcome this difficulty it is proposed to fold back one or both ends of the spring approximately along a diameter of the spring in such a way that the torque is applied to each blade 1%, 1112 by two approximately equal and opposite forces which leave little unbalanced load to be reacted by the conical pivot arrangement 10c, 11]). As explained above, a small degree of reaction on the conical pivot arrangement 10c, 11b is advantageous so as to pull the blades ltl b, 11b sufficiently close together for cutting relatively soft or thin material. One form of torsion spring satisfactory for this purpose is shown in FIGURES 4, 5 and 6. It will be seen that this spring 14 has a short tail 14a and a longer tail 1417 which is extended outwardly and then doubled back across the axis of the spring 14.

The spring 14 fits in a recess d in the member 10 and the short tail 14a is held in a narrow groove ltldl (FIGURE 4) which leads off from the recess 10d. When the two members 10 and 11 are assembled and the handles 10a, 11a moved towards one another, the free end of the long tail 14b contacts a pin 12c upstanding from the head of the bolt 12 whilst the opposite looped end of the long tail 14b bears against a lug 12d upstanding on the diametrically opposite side of the head 12. The position at which the pin 12c and the lug 12d engage the respective portions of the long tail 14b are at different radial distances from the axis of the spring 14 and the amount of sideways loading imparted by the spring is dependent upon this radial difference.

The desired reactive force produced when cutting may be accentuated by forming one or both of the edges of the blade 10b, 1111 with a rake, fo example at an angle of thirty degrees as shown in FIGURE 7 because the direction of reaction to cutting is then correct for producing the desired relative movement between the two shear members. As cutting proceeds and leverage is reduced the tendency for the material being cut to slip between the blades may tend to overcome the corrective action of the pivot. The aforesaid rake of the cutting edge reduces this tendency.

Considerable rake also makes for easier entry into the material being cut. However, the load on the blade near the pivot may be such that rake unduly weakens the cutting edg itself. A useful solution is therefore to vary the rake along the length of one or both blades 10b, 11b, either as a continuous variation or as a stepped variation. Moreover, the abutting surfaces of the cutting or shearing members are preferably slightly concave.

It will be understood that although the invention has been described in its application to all-purpose shears it is clearly applicable to a wide range of hand tools of the kind referred to.

We claim:

1. In a hand tool of the kind comprising two co-operating members which are moved together and apart by handles, mean-s coupling the two co-operating members, said coupling means having a first bearing surface fixed rigidly to one of said co-operating members and a second bearing surface fixed rigidly to the other of said cooperating members, said first and second bearing surfaces each being inclined at an acute angle to the planes in which the co-operating members move together and apart, said bearing surfaces having a limited freedom of movement relative to one another in a direction parallel to said planes, said limited movement being produced by the reaction of work being operated on by the co-operating members and drawing said planes closer together.

2. A hand tool according to claim 1, wherein said coupling means comprises a head having an undersurface in the shape of a part of a truncated cone, said undersurface constituting one of said bearing surfaces, said head being secured to one co-operating member, said other co-operating member having an aperture in which said head is accommodated with said undersurface lying adjacent a like-shaped surface, said like-shaped surface constituting the other of said bearing surfaces.

3. A hand tool according to claim 2, wherein said aperture has a mouth, said head and the mouth of said aperture being shaped in plan view so that in one position of opening of said handles the head can be withdrawn through the mouth to separate the two cooperating members with their handles attached thereto.

4. A hand tool of the kind comprising two co-operating members, two handles, each handle being united to a respective one of said co-operating members, a connecting pivot, said connecting pivot having first and second bearing surfaces, said first bearing surface being rigidly fixed relative to one of said co-operating mem bers and said second bearing surface being rigidly fixed relative to the other of said co-operating members, said first and second bearing surfaces each being inclined at an acute angle to the axis of rotation of said pivot, said cooperating members having a limited freedom of movement relative to one another in a direction at right angles to the pivot, whereby a reactive force resulting from cutting tends to produce relative movement of said bearing surfaces in a direction which produces movement of said cooperating members towards one another in a direction parallel to the pivotal axis.

5. A hand tool of the kind comprising two cutting members, two handles, each handle being secured to a respective one of said cutting members, a connecting pivot, said cutting members being movable about said connecting pivot under the control of said handles, said connecting pivot having first and second bearing surfaces,

said first bearing surface being rigidly fixed relative to one of said cutting members and said second bearing surface being rigidly fixed relative to the other of said cutting members, said first and second bearing surfaces each being inclined at an acute angle to the axis of rotation of said pivot, said cutting members having a limited freedom of movement relative to one another in a direction at right angles to the pivot, whereby when an article is being cut by said cutting members said first and second bearing surfaces tend to slide relative to one another in a direction which produces movement of said cutting members towards one another in a direction parallel to the pivotal axis.

6. A hand tool according to claim 5, further comprising a torque spring said spring having a first end which bears against one co-operating member and a second end which bears against the other cooperating member for urging the cutting members toward the open position, said first spring end bearing against the one co-operating member at a first predetermined position and said second spring end bearing against the other co-operating member at two positions which are angularly spaced relative to said pivot axis and on opposite sides of said predetermined position, whereby the torque of said spring is applied to each co-operating member by respective forces which are approximately equal and opposite.

7. A hand tool according to claim 6, further comprising a coil spring, said spring being adapted to urge said cutting members towards the open position, said coil spring having at least one end folded back approximately along a diameter of the coil so that said one end extends outwardly from diametrically opposite sides of the coil and is engaged on both sides of the coil by the cutting member to which torque is to be applied.

References Cited in the file of this patent UNITED STATES PATENTS 556,440 Sheer-er Mar. 17, 1896 624,175 Chapman May 2, 1899 743,658 Polkowski Nov. 10, 1903 1,007,836 Allison Nov. 7, 1911 1,423,866 Miller July 25, 1922 1,660,286 Wilkes et a1 Feb. 21, 1928 1,814,821 Botts July 14, 1931 1,886,273 Thomson Nov. 1, 1932 2,392,118 Cacarillo Jan. 1, 1946 2,596,767 Erickson May 13, 1952 2,801,468 Anderson Aug. 6, 1957 FOREIGN PATENTS 428,590 Great Britain May 15, 1935

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