NZ200338A

NZ200338A - Impact wrench

Info

Publication number: NZ200338A
Application number: NZ200338A
Authority: NZ
Inventors: D A Mcdonald
Original assignee: Farrow Investments Pty Ltd
Priority date: 1981-04-29
Filing date: 1982-04-19
Publication date: 1984-12-14
Also published as: DE3215848A1; NL8201687A; SE8202651L; IT8248293A0; FR2504839B1; GB2097309A; ZA822725B; FR2504839A1; AR227720A1; BE892980A; GB2097309B; IT1147933B; JPS584365A

Description

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NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION PATENT n:- \ 19 APR 19£2 "IMPACT TOOL" I/We-, DOUGLAS ARTHUR MCDONALD, of 15 Sefton Road, Thornleigh, New South Wales, Australia, an Australian Citizen, SUBSTITUTION OF APPLICANT - UNCEB SECTION 24 rQV VO p^-ut-d hereby declare the invention for which I / we pray that a patent may be granted to jne/ns-, and the method by which it is to be performed, to be particularly described in and by the following statement:- 200338 The present invention relates to hand tools and in particular to a tool which enables the user to apply impact torque, for example, to loosen an automotive wheel nut. The invention has been developed for use as an impact wrench and will be described hereinafter with reference to this field of use. It will be appreciated, however, that the invention is not limited to this particular application.

It is frequently found that standard sized wrenches do not provide sufficient leverage to loosen stubbon nuts, bolts or large screws. This is particularly the case with automotive road tools which are often inadequately sized for reasons of space and cost. To provide increased torque, the user may resort to attaching make-shift extension levers or striking the wrench with a hammer. This is always awkward and usually damages both the tool and the bolt-head, nut or screw.

It is an object of the present invention to provide an impact tool which can be used to apply an impact torque to whatever operative tool is connected to it.

According to the invention there is provided an impact tool for applying impact torque comprising a shaft defining an axis, a' transversely extending striker bar mounted for rotation about said axis, at least one anvil member connected with said shaft and spaced from said axis in the path of said striker bar, said at least one anvil ember extending between a pair of spaced parallel plates in the form f circular discs extending normally with respect to said axis.

Preferably, the striker bar is mounted for rotation about the shaft so that its axis and the central axis are identical. The shaft is also preferably adapted for ^ "7 'T ■ I'.-J KJ y*J connection to a wrench socket head fitting, thereby making the device generally applicable to a wide range of operative tools.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of an impact tool according to the invention; Figure 2 is a side elevation of the tool shown in figure 1; Figure 3 is a sectional plan view taken on line 3-3 of figure 2; Figure 4 is a sectional side elevation taken on line 4-4 of figure 1; Figure 5 is a sectional view taken on line 5-5 of figure 1; Figure 6 is a fragmentary view showing the application of the tool to a wrench socket for loosening a nut; Figure 7 is a fragmentary sectional plan view illustrating the operation of the tool.

Referring to the drawings, the impact tool 1 includes a shaft 2 defining a central axis 3. A transversely extending striker bar 4 is mounted for rotation about the shaft 2 between a pair of parallel disc plates 5 spaced along the shaft and securely joined to it by welding or other suitable means.

As best shown in figures 3 and 5, the discs 5 support a pair of anvil members in the form of pins 6 extending between 20033 the discs and diametrically oppositely spaced with respect to the central axis 3. The pins 6 are spaced from the central axis 3 so as to lie in the path of the striker bar 4 as it rotates about the shaft 2 within the limits defined by the pins. One of these pins 6 may be omitted if desired. The striker bar 4 is substantially in balance about the axis 3 and includes a pair of cylindrical weights 7 at or adjacent its opposite ends for increasing its moment of inertia about the shaft. These weights 7 may also serve as handles when 10 using the tool.

One end of the shaft is provided with a square sectioned key 9 to adapt it for engagement with a wrench socket 10 as shown in figure 6. The device is thereby generally applicable to a wide range of operative tools. If required, the shaft may be fixedly connected to a specific tool, such as an automotive wheel nut socket, when this versatility is not required. A wedging tool 11 is also provided at one end of the striker bar for removing automotive hub caps. Rubber caps 12 may also be applied to the free ends 13 and 14 of the 20 shaft and striker bar respectively.

In operation as an impact wrench to loosen, for example, an over-tightened nut, a socket 10 is attached to the shaft key 9 and the tool is applied to the nut 15, as shown in figure 6. The weights 7 may then be gripped as handles and the striker bar rotated, thereby simultaneously striking the two pins 6 as shown in figure 7 and delivering a substantial impact torque to loosen the nut. Alternatively, with the tool in the operative position applied to the nut, the free 7 ^^7 ■? o ^ 'O O O end 13 of the shaft remote from the nut may be held lightly with one hand and the striker bar given a brisk rotational movement with the other hand. The rotational inertia of the striker bar will often be found sufficient to loosen a nut in this way, without additional torque being applied by the user.

In other embodiments, the striker bar may be of uniform section throughout its length. Preferably, the bar is as heavy as conveniently possible in order to provide a high moment of inertia. These embodiments may also employ a 10 single anvil member rather than the two members illustrated in the drawings. In one particular embodiment, for example, the shaft may be provided with one or more projecting lugs which serve as anvil members. The lug or lugs may be defined by a pin extending through the shaft. The corresponding striker bar may then include a pair of spaced fork arms journalled on the shaft on either side of the lugs. The bar may then extend only on one side of the shaft, or it may be joined to another forked bar to define a balanced bar extending substantially equally in both directions. In this 20 latter case, the two components may each include a part journal and be joined one on top of the other, thereby forming the composite bar and bearing simultaneously.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

200338 A '< b - WHAT 1 CLAIM IS:

1. An impact tool for applying impact torque comprising a shaft defining an axis, a transversely extending striker bar mounted for rotation about said axis, at least one anvil member connected with said shaft and spaced from said axis in the path of said striker bar, said at least one anvil member extending between a pair of spaced parallel plates in the form of circular discs extending normally with respect to said axis.

2. An impact tool according to claim 1 wherein said discs are concentric with said axis.

3. An impact tool according to claim 2 wherein said shaft extends through both said plates.

4. An impact tool according to claim 1 including two said anvil members diametrically oppositely spaced with respect to said axis.

5. An impact tool according to claim 1 wherein said striker bar is substantially in balance relative to said axis and includes a pair of weights at or adjacent its opposite ends for increasing its moment of inertia about said axis.

6. An impact tool according to claim 5 wherein said weights are cylindrical in form.

7. An impact tool according to claim 1 wherein said striker bar is of uniform section throughout its length.

8. An impact tool according, to claim 1 wherein a distal end of said shaft is adapted for engagement with a wrench socket. 200338 7

9. An impact tool according to claim 1 wherein a distal end of said shaft is integral with a wrench socket.

10. An impact tool according to claim 1 wherein a distal end of said striker bar includes a wedging tool. j-vred this U*fL day of A. J. PARK SON PER agents for the applicants 18 JUU985