This invention relates to impact hand tools that are spring driven. Background Art

The concept of providing impact hand tools that are spring driven have been suggested for many years. For example US Patent No. 833,712 granted to H. Geisenhoner on October 16, 1906 show a prick punch hand tool that is spring driven. However such hand tool is rather expensive to manufacture and assemble. Numerous other patents show even more complicated and costly hand tools that are likely to wear out prematurely through repeated use, particularly when used in corrosive, dirty and dusty atmospheres.

Also separate tools are required for each function, necessitating multiple tools. One of the objectives and advantages of this invention is to provide a spring driven impact hand tool with multiple tool members for performing different functions that is inexpensive to manufacture and unlikely to wear out, even when used in corrosive, dirty or dusty atmospheres.

These and other advantages of this invention will become apparent upon reading the following detailed description of preferred embodiments.

Brief Description of the Drawings

Preferred embodiments of the invention are described below with reference to the accompanying drawings, which are briefly described below. Fig. 1 is a side elevation view of a preferred embodiment of the impact hand tool with the tool shown in an upright orientation on a work surface with a center punch tool member at one end engaging the work surface and a nail setting tool member at the other end, and with a tension driving coil spring in a contracted condition; Fig. 2 is a side elevation view similar to Fig. 1 except showing the driving spring in an extended condition;

Fig. 3 is a side elevation view similar to Fig. 2 except showing the tool inverted with the nail setting tool member engaging the work surface;

Fig. 4 is vertical cross sectional view of the center punch shown in Fig. 1 illustrating more fully the center punch tool member and the nail setting tool member;

Fig. 5 is an enlarged view of the center punch tool member;

Fig. 6 is an enlarged view of the center punch tool member and one end of the tension driving spring as the one end of the driving spring is being mounted on the center punch tool member; Fig. 7 is an enlarged view similar to Fig. 6 showing the one end of the driving spring fully mounted on the center punch member;

Fig. 8 is an enlarged view of the nail setting tool member;

Fig. 9 is an enlarged view of the tool member and an opposite end of the tension driving spring as the opposite end of the driving spring is being mounted on the nail setting tool member;

Fig. 10 is an enlarged view similar to Fig. 9 showing the opposite end of the driving spring fully mounted on the nail setting tool member; and

Fig. 11 is an view similar to Fig. 1, except showing an alternate embodiment with different size nail setting tool members being mounted at opposite ends of the tool.

Best Modes for Carrying Out the Invention and Disclosure of Invention

A preferred embodiment of the invention is disclosed in the attached drawings showing a hand impact tool generally designated with the numeral 10. The tool 10 may have several combination of tool elements or members 14 such as combination prick punch and center punch, combination center punch and nail setter, combination center punch and brad setter, combination nail setter and brad setter or combination nail setter of one size and nail setter of another size. The hand impact tool 10 is designed to perform work on a work surface 12 by one of the tool members 14 either by forming indentations in the surface 12 or by driving nails or brads or the like into the work surface 12.

The hand impact tool 10, illustrated in Fig. 1-10, has a center punch tool member 14a at one end and a nail setter tool member 14b at the opposite end. In Fig. 1 and 2 the center punch tool member 14a is shown engaging the work surface 12. In Fig. 3, the tool is reversed showing the nail setter tool member 14b adjacent the work surface 12. Fig. 11 shows an alternate configuration in which a small size nail setter tool member 14c is at one end and a larger size nail setter tool member 14d is at the opposite end to provide a single tool capable of being used with finishing nails of widely varying sizes. Each of the tool members 14 includes a rather elongated cylindrical body 16 having a predetermined maximum diameter. Preferably, the maximum diameter of the tool body 16 is between 0.65 cm. and 0.85 cm.

Elongated tool body 16 extends between a front end 18 having a tool tip 20 and an elongated cylindrical rear end 22 having an anvil surface 24. Preferably, the rear end 22 has a diameter that is substantially equal to the maximum diameter of the tool body 16. Preferably the rear end 22 has a longitudinal length that is greater than twice, and more preferably greater than four times, the maximum diameter of the tool body 16. Most preferably the rear end 22 has a longitudinal dimension of between 1.50 cm and 3.50 cm. The anvil surface 24 includes an anvil peripheral bevel 25 to facilitate assembly of the tool 10 and alignment of the impact force and to minimize anvil deformation along the peripheral edge.

Each of the tool members 14 has a finger gripping section 26 that is intermediate the front end 18 and cylindrical rear end 22 to enable the user to firmly grip the tool member 14 between the thumb and forefinger of one hand

to position and hold the tool tip 20 adjacent to or in engagement with the work surface 12. The section 26 has enhanced gripping interlocking friction characteristics (large coefficient of friction with respect to human fingers) to minimize the unintentional release of the tool member 14 during usage. Each tool member 14 further includes a spring latching groove 28 that is formed in the tool body 16 intermediate the finger gripping section 26 and the cylindrical rear end 22. The spring latching groove 28 forms a latching shoulder 30 in conjunction with the cylindrical rear end 22.

The hand impact tool 10 includes elongated tension coil spring 60 that has a rather constant diameter central section 62 that extends between reduced spring ends 64 and 66. The reduced spring ends 64 and 66 comprise at least two complete 360 degree coil turns, and preferably between two and five turns. Preferably, the coil spring 60 is made from a high quality spring music wire. Preferably, the coil spring 60 has an initial pre-load or pre-tension of at least 2 oz. and preferably 1.0 to 1.5 lbs. so that the anvil surfaces 24 and 46 are maintained in engagement when the tool is not in use and to increase axial alignment of the anvil surfaces 24 when in use.

The coil spring 60 preferably has sufficient strength to enable the spring to expand between 200 percent and 500 percent of its original length upon the application of the separation force between the two tool members 14a and 14b that is between 10 and 15 lbs. The central section 62 has a small angle helical spiral with a rather large diameter relative to the tool body 16 to maximize stored energy in the central section 62, when the coil is expanded. Preferably, the central section 62 has an inside diameter that is between 0.80 cm. and 0.90 cm. The inside diameter of the central section 62 is greater than the diameters of the rear ends 22 so that coils of the spring 60 do not interfere with the movement of the rear ends 22. Preferably, the reduced spring ends 64 and 66 have an inside diameter of between 0.50 cm. and 0.85 cm. Most preferably, the reduced spring ends 64, 66 have an inside diameter of approximately 0.66 cm. The spring music wire itself, preferably has a diameter of approximately 0.10 cm.

Preferably, the depth of the spring latching grooves 28 have a depth that is greater than one-half of the diameter of the spring wire of the coil spring 60. Preferably, the depth of the spring latching groove 28 is between 0.050 cm. and 0.080 cm.

The tool tip 20 of the center punch member 14a (illustrated in Figs. 5-7) has a center punch bevel 70 of approximately 35°. The nail setter tool member 14b, illustrated in Fig. 8-10, has an insert bevel 74 for receiving the head of a nail. The nail setter tool members 14c and 14d illustrated in Fig. 11 have insert bevels 76 and 78 respectively for receiving the heads of different size finishing nails.

As previously mentioned, the frictional characteristics of the finger gripping sections 26 are greatly enhanced in minimize premature release of the tool members 14. Preferably, the finger gripping friction characteristics of sections 26 are substantially equal on each of the tool members 14 of each tool 10 so that a person can easily maintain their grip on one of the tool members 14, and hold the one tool member adjacent to or in engagement with the work surface 12 before the other tool member 14 is released, as illustrated in Fig. 2.

Each of the finger gripping sections 26 includes a series of spaced annular grooves 80 formed in the tool body 16 having a depth greater than 0.040 cm. Preferably, the depth of each of the grooves 80 is between 0.040 cm. and 0.080 cm., and more preferably between 0.050 cm. and 0.080 cm. The annular spaced grooves 40 form at least two spaced rings 82. In a preferred embodiment, the grooves 80 form annular sharp edges 84 at the sides of the rings 82 to dramatically increase the gripping friction between the user's fingers and the members 14.

Each of the annular grooves 80 has a width that is between 1.5 and 2.5 times the depth of the grooves 80. Preferably, the width of the grooves 80 is between 0.120 cm. and 0.200 cm. Each of the rings 82 has a width that is preferably between 1.5 and 2.5 times the depth of the grooves 80. More preferably, the width of the rings 82 is between 0.120 cm. and 0.200 cm. The large frictional characteristics of the finger gripping sections 26 and 52 increase the safety in use of the hand impact tool, and additionally enables the user to quickly learn the proper distance to retract the tool members to obtain the desired results.

One of the advantages of the hand impact tool 10 is its ease of assembly. No special tools are required. As illustrated in Figs. 5 and 6, the elongated coil spring 60, and particularly the reduced spring end 64, 66 are easily mounted in their respective latching grooves 26. This is accomplished by merely pushing and rotating the spring ends 64 and 66 against the beveled anvil surfaces 25 (Figs. 6 and 9). The peripheral bevel 25 causes the reduced spring ends 64 and

66 to temporarily expand so that the spring end ends may be slid along the full lengths of the rear ends 22 as illustrated in Fig. 7 and 10. The reduced spring ends 64 and 66 then snaps into the spring latching grooves 26 for permanent attachment with one of the coil turns, firmly engaging the latching shoulder 30 for. preventing the release of the reduced spring end 64 or 66 from their respective member 14.

Use of the hand impact tool is illustrated in Figs. 1-3 and 11. Initially, the user grips the hand impact tool with one hand in which a finger and thumb engages and grips the finger gripping section 26 of tool member 14a as illustrated in Fig. 1 to position the combination center punch and nail setter tool 10 with respect to the work surface 12. After the correct position has been obtained, the user, with the thumb and index finger of the other hand grips the finger gripping section 26 of the nail setter tool member 14b and begins to pull the member 14b away from the tool member 14a as illustrated in Fig. 2. Such movement causes the anvil surfaces 24 to separate, and to increase the tension on the spring 60. As the coil spring expands, it increases its potential energy which is converted into dynamic energy when the nail setter member 14b is released. When released, the spring 60 contracts, driving the anvil surface 25 of the nail setter member into impact engagement with the anvil surface 24 of the center punch member 14a transferring the dynamic energy of the nail setter member 14b to the tool member 14a. In this way, a very rapid and high energy impact force is applied to the tool tip 20 and the work surface 12 to rapidly deform the work surface 12.

Consequently the tool may be used with work surfaces having a wide variance in hardness. Even more importantly the tool can be use on work surfaces that are quite brittle without breaking the work surface since the application of force is accomplished very rapidly causing deformation of the work surface, without fracturing. In a preferred embodiment, each of the tool members 14 are made from the same stock of steel material. The tool members 14 are appropriately heat treated to minimize fracture, fatigue and brittleness, while minimizing deformation of the anvil surfaces 24 over extended use.