Tools – Hammer – Having shock absorbing means
Reexamination Certificate
2000-10-26
2001-11-06
Smith, James G. (Department: 3723)
Tools
Hammer
Having shock absorbing means
C081S020000
Reexamination Certificate
active
06311582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to carpenters' claw hammers for driving and removing nails and striking various objects, and in particular, shock absorbing or dead blow hammers that reduce the recoil and vibration caused by the hammer strike. More particularly, the present invention relates to a shock absorbing hammer including a claw feature and a natural hickory wood, fiberglass, steel or other material handle.
When a percussive tool such as a hammer strikes the surface of an object, part of the energy produced by the strike is used to perform desired work, (e.g. drive a nail) part is converted into heat, and part is dissipated through the hammer. The energy dissipated through the handle often produces undesirable results such as recoil of the hammer from the object being struck or excessive vibration. These undesirable effects have been a persistent problem for the makers of hammers and other percussive tools. Many users of hammers prefer the vibration-reducing feel of wood handled hammers over those with solid steel or fiberglass handles. Hickory wood handles are often the preferred choice of professionals because of the natural feel of the wood and a common perception is that fatigue is reduced at the end of the day when using such.
Past attempts to reduce undesirable results from using hammers include designs which incorporate dampers of shock absorbers of various kinds to produce what is referred to as “dead blow” hammers. One of the earliest attempts to produce such a hammer is reflected in U.S. Pat. No. 1,045,145 issued in November 1912 to E. O. Hubbard. Hubbard explains that the head of a “dead blow” hammer struck against a surface will be forced against a cushion, such that the cushion absorbs a portion of the shock impact caused by the strike.
Several early approaches for reducing recoil in hammers are summarized in U.S. Pat. No. 2,604,914 to Kahlen issued in July 1952. In particular, Kahlen indicates that by 1952, known methods for reducing recoil included placing either a slug, a charge of round shot, or a charge of powdered material in a chamber immediately behind a striking face of the hammer, such that an object(s) placed behind the striking head will absorb some of the forces produced by the hammer strike. The particular approach disclosed in Kahlen involved the placement of a charge of irregularly shaped hard heavy particles in a chamber immediately behind the striking head of a hammer. In addition to solutions involving cushions and charge loads, several solutions utilizing resilient members, such as elastic inserts and springs, were proposed to address the hammer strike problems, whereby a portion of the energy developed from the hammer strike is dissipated through the resilient member. Other designs such as that disclosed in U.S. Pat. No. 5,408,902 use a “lagging mass”, which is positioned to move towards the striking portion of the hammer head upon impact, thus impacting the striking portion to reduce hammer recoil. Previous shot filled hammers have been limited: (i) because the requirement for a hollow chamber renders the size of such hammers out of proportion to their weight; and (ii) because, unless a special shot mixture is utilized, the shot is often not useful in preventing hammer recoil. Moreover, in prior art “dead blow” hammers, the prying and nail pulling capability of common claw hammers has been forfeited in the attempts to reduce vibration and recoil.
Further discussion of the prior art and its associated shortcomings us provided in U.S. Pat. No. 1,045,145; in U.S. Pat. No. 2,604,914; in U.S. Pat. No. 2,928,444: in U.S. Pat. No. 4,831,901; in U.S. Pat. No. 5,118,117; in U.S. Pat. No. 5,408,902; and German Patent No, 1,273,449.
Thus a need exists for a shock absorbing hammer which includes a claw feature for pulling nails and prying, and which addresses other problems associated with prior art shock absorbing or dead blow hammers.
SUMMARY OF THE INVENTION
In one aspect of the invention, a shock-absorbing claw hammer includes a natural hickory wood, fiberglass, steel or other material handle and a head which has a striking head portion with a lower surface, a claw portion extending generally opposite the striking head portion. The handle extends generally perpendicular to the sting head portion and the claw portion. The head defines an opening therein and the opening extends completely through at an angle perpendicular to the axis of both the striking head portion and the claw portion. The opening is rectangular in shape and stepped down from a larger chamber to a smaller one into which the tang of the handle can be offered up. The larger chamber has inset steps forming stops onto which a cover plate can be slideably fitted. The remainder of the larger chamber is open to receive steel, lead, titanium or other metal shot weight which is thereafter sealed inside the chamber by the cover plate being fitted and welded in place.
In another aspect of the invention in its assembled form, the hammer's hickory (or other suitable wood or material) handle is offered up into the rear opening of the head and affixed there using epoxy. The epoxy serves the multiple purposes of: (i) affixing the head to the handle; (ii) forming a “floor” in the cavity of the head; (iii) acting as a shock absorber for the metal shot which are loaded and sealed within the head cavity. A steel cover plate is inserted into the stepped opening into the head and welded in place to contain the metal shot. The entire head is thereafter cleaned and finished to produce a smooth esthetic appearance.
The drawings attached hereto will illustrate to those skilled in the art that the present invention is an improvement on the prior art dead blow hammers by reason of the addition of a claw, which is a vital feature in the construction trade, the use of a large shot-filled ballast cavity axially aligned with the striking face and the claw, and the welded cover plate, which when finished by grinding and polishing, becomes an integral part of the hammer head. Additionally, the use of an epoxy adhesive to affix the handle and to act as a shock absorbing medium for the inertial forces within the metal shot and the head itself, is an economical and practical way to combine the discrete components of the hammer in a unique way, permitting the use of old traditional materials (hickory or other woods) and modern computer designed metal castings.
REFERENCES:
patent: 3130762 (1964-04-01), Kerr
patent: 3343576 (1967-09-01), Norcross
patent: 4039012 (1977-08-01), Cook
patent: 4831901 (1989-05-01), Kinne
patent: 5320001 (1994-06-01), Floyd
patent: 5916338 (1999-06-01), Bergkvist et al.
patent: 5960677 (1999-10-01), Carmien
patent: 6128977 (2000-10-01), Gierer et al.
Lukasik Frank A.
Shakeri Hadi
Smith James G.
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