Woodworking – Process – Mechanical cutting or shaping
Reexamination Certificate
2002-08-21
2004-03-16
Bray, W. Donald (Department: 3725)
Woodworking
Process
Mechanical cutting or shaping
C173S120000, C144S193100, C144S194000
Reexamination Certificate
active
06705364
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a log splitting apparatus and, in particular, a log splitting apparatus that uses a conical screw-form wedge.
BACKGROUND OF THE INVENTION
Log splitting apparatus that use conical screw-form wedges are disclosed in U.S. Pat. No. 4,091,851 (Ober 1978); U.S. Pat. No. 4,245,683 (Cedergren 1981) and U.S. Pat. No. 4,347,881 (Wickham et al 1982). The Ober reference discloses a log splitting apparatus driven by an internal combustion engine of about 5 to 8 horsepower capacity and having a maximum output speed of about 3500 to 3600 revolutions per minute. A speed reduction unit is used to reduce the revolutions per minute down between 60 to 70 revolution per minute, which is viewed by Ober as being the preferred operating range for splitting logs with a conical screw-form wedge. The Cedergren reference discloses a protective guard which mounts to a work table to protect a workman from injury when using a conical screw-form wedge in a shop environment. The log splitting machine is not described. The Wickham reference discloses a log splitting apparatus driven off of the power take off (PTO) of a tractor. The reference includes features to improve the manner in which logs are fed onto and off of the conical screw-form wedge and features to protect the PTO shaft from fracturing due to induced bending stresses.
The above described apparatus are suitable for persons splitting large volumes of logs. Such apparatus are not suitable for use by persons who wish to camp overnight or picnic during an afternoon outing. Persons who camp or picnic generally have limited storage space to transport a log splitting apparatus and only split a few logs.
SUMMARY OF THE INVENTION
What is required is a hand held portable log splitting apparatus.
According to a first aspect of the present invention there is provided an apparatus for splitting logs which includes a combination of an impact wrench and a conical screw-form wedge. The impact wrench has an output coupling that provides both rotary and reciprocating movement. The conical screw-form wedge is coupled to the output coupling of the impact wrench.
According to another aspect of the present invention there is provided a method of splitting logs. A first step involves providing an impact wrench and a conical screw-form wedge, as described above. A second step involves coupling the conical screw-form wedge to the output coupling of the impact wrench. A third step involves placing the apex of the conical screw-form wedge against a log and activating the rotary and reciprocating movement of the impact wrench. The combined rotary and reciprocating movement of the impact wrench drives the conical screw-form wedge into the log.
The prior art devices such as disclosed in the Ober reference and the Wickham et al reference rely upon generating sufficient torque output to drive the conical screw-form wedge into a log. When one attempts to provide a miniature portable log splitting apparatus follow the same principles as are found in the Ober reference and the Wickham et al reference, the results are not satisfactory as the torque generated is inadequate. In contrast, beneficial results may be obtained through the combination apparatus and method described above. The additional reciprocating movement of the impact wrench, enables the conical screw-form wedge to operate effectively with decreased torque.
REFERENCES:
patent: 4091851 (1978-05-01), Ober
patent: 4245683 (1981-01-01), Cedergren
patent: 4347881 (1982-09-01), Wickham et al.
patent: 4491164 (1985-01-01), Waikas et al.
patent: 4669552 (1987-06-01), Foster et al.
patent: 5018792 (1991-05-01), Roussin et al.
patent: 5622230 (1997-04-01), Giardino et al.
Bray W. Donald
Christensen O'Connor Johnson & Kindness PLLC
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