Cutlery – Blades – Rotary
Reexamination Certificate
2002-04-23
2003-11-11
Watts, Douglas D. (Department: 3724)
Cutlery
Blades
Rotary
C030S276000, C056S012700
Reexamination Certificate
active
06643938
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to string trimmers, i.e., weed trimmers, of the type in which one or more lengths of a nylon or other type of string or line project radially from the rotary cutting head of the trimmer, and in which the moving cutting string slashes and severs leaves and stems of plants. The invention is also directed to a system and technique that facilitates replacing the string or line on the string trimmer. String trimmers may be of a fixed-string arrangement or of an extendible line arrangement, and this replacement string attachment may be used with either type.
Current string trimmers or weed trimmers typically have a cutting head in which line or string is wound upon a reel or spool, with the spool being situated inside an outer shell of the cutting head. There is a free end of the line projecting out through this shell, and that is what contacts the grass or weeds for cutting. The string trimmer may be gasoline powered, or electric (AC or battery), with a motor drive that spins the cutting head. The reel or spool typically has an annular bay, i.e., a recess in which the string is wound, and there may be two or more bays on the spool, with a cutting string reposed in each bay. The action of cutting grass and weeds abrades and wears out the string, and so the string has to be continually let out from the spool. When all the string has been used up, then the user has to rewind more string onto the spool, and that can be a difficult, tedious process. The line that is used may be too stiff to be handled easily, and because the dimensions of the bays on the spool are usually smaller than the size of the user's fingers, it is difficult to hold the string and secure it to the reel to start the rewinding process. Also, this type of trimmer is limited to using strings of round cross section or profile, and thus precludes the use of strings of other profiles that may actually be more suited to cutting some types of vegetation.
Several types of fixed string trimmers are also present in the current state of the art, and these typically have the string tied or secured to some part of the cutting head. In that case, if there is a failure or breakage of the cutting string, the string would have to be untied and replaced with a new string. In that case, the portion of the cutting head where the string is secured serves the purpose of the spool and bay of the spool type trimmer. Because the string has to be threaded through the cutting head and may have to be tied, there are also similar problems presented to the user when the time comes to secure the replacement string onto the trimmer.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a trimmer replacement string arrangement that is simple to install and use, and which avoids the drawbacks of the prior art.
It is another object to provide a replacement trimmer string arrangement that can be employed with a large variety of existing string trimmers, and can be installed without need for any special tools.
It is a further object to provide a replacement trimmer string arrangement that can employ cutting strings of a wide variety of profiles and cross sections, and which can be made of a variety of suitable materials.
According to an aspect of this invention, a replacement string arrangement is provided for a string trimmer of the type having a rotary cutting head in which a spool (or the equivalent in the case of a fixed string trimmer) that may have one or several annular bays is provided to hold a length of cutting string. The replacement string arrangement employs a brace having an arcuate member with an annular guide tunnel or guide sleeve at one end of the arcuate member. The cutting string has one end affixed at a second end of the arcuate member of the brace, and the string extends out that one end, then after forming a loop or bight, passes slidably through said guide tunnel and continues radially outward, so that a free end that projects from the cutting head when the replacement string arrangement is installed in the cutting head. The brace and string can be of the same material and unitarily formed, or the string can be formed separately and fused into the one end of the arcuate member. In a favorable embodiment, the brace may have a “wishbone” shape (generally, a figure “7” or mirror image thereof). The string may be of a nylon monofilament, or may be any other suitable string, which may in some cases be woven or braided. The string may be shaped, as well, for improved aerodynamics or improved cutting.
The replacement string arrangement of this invention is installed by slipping the loop or bight of the string) over the spool to fit into a desired one of the bays, and then the user simply pulls the free end out to tighten the device against the spool. The free end may be passed through a guide that is provided on the shell or cover of the cutting head. In operation, the rotation of the unit pulls the cutting string device more snugly and securely against the spool, due to centrifugal force.
The above and many other objects, features, and advantages of this invention will become apparent from the ensuing detailed description of a preferred embodiment, which is illustrated in the Accompanying Drawing.
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Molldrem, Jr. Bernhard P.
Watts Douglas D.
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