Cutlery – Cutting tools – Saw
Reexamination Certificate
2001-01-30
2002-05-21
Watts, Douglas D. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S386000
Reexamination Certificate
active
06389700
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a protective guard for conventional portable chainsaws, including those with saw dogs. This invention is suitable for use when a chainsaw is carried, transported, or stored, thereby reducing the possibility of injury to the individual carrying or handling the chainsaw, and also reducing the possibility of damaging the cutter chain or saw dogs of the chainsaw during such activities.
2. Description of the Prior Art
Because of the sharp edges of cutter chains and also of saw dogs when present on conventional chainsaws, chainsaws may cause injuries to the individuals carrying or handling the chainsaws, and their sharp edges may be damaged by unintended contact with objects.
One way previously proposed to minimize the risk of such injuries and damage was to place a chainsaw in a sealed portable case or similar container. However, the substantial weight and volume of such cases rendered them unattractive to individuals using them, especially loggers, who frequently have to carry chainsaws on foot to working sites. Exemplary such cases are described in Schurman U.S. Pat. No. 4,369,575 granted Jan. 25, 1983, Reynolds U.S. Pat. No. 5,119,937 granted Jun. 9, 1992, and Griffin U.S. Design Pat. No. 359,849 granted Jul. 4, 1995.
Another way previously proposed to prevent such injuries was to provide a guard, sheath, or the like to limit access to the cutter chain. However, in many such proposed devices, the protection of the individual primarily sought was protection during the sawing operation, not primarily protection during carrying or transporting the chainsaws. For example, many bar guards, sheaths, or the like were designed to prevent kickback when operating the chainsaw. Therefore, a portion of the cutter chain was always exposed when using such devices; the possibility of damage or injury during transportation was not prevented. An exemplary such partially open guard is illustrated in Holzworth U.S. Pat. No. 4,193,193 granted Mar. 18, 1980. A similar such guard hingedly connected to the saw is described in Shivers U.S. Pat. No. 4,621,426 granted Nov. 11, 1986. The Shivers bar guard is expensive and awkward to use; it remains attached to the saw during the sawing operation while it is pivoted upwards away from the guard, interfering with the operator's view of the log or other workpiece.
Other such protective devices often required some modification of the chainsaw itself. By way of example, in Otoupalik U.S. Pat. No. 3,042,087 granted Jul. 3, 1962, a protective sheath was designed to be removably attached to the chainsaw by a pair of removable tension springs. The cutter chain was completely sealed when the sheath was attached. However, the primary objective of the above mentioned invention was to protect the cutter chain and guide bar from damage during transportation of the chainsaw. As a result, the combined chainsaw and guard remained hazardous to the person carrying the chainsaw with the sheath thereon. For example, since the tension springs were hooked onto the chainsaw handle bar, the springs often interfered with carrying the chainsaw. Further, when the sheath was attached, the tension springs were always in extension. Thus, it was quite possible that the person carrying the chainsaw with the sheath thereon might be injured by the tension spring if it were accidentally dislodged. Finally, the sheath was not intended to cover saw dogs, and in fact, the tension springs extended in the vicinity of the saw dogs when they were attached to the handle bars. Therefore, simply by using the prior Otoupalik device, the risk of at least some types of injury increased.
An expensive and complex solution to the chainsaw guard protection problem is illustrated in Woleslagle U.S. Pat. No. 2,683,944 granted May 19, 1953. The telescoping sheath described by Woleslagle is awkward to use and necessarily bulky at one end to accommodate the series of telescoping elements when they are collapsed.
SUMMARY OF THE INVENTION
The present invention is a detachable bar guard that is inexpensive to manufacture, easy to attach to and detach from the chainsaw, secure when in place on the chainsaw bar, fully protective of both the cutter chain and the individual carrying the saw, including protection for and from saw dogs when present, lightweight and unobstructive.
A preferred embodiment of the invention comprises an elongate sleeve or sheath that shields substantially all normally exposed portions of the cutter chain on the guard bar, and also may be configured to provide the same shielding to saw dogs if present. Optionally, the flat of the sleeve may be provided with open areas to reduce weight. The proximal end of the sleeve is provided with a snap-clip mechanism to attach the sleeve to the chainsaw.
The inventor recognized that most chainsaws are designed to mount the bar to the saw housing or frame by means of a pair of spaced attachment/adjustment bolts that engage mating slots in the bar; as the chain wears and becomes looser, the nuts on the bolts are loosened and the bar is then moved distally relative to the driving sprocket of the chainsaw so as to tighten the chain on the bar. These adjustment nuts are invariably or almost invariably exposed to easy access to facilitate bar position adjustment. Further, although not quite uniformly placed or spaced from one saw design to another, the nuts are placed and spaced quite similarly from one chainsaw to another.
Accordingly, it is possible to provide a snap-clip mechanism on a sleeve according to the invention that mates with the retainer space between sequential adjustment nuts and that may be adjustable or adaptable to suit a range of chainsaws. The snap-clip mechanism includes a retaining claw that is biased into contact with the chainsaw frame or bar mounting plate or the like in the retainer space between the two bar guide adjustment nuts. The claw may be an elastic element fixed to or integral with the sleeve and configured so that under the biasing force, the claw is normally retained in place between the adjustment nuts. Alternatively, the claw may be rigid but pivotally mounted on the sleeve for biased engagement; a suitable biasing means such as a coil spring provides the bias force.
The claw/clip dimensions and configuration may be varied and selected to permit some longitudinal adaptability of the snap-clip mechanism to fit different chainsaws. Alternatively, the claw may be slidably mounted to the sleeve so that by sliding the claw into different mounting positions, it may fit different chainsaws. The sleeve may be oversized to fit both those bars in which there is little clearance between the chain and the interior walls of the sleeve and also smaller bars, or instead the sleeve may be made in a variety of sizes to fit bars of various standard lengths, or both.
Many types of plastics material are suitable for manufacture of the sleeve; such materials are sufficiently rigid to provide good protection for the chain and saw dogs when manufactured with relatively thin, lightweight walls, sufficiently soft not to damage the saw teeth if impacting against the teeth, and sufficiently flexible that a claw formed integrally with the sleeve is easily deflected to permit engagement and disengagement of the claw with the retainer space between the adjustment nuts. A somewhat less expensive and generally satisfactory manufacture of the guard can be effected using sheet steel for the sleeve and welding the snap-fit mechanism thereto; this solution entails some slight risk of dulling saw teeth if and when they come into frictional or impact contact with the guard, but the risk is probably acceptable because the saw teeth become dull with use in any case.
A sleeve-and-claw arrangement of the foregoing sort constitutes a secure bar guard protecting both the sawbar and the user that is easily secured to and released from the chainsaw, is lightweight, comfortable to someone carrying the chainsaw on the shoulder or otherwise, and inexpensive to manufacture. A claw arrangem
Barrigar Robert H.
Watts Douglas D.
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