A saw 10 has a handle 11 and a blade 12 projecting from the handle. The blade 12 has an edge 14 along which a plurality of saw teeth 15 project. The saw 10 further includes a flexible and retractable saw guard 20 which is connected to the saw 10 and which is retractable from a guard position in which the saw guard 20 overlies the saw teeth 14 and a retracted position in which the saw teeth 14 are exposed.

A protective apparatus and a machine tool are provided. The machine tool includes an operational element, a driving element, and the protective apparatus. The operational element and the driving element are disposed on machine table. The protective apparatus includes an insulating unit, conducting unit, capacitance sensor, and control unit. The insulating unit is disposed between the operational element and the driving element. The driving element drives the operational element by the insulating unit. The conducting unit contacts the operational element. The capacitance sensor electrically connects the conducting unit for sensing capacitance of the conducting unit. The control unit electrically connects the capacitance sensor and the driving element and determines whether a user approaches the operational element based on the capacitance. When the control unit detects that the distance between the user and the operational element is too close, the control unit stops the operation of the operational element.

A saw apparatus includes a guide bar, a chain driver, and an endless cutting chain trained about the guide bar and the chain driver. The guide bar includes a first chain retention feature along at least a portion of its periphery, and the cutting chain includes a second chain retention feature configured to interact with the first chain retention feature such that movement of the second chain retention feature away from the guide bar is restricted. A timber-working device includes a frame, at least one pair of arms pivotally attached to the frame and configured to be controlled to grasp at least one tree, and the saw apparatus mounted to the frame.

Table saws with safety systems are disclosed. The safety systems detect and react to dangerous conditions, such as contact between the blade and a person. The table saws may include a switch, a first light that illuminates to indicate the safety system is operable, and a second light that illuminates to indicate that the safety system is inoperable. The switch may not power the saw when switched on if the second light is illuminated.

Table saws with safety systems are disclosed. The safety systems detect and react to dangerous conditions, such as contact between the blade and a person. The table saws may include a switch, a first light that illuminates to indicate the safety system is operable, and a second light that illuminates to indicate that the safety system is inoperable. The switch may not power the saw when switched on if the second light is illuminated.

A power tool includes a motor; an arbor attachment mechanism that includes a shaft configured to be driven by the motor about a spin axis. The arbor attachment mechanism is configured to hold a blade onto the shaft. The power tool includes a blade size limiter that is configured to prevent attachment of a blade with a radius greater than a predetermined size, and is configured to be connected to the arbor attachment mechanism independently of the attachment of the blade to the arbor attachment mechanism and such that the blade size limiter is at a distance from the spin axis of the shaft.

The disclosed technology generally regards a chainsaw guard mountable on a chainsaw having a motor powerhead housing, a drive motor contained in the housing, a saw chain guide bar mounted on the housing, and a saw cutter chain driven by the drive motor and carried on the saw chain guide bar, the chainsaw guard forming a physical barrier that limits access to the saw cutter chain when the chainsaw guard is mounted on the powerhead housing. The chainsaw guard includes a bracket member mountable to a chainsaw motor powerhead housing, and a retractable member movably engaged with the bracket member and designed and configured to sheathe the saw chain guide bar and saw cutter chain of the chainsaw when the chainsaw guard is mounted on a chainsaw. Engaged with the bracket member and the retractable member are compressible springs about one or more guide rods, the springs having a spring force to position the retractable member relative to the bracket member in the extended position until a force greater than the spring force is applied to the distal end of the retractable member, translating the retractable member towards the retracted position; when the force is removed from the distal end of the retractable member, the retractable member by the spring force moves to the extended position.

Examples herein include a chainsaw bar shield and a method for using a chainsaw bar shield. A chainsaw bar shield comprises a bar shield arm extending from at least one securing mechanism for engaging and pinching a chainsaw bar extending from a chainsaw housing. The securing mechanism offsets the bar shield arm from a chainsaw chain extending from the chainsaw housing and, thereby, protects a user by separating the user from the chainsaw chain during maintenance of a chainsaw. Other examples of a chainsaw bar shield comprise an enclosure secured to a chainsaw bar which is offset from and substantially encloses a chainsaw chain extending from a chainsaw housing.

Power tools with conductive couplings used with active injury mitigation technology are disclosed. Conductive couplings are particularly relevant to table saws, hand-held circular saws, track saws, miter saws, and band saws with active injury mitigation technology. Conductive couplings provide a mechanism through which an electrical signal can be coupled or imparted to a blade, and then monitored for changes indicative of human contact with the blade. An exemplary conductive coupling includes a brush that establishes an electrical connection with a moving part of a power tool, and the brush maintains contact with the moving part of the power tool during at least 40 hours of cumulative time when the motor is spinning the arbor and blade without an interruption in the electrical connection sufficient to trigger the reaction system. A conductive coupling may be two-sided compliant. A conductive coupling may connect to a motor shaft to minimize electrical noise.

A method is provided for detecting a substance, preferably human tissue, in the vicinity of a mobile tool, wherein the substance to be detected has different electrical characteristics from a material that can be processed by the mobile tool. In the method, a change is detected in a capacitance formed by the tool and a counter electrode that is electrically insulated from the tool. A periodic change in the capacitance is detected and the change is produced by the presence of the substance in a region in relation to the tool and by a periodic change in a geometrical characteristic of the tool in this region as the tool moves.