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UL 62841-4-1-2020 pdf free download

UL 62841-4-1-2020 pdf free download.Electric Motor-Operated Hand-Held Tools, Transportable Tools And Lawn And Garden Machinery — Safety — Part 4-1: Particular Requirements For Chain Saws.
With the power switch in the “on” position and the chain saw disconnected from the power source, the force on the front hand guard needed to activate the brake shall be measured at the centre of the top (horizontal) pert of the front hand guard and in the direction of 450 fonvard and downward in relation to the guide bar centreline, see Figure 106.
The force shall be applied at a uniform rate. The average braking time shall not exceed 0,12 s and the maximum braking time shall not exceed 0,155.
Compliance is checked by the following test.
The chain saw and saw chain tension shall be adjusted as for normal use, as specified in 8.14.2. The chain saw shall be run in before starting the test by performing 10 on”Poff’ cycles with the power switch. One cycle consists of 30 s running and 30s rest. After the run-in, the saw chain tension shall be adjusted according to the manufacturer’s recommendations. If no recommendations are provided, the saw chain tension shall generally be adjusted so that, when a 1 kg mass is hanging from the centre of the cutting length along the lower portion of the saw chain, the gap between the saw chain side link and the guide bar is a minimum of 0,017 mm per millimetre of guide bar length.
With the saw chain lubricated as in normal use, and operated at rated voltage and maximum speed, the front hand guard is set in motion by the impact of a pendulum. This pendulum shall have a mass of 0,70 kg, a hammer with a flat strike face of 50 mm diameter and an arm of 700 mm length. The pendulum drop height shall be 200 mm. Any special hardware arid/or software used to achieve maximum speed in accordance with 5.101 shall not influence the braking performance provided by the chain brake. The time for the saw chain to stop shall be measured from the moment of impact with the front hand guard (see Figure 107).
The chain brake shall be operated a total of 25 times, The maximum stopping time and the average stopping time of the saw chain shall be determined at the first five and the last five braking operations.
The saw chain is considered to be stopped when the time taken for two successive drive links (see dimension a in Figure 108) to pass a fixed point exceeds 5 ms.
The tests shall be done in 2 mm intervals, comprising a nooad running period of I mm prior to each impact of the pendulum. immediately after the operation of the chain brake and the saw chain has stopped, the chain saw shall be switched off for the remainder of the inteival. The chain brake actuation mechanism shall be reset during this off period.
19.107.2 Chain saws with a maximum speed of the saw chain above 15 m/s shall be equipped with a non-manually activated chain brake that is sufficiently sensitive to operate when kickback occurs.UL 62841-4-1-2020 pdf free download.

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