UL 62841-4-1:2020 free download

UL 62841-4-1:2020 free download Electric Motor-Operated Hand-Held Tools, Transportable Tools And Lawn And Garden Machinery – Safety – Part 4-1: Particular Requirements For Chain Saws
NOTE In New Zealand, the following conditions apply:
All chain saws shall be fitted with a manually activated chain brake.
19.107.1.1 The manually activated chain brake shall be designed so that the static activation forcerequired is not more than 60 N and not less than 20 N.
Compliance is checked by the following test.
With the power switch in the “on” position and the chain saw disconnected from the power source, theforce on the front hand guard needed to activate the brake shall be measured at the centre of the top(horizontal) part of the front hand guard and in the direction of 45° forward and downward in relation tothe guide bar centreline, see Figure 106.
The force shall be applied at a uniform rate.
19.107.1.2 The average braking time shall not exceed 0,12 s and the maximum braking time shall notexceed 0,15 s.
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.Thechain saw shall be run in before starting the test by performing 10 on””off” cycles with the power switch.
One cycle consists of 30 s running and 30 s rest. After the run-in, the saw chain tension shall be adjustedaccording to the manufacturer’s recommendations. lf no recommendations are provided, the saw chaintension shall generally be adjusted so that, when a 1 kg mass is hanging from the centre of the cuttinglength along the lower portion of the saw chain, the gap between the saw chain side link and the guidebar 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 of0,70 kg, a hammer with a flat strike face of 50 mm diameter and an arm of 700 mm length.The pendulumdrop height shall be 200 mm.Any special hardware and/or software used to achieve maximum speed inaccordance with 5.101 shall not influence the braking performance provided by the chain brake.The timefor the saw chain to stop shall be measured from the moment of impact with the front hand guard (seeFigure 107).
The chain brake shall be operated a total of 25 times. The maximum stopping time and the averagestopping 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 (seedimension a in Figure 108) to pass a fixed point exceeds 5 ms.
The tests shall be done in 2 min intervals,comprising a no-load running period of 1 min prior to eachimpact of the pendulum. lmmediately after the operation of the chain brake and the saw chain hasstopped, the chain saw shall be switched off for the remainder of the interval.The chain brake actuationmechanism shal be reset during this off period.
19.107.2 Chain saws with a maximum speed of the saw chain above 15 mls shall be equipped with anon-manually activated chain brake that is sufficiently sensitive to operate when kickback occurs.