Inspection Of The Push-Button Switch; Inspection Of The Limit Switch - Hitachi L Series Service Manual

6-9. Inspection of the push-button switch

Please check the push-button switch in the following way with the power shut off. Exchange when an abnormality
is found.
(1) Does the pushbutton switch work correctly?
(2) Are there damage or cracks in the case, cover etc.?
(3) When the cover is removed, is there any screw loosening or an abnormality in the lead wires?
(4) Is there any foreign matter in it or are the contacts abnormally worn?

6-10. Inspection of the limit switch

1. Regarding the limit switch (upper / lower limit stop device), please perform the following inspection.
( 1 ) The limit switch must operate reliably at the upper and lower limits.
( 2 ) The limit lever is not deformed, and it operates smoothly.
( 3 ) The limit spring is not deformed or dropped off.
* Please be careful with dropping off when particularly assembling after disassembly.
2. Confirmation of hoist margin and lowering margin
When the hoist margin and lowering margin (deviation from the original spring dimensions when the limit
switch kick in) is lower than the specification, there is a risk of the brake slippage becoming larger or the
limiting spring getting deformed, which may lead to serious accidents due to excessive force being applied to
the main body or on the limit lever during the operation of the limit switch.
• How to check hoist and lowering margin
( 1 ) Measure the A and B dimensions of the point where the limit switch stopped at the upper limit and the
lower limit.
( 2 ) From the measured A and B dimensions and the H
dimension (original limit spring dimension) shown
on the right table, calculate the hoist and lowering
margin by the following calculation formula.
Hoist margin = A - H, Lowering margin = B - H
3. Confirm contact wear
( 1 ) Remove the housing and take out the limit switch in state of shutting off power from the Electric chain
hoist.
( 2 ) Examine through the side hole of the limit switch and check the condition of wear and discoloration of the
contacts.
* If there is abnormality in the contact, please exchange the limit switch.
Hoist margin
Lowering margin
A
* The above figure shows the cover removal status.
- 25 -
50mm or more
3mm or more
Rated load
500kg, 250kg
150kg
B
Unit : mm
H
22.5
44