Automatic Slack Adjusters
Need for Automatic Slack Adjusters
The process of adjusting the shoe clearance manually is cumbersome and time consuming, as we will be seeing now. The brake adjustments need several steps. Jack up the wheels and keep rotating the wheel. Then press the worm shaft clock completely and rotate worm shaft until the wheel locks. After this, rotate the worm shaft in the reverse direction until the wheel starts rotating freely. Then turn the worm shaft slightly and release the lock. Repeat this process for all the wheels. As it is difficult to maintain uniform clearance on all wheels and this can result in vehicle pulling to one side while braking.
Not only this process is time consuming and cumbersome but also keeps the vehicle off the road frequently, even though it is for about an hour. For example, when the truck is operated in the city roads, the clearance has to be adjusted once in 2 or 3 days and for long distance operation once in 10 or 15 days. It is seeing that until now the only available way to tackle this problem of shoe clearance is to manually adjust.
The only solution to overcome this problem is to use Automatic slack adjusters, which will maintain the pre-determined lining gap in all braking wheels by automatic adjustment of gap to compensate the lining wear due regular usage.
Automatic Slack Adjusters
Benefits in using the Automatic Slack Adjuster Assemblies
1. Properly adjusted brakes means increased safety to the vehicle operation at maximum brake efficiency.
2. Vehicle down time and labour expense for brake adjustment is reduced, since constant clearance between the brake lining and the drum is maintained automatically.
3. Automatic adjustment ensures uniform and constant clearance in all wheels. Thus providing good brake balance and stability during braking.
4. The brake chamber stroke is kept short and consuming less compressed air.
5. Automatic slack adjuster assemblies are well protected against water and dirt entry to give longer trouble free service.
6. Assembly comes pre-packed with grease also thereby eliminating the need for periodic lubrication.
The type of automatic slack adjusters is classified by its sensing mechanism and adjustment mechanism as follows:
1. Sensing mechanism
A) Clearance sensing
B) Stroke sensing
2. Adjustment mechanism
A) During release of brakes
B) During application of brakes.
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Automatic slack adjuster assemblies having clearance sensing and adjustment during release of brake features are preferred against other combinations due to its advantages:
1. In clearance sensing, the pre-determined gap between brake lining and drum is neglected during initial movement of Automatic Slack adjuster while applying the brakes and excess lining clearance is sensed in further stroking.
2. In addition the conical clutch provided on the worm shaft ensures die-engagement of sensing mechanism to ignore the brake push rod stroke due to the deflection of foundation brake structural parts, drum and brake lining thereby the excess lining gap due to wear is only considered for adjustment and not influenced by the elasticity of brakes or whether brake application is hard or gentle.
3. Brake adjustment during the release of brakes has major advantage of increased life of all parts related to adjustment mechanism, as it has to adjust against least load on the camshaft to rotate.
Automatic Slack Adjusters
How it works - general principles:
The Automatic Slack Adjuster, which incorporates the clearance sensing principle, senses the shoe clearance through a ‘one way’ clutch mechanism and adjusts the brake shoes by repositioning the “S” cam to maintain correct shoe clearance, automatically, at all times.
For all Global requirements contact
John Bruce UK Ltd..
Email: john@johnbruceukltd.com
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