9 replies to this topic

[Tom T]

Guys, I posted this question in the Technical area, but haven't had more than 1 response. The response suggest I search on this topic as it has been "discussed at length". I did perform a search, and all related post that came up where more technical than I am looking for....a little over my head too.

Just wondering if anyone came briefly discribe the common types of braking system found on lifts. I understand the purpose and the design of the anti-rollback device. I am more curious about the service brake, emergency brake, and/or main brake systems.

I'm looking for simply stuff like their location on the lift, when they would be deployed, and basic design or how they stop the lift. In particular, is the main/service brake located above the pull weel, and it is tied in with the electric current of the lift? In others woulds, when deployed is the electric current powering the lift also stopped?

Any response (even brief) would really be appreciated.

[Lift Dinosaur]

Basically:
The service brake is generally applied to a service brake disc, which is generally on the high speed (input) shaft into the gear reducer. This is activated by a normal stop.
A. If the drive is regenative, meaning it feeds current back into itself to slow the lift, then the brake is applied when the lift reaches zero speed, in fact just slightly before that. In this case the service brake is like the parking brake on your car, holding the lift until it is given a signal to satrt again.
B. If the drive is non regen, then when a stop is activated, the drive shuts off and the lift starts to coast to a stop, with the service brake being applied at a pre-determined rate (generally through hydraulic flow control) to stop the lift at about the time it reaches zero speed.

The emergency brake is applied when an emergency stop is activated. It is generally a c-clamp looking device that clamps onto the top and bottom flanges of the bullwheel (drive sheave). It is also generally controled through hydraulic flow control.
When an emergency stop is activated, the drive is disconnected. Therefore, in the case of a regen drive, you no longer have the smooth deceleration rate of the drive to stop the lift. And thusly, if you have a lift with a regen drive, your BEST stop is an normal stop, NOT and emergency stop.
I hope this helps you dazzle your colleagues and also answers your question.

[Jonni]

I know that will all of our drives here at Sunapee, a normal stop usually stops the lift in a shorter distance than the E-Stop. The other thing is that if the E-brake track, (where the E-brake contacts the bullwheel), is rusty than when that brake is activated it makes a very loud screeching noise.

[Kelly]

Now that Lift Dinosaur has got you up to speed (pun intended) I will give you a few more details.
Most service brake designs are similar to car disk brakes – bigger of course.
Almost all operate in a failsafe mode if power is lost or if a hydraulic failure occurs.
Newer brake systems (last 15 years) can sense speed and load of lift and will apply a changing force to allow for smoother stops.
The hurdle lift engineers face in brake design is smooth deceleration in the lower speed ranges yet still have enough force to hold the lift from going backward. Which leads me to an anecdote about teaching my ham footed 16 year old daughter to drive but after further contemplation the story aspects are too technical for further elaboration.

Other Brakes
Rollback dog – separate from gearbox
Rollback dog – incorporated into gearbox
Lowspeed bullwheel shaft
Bullwheel dog – holds lift by engaging in bullwheel spokes
Haulrope – holds lift by grabbing haulrope

Other Breaks
Morning
Lunch
Afternoon

[lastchair_44]

Jonni, on Feb 24 2006, 06:30 PM, said:

I know that will all of our drives here at Sunapee, a normal stop usually stops the lift in a shorter distance than the E-Stop. The other thing is that if the E-brake track, (where the E-brake contacts the bullwheel), is rusty than when that brake is activated it makes a very loud screeching noise.

I like the decel supervision monthly checks...makes the terminal smell like the out of towner's cars going down the mine road

[Tom T]

Thanks guys. I took a hard look at my area's lifts yesterday. I found a braking system on the slope facing side of the bullwheel, at the loading area. It appears to move upwards when engaged and applies pressure to the bottom of the bullwheel.

Would I be correct in saying that this single device serves as both the servicing and emergency brake? Servicing brake when the lift just needs to stop once speed of lift has come close to a stop, and emergency when the lift needs to be stopped quickly...

[Aussierob]

You are probably looking at the bottom half of the emergency brake. Service brakes are always on the high speed shaft going into the gearbox. Emergency and rollback breakes operate directly on the bullwheel. Brakes are always located at the drive station of the lift (could be top or bottom).

[Kelly]

…Ah close but not quite.
Pretty much a given the service brake is inside the motor room.
E brake will act on both sides of flange.
E brake is very crude for stopping lift (Lift Dinosaur mentions this in the above post) but excellent for holding lift.

Links to pictures
http://www.skilifts....sary/ebrake.jpg
http://www.pomagroup.com/
http://www.pomagroup.com/Detach%20prop%20d...rive%20stations
Thanks Poma for the detailed web site.
Ryan B

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•  ebrake_from_John_for_web_A.jpg (99.95K)
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•  Poma_service_brake_motor_room_background.jpg (197.48K)
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[Tom T]

Thank again guys. Very clear explanations for a novice like myself.

[Lift Dinosaur]

Tom T, on Feb 26 2006, 06:16 PM, said:

Thank again guys. Very clear explanations for a novice like myself.

Here's a novel concept. Why don't you talk to your Lift Maintenance Manager/Supervisor/Mechanic and ask for a tour of one of your lifts? He could show you the equipment, you could ask questions, maybe have a beer afterwards. I think its called Team Building.
Good luck with your meetings.