Dual-Directional Locking mechanism for precision motion controlBlind

in Mechanical Engineering held by Sami-n
Contest Closed
Description:
--Short Summary--

Design and model an addition of a secondary dual-directional locking mechanism for maintaining a platform’s slope angle in an event of a high spike/impact load of a minimum 40Nm in a miniature space. (Length: 90mm, Width: 33mm, Height 40mm).


--Detailed Description--

The goal of this design is to maintain a platform at a user-defined slope angle given random and frequent scheduled loads/disturbances. The current design includes a worm gear set to provide some degree of holding torque (for example 2Nm) which is sufficient for loads such as a person standing on one end of the platform. However, in cases of high impact load such as a person jumping on the tip of the platform, a secondary mechanical locking mechanism (both directions) is required to prevent the platform from moving. Note that the space constraint will likely be the main challenge for this project.

The task is to add the mechanism to the existing model while staying within the given space (box). The strict dimensions of the enclosure box including the current BOM items are:

-Length: 90mm
-Width: 33mm
-Height 40mm

We currently have a working version that uses a secondary motor to engage and disengage a custom dog-clutch-like mechanism. However, due to the high added cost and space, we would like to further explore a purely mechanical design. That being said, we are open to ideas that use minimal power (100-200mA at 5V or 50-100mA at 12V), are very compact and reliable, and are cost efficient.

Please note that the user in our experiment will frequently signal the platform, that will signal the motor to precisely change the platform’s slope angle. Therefore, the dual-directional locking mechanism should not interfere with the motor’s operation when there isn’t an overload. This means the mechanism should either:

1) Stay disengaged on idle mode and only engage when a load higher than ~2Nm is experienced/detected

2) Stay engaged on idle mode and immediately (i.e. milliseconds) disengage when the motor starts rotating

Other innovative ideas that would achieve the goal are more than welcome.

Feel free to add components such as gears, clutches, shafts, linkages, torque limiters, brakes, springs, pawl sets, etc., or other parts/mechanism that you see fit while staying within the enclosure space and minimizing cost. You may also add features (extrude, cut, etc.) to the interior of the enclosure box and make reasonable modifications to the existing shafts and gears (e.g. remove the hub from the gear if you have to).

Preference will be given to off-the-shelf torque rated components that are compiled with other parts to achieve the dual-directional locking, rather than multiple complex custom-made parts.

Please provide a 3D model of your concept with an explanation of how the design functions to meet the project’s goal. Also, include the names of the additional components used in the model.

SolidWorks is preferred but it is okay to use another software given a clear presentation of the concept.
Wants:
Functionality – The design concept achieves the dual-directional locking of the platform in an event of an overload, and mechanically disengages post overload.

Size – The design concept does not exceed the given enclosure space (preference will be given to the most compact design)

Cost – The additional cost of the design is minimal.

Precision – The platform does not slope more than 2 degrees in an event of an overload before the locking mechanism is engaged, and after dis-engagement.

Strength – The design can withstand an impact load of up to a minimum of 40Nm

Reliability – The mechanism should not fail to engage for impact loads that occur in a fraction of a second and will be a reliable and maintenance free assembly in line w/ other components’ lifecycles.
Don't Wants:
Use of a secondary motor to achieve desired outcome - due to power and cost limitations.

Manual locking/unlocking - the system has to be fully automated.
Software:
  1. SolidWorks

Entries

#13 Dual Directional Locking Mechanism (Seatbelt Autolock Inspired) by RamaKD
This mechanism concept is based on the car seat belt auto-locking mechanism that utilizes the principle of centrifugal force. the design is simple, only need a little modification to the platform shaft, and add 3 more components which are the teeth, the internal gear, and the bolts and nuts as the cam. The assembly utilizes bolts and nuts that makes It easy to be disassembled for maintenance.
more
Oct 27, 2019 20:36
#12 Locking mechanism by Mahbub
Concept design provided. Thanks
more
Oct 27, 2019 20:11
#11 Dual-Directional Locking Mechanism for Precision Motion Control v1a Vit G by Vit Gean
Locking functionality explained in more detail.
more
Oct 15, 2019 13:47
#10 Zero backlash, high locking-torque mechanism. by Abhinav
I have used a similar system which is common in industrial applications like robotic arms and conveyors where self-locking is critical and can't be achieved by simple worm gear. The novelty of the mechanism is that it ensures virtually zero backlash from the output to input and gives a high locking force-as per my calculation it will be enough for your case. After analyzing several mechanisms, I conclude this is the way to go.
There is still some work to be done to make it prototype-ready. If you have any qualms about how it works, please contact back.
more
Oct 14, 2019 17:38
#9 Dual-Directional Locking Mechanism for Precision Motion Control v1 Vit G by Vit Gean
Oct 14, 2019 12:11
#8 Tilting mechanism by Ahmad Taufiq
I think wormgear has selfbreak mechanism because it can be moved by rotating the gear wheel. I assume that the main problem of the design is the strength of the gear wheel which is only 1Nm. This is my design. I hope you like it.
more
Oct 7, 2019 3:02
#7 Concept drawings by MCell1
Hi Sami,
I'd like to discuss two ideas, please see concepts attached.
They need some polishing but the principles are useful
Best,
Cell
more
Oct 6, 2019 22:02
#6 Torque Control by Sava
I made something which if is not useful for the goal, maybe can be useful for some other similar purposes. I hope that it will be interesting for you.
more
Oct 6, 2019 15:50
#5 Dual Direction Mechanical Locking by DesignLab
Please check and give your feedback or concern.
Thanks.
more
Oct 4, 2019 18:14
#4 Mechanism concept by Domagoj Groznica
In this concept it was used spindle to adjust angle of platform. Spindle is self-locking so it wasn't need any additional system for maintaining slope angle. Since it is trapezoidal spindle, it has very high load capacity. Available space is really well used. Also, because it is using lever, system can withstand higher loads.
This is just initial concept, so if You like it, I can continue product development.
more
Oct 2, 2019 21:59
#3 Dual Direction Locking mechanism by Concadd
Space is a constraint as you have mentioned in your description.
The maximum load of 40Nm is also difficult to achieve as the motor voltage is restricted to 12V and smaller the motor lesser the torque.
Introducing a worm wheel gear box in this assembly is a problem as the the table cannot freely rotate.
Anyway here is a concept design , please check it out.
more
Oct 1, 2019 1:23
#2 locking mechanism by egeo
Hello,
the solution I send you is a system that uses a mechanical brake, this is just an idea, if you are interested I can continue with a definitive project.
good day
Theodoro
more
Sep 30, 2019 20:56

Discussion

Tue, 15 Oct 2019 20:03:42 +0000
Hey Sami,
can we remove the worm gear and use a different way to change the platform inclination using the same motor all the while staying within the dimensional limits. Also in the new design can the motor be located inside the enclosure itself.
Thanks.
Wed, 09 Oct 2019 13:07:49 +0000
Hello Sami.

I would like to ask what happens to the platform if the load applied is less than 40Nm.... Does it remain in it's position or does the platform tilt at any load less than 40Nm

Ahmad Taufiq

Designer

Tue, 08 Oct 2019 09:38:26 +0000
Please check my design, thanks

DesignLab

Designer

Fri, 04 Oct 2019 18:15:54 +0000
Please check my entry, Thanks.

DesignLab

Designer

Fri, 04 Oct 2019 07:05:00 +0000
Working on it.
Mon, 30 Sep 2019 22:11:25 +0000
Hi Sami,
Thanks for your quick response. I am asking about speed and adjustment resolution in order to see if my design will work. It requires a minimum speed from the motor. Thank you,
Brett

Sami-n

Buyer

Mon, 30 Sep 2019 17:10:18 +0000
Hi Prepo, the motor operation is not a part of this project, rather a locking/braking mechanism to maintain the slope for a 40+Nm loads. The motor is only considered for proper and timely disengagement of the mechanism.
Mon, 30 Sep 2019 00:58:11 +0000
What is the speed at which the motor runs when making adjustments? And what is the smallest adjustment that It will make (1 degree? or is there no minimum?)?

Sava

Designer

Sun, 29 Sep 2019 08:54:47 +0000
I may not have correctly understood the condition of the task, but the only goal here can be to prevent the motor from overloading.

Sava

Designer

Sun, 29 Sep 2019 08:42:56 +0000
I also think that the platform cannot tilt in any direction if the motor does not rotate. With the motor stopped, it is more likely to break something, but not to change the slope of the platform, no matter how much load it has on it.

Sava

Designer

Sun, 29 Sep 2019 06:54:28 +0000
I have an idea for how the solution could look like, but as far as I can see, the loads are too big for such a small thing. The torque ratio T1/T2 = 1/40 - so, if T1=2 Nm, T2=80 Nm and the axial force on the worm gear will be 80 Nm/0,010 m=8000 N which is 800 kg. And if T1=40 Nm we get for axial force 160 000 N (16 t). Really strange.

DesignLab

Designer

Sun, 29 Sep 2019 05:06:38 +0000
Please don't close this job before it's timeline.

sherifelsheikh

Designer

Sat, 28 Sep 2019 21:51:06 +0000
Hello Sami-n
Is this unit part of Combined Mechanism or stand alone unit?

Sami-n

Buyer

Sat, 28 Sep 2019 21:13:44 +0000
Hi Ghufran, you may only edit the 8mm shaft connected to the platform. Nothing outside of the enclosure box can be modified.
Sat, 28 Sep 2019 20:55:29 +0000
can i use the full bottom face of platform to attach stuff?

Sami-n

Buyer

Sat, 28 Sep 2019 17:12:57 +0000
Hi Sava, You're right. Please only refer to the torque values.

Sava

Designer

Sat, 28 Sep 2019 14:22:42 +0000
Aaah, it is the torque of the motor may be.

Sava

Designer

Sat, 28 Sep 2019 14:14:27 +0000
If a person about 750 N (75 kg) is standing on one end of the platform the torque will be 750*0,0625=46,875 Nm?

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