Ideas on how to open a hatch with low cost and minimum power consumption

Other Hardware Motors, Mechanics, Power and CNC
1

The project is about a box with a hatch in the bottom. I will manually fill the box and close the hatch. I just need it to open when I give a command.

The box content can become heavy, 5 to 15 kg (10 ~ 30 lbs).
There is no problem if, when command is given, it opens suddenly with gravity

I have seen some linear actuators, but it is too expensive for this project.

I was thinking about just put a rope, attach it to somewhere, and find a way to detach it. But no luck finding a way to do it.

Thanks in advance

2

Have a geared motor pull a rope attached to a pin holding the bottom closed. A low powered motor would have enough pull if sufficiently geared.

Weedpharma

3

How about a servo for an RC-plane. I've seen ones on line for less than $10. You could control it with a PWM pin.

4

Gear motor driving a threaded rod with a traveller nut.
The nut is attached to a latch.

.

5

"linear actuator" is a fancy name for fancy devices. A cheaper variant of linear actuators, with only two positions, is the simple door solenoid latch. Built exactly for keeping doors closed 'till they-re powered

6

Bolt attached to a motor with a screw ?

Some car door lock actuators work like this and can have considerable force at low cost.

http://www.ebay.co.uk/itm/Universal-Heavy-Duty-Power-Door-Lock-Actuator-Motor-2-Wire-12V-1-2-/351557182994?_trksid=p2141725.m3641.l6368

blimpyway:
. A cheaper variant of linear actuators, with only two positions, is the simple door solenoid latch. Built exactly for keeping doors closed 'till they-re powered

Unfortunately those latches jam under load

7

First design a latch that is secure but easy to open.

Then use a servo to open it.

...R

8

Robin2:
First design a latch that is secure but easy to open.

...R

Electric rim latches do exactly that.
Unfortunately they jam under load.

Not exactly cheap either.

I have done similar and the electric car locks work well , and a lot cheaper than the commercial 300 plus commercial motor locks used for multi point locking.

9

Lever held in place with fishing line. The line being tensioned lightly against a crossing peice of resistance wire, heat wire with a current to cut the line. A couple of AA cells would work if you use the right wire.

You might like to also look at the crossbow trigger mechanism invented by the Chinese 3000 years ago. Holds back a very large force but with a light trigger action.

10

Boardburner2:

First design a latch that is secure but easy to open.

Electric rim latches do exactly that.
Unfortunately they jam under load.

You are not being consistent. I specifically suggested a system that would be easy to open.

It could be that a substantial lever is needed to disengage a catch that does not itself need much movement to disengage - perhaps just 1mm or 2mm.

...R

11

I have used a store bought door latch coupled with a door actator and it was easy to implement.

Its on my loft acess hatch which weighs approx 2 Kg.

Rim latches use a sear mechanism like a gun.

They can take load but only with mechanical adventage like a lever.
That generally takes more travel than a solenoid can manage.

12

Robin2:
You are not being consistent. I specifically suggested a system that would be easy to open.

...R

Understood, that is why i suggest a door latch.

Making an easy reliable latch i found is not that easy.

13

Boardburner2:
Making an easy reliable latch i found is not that easy.

Agreed.

...R