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Can any master give me some idea

  1. Oct 27, 2010 #1
    I am trying to add some linkage bar or gear mechanism to a wheelchair which can use to rise or lift the patient to the half standing position. This is to help the patient to stand up from a wheelchair by himself witount using motor or any circuit. To rise the body weight by using hand force is it possible? Can any one provide me the draft of that mechanism design?

    Thanks a lot...i am just a begineer, hoping people may share their idea to me..thanks
     
  2. jcsd
  3. Oct 28, 2010 #2

    Danger

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    Welcome to PF, Sporty.
    Your post implies to me that the patient is capable of standing up unassisted as opposed to having to be resituated in a different seat. In that case, it's a lot simpler. I would think that a slightly forward-angled scissors jack would work. A hand crank running something along the line of an old-style automotive window mechanism should provide enough mechanical advantage to achieve elevation.
     
  4. Oct 28, 2010 #3
    yes, you are right, the person on the wheelchair is able to stand up,because they are only temporaly use the wheelchair like the people suffer from the accident or elder men or women in home, due to their leg is not able or no energy to stand directly from sitting . SO wish to lift the rear seat to make it in tilt position so they can easily stand up and use walker to walk.
    I have draw the draft but i think the linkage is not good enaugh to support and lift the whole body weight by a hand push force.
    the draft link,
    http://www.fileupyours.com/view/295883/dsg.bmp [Broken]
    http://www.fileupyours.com/view/295883/55.bmp [Broken]

    And thanks for your reply , help, and your idea...i wish to make a middle complexity mechanism with small forces to rise himself or herself up
     
    Last edited by a moderator: May 5, 2017
  5. Oct 28, 2010 #4

    Danger

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    Well, Sporty... your first diagram seems to be inadequate. No offense intended, but it doesn't conform to either what you said in your post or what I would require as a handicapped person. It tilts, fair enough, but in a dump-truck manner. From my understanding of the needs involved, I would think that both the front and the rear of the seat should rise, but the latter more so.
     
  6. Oct 28, 2010 #5
    Thanks to your replied,
    because i am thinking that is the handicapped person they don't need much for tilt the seat because they are seldom leave the wheel chair for walking using walker so I only assume to design the seat for aging people. Do you have any idea or any mechcanism using gear or linkage to lift up the both front and rear seat with the rear part rise more? I hope the hydraulic is not needed. because it is heavily with pump is need. Can you share your idea to me? or show me your draft or idea or drawing, so i can instantly modified my grandmother wheel chair to comfortable stage. Thanks a lot. Hopefully by sharing your idea in here may help a lot of people in need. Thanks
     
    Last edited: Oct 28, 2010
  7. Oct 28, 2010 #6

    Danger

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    Well, if you're familiar with a "scissors jack" as is used to change tires on a lot of small cars, that is the kind of mechanism that I'm thinking of. By using longer "legs" on the back side, the whole thing should tilt forward as it rises. Although you could use an electric pack, I think that a hand-powered unit should suffice for most purposes (if the attendant, rather than the patient, is doing the cranking).
     
  8. Oct 28, 2010 #7
    ic, do you have any reference to share, i am not very familiar in scissors jack mechanism, i only know it is a cross mechanism. but i look the equipment in my father's car which used to change tires is its rise the car by using the screw thread and i think need to turn a number of time to rise it. Thanks for your idea, now i am going to search online about scissors jack mechanism, if facing any problem or doubt, i will post here, hopefully you you reply. Please, If you have anymore idea or link that can share to me, I am here to say thanks.
     
  9. Oct 31, 2010 #8
    Danger, i am thinking if using scissors jack, the person need to turn numbers of time in order to rise the seat in tilt, and the mechanism for scissors jack is we need a strong base support for the reaction force, is it?
    I am also thinking one of the equipment that the reverse turning would not affect anythings, while forward turning only will rise the things up..so we can continuous turn forward and backward in set angle range, to rise the things up, so don't need to adjust the position... i don't know what is the name of that equipment ,do you know it?
    Sorry for my bad explaination and poor english.
    If i am using above mechanism, it is no way to lower down the seat back.. so what can i do?

    I am also thinking of floor jack mechanism that use to rise the car. but i don't know well in it.
    Can you provide me some ideas, drawings or references.. Thank you Danger, and anyone interested may also provide your idea here. thanks
     
  10. Oct 31, 2010 #9
    The problem that I see is that with the weight transfer, up and forward, the rear of the wheelchair would want to raise and possibly tip over. Adding a battery, and an electrical mechanism would add some weight to the rear to make it more stable while making it easier to operate the lifting mechanism, but then would make it harder to move around the rest of the time, but so would the extra weight added by reinforcing the frame.

    My thought is that if you could use their body weight to assist them, instead of trying to lift all their weight. Perhaps instead of moving the foot pads to the side when exiting the chair, you could use some cables and pulleys to transmit that force to under their armpits, assisting them instead of lifting them. I would think it possible to maybe give them a third of their body weight in lifting assistance, for a foot or so, since the foot pads are only about 4 inches off the ground, but then when they went to step off the pads, they would want to pop up, some type of locking mechanism could prevent that. Once I find my camera, i'll draw something and post it.

    The easiest way to lift them would be with a simple lever, bent at around 90 deg(cantilever?) and rotating on a center pivot point. A threadscrew attached to the lower point, the chair seat attached to the upper. When the threadscrew was turned it would raise the seat and move it forward at the same time, you could either use arm strength to turn the threadscrew(you could even use a ballscrew to reduce friction making it easier, but that would increase cost quite a bit) or a battery powered electric motor. Either way I think you would want some type of outrigger on the front to stop the chair from wanting to tip forward, or to roll backwards.

    I am off to find my camera to post some pictures.
     
  11. Oct 31, 2010 #10
    thanks a lot jasongreat, u bring a new idea to me, but i still have a little bit blur about the foot pad, hope you can found your camera as soon as possible, may god bless you, because i am really exciting in waiting your idea and drawing..anyway thanks again.
     
  12. Nov 2, 2010 #11

    Danger

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    I agree that Jason pointed out a couple of things that I had glossed over. For some reason, I thought that simply locking the brakes would be enough to prevent the chair from moving in response to the patient relocation. It just escaped me that the chair would also want to "nose-over" due to the shifting centre of mass. I can see the underarm harness thing being a logistical nightmare, but it's certainly a valid proposal. I look forward to seeing his drawings. If I see a point that I think might be improved upon, I'll chirp up.
     
  13. Nov 3, 2010 #12
    Thanks for your help danger.
     
  14. Nov 7, 2010 #13
    Danger, you are right about the underarm harness idea, I think that using the existing arm rests would be the better solution, that way the weight of the person would be transferred to the ground, instead of supported wholey by the seat. I have a couple drawings, kind of rubeish though, but I cant find my digital camera anywhere to post them here. The easiest way I figure is to use some linear actuators similiar to http://dcactuators.com/Detail.asp?Product_ID=306.120_6118" to replace the supports of the arm rests, and set to move up and forward, a simple on/off switch on the arm rest, so it can be easily reached while seated or while standing after getting aided up so the arm rests will recede. One could possibly use a small transformer instead of a battery system, to save weight and bulk, but then you would need to make a little power station they could wheel over to and easily plug in the chair to operate it.

    I will continue my search for my camera. Sporty have you had any other ideas come to mind?
     
    Last edited by a moderator: Apr 25, 2017
  15. Nov 8, 2010 #14
    I have no idea about the linear actuator.what is its function? sorry for my limited knowledge in linear actuator. How it can support the weight of the body to ground?
    In my mind i am thinking using a gear mechanism by turning or supply a torque and rise the scissor jack. but i am worry the chair will tip over or move backward when the mass of the body is rise. and i don't know any other good mechanism beside using gear to transfer to screethread and to rise up the scissor jack , or hydraulic( i am not very sure in hydraulic mechanism ) to rise up a linkage mechanism (like floor jack..?)and the seat. Or the drawing like what i put in my few previous thread.

    Can you further explain in details or drawing because i am not very good in comprehend becaouse my english is quite poor.
    thanks you jasongreat and danger.
     
  16. Nov 15, 2010 #15
    If i am trying using a gear to drive another gear that stick on scissor jack, is it possible to drive the gear by hand to lift the scissor jack? Anyone? danger, jasongreat..? Thanks
     
  17. Nov 15, 2010 #16

    Danger

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    It certainly is. Depending upon the gear ratio, it can take very little effort.
    I have to leave for a wee while now, but I'll get back to you soon to continue this.
     
  18. Nov 15, 2010 #17
    Thanks a lot danger. May i know 1 more things ,the scissor jack is it using screw thread to turn and rise the things up? I think i have to use your idea scissor jack, that is the only way i know, thanks a lot danger.
     
  19. Nov 16, 2010 #18
    Any one, or danger, I want to ask that if I want to use rack and pinion with ratchet function install at the side of the wheelchair, may i know what mechanism i can use to connect with rack and pinion to lift up the seat with a small applied force? Please help me, Thanks a lot.
     
  20. Nov 17, 2010 #19

    Danger

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    Hmmm... that would be a bit more difficult, and I suspect counter-productive. I can't help thinking that you will still need some sort of scissors linkage to connect the seat to the chair, so using that as the motivator as well would save a lot of hassle. Track-and-roller systems such as are used to mount car windows might work, but they seem to me to be overly complicated.
    In answer to your previous question, yes... a scissors jack uses a lead-screw and follower system. The good ones actually have both left-hand and right-hand threads on opposite ends of the driveshaft, with one follower for each. That ensures an even load distribution between the front and rear legs. (That's not really a great explanation, but I'm tired and find myself somewhat at a loss for words today.)
    A linear actuator, as Jason suggested to use, is simply a lead-screw inside a tube. You can most frequently find them on the tongues of small trailers such as for boats, used to hold the thing up when it's unhitched.
    Jason's mention of the foot pads gave me another idea as well. The weight transfer problem can be alleviated by dropping the pads to the ground to use as "wheelie bars".
     
    Last edited: Nov 17, 2010
  21. Nov 17, 2010 #20
    Danger ,thanks for your reply,i also thinking in its mechanism linkage if using pinion and jack. don't have any idea come my mind, very down. some people told me that if i don't know well in balance of center of mass gravity action, don't do this design. so i try another way by letting the mass act downward too when lift. This is the situation below link.
    before,
    http://www.fileupyours.com/view/295883/untitled.bmp [Broken]
    after,
    http://www.fileupyours.com/view/295883/untitled1.bmp [Broken]
    but inside drawing the lifting mechanism is not on floor, it is an example only.
    By this i can prevent the chair move backward when lift ,is it? is it better than tilt lift the whole seat instead remain some part of it horizontal.
    But the problem now is i can't calculate out and use scissor linkage,because the seat is move forward when lift, it is not direct lift up vertically.
    I am not very understand in Track-and-roller system, how it function in wheelchair..? and i also quite worry i can't make it because as you said it is complicated.
    wheelie bars used by drop them to the rear or front ground ?
    When the person stand up, will it applied a force in backward or to tilt seat to push the wheelchair to move backward? how we can solce it?
    Thanks for you explaination and helpful idea.
     
    Last edited by a moderator: May 5, 2017
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