1 manual climbing stairs wheelchair crawling principle and the existence of the problem

Ordinary wheelchairs do not have the function of climbing stairs and crossing roadblocks, which greatly limits the range of activities of lower limb paralysis patients and elderly infants with wheelchair as a means of transport. In order to solve this problem, but also take into account the majority of our wheelchair users of the current economic capacity, crawler should not be too complicated. Tsinghua University Department of fine arts rehabilitation research center first developed a manual climbing wheelchair [2]. It is in the ordinary wheelchair to add a set of climbing stairs and drive system and drive system, that is, in the plains, but also by virtue of the power of the user's arms to the wheelchair, down the stairs. The structure of the climbing wheelchair is shown in Fig. 1, and its main feature is the addition of a set of climbing stairs consisting of parallelogram mechanism on both sides of the ordinary wheelchair. The two strands (cranks 3, 8) in each mechanism are fixed to the gears (4, 10) of the same number of teeth and are driven by the chain 7. The four cranks on both sides are mounted in the same phase, with two "legs" at each end of the connecting rod (ie climbing the stairs 9), and four "legs" forming two sets of support systems with the four wheels of the wheelchair. When shaking the handle 1, after a set of transmission mechanisms, so that the four cranks simultaneously rotate, the two sets of support system turns to the ground, and another set of support system to the top (or down) a step, until the end of a paragraph stairs. The seat and backrest of the wheelchair adjusts its inclination so that the seat is always in the horizontal position when climbing the stairs. In order to reduce the height of the wheelchair in the process of climbing stairs, increase stability and safety, whether on the stairs or down the stairs, are used "downstairs" approach, that is, on the stairs when using retreat (see Figure 2).

Figure 1 manual climbing wheelchair structure schematic diagram

Figure 2 Schematic diagram of climbing stairs

When the wheelchair is running on the ground, it is only necessary to lock the four "legs" of the auxiliary climbing stairs 9 from the ground. The transition is extremely easy. This wheelchair climb stairs work principle we can see that in the middle of the stairs to climb the stairs, the theoretical displacement curve of the wheelchair centroid is pure arc. As the size of the staircase actuator is designed according to the statistical average of the staircase staircase, the occupant should adjust the position of the wheelchair relative to the stairs from time to time in order to accommodate the staircase steps of different sizes. Climb up (below) a step before, make the big wheel close to the level of the steps on the wall. But such a frequent adjustment, no doubt increased the complexity of the operation. If the specifications of the staircase actuator can be adjusted to adapt to the changes in the size of the stairs, it will make the structure of the complex structure, this contradiction needs to be resolved, otherwise affect the practical value of climbing the wheelchair. The author by changing the type of climbing pole 9, so that manually climb the stairs wheelchair on the different stairs size has a good adaptability.

2 Improvements and effects on crawling parts

When the stairs are climbing the stairs, the position of the four "legs" of the climbing stairs 9 will vary depending on the size of the steps and the uncertainty of the occupant's operation, and the change of the landing position ) A step, it is necessary to timely adjust the position of the wheelchair relative to the steps, such as each climb (below) a step before, so that the big wheel close to the level of the step on the wall, this approach to become a climb Level steps of the standard requirements. Otherwise, the cumulative number of crawling errors accumulated, will make the next crawling failure, and even lead to wheelchair overturned. So frequent adjustment of the location, the crew will be very hard, especially for frail and lower limb paralysis patients, affecting the practical value of climbing a wheelchair.

In order to improve this situation, the author test to change the shape and size of the climbing stairs 9 as shown in Figure 3, at this time climb the stairs 9 shaped arc, bow string with a soft rubber teeth, so crawling in the middle, climb The staircase bar 9 is no longer in contact with the step plane with four ends (both sides), but with the "bowstring" of the rubber teeth in contact with the six stepped (both sides) tip (see Figure 4), the 6-point contact is very stable, Rubber teeth chew on the tip of the steps, but also has a strong friction. In this way, when climbing the stairs, you do not have to adjust the wheelchair frequently, simplifying the operation. When you crawl other paragraphs, you can also operate normally.

Figure 3 The shape of the new climb stairs 9

Figure 4 to install a new climbing stairs when climbing stairs action diagram

The material of the bow string can be selected with the same stainless steel tube as the climbing staircase 9, with a diameter of 40 mm, both of which are connected by welding. With rubber teeth, the material can be selected natural rubber, made of the same diameter and the diameter of the bow and the same length of the mouth with the mouth, tooth type jagged, tooth height of 10mm, when the bow string welding, and then set up, The adhesive is then bonded with an opening. Wheelchair supplier