Laziness is always due to serious reasons. Until now, I somehow did not want to sit down for calculations. It is clear that when there are formulas, everything looks serious. But at the same time, the thought that now I would have to do endless mathematical calculations, this thought frightened me. And I also had to imagine how all this is at rest. That is, when the power is off. What form is the bracelet in? Recently, I have improved the design of the actuators, but something was still missing. I didn’t want to make telescopic cylinders, as it is difficult and expensive. And the soft rubber containers obviously did not direct the force in the right direction. In the end, an idea appeared that in order for the force to go along the desired axis, it was first necessary to compress the container along this axis. The tubes for transmitting air pressure and vacuum were already coiled into springs for me, and now these springs have a clear purpose.
The bracelet will be in a tense state all the time. Simply put, everything will be on compressed springs.
The amount of effort required to move the bracelet from the “closed” state to the “open” state consists of the sum of the individual efforts of each pneumatic actuator located between the two suction cups in the direction of the circle vector plus the radial force from the center of the circle. The body of the actuator is a wavy-walled rubber container. In the free state, the shape of the container has its maximum length. When we compress the container along the desired axis to the minimum length, the undulating walls also create a springy effect.
Two adjacent suction cups are also connected by a coiled spring tube. This spring compresses the suction cups with the container between them to a minimum length. Other tubes are also used as springs, which are attached to the large storage tanks of the module. In this way, all vacuum and pressure transfer tubes are pulled together to “close” bracelet. The force required to “open” the bracelet consists of the pressure on the container walls minus the spring resistance of the tubes and plus the spring effect of the container side walls. From this value, we should also subtract the radial loads arising from stretching the glove and sleeve. And also add excess pressure inside the sleeve.
The passive resistance of all electrical cables to bending should also be taken into account.
F — part of the effort from one pneumatic actuator required to “open” the bracelet
P — force created by compressed air pressure inside the actuator
ΣT — the force of the tubes for the transmission of vacuum and pressure, working as springs “closing” the bracelet
A — spring effect of the side walls of the actuator compressed by tubes in a “closed” bracelet
ΣC — total passive mechanical resistance of cable materials
G — force required to stretch the elastic of the glove
S — force required to stretch the fabric of the sleeve cuff
Ps — overpressure inside the suit sleeve
N — the total number of actuators in the bracelet
The design of a strained bracelet is better in the sense that we do not achieve the necessary characteristics by selecting the material of each part. I can increase the rigidity of the tubes by further increasing the thickness of the container walls. These efforts are directed along opposite vectors and compensate each other. The stiffer tubes, in turn, are able to withstand high pressure or vacuum. All this contributes to the reduction in the cost of materials and the entire design in general.
https://transform-ppe.medium.com/replacing-medical-gloves-as-a-lazy-developers-problem-28dabb4b02c7
