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Explaining its Spring-Loading Mechanism - Part 2

Clk2Hm Inside the Main Body lies the heart of the Springzback, its Adjustably Compressive Differential Mechanism.  This is the complicated portion of this device, so if you’re not technically inclined, do not feel bad, as most people can’t completely wrap their minds around this, especially when trying to visualize all three functions working together, but we’ll give it a go.

As implied by its long descriptive name, this mechanism accomplishes three important, yet distinct functions.  These have been broken down into their own tabs below.  Simplified drawings are used to help illustrate the working principles.  In reality, the sizes, thread pitches, forms of springs (etc.), involved many design changes, prototypes and trials & errors to finally arrive at what the Springzback is today. Ultimately, just about every part had to be custom made in order to achieve the desired end result.

Lets begin with the differential mechanism and a simple compression spring, and then we will build upon that foundation to include the adjustment feature, and finally the actual compression feature that all work together as one integral unit.

Click on the categories (listed below) to open them up

Why is a Differential Necessary?

The Springzback’s differential function allows for free opposing leg movements, such as when walking or standing with one leg forward. Otherwise, the brace would be constantly shifting back and forth as you walked.

In addition, if one leg was in front of the other when you put your weight on the brace, that leg would take the entire load/pressure, thus causing the brace to shift over until the other leg could be reached to balance the pressure. This would not only be uncomfortable, but your chest could slide around, and off, the chest plate.

Incorporating a differential makes for a much more user friendly experience. It engages with, and divides your transferred weight equally to both legs when supporting a forward bend, thus maintaining a constant even pressure on both legs, regardless of where your legs are positioned (even during walking). This also keeps the chest plate setting steady instead of rising up and down as you walked.

How Oppositely Threaded Shafts work as a Differential

The easiest way to grasp an understanding of this mechanism is to go to a hardware store, and for a couple of bucks you can purchase a turnbuckle.

Turnbuckles are commonly used in tightening ropes, wires, cables and chains. They feature oppositely threaded bodies with eyebolts (or hooks, etc.) threading into their opposite ends.turnbuckleHaving one of these in your hands would definitely make it easier for you to follow along with the illustrations. It would be even more helpful if you could find a short sturdy compression spring to fit in-between the inner ends of the eye bolts.

If not, forget about the spring and put something solid between the ends instead. Just have something that will prevent the bolts from running out of threads and tightening in body; they need to tightened against their ends instead.

Below is a simplified cutaway drawing (these appear in the Springzback patent). If you look at Fig 1 below you will see the representation of the main body housing, two oppositely threaded shafts (#1 is LH threaded, #2 is RH threaded) and a simple compression spring #3 (for illustration only, not the form of spring that is actually used).

Figure 1 represents what the mechanism looks like while standing upright with both legs together.

differential fig 1 Now refer to Fig 2.  Keep in mind that each shaft is clamped to a leg engagement, each of which follow the movement of the leg it presses against. These will either hold or cause the shafts to rotate.

Also keep in mind that these shafts turn relative to the main body. In other words, you can look at this from two views. The first view is that the users legs move up to their chest, the other view is that their chest moves down to their legs. Either way you view this, the end result is the same. When the chest moves closer to the legs, the shafts turn/screw together to compress the spring(s). When the chest moves away from the legs, the shafts turn/screw apart and reduce the spring compression.

Now for the differential effect: In Fig 2, notice that while shaft 1 is screwing inward, shaft 2 is screwing outward (in the opposite direction).

Figure 2 represents what the mechanism looks like while the leg of shaft 1 is forward of the leg attached to shaft 2.

differential fig 2

Figure 3 represents what the mechanism looks like while the leg of shaft 2 is forward of the leg attached to shaft 1.

differential fig 3 Figures 2 & 3 illustrate what occurs when you are walking. Notice the locations of the inner end gaps (and spring) during the back and forth (walking) movements. The gaps between the shafts remain the same, they just keep chasing each other back and forth as you walk, without compressing the spring.

The spring will not get compressed until you lean forward, and then the spring is compressed accordingly, but walking will not compress it any further. This phenomenon maintains equal torque (turning force) between the two shafts, thus equal pressure against each leg.

Figure 4 represents what occurs during a bend (both shafts get turned in the same direction). Due to the opposite threads they screw together causing the spring to ultimately fully compress (bottom-out). This is what it looks like (internally) during a fully supported bend where the chest plate comes to a hard stop.
Figure 4 represents what the mechanism looks like while the legs are side by side (together), and the user is leaning all his weight on the chest plate (thus bottoming-out the spring). differential fig 4

If you’re ready for more, Click on tab #2 for the Adjustment Selection

How the Twist of a Knob lets you Select Your Ideal Support Angle

The adjustment function uses a twist knob to allow you to select the angle at which you want the chest support to begin. This doesn’t actually change the spring tension, that is fixed, what it does change is when the spring-loading begins. It may at first seem like its changing the tension, but it really does’t.

The adjustment feature is basically a threaded rod with a large knob on its outer end, and it screws through one of the Main Body’s large shaft, and effectively alters the length of the inner end of the large shaft. Screwing it inward makes the large shaft act like it grows (or screws inward), and backing it out makes it act like it gets shorter (or screws outward). Thus when the inner ends of the large shafts begin contacting (compressing) the heavy spring pack, is altered, to begin compressing at different bending angles.

In keeping with the high quality standards of the Springzback, the threaded rod engages with about one inch of threads, and it’s inner end is cupped to mate with a ball bearing, both for achieving low friction, smooth operation and long wear life.

The Dual Stage Spring-Loading Feature

The spring-loading function features two stages of compression that is encountered. The first stage uses a simple compression spring attached (inline) to one of the outer ends of the powerful (supporting) spring pack. It works with the adjustment rod in a way that protects this weaker spring from being crushed when compressing the powerful support springs (we will not go into detail on this).

This primary compression provides a slight pressure on the chest and legs engagements so that they stay in place when you are disengaged from the powerful springs. Otherwise, once you rise up and unload from the supporting springs, the chest plate would droop and the leg pads would flop around while you walked. This feature eliminates the need for straps around your chest and legs.

The powerful second stage spring-loading function provides a progressive supporting effect. This provides much more mobility as opposed to a solid stop. Because if you need to reach down slightly, you can use you stomach muscles to pull yourself further down. If you rise up a bit, the spring effect still offers you most of your support, just a little less.

In contrast, without the spring effect, you could not reach down any further than the angle you selected, you would have to re-adjust your setting to lower yourself. And when you rise up at all, you are unsupported until you return back down to the chest plate, or you need to screw the adjustment to a higher leaning angle. The spring-loading feature really increases the user friendliness.

It would have been nice if a heavy compression spring would have worked between the shafts to achieve the powerful tension and travel required, but they didn’t even come close. This application required much more strength than any compression spring (in a size that would fit inside the mainbody) could offer. The only system found that was up to this task was a large amount of spring (cupped) washers strung on a steel shaft (referred to as “Belleville Washers”).

These provided the power required, but in order to achieve the travel needed, it was necessary to bore-out the large shafts and run them inside to accommodate the six inches of stacked washers (about 80 of them).

Below is an illustration used in the Patent, it is not an accurate depiction of the current design, but it is close enough to illustrate what has just been discussed. Hopefully all of this has helped! Mainbody cutaway illustration
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trade name of a patented back brace device for relieving back strain while engaged in forward leaning, bending or lifting.