Month: September 2015

September 28, 2015

CPI Waterproof Switch Applications for Military Vehicles.

CPI has a long history of providing switching solutions to friendly military operations in the US and across the globe. In fact our first switching solutions back in 1946 were targeted at the military aircraft of the day. Since then our line of waterproof switches, and thermal switches have found a home in light tactical vehicles, military construction vehicles and transports, avionics bays, ships, weapon systems, even submarine’s, wherever durability and reliability are paramount design considerations.

Law of diminishing returns as applied to Waterproof Switches.

One corollary to this law might be stated as follows: to get the last 20% of performance, you incur 80% of the cost in design/manufacturing. But what constitutes the last 20% of performance in a waterproof switch? Aren’t they all waterproof, stainless steel etc? Isn’t a $6 Offshore manufactured waterproof switch going to meet the requirements of most applications as long as specs are met?

After doing this for over 70 years, we can tell you that there are about as many ways to make a sealed switch as there are applications for them to go into. And that the joy of a $6 switch quickly evaporates when the EAR’s (Engineering Action Reports) start flying in from the field. At CPI we are sometimes the ones asked to diagnose and replace the engineering problems of other switch manufacturers with something that works.

Here is what we’ve found:

  1. Your double seal design needs to actually work. – When a ball or plunger switch depresses, it is the perfect opportunity for particulates to leak into the housing. Just a little bit of sand, mud or wind dust and your switch becomes all but useless. But in the CPI J4 ball switch we use a custom designed exclusion seal and our patented ball carrier that is tightly dimensioned to the plunger bore. In this proven configuration, our switch completely eliminates liquid and contaminate ingress. Your $6 switch? Not so much…
  2. News Flash: Switches on Military Vehicles Vibrate….A lot – Vibration problems are a leading cause of early switch failure. It occurs because a standard switch does not come with a specifically hardened actuator. CPI learned how to do this over decades of feedback in battlefield conditions and our hardened switch design is arguably the longest lasting and most dependable solution you will find for a given endurance rating.
  3. Many solve the hot problem, few solve the cold problem – Many switches will simply freeze up in one position or another when things get really chilly. In our qualification testing, our J4 ball switch is held in actuated position, then submerged in cold water in a -40C freeze chamber. Just before the switch completely freezes into a block ice, the switch is released. In our testing our J4 switch deactivates every time.
  4. Made in the USA – For some, the distribution of the supply chain into foreign nations of questionable economic and political stability is a non-starter. For others it’s the uncertainty of quality control and raw materials in 3rd world nations. It turns out that for many projects, the use of a 100% USA sourced product and supply chain is really worth something. We always thought so, which is why CPI has resisted for over 70 years, the temptation to move manufacturing offshore. The reliability you demand, comes from your ability to rely on us.

Other Military Applications for our Waterproof switches

  1. “Cab Down” detection on Oshkosh LTAS vehicle made for US Army. This was a variation of our J4 Plunger Switch.
  2. Hatch Door Open – our J4 ball switch is keeping US Navy personnel dry on navy ships and submarines.
  3. The Army’s Common Remotely Operated Weapon Station (CROWS) rely’s on our K1005 waterproof rocker for PON control of the sensitive targeting electronics.
  4. Army HMMWV (High Mobility Multipurpose Wheeled Vehicle) Program – The Army’s fleet of Humvee’s are used to take troops in and out of battle, and many other tactical operations. In this vehicle, both our pedal limit switch and Thermal switch are used in a thermal management design for the engine. Our switches are designed to operate completely submerged in 6 feet of water in this application.

Waterproof Switch Law of Diminishing Returns – Revisited.

I had an elderly aunt who used to say “Cheap is just another name for expensive”. Of course she was usually referring to cars, furniture, or badly baked pastries that upset her stomach but you get the idea.

And after all this discussion about why you get what you pay for in the world of waterproof switches, the final bit of irony is this… for similar offerings to our waterproof switch line from Otto, Honeywell and SquareD, CPI Switches are up to 80% less expensive in production quantities.

If you have a military vehicle application that requires waterproof or thermal switches, contact CPI today or visit www.cpi-nj.com. Let us show you how inexpensive real performance can be.

 

This content was originally posted at https://www.cpi-nj.com/blog/cpi-waterproof-switch-applications-for-military-vehicles/

September 20, 2015

Draw Wire Sensors Revisited

In ancient times when cave men were trying to measure the linear displacement of things they cleverly came up with something called a “String Pot”.  Using only stone knives and bearskins, they were able to cobble together a spool with some “string” and attach it to the object whose position was to be measured. Then with a simple potentiometer (resister) attached to a wiper, they could measure variable resistance (voltage) as an indication of position.

But as man began to walk upright, the drawbacks of string pots became apparent:  the strings broke; the spools were unreliable, they had limited accuracy, and of course the potentiometers wore out because of the contacting nature of the technology. But they were cheap to make and worked well-enough to be a tried and true technology for decades, especially in labs where environmental conditions were not a factor. It was straightforward mechanical technology. Easy to understand, easy to deploy. It required less complex electronics and signal conditioning.

What is A Draw Wire Sensor?

It turns out that String pots are really a type of draw wire sensor. This class of sensor is marked by its use of spooled wire or cable of some kind that is attached to a moving object whose linear position is to be measured.

In every area critical to durability and performance, CPI has extended the design of the class of linear transducers known as “Draw Wire Sensors” into something perfectly suited to reliable usage in extreme environments. The results are not only patented, but result in performance and durability parameters that bear little resemblance to their string pot ancestors….

  1. No string
    • Uses a stainless steel braided cable. The type of steel used (302, 304, 316) is selected for the particular application environment. Cable winding and diameter is also carefully selected for the size of the sensor, the cylinder stroke length, and the overall use case.
  2. No pot
    • In our design, the objective sensor is a Linear Variable Differential Transducer (LVDT). Immune to heat, liquid, temperature, RFI, EMI, shock, vibration….and it’s NON-CONTACTING, so it never wears out.
  1. No Sealed Volumes in the assembly
    • The CPI sensor has no sealed cavities or subassemblies. The device is immune to pressure or liquid environments because it is made entirely from precision-machined metal parts: No seals. No closed air volumes. As such it can be immersed, and mounted on the oil or gas side of the cylinder.
  1. Patented Translating Spool
    • String pots have a fixed spool and cable feed point. This is not optimal. CPI’s Linear Sensors have a patented Translating Spool. The spool moves laterally as it winds or unwinds. This means that the spool can hold more cable, more securely. In a string pot, the cable has to move over itself as it winds up. In our product, the spool moves out of the way of the cable.
  1. Patented Linear-to-Rotary-to-Linear technology
    • String pots work by turning a potentiometer with a cable spool. Many of our clients have abandoned String-Pots because “they don’t sense fast enough”. Essentially the transducer is directly tied to the rapid rotation of the spool and provides unreliable readings at higher rotational speeds. By contrast, CPI’s sensor works by reducing, via a precision micrometer thread mechanism, the long linear translation of the object to be sensed. The first reduction is to a rotary motion (the spool); then to a short, easily calibrated linear translation (the LVDT). No other linear sensing technology works like this. That’s why we have approximately 20 US and International patents granted to our linear position sensor technology.

Summary of CPI Sensor vs. String Pot

For large scale powerful hydraulics, or hydraulics deployed in heavy duty vehicles, or cylinders operating underwater, or in highly vibrational and corrosive environments, our SL series position sensor technology is arguably the only high reliability hydraulic cylinder linear position measurement solution of any technology in the world.

For more information visit us at www.cpi-nj.com.

 

 

This content was originally posted at https://www.cpi-nj.com/blog/draw-wire-sensors-revisited/