Increasing Safety and Efficiency in Exit Devices
At Pivot Point, we take pride in our ability to help our customers get the most out of their fasteners. Too often, a safer and more secure fastening method means a slower or more expensive assembly process. In this challenge, our solution actually increased both the safety of the end product, as well as the ease and speed of assembly, in order to surpass customer expectations.
Developing a safer, easier-to-assemble, linkage pin
- Industry: Exit Devices/Access Controls – Security Hardware
- Processes: Manufacturing of push-pad style exit devices for use on emergency doors
- Company Background: A mainstay in public buildings for years, the OEM in this case study is a designer and manufacturer of exit devices, electronic access control solutions, and related accessories. They offer a wide range of high-quality products that require significantly less maintenance over a 30-year period while offering consistent and reliable operation in critical moments.
- Challenge: The OEM was searching for a more consistent method of assembling the internal mechanism of their main push pad product line – specifically, the assembly of the main control link to the control linkage.
- Assessment: Pivot Point met with the OEM at their facility to view the application, discuss project needs, and review the current assembly process. Being a safety critical application, it was clear that minimizing failure of the unit after installation was a top priority. Due to the high volume being assembled each year, maintaining efficiency of assembly was also critical to the OEM’s bottom line. The incumbent solution (See Figure A) consisted of a cold formed clevis pin with a head on one end, and a circumferentially machined groove on the other. The pin would be inserted through the hole of the main control link and control linkage. A special tool was used to grab a ring from the cartridge and then push the ring over the groove in the pin until it snapped into place. This method was slow and allowed for the possibility of mis-installation or failures in the field.
Retaining Rings: Good Enough…Until They Aren't
We have seen it before – while retaining rings and e-clips are a long-relied-upon solution that certainly have their place in manufacturing, they can lack the consistency that some applications require. External retaining rings are installed in a relatively shallow groove, therefore, requiring a watchful eye on each ring after it is installed, to ensure the ring is properly seated in the groove. Additionally, in some cases, assembly technicians must be careful not to overstress the ring by opening it too far during assembly - an overstressed ring may not clip into the groove properly. In this specific case, the ring was being seated into a groove that was only .020” deep, which is in accordance with the manufacturer’s specifications for a Ø3/16” pin. As one can imagine, it would be difficult for the installation technicians to determine if the ring is properly seated in such a small groove. It’s not surprising that failures would occur in the field due to improperly installed rings on a small pin like this, especially when high volumes are involved.
The Solution: SLIC Pin – Consistent and Secure Fastening
Familiar with the strengths and weaknesses of grooved clevis pins and retaining rings, Pivot Point has seen our SLIC pin (Figure B) fill the void as a viable alternative for over a decade. The SLIC Pin already has the clip built in – which we refer to as a “plunger”. The spring-loaded plunger automatically ramps down upon installation and locks into place once it has passed through the application. Pivot Point reviewed the application to ensure that the stamped bracket yielded a mating hole with good bearing surface against which the wedge can engage and retain the pin. Additionally, we noted the double-shear type application, which is ideal for SLIC Pins. The material and finish of the incumbent grooved clevis pin were easily duplicated in a SLIC pin, as both fasteners are cold formed. In addition to eliminating the concern about mis-installed clips, or clips that could fall out after years of use, the SLIC Pin also significantly increased assembly efficiency by eliminating the need for a tool during assembly. Since SLIC Pins are only about 2X the purchase price of a grooved clevis pin and clip, the reduction of risk in this application, as well as the increased efficiency, gave the SLIC Pin a clear advantage. The updated assembly, using the SLIC Pin, was subjected to, and passed, UL testing. The improved push pad assembly, now utilizing SLIC, was approved for use and is now in production.
Do you have a challenging application? Contact us – We love a challenge!
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