Last updated on 09/30/2019
Believe it or not, pressure switches play an integral part in the production of tires for every kind of vehicle. During the tire curing process, today’s tire presses rely on switches to be able to work safely around the clock while handling high pressure and temperature cycles. Whether they are used in a hydraulic tire curing press or within a steam system, the quality of the switches used can make or break your bottom line.
What is tire curing?
To really understand the importance of switches in tire manufacturing, you need to know the basics of tire manufacturing and tire curing in particular. There are three main steps in the tire manufacturing process: combining base materials to make the rubber, assembling the different components of the tire to create a green tire, and finally, curing.
Tire curing is the process of turning a green tire, a tire with all of its components but no tread or form, into a tire that is ready to be molded. The green tire is inserted into a tire press where an internal tire bladder is inflated causing the green tire to press up against the mold. The action of pressing up against the mold combined with intense heat causes the rubber to conform to the mold, creating the tread and sidewall lettering in the process.
During the tire curing process, the tire curing press and its components are subjected to an enormous amount of heat and pressure. Without the proper safeguards in place, conditions like excessive pressure or overpressure in the mold and the release of scalding hot steam can occur without warning. This is where pressure switches come in.
Where are pressure switches used in tire presses?
High-temperature, high-pressure steam presses utilize pressure switches in a few different areas to maximize safety and ensure proper tire curing press operation. In most steam tire presses, pressure switches are used on both the steam line and the post inflator. Here’s how they work:
- The Steam Line: As the bladder is inflating during the curing process, steam is added to increase the temperature of the rubber sandwich and the pressure inside the press. When this curing process is complete, a vacuum sucks the excess air out of the press to deflate the bladder so that the finished tire can be removed from the mold.
To control temperatures around 350 degrees Fahrenheit and pressures around 350 PSI, a pressure switch is used on the safety interlock system and steam line to protect against a premature opening of the mold while under pressure and steam during the curing cycle.
- The Post Inflator: Sometimes, after removing the tire from the press, a post-inflator is used to maintain the size and shape of the tire while it completely finishes curing. Depending on the requirements, a pressure switch is used to maintain a safe pressure inside the inflator for the remaining curing period.
How Pressure Switches Protect Tire Curing Press Operators
Pressure switches provide protection during the curing process by ensuring the safety interlock system does not prematurely open until a preset safe level of pressure is reached, typically below 10 PSI. To do this, most pressure switches use a constant rate device, like a spring-loaded piston valve, to regulate pressure. However, because the actuation mechanism is constantly moving in these types of devices, premature wear and tear can cause the switch to fail which, in turn, causes a full shutdown of the tire press.
Seeing just how large of an inconvenience such a trivial problem can cause, CCS pioneered the DUAL-SNAP® action technology utilizing Belleville disc springs to lessen premature wear and tear. With this technology, CCS pressure switches sit at rest until a preset pressure is reached while other devices are continually in motion. This provides repeatable accuracy and safe operation while ensuring a dependable lifecycle and avoiding unnecessary shutdowns.
CCS’s 6214 series of switches also come with a clean-out port to help flush the “dirty steam buildup” caused by contaminants in curing steam that will eventually clog the ports of most other pressure switches. Lastly, our 6214 Series switch also incorporates wetted parts specially designed to withstand high-pressure steam at temperatures up to 500oF.
When it comes to tire manufacturing and tire curing, in particular, the industry could not exist as it does today without pressure switches. These small, but immensely important devices monitor the pressure and control the process on a tire curing press to ensure the safe operation of the machine and the safety of workers. For more information on the CCS switches used in tire curing presses, take a look at our tire manufacturing page or contact us directly.