Sometimes a point of purchase pusher tray needs to push products that are stacked 3 or 4 products high, such as baby food or pet food. There may be 6 or 7 of these stacks being pushed in one row on a display shelf. Other times, a single column of glass bottles, potato chip bags or candy bars needs to be delicately pushed forward. A new technique used to accomplish integrates a pusher tray, a variable force spring, and a rotary damper.
For many years, the pusher tray has used the variable force spring. Vulcan pioneered this type of spring and designed many versions of springs in use all over the globe. Assuming the reader is familiar with the basic pusher tray with a variable force spring, we can discuss the newest part of this system, the rotary damper. Vulcan has experience designing springs to work with dampers. This combination can be found in automotive, consumer and industrial applications. The rotary damper is now finding its way into point of purchase trays, providing smooth acceleration for the product moving forward.
A rotary damper enables a mechanism to operate with a smooth, controlled motion. The damper is filled with a viscous fluid, such as silicone. This fluid passes through rotating vanes, providing the damping resistance. The resistance force of a rotary damper is determined by the viscosity of the fluid and the design of the rotating vanes within the device. This is all accomplished in one small device that can be incorporated into a mechanism. These devices are typically found in automotive cup holders, DVD players and copy machines.
Designing a display with both a variable force spring and a rotary damper can be a difficult balance of resistance and force. Dampers can provide resistance in a clockwise rotation, counter clockwise rotation or both.
Special care must be taken to design a spring with the correct amount of force. The damper in these displays will slow the speed of the pusher moving forward. The damper will not reduce the force, it will slow the application of the full force. As an example, an oversized spring with dampening will slowly advance a bag of potato chips to the front of the display. However, the force of the spring is still present and the pusher will slowly continue to advance. The chips can be slowly crushed as the bags are forced together until the resistance of the crushed bags matches the force of the spring. By then it could be too late for the poor chips!
Designers should be aware that dampers change resistance force based on their environment. In cold temperature applications, the damper will move slower than in room temperature and hot environments. Therefore, care must be taken to best replicate the final location of the display throughout the design process. For instance, if the display is being used in a cooler, the damper should be kept cold just up until the test is made. If possible, test the entire display in a cooler. This would result in the best design of the variable force spring and damper system.
When considering a damper for your point of purchase pusher, it is best to contact Vulcan early in your design process. A Vulcan Spring engineer can assist in testing and evaluating the entire working system to recommend a spring.Contact Us