Pentalift Blog - February 2020
What are lift table electric toe sensors and how do they work?
February 28, 2020, 2:55 pm - Electric toe sensors are most commonly used on lift tables that are installed in a preformed recessed pit. In a recessed pit installation there is the potential for introducing a shear hazard as the platform lowers into the pit. Electric toe sensors are an interlocked 4 sided bar assembly that is suspended under the lower edge of the lift table platform. The suspended perimeter bar assembly interacts with 4 limit switches, one per corner. When the down button is activated the electrical signal to lower the platform travels from the controller through the 4 limit switches to the power unit lowering valve. During the lift table descent if any obstruction such as an operator’s foot, debris etc. contacts the suspended perimeter bar a minimum of 1 of the limit switches will immediately open circuit. This open circuit breaks the electric signal that travels from the controller to the power unit lowering valve; this broken signal stops the lift table descent immediately. When the operators foot is retracted or the debris removed the lift table now returns to normal operation.
Can you load and unload dock lifts from the side?
February 24, 2020, 8:24 am - Yes you can. With the dock lift in the lowered position there is no issue. However if the dock lift is to be loaded or unloaded from the side in the raised position the dock lift capacity rating must be carefully selected to avoid platform deflection and premature wear. Dock lifts are generally loaded and unloaded from the ends. The weight moves on and off the dock lift platform travelling with the length of the scissor legs. When dock lifts are loaded and unloaded from the side the weight travels across the width of the scissor legs. Travelling across the width of the scissor legs is not as supportive as travelling with the length of the scissor legs. Dock lifts have 3 capacity ratings; lifting capacity, end edge load capacity and side edge load capacity. Edge loads are similar to a point load. For example a 6,000 lb capacity rated dock lift will safely lift an evenly distributed 6,000 lb. The same dock lift has an end edge load rating of 4,800 lbs lbs and a side edge load rating of 3,780 lbs. If the application requires side loading in the raised position it is recommended to contact a Pentalift sales representative to discuss and select the appropriate dock lift capacity rating to address side loading.
Why are there limitations on lift table power units hydraulic hose length?
February 14, 2020, 9:35 am - Most lift table manufacturers recommend a maximum hydraulic hose length for remote/external power units that should not be exceeded for satisfactory performance. The issue is not raising the lift table; a pressurized hydraulic hose of almost any practical length will raise the lift table, the issue is lowering the lift table. If the lift table is lowered with weight on the platform the weight will assist in pushing the hydraulic oil back through the hydraulic hose to the reservoir. If the lift table is lowered with no weight on the platform only the empty weight of the lift table pushes the oil back to the reservoir. If the hydraulic hose length exceeds the manufacturer’s recommendation there can be too much resistance in the hydraulic system resulting in very slow or even no lowering. A combination of an empty lift table and excessively long hydraulic hose does not have the force to push the hydraulic oil back to the reservoir.
What is a Vertical Storing Dock Leveler Float Zone?
February 10, 2020, 8:16 am - Conventional hydraulic dock levelers are powered up and the hydraulic lip extends, when the push button is released it is gravity down until the extended lip rests on the truck bed ready for use. During loading/unloading it is common for the truck bed to move up and down this is referred to as “float”. Vertical storing dock levelers are powered up and powered down. On the downward travel approximately 24” above the finished floor level a limit switch activates and releases the controlled descent. The dock leveler with the lip extended now softly lowers until the lip contacts the truck bed. The dock leveler is now free to float up and down during loading/unloading. The float zone is the point that the lowering dock leveler switches from powered descent to gravity descent.