Warner Electric has been supplying high-performance brakes and clutches to Yale Lift Trucks for many years and has become one of the company’s trusted suppliers. When developing its next generation of three-wheel trucks, Yale approached Warner Electric with a new design brief: to customise the PK-35 brake to fit within a confined space whilst providing parking and manual release braking functions to help increase manoeuvrability.
The standard PK-35 brake is used in many forklift and materials handling applications around the World. However, when developing its latest three-wheeled product, Yale Lift Trucks, a leading global manufacturer of lift trucks, requested design parameters such as packaging, heat dissipation and special manual release that required a high degree of customisation to the standard design.
Mathieu Ruault, Warner Electric Forklift and Material Handling Market Manager, comments: “The level of re-design for this project was such that the finished components were virtually 100% bespoke to the customer’s requirements. Development was extremely fast-paced to keep to the project’s short schedule; during this time we worked closely with Yale Lift Truck’s engineers to review the performance of existing brakes and incorporate a manual override function.”
As each specification was addressed, design prototypes were created to slowly build up the final solution; an enhanced brake package that would provide all the features and benefits required whilst still remaining cost-effective. The main function of the brake is to lock the traction motor shaft when the truck is parked. This is done with springs pushing against a moving armature, which clamps a friction disc linked to the motor shaft. When power is applied to the brake, a coil acts as an electromagnet to pull the moving armature and to compress the springs.
There are two motors, back-to-back, with each one linked to the front wheels of the truck - the brakes are mounted on the back of the traction motors, on the opposite side to the gearbox. The brakes had to meet specific performance requirements, as per regulations, whilst also fitting within the confined space on the end of the in-line traction motors. Warner also factored easy-removal into the design to allow for servicing without the removal of the drive unit or traction motor.
Each prototype was thoroughly tested, including extensive field testing. Warner ran life-cycle tests to simulate the brake life of the product and conducted air gap tests along with pull-in/holding tests. The testing determined the air gap limits and demonstrated that the brake would pull-in to release as required. It also factored in how temperature affected pull-in responsiveness and timing. The life-cycle test simulated a fully loaded truck travelling at certain speeds to test the dynamic braking capability and overall performance outcome of the brake assembly.
Mr Ruault continues: “The test rigs were designed to simulate different braking energies with various speeds, to be as close as possible to the application; this also allowed us to monitor the torque of the unit through the whole life of the friction disc. The brake included new features like the hand release lever and an enclosed design to prevent entry of environmental contaminants. These options existed on other forklift brakes, but were usually added at a significant cost. The redesign work challenged us to come up with a solution which allowed these features to be integrated in the easiest way possible, allowing the design to remain cost competitive compared to the old version with these options.”
The newly modified PK-35 brake is an integral component on several different series of Yale and Hyster brand 1,300 - 1,800 kg. capacity sit down counterbalance trucks. It is also being installed on a series of three-wheel stand trucks. All platforms use independent in-line drive unit motors for manoeuvrability, and are variations of 36V and 48V trucks. The new PK-35 brakes incorporate a manual override function that allows for easy vehicle towing in case the truck needs to be moved, with no need for additional tools or power sources.
As a leading manufacturer Warner Electric is able to use its own design and engineering development teams to create customer specific products, not just offer standard items for series production. It is this flexibility and pro-active engineering approach to customer requirements which parent company and world’s largest industrial brake, clutch and coupling manufacturer, Altra believes sets the brand apart from others in the market.
Picture 1: Warner Electric Brake.
Picture 2: Yale Forklift Truck.
About Warner Electric
Warner Electric offers excellent service, and delivery. Single headsets can usually be supplied from stock, with multiple units for complete machines taking 3-4 weeks on average. In addition, Warner Electric is offering headset rebuild kits, which enable customers to rebuild the magnetic headsets themselves, or the alternative of a factory repair programme, where customers ship their headsets back to the Warner Electric factory for full factory rebuilds and certification. Finally, Warner Electric provides headset exchange programmes that allow customers to receive rebuilt Warner headsets at predetermined times during the year. With this option, customers can choose the programme that best meets their needs.
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