Achieving near silent hydraulics operation for mobile forklift

In order to ensure the machine's operation could be as silent as possible a key area of focus was the gear pump. With Bosch Rexroth already supplying hydrostatic drives and gear pumps across the vast majority of Hiab Moffett's Truck Mounted Forklifts, Kevin Turnbull, Engineering Director, approached Craig Grant, Mobile Applications Manager at Bosch Rexroth, to see if the company could provide a solution.

Speaking about Hiab Moffett's decision to develop a near silent Truck Mounted Forklift, Kevin says: "There has been a trend in recent years, where deliveries are not just to typical building sites or industrial estates, but also to residential areas. With this increased move towards more residential areas, operators need to be aware of lower noise emission thresholds, particularly at night or in the early morning when most supermarket deliveries take place. Because of this we were seeing increasing demand for quieter fork lift trucks, and took it upon ourselves to develop a near silent version for those customers where keeping noise pollution to a minimum is a top priority."

Speaking about the project, Craig says: "Having worked with Hiab Moffett for a number of years, we knew that noise pollution was becoming an increasing concern for the company's customer base. While there was a product on the market that professed to reduce noise emissions, it hadn't been specifically developed for mobile applications. Fortunately, when Hiab Moffett approached us we had just brought a product to market that, as well as meeting its demands for an electrically powered pump, operated with near silent hydraulic functions."

Developed specifically for mobile applications, and forklift trucks in particular, the Rexroth Silence Plus Gear Pump was highly commended in the Noise Abatement Society awards 2011, and provides a more robust bespoke design for use on moving vehicles.

To demonstrate noise reduction potential of the new pump, Craig provided sound files of a traditional gear pump running at 1500rpm across different pressures alongside the company's silence pump and the latest silence plus pump.

Reduction in pump vibration

Describing how the new Silence Plus Gear Pump is able to reduce operational noise Craig says: "In a traditional external gear pump there is a single point non-continuous contact between the tooth and the groove, which results in pulsation of the fluid and it is this pulsation that causes much of the vibration that results in high operating noise. The reason we are able to reduce operation noise by an average of 15dBA is that the Silence Plus Gear Pump features a round tooth profile, which allows fluid to flow continuously, as a result of permanent tooth contact. The reduction in pump vibration, which is typically as much as 75 per cent, also reduces vibration in other components in the hydraulic system, which means it can make a significant impact on the noise of the machine as a whole."

In order to ensure the new gear pump was up to the challenge of a mobile application, Bosch Rexroth added its own patented wear-free axial force compensation technology to improve longevity.

Speaking about the decision to choose Bosch Rexroth as the preferred partner for its new vehicle development programme, Kevin says: "Having used and specified hydraulic pumps for a number of years, I had become used to the fact that they have a relatively high operating noise. While we used a supplier in the past who supplied a helical pump, its functionality wasn't optimised for use on forklifts. Once Craig demonstrated the noise reduction capabilities of Bosch Rexroth's latest pump, along with its increased functionality and durability, it was a simple decision for us to work with the company."

Since the initial stages of the project, Bosch Rexroth engineers have worked in collaboration with Hiab Moffett to create a working prototype which has since been awarded its own highly commended award from the Noise Abatement Society in 2012. Following on from the award success, the world's first virtually silent Truck Mounted Electric Forklift is now in pre-production.

Craig concludes: "We pride ourselves on our ability to work alongside customers to provide the right technological solutions for them and their customers. Our noise reduction project with Hiab Moffett is a great example of this collaborative approach and we know that for them our engineering expertise and support are as important as our product portfolio."

To find out more about Bosch Rexroth and the Silence Plus Gear Pump visit www.boschrexroth.co.uk.