By Mike Barton, Managing Director, B&B Attachments
The use of hydraulic fork positions on forklift trucks is a cost-effective way of enhancing safety, reducing damage to the load and increasing efficiency.
Forklift trucks are nowadays seen more as materials handling solutions rather than a basic vehicle to handle loads, with the focus shifting from the machine to the task. Nowadays, fork positions on heavy trucks are a must as forks become near impossible to move manually at lifting capacities above 5 tonnes. Most forklift truck manufacturers offer hydraulically operated fork positioners as a standard option for trucks over 5 tonne capacity.
However, even on smaller machines fork positions make life easier for the operator. The wider the fork basis for the load, the more stable it will be during operation. However, more often than not, operators prefer to leave the forks where they are and hope that the load rests on them until the task in hand is complete. If operators are facing continual changes in entry pocket position, due to a high variation of different loads, the truck's efficiency is greatly affected when the driver has to frequently jump on and off the truck to change fork positions. Not only does this cause fatigue and increase the risks of accidents but can lead to fingers being crushed between the fork and carriage.
Health and safety boards increasingly recommend the use of hydraulic fork positions, concluding that they prevent accidents by stabilising loads and enhancing the safety of the operator and co-workers. In addition, hydraulic fork positioners also help reduce damage, enhance man-machine efficiency and reduce energy use by lessening forklift reversing.
Fork positions can feature movable carriages instead of welded forks, which allow the use of standard forklift forks. There is a huge range of different fork positioners available with a variety of features and designs.
Valve block sideshift:
In this case a hydraulic value switches cylinder control from opening and closing the forks to their parallel movement. The drawback of this, though, is that sideshift stroke is dependent on the rest-stroke of the positioning cylinders. Therefore, in completely opened and closed positions no sideshift is available.
Separate components for sideshift (sideshift cylinders) will be placed behind or in the centre of the body and displace the entire attachment. A benefit of this is that sideshift stroke is constant according to cylinder stroke and fully independent of the positioning cylinders. However additional components can impede visibility.
Forms Of Body
The number of profiles decides the resistance and strength of the attachment. The advantage of this is that the forks are properly guided, usually with inserted wear and tear profiles, but because this adds thickness and weight to the attachment, visibility can be impeded.
Bodies that guide the forks on carriages or by one or two horizontally aligned profiles do not provide enough, if any, profile overlap and resistance to allow fork spreads beyond the body width. In such a case, designs for a configuration of four profiles in horizontal or telescopic alignment are required. They also provide enough resistance for the use of stronger hydraulic cylinders with clamping forces and are therefore identical to attachment manufacturers' clamp body designs. These are able to exceed the body width and reach relatively wide fork spreads from a quite narrow basis. As a result of their clamping capability, they can also cope with spread forces or even clamp loads between forks.
Choosing Fork Positioners
The decisive factor when choosing fork positioners is their application. There are generally three categories that can be distinguished:
• Light duty: fork positioning for entering load carriers. Ideal for relatively short forks and operation within attachment's body confines. No spread forces or clamping. Suited to clean environments such as warehouse applications.
• Medium duty: fork positioning for entering load carriers. Ideal for light pushing and spread forces and operation within the attachment's body confines without clamping. Suited to normal environments such as loading/unloading applications.
• Heavy duty: fork positioning for long and wide goods. Including spread forces up to clamping, exceeding the attachment's body width. Suited for normal to dusty environments, such as mixed warehouses, pre-cast concrete plants, timber handling, etc.
Manufactures of fork positioners such as Kaup, have addressed all of these potential needs with four different types of fork positioners. Carriage based fork positioners have a sideshifting variant that positions within the frame width. This type of fork positioner provides absolutely synchronic fork movement via a chain and can be used with original forklift truck forks. Although not designed for spread forces or pushing pallet with fork it has a very low lost-load centre and therefore a high residual capacity.
Valveblock sideshift fork positioners have excellent visibility and positions forks within the frame width. Although they do not feature clamping capacity, they withstand pushing a pallet with forks on the floor etc. Other versions feature independent sideshift and positions forks within the frame. They have no clamping capacity but can withstand pushing a pallet with forks on the floor. These are usually available as a hook on version and offer a variety of features.
Clamp body designed forklift positioners can exceed clamp body width. They are designed to carry load on the forks rather than to clamp, which means strong forks for high capacity on forks and smaller cylinders to adjust forks for different pallet sizes. This therefore means lower clamping capacity between forks but faster adjusting speed compared to a clamp.
Operators are convinced that forklift sideshift allows for faster forklift operation, reduced energy and tyre consumption and less damage to the load carriers. Regardless of the loads, forklift positioners are an effective way of turning a forklift truck into a multi-talented and versatile materials handling system.