Two of the most common linkage designs are Z-bar and parallel linkage, which is common on tool carriers. "The tool carriers are of varying designs and each contributes in its own way to try to make visibility a priority," says Pooley. Z-bar has visible constraints to the use of attachments and it is harder to see the equipment. This is why manufacturers offer a parallel linkage design on most of their loaders.
But there are new designs emerging. "Many manufacturers are moving toward a linkage that provides more visibility and versatility in one design — high breakout force and parallel lift," says Tullo. "However, many manufacturers may achieve one aspect but lessen another."
For example, a manufacturer might incorporate parallel lift, but hinder visibility with the attachment bracket or linkage design. "Volvo designed its linkage with the whole system in mind from the attachments to the OEM attachment bracket," Tullo states. "This design philosophy leads to high breakout force, parallel lift and excellent visibility to all attachments, including buckets, brooms and, most importantly, fork tines."
Komatsu has reduced the cross section of its linkage components to improve visibility. "For fork applications, visibility is crucial in the center of the machine," says Gidaspow. "For bucket applications, visibility is crucial on the bucket corners."
Caterpillar also emphasizes the importance of linkage design. "Recently, we redesigned our IT38G Series II for increased visibility," says DesVeaux. "By evaluating component placement and rerouting our hydraulic lines, we were able to substantially increase the viewing area from this integrated tool carrier."