The present invention relates in general to seats for materials handling vehicles and, more particularly, to materials handling vehicle seats having pivoting seat backrests which improve the comfort of vehicle operators and also improve the operators' views of elevated forks of the vehicles.
Pivoting backrests for office and dinette chairs are well known and include chairs having a variety of resilient members for enabling chair backrests to pivot relative to the chairs' seating bases in response to force applied to the backrests. The resilient members also return the chairs' backrests to neutral, resting back supporting positions when forces required for pivoting are removed. Resilient members include flat spring members made of metal, plastics, composite materials and the like, as well as pads made of elastomeric materials. The effective density of some elastomeric pads used in such chairs can be controlled by adjusting a compressive force with the amount of compressive force being used to control the amount of force required to effect movement of an associated chair member, for example the tilt of a chair as shown in U.S. Pat. Nos. 4,871,208 and 5,649,740.
Typical materials handling vehicle seats have fixed backrests that firmly support the operator during operation of the vehicles and operation of materials handling systems included on the vehicles. Unfortunately, seats having fixed seat backrests can be uncomfortable for operators when materials handling vehicles are driven over irregularities or bumps common on surfaces over which the vehicles are driven and including, for example, dock boards, joints, entries to trucks and the like. When vehicles traverse such bumps, the normally solid suspensions of the vehicles cause them to bounce and rotate so that seat backrests lurch forward, striking operators in the back if the operators' backs are close to or resting against the seat backrests. While existing seats are typically padded, repeated seat backrest impacts create discomfort and can lead to early fatigue of vehicle operators. To alleviate this discomfort, operators may assume postures leaning away from the backrests. While these postures reduce the force of seat backrest impacts, they also may lead to early operator fatigue.
Accordingly, there is a need for improved seats having pivoting backrests to attenuate the pounding action of conventional seats that occurs when a materials handling vehicle is driven over dock boards, joints and similar vehicle support surface irregularities or bumps that bounce and rotate the vehicle and the operator's seat. Such seats, and particularly their backrest pivoting mechanisms, should be of simple structure to facilitate assembly, reduce parts counts and reduce costs for the seats. Due to movement of operators within seats on materials handling vehicles during normal operation, it is possible for an operator to inadvertently place an appendage near a pivoting mechanism. Accordingly, it would be desirable to have a pivoting structure that itself protects operators from potential pinching points created by pivoting movement of the seat backrest. In the case of elastomeric pads used for seat pivoting, it is also desirable to have protective structure to prevent pad damage over time, which can otherwise be incurred by the application of force to a pivoting seat backrest that exceeds the force necessary to achieve a maximum pivot position.