Lift vehicle with fail-safe overload protective system
US4068773A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 3, 1975 |
| Grant date | Jan 17, 1978 |
| Priority date | — |
| Expiry date | Apr 3, 1995 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB66F17/003
- WIPO fieldHandling
- WIPO sectorMechanical engineering
Abstract
An overload protective system continuously monitors the forward overturning moment on a counterbalanced lift truck and prevents further raising of the carriage or further forward tilting of the mast when the overturning moment is excessive. Resistance strain gage sensors mounted on a load carrying tilt jack pin which resists the overturning moment are connected in an electrical bridge which may be inherently unbalanced due to the weight of the unloaded carriage and derives a strain signal proportional to the mechanical strain in the load carrying anchor pin when the carriage supports a load; a high gain differential amplifier raises the level of the strain signal output from the bridge and unbalance compensating adjustment means permit selective variation of the potential difference between the inputs to the differential amplifier until its output voltage is substantially zero to thereby compensate for unbalance in the bridge when the carriage is unloaded; a visual indicator is lighted when the differential amplifier output voltage is substantially zero to thereby indicate that bridge unbalance is compensated for; a comparator derives a trip signal when the differential amplifier o…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.