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Electric truck having elevated load potential energy recovery with means to adjust rate of carriage descent

  • US 3,947,744 A
  • Filed: 10/21/1974
  • Issued: 03/30/1976
  • Est. Priority Date: 10/21/1974
  • Status: Expired due to Term
First Claim
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1. In combination with an electric lift truck energized from an electric battery to supply pressurized fluid to a lift ram which elevates a load supporting carriage, an energy recovery system for converting the kinetic energy of said elevated carriage into battery charging current comprisinga fluid motor,means for directing fluid exhausted from said lift ram through said fluid motor when said carriage is descending,unidirectional current generating means for charging said battery including a rotatable generator driven by said fluid motor and having a field winding, andmeans for selectively controlling the rate of descent of said carriage comprising transistor means for energizing said field winding to regeneratively brake said rotatable generator and said fluid motor which drives it during descent of said carriage and means for selectively varying the base drive of said transistor means to thereby regulate field excitation and the degree of regenerative braking.

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