Hydraulic cylinder with position encoder
First Claim
1. An actuator having a cylinder and a piston assembly moveable within said cylinder, said piston assembly including a piston rod projecting from said cylinder and having a surface that presents to a predetermined location on said cylinder a varying discernible characteristic as said surface moves relative to said cylinder, and a sensor assembly to monitor said varying discernible characteristic and to measure changes therein to provide an indication of movement of said piston assembly relative to said cylinder, said varying discernible characteristic being provided by an interface on said piston assembly exhibiting a change in said discernible characteristic and defined by a helical groove having oppositely directed convergent flanks inclined to the direction of travel of the rod and defining a series of peaks, said sensor assembly including three transducers circumferentially spaced about said piston rod and positioned relative to one another such that when one of said transducers is aligned with one of said series of peaks, a pair of said transducers are aligned with respective ones of said convergent flanks, the distance between said interface and each of said transducers varying progressively and continuously as said piston assembly moves relative to said cylinder, said pair of transducers providing a pair of phase shifted signals as said piston moves past said sensor assembly, a function of said pair of phase shifted signals providing said indication of movement.
3 Assignments
0 Petitions
Accused Products
Abstract
An actuator has a position encoder provided by a helical groove formed in the piston rod. The groove is filled with a material of different magnetic characteristics to provide a smooth exterior surface and a varying discernible signal as the rod moves relative to the cylinder. An array of Hall effect sensors is provided around the rod to provide phase shifted signals as the rod moves so that the signal of one sensor may be correlated by the signals of other sensors.
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Citations
13 Claims
- 1. An actuator having a cylinder and a piston assembly moveable within said cylinder, said piston assembly including a piston rod projecting from said cylinder and having a surface that presents to a predetermined location on said cylinder a varying discernible characteristic as said surface moves relative to said cylinder, and a sensor assembly to monitor said varying discernible characteristic and to measure changes therein to provide an indication of movement of said piston assembly relative to said cylinder, said varying discernible characteristic being provided by an interface on said piston assembly exhibiting a change in said discernible characteristic and defined by a helical groove having oppositely directed convergent flanks inclined to the direction of travel of the rod and defining a series of peaks, said sensor assembly including three transducers circumferentially spaced about said piston rod and positioned relative to one another such that when one of said transducers is aligned with one of said series of peaks, a pair of said transducers are aligned with respective ones of said convergent flanks, the distance between said interface and each of said transducers varying progressively and continuously as said piston assembly moves relative to said cylinder, said pair of transducers providing a pair of phase shifted signals as said piston moves past said sensor assembly, a function of said pair of phase shifted signals providing said indication of movement.
Specification