Linear position indicator

• US 4,608,654 A
• Filed: 12/13/1983
• Issued: 08/26/1986
• Est. Priority Date: 12/13/1983
• Status: Expired due to Fees

• Current Assignee: Bendix Automation Comapny
• Original Assignee: Warner & Swasey Company
• Inventors: Schafsteller, Helmut
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US06/561,014
• Time in Patent Office: 987 Days
• Field of Search: 364/559, 364/167, 318/594, 318/599, 318/469, 318/466, 377/15, 377/17, 377/24
• US Class Current: 700/302
• CPC Class Codes: G01D 11/245 Housings for sensors

Abstract

A linear position indicating system utilizing a fixed chain (20) which engages a pinion (32) connected to a mechanical input of an encoder (26) for providing position information. Encoder (26), supported on a relatively movable cross slide (14), provides an output signal indicative of the position of crosslide (14) relative to member (12) from which it is supported. Idlers (34, 36) are provided to guide the chain (20) around pinion (32) to ensure a large contact of approximately 180°. Proximity switches (50, 52) are disposed for detecting when crosslide (14) is near its travel limits. The distance between switches (50, 52) is adjustable so they can be set at a precise separation. A counter (72) is provided for counting pulses as crosslide (14) moves between switches (50, 52). The output of counter (72) is used along with the know separation between switches (50 52) for calibrating the output of encoder (26).

Claims

1. A position indicator for indicating the relative position of two members relatively movable for a predetermined distance in a predetermined direction comprising:

a length of chain secured at both ends to one of said member to be extended to lie along said predetermined direction for said predetermined distance;

an encoder secured for movement with the other of said members, said encoder having a rotatable input shaft and including means providing output position information signals in response to rotation of the input shaft;

a sprocket, connected to said rotatable input shaft, and having peripheral teeth positioned to engage each portion of said length of chain successively to rotate said input shaft during relative movement of the two movable members in said predetermined direction.

2. A position indicator as claimed in claim 1 wherein said sprocket is positioned alongside said length of chain, and further including:

a pair of rotatable guide idlers having a periphery adapted to engage said chain positions, each of said pair of idlers disposed said sprocket along said predetermined direction, said length of chain extending around each of said idlers into corresponding intermediate spaces between each of said idlers and said sprocket, and thereafter extending around said sprocket.

3. A position indicator as claimed in claim 2 wherein:

said each portion of said length of chain engages said sprocket of approximately one half the periphery of said sprocket.

4. A position indicator as claimed in claim 1 further including:

first detecting means for detecting when said two members reach a first predetermined relative position along said predetermined direction;

second detecting means, separated from said first detecting means, for detecting when said two relatively movable members reach a second predetermined relative position along said predetermined direction.

5. A position indicator as claimed in claim 4 comprising:

adjusting means for adjusting the separation of said first detecting means and said second detecting means.

6. A position indicator as claimed in claim 4 wherein said means included in said encoder for providing output information signals produces information pulses corresponding to rotation of said input shaft and further, including:

a counter operatively connected to said encoder for counting position information pulses from said encoder;

control means for relatively moving the two movable members between the first and second positions detected by said first detecting means and said second detecting means respectively and for activating said counter as the members move between the first and second positions.

7. A position indicator for indicating relative positioning of a first member movable in a predetermined direction between two spaced apart positions on a second member, comprising:

a length of chain fixed at both ends on said second member to be extended between the two spaced apart positions generally along said predetermined direction;

an encoder attached to the first member having a rotatable mechanical input and means providing output signals which are a function of rotation of the mechanical input; and

,

a sprocket, disposed on the mechanical input of said encoder, having a periphery engaging each successive portion of said chain as said first member moves between said two positions and thereby rotating the mechanical input of said encoder as the first member moves relative to the second member.

8. A position indicator as claimed in claim 7 comprising:

a pair of guide idlers each of said guide idlers having a periphery adapted to engage said chain portions disposed alongside said chain on either side of said sprocket along said predetermined direction with a space therebetween, said chain extending to partially wrap around the periphery of one of said guide idlers and thence through said intermediate space between said one guide idler and said sprocket and passing around one half the periphery said sprocket and thence into the intermediate space between said sprocket and the other guide idler, and thereafter passing about a portion of the other guide idler to extend away generally in said predetermined direction.

9. A position indicator as claimed in claim 7 further including:

a pair of proximity switches, located on the second member in respective positions spaced apart, a predetermined distance along said predetermined direction each of said proximity switches producing a respective detector signal as the first member reaches each of said two positions along said predetermined direction at which each of said proximity switches are located.

10. A position indicator as claimed in claim 9 comprising:

microprocessor means for receiving and storing said signals from said encoder and from said pair of proximity switches and including means calculating a calibration constant, determined upon movement of the members between the positions defined by said pair of spaced apart proximity switches by comparing said encoder signals to said detector signals.

11. A position indicator for indicating the position of a cross slide movable in a predetermined direction across a carriage between two limiting positions comprising:

a length of chain attached at both ends to the carriage to be extended generally along said predetermined direction between two spaced apart points on the carriage;

an encoder attached to said cross slide having a mechanical input, including a rotatable pinion in engagement with said chain; and

,

means generating an electrical signal output from said encoder providing position information as a function of rotation of the mechanical input.

12. A position indicator as claimed in claim 11 wherein:

said means generating said electrical signal output from said encoder provides position information in pulse form;

and further including a pair of detectors disposed to sense the presence of said cross slide at two positions located between the limits of movements of said cross slide; and

a counter activated when said cross slide moves between said pair of detectors for counting the number of pulses, indicative of the distance therebetween.

13. A position indicator as claimed in claim 12 including:

means adjustably mounting said detectors whereby the position between said pair of detectors is adjustable to a precise known distance.

14. A position indicator as claimed in claim 12 comprising:

control means for causing said cross slide to move between said pair of detectors and means utilizing the encoder output pulse and the pulses counted by said counter corresponding to said distance between said pair of detectors for calibrating said encoder.