US3499134A - Encoder having pin shaped contact elements - Google Patents

Encoder having pin shaped contact elements Download PDF

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Publication number
US3499134A
US3499134A US736612A US3499134DA US3499134A US 3499134 A US3499134 A US 3499134A US 736612 A US736612 A US 736612A US 3499134D A US3499134D A US 3499134DA US 3499134 A US3499134 A US 3499134A
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US
United States
Prior art keywords
contact element
contact
contact elements
encoder
opening
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US736612A
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English (en)
Inventor
Clarence J Klosterman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Northrop Grumman Guidance and Electronics Co Inc
Original Assignee
Litton Precision Products Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Litton Precision Products Inc filed Critical Litton Precision Products Inc
Application granted granted Critical
Publication of US3499134A publication Critical patent/US3499134A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/12—Contacts characterised by the manner in which co-operating contacts engage
    • H01H1/36—Contacts characterised by the manner in which co-operating contacts engage by sliding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/60—Auxiliary means structurally associated with the switch for cleaning or lubricating contact-making surfaces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H2001/0005—Redundant contact pairs in one switch for safety reasons
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/22—Analogue/digital converters pattern-reading type

Definitions

  • the mounting block is a unitary moldable body having a number of cylindrical openings therein with a number of pin contacts movcably mounted within the openings.
  • the new structure allows easy contact element removal, eliminates contact element entrapment and provides for extended contact element life at high rotational speeds.
  • the present invention relates in general to an improved analog to digital converter and in particular to an improved pin shaped contact element and mounting block arrangement for an electrical contact apparatus such as a rotational shaft encoder.
  • the pin shaped contact elements and mounting block there disclosed comprised a two-piece block having a plurality of holes into which a plurality of elongated pin shaped contact elements were mounted.
  • the openings were structured to form a reservoir for a lubricant with the block forming contact element constraining shoulders at each end of the opening.
  • the contact elements were generally cylindrically shaped having a larger periphery along its middle portion so as to form a piston and smaller peripheries at its ends so that each of the ends cooperated with the block shoulders to position and support the pin contact elements and allow easy axial movement.
  • a biasing spring surrounded each of the pins. Roughly half of each opening was formed in each of the mating pieces of the block; during assembly the pins were mounted within one of the block pieces with the other block piece being thereafter attached usually by bonding.
  • This type of pin and mounting block assembly provided an encoder having a long life, a more easily achieved redundancy and an improved stability against wobble.
  • pin shaped contact elements have greatly improved the analog-to-digital converter art
  • manufacturing difiiculties have appeared and there remains the natural impetus to improve the product still further as well as to broaden its applications.
  • One of the major manufacturing problems was misalignment of the block halves so that a ledge was formed within the opening.
  • the ledge provided an obstruction to the spring which prevented the pin from moving freely along a path parallel to its longitudinal axis.
  • an electrical contact apparatus comprising a mounting element having an opening therein; a contact element having a first end, said contact element being mounted in said opening, and said contact element being movable in a direction parallel to its longitudinal axis; means for substantially preventing movement of said contact element in a direction transverse to the longitudinal axis of said contact element disposed about said contact element adjacent said first end, said means having a surface closely spaced from the interior of said opening; and said first end having a surface cooperating with a fluid on the moveable contact surface when there is relative motion between said end surface and said moveable contact surface to cause a force to act upon said end surface.
  • An object of the present invention is to provide a new and improved pin shaped contact element and block combination which is relatively inexpensive to manufacture, easy to repair and extremely reliable in operation.
  • Another object of the present invention is to provide a new and improved pin shaped contact element and block combination having a long, useful life when used in conjuction with corresponding contact elements moving at high speeds.
  • Still another object of the present invention is to provide a new and improved pin shaped contact element and block combination which enables convenient redundancy of the contact elements, improved contact elements stability during operation and a greater ability to electrically contact a rotating encoder code disc.
  • FIG. 1 is a simplified cross sectional view of a rotational shaft encoder provided with pin shaped contact elements of the present invention
  • FIG. 2 is an elevation view of the mounting block
  • FIG. 3 is a cross sectional side view along line 3-3 of the embodiment shown in FIG. 2, and
  • FIG. 4 is an enlarged cross sectional view of a pin shaped contact element mounted in the mounting block of FIGS. 1 and 2.
  • FIG. 1 a rotational shaft encoder generally designated 10.
  • the encoder includes a housing 12, a support member 14 threadly inserted within the housing to hold an input shaft 16, a pair of bearings 18 and an encoder code disc 20.
  • the code disc 20 is concentrically coupled to the shaft 16 so as to rotate therewith.
  • a mounting block 22 (commonly referred to as a pin cage) is attached to the housing 12 by any suitable means such as by machine screws 23; the block has a plurality of openings or recesses 25 (better seen in FIG.
  • Leads 26 connect the contact elements 24 to a plurality of terminals 28 which in turn are connected to a diode package 30 containing a plurality of blocking diodes connected to the leads 26 so as to isolate the encoder from interfering external signals.
  • the leads 26 may be connected through the diode package 30 to a corresponding plurality of external terminals 32 which extend from the encoder 10.
  • the external terminals 32 and the diode package 30 may be held in place by a support 34 which may be attached to the housing 12 by any convenient means.
  • the code disc 20 generally comprises a disc having on one face a number of annular tracks. Each track has alternating conductive and non-conductive portions with an inner track being totally conductive.
  • various of the pin shaped contact elements 24 which are connected to a source of electrical power (not shown) contact selectively the various tracks and the various conductive and non-conductive portions thereof.
  • the pin shaped contact elements 24 are so arranged that by monitoring the various signals from the contact elements the angular position of the code disc 20 and thereby the angular position of the rotating shaft 16 are known. It can be seen that the contact elements must be capable of withstanding the force tending to move them with the code disc as it rotates, i.e. the contact elements have a tendency to move in a direction transverse to their longitudinal axes, as well as have an ability to be easily moveable in a direction along their axes to adjust for any irregularities in the contacting face of the code disc.
  • the block may be made of any convenient insulative material and is preferably constructed of an initially moldable plastic material as a unitary body having a plurality of openings or recesses formed when the body is molded. Distinct advantages are achieved by a one-piece block 22 as compared to the two-piece block which was disclosed in the above mentioned application. First, only one molding operation is necessary. Second, there is no need to have a mating step in which the two pieces are aligned and bonded together. Third, there is no problem of misalignment between the two pieces causing interior ledges within the openings. Thus the unitary block is considerably cheaper to manufacture and eliminates rejects because or misalignment problems.
  • a great number of pin shaped contact elements may be accommodated in a relatively small area by being positioned generally perpendicular to the main plane of the mounting block; prior art brushes were attached by long arms mounted almost parallel to the mounting block.
  • a triple redundancy i.e. have three electrically interconnected contact elements 24 properly spaced engaging the same annular track on the code disc 20 so that if one of the contact elements should fail or momentarily not make contact with the track, it is highly probable that one of the other two contact elements will be in proper contact.
  • the contact element locations are not to be considered limiting nor should the fact that a triple redundancy configuration is illustrated; it is quite clear that a great many contact element locations are possible as are a great variety of redundancy configurations.
  • FIG. 4 there is shown an enlarged view of a portion of the mounting block 22 illustrating one of the openings or recesses 25 which is preferably cylindrical in shape having an interior surface 40.
  • the opening is restricted at one end by an annular shoulder 42 which is integral with the mounting block 22.
  • the pin shaped contact elements '24 Moveably disposed within the opening 25 is the pin shaped contact elements '24 having a generally cylindrical shape of various diameter dimensions and cooperating with the opening 25 somewhat analogous a piston.
  • a conical, protruding end 50 of the contact element is tapered to a very small area for contacting a conductive portion 51 of a track on the code disc.
  • Adjacent the end 50 is a flange 52 which has an outer cylindrical surface 53 closely spaced from the interior surface 40 of the opening 25.
  • a liquid lubricating substance Disposed within the opening 25 is a liquid lubricating substance which also serves to dampen axial movement of the pin shaped contact element 24.
  • the contact element strikes an irregular surface portion of the code disc, the contact element will be pushed temporarily into the opening 25.
  • the flange 52 will place pressure upon the liquid which will flow through the spacing 58 to an exterior surface 63 of the mounting block until the pressure is released.
  • the contact element returns to its normal position as shown the liquid will again flow through the spacing 58 back into the opening 25.
  • the spring 60 which has one end 66 abutting the flange 52 and another end 68 abutting the shoulder 42, also acts to dampen axial movement of the pin shaped contact element 24. As shown in FIG.
  • the spring 60 is slightly biased, so that when the contact element is axially moved inward the spring will be further biased to retard the inward movement and provide a force to return the contact element to its normal position.
  • Additional liquid lubricant 70 is placed upon the code disc 20 to lubricate the end 50 of the contact element and the code disc, as well as to remove any wear particles which may break away from the code disc because of the engagement made between the contact element 24 and the code disc.
  • Hydrodynamic lubrication is created by the hydrodynamic pressure built up by moving one surface relative to another where the first surface is coated with a lubricant while the other surface presents an oblique surface to the first surface and to the virtual direction of motion between the two surfaces. According to one text on the subject a wedge shaped film of lubricant is formed between the two surfaces which provides a lifting force to the oblique surface perpendicular to the direction of motion.
  • the lifting force created is a function of the relative velocity, the length and width of the oblique surface, the angle the oblique surface makes with the other surface and the minimum thickness of the lubricant film between the two surfaces.
  • the code disc is assumed to move in the direction shown by the arrow (upward direction as the embodiment is depicted in the drawing).
  • a liquid 70 is coated on the code disc and may be any suitable lubricant.
  • the oblique surface is the tapered end 50' of the pin shaped contact element 24.
  • the liquid 70 will form a wedge in the zone designated 72, which will exert a force having a component acting normal to, i.e. away from, the code disc surface. This force will counteract the bearing force of the contact element caused by the spring 60 and thereby reduce the friction generated at the area of engagement between the two surfaces.
  • a contact element which fails to engage the code disc no longer functions to supply electrical signals to indicate a shaft position.
  • a shaft may rotate at a variety of difierent speeds there may be no need to have an indication of shaft position during high speed rotation.
  • One environment in which such variable speeds are obtainable is within an aircraft tracking radar unit capable of tracking aircraft in a 360 degree sweep.
  • the radar antenna may rotate quickly through the 180 degrees to alternately scan the location of one and the other aircraft. It is necessary that the exact antenna location be determined during the time the antenna is actually receiving signals from the aircraft while it is not necessary that the exact position be known during the time that the antenna is rotating through the 180 degrees.
  • the antenna may rotate relatively slowly while it is scanning each aircraft but rotate very quickly during the transition period when the antenna is moving from one aircraft to the other.
  • the inventive encoder herein disclosed is able to function in such an environment while those encoders of the prior art would fail within a short time.
  • the pin shaped contact element 24 and mounting block 22 may have a very small physical size.
  • the mounting block 22 may be only an inch in diameter and .1 inch in depth.
  • the contact element may have a diameter for the flange surface 53 of 32 mil. while the diameter of the interior surface 40 may be 32.5 mil.
  • the distance between the flange 52 and the area of contact between the end '50 and the code disc 20 may be about 20 mil. While the taper of the end 50 may be about
  • a suitable lubricant may be any light viscosity silicon oil, suitably of a viscosity of about centipoises corresponding to approximately 50 centistokes, also corresponding to about 8 SAE, at room temperature.
  • An electrical contact apparatus comprising:
  • said first end having a surface cooperating with a fluid on a moveable contact surface when there is relative motion between said first end surface and said moveable contact surface to cause a force to act upon said first end surface.
  • said mounting element is a unitary body of insulative material.
  • said contact element has a second end opposite the first end, said second end having a periphery smaller than the internal periphery of said opening for providing passage between said opening and the exterior of said mounting element.
  • An electrical contact apparatus as claimed in claim 1 including:
  • said mounting element is a unitary body of an insulative material
  • said contact element having a second end, said second end having a periphery smaller than the internal periphery of said opening for providing passage between said opening and the exterior of said mounting element;
  • An improved electrical contact apparatus having a rotatable input shaft and an encoder disc coupled to rotate with said shaft, said encoder disc having a code pattern of electrical contacts thereon for generating information representative of the angular position of said shaft wherein the improvement comprises means cooperative with said encoder disc for deriving the position information and includes:
  • each of said first ends having a surface cooperating with a fluid and said encoder disc when there is relative motion between first end surfaces and said encoder disc to cause a force to act upon said first end surfaces.
  • each of said contact elements has a second end, said second end having a periphery smaller than the internal periphery of a corresponding opening for providing passage between said opening and the exterior of said mounting element.
  • An improved apparatus as claimed in claim 6 including:
  • each of said spring means having a first end abutting a corresponding means disposed about said contact elements, and said spring means having a second end abutting the mounting element.
  • each of said spring means having a first end abutting a corresponding means disposed about each of said contact elements and said spring means having a second end abutting the mounting element;
  • (f) means lubricating said contact elements, for removing surface wear particles, for dampening axial move-- ment of said contact elements, and cooperating with said second surfaces of each of said first ends.
  • (e) means biasing said contact elements toward mutual engagement with a force which is less than said separating force when the relative movement is above said predetermined velocity.
  • one of said pair of contact elements is an encoder disc, and the other contact element is provided with the slanted surface.
  • a contact assembly including at least one pair of cooperating contact elements operable so as to have relative motion therebetween comprising:
  • the relative motion between contact elements can increase sufficiently to cause said developed separating force to exceed said biasing force and completely separate the contact elements one from the other.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Sliding-Contact Bearings (AREA)
  • Pivots And Pivotal Connections (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
US736612A 1968-06-13 1968-06-13 Encoder having pin shaped contact elements Expired - Lifetime US3499134A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US73661268A 1968-06-13 1968-06-13

Publications (1)

Publication Number Publication Date
US3499134A true US3499134A (en) 1970-03-03

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Application Number Title Priority Date Filing Date
US736612A Expired - Lifetime US3499134A (en) 1968-06-13 1968-06-13 Encoder having pin shaped contact elements

Country Status (7)

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US (1) US3499134A (de)
BE (1) BE725413A (de)
DE (1) DE1810962C3 (de)
FR (1) FR1596046A (de)
GB (1) GB1216822A (de)
NL (1) NL158643B (de)
SE (2) SE368473B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090034108A1 (en) * 2007-02-09 2009-02-05 Fujifilm Corporation Transfer method, transfer apparatus, and recording medium

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2796472A (en) * 1956-06-12 1957-06-18 Melvin A Carter Multi-sequence switches for display devices and the like
US3030617A (en) * 1956-05-28 1962-04-17 Gen Precision Inc Analog-digital converter
US3168635A (en) * 1962-12-31 1965-02-02 Chalco Eng Corp Assembly of elements for making intermittent electrical contact
US3278715A (en) * 1965-02-03 1966-10-11 Martin S Arbonies Frictionless device for making electrical contact between moving members
US3330930A (en) * 1965-12-27 1967-07-11 F & F Entpr Inc Shorting and non-shorting switch contact constructions

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3030617A (en) * 1956-05-28 1962-04-17 Gen Precision Inc Analog-digital converter
US2796472A (en) * 1956-06-12 1957-06-18 Melvin A Carter Multi-sequence switches for display devices and the like
US3168635A (en) * 1962-12-31 1965-02-02 Chalco Eng Corp Assembly of elements for making intermittent electrical contact
US3278715A (en) * 1965-02-03 1966-10-11 Martin S Arbonies Frictionless device for making electrical contact between moving members
US3330930A (en) * 1965-12-27 1967-07-11 F & F Entpr Inc Shorting and non-shorting switch contact constructions

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090034108A1 (en) * 2007-02-09 2009-02-05 Fujifilm Corporation Transfer method, transfer apparatus, and recording medium
US7804654B2 (en) * 2007-02-09 2010-09-28 Fujifilm Corporation Transfer method, transfer apparatus, and recording medium

Also Published As

Publication number Publication date
DE1810962C3 (de) 1974-11-28
DE1810962A1 (de) 1969-12-18
FR1596046A (de) 1970-06-15
SE350670B (de) 1972-10-30
DE1810962B2 (de) 1974-04-25
NL6908665A (de) 1969-12-16
GB1216822A (en) 1970-12-23
NL158643B (nl) 1978-11-15
BE725413A (de) 1969-06-13
SE368473B (de) 1974-07-01

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