US3662614A - Fine-coarse drive mechanism - Google Patents

Fine-coarse drive mechanism Download PDF

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US3662614A
US3662614A US97799A US3662614DA US3662614A US 3662614 A US3662614 A US 3662614A US 97799 A US97799 A US 97799A US 3662614D A US3662614D A US 3662614DA US 3662614 A US3662614 A US 3662614A
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drive
fine
coarse
driven
driven system
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US97799A
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John Quilty
Photon Inc
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UNITEX Inc
Photon Inc
Indian Head National Bank
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Assigned to INDIAN HEAD NATIONAL BANK, ONE INDIAN HEAD PLAZA, NASHUA, NH 03060 reassignment INDIAN HEAD NATIONAL BANK, ONE INDIAN HEAD PLAZA, NASHUA, NH 03060 ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: UNITEX INC.
Assigned to UNITEX, INC. reassignment UNITEX, INC. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ITEK CORPORATION A DE CORP
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05G—CONTROL DEVICES OR SYSTEMS INSOFAR AS CHARACTERISED BY MECHANICAL FEATURES ONLY
    • G05G23/00—Means for ensuring the correct positioning of parts of control mechanisms, e.g. for taking-up play
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H35/00—Gearings or mechanisms with other special functional features
    • F16H35/08—Gearings or mechanisms with other special functional features for adjustment of members on moving parts from a stationary place
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05G—CONTROL DEVICES OR SYSTEMS INSOFAR AS CHARACTERISED BY MECHANICAL FEATURES ONLY
    • G05G2700/00—Control mechanisms or elements therefor applying a mechanical movement
    • G05G2700/02—Means for regulating or adjusting control mechanisms, e.g. devices for automatic adjustment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/19555—Varying speed ratio
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/1956—Adjustable
    • Y10T74/19565—Relative movable axes
    • Y10T74/19575—Automatic control

Definitions

  • the driven shaft is part of a system which integrates the afore-mentioned rotational and axial motions in order to rapidly and accurately move and position a rack through a wide range of drive increments which is afforded by the presence of the coarse and fine drives.
  • SHEET 1 [IF 2 INVENTOR JOHN QUILTY ATTORNEY FINE-COARSE DRIVE MECHANISM BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
  • This invention pertains to a novel means for combining coarse and fine drive motions to obtain rapid drive speed while retaining accurate fine positioning.
  • the invention may be employed to drive any equipment which must be moved rapidly, and then stopped with instantaneous accuracy, in an incremental, continuous manner.
  • the foregoing objective is attained in the present invention by utilizing a fine drive stage which minimizes the interaction and inertia loading between it and the coarse revolution stage, while providing the capability of large drive increment differences between the coarse and fine drives.
  • FIG. 1 is a sectional view taken through the drive system showing the inventive drive arrangements
  • FIG. 2 is a partial sectional view of the fine drive portion of the positioning system.
  • FIG. 3 is a modification which employs the same inventive principles.
  • the coarse drive section consists of a motor with a helical gear 12 on its shaft 13 which drives a second helical gear 14 that is pinned to the output shaft 16. Attached to one end of this output shaft is the output gear (or pinion) 18, which in turn drives rack 19, which may be a carriage or the like.
  • gear 14, shaft 16 and gear 18 may be hereinafter referred to as the first driven system, while rack 19 may be hereinafter referred to as the second driven system.
  • the first driven system is adapted to integrate the rotational and axial motion imparted to it by the coarse and fine drives, respectively, such that both coarse and fine incremental movement is possible in order to rapidly and accurately position the second driven system.
  • the fine drive section can be best understood by referring to FIG. 2.
  • the fine drive motor 20 turns the cam 22 attached to its shaft 24, cam 22 moves shaft 16 containing helical gear 14 and output gear 18 in and out along its axis.
  • the axial motion of helical gear 14 on output shaft 16 causes gear 14 to rotate due to its angular mesh with helical gear 12 on the coarse motor shaft 13, which is assumed stationary for explanation purposes. If a 45 helical gear set is used, the axial displacement of output shaft 16 causes the output shaft to rotate through an angle (0 in radians) equal to the axial displacement divided by the pitch radius of the helical gear.
  • This fine movement of output shaft 16 turns the output pinion or gear 18 providing accurate final positioning of a driven device 19 such as a carriage.
  • Cam 22 may be of symmetrical design which turns on either side of a 0 position, or it can be a undirectional type which returns to 0 after I revolution. In either case its total incremental range of movement must be able to rotate the output gear through the equivalent of the coarse drive step angle (in other words, is equal to a single incremental movement of the coarse drive) to permit continuous positioning capability.
  • the fine cam follower 26 as shown is prevented from rotating by the use of cam follower box 28, but guide pins, rails, slots, or many other methods can be used to accomplish the same result.
  • the positive action of this box cam follower permits high speed position changes without bounce or overshoot.
  • the boxed cam follower can be replaced by a spring 30 added to the system to load the output shaft 16 against the cam 22.
  • the cam spring 30 shown in FIG. 2 is used to take up any minor backlash that might develop from long term wear of the cam or follower.
  • the pair of helical gears shown in FIG. 1 may be replaced with standard spur gears, in which case the output gear and its driven rack or gear would be changed to a helical pitch. If this were done, the same drive action would result.
  • FIG. 3 An alternate design which uses the same inventive drive principles is shown in FIG. 3.
  • the line drive cam 40 provides axial motion to the helical output gear 42 on the coarse motor shaft 44.
  • Gear 42 is keyed or splined at 43 to motor shaft 44, and is mounted on a sleeve member 45 which is adapted to slidably fit over the splined portion 43 of shaft 44, which allows gear 42 to move axially on the shaft without rotating.
  • axial motion of the helical gear causes the helical rack (or helical driven gear) 46 to move through the fine drive increment as previously described.
  • gear 42, splined portion 43 and sleeve member 4 may be referred to as the first driven system, and rack 46 as the second driven system.
  • a coarse-fine drive mechanism comprising:
  • a coarse drive adapted to incrementally impart motion to a first driven system
  • a fine drive also adapted to incrementally impart motion to said first driven system
  • said coarse drive connected to said first driven system such that said drive imparts only rotational motion to said first driven system
  • said fine drive connected to said first driven system in such a manner that said drive imparts only axial or linear motion to said first driven system
  • said first driven system adapted to integrate said rotational and axial motion imparted thereto whereby said first driven system is capable of both coarse and fine incremental movement in order to rapidly and accurately drive and position a second driven system.
  • said coarse drive comprises a stepping motor having an output shaft with a drive gear mounted thereon,
  • said first driven system includes a shaft having mounted thereon a gear positioned so as to mesh with, and be driven by, said drive gear, and
  • said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned in operative association with an end of said driven shaft such that when the cam is rotated by said fine drive output shaft, said driven shaft is moved along its axis.
  • said coarse drive comprises a stepping motor having an output shaft mounted thereon,
  • said first driven system includes a driven gear which is integrally keyed or splined to said coarse drive output shaft such that actuation of said shaft rotates said driven gear, said driven gear being mounted on a sleeve member which is adapted to slidably fit over said splined portion of the first driven system, and
  • said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned adjacent to an end of said sleeve member such that when the cam is rotated by said fine drive output shaft, said driven gear is moved along its axis.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)

Abstract

A pair of stepping motors form the basis of a coarse-fine drive mechanism. A coarse stepping motor imparts rotational motion through a drive gear to a driven shaft, and a fine stepping motor imparts linear or axial motion to the same shaft by means of a cam. The driven shaft is part of a system which integrates the afore-mentioned rotational and axial motions in order to rapidly and accurately move and position a rack through a wide range of drive increments which is afforded by the presence of the coarse and fine drives.

Description

United States Patent Quilty [54] FINE-COARSE DRIVE MECHANISM John Quilty, c/o Photon, Inc,, 355 Middlesex Ave., Wilmington, Mass. 01887 [22] Filed: Dec. 14,1970
[2]] Appl.No.: 97,799
[72] Inventor:
[30] Foreign Application Priority Data Dec 15, 1969 Great Britain ..6l,089/69 [52] U.S. Cl... ..74/393, 74/398 [51] Int. Cl F16h 35/02, Fl6h 35/06 [58] Field of Search ..74/398, 396, 393
[56] References Cited UNITED STATES PATENTS 1,813,997 7/1931 Himes ..74/398 [4 1 May 16, 1972 3,473,410 10/1969 Kraft ..74/396 X Primary ExaminerLeonard H. Gen'n Attorney-William D. OReilly 57 ABSTRACT A pair of stepping motors form the basis of a coarse-fine drive mechanism. A coarse stepping motor imparts rotational motion through a drive gear to a driven shaft, and a fine stepping motor imparts linear or axial motion to the same shaft by means of a cam. The driven shaft is part of a system which integrates the afore-mentioned rotational and axial motions in order to rapidly and accurately move and position a rack through a wide range of drive increments which is afforded by the presence of the coarse and fine drives.
5 Claims, 3 Drawing Figures PmNTEnnmamz 3.662.614
SHEET 1 [IF 2 INVENTOR JOHN QUILTY ATTORNEY FINE-COARSE DRIVE MECHANISM BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION This invention pertains to a novel means for combining coarse and fine drive motions to obtain rapid drive speed while retaining accurate fine positioning. The invention may be employed to drive any equipment which must be moved rapidly, and then stopped with instantaneous accuracy, in an incremental, continuous manner.
In the past numerous arrangements have been used to move and position a carriage or other mass as quickly and accurately as possible. Typically these mechanisms include multiple solenoids, clutches and'brakes, escapements of various kinds, and the use of standard differential drives used in conjunction with servo or stepping motors. All the above were tried in an effort to find an accurate high speed positioning system but each was found to be unsuitable for one or more of the following reasons: insufficient drive speed, poor positional accuracy, large backlash due to numerous gear meshes in the drive train, excessive carriage bounce or overshoot causing relatively long settling time at the desired position, or interaction between the coarse and fine portions of the drive system which caused excessive wear or inaccuracy. In order to achieve maximum speed and minimum settling time between given positions, it is desirable, but not necessary, to make both coarse and fine positional corrections simultaneously.
It is therefore the object of this invention to provide a high speed coarse-fine drive system which eliminates undesirable interaction of the coarse and fine drive motions, and reduces the bounce and settling time of the driven mass, while retaining precise positional accuracy. The foregoing objective is attained in the present invention by utilizing a fine drive stage which minimizes the interaction and inertia loading between it and the coarse revolution stage, while providing the capability of large drive increment differences between the coarse and fine drives.
The characteristic features and purposes of the present invention will be obvious from the accompanying drawings and the following description of the invention.
In describing the details of the invention, reference will be made to the accompanying drawings in which:
FIG. 1 is a sectional view taken through the drive system showing the inventive drive arrangements;
FIG. 2 is a partial sectional view of the fine drive portion of the positioning system; and
FIG. 3 is a modification which employs the same inventive principles.
DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, the coarse drive section consists of a motor with a helical gear 12 on its shaft 13 which drives a second helical gear 14 that is pinned to the output shaft 16. Attached to one end of this output shaft is the output gear (or pinion) 18, which in turn drives rack 19, which may be a carriage or the like. When the fine drive section is not operating, it is the above coarse drive system that provides the rapid large incremental drive motion to the output gear 18. Gear 14, shaft 16 and gear 18 may be hereinafter referred to as the first driven system, while rack 19 may be hereinafter referred to as the second driven system. The first driven system is adapted to integrate the rotational and axial motion imparted to it by the coarse and fine drives, respectively, such that both coarse and fine incremental movement is possible in order to rapidly and accurately position the second driven system.
The fine drive section can be best understood by referring to FIG. 2. When the fine drive motor 20 turns the cam 22 attached to its shaft 24, cam 22 moves shaft 16 containing helical gear 14 and output gear 18 in and out along its axis. The axial motion of helical gear 14 on output shaft 16 causes gear 14 to rotate due to its angular mesh with helical gear 12 on the coarse motor shaft 13, which is assumed stationary for explanation purposes. If a 45 helical gear set is used, the axial displacement of output shaft 16 causes the output shaft to rotate through an angle (0 in radians) equal to the axial displacement divided by the pitch radius of the helical gear. This fine movement of output shaft 16 turns the output pinion or gear 18 providing accurate final positioning of a driven device 19 such as a carriage.
Cam 22 may be of symmetrical design which turns on either side of a 0 position, or it can be a undirectional type which returns to 0 after I revolution. In either case its total incremental range of movement must be able to rotate the output gear through the equivalent of the coarse drive step angle (in other words, is equal to a single incremental movement of the coarse drive) to permit continuous positioning capability.
The fine cam follower 26 as shown is prevented from rotating by the use of cam follower box 28, but guide pins, rails, slots, or many other methods can be used to accomplish the same result. The positive action of this box cam follower permits high speed position changes without bounce or overshoot. However, where lower speeds are involved, the boxed cam follower can be replaced by a spring 30 added to the system to load the output shaft 16 against the cam 22. The cam spring 30 shown in FIG. 2 is used to take up any minor backlash that might develop from long term wear of the cam or follower.
As may be readily seen the pair of helical gears shown in FIG. 1 may be replaced with standard spur gears, in which case the output gear and its driven rack or gear would be changed to a helical pitch. If this were done, the same drive action would result.
An alternate design which uses the same inventive drive principles is shown in FIG. 3. In this adaptation the line drive cam 40 provides axial motion to the helical output gear 42 on the coarse motor shaft 44. Gear 42 is keyed or splined at 43 to motor shaft 44, and is mounted on a sleeve member 45 which is adapted to slidably fit over the splined portion 43 of shaft 44, which allows gear 42 to move axially on the shaft without rotating. With the coarse motor shaft fixed, axial motion of the helical gear causes the helical rack (or helical driven gear) 46 to move through the fine drive increment as previously described. In the embodiment of FIG. 3, gear 42, splined portion 43 and sleeve member 4 may be referred to as the first driven system, and rack 46 as the second driven system.
Due to low inertia loading and minimum backlash of these drive systems it is possible and desirable, although not necessary, to move both the coarse and fine sections at the same time, thereby obtaining maximum speed without undesirable bounce or overshoot. Previously, when standard differentials were used to mix coarse and fine motions, the cumulative backlash of the many gear meshes required for large drive ratios as well as interaction of both drives when operated together caused excessive bounce. Also, the combined inertia of the drive train limited the maximum speed attainable.
Although only two specific applications of the invention are shown in this disclosure, it should be understood that the particular embodiments disclosed have been selected to facilitate explanation of the invention rather than to limit the number of embodiments which it may assume. Further it should be understood that various modifications and adaptations may be applied to the specific embodiments described without departing from the spirit or scope of the present invention.
What is claimed is:
l. A coarse-fine drive mechanism comprising:
a coarse drive adapted to incrementally impart motion to a first driven system,
a fine drive also adapted to incrementally impart motion to said first driven system,
said coarse drive connected to said first driven system such that said drive imparts only rotational motion to said first driven system,
said fine drive connected to said first driven system in such a manner that said drive imparts only axial or linear motion to said first driven system,
said first driven system adapted to integrate said rotational and axial motion imparted thereto whereby said first driven system is capable of both coarse and fine incremental movement in order to rapidly and accurately drive and position a second driven system.
2. The drive mechanism of claim 1 in which:
said coarse drive comprises a stepping motor having an output shaft with a drive gear mounted thereon,
said first driven system includes a shaft having mounted thereon a gear positioned so as to mesh with, and be driven by, said drive gear, and
said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned in operative association with an end of said driven shaft such that when the cam is rotated by said fine drive output shaft, said driven shaft is moved along its axis.
3. The drive mechanism of claim 1 in which:
said coarse drive comprises a stepping motor having an output shaft mounted thereon,
said first driven system includes a driven gear which is integrally keyed or splined to said coarse drive output shaft such that actuation of said shaft rotates said driven gear, said driven gear being mounted on a sleeve member which is adapted to slidably fit over said splined portion of the first driven system, and
said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned adjacent to an end of said sleeve member such that when the cam is rotated by said fine drive output shaft, said driven gear is moved along its axis.
4. The drive mechanism of claim 1 wherein said coarse drive and said fine drive are adapted to drive said first driven system simultaneously.
5. The drive system of claim 1 in which the total incremental range of movement of said fine drive is equal to a single incremental movement of said coarse drive.

Claims (5)

1. A coarse-fine drive mechanism comprising: a coarse drive adapted to incrementally impart motion to a first driven system, a fine drive also adapted to incrementally impart motion to said first driven system, said coarse drive connected to said first driven system such that said drive imparts only rotational motion to said first driven system, said fine drive connected to said first driven system in such a manner that said drive imparts only axial or linear motion to said first driven system, said first driven system adapted to integrate said rotational and axial motion imparted thereto whereby said first driven system is capable of both coarse and fine incremental movement in order to rapidly and accurately drive and position a second driven system.
2. The drive mechanism of claim 1 in which: said coarse drive comprises a stepping motor having an output shaft with a drive gear mounted thereon, said first driven system includes a shaft having mounted thereon a gear positioned so as to mesh with, and be driven by, said drive gear, and said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned in operative association with an end of said driven shaft such that when the cam is rotated by said fine drive output shaft, said driven shaft is moved along its axis.
3. The drive mechanism of claim 1 in which: said coarse drive comprises a stepping motor having an output shaft mounted thereon, said first driven system includes a driven gear which is integrally keyed or splined to said coarse drive output shaft such that actuation of said shaft rotates said driven gear, said driven gear being mounted on a sleeve member which is adapted to slidably fit over said splined portion of the first driven system, and said fine drive comprises a stepping motor having an output shaft with a cam mounted thereon, said cam being positioned adjacent to an end of said sleeve member such that when the cam is rotated by said fine drive output shaft, said driven gear is moved along its axis.
4. The drive mechanism of claim 1 wherein said coarse drive and said fine drive are adapted to drive said first driven system simultaneously.
5. The drive system of claim 1 in which the total incremental range of movement of said fine drive is equal to a single incremental movement of said coarse drive.
US97799A 1969-12-15 1970-12-14 Fine-coarse drive mechanism Expired - Lifetime US3662614A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1813997A (en) * 1928-08-22 1931-07-14 Westinghouse Electric & Mfg Co Worm-gear reduction mechanisms
US3473410A (en) * 1966-12-30 1969-10-21 Zimmer Johannes Repeat transmission

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1813997A (en) * 1928-08-22 1931-07-14 Westinghouse Electric & Mfg Co Worm-gear reduction mechanisms
US3473410A (en) * 1966-12-30 1969-10-21 Zimmer Johannes Repeat transmission

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