US3636782A - Indexing mechanism - Google Patents

Indexing mechanism Download PDF

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Publication number
US3636782A
US3636782A US834076A US3636782DA US3636782A US 3636782 A US3636782 A US 3636782A US 834076 A US834076 A US 834076A US 3636782D A US3636782D A US 3636782DA US 3636782 A US3636782 A US 3636782A
Authority
US
United States
Prior art keywords
pawl
ratchet wheel
lever arms
frame portion
movement
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
US834076A
Other languages
English (en)
Inventor
William B Huber
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.)
Motorola Solutions Inc
Original Assignee
Motorola 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 Motorola Inc filed Critical Motorola Inc
Application granted granted Critical
Publication of US3636782A publication Critical patent/US3636782A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • F16H31/00—Other gearings with freewheeling members or other intermittently driving members
    • F16H31/003—Step-by-step mechanisms for rotary motion
    • F16H31/005—Step-by-step mechanisms for rotary motion with pawls driven by a reciprocating or oscillating transmission member
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • 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
    • Y10T74/15—Intermittent grip type mechanical movement
    • Y10T74/1526—Oscillation or reciprocation to intermittent unidirectional motion
    • Y10T74/1553—Lever actuator
    • Y10T74/1555—Rotary driven element
    • Y10T74/1556—Multiple acting
    • 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
    • Y10T74/21—Elements
    • Y10T74/2133—Pawls and ratchets
    • 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
    • Y10T74/21—Elements
    • Y10T74/2133—Pawls and ratchets
    • Y10T74/2136—Pivoted pawls
    • Y10T74/214—Multiple tooth

Definitions

  • a pawl and ratchet device actuated by a solenoid for rotating the cam of a cartridge-type tape player to position the magnetic tape head adjacent different tracks on the tape includes a unitary plastic pawl element having an opening therein for receiving the ratchet wheel and further having first and second pawls integrally formed as part of the pawl element and attached to the sides of the opening thereof by a restricted portion forming a spring biasing the pawls into engagement with the ratchet. Surfaces are provided on opposite sides of the opening in the pawl element for engaging the ratchet wheel in the extreme positions of motion of the element in both directions to prevent further rotation of the ratchet at the limits of movement of the element.
  • the pawls are provided with only straight line linear motion, it is necessary to provide the device with a relatively large armature stroke; because the pawls must be moved through the stroke corresponding to the movement of the ratchet wheel and in addition through a further path in order to cause the pawls to be moved fully out of engagement with the ratchet wheel when the other of the pawls is causing the motion to be imparted to the wheel.
  • Pawl and ratchet mechanisms of the type described above are used in many cartridge-type tape players capable of reproducing multitrack tape. Such players use a cam and a cam follower arrangement for positioning the magnetic tape head, with the ratchet wheel being utilized to rotate the cam. It has been discovered in the use of this type of mechanism in a cartridge-type tape player that some cam surfaces, when in contact with the cam follower, cause autorotation of the cam, thereby misaligning the tape head with the track. In order to prevent such misalignment, additional locking devices for positively locking the cam into position after it has been moved from one set of tracks to another, have been provided. Such additional locking devices, however, also result in an increased cost of the positioning mechanism in such tape players.
  • a pawl and ratchet mechanism uses a double-pawl element made from a single piece of resilient material, with the element comprising a frame portion and with the pawl elements formed with and attached to the frame portion by resilient connecting webs which bias the pawl elements into engagement with the ratchet wheel.
  • Locking surfaces are provided on the frame portion on opposite sides of the ratchet wheel; so that when the pawl element is moved to either of its extreme positions, one or the other of the locking surfaces engages the ratchet wheel to prevent further rotation due to momentum of the ratchet wheel or due to autorotation of the member driven by the ratchet wheel.
  • An additional feature is to utilize the pawl and ratchet mechanism in a push-pull pawl arrangement to position the cam in the head-positioning mechanism of an eight-track recorder having four head positions, the cam having only four cam surfaces, each corresponding to a different one of the four positions to which the head is to be located.
  • each push-pull action of the pawl driving mechanism causes rotation of the cam over an arc of for each cycle of operation.
  • Another feature is to provide the ratchet teeth with a concave surface for engagement by the actuation portions of the pawl elements to improve the operation of the mechanism.
  • FIG. 1 is a top view of a tape player utilizing a push-pull double-pawl and ratchet mechanism in accordance with a preferred embodiment of this invention
  • FIG. 2 is a side elevation view of the mechanism shown in FIG. 1;
  • FIGS. 3, 4 and 5 are bottom views illustrating the operation of the pawl and ratchet mechanism shown in FIGS. 1 and 2;
  • FIG. 6 is a perspective view of a cam used in the tape player shown in FIGS. 1 and 2.
  • a-portion 10 of a cartridgetype tape player adapted to receive and play tape cartridges having multitrack tapes therein.
  • the tape player 10 includes a magnetic tape head 12 which is mounted in a head bracket 14.
  • the bracket 14 is movably mounted on a tape deck 15 by a pantograph, a portion of which includes a pair of pivot rods 17 and 18.
  • a cam follower 19 Integrally mounted with the head bracket 14 is a cam follower 19, and a spring, which is not shown, biases the pantograph and therefore the head bracket 14 and the cam follower 19 into contact with a cam 20.
  • the cam 20 has four different cam surfaces, each of which is associated with the four different sets of tracks on the magnetic tape (assuming that a standard eight-track stereo tape cartridge is to be played by the tape player 10).
  • the cam 20 in turn is mounted on a shaft 22 which is rotatably mounted on the tape deck 15.
  • the cam follower 19 moves the magnetic tape head assembly 14, and thus the head- 12, against the spring bias of the pantograph to position the magnetic tape head to a different set of tracks on the tape.
  • the tape player 10 also includes a capstan shaft 23 mounted within a capstan housing 25 that is supported by the tape deck 15.
  • a motor 27 is coupled by a drive belt 28 to a flywheel 30 which is connected to the capstan shaft 23 and drives the shaft 23 to move the magnetic tape through the cartridge and past the magnetic tape head 12.
  • a solenoid is actuated to operate a linkage for rotating the cam to position the tape head 12 to a new set of tracks on the magnetic tape.
  • this is accomplished by the operation of a solenoid 29 which is momentarily energized in a known manner upon completion of the reproduction of a pair of tracks in the player to momentarily attract and then release an armature 31 against the action of a biasing spring 32, imparting a reciprocating linear motion to the armature.
  • the solenoid 29 is deenergized, the spring 32 returns the armature 31 to the position shown in FIGS. 1 and 2.
  • a double-pawl element or mechanism 33 is attached to the end of the armature 31 and operates upon a four-toothed ratchet wheel 35, with the ratchet wheel 35 being rigidly attached to the cam 20.
  • the pawl element 33 is made of a thin piece of resilient plastic or metal material of substantially rectangular or square shape.
  • a pair of pawls 36 and 37 are integrally formed with the pawl element 33 in an opening in the center of the pawl element 33. The ratchet wheel 35 then extends into the opening and is engaged by the actuating portions of the pawls 36 and 37 which are resiliently spring-biased into contact with the ratchet wheel 35 by connecting webs 39 and 40, respectively.
  • the entire pawl element 33 is formed out of a single piece of resilient plastic material and may be formed by molding the structure in the shape most clearly seen in FIGS. 3, 4 and 5, or by cutting out the central portion of the pawl element 33 to form the pawls 36, 37 and connecting webs 39 and 40 from a solid piece of resilient plastic stock.
  • the material used to form the pawl element 33 may be of any suitable type which is relatively rigid in the hardened state with good fatigue characteristics and possessing sufficient elasticity so that the pawls 36 and 37 bear against the ratchet wheel 35.
  • the ratchet 35 carries four teeth 43, each of the teeth having a generally radially extending concave surface which is engaged by the actuating portions 41 and 49 of the respective pawl members 36 and 37 to cause rotation of the ratchet wheel 35.
  • the actuating portions 41 and 49 of the pawl members 36 and 37 are angled from the body portions of the pawl members 36 and 37 to extend the tips of the actuating portions 41 and 49 respectively into the pocket formed by the concave surfaces 44 on the teeth 43 of the ratchet wheel 35 in order to provide a positive engagement between the teeth 43 and the actuating portions 41 and 49 of the pawls.
  • the concave pawl engaging surface 44 of the teeth 43 permits positive engagement between the actuating portions 41 and 49 of the pawls with the teeth of the ratchet wheel without increasing the spring bias imparted by the webs 39 and 40 to a point where a stronger electromagnet 29 would have to be employed.
  • the rear surface 48 of the pawl element 33 operates to prevent clockwise or counterrotation of the ratchet wheel 35 since the surface 48 is in abutting relationship with the tip of the next adjacent tooth 43 on the ratchet wheel 35. If for any reason, the ratchet wheel 35 is not completely rotated through a one-half tooth gradation by the operation of the pawl 36, engagement of the rear surface 48 with the tip of the next adjacent tooth 43 tends to complete the rotation.
  • the solenoid spring 32 When the solenoid 29 is deenergized, the solenoid spring 32 returns the pawl element 33 to the rest position shown in FIG. 5. During this return movement, the actuating projection 49 of the pawl 37 engages the concave surface of a different tooth 43 on the ratchet wheel 35 to move or pull the ratchet wheel 35, and thus the cam 20, through another approximately 45 rotation in the counterclockwise direction, thereby completing the desired of rotation of the ratchet wheel 35 and cam 20.
  • a projection 51 provided on the front surface 50 of the pawl element 33 extends into the path of the next adjacent tooth of the rachet wheel 35 to further provide, or lock against, counterrotation of the ratchet wheel in a clockwise direction, since the projection 51 is located directly in the path of rotation of the next adjacent tooth 43 of the ratchet wheel 35.
  • the projection 51 pushes on the back surface of the adjacent tooth 43 to rotate the wheel 35 to the position shown in FIG. 5.
  • Each energization and subsequent deenergization of the solenoid 29 causes the pawl mechanism to operate in the manner described previously to rotate the ratchet wheel 35 and thus the cam 20 an additional 90.
  • FIG. 6 A perspective view of the cam 20 is shown in FIG. 6, and the cam includes four cam surfaces 54 to 57 located at different elevations at 90 angles from one another. Separating the cam surfaces 54 to 57 are sloped surfaces 58 for providing a relatively gradual slope for adjusting the position of the cam follower 19 from one of the surfaces 54 to 57 to another of the surfaces, upon each 90 rotation of the cam 20 by the pawl and ratchet mechanism shown in FIGS. 3 to 5.
  • the cam surfaces 54 to 57 are located at different vertical positions within relatively close tolerances.
  • an adjusting screw 60 is provided for adjusting the vertical direction of the shaft 22, as best shown in FIG. 2, after the tape player is assembled. This adjustment moves the cam 20, and the ratchet attached thereto, a small amount in the vertical direction as viewed in FIG. 2 so that proper alignment of the tape head 12 with a given track on the tape may be provided as an initial adjustment for the tape player.
  • the pawl element 33 is made relatively thin compared to the axial length of the ratchet wheel 35 so that adjustment of the ratchet wheel 35 in the vertical direction under the action of the screw 60 may be effected while the webs 39 and maintain the actuating portions of the pawls 41 and 49 in engagement with the ratchet wheel 35 in a plane substantially normal to the axis of rotation of the ratchet wheel 35 and cam 20. Because the pawls 36 and 37 and the actuating portions 41 and 49 thereof are relatively thin in comparison to the axial length of the ratchet wheel 35, substantial adjustments in the vertical direction of the ratchet wheel 35 may be effected with the pawls remaining in engagement with the ratchet wheel 35.
  • the pawl and ratchet mechanism transforms reciprocating linear motion into rotary motion by use of a double-pawl member in which the pawl elements and locking or braking surfaces all are integrally formed from a single piece of resilient plastic material.
  • the alignment of the pawl mechanism with the center of rotation of the ratchet is not critical, permitting considerable tolerance in assembling the respective components of the tape player with which the pawl mechanism is used.
  • the pawl and ratchet mechanism When the pawl and ratchet mechanism is used with a cartridge-type tape player, the pawl and ratchet cooperate to lock the cam for positioning the tape head in place once the cam has been rotated to position the tape head to a difierent set of tracks.
  • the pawl mechanism permits adjustment of the cam in elevation along its axis of rotation without interfering with the engagement of the pawl-actuating portions with the ratchet wheel.
  • the double-pawl mechanism comprises a unitary pawl element made of resilient material, said element including a frame portion, a pair of lever arms integrally and flexibly connected to the frame portion with each of the lever arms terminating in an integral pawl member resiliently biased into engagement with the ratchet wheel; and at least one locking surface on the frame portion for engaging the ratchet wheel with the pawl element being moved to a predetermined position in at least one linear direction.
  • the frame portion is formed of plastic material with an opening therein for receiving the ratchet wheel, with the lever arms terminating in the pawl members being integrally formed with the frame portion within the opening and being connected to the frame portion by an integral flexible connecting web for engaging a ratchet wheel placed within the opening, and wherein the first and second locking surfaces are formed on diametrically opposite sides of the opening in the frame portion.
  • a device for transforming reciprocating linear motion to rotary motion including in combination:
  • a ratchet wheel having a plurality of teeth, each including a convex upper surface and a concave engaging surface;
  • a pawl element made of resilient material including a frame portion and at least one pawl member integrally formed therewith and carrying an actuating portion, the actuating portion of the pawl member being resiliently biased into engagement with the ratchet wheel teeth;
  • the pawl element includes first and second pawl members integrally formed therewith and each carrying an actuating portion, with the first and second pawl members being resiliently biased into engagement with the ratchet wheel on substantially opposite sides thereof, movement of the pawl element in said first linear direction causing the actuating portion of the first pawl element to engage the concave surface of a first one of the teeth on the ratchet wheel to rotate the ratchet wheel a predetermined amount, and movement of the pawl element in a diametrically opposite direction causing the actuating portion of the second pawl element to engage the concave surface of a second one of the teeth on the ratchet wheel to move the ratchet wheel in the same direction an additional predetermined amount.
  • a double-pawl mechanism for transforming reciprocating linear motion to rotary motion of a ratchet wheel
  • the double-pawl mechanism comprises a unitary pawl element made of resilient material, said element including a frame portion, first and second connecting means, a pair of lever arms integrally and flexibly connected to the frame portion through said first and second connecting means, respectively, with each of the lever arms terminating in an integral pawl member resiliently biased toward an opening for receiving a ratchet wheel, the pawl members being located so that movement of the pawl element in one linear direction causes the pawl member on a first one of the lever arms to be located for a pulling driving engagement with said ratchet wheel through said first connecting means and the pawl member on the other one of the lever arms to be in sliding relation to said ratchet wheel for pulling of said ratchet wheel through a portion of the desired rotation, and with movement of the pawl element in a linear direction opposite to said one direction causing the pawl member on said other one of the lever arms to

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)
  • Basic Packing Technique (AREA)
  • Moving Of Heads (AREA)
  • Moving Of Head For Track Selection And Changing (AREA)
US834076A 1969-06-17 1969-06-17 Indexing mechanism Expired - Lifetime US3636782A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US83407669A 1969-06-17 1969-06-17

Publications (1)

Publication Number Publication Date
US3636782A true US3636782A (en) 1972-01-25

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Family Applications (1)

Application Number Title Priority Date Filing Date
US834076A Expired - Lifetime US3636782A (en) 1969-06-17 1969-06-17 Indexing mechanism

Country Status (4)

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US (1) US3636782A (enrdf_load_stackoverflow)
CA (1) CA946182A (enrdf_load_stackoverflow)
ES (1) ES380833A1 (enrdf_load_stackoverflow)
GB (1) GB1302072A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3839735A (en) * 1972-10-13 1974-10-01 Newell Ind Transducer head positioning device
US4125074A (en) * 1976-05-04 1978-11-14 Kabushiki Kaisha Sato Kenkyusho Feed mechanism for portable labeling machine
US4383453A (en) * 1979-12-19 1983-05-17 Contraves Ag Stepping mechanism
US4448194A (en) * 1982-02-03 1984-05-15 Ethicon, Inc. Full stroke compelling mechanism for surgical instrument with drum drive

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3839735A (en) * 1972-10-13 1974-10-01 Newell Ind Transducer head positioning device
US4125074A (en) * 1976-05-04 1978-11-14 Kabushiki Kaisha Sato Kenkyusho Feed mechanism for portable labeling machine
US4383453A (en) * 1979-12-19 1983-05-17 Contraves Ag Stepping mechanism
US4448194A (en) * 1982-02-03 1984-05-15 Ethicon, Inc. Full stroke compelling mechanism for surgical instrument with drum drive

Also Published As

Publication number Publication date
DE2029097A1 (de) 1971-04-15
ES380833A1 (es) 1972-09-16
DE2029097B2 (de) 1972-08-24
GB1302072A (enrdf_load_stackoverflow) 1973-01-04
CA946182A (en) 1974-04-30

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