US3432695A

US3432695A - Intermittent motion devices

Info

Publication number: US3432695A
Application number: US585397A
Authority: US
Inventors: John C Sims Jr
Original assignee: Mohawk Data Sciences Corp
Current assignee: Momentum Systems Corp; Mohawk Systems Corp
Priority date: 1966-10-10
Filing date: 1966-10-10
Publication date: 1969-03-11
Anticipated expiration: 1986-03-11

Description

March 11, 1969 J. c. SIMS, JR 3,432,695

INTERMITTENT MOTION DEVICES Fil ed Oct 10, 1966 Q a INVENTOR JOHN C. 9M8, JR.

f -ATTORNEY United States Patent Oflice Patented Mar. 11, 1969 9 Claims In the present invention, intermittent mechanical output motions are produced under the control of electrical signals to provide incrementing mechanisms having a broad range of uses such as feeding paper one or more lines at a time to a printing device.

Numerous mechanical and electromechanical devices are available which produce intermittent or stepping motions, such as ratchet devices, wrap spring clutches, and stepping motors. These devices, however, are generally expensive when designed for precise, rapid operation with minimum actuating power. In contrast, the inventive devices provide these desirable characteristics while remaining relatively inexpensive and uncomplicated.

The preferred embodiment of the invention develops a cyclic output motion for a number of cycles which depends upon the time between an actuating signal and a terminating signal. According to the preferred embodiment of the invention, a flexible member is arranged for movement between two positions, one of which impedes or interrupts the motion of a rotatably-driven member at one or more predetermined angular positions, and the other of which permits continuous rotation of the driven member. The position of the flexible member is controlled by a magnetic element which is movable between two magnetic circuits, one corresponding to the motion-impeding position of the flexible member and the other corresponding to the motion-permitting position. The magnetic circuits serve to alternately latch the flexible member in its two positions, the position switching when the appropriate magnetic circuit is released. That is, the magnetic element is held in one position by one magnetic circuit until the circuit is release-d, then the element moves to the other position where it is held by the other magnetic circuit until that circuit is released, whereupon the element returns to the first magnetic circuit. This action alternately moves the flexible member between the motion-impeding position to the motionpermitting position.

The magnetic circuitry comprises a permanent magnetic field, two pairs of pole pieces, and an electromagnetic releasing coil for each pair of pole pieces. When a coil is actuated, a local magnetic field is established in opposition to the permanent magnetic field in the associated pole pieces. As the coils are alternately actuated, the magnetic element associated with the flexible member is switched between the pairs of pole pieces.

While magnetic forces alone are adequate to provide the bistable switching action, in the preferred embodiment of the invention at least a portion of the flexible member is cocked (flexed) in opposition to its instantaneous position to accelerate the switching action. When the flexible member is placed in the motion-impeding position to interrupt (stop) the rotatable member, the rotatable member causes a cocking force to be applied to the flexible member in a direction toward its other (mo tion-permitting) position. Thus, when the flexible mem ber is to be switched by actuating the appropriate release coil, the cocking force accelerates the action and the flexible member is moved rapidly to the continuous-mo tion position. As the rotatable member moves away from its interrupted position, the cocking force is removed and the flexible member is oppositely cocked to accelerate the return action. This opposite cocking force is dependent upon the configuration of the components: the flexible member is quiescently positioned (without considering the effect of the permanent magnetic field or the cocking force provided by the rotating member) toward the motion-impeding position. Thus, the flexible member is always cocked in a direction to aid the next switching action: quiescently cocked when in the motion-permitting position, and mechanically cocked (by the rotatable member) when in the motion-impeding position.

It is thus a primary object of the present invention to provide improved intermittent motion devices wherein one or more cyclic motions are developed under the control of applied signals.

Another object is to provide improved intermittent motion devices where operation is controlled by magnetic forces.

A further object is to provide improved intermittent motion devices employing flexible members which controllably interrupt a cyclically-driven element, wherein the control is magnetically effected.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawmgs.

In the drawings:

FIGURE 1 is an isometric drawing showing the preferred embodiment of the invention with the rotatable members removed.

FIGURES 2, 3 and 4 are isometric drawings showing a portion of the device shown in FIGURE 1 in conjunction with the rotatable member in the various modes of operation: in FIGURE 2, the rotatable member is impeded from motion; in FIGURE 3, the rotatable member is free to move; and in FIGURE 4, the rotatable member is about to be impeded.

As shown in FIG. 1, a flexible member 2 consisting of spring steel or other suitable material is shaped with two outer prongs 4 and an inner prong 6. The ends of the outer prongs 4 are connected together by a strip 8 of the flexible member. In effect, the flexible member is essentially rectangular in appearance with a U-shaped portion removed to define the center prong 6.

A magnetic element 10 is rigidly affixed to the strip 8 by an adhesive or, alternatively, by extending and shaping the strip 8 to surround the magnetic element.

The flexible member 2 is rigidly mounted between two permanent magnets 12 which are contained between two pole pieces 14. The permanent magnets 12 are preferably ceramic with high silicon steel pole pieces. The pole pieces 14 extend to form a lower pair of pole elements 16 and an upper pair of pole elements 18, where the pairs of pole elements are arranged to permit a magnetic circuit to be completed when the magnetic element 10 is between the lower pole elements 16 as shown or between the upper pole elements 18.

The flexible member 2 is quiescently biased toward the lower pole elements 16. That is, in the absence of magnets 12, the flexible member assumes the position shown in FIG. 1. However, the magnetic forces exceed the quiescent bias to enable the magnetic element 10 to remain in contact with the upper pole elements 18 when the element is thus positioned. Thus, the permanent

magnetic structure

10, 12, 14, 16, 18 functions as a bistable device or latch, where the movable member 10 can be held in either its lower or upper position.

A demagnetizing coil 20 is mounted on one lower pole element 16 and another coil 16 is mounted on one upper pole element 18. These coils are selectively actuated to develop electromagnetic forces between the pole elements that are in opposition to the forces developed by the permanent magnets 12. In this manner, the magnetic element can be alternately switched between its lower and upper positions by alternately pulsing the coils 20. When the appropriate coil is pulsed, the corresponding magnetic circuit is neutralized and the magnetic element is moved by the attraction of the opposite pole elements to its alternative position. High speed operation is provided by the magnetic structure because the pole elements are demagnetized locally without demagnetizing the entire structure. While only one coil 20 is used for each pair of pole elements, separate coils can be placed on each pole element if desired.

The magnetic structure shown in FIG. 1 is used in conjunction with a cyclically driven mechanism to provide an intermittent motion device which controllably executes one or more cycles of operation. As shown in FIGS. 2, 3 and 4, a disk or drum shaped rotatable member 22 containing a radially-extending element 24 is mounted on a shaft 26. The shaft is continuously driven in a clockwise direction by an essentially constant rotational force, such as provided by a slip clutch or other suitable mechanism (not shown). The resulting interrupted motion of the rotatable member 22 and shaft 26 is derived from the shaft and applied to a utilization device (not shown), such as the paper feed mechanism of a printer.

FIGS. 2, 3 and 4 show the positions of the elements in several phases of the operating cycle.

In FIG. 2., the mechanism is shown in its motioninterrupted position, where movement of the rotatable member 22 is impeded because the extension 24 is contacting the edge of the strip 8 and the magnetic element 10. The center prong 6 of the flexible member 2 is forced upward by the extension 24. However, the tension on the flexible member caused by flexing the prong is more than offset by the magnetic force which holds the magnetic element 10 against the lower pole elements 16.

When one or more cycles of operation are to be initiated, a pulse is applied to the coil 20 (FIG. 1) on the lower pole elements to counteract the permanent magnetic field in the lower magnetic circuit. At this time, the combined forces of the upwardly-flexed prong 6 and the upper magnetic circuit (between pole elements 18) cause the magnetic element 10 to rapidly move to its upward position. As show in FIG. 3, the extension 24 is no longer blocked and the rotatable member 22 moves in the clockwise direction. While the flexed prong 6 is not essential to operation, its use in the preferred embodiment of the invention provides enhanced operating speed and reliability.

The rotatable element 22 continuously turns during the time that the magnetic element 10 is latched in its upward position. During the last desired revolution, interruption of the rotatable element is anticipated by moving the magnetic element 10 to its lower position, as shown in FIG. 4. This is accomplished by pulsing the upper demagnetizing coil 20 (FIG. 1) to release the upper magnetic circuit. At this time, the combined forces of the upwardly flexed outer prongs 4 and the magnetic attraction of the lower pole elements 16 return the magnetic element 10 to its lower position. The rotatable element 22 is then stopped when its extension 24 contacts the edge of the strip 8 and the magnetic element 10, in the position shown in FIG. 2.

The design of the mechanism can be simplified for use in environments where the same intermittent movement is infiexibly required, such as in conjunction with a paper feed mechanism which operates one line at a time and is not capable of slewing the paper several lines at a time. In this restricted environment, the upper pole elements 18 and their demagnetizing coil 20' are not required. When the mechanism is to provide its cycle of operation, the coil 20 is pulsed on the lower (and only) pole elements 16 and the magnetic element 10 moves upward under the force applied by the flexed prong 6. The

rotatable element 22 is then no longer impeded from motion. As soon as the extension 24 passes under the strip 8 and the magnetic element 10, the magnetic element returns to the lower position and the motion of the rotatable element 22 is interrupted at the end of one revolution.

In the preferred embodiment of the invention, only one extension 24 is provided on the rotatable element 22 but, obviously, additional extensions can be spaced around the circumference of the rotatable element. Furthermore, the extensions need not extend radially, but can be formed on a side of the rotatable element. As another obvious modification, the rotatable element need not be disk or drum shaped, but may merely comprise one or more radial extensions from the shaft.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An intermittent motion device comprising, in combination:

a rotatable member upon which a rotational force is applied; the member containing at least one rotationinterrupting portion;

control means capable of assuming a motion-impeding position wherein the rotation-interrupting portion of the rotatable member is engaged by the control means, and capable of assuming a motion-permitting position when the rotation-interrupting portion of the rotatable member is not engaged by the control means;

the control means comprising a flexible member which is cocked by the rotation-interrupting portion of the rotatable member when the control means is in the motion-impeding position to exert a force on the control means toward the motion-permitting position, and a magnetic element which controls the position of the control means;

means for establishing a fixed magnetic field to attract the magnetic element for providing a force on the control means toward its motion-impeding position, said force exceeding the cocking force;

and means for selectively establishing a temporary magnetic field in opposition to the fixed magnetic field for counteracting the fixed magnetic field, enabling the cocking force to move the control means toward its motion-permitting position.

2. The device described in claim 1, wherein the rotatable member is generally circular with a segment having a greater radius to form the rotation-interrupting portion.

3. The device described in claim 2, wherein the control means comprises a three-pronged flexible member arranged tangentially to the rotatable member, the outer two prongs extending beyond the center prong and supporting the magnetic member, the center prong coacting with the rotation-interrupting segment of the rotatable member to provide the cocking force in a direction away from the rotatable member, and the magnetic member coactable with the leading edge of the rotation-interrupting segment to impede motion of the rotatable member.

4. The device described in claim 1, further comprising a second fixed magnetic field to attract the magnetic element for providing a force on the control means toward its motion-permitting portion and a second selectivelyestablished temporary magnetic field to counteract the second fixed magnetic field, whereby the control means is maintained in its motion-permitting position until the counteracting second temporary magnetic field is established.

5. The device described in claim 3, further comprising a second fixed magnetic field to attract the magnetic element for providing a force on the control means toward its motion-permitting portion and a second selectivelyestablished temporary magnetic field to counteract the second fixed magnetic field, whereby the control means is maintained at its motion-permitting position until the counteracting second temporary magnetic field is established.

6. The device described in claim 1, wherein the fixed magnetic field is provided by a permanent magnet and wherein the selectively-established magnetic field is pro vided by an electromagnet.

7. The device described in claim 4, wherein the fixed magnetic fields are provided by a permanent magnet and wherein the selectively-established magnetic fields are provided by electromagnets.

8. The device described in claim 6, wherein the fixed magnetic field is developed across a pair of pole pieces, around at least one of which is mounted a counteracting electromagnet.

9. The device described in claim 7, wherein the fixed magnetic fields developed across pairs of pole pieces, around at least one of each pair of pole pieces is mounted a counteracting electromagnet.

References Cited UNITED STATES PATENTS 3,343,112 9/1967 Schulze 335- X 2,170,316 8/1939 Zenner 335-266 XR 2,794,157 5/1957 Chisholm 317- 3,349,356 10/1967 Shinohara 335-254 MILTON O. HIRSHFIELD, Primary Examiner. B. A. REYNOLDS, Assistant Examiner.

US. Cl. X.R.

Claims

1. AN INTERMITTENT MOTION DEVICE COMPRISING, IN COMBINATION: A ROTATABLE MEMBER UPON WHICH A ROTATIONAL FORCE IS APPLIED; THE MEMBER CONTAINING AT LEAST ONE ROTATIONINTERRUPTING PORTION; CONTROL MEANS CAPABLE OF ASSUMING A MOTION-IMPEDING POSITION WHEREIN THE ROTATION-INTERRUPTING PORTION OF THE ROTATABLE MEMBER IS ENGAGED BY THE CONTROL MEANS, AND CAPABLE OF ASSUMING A MOTION-PERMITTING POSITION WHEN THE ROTATION-INTERRUPTING PORTION OF THE ROTATABLE MEMBER IS NOT ENGAGED BY THE CONTROL MEANS; THE CONTROL MEANS COMPRISING A FLEXIBLE MEMBER WHICH IS COCKED BY THE ROTATION-INTERRUPTING PORTION OF THE ROTATABLE MEMBER WHEN THE CONTROL MEANS IS IN THE MOTION-IMPEDING POSITION TO EXERT A FORCE ON THE CONTROL MEANS TOWARD THE MOTION-PERMITTING POSITION, AND A MAGNETIC ELEMENT WHICH CONTROLS THE POSITION OF THE CONTROL MEANS; MEANS FOR ESTABLISHING A FIXED MAGNETIC FIELD TO ATTRACT THE MAGNETIC ELEMENT FOR PROVIDING A FORCE ON THE CONTROL MEANS TOWARD ITS MOTION-IMPEDING POSITION, SAID FORCE EXCEEDING THE COCKING FORCE; AND MEANS FOR SELECTIVELY ESTABLISHING A TEMPORARY MAGNETIC FIELD IN OPPOSITION TO THE FIXED MAGNETIC FIELD FOR COUNTERACTING THE FIXED MAGNETIC FIELD, ENABLING THE COCKING FORCE TO MOVE THE CONTROL MEANS TOWARD ITS MOTION-PERMITTING POSITION.