US3871238A

US3871238A - Intermittent motion mechanism

Info

Publication number: US3871238A
Application number: US368530A
Authority: US
Inventors: Kiysohi Kitai
Original assignee: Seiko Koki KK
Current assignee: Seiko Koki KK
Priority date: 1972-06-09
Filing date: 1973-06-11
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: DE2329447A1; FR2188747A5; JPS4918063A; GB1426098A

Abstract

An intermittent motion mechanism comprises a pair of ratchet wheels mounted in side-by-side relationship for rotary movement independently of each other. One of the ratchet wheels is provided with an extra deep tooth space between two of its ratchet teeth and this ratchet wheel is intermittently rotated by a reciprocatory feeding ratchet to cyclically advance same through a series of angular increments to a position wherein the extra deep tooth space moves into alignment with one of the tooth spaces existing between the ratchet teeth of the other ratchet wheel. When the extra deep tooth space is aligned with the other tooth space in this manner, either the aforesaid feeding ratchet or another feeding pawl engages with both ratchet wheels and angularly advances them in unison through one angular increment.

Description

United States Patent 1191 Kitai INTERMITTENT MOTION MECHANISM [75] Inventor: Kiysohi Kitai, Tokyo, Japan [73] Assignees Seiko Koki Kabushiki Kaisha,

Tokyo, Japan 22 Filed: June 11, 1973 21 Appl.No.:368,530

[30] Foreign Application Priority Data 1111 3,871,238 Mar. 18, 1975 Primary ExaminerWesley S. Ratliff, Jr. Attorney, Agent, or Firm-Robert E. Burns; Emmanuel J. Lobato; Bruce L. Adams 57 ABSTRACT An intermittent motion mechanism comprises a pair of ratchet wheels mounted in side-by-side relationship for rotary movement independently of each other. One of the ratchet wheels is provided with an extra deep tooth space between two of its ratchet teeth and this ratchet wheel is intermittently rotated by a reciprocatory feeding ratchet to cyclically advance same through a series of angular increments to a position wherein the extra deep tooth space moves into alignment with one of the tooth spaces existing between the ratchet teeth of the other ratchet wheel. When the extra deep tooth space is aligned with the other tooth space in this manner,'either the aforesaid feeding ratchetor another feeding pawl engages with both ratchet wheels and angularly advances them in unison through one angular increment.

1 Claim, 8 Drawing Figures l INTERMITTENT MOTION MECHANISM FIELD OF THE INVENTION The present invention pertains generally to intermittent motion mechanisms and more particularly, to an intermittent motion mechanism having a plurality of ratchet wheels which are intermittently rotated at different rates to obtain a plurality of intermittent output motions.

BACKGROUND OF THE INVENTION Intermittent motion mechanisms are well known in the art and the most common type heretofore employed is of the pawl-and-ratchet type and utilize feeding pawls and holding pawls which are spring-biased into engagement with the ratchet wheel. Consequently,

when the feeding pawl rides over a tooth of the ratchet wheel during its return stroke and drops down into the tooth space between the successive ratchet teeth, the feeding pawl makes a clicking sound. Likewise, when the ratchet wheel is advanced so that the holding pawl rides over a tooth of the ratchet wheel, a clicking sound results when the pawl drops down into the tooth space between successive ratchet teeth. If such an intermittent motion mechanism is used in a clock, the continual clicking sound is disadvantageous since it is desirable to have the clock operate quietly. Moreover, the repeated impacts of the feeding pawl and holding pawl with the ratchet wheel result in wear of the parts necessitating their replacement. In addition, if the biasing springs which bias the feeding pawls and holding pawls should break or become weakened the whole mechanism becomes inoperative.

To solve the aforementioned problems, an intermittent motion mechanism has been developed which operates quietly and is of simple construction having a minimum number of parts and having a long useful life. Such an intermittent motion mechanism eliminates the biasing springs and instead, urges the feeding pawl and the holding pawl into engagement with the ratchet wheel by frictional engagement with rotary members by which thefeeding pawl and holding pawl are actuated. Hence, when the feeding pawl and holding pawl ride over successive teeth of the ratchet wheel, they do not drop down into the intervening spaces with a noiseproducing impact but instead are moved at a controlled rate by which impact and resultant noise are avoided. This type of intermittent motion mechanism is fully disclosed in related U.S. Pat. application Ser. No. 349,865 filed on Apr. 10, 1973.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an intermittent motion mechanism which operates quietly and noiselessly and provides a plurality of different intermittent rotary output motions.

It is a further object of the present invention to provide an intermittent motion mechanism having a plurality of ratchet wheels which are coupled together in such a manner that they undergo intermittent and synchronous rotation with each other at different rates.

It' is yet another object of the present invention to provide an intermittent motion mechanism which is very simple in construction, inexpensive to manufacture, and sufficiently rugged and sturdy so that the 2 mechanismis reliable in operation and has a long useful life.

It is still another object of the present invention to provide 'an intermittent motion mechanism for producing a plurality of intermittent rotary outputs and which is especially suitable. for use in a clock or other device requiring a timing mechanism.

The above and other objects of the present invention are carried out by an intermittent motion mechanism comprising a pair of ratchet wheels each having a set of ratchet teeth and the ratchet wheels are arranged relative to one another such that a common feeding pawl may simultaneously engage both ratchet wheels to angularly advance them during a portion of the rotation cycle of each ratchet wheel. One of the ratchet wheels is provided with one or more extra-deep tooth spaces between successive ratchet teeth and the ratchet wheels are arranged so that the extra-deep tooth spaces of the one ratchet wheel periodically move into alignment with the normal tooth spaces between the teeth in the other ratchet wheel whereupon the common feeding pawl enters both tooth spaces and simultaneously drives both ratchet wheels through one angular increment. Whenever the extra-deep tooth spaces are not in a position to receive the common feeding pawl, the feeding pawl drives only the one ratchet wheel whereby a plurality of intermittent rotary output motions are obtained.

BRIEF DESCRIPTION'OF THE DRAWINGS Having in mind the-above and other objects that will be evident from an understanding of this disclosure,'the present invention comprises the combinations and arrangements of parts as illustrated in the presently preferred embodiments of the invention which are hereinafter set forth in sufficient detail to enable those persons skilled in the art to clearly understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings, wherein like reference characters denote like parts in the various views, and wherein:

FIG. 1 is a schematic plan view showing the essential parts of an intermittent motion mechanism constructed in accordance with the present invention;

FIG. 1A is a schematic plan view similar to FIG. I but showing the parts in a different portion of their operating cycle;

FIG. 1B is a schematic plan view similar to FIG. 1A but showing the parts in a more advanced stage of their operating cycle;

FIG. 2 is a cross-section taken along the line lI-2 in FIG. 1;

FIG. 3 is a schematic plan view of a second embodiment of intermittent motion mechanism constructed in accordance with the principles of the present invention;

FIG. 4 is a schematic plan view showing the essential parts of another embodiment of intermittent motion mechanism constructed in accordance with the principles of the invention;

FIG. 5 is a side view, in cross-section, of the essential parts of a clock mechanism embodying the intermittent motion mechanism of the invention; and

FIG. 6 is a side view, in cross-section, of a portion of the intermittent motion mechanism employed in the clock mechanism.

ratchet wheel-3 is secured to the shaft 2 and has around' its periphery asetof ratchet teeth which each have a sawtooth shape with one sloping flank and one abrupt face. In thisembodiment, the set of ratchet teeth comprise 30 teeth disposedequidistantly apart around the periphery of the ratchet wheel 3 with a tooth space existing between each two adjacent teeth and one extradeep tooth space 3a extends radially much deeper into the ratchet wheel than do the remaining tooth spaces for reasons described hereinafter. Another ratchet wheel is disposed opposite andfacing the ratchet wheel 3 and is secured to a tubular shaft 4 which-is rotatably mounted upon another support plate 6, as shown in FIG. 2. The tubular shaft 4 is rotatably mounted on the shaft 2 so that both shafts are free to rotate independently of each other. The ratchet wheel 5 has around its periphery a set of ratchet teeth which have a sawtooth shape similar to those of the ratchet wheel 3 and in this embodiment, the set comprises 60 teeth. A tooth space exists between each two adjacent teeth and the one extra deep tooth space 3a in the ratchet wheel 3 extends to a depth substantially equal to that of the tooth space in the ratchet wheel 5. A shaft 7 is rotatably mounted upon the support plate 1 and has a gear wheel fixedly secured thereto. On one face of the gear wheel 10 there is provided an eccentric disc portion 8and a second smaller eccentric disc portion 9 superposed on the'disc portion 8'. Outboard of the disc portion 9 there is provided a sleeve portion 10a which is coaxial with the gear wheel 10 and the gear wheel 10, the disc portions 8, 9 and the sleeve portion 10a comprise a one-piece unitary structure which is rotatable about the shaft 7. The eccentricity of the disc portions 8 and 9 with respect do the axis of rotation of the gear wheel 10 is somewhat greater than one-quarter of the pitch of the teeth of the ratchet wheel 3 and the two disc portions are arranged relative to one another so that they are eccentric in opposite directions with respect to the rotary axis of the gear wheel 10.

Two

feeding'pawls

11 and 13 are mounted respectively on the eccentric disc portions 8 and 9. The feeding pawl 11 has a nose portion 11a engageable with the teeth of the ratchet wheel 3 and a split collar portion l2'whi'chextends around the eccentric disc 8 except for a split orgap. Likewise, the feeding pawl 13 has a nose portion 13a engageable with the teeth of both of the

ratchet wheels

3 and 5 and a split collar portion 14 which extends around the eccentric disc 9 except for a split or gap. The nose portion 130 is much wider than the nose portion 11a and overlaps both ratchet wheels, as seen in FIG. 2. Moreover, the nose portion 13a is configured to engage with both sets of ratchet teeth provided on the

ratchet wheels

3 and 5 to angularly advance these wheels as described hereinafter.

A holding pawl l5 is mounted on the sleeve portion l0a. The pawl has a nose portion 15a engageable with the" teeth of the ratchet wheel 5 and a split collar portion 16 which extends around the sleeve portion 10a-of the gear wheel 10. The collar portion 16 of the locking pawl. and the

collar portions

12 and 14 of the feeding pawls are made of resilient material and when these collar portions are in a relaxed condition, their inner diameters are somewhat smaller than the diameters of the corresponding portions on which they are mounted so that when the pawl 15 and feeding pawls l1 and 13 are assembled on the gear wheel 10, they grip the gear wheel with a friction fit. I-Ience, when the gear wheel 10 is rotated in a' counterclockwise direction-as indicated by the arrow, the frictional engagement between

thecollar portions

12 and 14 and the disc portions 8 and 9 as well as the frictional engagement between the collar portion 16 and the sleeve portion 10a effects urging of the feeding pawls and the holding pawl into engagement with their associated ratchet wheels.

The operation of the intermittent motion mechanism will now be described assuming that the gear wheel 10 I is in mesh with a drive pinion 18 which is rotationally driven by a motor or the like and assuming that the components are in thepositions shown in FIG. 1. In the state shown in FIG. 1, the'feeding pawl 11 isin engagement with the teeth of the ratchet wheel 3, the feeding pawl 13 is about to engage with the teeth of both

ratchet wheels

3 and 5, and the holding pawl is in engagement with the teeth of the ratchet wheel 5 in order to prevent reverse rotation of the wheel 5.

i As the drive pinion 18 rotates clockwise, the gear wheel 10 is rotationally driven counterclockwise causing the feeding pawl 11 to recede to the right out of driving engagement with the ratchet wheel 3 while the feeding pawl 13 proceeds to the left into driving or feeding engagement with both the ratchet wheels 3' and 5. At this time, the nose portion 13a fits within the enlarged tooth space 3a of the ratchet wheel 3 and simulhalf pitch while simultaneously advancing the ratchet wheel 5 through one complete pitch.

As the gear wheel 10 rotates through another the components obtain the position shown in FIG. 13 during which time the feeding pawl 11 angularly advances the ratchet wheel 3 through one-half pitch while the ratchet wheel 5 remains stationary and is locked against reverse rotation by the holding pawl 15.

Thus as the gear wheel 10 is driven through one rotation, the ratchet wheel 3 is advanced a distance corresponding to one-half the pitch of the teeth by the feeding pawl 11 and is likewise advanced a distance corresponding to one-half the pitch ofthe teeth by. the feeding pawl 13 so that the ratchet wheel 3 is advanced one full pitch for each complete rotation of the gear wheel 10. Since the feeding pawl 13 is only able to engage with the ratchet wheel 5 when the enlarged tooth space 3a is in the position shown in FIG. 1 and since this occurs only once per each complete revolution of the ratchet wheel 3, the ratchet wheel 5 is advanced an angular distance corresponding to one full pitch of its ratchet teeth per each revolution of the ratchet wheel 3. By such an arrangement, the

shafts

2 and 4 are intermittently and progressively advanced in a stepwise manner by the continuous rotation of the gear wheel 10 and the shafts are synchronously driven so that the shaft 4 is angularly advanced one pitch per each full revolution of the shaft 4.

In the embodiment described, the ratchet wheel 5 is driven one increment after the ratchet wheel 3 has undergone intermittent angular movement through a pre selected number of angular increments, i.e., the ratchet wheel 5 moves one increment or one pitch after the ratchet wheel 3 has moved through 59 increments or half-pitches and the wheel 3 moves through its one increment simultaneously with the movement of the wheel 5 through its sixtyth increment. Of course, other synchronous modes of rotation may be realized by employing two, three, four or any other number of extraordinarily deep tooth spaces alike the tooth space 3a. For example, if three such tooth spaces are employed, the ratchet wheel 5 will intermittantly advance through three increments per revolution of the ratchet wheel 3. Moreover, it is possible to replace the holding pawl with other means, such as frictional load, for preventing reverse movement of the ratchet wheels.

In an alternative construction shown in FIG. 3, the ratchet wheel 5' is housed within a recess formed in one side face of the ratchet wheel 3'. In this construction, the extra deep valley 3a overlies the set of ratchet teeth on the ratchet wheel 5 and the feeding pawl 13 engages with the teeth on both ratchet wheels by extending radially inwardly through the periphery of the ratchet wheel 3' to engage with the teeth of the ratchet wheel 5'.

Another embodiment of the intermittent motion mechanism is shown in FIG. 4.

Ratchet wheels

23 and 25 correspond to the

wheels

3 and 5 respectively in the FIG. 1 embodiment. A gear wheel has an eccentric disc portion 29 and a central sleeve portion 27. In this embodiment, a single feeding pawl 33 having a wide nose portion 33a is used to drive both ratchet wheels and the feeding pawl 33 has a split collar portion 34 mounted upon and in frictional engagement with the eccentric disc 29.

A holding pawl 35 is frictionally mounted upon the sleeve portion 27 of the gear wheel 30 and engages with the ratchet wheel 25 to prevent reverse rotation thereof by releasably holding the ratchet wheel in each successive advanced position. Likewise, a holding pawl 39 is frictionally mounted upon the sleeve portion 27 and engages with the ratchet wheel 23 to prevent same from undergoing reverse rotation.

In the FIG. 4 embodiment, the eccentricity of the disc portion is slightly greater than one-half of the pitch of the teeth of the ratchet wheel 23 so that each revolution of the gear wheel 30 reciprocates the feeding pawl 33 leftwardly and rightwardly to advance the ratchet wheel 23 one increment or one pitch. The holding pawl 39 engages with the ratchet wheel 23 to prevent reverse movement thereof during the rightward return stroke of the feeding pawl 33.

It will be evident to those skilled in the art that the FIG. 4 embodiment may be modified to have other desired modes of rotation with different ratios of rotation between the

ratchet wheels

23 and 25. For example, if four extra deep valleys are provided in the ratchet wheel 23, the ratchet wheel 25 will be intermittently advanced four increments per revolution of the ratchet wheel 23.

A clock mechanism embodying the intermittent motion mechanism of the invention is shown in FIGS. 5

and 6. The clock mechanism has a pair of

support plates

51 and 56 which are disposed in spaced-apart relationship and contain therebetween the clock movement. A second shaft 52 is'rotatably mounted at one end on thesupport plate 51 and a minute shaft 54 is rotatably mounted within the clock mechanism and rotatably receives therethrough the second shaft 52. The shaft 54 has a hollow tubular configuration and the shaft 52 extends through the interior of the shaft 54 and is rotatable relative thereto so that each shaft may rotate independently of the other. A ratchet wheel 53 is secured to the shaft 52 and another, smaller ratchet wheel 55 is secured to the shaft 54. The ratchet wheel 55 is housed within a recess provided in the ratchet wheel 53 and this arrangement is similar to that shown in FIG. 3. Each ratchet Wheel has a set of ratchet teeth around its periphery and the ratchet wheel 53 has an extra-deep valley or space 53a between two successive ratchet teeth and the valley 53a is superposed over the set of ratchet teeth on the ratchet wheel 55. The ratchet wheel 53 is provided with thirty ratchet teeth and the ratchet wheel 55 is provided with 60 ratchet teeth.

A hollow rotatable hour shaft 71 rotatably extends around the shaft 54 as shown in FIG. 5. A series of clock hands are secured to the shafts and the hands comprise a second hand 73 secured to the second shaft 52, a minute hand 74 secured to the minute shaft 54 and an hour hand secured to the hour" shaft 71. Thus as each of the shafts rotate, the corresponding hand also rotates to provide a visual indication of the time. A dial face 89 is disposed on the front face of the support plate 56 and contains suitable time indicia which coact with the clock hands to indicate the time.

The details of the intermittent motion mechanism are shown in FIG. 6 and the mechanism comprises a shaft 57 mounted upon the support plate 51 and a rotary gear wheel 60 is mounted to undergo rotation on the shaft 57. The gear Wheel 60 has a first eccentric disc portion 58 and a second eccentric disc portion 59 and the disc portions are formed integrally with the gear wheel 60. A feeding pawl 61 is mounted on the eccentric disc 58 by means of a split collar portion 62 which is in friction engagement with the disc 58. Likewise, a feeding pawl 63 is mounted upon the eccentric disc 59 by means of a split collar portion 64 which is in frictional engagement with the disc 59.

The feeding pawl 61 is positioned to engage with the teeth of the ratchet wheel 53 along one perpheral side of the ratchet wheel whereas the feeding pawl 63 is positioned to engage with the teeth of the ratchet wheel 53 on the other peripheral side and to also engage with the ratchet wheel 55 whenever the extra-deep valley 53a is advanced into the appropriate position. Thus the feeding pawl 63 engages with both the ratchet wheels 53 and 55 whenever the extra-deep valley 53a is in a position .to receive the nose portion of the feeding ratchet 63. The amount and direction of eccentricity of the

disc portions

58 and 59 are similar to the embodiment shown in FIG. 1. A retaining disc 76 is positioned outboard of the feeding pawl 63 and coacts with the gear wheel 60 to retain the feeding pawls on the gear wheel.

The gear wheel 60 is rotationally driven by a synchronous motor 77 through a gear train. The synchronous motor is of conventional construction and may be a pulse motor, a Wallen motor, or a hysteresis motor, and

7 v is secured to the supportplate 51. A gear sleeve 78 is connected to the synchronous motor output shaft for "rotational movement therewith and a gear 79 meshes manner by the synchronousmotor 77. In the embodiment shown, the synchronous motor rotationally drives its output shaft at a rate of one revolution in two seconds. 7

Referring again to FIG. 5, a pinion gear 81 is formed integrally with the ratchet wheel 55 and rotates therewith during operation of the clock-mechanism. A gear wheel 82 is in meshing engagement with the pinion gear I 81 and is secured to a shaft 83 which is rotatably speed reduction system having a reduction ratio of.

60:1. A biasing spring 85 is interposed between the support plate 56 and the pinion gear 84 to maintain the speed reduction gear system under a small frictional load to thereby take-up any free play which may exist. Along one side face of the gear wheel 82 is provided a gear ring 86 which meshes with a gear wheel 87. The gear wheel 87 is mechanically coupled through a shaft to a correction knob 88 whereby the clock hands may be adjusted and corrected by manual turning of the knob 88.

The operation of the clock mechanism will now be described. The synchronous motor 77 acts through the gear train to rotationally drive the gear wheel 60 whereby the feeding pawls 61 and 63 are reciprocated and each forward and return stroke of each feeding pawl effect angular advancement of the ratchet wheel 53 through an angular distance of one-half of the pitch of the ratchet teeth of the ratchet wheel 53. This intermittent angular motion is transmitted to the second shaft'52 to accordingly drive the second hand 73. As the ratchet wheel 53 makes one revolution, the feeding pawl 63 falls into the extra-deep valley 53a and thereby drives the ratchet wheel 55 through one pitch whereby the minute shaft 54 is advanced along with the minute hand 74. In a similar manner, the intermittent rotation of the ratchet wheel 55 is transmitted to the hour shaft 71 through the speed reduction gear system to effect intermittent rotation of the hour hand 75. In this manner, the intermittent motion mechanism effects synchronous intermittent rotation of the second hand 73 and the minute hand 74 and coacts with the speed reduction gear system to effect corresponding intermittent rotation of the hour hand 75.

Of course, the intermittent motion mechanism used in the clock mechanism may obviously be of the'type disclosed in FIGS. 1 or 4. 7

Thus it may be appreciated that the clock'mechanism effectively utilizes the intermittent motion mechanism of the invention to effect noiseless operation of the various clock hands and in view of the compactness of the intermittent motion mechanism, the entire'clock mechanism is considerably reduced in size in comparison to the prior art clock mechanisms. Moreover, in accordance with the invention, it is very easy to synchronize the setting of the secondv hand and the minute hand since both of these hands are actuated by the intermittent motion mechanism and thus when the second is at a zero setting, the minute hand may be precisely set so that correct time indication may be obtained.

The invention has been described in conjunction with several preferred embodiments and it is to be understood that obvious modifications and changes may be made without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. An intermittent motion mechanism comprising: a first rotary ratchet wheel having disposed therearound a first set of ratchet teeth and having an intervening tooth space between each two successive ratchet teeth; a second rotary ratchet wheel having disposed therearound asecond set of ratchet teeth and having an intervening tooth space between each two successive ratchet teeth, at least one of said tooth spaces being deeper than the remaining tooth spaces; means mounting said first and second ratchet wheels in side-by-side relationship for rotational movement independently of each other and mounting said first and second ratchet wheels in mutually relative positions so that said second ratchet wheel may be cyclically moved into an actuating position wherein the deeper tooth space is in alignment with one of the tooth spaces between successive ratchet teeth of said first ratchet wheel; means reciprocable into engagement with said second set of ratchet teeth to effect intermittent angular movement of said second ratchet wheel through a plurality of angular increments to cyclically advance same to said actuating position and reciprocable into concurrent engagement with both said first and second sets of ratchet teeth when said second ratchet wheel is in said actuating position to effect intermittent angular movement of both ratchet wheels through one angular increment; whereby said first and second ratchet wheels are intermittently rotated in a stepwise manner at different rates, and said last-mentioned means comprising a pair of feeding pawls one of which engages only with said first set of ratchet teeth and the other of which engages with both said first and second sets of ratchet teeth.

Claims

1. An intermittent motion mechanism comprising: a first rotary ratchet wheel having disposed therearound a first set of ratchet teeth and having an intervening tooth space between each two successive ratchet teeth; a second rotary ratchet wheel having disposed therearound a second set of ratchet teeth and having an intervening tooth space between each two successive ratchet teeth, at least one of said tooth spaces being deeper than the remaining tooth spaces; means mounting said first and second ratchet wheels in side-by-side relationship for rotational movement independently of each other and mounting said first and second ratchet wheels in mutually relative positions so that said second ratchet wheel may be cyclically moved into an actuating position wherein the deeper tooth space is in alignment with one of the tooth spaces between successive ratchet teeth of said first ratchet wheel; means reciprocable into engagement with said second set of ratchet teeth to effect intermittent angular movement of said second ratchet wheel through a plurality of angular increments to cyclically advance same to said actuating position and reciprocable into concurrent engagement with both said first and second sets of ratchet teeth when said second ratchet wheel is in said actuating position to effect intermittent angular movement of both ratchet wheels through one angular increment; whereby said first and second ratchet wheels are intermittently rotated in a stepwise manner at different rates, and said last-mentioned means comprising a pair of feeding pawls one of which engages only with said first set of ratchet teeth and the other of which engages with both said first and second sets of ratchet teeth.