Reset Mechanisms

Abstract

A reset mechanism for a stop-watch is operable to rotate two cams on the staves of the minute and second hands respectively of the watch, back into datum angular positions. Depression of a reset button of the mechanism actuates an operating lever that engages with a cam surface of a pivotally-mounted support-member to pivot the support member towards the cams against the action of a spring. A striker of unitary construction and having camming surfaces for engaging the cams is pivotally mounted on the support member but is restrained from more than small angular displacement relative to the support member by a pin which from the striker member engages in an oversized hole in the support member. Pivoting of the support-member carries the striker to bring its two camming-surfaces into engagement with the two cams respectively, the loose mounting of the striker on the support member permitting it limited adjustment of orientation relative to the support-member to ensure that the camming surfaces are both brought into positive engagement with their respective cams. The striker is constrained to movement along a path which is defined by a slot in the base plate of the mechanism and which is spaced from the support-member pivot, the slot being engaged by a pin which is carried on the striker and which is spaced from the pivot of the striker with the support member.

Description

This invention relates to reset mechanisms and is particularly, although not exclusively, concerned with the provision of such mechanisms for resetting the hands of a stop-watch to zero.

One form of reset mechanism in common use at present provides a cam-piece which when released is operable under the influence of a spring to cooperate with cams mounted on the staves of the hands of the watch to return those hands to a datum position.

Practical difficulties arise in using the above form of reset mechanism not the least of which lies in the use of a spring to effect the resetting operation. Again, in view of the accuracy with which it is desired to reset the hands of a stop watch to zero, the various parts of the reset mechanisms used heretofore have had to be formed, and then their assembly carried out, with a great accuracy. This has the inevitable effect of increasing both the cost of the various parts of the watch and the costs of assembling those parts in a watch.

According to this invention a reset mechanism comprises a striker member which is loosely mounted on a movably-mounted support member and which has a camming surface for engaging a reset cam of the mechanism for resetting the cam to a datum position, and operating means which is actuable to engage with the support member and to cause it to move such that the camming surface of the striker member engages the reset cam to reset it to its datum position.

One advantage of the invention over the prior proposals is that the various parts of the reset mechanism may be manufactured to a lesser (or at least the same) degree of accuracy than has heretofore been necessary. Another advantage resulting from the same feature of the invention is that the loose coupling between striker and support members permits their assembly very cheaply and quickly.

Further advantages including, for example, the nonreliance on a spring to effect the resetting action, will become apparent from the description of a stop-watch including the reset mechanism which follows.

The stop-watch is described, by way of example only, with reference to the accompanying drawings, which show in FIGS. 1 and 2 respectively the watch before and after resetting of the hands.

Referring to FIGS. 1 and 2, the casing 9 of the watch carries a movement of which only one mounting plate 10 is shown. A winder-reset button 12 is carried by the movement and extends through a hole in the casing 9. Also mounted on the movement to extend through a hole in the casing 9 is a stop-start button 13. The button 13 may operate as described in my copending U. S. Pat. application Ser. No. 279,400, filed Aug. 10, 1972, in starting and stopping operation of the watch. The reset button 12 includes a knurled winder knob 14 and stem 15. The stem 15 connects to the movement of the watch and may be operated to `wind-up` the mainspring of the watch in any well known way. Whenever the button is depressed a flange 17, which is formed integrally with the stem 15 engages a boss 18 formed of an operating lever 19 pivotally mounted at one end, 20, on the plate 10. The operating lever 19 carries a shouldered stud 21 located in a slot 22 formed in the mounting plate 10. The mounting plate 10 also carries an arcuate support member 23 pivotally mounted at one end 24.

The striker member 28 is constrained to follow a predetermined path relative to the mounting plate 10 during movement of the support member 23. This path is defined by a slot 30 in the plate 10, and is followed by a pin member 29 that is carried by the striker member 28 to engage with the slot 30. The other end of member 23 is formed with a camming surface 26 and pivotally supports, at 27, a striker member 28. The striker 28 is formed with two camming surfaces 31 and 32 which are engageable respectively with two reset cams 33 and 34. The cams 33 and 34 are rigidly mounted on the staves carrying the minute and second hands of the watch. A pin or half-sheered dowel in striker 28 engages loosely in a hole 35 in the arcuate support member 23 so that striker 28 is free to rotate through a small angle about its pivotal support 27. A spring 36 is provided to bias the arcuate support member away from the cams 33 and 34 as shown.

Operation of the mechanism will be described assuming that the mechanism is initially in the position shown in FIG. 1 - that is to say with the hands stopped but not reset. Depression of the button 12 to reset the hands of the watch to zero, causes the flange 17 on the winding stem 15 to move inwardly hard against the boss 18. Continued depression of button 12 moves the operating arm 19 about its pivot 20 until the free end of arm 19 engages the surface 26 of the arcuate support member 23. Member 23 is forced inwardly carrying with it the striker member 28 to follow the path defined in the mounting plate 10 by the slot 30, until the surfaces 31 and 32 engage the cams 33 and 34 respectively. Further movement of button 12 results in the cams 33 and 34 being reset to the position shown in FIG. 2. When released the button 12 is driven back to the position shown in FIG. 1 under the influence of spring 36.

The "floating" feature of striker 28 provided by the loose mounting of the striker 28 on the support member 23, and acting within the constraint imposed by engagement of the pin 29 in the slot 30, ensures that cams 33 and 34 are returned to zero accurately and variations in manufacturing accuracies and finish are compensated for. The surfaces 31 and 32 and the faces of the cams 33 and 34 which they engage may be flat, as shown, or curved. In this latter respect the faces 31 and 32 are preferably convex and the faces on the cams shaped to conform with them. The cam shaping facilitates return of each cam to its zero, datum position through the shortest available angular path when acted upon by the striker 28.

Means may be provided, associated with the stop-start mechanism for preventing operation of the reset mechanism while the hands of the watch are in motion.

Claims

I claim:

1. A reset mechanism comprising a base member, a reset cam which is mounted on the said base member for angular movement into a datum angular position with respect to said base member, a support member, pivot means pivotally mounting said support member on said base member for movement relative to said cam, a striker member, further mounting means loosely mounting said striker member on the support member, the striker member having a camming surface for effecting engagement with the said cam to displace the cam angularly into said datum angular position, operating means actuable to engage the support member to move it to bring said striker member into said engagement with the cam so as to reset the cam to its said datum angular position, and means interconnecting said striker member and said base member to constrain the said striker member to follow a predetermined path relative to the said base member, and thereby to said cam, during said movement of the support member, said interconnecting means being operative along said path to interconnect a part of the striker member spaced from the said further mounting means with a part of the said base member spaced from said pivot means.

2. A reset mechanism as claimed in claim 1 in which the support member has a cam-surface part, and the said operating means comprises a pivotally mounted lever member having a camming surface for engaging said cam-surface part of the support member to effect the said movement of the support member.

3. A reset mechanism according to claim 1 in which said means interconnecting said striker and base members comprises a pin element carried by one of said striker and base members to engage in a slot in the other of the said striker and base members.

4. A reset mechanism as claimed in claim 1 in which said further mounting means comprises means pivotally mounting the striker member on the support member, and means to restrain said striker member from substantial pivotal movement relative to the support member when the striker member is brought into said engagement with said cam.

5. A reset mechanism according to claim 4 in which said means to restrain said striker member comprises a pin element carried by one of the siad striker and support members to engage in an aperture in the other of said striker and support members.

6. In a stop-watch, a reset mechanism comprising a base plate, a reset cam mounted on the staff of a hand of the stop-watch and movable angularly to a datum angular position with respect to the base plate to reset the said hand of the stop watch, a support member, pivot means pivotally mounting said support member on said base plate for movement relative to said base plate and said cam, a striker member, further mounting means loosely mounting said striker member on the support member, the striker member having a camming surface for effecting engagement with the said cam to displace said cam angularly into said datum angular position, operating means actuable to engage with the support member to move it to bring the said striker member into said engagement with the cam so as to reset the cam to its said datum angular position, and means interconnecting said striker member and the said base plate to constrain the said striker member to follow a predetermined path relative to the said base plate, and thereby to said cam, during said movement of the support member, said base plate having a slot therein that is spaced from said pivot means to define said path, and said interconnecting means comprising an element carried by said striker member to engage in said slot throughout said movement of the support member, said element being spaced on said striker member from the said further mounting means.

7. In a stop-watch, a reset mechanism comprising: a base member; a pair of reset cams mounted respectively on the staves of the minute and second hands of the watch, said cams being movable angularly with respect to said base member into respective datum angular positions to reset the hands of the stop watch; a support member; mounting means pivotally mounting said support member on said base member for movement relative to the said pair of cams; a unitary striker member loosely mounted on the support member, the striker member comprising two camming surfaces each for effective engagement with a respective one of said pair of reset cams, and means rigidly interconnecting the two camming surfaces with one another as a unitary whole; operating means actuable to engage with the support member to move it to bring the said striker member into said engagement with the said pair of reset cams so as to reset the said pair of cams to their respective datum positions; and means interconnecting the striker member with the base member to constrain the striker member to follow a predetermined path relative to the said base member, and thereby to said cams, during the said movement of the support member said base member having a slot therein that is spaced from said mounting means to define said path, and said interconnection means comprising an element carried by said striker member to engage in said slot throughout said movement of the support member.