US3676995A

US3676995A - Return mechanism for a stopwatch or a chronograph

Info

Publication number: US3676995A
Application number: US25718A
Authority: US
Inventors: Katsuhiko Morita; Yoshio Yamamoto
Original assignee: Seiko Instruments Inc
Current assignee: Seiko Instruments Inc
Priority date: 1969-04-16
Filing date: 1970-04-06
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18
Also published as: GB1270747A

Abstract

In a return mechanism of a chronograph or stopwatch, a plurality of heart-shaped cams are returned to zero position by means of a rotatable hammer having an equal number of acting surfaces which press against the cams during actuation. Each of the acting surfaces in excess of one is flexible with respect to the remainder of the hammer.

Description

United States Patent Morita et al. [4 1 July 18, 1972 [54] RETURN MECHANISM FOR A [56] References Cited STOPWATCH OR A CHRONOGRAPH FOREIGN PATENTS OR APPLICATIONS [72] Inventors: Katsuhiko Morita- Yoshlo Yamamoto both of-rokyojapn 466,152 1/1969 Sw tzerland ..58/74 285,850 9/1952 Switzerland ..58/74 1 s Kabushlki Keisha Dflini Selkwha, Tokyo, 286,565 10/1952 Switzerland ..ss/74 Japan [22] Filed: April 6, 1970 Primary Examiner-Richard B. Wilkins [211 APPLNO': 25,718 Assistant Examiner-George H. Miller, Jr.

AttorneyBlum, Moscovltz, Friedman & Kaplan [30] Foreign Application Priority Data 57] ABSTRACT April 16, 1969 Japan ..44/34l59 In a [6mm mechanism of a chrono graph or stopwatch, a plu- Apnl 7 vu l f ai l 'ifiiii"?"8'21""1'74fl tality of heart-shaped cams are returned to zero position by 52 U.S Cl ..58/76 means "Mable hammer having an equal number Field of Search ..:.58/74-79 ing surfaces which press against the cams during actuation. Each of the acting surfaces in excess of one is flexible with respect to the remainder of the hammer.

1 Claim, 3 Drawing Figures PATENTED JUU 8 I972 MQm $23553 STROKE RETURN MECHANISM FOR A STOPWATCH OR A CI-IRONOGRAPH DETAILS or THE INVENTION This invention relates to the improvement of a hammer being provided with at least two acting surfaces and the improvement of characteristics of the working stroke of the hammer. A hammer which works with at least two hearts and a return hand is provided with the acting surfaces cooperating with at least two hearts. In the return hand the acting surfaces must contact the shoulder of the heart without a gap.

In an ordinary return mechanism, however, gaps cannot be avoided of all shoulders of heart except shoulders of one heart due to production error. The acting surfaces are adjusted by a file to reduce thegaps. Such adjustment has inconveniences which make the surfaces rough by filing of acting surfaces and is apt to make the corner of the hammer round.

, Moreover, as the working force receives the feeble resistance at the beginning of the push, the acting surfaces of the hammer acts with too weak a force so that it cannot return the hand to zero and the heart stops.

The hammer according to this invention is provided with at least two acting surfaces and at least two spring parts so as to absorb the gap due to production error and to act without adjustment. By making the spring part of the hammer cooperate with the pin inserted in the plate, the working force at the beginning of the push is made stronger and the acting surface of the hammer acts on the heart and the hand automatically returns to zero.

EXPLANATION OF THE FIGURES FIG. I is a plane view of a return mechanism according to the invention;

FIG. 2 is a view and explanation of action; and

FIG. 3 is a characteristics diagram of the working stroke of a return mechanism.

Referring now to the drawings, 1 is a hammer which is provided with, in this case, two acting surfaces 1a and 1b which cooperate respectively with

hearts

3 and 4. Hammer 1 has a spring portion 1d which gives the hammer the force of restitution. 6 is the locating pin which locates the hammer on restitution point. Usually the hammer is restored to the original state as shown in FIG. 1. When returning the hand, the hammer acts in the state of action as shown in FIG. 2. The position of the hammer is settled by the rotating axle 2 and heart 3. The acting surface la or 1b was hitherto filed and adjusted in order to reduce the gap between heart 4 and the acting surface lb. In this invention, the acting surface lb and the hammer are combined by the spring portion 10, and the spring portion 11 is disposed to be automatically bent when la and heart 3 make contact. In this way the gaps between more than two hearts and the hammer l are absorbed without forcing the axle of heart 4. v

EXPLANATION OF THE WORKING FORCE When a pushed part 1f of the hammer is actuated externally the projection 1e of the spring portion 1d is connected with a pin 5, and a strong working force is set in motion on the acting surface 1b and makes the

hearts

3 and 4 return automatically to zero. When the external pressure acts on the pushed part, and the hammer l rotates to some extent, the spring portion ld moves as shown in FIG. 2 in the direction of arrow A and the projection le slips out of the pin 5, thus weakening the working force of the acting surface. The relation between working force of acting surface which acts on the heart and the stroke of the pushed part If is as shown in FIG. 3; the working force is strong at the beginning of the stroke and weak in the latter half. This working force therefore makes returning to zero more sure than a flat working force of an ordinary mechanism 6 as shown in FIG. 3.

The invention as above mentioned has the advantages of beingable to eliminate the. difficult adjustment without spoiling the finishing-10f the acting surface. Moreover, as the spring portion of the ammer can be moved, the workmg force Is strong at the beginning and weak in the latter half, this mechanism can return hearts to zero automatically.

What is claimed is:

l. A return mechanism for a chronograph or a stopwatch, comprising a hammer-fulcrum, a hammer mounted rotatably on said hammer-fulcrum and having an integral hammer spring and two integral acting surfaces one of which has flexibility with respect to the remainder of said hammer, two essentially heart-shaped cams, each mounted rotatably on its own cam-fulcrum and disposed to coact with one of said acting surfaces when said return mechanism is actuated, said acting surfaces being at essentially equal distances from said hammer-fulcrum, and said cam-fulcrums being at essentially equal distances from said hammer-fulcrum, whereby the forces exerted by said acting surfaces against said cams during actuation will be essentially equal, and a pin so disposed as to press against said hammer spring and urge said hammer away from said cams, the shape of said hammer-spring being such that the force exerted by said spring is near maximum during the first portion of said actuation, decreases during a further portion of said actuation and rises during the last portion of said actuation.

Claims

1. A return mechanism for a chronograph or a stopwatch, comprising a hammer-fulcrum, a hammer mounted rotatably on said hammer-fulcrum and having an integral hammer spring and two integral acting surfaces one of which has flexibility with respect to the remainder of said hammer, two essentially heartshaped cams, each mounted rotatably on its own cam-fulcrum and disposed to coact with one of said acting surfaces when said return mechanism is actuated, said acting surfaces being at essentially equal distances from said hammer-fulcrum, and said cam-fulcrums being at essentially equal distances from said hammer-fulcrum, whereby the forces exerted by said acting surfaces against said cams during actuation will be essentially equal, and a pin so disposed as to press against said hammer spring and urge said hammer away from said cams, the shape of said hammer-spring being such that the force exerted by said spring is near maximum during the first portion of said actuation, decreases during a further portion of said actuation and rises during the last portion of said actuation.