GB2125992A

GB2125992A - Watch movement

Info

Publication number: GB2125992A
Application number: GB08224396A
Authority: GB
Inventors: Joseph Rinaldi; Paul Wuthrich
Original assignee: Timex Corp
Current assignee: Timex Group USA Inc
Priority date: 1982-08-25
Filing date: 1982-08-25
Publication date: 1984-03-14
Also published as: GB2125992B

Abstract

A thin movement for a stepping motor watch employs a single frame member comprising a peripheral front frame portion 2a surrounding and connected to a back frame portion 2b and a stepping motor stator 10 affixed to the frame member. Pins 19-21 fixed in the back frame portion 2b, and a rotor pin 10a fixed in the stepping motor stator, rotatably mount gear members 13, 16, 17, 18 for driving the watch hands. A timepiece dial 4 is supported on the front frame portion 2a and serves to control axial movement of the gear members on the pins, as well as of stepping motor rotor 10 on pin 10a. Only two layers of gear members are required in the space between the back frame portion 2b and the dial 4. <IMAGE>

Description

SPECIFICATION Watch movement This invention relates generally to movements for timepieces, and particularly to a thin movement suitable for a stepping motor watch of the quartz analogue type.

The known employment of an integrated circuit, a quartz crystal timebase, and a stepping motor driving the timepiece hands has already reduced the number of components in analogue wristwatches and has offered opportunities for simplifying construction and reducing the number of components. A very thin wristwatch also offers improved aesthetic values and flexibility in design.

Any timepiece with rotatable members, such as a stepping motor rotor, gear train and an hour and minute wheel assembly carrying timepiece hands, must maintain proper axial clearance of the rotatable members so that they will neither bind nor have excessive axial play. The axial movement of the rotatable members is sometimes known as "endshake" and its proper control in high-volume, mass-produced timepieces is vital to successful control of the manufacturing process and timepiece quality.

Accordingly, one subject of the present invention is to provide an improved movement for a timepiece, with improved means for controlling the endshake of the rotatable members included in such movement.

Briefly statedsthe invention provides a timepiece movement comprising a single frame member with a peripheral front frame portion connected to and at least partially surrounding a back frame portion, said front and back frame portions having surfaces disposed in parallel spaced planes, a plurality of pins having one end fixed in said back frame portion and the other end terminating substantially in the plane of the front frame portion surface, a plurality of gear members mounted on said pins, a dial disposed on the front surface and contacting the terminating ends of said pins and limiting the axial movements of said gear members on the pins.

An additional pin may be used in a stepping motor stator to support the stepping motor rotor, which may also have its endshake controlled by the dial.

An embodiment of a timepiece movement according to the present invention will now be described by way of example, reference being made to the accompanying drawings in which: Figure 1 is an exploded perspective view of the timepiece movement, and Figure 2 is a developed partial horizontal cross section of the movement.

Referring now to Figure 1 of the drawings, the major components shown are a stepping motor assembly 1, a single piece frame member 2, a train of rotatable gear members 3, a timepiece dial 4, and timepiece hands 5. The electronic components are arranged on a circuit board 6. Not shown in the drawing are the timepiece case, which may be of conventional construction, push button switches to actuate the electrical circuitry for setting the timepiece, and a button-sized energy cell to provide power.

The stepping motor assembly 1 comprises a coil 7, a front stator member 8, a permanent magnet rotor and pinion assembly 9, a back stator member 10, a rotor pin 1 Oa and screws 11, 12 which securely attach the stator members 8, 10 to the frame member 2. The rotatable gear train 3 includes an hour wheel 1 3 with attached sleeve 14, a minute wheel 1 5 with attached sleeve 1 6 arranged to fit coaxially within sleeve 14, a third wheel gear and pinion assembly 17, and an intermediate gear and pinion assembly 1 8.

The frame member 2 is stamped from a single sheet of metal and comprises a peripheral front frame portion 2a connected to and at least partially surrounding a back frame portion 2b. The front and back frame portions 2a, 2b are formed with top surfaces disposed in spaced parallel planes. The front frame portion includes notches 2c disposed to receive tabs 4a on the dial 4 which permit the dial to be affixed to the frame member 2, as the movement is assembled, by bending the tabs 4a on the dial beneath the frame member.

The dial 4 also includes a central hole 4b and time indicating markers 4c.

The rotatable gear members of train 3 are journaled upon non-rotatable or fixed pins, which include a centre post 19, and pins 20 and 21 supporting the third wheel assembly 1 7 and the intermediate wheel assembly 1 8 respectively. The pins 20, 21, and centre post 1 9 are fixed securely at one end in the back frame portion 2b of the frame member 2. The other ends of pins 1 Oa, 20, 21 terminate in the plane which contains the top surface of the front frame portion 2a, while the centre post 1 9 projects above this plane. It remains to note that the hour wheel 1 3 includes an annular ridge 1 3a which cooperates with the underside of dial 4 to control endshake as will be explained.

Referring now to Figure 2 of the drawings, a developed partial elevation drawing in crosssection illustrates the principle of construction and operation of the improved thin movement for a stepping motor timepiece. When the timepiece is assembled, the stepping motor assembly 1 is attached to the single piece frame member 2 from the rear with screws 11, 12 as indicated, with the stepping motor rotor pin 1 0a having a terminating free end disposed in the plane of the upper surface of the front frame portion 2a.

The third wheel and intermediate wheel gear and pinion assemblies 1 7 and 1 8 are assembled from the front of the movement on pins 20, 21 and the hour and minute wheel assemblies 13, 14, 15, 1 6 are assembled on the centre post 19, again from the front of the movement. Dial 4 is affixed to the front frame portion 2a and contacts the ends of pins 20, 21, 1 Oa. Since the spacing between the dial 4 and the back frame 2a (or stator 10) is now accurately set, the endshake for axial movement of the stepping motor rotor and pinion assembly 9 and the third wheel and intermediate gear assemblies 17, 1 8 are accurately controlled.

In the case of the coaxially mounted hour wheel and minute wheel sleeves 14, 1 6, the endshake or axial movement of the two assemblies is controlled by the ridge 1 3a on hour wheel 13, which forms close clearances with the dial. Since the hour wheel is a very slow moving wheel, the friction induced by this contact is negligible.

It is important to note also that the resulting gear train arrangement has no more than two layers of gear members in the space between the back frame portion and the dial. Therefore, an extremely thin movement is possible which is simple to assemble and yet with assurance of accurate endshake control.

Claims

1. A timepiece movement comprising a single frame member having a peripheral front frame portion connected to and at least partially surrounding a back frame portion, said front and back frame portions having surfaces disposed in parallel spaced planes, a plurality of pins each having one end fixed in the frame back portion and the other end terminating substantially at the front frame portion surface plane, a plurality of gear members rotatably mounted on said pins, and a dial for the timepiece supported on the front frame surface portion and contacting the other ends of said pins and controlling the axial movements of said rotatable gear members on said pins.

2. A movement according to Claim 1, including a stator member for a stepping motor affixed to said frame member and carrying a fixed stator pin having a free end terminating at the front frame portion surface plane, and a stepping motor rotor disposed on said pin, whereby the axial movement of the stepping motor rotor is controlled by said dial.

3. A movement according to Claim 1, including a centre post affixed at one end to the back frame portion and projecting through a hole defined in the dial, and coaxial hour and minute wheel assemblies rotatably mounted on said centre post, said hour wheel defining an annular ridge adapted to form close clearances with the dial to thereby control endshake of the hour and minute wheel assemblies.

4. A movement according to Claim 1, wherein said dial and said back frame portion define therebetween a space containing the rotatable gear members, said gear members comprising no more than two layers of gears disposed in said space, whereby the thickness of the movement may be minimised.

5. A movement according to Claim 1, wherein said frame member comprises a single metal stamping.

6. A movement according to Claim 1, including a stepping motor comprising a stator carrying a pin supporting a motor rotor, and further including a centre post rotatably supporting coaxial hour and minute wheel assemblies, said rotor, said gear members and said hour and minute wheel assemblies all being adapted to cooperate with said timepiece dial to control endshake.

7. A movement for a thin timepiece of the type having a stepping motor with a rotor driving timepiece hands through an intermediate gear train, said movement comprising: (a) a single stamped metal frame member having a peripheral front frame portion connected to and at least partially surrounding a back frame portion, said front and back frame portions having surfaces disposed in parallel spaced planes, (b) a stepping motor stator affixed to said frame member and having a stator pin affixed at one end to the stator and terminating in the front frame surface plane, (c) a plurality of pins affixed at one end in the back frame portion and having ends terminating in the front frame surface plane, (d) an intermediate gear and pinion assembly disposed on one of said pins and adapted to be driven by the rotor, (e) a third wheel gear and pinion assembly disposed on another of said pins meshing with and adapted to be driven by the intermediate gear and pinion assembly, (f) a centre post having one end affixed in the back frame portion and extending past said plane, (g) coaxial minute wheel assembly and hour wheel assembly meshing with and driven by said third gear and pinion assembly, and (h) a dial disposed on the front frame portion and affixed thereto and defining a centre hole to receive the centre post, said dial contacting the free ends of said pins and controlling endshake of the stepping motor rotor, the intermediate gear and pinion assembly and the third gear and pinion assembly.

8. A movement according to Claim 7, wherein said hour wheel has an annular ridge thereon adapted to form close clearances with said dial to thereby control the endshake of the hour wheel and minute wheel assemblies.

9. A timepiece movement substantially as hereinbefore described with reference to the accompanying drawings.