Content .. 66 67 68 69 ..

Technology of watch production - part 68

The escape wheel is fed under the grinding wheels on the two spindles

by the rocking of the dividing head ( 1 0 ), mounted on the spindle head .

FIGURE 14. Kinematic diagram of the S-125A machine

The dividing head is indexed one division (one wheel tooth ) upon each

revolution of cam ( 7 ) through levers (8 ) and ( 9 ) . At the end of the machin

ing cycle , that is, when the one - tooth pinion

has rotated the wheel

z16

one

revolution, the stop (4 ) fitted on shaft III move s the lever ( 5 ) to the right,

and the microswitch switches off the electric moto r . This stops the machine .

Technical data, S-125A machine

Maximum diameter of the wheel machined, mm

. . .

1 5

Number o f teeth o n the wheel machined

. . . . . . . . .

Number of camshaft speeds

. . . . . . . . • .

•

. . . .

Range of camshaft speeds, rpm

. . . . . . . . •

. . . . . . .

24.7-32

Range of spindle speeds, rpm

• . . . . • • . •

. . . . . .

1150-4420

Electric motor .

. • .

•

. . . . . . • • •

. . . . . . . .

0.25 kw, 1 500 rpm

Time per cycle, sec

. • . . . . . . . . . . . . . . . • . . • .

6 .8-36.4

The impulse face and the locking face are accurately ground on the

S - 1 2 6A machine (Figure 1 5 ). The wheel is again located according to the
central hole.

The-surface finish quality of the two faces must be not poorer than

class 1 2 . One wheel is held on the mandrel at a tim e .

2 6 9

A n allowance of 0 . 0 1 mm is left on the diameter fo r the finish grinding.

The  two  faces  are  ground simultaneously by A z':'  abrasive  wheels .  The
wheel  shape  is  shown  in  Figure  1 6 .   No  burrs  are  formed  on the  tooth  edges
with this wheel  a rrangement.  The  diameter toleranc e  is  0 . 0 1  mm and the

permissible run- out is 0 . 005 rh m .

FIGURE 1 5 . General view o f the S-126A machine

Section A A

�t-

30°

....:

CO;

FIGURE 16. Finish grinding of the impulse face and the

locking face of escape-,vheel teeth

The kinematic diagram of the S - 1 26A m achine is given in Figure 1 7 .

The two - step pulley on the electric m otor drives the countershaft

means of round belts . Three- step pulleys are m ounted on the countershaft

driving the quill through round belts , and the camshaft II through a worm

and wheel . The cam shaft carries the one - tooth wheel

z1 ,

which controls

• [AZ is an abbreviation for the Russian A lmazoZamenitel' - diamond substitute. )

2 7 0

the automatic stoppage of the machine, and the cam ( 1 )

which rocks the

quill, that is, moves the grinding wheel toward and way from the wheel

being machine d .

The quill which carries the A Z grinding wheels i s periodically lowe red

unde r the action of rocking levers mounted on the auxiliary shaft III, and

grinds the impulse face and the locking face simultaneously (Figure 1 6 ).

f:IGURE

1 7 .

Kinematic diagram of the S-126A machine

Leve r (2 ), mounted on the auxiliary shaft, controls the dividing head.

It is indexed a given angle by the lever (4 ) and cam (1 ) . At the end of the
machining cycle the one- tooth wheel

z 1

has rotated the gear wheel

z16

one

full revolution, as was the case with the S- 1 2 5A machine, and the stop ( 3 )

s tops the machine .

Technical data, S -126A machine

Maximum diameter of the \vheel machined, mm . . . .
Number of teeth on the wheel machined

. . • . . . • • . •

Number of camshaft speeds . . . . . . . . . . . ,

. . . .

. .

Range of camshaft speeds, rpm

• . . . . . . . . . . . . . . .

Range of spindle speeds,

rpm . . . . . . . . . . . . . . . .

Electric motor

Time per cycle, sec . . . . . . . . . . . . . . . . . . . . . .

2 7 1

1 5

1 8 .2-85.5
1 150-4420

0.25 kw

rpm

10.5-49.5

Random inspection is carried out during each of the operations involved

in the machining of the escape wheel . In addition, the finished p roduct is
inspected l O O o/o for the basic parameters . The outside diameter, the tooth

p rofile and the circular pitch are inspected on a profile projector.

The run-out is inspected on an indicator instrument in a manner similar

to that in which modular gear wheels are inspected. The surface- finish

quality is inspected visually under plant conditions using a magnifying glass

with a magnification of 5X or l OX, or a microscope with a magnification

of 1 6 - 3 2X.

THE PALLET LEVER AND THE GUARD PIN

In the movements of pocket and wristwatches the pallet lever (Figure 1 8 )

receives impulses from the escape wheel through the interaction of the

pallets (pallet stones ) with the wheel teeth, and transmits the impulses to

the balance through the interaction of the pallet fork and the impulse pin

on the double roll e r (Figure 1 9 ).

FIGURE 18. Pallet lever

FIGURE 19. Impulse trans
mission

FIGURE 20. Strip layout for

blanking the pallet lever

To ensure correct escapem ent - balance interaction, the slots for the

pallet s tones and the hole for the impulse pin must not only be of accurate

width, but must also be correctly positioned relative to the axis of the fork

slot.

These slots are machined on special machines . The blank (Figure 2 0 )

i s punched out from a strip by a c ompound die with simultaneous contour

shaving (first operation ) .

The pallet lever has a complex asym metric contour and the clearances

between punch and die must be perfectly uniform . In o rder to obtain die

working surfaces of quality class 1 0 at least, one uses a s ectional die

(Figure 2 1 , a ) . The s till soft punch is b roached in the die set by the die,

and finish-ground in place after heat treatment. The die is of the s ectional

type and is made of three parts . The die entrance has a 0 . 05 mm radius

and is ground to a class-1 0 finish . The die is mounted in a ring (Figure 2 1 ,b),

2 7 2

Content .. 66 67 68 69 ..