Handwheel clutch for sewing machines

A handwheel clutch for a sewing machine having a bistable tiltable element for engaging or disengaging the clutch thereby coupling or decoupling the handwheel from the arm shaft.

DESCRIPTION 
BACKGROUND OF THE INVENTION 
This invention relates to combination handwheels and handwheel clutches for 
sewing machines and, more particularly, to a handwheel clutch that may be 
decoupled from the arm shaft of a sewing machine by light manual pressure 
on a tiltable member associated with a handwheel. In a typical sewing 
machine, a handwheel is provided which is coupled to both an electric 
drive motor and to the arm shaft by a clutching device. In many instances, 
a bobbin winder is provided which is driven by frictional contact with the 
handwheel. Since the arm shaft drives all of the other mechanisms in the 
sewing machine it is desirable to declutch the handwheel from the arm 
shaft when winding thread on a bobbin. Prior art handwheel clutches tend 
to detract from the aesthetic appearance of the sewing machine and are 
frequently composed of many highly precision parts resulting in a complex 
and costly mechanism. 
It is therefore an object of this invention to provide a handwheel 
declutching mechanism wholly contained within the interior of the 
handwheel to preserve the aesthetic appearance of the sewing machine. 
It is another object of this invention to provide a handwheel declutching 
mechanism of simple construction, few parts, that is relatively 
inexpensive to manufacture and maintain. 
Other objects and advantages of the invention will become apparent through 
reference to the accompanying drawings and descriptive matter which 
illustrate a preferred embodiment of this invention. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a sewing machine 
having an arm shaft, a handwheel, and a drive means for rotating the 
handwheel. A clutch means is provided for drivingly coupling the handwheel 
to the arm shaft. The clutch means comprises a drive notch formed in the 
handwheel and a driving element supported on a segment of the arm shaft 
for rotation therewith. The driving element is arranged to tilt between 
each of two bistable positions. When in the first bistable position, the 
driving element is in driving engagement with the drive notch and when in 
the second bistable position, the driving element is out of driving 
engagement with the drive notch. 
The driving element comprises a substantially planar yoke having a pair of 
flexible members each joined at one extremity to the yoke and arranged 
with their free extremities facing each other and spaced apart a 
predetermined distance. Means is provided for interlocking the yoke on the 
arm shaft or rotation therewith. Diametrically opposed reception seat 
surfaces are formed on the arm shaft and are spaced apart a distance which 
is greater than the predetermined distance between the the free 
extremities of the flexible members. The yoke is assembed on the arm shaft 
with the free extremities of the flexible members arranged in engagement 
with a respective one of the diametrically opposed reception seat 
surfaces. The flexible members are each flexed to a position on an 
opposite side of the plane of the yoke. Means is provided for interlocking 
the yoke with the arm shaft for rotation therewith when the free 
extremities of the flexible members are in engagement with the reception 
seat surfaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 through 4, there is shown a sewing machine 2 having an 
arm shaft 4 with a handwheel 6 rotationally supported thereon. The 
handwheel 6 is free to rotate on the diameter 8 of the arm shaft 4 and is 
retained between the shoulder 10 and the snap ring 12. A bobbin winder 
mechanism shown generally at 20 is of conventional construction having a 
friction wheel 22 which may be placed in frictional engagement with the 
surface 24 of the handwheel 6 for rotational driving thereby. During the 
normal sewing operation, the friction wheel 22 is out of engagement with 
the surface 24 as shown in FIG. 1. A drive belt 30 rotationally couples 
the handwheel 6 to a drive motor, not shown. 
Referring to FIG. 4, there is shown an exploded perspective view of the 
component parts comprising the handwheel clutch assembly. A pair of 
parallel grooves, or reception seat surfaces, 40 are formed in a segment 
of the arm shaft 4 normal to the axis and adjacent the snap ring groove 
11. Two diametrically opposite and substantially parallel flats 52 are 
formed on the end 50 of the arm shaft 4 normal to the pair of grooves 40. 
The handwheel 6 has a hollow interior 60 and a shoulder 62 formed on the 
inner wall thereof. A series of drive notches 64 are equally spaced about 
the shoulder 62 each having a drive surface 66 that is substantially 
parallel to the axis of the arm shaft 4. A driving element, generally 
shown at 70, comprises a yoke 72 having a drive tap 82 formed normal 
thereto, two inwardly projecting stop members 72 having opposing face 
surfaces 76, and two inwardly projecting flexible members 78 having free 
extremities 80 facing each other. The two opposing face surfaces 76 are 
spaced apart so that they will slidingly engage the pair of flats 52 of 
the arm shaft 4. With the surfaces 76 in engagement with the pair of flats 
52, the drive element 70 is rotationally coupled to, or interlocked with 
the arm shaft 4 and must rotate therewith. 
The two opposing free extremities 80 of the flexible members 78 are spaced 
apart a predetermined distance that is slightly smaller than the distance 
between the pair of grooves 40. The extremities 80 may be formed with a 
small turned edge or lip, as shown in FIG. 4. This lip, however, should 
seat well into the groove 40 yet permit sufficient movement so that the 
drive element 70 may be tilted between the bistable position shown in FIG. 
1 and that shown in FIG. 2. The driving element 70 is disposed on the arm 
shaft so that the two opposing free extremities 80 interferingly engage 
the pair of grooves 40 and the two stop members 74 slidingly engage the 
pair of flats 52, as shown in FIG. 3. Each flexible member 78 is flexed to 
a position on an opposite side of the plane of the yoke 72. That is, the 
yoke 72 is assembled on the arm shaft 4 with one flexible member 78 flexed 
in a direction away from the end 50 of the arm shaft 4 and the other 
flexible member 78 flexed in a direction toward the end 50. This 
positioning of the two flexible members 78 in opposite directions causes 
the distance between the two facing extremities 80 to become greater so 
that the extremities 80 will embrace the pair of grooves 40. This will 
cause the yoke 72 to tilt with respect to a plane containing the two 
grooves 40 into a first bistable position. By applying manual pressure to 
the drive element 70, thereby causing it to tilt in the opposite 
direction, the two flexible members 78 will reverse their positions: the 
one that was flexed toward the end 50 will now be flexed away from the end 
50 and the other that was flexed away from the end 50 will now be flexed 
toward the end 50 thereby causing the yoke 72 to tilt into a second 
bistable position. The two extremities 80 are always in engagement with 
the grooves 40, thereby retaining the driving element 70 on the arm shaft 
4. Additionally, since the two opposing face surfaces 76 of the stop 
members 74 are always maintained in sliding engagement with the pair of 
flats 52, the driving element 70 is interlocked with the arm shaft so that 
one must rotate with the other in each of the bistable positions. If the 
torque requirements of the sewing machine are not prohibitively large, the 
stop members 74 may be eliminated. In this case the free extremities 80 
seating in the grooves 40 perform the interlock function thereby 
preventing relative rotation between the yoke 72 and the arm shaft 4. 
Referring now to FIG. 4, an actuating plate 90 made of a suitable plastic 
material, has molded therein a long boss 92 and a short boss 94. Each boss 
has a molded extension 96 which lockingly engages a pair of mounting holes 
98 formed in the driving element 70. This actuating plate 90 is included 
in the interest of operator safety and is not necessary for the successful 
practice of this invention. As can be seen in FIG. 1, the length of the 
bosses 92 and 94 are such that the actuating plate 90 is substantially 
square with respect to the handwheel 6 when the end 82 of the driving 
element 70 has engaged the drive notch 64. This is its normal position 
when sewing. 
In operation, the operator will depress the actuating plate 90, tilting it 
into its second bistable position, as shown in FIG. 2, wherein the end 82 
is out of engagement with the drive notch 64 thereby rotationally 
decoupling the handwheel 6 from the arm shaft 4. With the driving element 
70 in this position the friction wheel 22 of the bobbin winder 20 may be 
engaged with the surface 24 of the handwheel 6 for winding the bobbin 
without effecting rotation of the arm shaft. When the winding operation is 
completed the bobbin winder 20 is disengaged from the surface 24 and the 
actuating plate 90 is returned to its first bistable position. 
As can be seen, the driving element 70 is of unitary construction thereby 
providing a unique and extremely simple clutch structure. With this 
arrangement the component parts are economical to manufacture and 
extremely simple to assemble. The important and unique features of this 
invention are manifested in the biastable driving element having flexible 
members which engage the arm shaft for biasing the driving element in 
either of the two bistable positions. 
Upon reviewing the present disclosure a number of alternative constructions 
will occur to one skilled in the art. Such constructions may utilize 
variations in the driving element 70 such as a single flexible member 78 
or variations in other components of the present invention. These 
constructions however are considered to be within the spirit and scope of 
this invention.