Abstract A zigzag sewing machine is disclosed which can exchangeably accommodate any one of a variety of differently organized special cam units for producing special patterns of zigzag stitches, zigzag stitch patterns combined with patterned work feed control, or closed stitch groups such as buttonholes. A novel cam unit for buttonholing is disclosed which may be selectively clutched to the cam shaft while maintaining a constant position lengthwise on the cam shaft. The cam unit for buttonholing is additionally novel in the provision of a clutch mechanism which can be overrun manually at will as for positioning the unit to start but which cannot be overrun by the back pressure of the follower which tracks the cam unit.
An exchangeable pattern cam unit for a sewing machine having a driven camshaft with a cam unit reception seat, said exchangeable pattern cam comprising a hub portion complimental to said reception seat for exchangeable accommodation thereon into and out of rotationally interlocked relation with said driven camshaft, a cam disc member freely rotatable on said hub portion, selectively engageable clutch means on said hub portion and on said cam disc including a clutch engagement controlling element carried on said cam disc and accessible exteriorly thereof, and a manually rotatable handle member interlocked rotationably with said cam disc member.
Claim 2
Dependent Claim
98 words
An exchangeable pattern cam unit for a sewing machine having a driven camshaft with a cam unit reception seat, said exchangeable pattern cam comprising a hub portion complimental to said reception seat for exchangeable accommodation thereon into and out of rotationally interlocked relation with said driven camshaft, a cam disc member freely rotatable on said hub portion, selectively engageable clutch means on said hub portion and on said cam disc including a clutch engagement controlling element carried on said cam disc and accessible exteriorly thereof, and a manually rotatable handle member interlocked rotationably with said cam disc member.
Claim 3
Dependent Claim
46 words
A pattern cam unit as set forth in claim 1 in which said selectively engageable clutch means comprises ratchet teeth formed on said hub portion and a pawl shiftably supported on said cam disc for movement into and out of interlocked relation with said ratchet teeth.
Claim 4
Dependent Claim
44 words
A pattern cam unit as set forth in claim 2 in which said ratchet teeth are formed substantially rectangular in form with pawl-engaging suRfaces at each side extending substantially radially of said hub, and in which said pawl includes a substantially rectangular ratchet-engaging extremity.
Claim 5
Dependent Claim
104 words
A pattern cam unit as set forth in claim 3 in which said manually rotatable handle member is interlocked rotationally with said cam disc member by means of a projection extending from one of said members and accommodated in a clearance aperture formed in the other of said members providing for lost motion of said handle member relatively to said cam disc member, and pawl-engaging means on said handle member for shifting said pawl out of interlocked relation with said ratchet teeth during the lost motion of said handle member relatively to said cam disc upon turning of said handle member in one direction.