US2781012A - Thread cutters for sewing machines - Google Patents

Description

Feb. 12, 1957 1.. J. KUHAR THREAD CUTTERS FOR SEWING MACHINES Filed June 23, 1954 IN VEN TOR.

Ludwig J Kuhar ATTORNEY United States Patent THREAD CUTTERS FOR SEWING MACHINES Ludwig J. Kuhar, Clark Township, N. 1., assignor to The Singer Manufacturing Company, Elizabeth, N. .L, a corporation of New Jersey Application June 23, 1954, Serial No. 438,775

4 Claims. (01. 112-452 This invention relates to sewing machines and more particularly to a thread cutter especially adapted for severing the needle and bobbin threads after the termination of a sewing operation, and one of the primary objects of the invention is to provide an improved device of this class.

Another important object of the invention is to provide an improved thread cutter that can be manufactured with the minimum of cost and effort.

With these and other objects in view, as will hereinafter appear, the invention consists in the devices, combinations and arrangements of parts described in connection with the accompanying drawings, which illustrate a preferred embodiment of the invention and in which:

Fig. 1 is a fragmentary perspective view of a sewing machine embodying the invention;

Fig. 2 is an enlarged view of a portion of the presserbar bushing shown in Fig. 1; and

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2.

Referring in detail to the drawings, the illustrated embodiment of the invention is shown as applied to a familytype sewing machine of the type fully disclosed in United States Patent No. 2,617,375, issued November 11, 1952. The present drawings illustrate portions of the sewing machine, including a bed 16 to which there is hinged an extension plate 17. The bed 16 is cut away and thereby receives a throat-plate 18 which is held to the bed 16 by screws 1919. A presser-foot 21, of Well known construction, is positioned above the throat-plate 18 and is pivotally supported on the lower end of a resser-foot shank 22, the upper end of which is held to the lower end of a resser-bar 23 by means of a thumb screw 24. The presser-bar 23 is supported for longitudinal movement in a resser-bar bushing or tubular member 27, which, in a well-known manner, is supported in and extends below the lower end of a bracket-arm head 28. The head 28 also supports a reciprocable needle-bar and needle indicated generally by the numeral 29.

The bushing 27, as best seen in Fig. 2, is in the form of a right cylindrical tube and thus provides a tubular wall 31 having an inner cylindrical surface 32 and an outer or external cylindrical surface 33. The base of the bushing is in a plane that is at right angles to the axis of the bushing 27. The wall 31 surrounds a bore 34, which is the bore in which the presser-bar 23 is movably mounted. The upper end of the bushing 27 has a shoulder 36 and the lower end of the bushing 27 is provided with an inclined thread-receiving slot 37 cut downward and inward toward, but not into, the bore 34 of the bushing. The slot 37 base bottom 38, a lower arced edge 41, and an upper arced edge 42. Reference to Fig. 2 shows that the slot 37 is positioned in the wall 31 of the bushing 27 in such a manner that the two ends of the slot 37 are at unequal distances from the bottom of the bushing 27, the upper end of the slot being indicated by the numeral 43, and the lower end of the slot being indicated by the numeral 44. By reference to Fig. 1, it will be noted that 7 2,781,012 Patented Feb. 12, 1957 the lower end 44 of the slot 37 is located substantially in line with the line of feed of the sewing machine and that 'ice the upper end 43 of the slot is substantially in line with p the end of the bracket-arm head 28. In other words, the slot 37 subtends an are, measured circnmferentially of the bushing 27, of substantially ninety degrees Reference to Fig. 3 shows that the sides of the slot 37 define parallel planes which intersect, at an angle of approximately sixty degrees (60), a plane defined by the end or base of the bushing 27, the last named plane being normal to the longitudinal axis of the tubular bushing 27 Reference to Fig. 2 shows that the bottom 38 of the slot 37 defines a line which intersects the plane, defined by the end or base of the bushing 27, at an angle of approximately thirty degrees (30). This positioning of the slot 37 has been found to be especially advantageous when the slot is used to cut or sever the needle and bobbin threads at the termination of the sewing operation. Furthermore, the slot 37 opens only to the external surface 33 of the bushing 27 and is not cut deep enough to intersect the inner surface 32 thereof. This arrangement prevents lint or other dirt which may collect in the slot 37 from interfering with the operation of the presser-bar 23.

The low cost of providing the thread cutter slot 37 in the bushing 27 is of considerable importance. first place, the bushing 27 is a standard part of the sewing machine and would be supplied as a necessary component of the machine whether the thread cutter was furnished or not. In the second place, the only operation that is required in providing the thread cutter is the forming of the slot 37 by one saw out prior to finishing the external surface 33 of the bushing 27. The grinding operation, which is normally performed to provide the proper outside diameter for the bushing 27, sharpens the thread- cutting edges 41, 43 and 44 of the slot 37.

In operation, the thread cutter is used in the following manner. At the completion of a seam the upper and lower threads (not shown) are drawn out sufiiciently sothat they are long enough to reach the bushing 27 above the slot 37. Then the threads are manually pulled against the side of the bushing 27 at a level above the threadreceiving slot 37, following which a downward pull on the threads causes them automatically to enter the threadreceiving slot. Then a downward pull is exerted on the threads and one or more of the cutting edges 41, 43 and/or 44 cut the threads.

Having thus set forth the nature of the invention, what I claim herein is:

1. A sewing machine comprising a bed, a bracket-arm head overhanging said bed, and a right cylindrical member supported from and extending below the lower end of said bracket-arm head, said member being provided toward its lower end with a thread-cutting slot cut into the member from the outer cylindrical surface thereof, said slot having a closed bottom that defines a line which intersects a plane normal to the longitudinal axis of the member at an angle of approximately thirty degrees (30).

2. A sewing machine comprising a bed, a bracket-arm head overhanging said bed, and a right cylindrical member supported from and having an outer surface extending below the lower end of said bracket-arm head, said member being provided toward its lower end with an upwardly open, downwardly extending thread-cutting slot cut into the member from the outer cylindrical surface thereof, the sides of said slot defining parallel planes which intersect a plane normal to the longitudinal axis of the member at an angle of approximately sixty degees (60).

3. A sewing machine comprising a bed, a bracket-arm head overhanging said bed, and a member supported from and extending below the lower end of said bracketarm head, said member being provided with a thread- In the cutting slot cut into the member from the outer surface thereof, said slot having a closed bottom that defines a line which intersects a plane normal to the axis of the member at an angle of approximately thirty degrees (30) and the sides of said slot defining parallel planes which intersect a plane normal to the axis of the member at an angle of approximately sixty degrees (60).

4. A sewing machine comprising a bed, a bracket-arm head overhanging said bed, a member supported from and having an outer surface extending below the lower end of said bracket-arm head, said member being provided with References Cited in the file of this patent UNITED STATES PATENTS 280,970 Staples July 10, 1883 1,251,352 De Voe Dec. 25, 1917 2,558,039 Carrol] June 26, 1951

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