Bight stop mechanism for sewing machines

Abstract

The present disclosure relates to zig-zag sewing machines including means for controlling the bight stops in order to produce ornamental patterns. In particular, the disclosure relates to electronically controlled sewing machines having storage means for storing stitch information and wherein logic means are used to select and release stitch information in timed relation with the operation of the sewing machine. The disclosure of the invention has particular application in those sewing situations wherein it is desired to use more than one needle in a single needle holder of the needle bar which therefore necessitates a limitation on the magnitude of the jogging or swinging of the needle bar in order to accommodate the multiple needles in the aperture of the needle plate. In accordance with the disclosure of the present invention whenever more than one needle is used in the sewing machine the electronic control of the bight stops is automatically put into effect whenever such multiple needle mode is selected.

Description

BACKGROUND OF THE INVENTION

In sewing machines it is desirable in some sewing situations to be able to use more than one needle as in the case, for example, of multicolored embroidery stitching. When substituting two or more needles for a single needle in a zig-zag machine, it becomes necessary to limit the swing amplitude of the needles, or the bight stops, as the two or more needles would swing in a wider path than a single needle which could take the needles out of the area covered by the aperture in the needle plate resulting in a breaking of the needles during penetration of the fabric. It is known to limit the bight stops in mechanically controlled zig-zag machines when substituting multiple needles for single needles, such as for example shown in U.S. Pat. No. 3,296,987 granted Jan. 10, 1967. In such mechanically controlled machines the zig-zag motion is generally imparted to the needle bar by a cam mechanism which is connected to the needle bar mechanism through a cam follower and associated linkage. In order to adjust or limit the bight stops in such machines means are generally provided for altering the linkage between the cam mechanism and the needle bar mechanism.

In electronically controlled sewing machines of the type disclosed in co-pending U.S. patent application Ser. No. 431,649 Preferably, the circuit is arranged such that when the switch 110 is open, the bight will be reduced for multiple needle sewing, and when the switch 110 is closed, a wider bight will be available for single needle sewing. It will be recalled, as discussed above, the digital-to-analog converter 52 puts out an analog signal which is converted from the digital information from the memory to provide a control signal for the bight in accordance with a selected pattern. In order to reduce the signal from the digital-to-analog converter 52, a fixed resistance in the form of a resistor 116 is placed in line 114 which resistor 116 has a resistance selected so that it will reduce the analog voltage from the digital-to-analog converter in an amount proportion to the number of needles, which in the case of switch 110 and its associated circuit in the preferred embodiment illustrated is selected for twin or two needle sewing. Thus, for example, the resistance of resistor 116 may be such to reduce influence the output from the digital-to-analog converter by an amount of 50%. It will be further seen that the parallel circuit containing switch 110 and resistor 116 is inserted into the circuitry prior to the application of any override or feedback signals, as would appear on line 70 subsequent to amplification of the bight control signal through bight signal control amplifier 62. Therefore, when the switch 110 is closed to insert the resistance 116 into the circuit any modification of the signal thereafter as through the override controls or the feedback would only could not have an effect on a reduced the maximum value of the control signal. By this means any modification of the bight control signal would not give rise to any concern that the swing amplitude of the needles would exceed the width of the needle plate aperture 36. It will also be understood, that instead of a single position switch 110 a multiple position switch may be provided wherein multiples of resistance may be inserted into the circuit in the same manner as the resistor 116 for situations wherein more than two needles will be used in the needle bar.

It will be seen from the above description that a novel and improved bight stop control mechanism is provided for a sewing machine for limiting the swing amplitude of a needle bar during zig-zag stitching when more than one needle is present in the needle bar. In particular, means are provided for modifying electronic bight control signals when the sewing machine is placed in a multiple needle mode to limit the swing amplitude of the needle bar so as to prevent any damage to the needles or the work or other elements of the sewing machine. While the invention has been described in its preferred embodiments, it will be obvious to one skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. In a sewing machine having endwise reciprocable needle means, jogging means for initiating relative lateral movement of said needle means, electric motor means connected to said jogging means such that initiation of the relative lateral movement of said needle means is controlled in accordance with movement of said electric motor means, means including first circuit means for generating electrical input signals in accordance with predetermined stitches in a selected pattern and for connecting said electrical input signals to said electric motor means, said electric motor means having a work output proportional to said electric input signals, and circuit means in addition to said first circuit means and including switch means for limiting the magnitude of the electrical input signals to said electric motor means, said circuit means being operative for reducing said electrical input signals a fixed percentage each time said switch is actuated whereby upon actuation of said switch means the maximum extent of lateral movement of said needle means will be limited.

2. In a sewing machine as recited in claim 1 further comprising override control means for selectively varying the magnitude of said electrical input signals, and said circuit means being operative to reduce said electrical input signals a fixed percentage irrespective of the selection of said override control means.

3. In a sewing machine as recited in claim 2 wherein said circuit means is operative for reducing said electrical input signals prior to any variation of said electrical input signals by said override control means.

4. In a sewing machine as recited in claim 1 wherein said electrical motor means comprises a reversible electric motor, said reversible electric motor being responsive to said electrical input signals for initiating relative lateral movement of said jogging means in first and second directions.

5. In a sewing machine as recited in claim 4 wherein said reversible electric motor comprises a linear motor.

6. In a sewing machine having a needle bar disposed for endwise reciprocation, said needle bar being adapted for supporting one or more needles for reciprocation therewith, jogging means responsive to electrical input signals for initiating lateral movement of said needle bar to produce patterned stitches with the magnitude of lateral movement of said needle bar being proportional to the magnitude of the electric input signals, pattern control means including first circuit means operative for supplying electrical input signals of predetermined magnitude to said jogging means, and circuit means in addition to said first circuit means and including switch means operatively connected to said pattern control means, said switch means being adapted for operation when more than one needle is supported by said needle bar for reducing the predetermined magnitude of the electrical input signals a fixed percentage of its original value supplied by said pattern control means.

7. In a sewing machine as recited in claim 6 wherein said circuit means includes resistance means, the value of said resistance means being selected in accordance with the number of needles supported by said needle bar.