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 switch means responsive to the presence of more than one needle automatically puts the machine into a multiple needle mode of operation.

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 filed on Jan. 8, 1974 now patent #3,984,749, now U.S. Pat. No. 3,984,749 and assigned to the same assignee as the present invention for a more detailed description of the linear actuator. Disposed within the bed 12 and below the needle bar 22 for operation in association therewith is a needle plate 34 which includes a needle aperture 36 having a width sufficient to at least accommodate a single needle during maximum width zig-zag motion. Supported beneath the bed plate 12 is a feed mechanism for feeding the work across the surface of the bed plate and includes a feed dog 38 operably connected with suitable linkage generally indicated at 40 which in turn is connected to a second linear motor or actuator 42. As described in co-pending application Ser. No. 596,683 filed July 16, 1975 now U.S. Pat. No. 4,016,821 output line 60 rheostat 58 of the digital-to-analog converter 52. 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 a 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 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 have an effect on a reduced value 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.

Referring to FIGS. 4 and 4a, as shown therein the switch means 110 may be carried in association with the needle bar mechanism and cooperates with the needle holder so that when more than one needle is inserted into the needle bar the desired resistance will be automatically placed in the circuit. As shown in FIG. 4a, the switch 110 supported by a switch block 118 may be carried by the needle bar 22. The switch 110 includes a fixed contact 110a and a movable contact 110b supported on a flexible member, as illustrated. A collar member 120 is disposed around and in sliding relationship with the needle bar 22 and a frame member comprising a pair of depending legs 122 is fixed to the collar 120 for movement therewith. The legs 22 terminate in a bent portion 124 or form an aperture or passageway 125 through which the shank of a single needle or the post of a twin or multiple needle holder may pass without interference. However, the width of a twin or multiple needle holder will be greater than the width of passageway 125 and will abut the portion 124 during insertion thereof and cause the collar 120 to slide upwardly on needle bar 22 to close switch 110 as shown in FIG. 4a. The collar 120 is normally biased away from switch 110 by a spring 126 connected to a post 128 in collar 120 and to a fixed post 130 on the needle bar clamp 132. When a single needle is inserted, (FIG. 4) the shank will pass through passageway 125 without interfering with the bent portion 124 of the frame member so that collar 120 will not be raised in opposition to spring 126 and switch 110 will remain open. When a multiple needle is inserted, (FIG. 4a) the plurality of needles 26 will be wider than passageway 125 so that full insertion of the multiple needle will raise the frame member in opposition to spring 126 to close switch 110 and thereby automatically insert resistance 116 into the circuit for limiting the bight, as described above.

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 in an electronically controlled sewing machine for automatically modifying the 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 embodiment, it will be obvious to those 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 including a housing, an endwise reciprocable needle bar means and needle means removably supported in said needle bar means for movement therewith, jogging means for initiating relative lateral movement of said needle bar means, electric motor means operatively connected to said jogging means such that initiation of the relative lateral movement of said needle bar means is controlled in accordance with movement of said electric motor means, means for generating electrical input signals in accordance with predetermined stitches in a plurality of selected patterns 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 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 bar means for any selected pattern will be limited and means responsive to the insertion of a needle means in said needle bar means for automatically actuating said switch means.

2. In a sewing machine as recited in claim 1 wherein said switch means includes switch components at least one of which is disposed for cooperation with said needle means for actuating said switch means.

3. In a sewing machine as recited in claim 1 further comprising a movable element supported for movement between a first position for actuating said switch means and a second position wherein said movable element is ineffective for actuating said switch means.

4. In a sewing machine as recited in claim 3 wherein said needle means comprises a plurality of needles and a holder for supporting said needles, and means on said holder disposed for cooperation with said movable element for initiating movement of said movable element to said first position.

5. In a sewing machine as recited in claim 3 wherein said movable element is supported on said needle bar means for movement relative to said needle bar means between said first and second positions.