Safety lockout system for sewing machines

Abstract

This disclosure relates to means for preventing the reciprocating needle of a sewing machine from operating in a zig-zag mode when a straight stitch throat plate means is positioned on the work bed surface. A latching means is provided for selective interconnection between the zig-zag jogging mechanism and the needle mechanism with said latching means being responsive to movement of the presser mechanism for unlatching the latching means. A locking mechanism is also provided to lock the latching mechanism in an unlatched position.

Description

BACKGROUND OF THE INVENTION

This invention relates to a safety lockout mechanism for preventing a sewing machine from operating in a zig-zag mode when a throat plate means is present on the work bed surface which is capable of receiving only reciprocation of the needle in a straight stitch mode. As is known in the art during zig-zag stitching the needle of the sewing machine is moved laterally or from side to side while at the same time reciprocating up and down with respect to the throat plate which is supported on the work bed surface of the sewing machine. In order to accommodate the side to side or lateral movement of the sewing machine needle a zig-zag throat plate is provided which has an enlarged aperture formed to accommodate the maximum lateral movement of the needle during zig-zag stitching. During straight stitch operation however the throat plate is not provided with such an enlarged aperture but is only provided with a sufficiently large aperture to accommodate the needle during its substantially straight line reciprocation whereby maximum support of the work on the work bed is provided. It will be apparent that, if a straight stitch throat plate is present on the work bed surface when the machine is placed in a zig-zag mode, the needle will protion(now U.S. Pat. No. 3,926,133) wherein there is described both a mechanical type jogging mechanism and one of the electromagnetic type with an example of circuit means for centering the actuator. In addition to the aforementioned means for insuring that the pin 38 is in a proper position for coupling, according to the present invention as described above, the pin 46 on the coupling member 48 is always maintained within the slot 44 in the pin 48, even during uncoupling. When the coupling member is elevated in response to the cam member 58, the cam portion or cam surface 50 on the coupling member 48 will engage an inner surface of the slot 44 and cam the pin 38 and link 36 into the center position so that the cylindrical portion 52 of the coupling member 48 may now pass into the slot 44 for completing the coupling engagement. Thus, it will be seen, that irrespective of the last position of the actuator 34 and the link 36 prior to a reinitiation of a zig-zag mode, the construction of the coupling member 48 in combination with the size and shape of the slot 44 in the pin 38 will always insure that the coupling member 48 will be received in said slot 44 for coupling the respective elements together.

If it is now desired to change from the zig-zag mode to the straight stitch mode, it will be necessary to raise the presser mechanism control lever 80 to lift the presser foot in the usual manner and exchange the zig-zag throat plate 18a for a straight stitch throat plate 18. As explained above upon lifting the control member 80 the needle bar release cam lever is pivoted along with the cam member 58 so that the cam member 58 no longer urges the coupling member 48 into coupling engagement and thus permits the spring 56 to urge the coupling member 48 in a direction so that it is not in positive engagement with the pin 38 and the rocker bracket 42. At this time the jogging mechanism will be effectively disconnected from the needle bar mechanism so that upon turning the machine on no zig-zag motion of a needle will be produced. In order to insure that the mechanism remains in the straight stitch mode, that is, with the needle constrained in alignment with the throat plate needle hole as shown in FIG. 2 by abutment of the cam member 58 against the needle bar bracket 26, and that no zig-zag motion is produced, a locking means is provided for locking the latching mechanism including the cam member 58, the needle bar release cam member 64 and coupling member 48 into an unlatched position. The locking means or mechanism includes a tooth 88 on the latching pawl 70 which is disposed for engagement in the slot 68 in the pawl receiving cylinder 66. The latching pawl 70 is pivotally supported on a bracket member 90 which along with the bracket member 78 is suitably fixed to the machine frame. As best shown in FIG. 1, it will be seen that the pivot point of the latching pawl 70 is substantially at its mid-point and that a spring 92 is connected adjacent the end of the latching pawl 70 opposite from the tooth 88 which spring 92 is fixed at its other end to the bracket 78 for urging the latching pawl in a clockwise pivotal direction or towards a position for engagement with the slot 68 in the pawl receiving cylinder 66. Therefore, when the control lever 80 is elevated to pivot the needle bar release cam lever to its substantially vertical position, as illustrated in FIG. 1, the slot 68 in the pawl receiving cylinder 66 will rotate to a position wherein the tooth 88 of the latching pawl will drop into said slot 68. Upon return of the control member 80 to its vertical position the pin 86 on the link 84 will now leave the surface of the needle bar release cam lever 64 but the needle bar release cam lever will now be locked into its vertical position wherein the cam member 58 is ineffective for urging the control member 48 into coupling engagement. Therefore it will be seen that whenever the presser bar mechanism control lever 80 is raised the latching mechanism will be positioned for uncoupling the jogging mechanism from the needle bar mechanism and the locking means will lock the latching mechanism in the unlatched position.

In order to unlock the locking mechanism and return the elements of the latching mechanism to a position wherein zig-zag motion may be reinstituted, means are provided in response to a change in the throat plate to unlock the locking mechanism. The aforementioned means comprises a solenoid 94 which is suitably fixed to the bracket 90 and is disposed adjacent the latching pawl 70 and is coupled therewith so that upon actuation of the solenoid 94 the armature will exert a force on the rear portion or the portion opposite to the tooth 88 and initiate a counter clockwise motion in opposition to the force of spring 92 which will thereby uncouple the tooth 88 from the slot 68 in the pawl receiving cylinder 66 and permit the needle bar cam release lever to return to its substantially horizontal position under exertion of the spring 72 and consequently pivot the camming member 58 into a position for urging the coupling member 48 into coupling engagement with the jogging mechanism and the needle bar mechanism. Energization of the solenoid 94 is brought about by actuation of a switch member 96 positioned in the work bed 14 and directly underneath a portion of the work bed surface wherein the throat plate is received. The switch 96 includes a plunger 98 which acts to permit the switch 96 to move to a closed position when the plunger is in a raised position and acts to move the switch 96 to an open position when lowered. As seen in FIG. 2, the zig-zag throat plate 18a is provided with a cut-out portion or an opening 100 which when a zig-zag throat plate is in position on the work bed surface 16 permits the plunger 98 of the switch 96 to raise and as a result the switch 96 will close and energize the solenoid 94. The straight stitch throat plate 18 as shown in FIG. 1 does not have such an opening and when such throat plate 18 is in position on the work bed surface 16 the plunger 98 will be depressed and thereby move the switch 96 to an open position so that the solenoid 94 is not energized.

The operation of the invention is substantially as follows. Assuming the sewing machine to be turned on and a zig-zag mode selected, if it is necessary to change the throat plates from a straight stitch throat plate to a zig-zag throat plate. The presser mechanism control lever 80 is raised whereupon, as explained above the latching mechanism will be positioned for uncoupling the jogging mechanism from the needle bar mechanism and the locking means will be in a position for locking the latching mechanism in the unlatched position. Upon removal of the straight stitch throat plate 18 and insertion of the zig-zag throat plate 18a the plunger 98 in the switch 96 will be permitted to raise whereupon the solenoid will be energized to unlock the locking mechanism. However, as the control lever 80 of the presser bar mechanism is still in an elevated position the latching mechanism will still be physically locked in the unlatched position. However upon return of the control lever 80 to its lowered position for lowering the presser foot into a work engaging position, the control lever 80 will be removed from its position of urging the needle bar release cam lever into an unlatching and will permit said cam lever 64 to return to its substantially horizontal position wherein the camming member 58 is pivoted for urging the coupling member 48 into coupling engagement with the jogging mechanism and the rocker bracket 42. If it is now desired to change to a straight stitch mode of stitching, the control lever 80 of the presser bar mechanism is again raised wherein the latching mechanism will be held by said control lever through link 84 and pin 86 in an unlatched condition. The zig-zag throat plate 18a is now removed and a straight stitch throat plate 18 inserted therefor. When the straight stitch throat plate 18 is inserted it will depress the plunger 98 of the switch 96 to open the switch 96 and inactivate the solenoid 94. With the solenoid 94 inactive, the tension in spring 92 will cause the latching pawl member to pivot so that the tooth 98 on the latching pawl 70 will drop into slot 68 of the pawl receiving cylinder 66 for locking the latching mechanism in the unlatched condition. Now upon return of the control lever 80 to a position wherein the presser foot is lowered for engaging the work surface the latching mechanism will be locked by the locking mechanism into an unlatched position so that movement of the actuator 34, if any, will not be transmitted to the rocker bracket 42 and the needle bar mechanism.

It will be seen from the above description that elevation of the presser bar mechanism will move the latching mechanism into an unlatched position each time the control lever 80 thereof is raised and will physically hold the latching mechanism in such position. A locking mechanism is also provided for insuring that the latching mechanism will be locked in the unlatched position whenever a straight stitch throat plate is present. As initially pointed out herein, one advantage of the invention lies in the fact that, when the machine is in a straight stitch mode, the zig-zag mechanism is completely uncoupled from the needle bar mechanism and that no restraining means are required for restraining the zig-zag mechanism from initiating any zig-zag movement during such straight stitch mode. Obviously this eliminates any strain on the elements of the zig-zag mechanism of the sewing machine and should contribute substantially to their operating life. Further, the latching mechanism is responsive to movement of the presser bar mechanism which is normally raised and lowered during changes between the zig-zag mode and the straight stitch mode so that the invention takes advantage of a normal operation of the operator during sewing to initiate an unlatching of the zig-zag mechanism upon selection of a straight stitch mode.

While the invention has been described in detail in its preferred embodiments, it will be understood by those skilled in the art that various modifications and changes may be made therein without departing from the spirit and scope of the invention as described in the appended claims.

Claims

1. In a sewing machine having a frame, a needle bar disposed for endwise reciprocation in said frame, a needle bar jogging means for selectively initiating relative lateral movement of said needle bar for producing zig-zag stitches whereby the sewing machine is operable in straight stitch and zig-zag modes, a work engaging presser mechanism including control means for selectively lifting said presser mechanism away from a work engaging position and lowering said presser mechanism toward a work engaging position, and means operatively connecting said presser mechanism with said jogging means for disabling said jogging means and for constraining said needle bar in a predetermined straight stitch position in response to actuation of said presser mechanism control means.

2. In a sewing machine as recited in claim 1 wherein said means operably connecting said presser mechanism with said jogging means includes latching means for latching said jogging means with said needle bar and said latching means being responsive to movement of said presser mechanism such that upon selective movement of presser mechanism control means to a first position movement of said latching mechanism is initiated for unlatching said jogging means from said needle bar.

3. In a sewing machine as recited in claim 2 wherein said latching means is biased toward a position for latching said jogging means to said needle bar and said presser mechanism control means being effective upon movement to said first position for overcoming the bias of said latching means.

4. In a sewing machine as recited in claim 3 wherein said latching means includes a coupling member operative for coupling said jogging means and said needle bar, said coupling member being biased toward a position for uncoupling said jogging means and said needle bar, a camming member disposed for engagement with said coupling member and said camming member being biased toward a position for urging said coupling member to couple said jogging means and said needle bar.

5. In a sewing machine as recited in claim 4 further comprising locking means for locking said camming member in position when said control means is moved to said first position whereby said coupling member will be uncoupled from said jogging means and said needle bar.

6. In a sewing machine as recited in claim 5 wherein said locking means includes a pawl disposed for engagement with said camming means, said pawl being biased toward a position for positively latching said camming means, and release means for overcoming the bias on said pawl thereby permitting said camming means to move to a position for urging said coupling member to couple said jogging means and said needle bar.

7. In a sewing machine as recited in claim 6 further comprising a work bed surface, throat plate means disposed on said work bed surface and including means for receiving the needle during straight stitch and zig-zag stitch modes of needle operation, switching means responsive to the presence of said throat plate means during one of the straight stitch or zig-zag modes of needle operation, and said release means being responsive to said switching means for enabling release of said pawl from said camming means.

8. In a sewing machine as recited in claim 3 further comprising locking means for locking said latching means in position after movement of said latching means in response to movement of presser mechanism control means to said first position.

9. In a sewing machine as recited in claim 8 further comprising release means for releasing said locking means from said latching means, and said release means being operative only when said sewing machine is in one of the zig-zag or straight stitch modes of stitching.

10. In a sewing machine as recited in claim 9 wherein said release means is operative only in response to a selection of a zig-zag mode of stitching.

11. In a sewing machine having a frame, a needle bar supporting a needle and disposed for endwise reciprocation in said frame, jogging means for initiating relative lateral shifting of said needle bar for producing zig-zag stitches, a work bed surface on the sewing machine, throat plate means disposed on said work bed surface and including means for receiving the needle when in a straight stitch mode or a zig-zag mode, latching means for latching said needle bar with said jogging means, and selectively operable locking means for rendering said latching means unlatched and constraining said needle in axial alignment with said means for receiving the needle when in a straight stitch mode, electromagnetic means operably associated with said locking means and operable in response to the presence of said throat plate means when in one of the straight stitch or zig-zag modes including means for receiving the needle when in a straight mode for locking said latching means in an unlatched position such that upon actuation of said locking means said jogging means will be disconnected from said needle bar whereby the sewing machine will operate in a straight stitch mode.

12. In a sewing machine as recited in claim 11 wherein said jogging means includes a needle bar jogging member connected to said needle bar, an actuator member disposed for coupling engagement with said jogging member, said actuator member being operable for transmitting jogging motion to said jogging member, and said latching means including a coupling member for coupling said actuator member to said jogging member.

13. In a sewing machine as recited in claim 12 further comprising a presser mechanism for holding the work on said work surface and including control means for selectively lowering and lifting said presser mechanism toward and away from said work surface, and said control means being operative when said presser mechanism is lifted for disengaging said coupling member from said actuating member and said jogging member.

14. In a sewing machine as recited in claim 13 wherein said locking means is operative for locking said coupling member in a disengaged position.

15. In a sewing machine as recited in claim 14 wherein said coupling member is biased toward a position for uncoupling said actuating member from said jogging member and said latching mechanism includes camming means connected to said coupling member and being operative for urging said coupling member into coupling engagement with said actuating member and said jogging member.

16. In a sewing machine as recited in claim 15 wherein said locking means comprises a cam latching pawl, said cam latching pawl being biased toward a position for locking said camming means in a position wherein said camming means in ineffective for urging said coupling member into coupling engagement with said actuator member and said jogging member, and an electromagnetic actuator disposed in operative relationship with said cam latching pawl such that upon energization of said electromagnetic actuator said cam latching pawl is urged into a position for unlocking said camming means.

17. In a sewing machine as recited in claim 16 further comprising switching means disposed in operative association with said throat plate means and said electromagnetic actuator and said throat plate means further including means for activating said switching means when said means for receiving the needle is in one of the straight stitch or zig-zag modes.

18. In a sewing machine as recited in claim 17 wherein said throat plate means comprises first and second throat plate members interchangeable with each other on the work bed surface, and one of said first and second throat plate members including said means for activating said switching means such that when said one throat plate member is disposed on said work bed surface said electromagnetic actuator will be actuated for urging said cam latching pawl to unlock said camming means.

19. In a sewing machine as recited in claim 18 wherein said one throat plate member includes aperture means for receiving reciprocation of the needle when said needle is in the zig-zag mode.

20. In a sewing machine as recited in claim 18 wherein the other of said throat plate members includes aperture means for receiving reciprocation of the needle when said needle is in the straight stitch mode, and said other throat plate member being ineffective for activating said switching means.