Sewing machine
A controller of a sewing machine configured to execute a pre-positioning operation including controlling a needle bar driving mechanism, based on a thickness of a workpiece cloth detected by a thickness detection mechanism and a vertical position of a needle bar detected by a needle bar position detection mechanism, to stop a needle bar at a preset position immediately before a tip of a sewing needle pierces the workpiece cloth, controlling a pressure adjustment mechanism to adjust a pressure of a presser foot at a predetermined pressure that allows movement of the workpiece cloth, and controlling a feed dog switching mechanism to switch a feed dog to an inoperative state.
1. A sewing machine, comprising:
a needle bar;
a sewing needle attached to a lower end of the needle bar;
a needle bar driving mechanism that vertically moves the needle bar and that allows the needle bar to be stopped at a given position;
a needle bar position detection mechanism that detects a vertical position of the needle bar;
a bed;
a needle plate provided on the bed;
a presser foot that presses a workpiece cloth against the needle plate;
a pressure adjustment mechanism that adjusts a pressure exerted by the presser foot;
a thickness detection mechanism that detects a thickness of the workpiece cloth;
a feed dog that feeds the workpiece cloth;
a feed dog switching mechanism that switches the feed dog between an operative state in which the feed dog is moved above and below the needle plate and an inoperative state in which the feed dog stays below the needle plate;
a controller that controls the needle bar driving mechanism, the pressure adjustment mechanism, and the feed dog switching mechanism,
wherein the controller is configured to be capable of executing a pre-positioning operation including:
controlling the needle bar driving mechanism, based on the thickness of the workpiece cloth detected by the thickness detection mechanism and the vertical position of the needle bar detected by the needle bar position detection mechanism, to stop the needle bar at a preset position immediately before a tip of the sewing needle pierces the workpiece cloth,
controlling the pressure adjustment mechanism to adjust the pressure of the presser foot at a predetermined pressure that allows movement of the workpiece cloth, and
controlling the feed dog switching mechanism to switch the feed dog to the inoperative state.
2. The sewing machine according to claim 1 , further comprising an operation element that instructs the pre-positioning operation executed by the controller.
3. The sewing machine according to claim 2 , wherein the operation element comprises a needle height adjustment switch that switches the vertical position of the needle bar, and
wherein the controller, whenever the needle height adjustment switch is operated, controls the needle bar driving mechanism to switch the vertical position of the needle bar in a listed sequence of an upper position where the sewing needle is elevated, the preset position rendered by the pre-positioning control, and a lower position where the sewing needle pierces the workpiece cloth.
4. The sewing machine according to claim 1 , wherein a free motion mode can be set that allows the workpiece cloth to be manually moved in forming stitches, the setting of the free motion mode triggering automatic execution of the pre-positioning operation.
5. The sewing machine according to claim 1 , further comprising a presser bar that supports the presser foot, wherein the thickness detection mechanism includes a detector that detects a height of the presser bar when the presser foot is placed in contact with an upper surface of the workpiece cloth and
wherein the controller controls the feed dog switching mechanism to switch the feed dog to the inoperative state when detecting the thickness of the workpiece cloth by the detector.