Patent Application
20130068145
1. Field of the Invention
This invention relates to a sewing machine, more particularly to a sewing machine with a thread holding device for holding a required amount of needle thread remaining on a sewing needle.
2. Description of the Related Art
A conventional electronic sewing machine generally includes a plurality of thread guides, such as a needle thread regulating member, a guide frame, a take-up spring, a thread take-up lever, a needle-bar thread guide, and the like, where a needle thread extending from a spool is passed through a predetermined threading path. The needle thread is then passed through an eye of a needle. Subsequent to a thread cutting procedure, the thread take-up lever is swung upward to its top dead center to move the needle bar away from a needle plate. At that point, the needle thread may be pulled out of the needle eye by the upward moving the thread take-up lever, so that manually rethreading the needle is necessary, which is very troublesome.
An object of the present invention is to provide a sewing machine which has a thread holding device for holding a required amount of needle thread remaining on a sewing needle.
According to this invention, the sewing machine includes a sewing head, a needle bar mounted on the sewing head to be reciprocally movable upward and downward, and having a needle-bar thread guide, a thread take-up lever mounted on the sewing head and upwardly of the needle bar to be swung upward and downward in synchronization with the needle bar, and having a lever threading portion which is disposed upstream of the needle-bar thread guide in terms of a threading path of a needle thread, a thread guide frame mounted on the sewing head and between the needle bar and the thread take-up lever, and a thread holding device including a first disc, a second disc, an electromechanical unit, and a biasing member. The first disc is fixed to the thread guide frame, and has a first holding surface which faces the threading path and upstream of the needle-bar thread guide. The second disc is movable relative to the first disc between holding and releasing positions, where the second disc is closer to and remote from the first disc, respectively, and has a second holding surface which confronts and cooperates with the first holding surface to define a thread holding clearance so as to permit passage of the needle thread therethrough such that, in the releasing position, the needle thread is permitted to continue on running from the lever threading portion to the needle-bar thread guide, and such that, in the holding position, the needle thread is arrested from moving along the threading path. The electromechanical unit is disposed to be actuated to thrust the second disc to the holding position. The biasing member is disposed to bias the second disc toward the releasing position.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which:
Referring to
Referring to
Referring to
The second disc 40 is movable relative to the first disc 30 between holding and releasing positions, where the second disc 40 is closer to and remote from the first disc 40, respectively, and has a second holding surface 411 which confronts and cooperates with the first holding surface 311 to define a thread holding clearance (S) so as to permit passage of the needle thread 300 therethrough. Thus, in the releasing position, as shown in
In this embodiment, the thread holding clearance (S) has an upper region (S1) which is defined by upper portions 32, 42 of the first and second discs 30, 40 and which is configured to be divergent upwardly so as to facilitate entry of the needle thread 300 into the thread holding clearance (S).
The electromechanical unit 10 includes a housing 11 and an electromagnetic solenoid unit 12 mounted in the housing 11. The housing 11 is secured to the thread guide frame 250 and defines an accommodation chamber 111 which extends axially to terminate at an end wall 112 that is attached to the first disc 30 and that has a plunger hole 115 in spatial communication with the accommodation chamber 111. The plunger hole 115 is aligned with the plunger holes 33, 43 in the first and second discs 30, 40. The electromagnetic solenoid unit 12 includes a plunger 122 having a plunger end 125 which extends through the plunger holes 115, 33, 43. A washer 123 is sleeved on the plunger end 125, and a screw nut 124 is threadedly engaged with the plunger end 125 so as to tighten the second disc 40 between the washer 123 and the screw nut 124. Thus, the plunger end 125 is movable axially toward the plunger hole 115 to displace the second disc 40 to the holding position. The electromagnetic solenoid unit 12 further includes a solenoid member 121 activated to move the plunger 122 and thrust the second disc 40 toward the holding position.
The biasing member 60 is in the form of a coil spring 60 which is sleeved on the plunger 122 and which abuts against the solenoid member 121 and the washer 123 so as to bias the second disc 40 away from the solenoid member 121 toward the releasing position.
Further, a movement guiding shaft 113 is disposed to extend axially from the end wall 112 and is parallel to the plunger 122 so as to extend through the shaft holes 34, 44 of the first and second discs 30, 40 to guide the axial movement of the second disc 40. A stop ring 114 is disposed on the movement guiding shaft 113 for limit the axial movement of the second disc 40.
According to this embodiment, when the cutting operation of the needle thread 300 is performed, the needle thread 300 can be clamped with the clamping force in the thread holding clearance (S) which is disposed between the lever threading portion 241 and the needle-bar thread guide. Hence, the needle thread 300 extending between the thread holding clearance (S) and the needle 270 stands still to prevent the needle thread 300 from being pulled out of an eye of the needle 270. Thus, a required amount of the needle thread remaining, such as that having 5-10 cm in length, on the needle 270 can be secured even when the thread take-up lever 240 is moved up to its top dead center. Moreover, the configuration of the upper region (S1) defined by upper portions 32, 42 of the first and second discs 30, 40 is divergent upwardly so as to facilitate manual introduction of the needle thread 300 into the thread holding clearance (S). Furthermore, by virtue of the rib and mating groove regions 312, 412 and the roughened second holding surface 411, the needle thread 300 can be clamped firmly with the clamping force and the friction in the thread holding clearance (S).
While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.
