Bobbin thread feeder of sewing machine

Abstract

The present invention provides a bobbin thread feeder of sewing machine of simple structure in which a lower thread can be reliably fed at an appropriate tension. A lower thread bobbin 21 can be removably contained through an opening for containing a lower thread bobbin 17 in a rotary hook 20 of a horizontal rotary hook 30 provided in a sewing machine frame. A thread tension plate and a thread tension spring are attached while overlapping along the inner circumference of the rotary hook 20, and function as a tension generating portion 22 for imparting resistance to pulling out a lower thread being guided through the gap between the thread tension plate and the thread tension spring. A needle plate 16 with an opening for taking the lower thread bobbin 21 in and out is provided above the rotary hook 20. The needle plate 16 comprises a guiding slit 27 that guides the lower thread formed thereon. The guiding slit 27 is formed substantially linearly in the extending direction of the overlapping portion of the thread tension plate and the thread tension spring.

Description

TECHNICAL FIELD[0001]The present invention relates to a bobbin thread feeder of sewing machine comprising a horizontal rotary hook that removably contains a lower thread bobbin, wherein a lower thread can be easily set during a sewing operation.BACKGROUND ART[0002]As sewing machines for household use, a model comprising a horizontal rotary hook in which a lower thread bobbin does not have to be contained in a bobbin case when being attached is becoming a mainstream instead of the one comprising a vertical rotary hook. In the case of sewing machines comprising a horizontal rotary hook, the lower thread bobbin need only to be set through an opening above the horizontal rotary hook into a rotary hook, and thus a bobbin thread feeder is provided so that a lower thread can be reliably fed.[0003]For example, in Patent Document 1, a bobbin thread feeder is consisted such that a containing portion of a rotary hook in the shape of a cylindrical container is positioned below an opening for co...

AI Technical Summary

Benefits of technology

[0013]According to the present invention, when the user moves the lower thread along the guiding slit on the upper face side of the rotary hook that contains the lower thread bobbin, the lower thread can be guided to the overlapping portion of the thread tension plate and the thread tension spring, and an appropriate tension is imparted to the lower thread. Accordingly, it is possible to provide a bobbin thread feeder of sewing machine that does not impair the function of feeding the lower thread by imparting an appropriate tension thereto even if a guide member is not additionally provided, only by a simple production process that forms a substantially linear guiding slit on the needle plate. Thus, production costs can be reduced because the number of parts is not increased.

Problems solved by technology

In the case where the sewing machine is operated in a state where the lower thread is not properly put through the tension generating portion, the feeding amount of the lower thread becomes excessive as the tension of the lower thread decreases, the balance with the upper thread is lost, and thus the sewing operation cannot be performed well.

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