Tension detector for string-like element

Claim 1

In a sewing machine for forming stiches with a string-like element and having means for terminating its operation in response to an electrical signal, a tension detector comprising: a support; a member mounted on the support for gravity biased movement from a first to a second position, without stop members, said member having an integral indicating portion having an opening permitting the passage of light and an integral portion for engaging the string-like element controlling the movement of the member in response to a lowered tensile condition of the element; a block mounted on the support with the indicating portion of the member normally between the support and the block, the block having a channel for slidingly receiving a photoelectric device from a separate to an operative position aligned with a hole extending from the photoelectric device through the block toward the support; and a light source mounted on the support in alignment with the photoelectric device and hole in the block for cooperation with the photoelectric device to provide an electrical signal only when the lowered tensile condition of the element permits movement of the member to the second position in which the opening is aligned with the light source and the photoelectric device.