Abstract
Hook (11, 12, 13, 14) for a lockstitch sewing machine, or parts of the hook such as the support element of the tension spring (in particular the basket or the bobbin case) or the tension spring itself, including a tension spring (80, 90, 100, 110, 120) that includes a bending towards the outside (with respect to the support element on which it is mounted and with respect to the main bending radius of the tension spring) of the tension spring's extremity designed to press on the bobbin thread, so that the pressure point (P) on the bobbin thread is the point of tangency between the bending radius (R) of the bending of the tension spring's extremity and the support element of the tension spring, so as to generate a stable tension of the bobbin thread.
Claims
1. A hook for a lockstitch sewing machine, comprising: a tension spring mounted on a support, said tension spring being bent with a main bending radius towards an inside of said support, a bobbin on which a bobbin thread is wound, and at least one of a bobbin case and a basket of the hook, wherein said tension spring comprises an extremity configured to press on the bobbin thread, said extremity having an outward bending radius towards an outside, with respect to the support on which the tension spring is mounted and with respect to said main bending radius of the tension spring, so that a point of pressure on said bobbin thread is a point of tangency between said outward bending radius of the tension spring and said support, so as to generate a stable tension of the bobbin thread.
2. The hook according to claim 1, wherein said tension spring further comprises an extension of the tension spring, in proximity of said extremity of the tension spring, wherein said extension is bent towards the outside with said outward bending radius.
3. The hook according to claim 1, wherein said outward bending radius of the extremity of the tension spring, is less than the main bending radius.
4. The hook according to claim 1, wherein said outward bending radius of the extremity of the tension spring is less than 2 mm.
5. A tension spring belonging to a hook for a lockstitch sewing machine, said tension spring comprising: a main bending radius towards an inside of the tension spring, an outward bending radius towards an outside, with respect to a support on which the tension spring is configured to be mounted and with respect to said main bending radius, wherein an extremity of the tension spring is designed to press on a bobbin thread, so that a point of pressure on said bobbin thread is a point of tangency between outward bending radius and said support of the tension spring.
6. The tension spring according to claim 5, wherein said tension spring further comprises an extension, in proximity of said extremity of the tension spring designed to press on the bobbin thread, and that said extension is bent towards the outside, with said outward bending radius.
7. The tension spring according to claim 5, wherein said outward bending radius of the extremity of the tension spring is less than the radius of the main bending radius.
8. The tension spring according to claim 5, wherein said outward bending radius of the tension spring is less than 2 mm.
9. The tension spring according to claim 5, further comprising the support of the tension spring belonging to a hook for a lockstitch sewing machine attached thereto.
10. The tension spring according to claim 5, further comprising a lockstitch sewing machine attached thereto.
11. The hook according to claim 2, wherein said outward bending radius of the extremity of the tension spring, is less than the main bending radius.
12. The tension spring according to claim 6, wherein said outward bending radius of the extremity of the tension spring is less than the main bending radius.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention will now be described with reference to exemplary embodiments, but not limiting, described in the attached figures, where:
(2) FIG. 1 shows schematically an exploded view of a central bobbin hook, complete with bobbin case, known;
(3) FIG. 2 shows schematically an exploded view of a rotary hook with horizontal axis, complete with bobbin case, known;
(4) FIG. 3 shows schematically an exploded view of a rotary hook with vertical axis, complete with bobbin case, known;
(5) FIG. 4 shows schematically an exploded view of a rotary hook with vertical axis, in the execution without bobbin case, known;
(6) FIGS. 5a-5c, 6a-6c and 7a-7c show some of the embodiments of the tension spring according to the state of the art;
(7) FIGS. 8a-8c, 9a-9c and 10a-10c show a kind of embodiment of the tension springs of FIGS. 5a-5c, 6a-6c and 7a-7c according to the invention, presenting a bending towards the outside (with respect to the support means on which it is mounted and with respect to the main bending radius of the tension spring), of the extremity of the tension spring, so that the pressure point on the bobbin thread is no longer the edge of the tension spring's sheet, but the point of tangency of the bending radius of said extremity;
(8) FIGS. 11a-11c and 12a-12c show a different embodiment of the tension spring of FIGS. 8a-8c according to the invention, in which the flat development of the tension spring's sheet is extended in the proximity of the tension spring's extremity designed to press on the bobbin thread, so as to make possible to bend such excess material with a bending radius towards the outside (with respect to the support means on which the tension spring is mounted and with respect to the main bending radius of the tension spring) and to leave unchanged the contact point of the tension spring with the bobbin thread. This different embodiment of the tension spring of FIGS. 8a-8c according to the invention, that considers to extend the flat development of the tension spring's sheet in proximity of the extremity of the tension spring designed to press on the bobbin thread, is easily achievable also for the other described embodiments of the tension spring, but the graphical representation is here omitted, as it would not be significantly different from FIGS. 9a-9c and 10a-10c;
(9) FIGS. 13a-13c show the mere detail in section along the section line A-A of FIGS. 5b, 8b, 11b of the point where the tension spring presses on the bobbin thread, by comparing a) the embodiment according to the state of the art in where the pressure point is on the edge of the sheet; b) the first embodiment according to the present invention in which the extremity of the tension spring is bent outwards generating a radius and moving back the point of pressure; c) the second embodiment according to the present invention in which the flat development of the tension spring has been extended so that when the additional material at the tension spring's extremity is bent towards the outside, the pressure point still remains the original one of the tension spring according to the state of the art.
DETAILED DESCRIPTION OF THE INVENTION
(10) In the attached figures, corresponding elements will be identified by the same numeral references.
(11) FIG. 1 shows schematically an exploded view of a central bobbin hook 11 with horizontal axis of rotation, known, in which only the elements relevant to the present description have been identified by numeral references: a hook body 2, comprising a well 18 in which the bobbin case 8 complete with bobbin 4 is housed; a support means of the tension spring, in this case a bobbin case 8 housed in the well 18 of the hook body 2, free to rotate inside of the hook body 2 and complete with latch slide 15 for the axial constraint of the bobbin case 8 on the hook body to prevent accidental disassembly during the sewing operation, and complete with the latch lever 16 that acting on the latch slide 15 allows the operator to disengage the slide 15, and herewith the bobbin case 8, from the axial constraint on the hook body 2 to allow the removal of the bobbin case, and complete with tension spring 9 to give tension to the bobbin thread (whose graphical representation is omitted) wound on the bobbin 4 which is inside the bobbin case 8; a bobbin 4, on which is wound the bobbin thread (not shown), is housed in the bobbin case 8 and is constrained within the hook body 2 by the mounting of the bobbin case 8 on the hook body 2.
(12) FIG. 2 shows schematically an exploded view of a rotary hook 12 with horizontal axis of rotation, known, in which are identified by numeral references only the elements relevant for the purposes of the present description: a hook body 2; a basket 6, free to rotate inside of the hook body 2 comprising: a well 18 of the basket 6 in which is housed the bobbin case 8 complete with bobbin 4; a support means of the tension spring, in this case a bobbin case 8 housed in the well 18 of the basket 6, complete with latch slide 15 for the axial constraint of the bobbin case 8 on the basket to prevent accidental disassembly during the sewing operation, and complete with the latch lever 16 that acting on the latch slide 15 allows the operator to disengage the slide 15, and herewith the bobbin case 8, from the axial constraint on the basket 6 to allow the removal of the bobbin case, and complete with tension spring 9 to give tension to the bobbin thread (whose graphical representation is omitted) wound on the bobbin 4 which is inside the bobbin case 8; a bobbin 4, on which is wound the bobbin thread (not shown), is housed in the bobbin case 8 and is constrained within the basket 6 by the mounting of the bobbin case 8 on the basket 6.
(13) FIG. 3 shows schematically an exploded view of a rotary hook 13 with vertical axis of rotation, known, in which are identified by numeral references only the elements relevant for the purposes of the present description: a hook body 2; a basket 6, free to rotate inside of the hook body 2 comprising: a well 18 of the basket 6 in which is housed the bobbin case 8 complete with bobbin 4; a lever 16 that allows the operator to disengage the bobbin case 8, from the axial restraint on the basket 6 to remove the bobbin case 8; a support means of the tension spring, in this case a bobbin case housed in the well 18 of the basket 6, complete with tension spring 9 to give tension to the bobbin thread (whose graphical representation is omitted) wound on the bobbin 4 which is inside the bobbin case 8; a bobbin 4, on which is wound the bobbin thread (not shown), is housed in the bobbin case 8 and is constrained within the basket 6 by the mounting of the bobbin case 8 on the basket 6.
(14) FIG. 4 shows schematically an exploded view of a rotary hook 14 with vertical axis of rotation, in execution without bobbin case, known, in which are identified by numeral references only the elements relevant for the purposes of the present description: a hook body 2; a support means of the tension spring, in this case a basket 6, free to rotate inside the hook body 2, comprising: a well 18 of the basket 6 in which is housed the bobbin 4, a lever 16 that allows the operator to disengage the bobbin 4 from the axial constraint on the basket 6 to allow the removal of the bobbin, and a tension spring 9 to give tension to the bobbin thread (whose graphical representation is omitted) wound on the bobbin 4; a bobbin 4, on which is wound the bobbin thread (not shown), housed inside the basket 6.
(15) FIGS. 5a-5c, 6a-6c and 7a-7c show different tension springs in the version according to the state of the art in a perspective view a) and in a side view b), with the detail c) zoomed and in section according to the axis A-A to highlight the pressure point P of the tension spring on the bobbin thread.
(16) The hook 11, 12, 13, 14 object of the present invention, comprises a tension spring, mounted on the basket or on the bobbin case, which creates a stable tension on the bobbin thread and independent as much as possible from the irregularities and from the characteristics of the thread.
(17) In a preferred embodiment of a hook 11, 12, 13, 14 according to the invention, described in FIGS. 8a-8c, 9a-9c and 10a-10c, the tension spring designed to create such a stable tension comprises a bending towards the outside (with respect to the support means on which it is mounted and with respect to the main bending radius of the tension spring) of the extremity of the tension spring, so that the pressure point is no longer the edge of the tension spring's sheet, but the point of tangency of the radius of said bending extremity of the tension spring. In this preferred embodiment, said bending radius of the tension spring's extremity is opposite to the main bending radius of the tension spring (which is bent towards the inside of the support means on which it is mounted), and is of very small size (typically of an order of magnitude less than the main bending radius of the tension spring).
(18) FIGS. 8a-8c, 9a-9c and 10a-10c show a first preferred embodiment of the present invention. In the version according to the state of the art, the tension spring (50, 60, 70) comprises an edge at its extremity, which generates the pressure point P on the bobbin thread. In the execution according to said first preferred embodiment of the present invention, the tension spring (80, 90, 100) comprises a bending towards the outside at its extremity, whose bending radius R is designed to press on the bobbin thread.
(19) FIGS. 11a-11c and 12a-12c show a second preferred embodiment of the present invention. As said, in the version according to the state of the art, the tension spring (50) comprises an edge at its extremity, which generates the pressure point P on the bobbin thread. In the version according to said second preferred embodiment of the present invention, the tension spring (110, 120) comprises an extension of the flat development of the tension spring's sheet, in the proximity of the extremity of the tension spring designed to press on the bobbin thread, so as to make possible to bend such excess material (111, 121) towards the outside (with respect to the support means on which the tension spring is mounted and with respect to the main bending radius of the tension spring) with a bending radius R and to leave unchanged the contact point of the tension spring with the bobbin thread. Quite evident corresponding extensions can be realized for the other embodiments of the tension spring according to the state of the art (60, 70), for which the representation is omitted.
(20) FIGS. 13a-13c show the mere detail in section along the section line A-A of the tension springs (50, 80, 110) of the previous FIGS. 5b, 8b, 11b of the point P where the tension spring presses on the bobbin thread, by comparing a) the embodiment of the tension spring 50 according to the state of the art where the pressure point is on the edge of the sheet; b) the first embodiment of the tension spring 80 according to the present invention in which the extremity of the tension spring is bent towards the outside generating a radius R and moving back the pressure point P with respect to the original one of the tension spring 50 according to the state of art; c) the second embodiment of the tension spring 110 according to the present invention in which the flat development of the tension spring has been extended so that when the additional material 111 at the tension spring's extremity is bent towards the outside, the pressure point remains in the same position as the original one of the tension spring 50 according to the state of the art. Entirely analogous considerations apply to other embodiments of the tension spring (60, 70).
(21) In another preferred embodiment, said bending radius R towards the outside of the tension spring's extremity, opposite to the main bending radius of the tension spring (which is bent towards the inside of the support means on which it is mounted), is of a very small size and is less than 2 mm.
(22) The hooks according to the invention, therefore, vary from those according to the state of the art (11, 12, 13, 14) only for the use of the tension spring (80, 90, 100, 110, 120) designed according to one of the preferred embodiments.
(23) Naturally, the invention is not limited to the particular embodiments previously described and illustrated in the attached figures, but it can be subject to numerous modifications of detail within the reach of a person skilled in the art, without departing from the scope of the invention itself, as defined in the appended claims.
