Sewing machine

Abstract: According to the invention, since the axis (L3) of a needle (38) is inclined with respect to an imaginary plane perpendicular to the axis (L2) of a lower shaft (28), the lowermost position of the needle (38) where it comes closest to a loop taker (30) is spaced from the loop taker (30) in the axial direction thereof in proportion to the degree of inclination of the axis (L3) of the needle (38). As a result, the length of a bobbin (61) accommodated in the loop taker (30) can be extended along the axis (L2) thereof, thereby permitting the amount of bobbin thread loaded on the bobbin (61) to be increased. At this time, the amount of needle thread drawn by the needle thread take-up may remain the same as in the previous construction and need not be changed, which serves to eliminate the problems such as thread breaking or difficulty of thread cast-off.

Description: The invention relates to a sewing machine including a lower shaft, having a horizontal rotation axis and supporting a looptaker, in which is mounted a bobbin having thread wound thereon, and a needle mounted for reciprocal motion toward and away from said looptaker in synchronism with rotation of said lower shaft, said needle and said bobbin being mounted such that the needle axis intersects a plane containing an axial end of the bobbin at an acute angle. Such sewing machine is known from EP-A-0,288,612. In this known machine the reciprocal motion of the needle takes place in the vertical direction, perpendicular to the rotation axis of the lower shaft. The bobbin, however, is inclined relative to the rotation axis of the lower shaft. This arrangement permits the increase of the amount of thread to be loaded onto the bobbin. It is an object of the invention to provide an improved sewing machine of the above described type, while retaining the increased thread take up capacity of the bobbin, used therein. This object is achieved by providing a sewing machine in which the needle axis is inclined at an acute angle to an imaginary plane extending perpendicular to the axis of said lower shaft and intersects said axis under an acute angle. The tilting of the needle over an acute angle (1) from the vertical position into an inclined position permits the tilting of the axis of the bobbin over the same acute angle so that this axis coincides with the horizontal rotation axis of the lower shaft. This relative position of the needle axis and the axis of the bobbin allows for maintaining the advantage of increasing the amount of thread to be loaded on the bobbin as described in EP-A-0,288,612. The inclined position of the needle further reduces the vibrations of that needle and allows the upper needle drive shaft to be made shorter, thereby reducing also the vibrations of that shaft. These and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken with reference to the drawings, wherein: Fig.1 is a perspective view of a sewing machine according to an embodiment of the invention; Fig.2 is a cross-sectional view of a horizontal axis full rotary loop taker mounted on such sewing machine; Fig.3 is an enlarged view of a loop seizing beak and adjacent parts thereof; Fig.4 is an enlarged view, illustrating the distance of shifting of the point of a needle installed in such sewing machine. Referring now to the drawings, a preferred embodiment of the invention is described below. Fig.1 is a perspective view of a sewing machine 20 according to the invention, and Fig.2 is a cross sectional view of a horizontal axis full rotary loop taker 30 mounted on the sewing machine 20. The sewing machine 20 includes a horizontal bed 21 and a main body 22 mounted on the bed 21. The main body 22 is provided with an upper shaft 23 which is driven to rotate about a horizontally extending axis L1. To the upper shaft 23 is fixed a bevel gear 24 which engages with a bevel gear 26 fixed to one end of an interlocking shaft 25 that is driven to rotate about the vertically extending axis thereof. Fixed to the other end of the interlocking shaft 25 is a bevel gear 27 which engages with a bevel gear 29 fixed to one end of a lower shaft 28. The lower shaft 28 is driven to rotate about a rotation axis L2 lying in a vertical plane containing the rotation axis L1 of the upper shaft 23, the axes L1 and L2 being parallel with each other. A horizontal axis full rotary loop taker 30 is mounted on the other end of the lower shaft 28. On one end of the upper shaft 23 is mounted a pulley or wheel 32 on an outer circumferential surface of which a V-shaped groove 31 is formed. A needle thread take-up cam 33 is fitted to the other end of the upper shaft 23. The take-up cam 33 is provided with a needle thread take-up link 34 and a crank shaft 35 mounted concentrically with the take-up link 34. The thread take-up link 34 is connected to a needle thread take-up 36 such that the needle thread take-up 36 is moved up and down in reciprocating fashion. Fitted to the crank shaft 35 is one end of a connecting rod 37. A needle holder 39, in which a needle 38 is detachably fitted, is fixed to the other end of the connecting rod 37. The needle holder 39 is inserted through an aperture 41 formed in a guide member 40 fixed to the main body 22. An axis L3 of the needle 38 is inclined toward the take-up cam 33 at an angle of 1, in a plane containing the rotation axes L1 and L2 of the upper and lower shafts 23 and 28, with respect to a vertical line L4 that lies in an imaginary plane perpendicular to the rotation axis L2 of the lower shaft 28. The angle 1 is, for example, 3 to 10 degrees. The handwheel 32 is driven for rotation with a V belt 44 extending from a driving source (not shown) and fitted around the V-shaped groove 31. When the handwheel 32 is rotated, the upper shaft 23 is rotated about its rotation axis L1, thereby moving the needle thread take-up 36 and the needle 38 up and down in reciprocating fashion. The rotation of the upper shaft 23 is transmitted via the interlocking shaft 25 to the lower shaft 28 so that the lower shaft 28 is rotated about its rotation axis L2. In the thus constructed sewing machine 20, the upper shaft 23 and the lower shaft 28 have parallel axes lying in the same vertical plane, and the needle 38 reciprocates up and down in such a way as to space itself away from a bobbin 61 hereinafter described, with its path of travel inclined at an angle of 1 with respect to the vertical line L4. In the full rotary loop taker 30 mounted on the sewing machine 20, there is provided a hook-body 50 which includes a hook body shell 51 and a mounting member 52. The mounting member 52 is secured to the lower shaft 28 having the horizontally extending axis of rotation L2. A gib 53 is fixed to the hook body shell 51 to form a hook groove 54 which extends circularly in an imaginary plane perpendicular to the rotation axis L2 of the lower shaft 28. On the outer circumferential surface of a bobbin case holder 55 is formed a bobbin case holder rib 56 which engages with the hook groove 54 to support the bobbin case holder 55 in the hook body 50. The hook body 50 further includes a loop seizing beak 57 and a spring 58. A protrusion on a rotation restraining member (not shown) fixed to the sewing machine body engages with a rotation restraining notch 59 formed on the bobbin case holder 55, to prevent the rotation of the bobbin case holder 55 while the hook body 50 is being driven for rotation about the rotation axis L2 of the lower shaft 28. A bobbin case 62 housing a bobbin 61 is mounted in a cavity 60 of the bobbin case holder 55. The bobbin 61 includes a barrel 65 of a right cylindrical shape having a center hole 64 through which a stud 63 is inserted, and a pair of flanges 66 and 67 which are fitted to opposite ends of the barrel 65. Thread 68 is wound on the bobbin 61 through the center hole 64 of which is inserted the stud 63 extending at right angles from the bottom 69 of the bobbin case holder 55. The axis of the stud 63, and thus the axis of rotation of the bobbin 61, is concentric with the rotation axis L2 of the lower shaft 28. The needle 38 reciprocates up and down in directions shown by arrow 70, the lowermost point of the path of travel of the needle 38 being indicated by reference numeral 71. The lowermost point 71 of the needle 38 is determined so that the needle does not strike the flange 67. Referring to Fig.3, an end portion 80 of the loop seizing beak 57 formed on the hook body 50 has an end face 81 formed parallel to the reciprocating path of the needle 38, i.e., to the axis L3 of the needle holder 39. The end face 81 therefore forms an acute angle 2 with the axis L2 of the lower shaft 28. (see Fig. 5) The angle 2 is, for example, 80 to 87 degrees. When the needle 38 enters a needle guide 82 in the bobbin case holder 55, the end face 81 of the loop seizing beak 57 is substantially parallel to the path of travel of the needle 38. Also, if the point of the needle 38 strikes an inclined face 82b of the needle guide, the needle 38 will be guided into the needle guide 82 by such inclined face 82b. Fig.4 is a diagram explaining the distance of shifting of the point P1 of the needle 38 in the sewing machine 20. When compared with the needle 7 of the aforementioned prior art arrangement, the needle 38 of the invention is inclined at an angle of 1 with respect to the vertical line L4, or 2 with respect to the rotation axis L2 of the lower shaft 28. The point P1 of the needle 38 is shifted from the point P0 of the needle 7 by a horizontal distance s. When the difference in vertical height between the point P0 and the point P1 where the needle 7 and the needle 38 are at their respective lowermost points is denoted as h, the distance s is given by equation (1) or (2) below. s = h·tan 1 s = h/tan 2 With the path of travel of the needle 38 thus inclined by angle 2 to the rotation axis L2 of the lower shaft 28, the length of the bobbin 61, i.e. the axial length of the barrel 65 on which the thread 68 is wound with the flanges 66 and 67 fitted to opposite ends thereof, can be extended by the distance s, thereby permitting the amount of the thread 68 on the bobbin to be increased. Also, since the upper shaft 23 can be made shorter, it is possible to reduce the vibration of the upper shaft 23. Furthermore, since the needle 38 is moved in an inclined direction, the vibration of the needle 38 is reduced.

Claims: A sewing machine, including a lower shaft (28), having a horizontal rotation axis (L2) and supporting a looptaker (30), in which is mounted a bobbin (61) having thread (68) wound thereon, and a needle (38) mounted for reciprocal motion toward and away from said looptaker (30) in synchronism with rotation of said lower shaft (28), said needle (38) and said bobbin (61) being mounted such that the needle axis (L3) intersects a plane containing an axial end (67) of the bobbin (61) at an acute angle, characterized in that the needle axis (L3) is inclined at an acute angle (1) to an imaginary plane (L4) extending perpendicular to the axis (L2) of said lower shaft (28) and intersects said axis (L2) under an acute angle (2).

Inventors: HIROSE TOKUZO, HIROSE, TOKUZO
Applicants: HIROSE MFG CO LTD, HIROSE MANUFACTURING COMPANY LIMITED
Application year: 1991
Main classification: D05B57
IPC codes: D05B57, D05B55