Pressure adjustment mechanism of sewing machine presser foot

Abstract

A pressure adjustment mechanism of the sewing machine presser foot comprises a motor, a screw actuated by the motor, a spiral spring and a pressing plate for pressing against an upper end of the presser foot. A nut is screwed and connected on the screw, and the nut is lifted or lowered by the screw. The pressing plate is underneath the nut. The circumferential direction of the nut is unfixed. The spiral spring is located between the nut and the pressing plate, an upper end of the spiral spring is pressed against the nut, and a lower end of the spiral spring is pressed against the pressing plate. The spiral spring is being compressed under the effects of the nut and the pressing plate.

Claims

1. A pressure adjustment mechanism for a presser foot of a sewing machine, comprising: a motor; a screw actuated by the motor; a spiral spring; a pressing plate capable of pressing against an upper end of the presser foot; and a nut being screwed and connected on the screw, the nut being lifted or lowered by the screw, and the pressing plate being underneath the nut; wherein the nut is unfixed in a circumferential direction, the spiral spring is located between the nut and the pressing plate, an upper end of the spiral spring is pressed against the nut, a lower end of the spiral spring is pressed against the pressing plate, and the spiral spring is being compressed under effects of the nut and the pressing plate; wherein the upper end of the spiral spring is fixedly connected to a metal pad, a center hole is disposed on the pad, the screw goes through the center hole of the pad, a lower side of the nut has a columnar limiting portion, the limiting portion is inserted into the center hole of the pad, and a limiting structure is disposed between the limiting portion and the pad, the limiting structure is capable of preventing the nut from turning in the circumferential direction relative to the pad.

2. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 1 wherein the lower end of the spiral spring is pressed against an upper side of the pressing plate, and, the lower end of the spiral spring and the pressing plate are unfixed in the circumferential direction.

3. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 2 wherein a lower side of the pressing plate has an inserting column for sleevely connecting with the upper end of the presser foot, the upper side of the pressing plate has a limiting column, and the lower end of the spiral spring is sleeved around the limiting column.

4. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 2 wherein an upper side of the pad is pressed against the lower side of the nut.

5. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 4 wherein the nut is made of plastic.

6. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 5 wherein the limiting structure comprises a plurality of limiting protruded portions disposing on a hole wall of the center hole, a plurality of axially disposed limiting grooves is disposed on an outer wall of the limiting portion, and the limiting protruded portions are engagedly connected in the limiting grooves.

7. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 5 wherein a sum of lengths of the limiting portion and the limiting column is larger than a length of the spiral spring when it is fully compressed.

8. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 5 wherein a shaft outer wall of the motor has an outer thread to form the screw, and a screw hole of the nut penetrates to a lower end face of the limiting portion.

9. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 1 wherein the pressure adjustment mechanism further comprises a sleeve; the nut, the spiral spring, and the pressing plate are disposed inside the sleeve; the motor is fixedly connected on an upper end of the sleeve; a lower end of the sleeve is fixedly connected with a cover plate, a through hole is disposed on the cover plate for the upper end of the presser foot to go through; and the pressing plate and the through hole are oppositely disposed.

10. The pressure adjustment mechanism of the sewing machine presser foot as claimed in claim 9 wherein a gap is disposed between an inner circumferential wall of the sleeve and the nut, the pad, and the pressing plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of one embodiment of a sewing machine;

(2) FIG. 2 is a schematic view of a partially sectioned sleeve in one embodiment of a pressure adjustment mechanism;

(3) FIG. 3 is sectional view of one embodiment of a pressure adjustment mechanism; and

(4) FIG. 4 is a sectional view of FIG. 3 along line A-A.

DETAILED DESCRIPTION OF THE INVENTION

(5) The structure and the technical means adopted by one embodiment of the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. However, the present invention is not limited by the preferred embodiments.

(6) One embodiment of a pressure adjustment mechanism of a sewing machine presser foot as shown in FIG. 1, the sewing machine comprises a frame 1, and the pressure adjustment mechanism comprises a motor 2, a sleeve 7 and a cover plate 8. The motor 2 is fixed on an upper end of the sleeve 7, a lower end of the sleeve 7 is fixed on the cover plate 8, and the cover plate 8 is fixed on the frame 1. At this point, the sleeve 7 is inclined; in other words, the axial direction of the sleeve 7 and the vertical direction form an included angle between 15° and 25°. As shown in FIGS. 2 and 3, the pressure adjustment mechanism further comprises a screw 21, a spiral spring 3 and a pressing plate 4. The spiral spring 3 and the pressing plate 4 are disposed inside the sleeve 7. A gap is disposed between an inner circumferential wall of the sleeve 7, and a pad 31 and the pressing plate 4. The screw 21 is formed by processing an outer thread on an outer circumferential wall of a shaft of the motor 2. A nut 5 is screwed and connected on the screw 21, and the nut 5 is lifted or lowered by the screw 21. The nut 5 is disposed inside the sleeve 7. A gap is also disposed between the nut 5 and the inner circumferential wall of the sleeve 7. The pressing plate 4 is underneath the nut 5. The circumferential direction of the nut 5 is unfixed. The spiral spring 3 is located between the nut 5 and the pressing plate 4. An upper end of the spiral spring 3 is fixedly connected with the metal pad 31. A center hole 311 is disposed on the pad 31. The screw 21 goes through the center hole 311 of the pad 31. An upper side of the pad 31 is pressed against a lower side of the nut 5. A lower end of the spiral spring 3 is pressed against an upper side of the pressing plate 4, and, in the circumferential direction, the lower end of the spiral spring 3 and the pressing plate 4 are unfixed. A presser foot 6 has a rod-shaped upper end. A through hole 81 is disposed on the cover plate 8, and the pressing plate 4 and the through hole 81 are oppositely disposed. The upper end of the presser foot 6 goes through the through hole 81 and presses against the pressing plate 4. In the circumferential direction, the pressing plate 4 and the upper end of the presser foot 6 are unfixed. The spiral spring 3 is being compressed under the effects of the nut 5 and the pressing plate 4.

(7) Specifically, a lower side of one embodiment of the pressing plate 4 has an inserting column 41. The upper end of the presser foot 6 has an inserting hole 61. The inserting column 41 is insertedly connected inside the inserting hole 61. The presser foot 6 keeps the pressing plate 4 stable through the inserting column 41. The upper side of the pressing plate 4 has a limiting column 42, and the lower end of the spiral spring 3 is sleeved around the limiting column 42. The pressing plate 4 keeps the lower end of the unfixed spiral spring 3 stable through the limiting column 42. The nut 5 is made of plastic. The lower side of the nut 5 has a columnar limiting portion 51. A screw hole of the nut 5 penetrates to a lower end face of the limiting portion 51. The limiting portion 51 is inserted inside the center hole 311 of the pad 31. As shown in FIG. 4, three limiting protruded portions 312 are disposed on a hole wall of the center hole 311, and the limiting protruded portions 312 are protruded arcuately. Three axially disposed limiting grooves 511 are disposed on an outer wall of the limiting portion 51. Adaptively, the cross section of the limiting grooves 511 is also in an arc shape. The three limiting protruded portions 312 are engagedly connected in the three limiting grooves 511 respectively. Therefore, the limiting portion 51 and the pad 31 are fixed in the circumferential direction through the mating of the limiting protruded portions 312 and the limiting grooves 511. Wherein, the sum of the lengths of the limiting portion 51 and the limiting column 42 is larger than that of the spiral spring 3 when it is compressed to the utmost. Thereby, the spiral spring 3 is prevented from being fully compressed to the utmost which will result in damage.

(8) When one embodiment of the pressure adjustment mechanism is in use, the spiral spring 3 is compressed between the nut 5 and the pressing plate 4. The pressing plate 4 generates a downward pressure against the presser foot 6. Thereby, between the upper end of the spiral spring 3 and the nut 5, between the lower end of the spiral spring 3 and the pressing plate 4, and between the pressing plate 4 and the presser foot 6, there is pressure. When the motor 2 actuates the screw 21 to turn, the nut 5 under the effect of the spiral spring 3 is subject to static friction in the circumferential direction. The static friction in the circumferential direction can limit the circumferential direction of the nut 5 and prevent the nut 5 from turning together with the screw 21. Thereby, the nut 5 is lifted up or lowered down in order to adjust the pressure of the presser foot 6. When the nut 5 is lowered overly, and if the limiting portion 51 and the limiting column 42 are pressed against each other causing the nut 5 not being able to lower down any further, because, in the circumferential direction, the nut 5 is unfixed, the nut 5 actuates the spiral spring 3 to turn together relative to the pressing plate 4; or the nut 5 actuates both the spiral spring 3 and the pressing plate 4 to turn together relative to the presser foot 6. Thereby, the nut 5 is prevented from being unable to lower, getting the screw 21 stuck, and causing the motor 2 to be overloaded and damaged.

(9) Note that the specifications relating to the above embodiments should be construed as exemplary rather than as limitative of the present invention, with many variations and modifications being readily attainable by a person of average skill in the art without departing from the spirit or scope thereof as defined by the appended claims and their legal equivalents.

(10) Moreover, the following technical terms mentioned in the present invention, for instances, the frame 1, the motor 2, the screw 21, etc., are used to explain and help to comprehend the present invention, but not as limitations thereof. Other technical terms may be used. Construing the technical terms as additional limitations is contrary to the scope and the spirit of the invention.

LIST OF REFERENCE PARTS

(11) 1 frame 2 motor 21 screw 3 spiral spring 31 pad 311 center hole 312 limiting protruded portions 4 pressing plate 41 inserting column 42 limiting column 5 nut 51 limiting portion 511 limiting groove 6 presser foot 61 inserting hole 7 sleeve 8 cover plate 81 through hole