FABRIC ADVANCEMENT DEVICE FOR SEWING MACHINES

Specification

This invention generally refers to a fabric advancement device for sewing machines. More specifically, it is a fabric advancement device for one or more sewing machine needles.

As is well known, in sewing machines there are jaws arranged below one or more sewing needles and designed to advance the two fabric flaps during their sewing.

Fabric advancement devices are known from patent documents US 3 611 817 A, US 5 309 854 A, CN 108 589 061 A.

The jaws have an elongated shape and include reliefs that cling to the fabric to advance it. For this purpose, the jaws make a helical movement always remaining in a substantially horizontal position.

A problem with the jaws and the fabric advancement device according to the known art is that one of the two fabric flaps that are sewn, specifically the upper one, is substantially braked by the presser foot.

As a result, the jaws move the lower fabric flap to the detriment of the upper fabric flap.

In other words, during sewing the upper and lower flap would have a different stroke, which can cause the upper fabric to ripple once sewn.

To overcome this problem, the operator has to move the upper fabric flap faster. As a result, the goodness of the stitching may vary depending on the skill and experience of the operator.

The purpose of this invention is to offer a fabric advancement device for sewing machines that guarantees a homogeneous movement of both the lower and upper fabric flap when sewing.

Another purpose of the invention is to provide a fabric advancement device that guarantees an optimal movement of the upper fabric flap, regardless of the pressure of the presser foot and the different speed of movement of the lower fabric flap.

A further purpose of the invention is to provide a fabric advancement device that allows to increase the quality of the sewing, obtaining a homogeneous sewing of the sewn fabric flaps, independently of the operator in action on the sewing machine. These and other purposes are achieved, according to the invention, by a fabric advancement device for sewing machines including a first bar at one end of which a first jaw is fixed, at the opposite end of the first bar being placed a first U- shaped body open downwards.

In the first bar there is a first elongated seat, in which a square pivot is housed, which acts as a fulcrum for the first bar and as a skid so that the first bar can move according to a horizontal oscillatory and translational movement.

A rotating pin is also included, to which a first cylindrical body is attached and to which a first cylinder eccentric with respect to the axis of the pin is associated, the first cylinder being housed in a homologous cylindrical seat obtained in a first square block to move vertically in the first U-shaped body.

The advancement device according to the invention is characterized by the fact that it includes a second bar at one end of which a second jaw is fixed.

At the opposite end of the second bar there is a second U-shaped body open towards the back of the second bar and a third U-shaped body open downwards. In the second bar there is a second elongated seat, in which the square pivot is housed, acting as a fulcrum for the second bar and as a skid so that the second bar can move according to a horizontal oscillatory and translational movement. It includes a second cylindrical body fixed to the rotating pin and to which a second cylinder is associated which is eccentric with respect to the axis of the pin, the second cylinder being housed in a homologous cylindrical seat obtained in a second square block designed to move vertically in the third U-shaped body, an eccentric cylindrical element being included and being fixed to the rotating pin, housed in a cylindrical seat obtained in a third square block designed to move horizontally in the second U-shaped body.

Through this configuration, since the third square block can only move horizontally inside the second U-shaped body, the eccentric cylindrical element in its movement moves the second arm vertically and therefore also the first arm. In a similar way, since the first square block can only move vertically inside the first U-shaped body, and the second square block can only move vertically inside the third U-shaped body, the first cylinder moves the first bar horizontally and the second cylinder moves the second bar horizontally.

The stroke of these last two displacements can be modified independently of each other, modifying the eccentricity of the cylinders with respect to their respective cylindrical bodies.

Advantageously, a parallelepiped block attached to the first bar can be received and slide into an elongated seat in the second bar, so that the second bar can move horizontally with respect to the first bar and any other relative movement between the first bar and the second bar is prevented. In addition, the parallelepiped block can be attached to the second bar by means of a plate, so that the first bar does not move away from the second bar.

The position of the first cylinder with respect to the first cylindrical body can be adjusted so as to vary the eccentricity of the first cylinder with respect to the rotating pin and thus change the stroke in the horizontal direction of the first bar.

This adjustment can be made by means of a first adjustment screw.

Similarly, the position of the second cylinder with respect to the second cylindrical body can be adjustable, so as to vary the eccentricity of the second cylinder with respect to the rotating pin and thus modify the stroke in the horizontal direction of the first bar.

This adjustment can be made by means of a second adjustment screw.

Further features and details can be better understood from the following description, given as a non-limiting example, as well as from the attached drawing tables: figure 1 is an axonometric view of a sewing machine including a fabric advancement device according to the invention; figures 2 and 3 are lateral axonometric views of the fabric advancement device according to the invention; figure 4 is an exploded axonometric view of the fabric advancement device according to the invention.

With reference to the attached figures, a fabric advancement device, arranged in arm B, shown in figure 1 , of a sewing machine, is indicated with 10.

The feed device 10 includes a first bar 12 and a second bar 14.

At one end of the first bar 12 and at one end of the second bar 14 a jaw group 16 and a single jaw 18 are attached, respectively. At the opposite end of the first bar 12 and at the opposite end of the second bar 14, a first U-shaped body 20 open downwards and a second U-shaped body 22 open towards the rear of the second arm 14 are arranged, respectively.

A third U-shaped body 24 open downwards is coupled to the second U- shaped body 22 by means of two coupling screws 23.

The first bar 12 and the second bar 14 have a first seat 26 and a second seat 28, respectively, in which a square pin 30 is inserted to be tied to the sewing machine frame so as to bind the same first bar 12 and second bar 14 in their movement.

A parallelepiped block 50 is tied to the first bar 12 by two first screws 52.

The parallelepiped block 50 can slide inside an elongated seat 54 formed in the second bar 14 adjacent to the second U-shaped body 22 and delimited by two second screws 56.

The parallelepiped block 50 is fixed to the second bar 14 by means of a platelet 58 that goes into the second bar 14 and is fixed to the same parallelepiped block 50 by means of two screws 60.

The square pin 30 acts as a fulcrum for the first bar 12 and the second bar 14 and is capable to guarantee a substantially horizontal translation of the first bar 12 and second bar 14.

The parallelepiped block 50 cooperates in this movement of the second bar 14 with respect to the first bar 12, as it only allows a relative movement of the two bars 12, 14 in a straight direction parallel to the direction of greater development of the same bars 12, 14.

The first U-shaped body 20, the second U-shaped body 22 and the third U- shaped body 24 receive a movement group 32 which in its articulated movement makes the first bar 12 and the second bar 14 move in an oscillatory and translational motion.

The movement group 32 includes a rotating pin 34 to which a first cylindrical body 36, a cylindrical element 38 and a second cylindrical body 40 are fixed. A first cylinder 42 is associated to the first cylindrical body 36 and can be arranged in an eccentric position with respect to the axis of rotation of the first cylindrical body 36.

In particular, the eccentricity of the first cylinder 42 can be adjusted by means of a first adjustment screw 41. The first cylinder 42 is received in a homologous cylindrical seat made out of a first square block 43 to move vertically in the first U-shaped body 20.

Similarly, the second cylindrical body 40 is associated with a second cylinder 44 which can be arranged in an eccentric position with respect to the rotation axis of the second cylindrical body 40. In particular, the eccentricity of the second cylinder 44 can be adjusted by means of a second adjustment screw 45.

The second cylinder 44 is received in a homologous cylindrical seat made out of a second square block 46 to move vertically in the third U-shaped body 24.

The cylindrical element 38 is also eccentric as the outer cylindrical surface is not coaxial to the rotating pin 34.

The cylindrical element 38 is received in a cylindrical seat in a third square block 48 designed to move horizontally in the second U-shaped body 22.

With one rotation of the rotating pin 34, the first cylindrical body 36 rotates together with the first eccentric cylinder 42 which moves the first square block 43 in which it is housed. The vertical component of the movement of the first cylinder 42 causes the vertical translation of the first square block 43 into the first U-shaped body 20, while the horizontal component of the movement of the first cylinder 42 causes the horizontal translation of the entire first bar 12.

Similarly, with a rotation of the rotating pin 34, the second cylindrical body 40 also rotates together with the second eccentric cylinder 44 which moves the second square block 46 in which it is housed. Also in this case, the vertical component of the movement of the second cylinder 44 causes the vertical translation of the second square block 46 in the third U-shaped body 24, while the horizontal component of the movement of the second cylinder 44 causes the horizontal translation of the entire second bar 14.

The cylindrical element 38, also eccentric, also moves the third square block 48 which moves in the second U-shaped body 22.

In the same way as described above, the horizontal component of the movement of the cylindrical element 38 causes the horizontal translation of the third square block 48 in the second U-shaped body 22, while the vertical component of the movement of the cylindrical element 38 causes the vertical translation of the entire second bar 14.

The vertical movement of the second bar 14 causes the simultaneous and identical vertical translation of the first bar 12, since the parallelepiped block 50, as previously described, blocks the two bars 12, 14 vertically.

On the other hand, as far as the horizontal translation is concerned, the first bar 12 and the second bar 14 remain independent, since the parallelepiped block 50 allows an independent horizontal translation.

The horizontal movement of each of the two bars can be adjusted, modifying the eccentricity of the first cylinder 42 and the second cylinder 44 in a differentiated way, acting respectively on the first adjustment screw 41 and the second adjustment screw 45.

Consequently, the jaw group 16 follows the movement of the end of the first bar 12 and the single jaw 18 follows the movement of the end of the second bar 14.

These movements are oscillating and translating, as the two bars are hinged in the square pivot 30 which, however, acts as a skid in the first seat 26 and in the second seat 28 and allows the horizontal translation of the same bars 12, 14.

The vertical movement of jaw group 16 and single jaw 18 is, on the other hand, coincident and is regulated by the fixed eccentricity of the cylindrical element 38.

The fabric advancement device 10 according to the invention therefore allows a different stroke, particularly in the horizontal direction, of the single jaw 18, which acts on the upper fabric flap, with respect to jaw group 16, which acts on the lower fabric flap. The fabric advancement device 10 therefore guarantees optimum movement of the upper fabric flap, regardless of the pressure of the presser foot and the different speed of movement of the lower fabric flap.

In addition, it increases the sewing quality, resulting in a homogeneous sewing of the sewn fabric flaps, regardless of the operator in action on the sewing machine. In addition, variations and modifications can be envisaged, to be considered included in the scope of the invention.

For example, a different system of connection between the two bars can be used, allowing independent horizontal translation of the two bars, but not vertical translation.