Centering device for sewing machines used to apply decorative strings on mattresses, quilts and similar articles

Abstract

 The present invention refers to a device installed as accessory on the head of sewing machines used to apply decorative ribbons or strings on fabrics for mattresses, quilts and similar articles; it being provided that the device is able to guarantee the perfect centering of the ribbon or string to be sewn with respect to the direction of the sewing head needle constantly and regardless of the direction of the sewing heads during operation.

Description

[0001] The present patent application for industrial invention refers to a centering device for sewing machines used to apply decorative strings on mattresses, quilts and similar articles.

[0002] The practice of sewing decorative ribbons and strings on the surface of mattress and quilt fabric has become especially popular.

[0003] In particular, the different sections of string sewn on the mattress surface can have the shape of a flower, a ribbon or any other ornamental element.

[0004] Strings are sewn continuously with sewing machines of known type.

[0005] Each machine comprises a sewing station and the fabric on which the strings are to be sewn moves under the sewing station.

[0006] The sewing station has a bridge structure that supports a series of parallel needle-holding heads that can translate both in longitudinal and transversal direction with respect to the fabric. For this reason, the needles are able to simultaneously sew different sections of string according to the same direction, including a closed curvilinear direction, in adjacent areas of the fabric.

[0007] It must be noted that each needle cooperates with a "fabric-pressing" foot, preferably with circular shape, able to interfere with the fabric during sewing.

[0008] The foot has a central hole used to introduce the string to be sewn on the fabric.

[0009] The hole is perfectly centered with respect to the vertical sliding axis of the need and designed to guarantee that the string remains under the needle during continuous sewing.

[0010] This guarantees that the thread that feeds the needle can properly sew the string.

[0011] Considering that the movements of the foot on the fabric are combined with the movements imposed on the sewing head, it appears evident that the foot can move on the fabric in any radial direction with respect to the central hole.

[0012] Moreover, considering that the string tends to penetrate the hole of the foot always with the same orientation (being forced to do it by suitable means provided on the sewing head that guide it next to the foot), it appears evident that every change of direction of the foot produces a change of the angle between the new direction of the foot and the direction according to which the string is introduced in the central hole of the foot.

[0013] In particular, the change of angle according to which the string is introduced in the foot is determined by the tension created between the last section of string sewn on the fabric and the first free section of the string.

[0014] Because of the continuous variation of the angle according to which the string is introduced in the foot, the string can have a misaligned position with respect to the sewing direction of the needle.

[0015] Because of the anomalous position of the string inside the foot, the needle is not able to execute a perfectly centered axial line during sewing.

[0016] Because of this, sometimes the needle is not capable to interfere with the string below.

[0017] The purpose of the present invention is to provide a device for sewing machines that, without altering the general structure of sewing machines, shall guarantee the perfect centering of the cord (or ribbon) to be sewn with respect to the needle regularly and continuously, in spite of the possible variation of the angle according to which the string is introduce in the hole of the foot.

[0018] A further purpose of the invention is to provide a solution to the aforementioned problem by means of a device that does not impair the sewing speed of the sewing machine, which can be maintained around the traditional speed of 3,000 stitches per minute.

[0019] The aforementioned purposes have been obtained by equipping a traditional sewing machine, with a traditional general structure, with a vertical rod that rotates around the needle, able to cooperate with the traditional foot with hole associated with the sewing needle.

[0020] More precisely, the rod has a hole on the lower end, in which the string (or ribbon) to be sewn on the mattress is introduced, before being introduced in the hole traditionally situated in central position in the foot that cooperates with the needle.

[0021] The rotations of the guiding rod are adjusted in real time by means of electronics installed on the machine, according to the different directions of the sewing head above the fabric to be sewn, and consequently of the foot that cooperates with the needle.

[0022] The calibrated, instantaneous rotations of the guiding rod guarantee that the end of the string to be sewn on the fabric is offered to the needle always from the front, that is to say in perfect alignment with the direction followed by the needle on the mattress.

[0023] Because of the rotating rod, the string is able to anticipate the sewing direction and be perfectly aligned with it.

[0024] This guarantees that the string is always placed in perfectly centered position with respect to the needle direction.

[0025] Obviously, the position of the string ensures that the sewing line of the needle is always perfectly centered, thus guaranteeing excellent technical, functional and aesthetical results.

[0026] For major clarity, the description of the invention continues with reference to the enclosed drawing, which is intended for purposes of illustration only and not in a limiting sense, whereby Figure 1 is the axonometric view of the head of a sewing machine equipped with the device of the invention.

[0027] With reference to Figure 1, the device of the invention is designed to be used on a traditional sewing machine, usually provided with a sewing head (T) that supports a needle (1) and a foot (2), with preferably circular shape, provided with a central hole (2a) through which the needle (1) and the (or ribbon) to be sewn is introduced; it being provided that the sewing head (T) is equipped with the spool that feeds the cord (C) to be sewn on the fabric below.

[0028] In particular, the device of the invention is provided with a metal plate (3), mounted in horizontal position at the base of the sewing head (T), it being also provided with suitable holes for the introduction of the shaft (1a) of the needle (1) and the shaft (2b) of the foot (2).

[0029] The back end of the plate (3) on the opposite side of the needle (1) supports an actuator (4) in vertical position (preferably a brushless motor), whose shaft is inserted into a suitable hole on the plate (3), slightly protruding from it.

[0030] The end of the shaft that projects under the plate (3) is coupled to a first gearvvheel (5) connected by means of a belt (6) with a second gearwheel (7) provided on the opposite end of the plate (3).

[0031] The function of the belt (6) is to combine the rotations of the two gearwheels (5, 7); in other words, the rotations of the first gearwheel (5) - that is to say the gearwheel controlled by the actuator (4) - are exactly transmitted to the second idle gearwheel (7).

[0032] It must be noted that the second gearwheel (7) has a suitable central hole for the introduction of the shaft (1a) that supports the needle (1).

[0033] The second gearwheel (7) is provided with a vertical rod (8) in lower position, it being equipped with an eye (8a) near the foot (2).

[0034] As shown in Fig. 1, the end of the string (C) to be sewn is first introduced in the eye (8a) of the rod (8) and then in the central hole (2a) of the foot (2) that cooperates with the needle (1).

[0035] As mentioned, the rotations of the rod (8), indirectly determined by the actuator (4) and suitable coordinated (by means of the electronics installed on the machine) with the sewing directions of the sewing head (T), maintain the end of the string to be sewn always in front of the needle (1) of the sewing head (T), regardless of the direction of the sewing head (T).

[0036] This guarantees that the sewing line of the needle (1) is always perfectly centered with respect to the string (C).

[0037] It must be noted that the foot (2) has a concave shape with upward concavity; because of this, the raised perimeter of the foot (2) can convey the section of string or ribbon suspended between the eye (8a) of the rod (8) and the central hole (2a) of the foot (2).

[0038] In view of the above, it appears evident that the introduction of the device of the invention in a traditional sewing machine does not alter the structure, the operation mode of the foot (2)-needle (1) assembly or the sewing speed.

[0039] This is because the device of the invention is assisted by a dedicated actuator and provided with an independent structure with respect to the sewing machine on which it is installed as accessory.

Claims

1. Centering device for sewing machines, of the type comprising a sewing head (T) that supports a needle (1) and a foot (2) with a central hole (2a) used to introduce the needle (1) and the string or ribbon to be sewn on fabrics for mattresses, quilts and similar articles, characterized in that it is provided with a gearwheel (7) with vertical axis centrally fitted to the shaft (1 a) that supports the needle (1) and designed to support a downward-facing rod (8) in lower position, provided with an eye (8a) used to introduce the ribbon or string, which are then introduced in the central hole (2a) of the foot (2) that, in this specific case, has a circular shape, it being provided that the gearwheel (7) and the rod (8) are driven into rotation around the shaft (1a) of the needle (1) by a suitable actuator (4) mounted on the sewing head (T), which, being controlled by suitable electronics installed on the machine, coordinates the rotations of the gearwheel (7) with the sewing direction of the sewing head (T), so that the eye (8a) of the rod (8) is joined with the gearwheel (7) and the end of the ribbon or string can always be positioned in front of the needle (1) of the sewing head (T), regardless of any possible direction of the sewing head (T).

2. Device as defined in claim 1, characterized in that the gearwheel (7) that supports the rod (8) is supported in idle on a horizontal plate (3) basically situated at the base of the sewing head (T) and provided with a through hole with vertical axis for the introduction of the shaft (2b) of the foot (2); it being provided that the plate (3) supports a second gearwheel (5) with vertical axis on the opposite side, directly coupled to the shaft of the actuator (4), whose rotations are transmitted to the idle gearwheel (7) by means of a suitable connection belt (6).

3. Device as defined in any of the above claims, characterized in that the foot (2) has a concave shape with upward concavity.

Drawing