Apparatus used to support and move a pair of parallel needles in exchangeable position installed in sewing machines

Abstract

 The present invention refers to an apparatus for sewing machines used to support and move a pair of parallel needles able to exchange their position while sewing.
The apparatus comprises an overlapped pair of shelves supported by the needle-holder bar, each shelf supporting one of the needles. The needles can exchange their position following to a relative roto-translation movement of the two shelves.

Description

[0001] The present patent application refers to an apparatus for sewing machines, designed to support and move a pair of parallel needles able to exchange their position while sewing.

[0002] Similar apparatuses already exist on the market and are used for two-thread sewing, in which the two threads cross to form decorative patterns characterised by stitches with transversal direction with respect to the sewing line.

[0003] According to one of the known devices, the two needles are supported by two vertical bars fixed on top to support brackets, both fitted to the same horizontal pivoting pin, which is an integral part of a cursor that receives the alternate movement necessary for the needles to originate the stitch.

[0004] The parallel needles can exchange their position by means of a cam that causes the oscillation of the needle-holder bars around the common pivoting pin in order to alternate the two needles rhythmically.

[0005] The distance between the two parallel needles can be changed by simply changing the cam with a simple and economic replacement operation.

[0006] Other apparatuses use a single bar to support and move the two needles, which are mounted at the base of the bar with a special articulated joint in diametrically opposite position with respect to the needles.

[0007] When the needle-holder bar rotates by 180°, the joint reciprocally exchanges the position of the needles, whose alternate travels occur in combination with the needle-holder bar.

[0008] This second type of apparatus is penalised by the fact that, in order to change the distance between the two needles, it is necessary to replace the articulated joint, with high cost in terms of time and money.

[0009] Although being different, the two types of apparatus of known type share a major drawback, meaning that when the needles are exchanged, the section of thread from the needle's eye to the thread-guide member is twisted. In addition to significant stress, this fact also causes the uneven movement of the thread, which originates unequal stitching in terms of exterior regularity of the stitches.

[0010] The purpose of the present invention is to find a solution to the aforementioned problem by devising a new apparatus used to exchange needles of sewing machines.

[0011] Another purpose of the present invention is to devise a new apparatus used to exchange needles of sewing machines with a completely new conception, in order to reduce production costs thanks to a very simple and economical structure, which requires no special adaptation or preparation of the sewing machine where the apparatus of the invention is installed.

[0012] Another purpose of the invention is to devise an apparatus used to exchange needles of sewing machines that allows to change the distance between the needles by simply replacing a single, inexpensive part.

[0013] The device of the invention comprises an overlapped articulated pair of shelves that frontally support sewing needles in lower position with perfectly vertical direction.

[0014] The first needle, that is to say the needle fitted to the upper shelf, is applied in central position in a V-shaped through slot, whose diverging sections exactly end at the two sides of the application point.

[0015] The slot acts as a cam to guide the movement of the second needle fitted to the lower shelf, which can assume two alternative working positions, in which the needle axis is aligned with the ending point of the two diverging sections of the V-shaped slot.

[0016] The back end of the upper shelf is anchored at the base of the needle holder bar, which gives the typical alternative vertical motion to the pair of parallel needles.

[0017] Likewise, the back end of the lower shelf is anchored at the base of the needle-holder bar with double freedom of movement, since the second shelf can translate forward or backward and rotate with respect to the bar.

[0018] In view of the above, the needle-holder bar drags both shelves in vertical alternate travels, while only the upper shelf is forced to follow the rotation imposed to the needle-holder bar when the needles exchange their position.

[0019] During this stage, the lower shelf and the second needle are first moved backwards and then pushed forward again, until the second needle is placed side by side with the first needle, but on the opposite side with respect to the side occupied before the rotation of the needle-holder bar.

[0020] For major clarity, the description of the apparatus according to the present invention continues with reference to the enclosed drawings, which are intended for purposes of illustration only and not in a limiting sense, whereby:

• Fig. 1 is an axonometric view of the apparatus of the invention, having removed some external parts to show internal components better;
• Figs. 2 and 3 are a top and side view of the upper shelf with the first needle, respectively;
• Figs. 4 and 5 are a top and side view of the lower shelf with the second needle, respectively;
• Fig. 6 is a side view of the apparatus of the invention;
• Fig. 7 is a top view of the apparatus of the invention with the second needle positioned to the left of the first needle;
• Fig. 8, being basically the same as Fig. 7, is a top view of the apparatus of the invention with the second needle positioned to the right of the first needle;
• Fig. 9 shows some examples of two-needle stitching that can be obtained with sewing machines provided with the apparatus of the invention.

[0021] With reference to the aforementioned figures, the apparatus of the invention comprises an overlapped articulated pair of shelves (1 and 2) supported by the needle-holder bar (3), which receives both a rectilinear vertical alternate and a rotation movement by means of traditional mechanisms, the first movement being designed for stitching and the second movement being designed to exchange the position of the needles (4 and 5).

[0022] The upper shelf (1) is basically rectangular in shape and has a back hole (6) where a central notch (7) ends, and a front through slot (8) with V-shape and vertex towards the hole (6).

[0023] The first needle (4) is applied under the upper shelf (1) in a point (P) located in the centre of the V-shaped slot (8), whose diverging sections exactly end at the two sides of the point (P).

[0024] The shelf (1) is frontally provided with a lower attachment (1a) with a thread-guide hole (1b) and a housing used to fit the first needle (4).

[0025] The upper shelf (1) is anchored at the base of the bar (3), which is inserted in the hole (6) and tightened by means of a fastening screw (9) used to approximate the sides of the central notch (7).

[0026] The lower shelf (2) has a basically wedge-shaped configuration characterised by a back slot (10) where a pin (11) is inserted, which protrudes from a circular pedestal (12) and is exactly inserted in the ending base section of the tubular bar (3).

[0027] It must be noted that by fastening the screw (9) the pin (11) is blocked inside the bar (3) and the shelf (1) is blocked outside the same bar (3).

[0028] The lower shelf (2) is supported by the pedestal (12), where the shelf (2) rests with large freedom of movement with respect to the pin (11) joined to the bar (3).

[0029] More precisely, the shelf (2) can translate forward or backward and rotate with respect to the pin (11).

[0030] Attention is drawn on the opposite pair of protruding elements (13) at the two sides of the shelf (2), which are held by traditional means (not shown) used to move the shelf (2) back. The forward return travel of the shelf (2) is ensured by a return spring (14) partially housed inside a guide cap (15) that touches and slides on the pin (11).

[0031] The point of the shelf (2) is provided with a vertical shaped attachment (16) under which the second needle (5) is fitted.

[0032] The attachment has a top thread-guide hole (16a) coaxial with the needle (5), and a second thread-guide hole (16b) at the base.

[0033] It must be noted that the first hole (16a) is situated in a peg (16c) that protrudes from the top of the attachment (16) and is exactly housed in the diverging sections of the V-shaped slot (8).

[0034] In view of the above, the position of the needles (4 and 5) can be exchanged by performing the simple sequence of operations illustrated below:

• actuate the means fastened to the protruding elements (13) in order to move the shelf (2) backward and make the peg (16c) move backward into the first section of the slot (8) until it reaches the vertex;
• rotate the bar (3) in such a way that the peg (16c) is aligned with the other section of the slot (8);
• deactivate the means fastened to the protruding elements (13) to allow the return spring (14) to push the shelf (2) forward until the peg (16c) reaches the limit on the bottom of the second section of the slot (8).

[0035] It must be noted that, according to the apparatus of the invention, the thread used for stitching is not twisted during the rotation of the needle-holder bar (3), being the thread away from the bar because the shelves (1 and 2) are provided with housings for the needles (4 and 5) at the front ends and housings (6 and 10) for the bar (3) at the back ends.

[0036] Finally, it must be noted that the distance between the needles (4 and 5) can be changed rapidly and simply by replacing the first shelf (1) with an identical shelf provided with V-shaped slot (8) having a different vertex.

Claims

1. Apparatus used to support and move a pair of parallel needles (4 and 5) installed on sewing machines of the type provided with a needle-holder bar (3) with vertical axis, which receives a vertical alternate movement and a rotation movement around its axis by means of traditional mechanisms, apparatus being characterised by the fact that it comprises:

- an upper shelf (1) fixed at the back end to the base of the bar (3) and supporting the first needle (4) at the front end in a point (P) in the centre of a through slot (8) with V-shape, whose diverging sections exactly end at the two sides of the point (P);

- a lower shaft (2) supporting the second needle (5) at the front end, which is free to rotate and translate forward and backward with respect to a supporting pin (11) with vertical axis anchored at the base of the needle-holder bar (3);

it being provided that the lower shelf (2) is movably coupled with the upper shelf (1) by means of a peg (16c) located in the shelf (2), which slides inside the through slot (8) and is coaxial with the needle (5).

2. Apparatus as defined in the preceding claim, characterised by the fact that the upper shelf (1) has a basically rectangular shape and is provided with a back hole (6) where a central notch (7) ends, and is also provided with a front through slot (8) with V-shape and vertex towards the hole (6), where the bar (3) is inserted and tightened by means of a fastening screw (9) used to approximate the sides of the central notch (7).

3. Apparatus as defined in claim 1, characterised by the fact that the lower shelf (2) has a basically wedge-shaped configuration and is provided with a back slot (10) where the pin (11) is inserted, which protrudes from a circular pedestal (12) and is inserted and fastened inside the ending base section of the tubular bar (3); it being provided with a pair of opposite protruding elements (13) at the two sides of the shelf (2), which is constantly moved forward towards the limit by a return spring (14) partially housed inside a guide cap (15) that touches and slides on the pin (11).

4. Apparatus as defined in the preceding claim, characterised by the fact that the point of the shelf (2) is provided with a vertical shaped attachment (16), where the second needle (5) is fitted in lower position, provided with a top thread-guide hole (16a) and a second thread-guide hole (16b) at the base.

5. Apparatus as defined in claim 4, characterised by the fact that the first hole (16a) is situated in the peg (16c) that protrudes from the top of the attachment (16) and is exactly housed in the diverging sections of the V-shaped slot (8).

6. Apparatus as defined in claim 2, characterised by the fact that the shelf (1) is frontally provided with a lower attachment (1a) with a thread-guide hole (1b) and a housing used to fit the first needle (4).

Drawing