Craven, Malcolm (AMF Reece Clayton Wood Close West Park Ring Road Leeds LS16 6QQ, UK)
Prout, Jason (AMF Reece Clayton Wood Close West Park Ring Road Leeds LS16 6QQ, UK)
Craven, Malcolm (AMF Reece Clayton Wood Close West Park Ring Road Leeds LS16 6QQ, UK)
| 1. | A drive mechanism for a jigfed sewing machine, said mechanism being operative to engage a driven edge of a jig which has been loaded with fabric and which has been moved to a starting position with respect to a sewing head of the machine, and in order to advance the jig relative to the sewing head so that required sewn seams can be formed; in which the drive mechanism is operative in one mode to advance the jig so as to allow a sewn seam to be formed in one direction, but which is convertible so as, when required, to reverse the motion of the jig so that a back tack can be formed. |
| 2. | A drive mechanism according to claim 1, in which the advancing movement of the jig in said one mode of the drive mechanism is an indexing movement. |
| 3. | A drive mechanism according to claim 1 or 2, and coupled with a drive wheel which can make frictional engagement with the driven edge of the jig, and in which the drive mechanism is operative to drive the wheel in one direction for the purposes of advancing the jig, and which can be disengaged in order to allow the mechanism to drive the wheel in a forward or reverse direction independently of the sewing head. |
| 4. | A drive mechanism according to claim 3, in which the drive mechanism is operative to drive the wheel in said one direction for the purposes of advancing the jig via a forward indexing feed. |
| 5. | A drive mechanism according to claim 4, in which the forward indexing feed can be disengaged using a clamping ring, so that an independent electric motor can then be engaged in order to drive the wheel in the reverse direction. |
| 6. | A drive mechanism according to claim 5, in which the independent electric motor is engageable to drive the wheel in the reverse direction using a clutch mechanism. |
| 7. | A jigfed sewing machine provided with a drive mechanism according to any one of the preceding claims. |
In the mass production of garments (or other stitched fabrics e. g. seat covers), it is known to use specially designed jigs to hold layers of fabric which are to be stitched together and to guide the movement of such jigs relative to the sewing head of an industrial type sewing machine, so that required seams can be formed.
The sewing machine therefore usually has a drive wheel which makes frictional engagement with an outer driven edge of the jig, in order to advance the jig through a predetermined cycle of operation.
In the formation of a sewn seam using a standard manual sewing machine, it is usually desirable to begin, and to finish off a seam with a so-called"back-tack", and which is usually obtained by an operator working a treddle to reverse the movement of the usual feed arrangement. Alternatively, a length of condensed stitches can be formed. However, using a automatically advanced jig with an industrial type of sewing machine, it is normal to start and to finish with a length of condensed stitches.
There are two existing methods of driving fabric, or fabric plus template (jig) through a sewing machine.
Firstly, there is so-called intermittent feed (indexed) whereby the transverse feed (of fabric or fabric plus template) is interrupted momentarily while the needle passes through the fabric in a transverse direction.
Secondly, there is continuous feed whereby no such interruption of the fabric motion or feed takes place.
However, from a quality point of view, intermittent feed is preferred.
Some automatic jig machines exist where a back tack seam end is possible. However, these machines employ lower quality drive means of continuous feed.
The invention therefore seeks to provide an improved drive mechanism which allows high quality sewn seams to be formed in one direction, but which can reverse the motion of the jig for the purposes of forming a"back tack".
According to the invention there is provided a drive mechanism for a jig-fed sewing machine, said mechanism being operative to engage a driven edge of a jig which has been loaded with fabric and which has been moved to a starting position with respect to a sewing head of the machine, and in order to advance the jig relative to the sewing head so that required sewn seams can be formed; in which the drive mechanism is operative in one mode to advance the jig so as to allow a sewn seam to be formed in one direction, but which is convertible so as, when required, to reverse the motion of the jig so that a back tack can be formed.
The invention therefore has the advantage of allowing the drive mechanism to be converted from its normal mode of advancing movement of the jig-usually indexing movement, to a continuous drive which can be used to reverse the motion of the jig so that a back tack can be formed.
Alternatively, the conversion can be used to allow the template (jig) to be moved in either direction in a way which is independent of the sewing head.
Accordingly, in a preferred arrangement, the drive mechanism is coupled with a drive wheel which can make frictional engagement with the driven edge of the jig, and in which the drive mechanism can drive the wheel in one direction for the purposes of advancing the jig, and preferably via a forward indexing feed, but which can be disengaged in order to allow the mechanism to drive the wheel in a forward or reverse direction independently of the sewing head.
The drive mechanism may therefore comprise a forward indexing feed to drive the wheel, but which can be disengaged using a clamping ring, so that an independent electric motor can then be engaged e. g. using a clutch mechanism, to drive the wheel in the reverse direction.
The above is a primary function of the drive mechanism, but there are advantageous secondary functions which are set out below.
Auxiliary Drive On special applications, sewing may be stopped at certain places along the sewing track, the jig is driven past a length of track, and with sewing commencing again after this length, all without any intervention on the part of the operator.
Continuous Feed Stitchina If an application is found where continuous feed for part of all of the main forward stitch is required, then this may be selected in a programmed control set-up.
Throuah-Track Auto Loadinq In conjunction with an auto start function (disclosed in more detail in our co-pending UK patent application No 0004784.5 filed 1 March 2000 a through-track auto start mechanism may be employed. The disclosure in our co-pending application is therefore incorporated herein by reference to the application, of which the application number details will be entered in due course. On smaller components e. g. cuffs, where the jig track may be kept open at the start, the operator may simply slide the jig to the throat plate, and let the machine take the jig to the sew start position.
A preferred embodiment of drive mechanism according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective illustration of the operating components of the drive mechanism, in partly exploded form for clarity; Figure 2 is a perspective illustration, to an enlarged scale, showing in more detail part of the drive mechanism; and Figure 3 is a detailed view of a releasable clamping device of the mechanism.
Referring now to the drawings, there will be described an improved drive mechanism for a jig-fed sewing machine, in which the mechanism is operative to engage a driven edge of a jig (not shown) which has been loaded with fabric and which has been moved to a starting position with respect to a sewing head of the machine. The automatic advancement of jigs of this type, in the industrial manufacture of garments (or other stitched fabrics), is well known, to those of ordinary skill in the art, and need not be described in detail herein.
The drive mechanism operates in order to advance the jig relative to the sewing head, so that required sewn seams can be formed.
The improved drive mechanism disclosed herein allows sewn seams to be formed in one direction via an automatically operating sewing machine, but which can also operate so as to reverse the motion of the jig for the purposes of forming"back tacks", when required.
The drive mechanism therefore is operative in one mode to advance the jig so as to allow a sewn seam to be formed in one direction, under programmed control, but which is convertible so as, when required, to reverse the motion of the jig so that a back tack can be formed.
The drive mechanism will apply drive to a friction drive wheel which engages the outer driven edge of the jig, and will now be described in detail with reference to the drawings.
In particular, the drive wheel is shown by reference 10 in Figure 2, and can be incrementally advanced by an index drive linkage 11, when the mechanism is operating in a first mode, so that a sewn seam can be formed in one direction, but which can be converted so as to operate in an alternative mode, in which the motion of the jig is reversed for the purposes of forming"back tacks".
The drive mechanism therefore includes an independent DC motor 12 operating via gearbox 13 and clutch 14, clutch plate 15 (see Figure 1) and motor drive gear 17 to reverse the rotation of the drive wheel 10. The DC motor 12 is therefore engaged using the clutch mechanism, while the forward indexing feed is disengaged using the clamping ring 16 around the jig drive free wheel arrangement.
The above description comprises the primary function of the improved drive mechanism disclosed herein. There are additional preferred secondary functions, as set out below.
Auxiliary Drive On special applications, sewing may be stopped at certain places along the sewing track, the jig driven past a length of track, and with commencing again after this length, all without operator intervention.
Continuous Feed Stitching If an application is found where continuous feed for part or all of the main forward stitch is required, then this may be selected in a programmed control system.
Throucrh-Track Auto Loading In conjunction with an automatic start function which may be provided, a through-track auto start system may be incorporated. On smaller components e. g. cuffs, where the jig track may be kept open at the start, the operator may simply slide the jig to the throat plate, and let the machine take the jig to the sew start position.
The invention therefore provides a drive mechanism which has the advantage of being able to be converted from a normal mode of advancing movement of the jig-usually an indexing movement, to a continuous drive which can be used to reverse the motion of the jig, so that a back tack can be formed. Alternatively, the conversion to the continuous drive mode can be used to allow the template (jig) to be moved in either direction in a way which is independent of the sewing head.
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