WO1996001778A1

WO1996001778A1 - Automatic dual bobbin

Info

Publication number: WO1996001778A1
Application number: PCT/US1994/010480
Authority: WO
Inventors: Steven Chang
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-07-07
Filing date: 1994-09-16
Publication date: 1996-01-25
Anticipated expiration: 1997-01-07
Also published as: AU7729794A

Abstract

An automatic dual bobbin mechanism is provided. A housing (1) containing two bobbins oriented side-by-side (10 and 11) with the sewing needle (4) passing through a needle pocket between the bobbin pair replaces the conventional single bobbin configuration. The bobbin pair acts in a tag-team operation whereby one bobbin supplies the additional thread to be stitched into a fabric while the second bobbin is simultaneously being filled with thread from an external source. When the first bobbin is emptied, the bobbin pair is rotated 180° inside the housing. The second bobbin, now full, is in position to supply thread for continued stitching while the first bobbin is in position for refilling with thread supplied by the external source. A unique thread hook housing cap (2) is also provided which can automatically rethread the needle and cut bobbin thread from an external source.

Description

AUTOMATIC DUAL BOBBIN

BnitiBia y of the Invention

An improvement in existing sewing machine bobbin transfer, replacement and respooling methods is provided whereby two bobbins are constantly kept together inside a housing which contains bobbin casings. The housing is designed so that it can hold the bobbin casings, catch thread from the newly filled bobbin, cut said thread when commencing respooling and wrap the thread around the bobbin casings and sewing needle to complete required stitches.

"Male" and "female" type connectors between the bobbins allow them to spin in unison inside the casings. While one bobbin is supplying thread for stitching into the fabric, the other is being respooled. At a predetermined instant corresponding to the number of bobbin revolutions required to empty the full bobbin, the full and empty bobbins (and casings) are rotated inside the housing. Depending on the particular type of sewing machine the bobbins may be rotated automatically by electromechanical or electromagnetic means or manually by use of a lever arm attached to the bobbin casings.

Each bobbin casing is provided with a groove. Once the bobbins have switched positions, the bobbin thread (under tension) travels along the grooves from the full bobbin to the empty bobbin. A hook on the empty bobbin then catches this thread to enable respooling to commence.

Background of the invention

The advent of the sewing machine changed the face of the garment industry from tiny, store-front shops with a few seamstresses and tailors, into a multi-billion dollar per year operation. The sewing machine provided a fast and effective way to stitch fabric while maintaining or even surpassing the high degree of quality found in hand stitched garments. Moreover, large numbers of a single type of garment could be produced in a greatly reduced amount of time. However, sewing machines were limited by the fact that certain garments required the looping and stitching of an additional thread to properly join two pieces of fabric. This additional thread was supplied by a secondary thread source or bobbin. Bobbins were extremely limited in their thread capacity and frequently required changing. Once a bobbin was emptied of its thread, a sewing machine operator would have to stop the stitching process, manually remove the empty bobbin, replace it with a full bobbin, rethread the needle hook and needle and resume stitching. This became a time consuming process and sometimes led to poor garment construction or damaged the delicate fabrics being joined. Since the success of a garment manufacturer depended mostly on the ability to constantly supply quality clothing in a timely manner, there arose a need for a bobbin mechanism that had an increased thread supply or was capable of continuous bobbin replacement feeding to reduce "down time" during sewing machine operation.

Various improvements in bobbin technology have been made. Rovin et al. (U.S. Patent No 4,002,130) teaches an automatic bobbin rewinding mechanism whereby an empty bobbin and its case are removed from a sewing position and inserted to a rewinding position, while simultaneously, a filled bobbin is removed from the rewinding position and inserted to a sewing position. However, the procedure of transferring the bobbins from rewinding to sewing positions requires various mechanical components including actuators, cams, gear drives, etc. which results in a bulky frame needing to be bolted to the existing sewing machine.

Mardix et al. (U.S. Patent No. 5,143,004) teaches a sewing apparatus which comprises a sewing needle, a bobbin for feeding thread to the sewing needle, a rotary housing containing the bobbin and its case, a sensor for sensing the non-feeding of thread to the sewing needle and an automatic extraction-loading device for extracting an empty bobbin and replacing it with a full one. This automatic bobbin-reloading system also utilizes a series of rotary actuators, pistons, etc. to remove and refill bobbins. Also, an optical sensor to detect bobbin thread-breakage or -exhaustion further adds to the complexity of the device.

Kos as (U.S. Pat. No. 4,681,050) teaches a bobbin in run-out detector and bobbin changing mechanism. The mechanism comprises a carriage which supports a rotatable turret that holds a pair of bobbins. The run-out detector, similar to that of Mardix, is also an optical sensor device. This machine however is limited in that upon detection of an empty bobbin, it must stop the sewing operation to rotate the turret to move the full bobbin into the sewing position, retract the empty bobbin and replace it with the full bobbin. Further, once the full bobbin is in position, an additional step to resynchronize the hook and bobbin is employed before sewing can continue.

Despite the advances in bobbin rewinding and transfer technology, there still is a need for improved thread run¬ out detection and transfer of bobbins for smooth, continuous operation without the addition of bulky frames attached to the existing machines or extra steps to rethread hooks or refill bobbins. The subject invention discloses such a device in that it is a single unit that replaces current bobbin assemblies. Two bobbins nestled in a side-by-side configuration "float" inside a housing and are never physically removed from the unit when transfer takes place. Rather, the bobbins rotate 180° within the housing from the "sewing" position to the "filling" position. The end cap of the housing replaces the existing bobbin thread hook and the entire unit is connected directly to the main driveshaft of the sewing machine. The thread is supplied by a single external source and constantly remains taut, allowing for automatic rethreading of the needle and refilling of the empty bobbin. Further, thread-exhaustion detection is linked directly to bobbin revolutions. A preset value of revolutions is programmed into the machine (either by manual digital counter or by computerized monitoring) so that when the set value is reached, bobbin transfer is automatic. Since the preset value is determined by thread thickness and number of thread rotations on the bobbin, the bobbin is always fully exhausted when the preset value is reached.

Brief Description of the Figures

Figure 1 is a side view of dual bobbin mechanism attached to the drive shaft of the sewing machine.

Figure 2 is a cross-sectional view of the dual bobbin mechanism attached to the driveshaft of the sewing machine.

Figure 3 is an exploded view of the dual bobbin mechanism.

Figure 4 is a perspective view of the left and right side bobbins removed from their casings.

Figure 5 is a top view of the left and right side bobbins removed from their casings.

Figure 6 is a perspective view of the left and right side bobbin casings with bobbins in place.

Figure 7 is top view of the left and right side bobbin casings with bobbins in place.

Figure 8 is an exploded perspective view of one bobbin casing, bobbin casing cap and retaining spring clip. Detailed Description of the Invention

As sewing machines are fairly common articles and are well known to those skilled in the art of garment manufacturing, the basic functioning and operation of these machines will not be discussed. Rather, specific improvements to the existing bobbin design and replacement operation are discussed.

In the preferred embodiment of the invention, a single housing containing two bobbins, thread hook and means for rotating and refilling bobbins replaces existing systems or components. The mechanism is attached directly to the main driveshaft of the sewing machine thereby replacing the existing sewing head. Thread for refilling the empty bobbin is supplied by the main thread supply, fed through the driveshaft and into the housing. The number of revolutions required to empty a bobbin in the sewing position corresponds to revolutions required to fill a bobbin in the refilling position. Since this number is predetermined and programmed into the machine, transfer of bobbins is instantaneous and without waste or unexpected exhaustion of thread.

The preferred embodiment of the mechanism fully assembled and ready for operation is shown in Figure 1. As some new sewing machines are capable of operating at 7000 RPM, the mechanism should be fashioned from durable materials to minimize the effects of heat and/or warpage due to friction. The housing (1) and thread hook housing cap (2) should be made of a metal or alloy, preferably steel, so as to maintain their dimensions and integrity during operation. The unit is mounted on the outer rotating driveshaft (5) of the sewing machine which sits on the stationary inner shaft (6) . Also shown in Figure 1 for the purpose of orienting the device with existing sewing machine components, is the needle (4) .

Figure 2 is a cross-sectional view of the dual bobbin mechanism. The unit is attached to the outer driveshaft (5) by a set screw (8) which allows the unit to be removably secured to the machine for the purpose of servicing or replacement with the existing bobbin assembly. To facilitate rotation, the mechanism is provided with a brass sleeve bearing (7) between the inner shaft (6) and the outer driveshaft (5) . Since all models of sewing machines do not have the same bobbin configuration, the method by which the mechanism rotates on the shaft may also be by other means including ball or roller bearings.

The two bobbins (10 and 11) are oriented in a side by side manner. The left side bobbin (10) is provided with a tab or protrusion on its outer edge (18) and the right side bobbin (11) is provided with a complementary indentation (19) on its outer side. They are held in position relative to one another inside the housing by bobbin casings (12 and 13) . Each of the two casings are provided with covers (3 and 14) to provide access to the bobbins when necessary. The covers are secured to the casings by means of a retaining spring clip (15) . Each combined bobbin casing and cover is fashioned in a hemispherical shape so that when placed adjacent to each other, they form a nearly spherical body in which the bobbins (10 and 11) reside. The inner surfaces of the housing (1) and thread hook housing cap (2) combine to form a spherical shape of nearly identical dimensions to those of the bobbin casings and covers.

Figure 3 is an exploded view of the unit. The right side bobbin (11) fits inside the right side bobbin casing (13) . The right side bobbin casing (13) is enclosed on one side by the right side bobbin casing cap (14) . The bobbin casing cap is provided with a spring lever clip mechanism (15) to lock it in place on the casing as well as an axial shaft on which the right side bobbin (11) sits to permit free rotation of the bobbin within the casing. The assembled right hand bobbin, casing, cap and clip then fits into the housing (1) . The left side bobbin (10) is assembled into the left hand side of bobbin casing (12) with left side bobbin casing cover (3) and clip (15) in place in a similar manner. An exploded view of the left side bobbin casing, cover and clip is shown in greater detail in Figure 8. The left hand bobbin casing (12) then fits inside the thread hook housing cap (2) . The thread hook housing cap (2) is provided with male threads which then screw into place onto the housing (1) which is provided with female thread grooves to receive the thread hook housing cap (2) . The entire unit is then inserted on the rotating outer drive shaft (5) of the sewing machine and secured by the set screw (8) . These features allow the bobbins (10 and 11) to rotate inside their respective casings at the same time and rate of speed while the casings (12 and 13) remain stationery and float inside and housing (1) and thread hook housing cap (2) which spin at normal sewing machine speeds (up to 7000 RPM) .

More detailed views of the bobbins and bobbin casings are displayed in Figures 4, 5, 6 and 7. Both bobbins are provided with hooks (16 and 17) on their inside edges for catching thread during the refilling process (see Figs. 4 and 5) . Figure 6 shows a side-by-side view of the bobbin casings removed from the housing with bobbins in place. Both bobbin casings (12 and 13) contain grooves (20 and 21) cut into the casings to allow the thread from the main thread supply to pass from the filled bobbin to the empty bobbin during the bobbin switching process. The grooves further act as a needle pocket which allow the sewing needle (4) access to the thread during sewing.

A completely assembled dual bobbin housing will contain the following: a full left side bobbin with thread coming up through groove (20) to catch needle (4) , a right side bobbin empty whereby thread (9) from the main thread supply is hooked by the right side bobbin hook (17) so that refilling can commence, a manual digital counter or computerized monitor which counts bobbin revolutions and has been preset to the number of revolutions required to empty the full left side bobbin (10) .

Once these conditions have been established, sewing can commence. Sewing proceeds in a normal fashion with bobbin thread being hooked by thread hook housing cap (2) and fed around needle (4) and dual bobbin assembly to complete the required stitch pattern. Once the preset number of bobbin revolutions is reached, the left and right side bobbin casings (12 and 13) will automatically switch positions, i.e. left side will rotate 180° to right side and right side will rotate 180° to left side. Since the empty bobbin (11) was rotating at the same speed as full bobbin (10) , it was being refilled by the main thread supply at the same rate at which thread was being removed from full bobbin (10) . The rotation of the bobbin casings may be effected by any means necessary and include but are not limited to electromagnetic, magnetic, or electromechanical means. Once the means of counting the bobbin revolutions reach the preset value, it will trigger the mechanism for rotating the bobbin casings. On manual sewing machines, once the digital counter reaches the preset value, a lever arm connected to the housing can be operated to rotate the bobbin casings. The thread (9) from the main thread supply is subsequently dragged around the bobbin casing during rotation. Once the casings are rotated the full 180°, the thread (9) from the main thread supply begins to travel across the groove (21) of the just-rotated casing (13) containing the full bobbin (11) through the groove (20) of casing (12) to the now empty bobbin (10) . Since the main thread supply is always under constant tension, thread (9) is compelled to travel along the grooves of the two bobbin casings until it reaches its original position at the extreme right side end of the now empty bobbin (10) . Sewing operation can then immediately recommence with the thread (9) being between the left side and right side bobbin casings, caught by the thread hook housing cap, cut by said hook, grabbed down by needle (4) and stitched. As the housing and thread hook begin turning to cut the thread, thread (9) from the main supply, still under tension, is hooked by the now empty bobbin hook (16) and begins refilling the empty bobbin (10) . Simultaneously, the counter is reset to begin counting the number of new revolutions for the now full bobbin (11) . The counter continues until the set number is reached which subsequently triggers the next rotation of the bobbins.

The operation of this device results in momentarily halting the sewing process while bobbins are switched, thread hook and needle are prepared for next stitch and the empty bobbin is prepared for refilling. The advantages of this mechanism over previous types of bobbin changing systems is that bobbins are never removed from their casings to effect respooling. Further, the simplicity of design eliminates the need for cumbersome bobbin switching means including carriages, cams, rotating arms, etc. This reduction in the number of moving parts reduces the possibility of breakdown due to frictional heat, build-up of residual thread fuzz around thread hook rotary, and loss of lubrication, thereby increasing reliability of the overall system and improving machine and operator efficiency.

While the preferred embodiment of the invention has been described in detail, alternate embodiments will become obvious to those skilled in the art after reading this disclosure. These variations are to be considered within the scope and spirit of the subject invention. Consequently, the subject invention is only to be limited by the claims which follow and their equivalence.

Claims

What is claimed is:

1. A dual bobbin mechanism for use on a sewing machine which comprises:

means for holding two bobbins in a side-by-side configuration whereby both bobbins rotate at the same time and speed;

means for rotating the two bobbins to allow for repositioning of a full bobbin to the empty bobbin position and an empty bobbin to the full bobbin position to maintain a continuous sewing operation;

means for the automatic rethreading of the empty bobbin to begin respooling with thread; and

means for the cutting and hooking of thread from the full bobbin to begin stitching once bobbin rotation has occurred.

2. A dual bobbin mechanism of claim 1 wherein the means for maintaining two bobbins in a side-by-side position comprise a right side housing and left side thread hook housing cap which house right half and left half bobbin casings that contain bobbins.

3. A dual bobbin mechanism of claim 2 wherein one bobbin comprises a protrusion on its side which meets and fits adjacent to an indentation on the side of the second bobbin to permit both bobbins to spin together.

4. A dual bobbin mechanism of claim 1 wherein the means for rotating the bobbins comprise a mechanical lever or electromechanical or electromagnetic device.

5. A dual bobbin mechanism of claim 1 wherein the means for automatically rethreading of empty bobbin comprise a groove or channel cut into each bobbin housing which allows the free travel of thread under tension from full bobbin to empty bobbin.

6. A dual bobbin mechanism of claim 5 wherein the thread under tension is respooled on the empty bobbin by catching a hook on the inside of the enclosed side of the bobbin.

7. A dual bobbin mechanism of claim 1 wherein the means for cutting and hooking of the new bobbin thread comprise a thread hook housing cap removably attached to the dual bobbin housing.