GB2301600A

GB2301600A - Sewing machine bobbin capacity indicator

Info

Publication number: GB2301600A
Application number: GB9511763A
Authority: GB
Inventors: Gareth Richard Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-30
Filing date: 1995-05-30
Publication date: 1996-12-11
Also published as: GB9511763D0

Abstract

A device which calculates the amount of thread remaining on the bobbin of a sewing machine comprises a sensor (1), e.g. an optical sensor scanning a reflective area on the balance wheel of the machine, a processing unit (5) which calculates the thread consumption on the basis of the sensor signals and thus the thread remaining on the bobbin (the unit having initially been calibrated by running a full bobbin to empty) and a warning device or devices (7, 8) which indicate that the amount of bobbin thread is low. The sensor is connected to a conditioning circuit which may have a potentiometer to set the sensitivity of the unit. The warning devices may include an optical device (8) which flashes as the thread runs low and an audible device (7) which subsequently sounds. The device (8) also displays the percentage of thread remaining. The device may be used on a machine with twin needles/bobbins and indicates the bobbin with the lower thread amount.

Description

BOBBIN CAPACITY INDICATOR This invention relates to a sewing machine bobbin capacity indicator.

Lockstitch sewing machines use a top thread (a reel of thread placed on a stand in view of the operator) and a bobbin filled with cotton that is inserted into the sewing hook or shuttle underneath the bed of the machine.

If the operator was sewing articles that required there be no join or break in either of the two sewing threads, it would be easy for the operator to monitor the top thread and assess if sufficient cotton is avalable to complete the next article to be sewn orto change the top cotton reel.

The problem arises with the bobbin thread as this is out of view of the operator, and could therefore run out without warning If this occured part of the way through the article being sewn it would mean either rejecting the article as waste, or unpicking the article. This process is not only time consuming but also risks damage to the article as the stitches are unpicked.

In applications where twin-needle opperations are employed this would mean that if one of the bobbins was to runout part of the way through an article the operator would have two rows of stitching to unpick, increasing the risk of damage or rejected articles.

If the operator was aware of the actual amount of sewing thread currently on the bobbin they would then be able to evaluate whether to finish sewing the current article and then change the bobbin for a full one, or carry on sewing with the knowledge of exactly how much thread was left on the bobbin and exactly how many more articles could be sewn sucessfully.

Acording to the present invention there is provided a bobbin capacity indicator that comprises of: A control unit that houses a power supply and the processing unit with a switch to select between single and twin-needle operations.

A display unit that consists of an optical display device, an audible warning device, two push switches, and a signal conditioning circuit used to convert the output of a transducer (used to detect the rotation of the sewing machine ) into pulses sutable for the processing unit to interpret.

The transducer used to detectthe rotation of the sewing machine may be of any type that will allow the movement of the sewing machines balance wheel, gears or any other moving part to be monitored. This could be in the form of a hall effect sensor, a proximity sensor, a light activated switch, an inductive sensor ect but for the purpose of this description an optical reflective sensor is used.

A specific embodiment of the invention will now be describled by way of example with reference to the accompanying drawing in which: Figure 1 shows atypical lockstitch sewing machine with the three main parts of the bobbin capacity installed.

Figure 2 shows the optical sensor and balance wheel of the sewing machine Figure 3 shows a block diagram of the various parts of the bobbin capacity indicator.

Referring to Figure 1, the bobbin capacity indicator comprises of three main units : An optical sensor (1) that is positioned so that it is viewing the balance wheel (2) of the sewing machine (3). On the balance wheel (2) there is a light reflective marking (4) that passes the optical sensor every time the balance wheel rotates.

Conviently mounted by a small bracket (5) is the display unit (, . this would be positioned within easy reach of the operator so the push buttons can be pressed without overreach and for the operator to easily view the optical display device. Underneath the sewing machine table the control unit (7) would be secured.

Figure 2 shows in greater detail the sewing machine's balance wheel (1). and the optical sensor (2). The light reflective marking (3) may be in the form of awhite painted area, or a piece of light reflective tape may be affixed to the balance wheel.

Figure 3 shows a block diagram of the various units that make up the bobbin capacity indicator. The optical sensor (1) produces an electrical signal that is fed into the signal conditioning circuit (2) that produces a pulse sutable for the processing unitto interpret. Provision is made in the siqnal conditioning circuit two allow the sensitivity of the unit to be adjusted (this is in the form of a potentiometer (3) to prevent slight scratohes or other marks on the balance wheel causing afalse output signal. A light emitting diode (4) is used to accuratly align the optical sensor, this will pulse briefly every time the light reflective marking passes the light sensor.The output of amplifler (3) is fed into the processing unit (5).

Two push witches (6) are also installed into the display unit these are used to allow calibration of the unit and also to inform the unit when a bobbins) has been changed. These switches are conected to the processing unit (5). An audible warning device (7) is used to inform the operator when the bobbin capacityfallsto a preset level this is contolled bythe processing unit (5). An optical display device (8) is also provided, this will display the bobbin contents as a percentage itwill also be used to inform the operator when the bobbin capacity indicator is being calibrated. A power supply (9) is used to provide a low voltage supply for all the circuitry.A switch (1 0) is fitted to the control unit to allow the processing units program to select either single-needle or a twin-needle application. The processor unit uses a non volitile memory device to store the current bobbin contents and also to store previously programmed memories.

The basic operation is as follows: First the unit is calibrated by putting afull bobbin into the sewing machine and running the machine unitl the bobbin becomes empty, as this is done the unit counts the number of stitches sewn.

Once the unit is calibrated itwill be able to countthe number of stitches sewn and with the number of stitches on afull bobbin calculate the percentage of thread remaining.

The unit has also been given the ability to have the thresholds of when it beeps, flashes,ect programed by the operator so it does these functions at predetermined thread capacity levels.

Also the operator will be able to program memories and recall memories for different garment thicknesses to prevent the unit having to be recalibrated everytime the sewing operation is changed.

In twin needle operation, the unit will displaythe bobbin with the lowest capacity and show its percentage.

Claims

I A device that will calculate the amount of sewing thread remaining on the bobbin of a iockstitch sewing machine.
2 A device as claimed in claim where the amount of thread remaining on the bobbin is indicated to the operator by means of an optical display device.
3 A device as claimed in claim I that will warn the operator when the amount of thread remaining on the bobbin falls to a preset level by means of an audible warning device.
4 A device as claimed in claim that will allow preset thresholds to be set where the audible warning device sounds.
5 A device as claimed in claim li that will allow preset thresholds to be set where the optical display device prints up warnings relating to the amount of thread remaining on the bobbin
6 A device as claimed in claim r that will allow preset thresholds to be set whrer the optical display device will start to flash to attract the operators attention.
7 A device as claimed in claim I that will allow the operator to program various memories and be able to recall these memories so as to be able to use the device with various fabrics and different articles being sewn.
8 A device as claimed in claim 1 that will allow the two bobbins on a twin needle lock-stitch to be monitored an the bobbin with the lowest thread capacity displayed to the operator.
9 A device as claimed in claim I that will retain the memories stored in it in the event of power being removed from it.