Patent Application
20080022909
The invention described herein is for use with a portable sewing machine. However one skilled in the art will recognize that the invention described herein will also work for many systems which use a flywheel or other rotating member to drive a drive shaft. While the sewing machine described herein includes an attached motor, the invention described herein will work equally well if the flywheel is driven by an external motor, or a motor that is not attached to the sewing machine. Such external or unattached motors are common in industrial sewing machines.
With reference to FIGS. 1 and 3-8, the sewing machine 100 includes a housing 13 from which a main drive shaft 15 extends therefrom. A motor 17 having a power shaft 18 is used to drive a belt 19 to rotate a reduction pulley 26 which in turn drives belt 45 to rotate flywheel 35. A bushing 20 is placed about the exposed main drive shaft 15 and prevented from rotating about the main drive shaft 15 by at least one set screw 22. In the preferred embodiment, two set screws 22 are used to secure the bushing 20 the main drive shaft 15. One skilled in the art will recognize that the bushing 20 is not a necessary part of the invention. For instance, the main drive shaft 15 could incorporate a flange proximal to the housing 13, where the flange would permit engagement of a removable locking pin.
The bushing 20 includes a flange portion 21 and a narrower portion 25 of reduced diameter in comparison to the diameter of the flange portion 21. In the preferred embodiment, the set screws 22 are secured through the flange portion 21. The flange portion 21 includes apertures 32 extending from its outer perimeter to its central aperture 30 to accept the set screws 22. The bushing 20 is placed over the main drive shaft 15 so that the flange portion 21 is proximal to the main housing 13 of the sewing machine 100. This positioning allows the flywheel 35 to be placed over the narrower portion 25 of the bushing 20. Flywheel 35 is generally of a larger diameter than the flange portion 21 of the bushing 20.
The flywheel 35 includes a drive surface 40 on which the drive belt 45 engages. In the preferred embodiment, the drive surface 40 includes teeth to engage a toothed drive belt 45. One skilled in the art will recognize that a toothed drive belt 45 is not necessary, and a smooth drive belt, or other friction type drive can be used. The flywheel 35 includes a central aperture 41 sized to fit over the reduced portion 25 of the bushing 20. The flywheel 35 includes a locking pin aperture 51 extending therethrough generally parallel to the central aperture 41 of the flywheel 35, the flywheel locking pin aperture 51 is located radially away from the flywheel's central aperture 41.
The bushing 20 includes at least one corresponding locking pin aperture 55, positioned on the flange portion of the bushing 20, so that said locking pin aperture 51 is align when the flywheel 35 is placed upon the narrower portion 25 of the bushing 20. In the preferred embodiment, the bushing 20 includes four such locking pin apertures 55a-d, the locking pin apertures being equally spaced about the flange 21 of the bushing 20. As one skilled in the art will recognize, the bushing 20, and the flywheel 35 may have a plurality of such locking pin apertures 51.
The assembly also includes a retaining knob 57 which threads into the central aperture 30 of the bushing 20. The retaining knob 57 holds the flywheel 35 onto the bushing 20, while allowing the flywheel 35 to freely rotate about the bushing 20. The retaining knob 57 preferably has a diameter smaller than that of the flange portion 21 of the bushing 20. In alternate embodiments, the retaining knob 57 can thread directly into the main drive shaft 15.
The retaining knob 57 includes an pin holding aperture 58, which is used to hold the locking pin 60 when the locking pin 60 is not being used to hold the flywheel 35 and bushing 20 in an engaged relationship. The pin holding aperture 58 includes a portion of greater diameter 59 located away from the head of the retaining knob. The portion of greater diameter 59 allows the detent ball 70 to secure the locking pin 60 into place while not allowing the locking pin 60 to extend too far outside of the retaining knob on the side proximate to the machine housing 13. If the locking pin 60 were to extend too far, it could interfere with the drive shaft when a separate bushing 20 is attached to the main drive shaft 15.
When the flywheel is rotated so that any locking pin aperture 51 in the flywheel 35 is aligned with a locking pin aperture 55 in the bushing 20 a locking pin 60 can be inserted to secure the two together, thus allowing the flywheel 35 and bushing 20 to rotate together. This creates a direct drive situation whereby the flywheel 35 can not slip on the bushing 20. Then to disengage the flywheel 35 from the bushing 20, the locking pin 60 is removed from the apertures.
The locking pin 60 is stored in a pin holding aperture 58 in the center of the clutch or retaining knob 57. In this position the locking pin 60 does not engage or make contact with the bushing 20 so the flywheel 35 is free to rotate with respect to the main drive shaft 15, keeping the machine from operating (i.e. performing the sewing function).
The locking pin 60 includes a head 65 and a shaft 66. The locking pin 60 is preferably a detent pin with a spring 68 over the body of the shaft 66. The spring 68 is contained by the head 65 which is most preferably a thumb nut, and detent ball 70 at the opposite end of the locking pin 60. The spring 68 functions to hold the detent ball 70 against the surface of the bushing 20 to keep the locking pin 60 from moving in and out of the locking pin apertures once it is pushed into position. This eliminates potential rattling noises and also keeps the locking pin end from colliding with the sewing machine head casting or housing 13 in the proximity of the bushing 20.
The locking pin 60 also functions as a shear pin. The locking pin has a shaft tip end 90 opposite the head 65. In the preferred embodiment, the locking pin 60 has the following specifications:
One skilled in the art will recognize that these dimensions are merely preferred dimensions, and may vary with the specific application. For instance, the shear groove 71 may not be positioned 0.26 inches from the inside edge of the detent ball 70 of the shaft 68. The shear groove 71 should be positioned so that the groove is near the interface between the bushing flange portion 21 and the flywheel 35. In such a position, the shear groove 71 will function and break if sufficient force is applied between the flange 21 and the flywheel 35, such as when the motor is driving the flywheel 35, and the drive shaft 15 stops or is slowed by heavy fabric in the sewing mechanism, or other such obstruction.
Maximum power is achieved by using a flywheel 35 of greater diameter with an appropriate hole in the face of the wheel for the insertion of the pin 60 described above. However, flywheel 35 diameter changes are not necessary to reap the benefits of the direct drive system described.
One skilled in the art will recognize that placement of the locking pin apertures 51 and 55 can vary. However, placement of the locking pin apertures can be limited by design constraints of the sewing machine. For instance, the flange portion 21 of the bushing 20 can be as large as the flywheel 35. However if the flange portion 21 becomes too large in diameter, the flange portion may interfere with the bobbin winding wheel. Thus, in most applications, the flange portion 21 is of a diameter less than the flywheel 35. In other applications, it may be desirable for the retaining knob 57 to be larger than shown in the drawings. In such an application, the retaining knob 57 may include a locking pin aperture so that the locking pin can be inserted into the locking pin aperture in the retaining knob 57 and also through the locking pin apertures in the flywheel 35 and flange portion 21 of the bushing 20. In such an arrangement, the locking pin 60 will lock the retaining knob, flywheel 35, and flange portion 21 together so that they would rotate in unison.
The above invention can also be used on industrial and commercial sewing machines which are either portable or non-portable. For instance, a sewing machine in a powerstand (table with motor mounted under the table) can make use of the locking pin clutch described herein. Most of these machine types do not have a bushing attached to the upper drive shaft. In fact, they rarely have any clutch system at all. The flywheel is mechanically attached to the bare metal shaft end (main drive shaft). The intention is to have positive drive to the main drive shaft at all times with no slippage possible. Adding the clutch system allows for the same direct drive connection but enhances the operation by allowing for easy disengagement of the flywheel by dislodging the pin connecting the flywheel to the bushing. As previously described, the bushing may be unnecessary, if the drive shaft includes a flange portion, or other structure which allows insertion of a pin connecting the structure to the flywheel 35. The addition of a locking pin as described here on such an industrial sewing machine also adds the added functionality of a replaceable shear pin. In addition, the shear pin makes bobbin winding more convenient and it protects the machines internal parts from breakage.
The sewing machine clutch with a removable locking pin as described herein can also be constructed to include a captive locking pin. Such an alternate embodiments is shown in
The locking pin 161 for an embodiment including a captive locking pin is preferably a pop pin 180 (also known as a clamp pin or hand retractable plunger), as shown in
The spring loaded pin 182 includes a hand actuated knob 192 which when manipulated by a user will retract the spring loaded pin 182 into the boss 185. This action of retracting the spring loaded pin 182 also retracts the spring loaded pin from the bushing locking pin aperture 155, so that the bushing 120 and the flywheel 135 are free to rotate relative to one another.
Another embodiment of the invention may use a keyed locking pin 260, having a tab or key 280 extending from the shaft 281 of the locking pin 260, as shown in
The aperture 255 of the bushing 220 must be of an appropriate shape to allow for the passage of the keyed locking pin's key end so that the connection between the flywheel 235 and the bushing 220 can be severed by twisting the pin end in a manner that the keyed locking pin's key end is aligned with the aperture shape. Once aligned, the pin can be retracted so that the connection is disengaged. The assembly of the above mentioned components would require that the pin be installed at the back side 236 of the flywheel 235 before the hand actuated knob 282 is installed on the outside of the flywheel 235. This embodiment would work with or without a spring positioned between the knob and the flywheel outer surface. Such as spring would, however, helps to minimize vibration noises and also keep the pin from colliding with the sewing machine head casting or housing 13 in the proximity of the bushing 220.
Another embodiment uses the detent pin as described in the preferred embodiment. However, Instead of storing the pin in a pin holding aperture 58 in the center of the clutch knob 57, the pin can be pulled out just enough to become disengaged from the bushing 20. As with the pop pin and keyed locking pin embodiments, a void at the inside surface of the flywheel must exist to allow the pin's tip end 90 to rotate freely of the bushing 20. The flywheel aperture in the 151 must be of sufficient diameter to allow the pin and detent ball to retract inside the flywheel to a point where the pin's tip end 90 is clear of the bushing 20. Once this position is reached the flywheel aperture 151 must then decrease in diameter to roughly match the pin's diameter keeping the detent from sliding the remaining way through the flywheel 235. Thus, the void need only be as wide at to accommodate the detent ball, and of a sufficient depth to accommodate the detent ball and portion of the tip end 90 extending thereto. This way the locking pin becomes captive but can also be removed by force as in the preferred embodiment, thus becoming a removable locking pin as well.
Another variation is a threaded aperture in the flywheel for a screw pin which makes contact with the surface of the bushing 20 or engages an aperture 55 in the bushing 20 as the screw pin is advance or retracted by turning the screw pin in the appropriate direction.
The examples described here in are merely examples of the invention, and are not meant to be unnecessary limitations upon the same.
This application claims priority to U.S. Provisional application 60/820,427, entitled Sewing Machine Clutch with Removable Locking Pin, filed on Jul. 26, 2006. The aforementioned application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60820427 | Jul 2006 | US |
