Claims
- 1. In a stitching machine including a needle adapted for reciprocatory movement into and out of a workpiece, shaft means connected to said needle for reciprocating said needle upon rotation of said shaft, drive means including a drive motor for rotating said shaft, operator control means for activating and deactivating said drive means, the improvement for positioning said needle in a preselected position along its reciprocatory path comprising
- a pneumatically powered positioning motor,
- means connecting said positioning motor in driving relation to said shaft means for rotation of said shaft means when said drive motor is inactive,
- a source of pneumatic pressure,
- conduit means connecting said source of pneumatic pressure to said positioning motor,
- valve means interposed in said conduit means and actuatably responsive to functioning of said operator control means,
- control means interposed in said conduit means between said valve means and said positioning motor and operative when said valve means is open to activate said positioning motor to rotate said drive shaft to position said needle in a preselected position along its reciprocatory path,
- said control means comprising cylinder means having a bore extending therethrough, piston means disposed in said bore and having one of its ends exposed to said pressurized fluid when said valve means is open, the opposite end of said piston means being exposed externally of said cylinder means and defining a contact surface, cam means having a recess therein and mounted on said drive shaft in juxtaposition to said contact surface, cam follower means interposed between said contact surface and said cam means including detent means thereon in position to engage said cam means, means biasing said cam follower means out of contact with said cam means, means defining a passageway in said piston means from its exposed end to an exit location within said bore, seal means defining a plurality of chambers between said piston means and said cylinder means, at least one of said chambers communicating with said exit location of said passageway in said piston means, and means defining an exit passageway from said bore to the exterior of said cylinder means at a location contiguous to said chambers, whereby the position of said piston means within said bore establishes fluid communication between at least one of said chambers and said exit passageway to control the flow of pressurized fluid to said positioning motor.
- 2. The improvement of claim 1 wherein said cam follower means comprises an arm means hingedly mounted at one of its ends with its opposite end freely movably with respect to said contact surface of said externally exposed end of said piston means.
- 3. The improvement of claim 1 wherein said externally exposed end of said piston means is radiused to reduce the frictional engagement between said cam follower means and said end of said piston means.
- 4. The improvement of claim 1 wherein said cam follower means includes a first surface thereof facing said cam means and an opposite surface thereof facing said externally exposed end of said piston means, and detent means provided on said first surface in position to engage said recess in said cam means, said exposed end of said piston means being freely movable with respect to said opposite surface of said cam follower.
- 5. The improvement of claim 1 wherein said recess in said cam means includes opposite side walls and a bottom joining said side walls and the angle of intersection of each of said side walls and said bottom is substantially equal to, but not less than, ninety degrees, and said detent means comprises opposite side walls and an outboard end wall joining said side walls and the angle of intersection of each of said side walls with said bottom wall is substantially equal to, but not less than, 90.degree., and the distance between said side walls of said detent means is slightly less than the distance between said side walls of said recess whereby said detent is snugly received within said recess.
- 6. The improvement of claim 1 including means biasing said piston means within said cylinder means toward a position of disengagement with said cam follower means and biasing said cam follower means in the same direction as said piston means.
- 7. The improvement of claim 6 wherein said cam follower means is loosely connected with said exposed end of said piston means for substantially simultaneous movement of said cam follower means with said piston means.
- 8. The improvement of claim 1 including first spring means biasing said piston means in a direction away from said cam follower means, and further spring means biasing said cam follower toward said exposed end of said piston means and away from said cam means, the biasing force of said further spring means being small relative to the biasing force of said first spring means.
- 9. The improvement of claim 1 and including connector means interposed in said conduit means between said positioning motor and said control means and adjacent said positioning motor and defining chamber means, a flow restrictive orifice leading into said chamber means and regulating the flow of air through said conduit means to that value which will operate said positioning motor at a predetermined rotational speed but less than that air flow required to start said motor, the volume of said chamber being large enough to accumulate that quantity of air required to start said positioning motor under load.
Parent Case Info
This application is a continuation-in-part of copending application Ser. No. 504,324, filed Sept. 9, 1974 now U.S. Pat. No. 3,924,553, dated Dec. 9, 1975, entitled: "Needle Positioning Apparatus for Stitching Machines."
This invention relates to stitching machines and more particularly to apparatus for positioning the reciprocatable needle of such machines in a predetermined position along the reciprocatory path.
It is well recognized in the industries which use stitching machines, particularly the garment industry, that there exists a need for apparatus associated with a stitching machine which will position the reciprocatory needle either in the work or out of the work upon the completion of a stitching operation. Such positioning of the needle at the end of a stitching operation has been performed heretofore by the operator turning a hand wheel to rotate the drive shaft for the needle to move the needle into or out of the work as desired. By way of example, if the work-piece is to be turned to change the direction of stitching, it is desired that the needle be stopped in the work. Contrariwise, if the work-piece is to be removed from the machine at the end of the stitching operation, it is desired that the needle be stopped in a position out of the work.
Numerous devices have been proposed for automatically positioning the needle of a stitching machine in a preselected position at the end of a stitching operation. These devices predominately have been of the electrical or electro-mechanical type. In most all instances, these devices have involved the use of a cam or its equivalent associated with the drive shaft for the needle and a cam-follower type machanism which halts the rotation of the needle drive shaft upon the needle achieving the desired position. Most generally, these prior art devices have each included an auxiliary motor which rotates the needle drive shaft after the main drive motor for the needle drive shaft has been stopped at the end of a stitching operation.
Despite the acknowledged advantages of a needle positioning apparatus, and despite the numerous attempts to accomplish the desired results, it is generally acknowledged in the industry that there are no needle positioning devices presently available that are satisfactory from either their operation and/or economic standpoints. Besetting these prior art needle position devices are the problems of complexity of design, difficulty of installation, and sensitivity to maladjustment, all of which contribute to relatively high initial cost and inordinate demands relating to maintenance of the devices after their installation. So far as is known to applicant, prior to applicant's invention as disclosed in his copending application U.S. Pat. No. 3,924,553, there has been no pneumatically operated needle positioning device.
Not only is it desired in the stitching industry that there be provided a pneumatically powered needle positioner, it is desired that such positioner function rapidly and accurately. It is common in the stitching industry to pay wages to operators on the basis of their work output as measured by the number of piece goods that the operator completes in a given period of time. Operators are commonly assigned minimum work quotas with a premium being paid for work completed in excess of such quota. These operators, therefore, desire stitching equipment that performs its function accurately and reliably. In the instance of needle positioners for stitching machines, it is desired that there be a minimum of time consumed during the positioning cycle, i.e., from the time the operator heels the stitching machine until the needle is positioned for the operator to commence a further work maneuver, which may be relocating a workpiece, removing a completed workpiece and inserting a new workpiece, etc. Applicant's copending application Ser. No. 504,324, discloses a needle positioner for stitching machine that is relatively fast and reliable in its operation. The present disclosure provides for faster starting of the needle positioning function, for less time for completing a positioning cycle, and for more accurate positioning of the needle at the desired location along its reciprocatory path.
As concerns the accuracy of the position of the needle relative to its desired position at the end of a positioning operation, it has been recognized in the art that a few degrees of rotational movement of the drive shaft of the needle produces substantial distance of movement of the needle along its reciprocatory path so that as little as three to five degrees of inaccuracy in stopping the rotation of the drive shaft in a needle positioning operation can result in intolerable inaccuracies in the ultimate stopped position of the needle.
It is therefore an object of this invention to provide an improved apparatus for automatically positioning the needle of a stitching machine in a preselected position along its reciprocatory path following the cessation of a stitching operation. It is another object to provide an improved apparatus of the class described in which there is improved accuracy in the position of the needle along its reciprocatory path relative to the desired position of the needle upon completion of the positioning cycle. It is another object to provide an improved needle positioning apparatus in which there is a relatively shorter period of time consumed in the course of the positioning operation.
US Referenced Citations (2)
| Number |
Name |
Date |
Kind |
| 1880164 |
Whitehouse |
Sep 1932 |
|
| 3592153 |
Margereson |
Jul 1971 |
|
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 497,893 |
Dec 1938 |
UK |
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
504324 |
Sep 1974 |
|
Patent Grant
3977339
