Abstract:
An improved sewing machine is disclosed for making consistent edge seams. The improvement automatically adjusts a width of a sewn seam based upon feedback from a sensor which detects a position of a sewn edge. Feedback from the sensor causes a transverse adjustment in the position of an edge guide. An outside foot of the sewing machine may be suspended on a biased linkage to permit its transverse displacement when making an adjustment to a seam width.

Description:
TECHNICAL FIELD 
     This invention relates generally to sewing machines, and, more specifically, to sewing machines having apparatus to ensure a seam is sewn having a correct width. 
     BACKGROUND 
     Sewing machines wherein the instant invention finds exemplary application include industrial sewing machines used to form edge seams. Such machines may incorporate a feedback sensor to ensure proper positioning of material being sewn. A light-based sensor arrangement used in certain commercial sewing machines has a light sensor that is positionable to track a location of an edge of material while the material is being sewn. The sensor can be adjusted to trigger when the sewn seam becomes too wide, occluding the sensor beam. When such a condition occurs, the sensor triggers to turn off the sewing machine. Unfortunately, however, the momentum of the sewing machine causes additional stitches to be sewn in the material before the needle can be brought to a halt. Consequently, from about one to perhaps several inches of noncompliant seam will be sewn as the machine slows down. Generally, the noncompliant portion of the seam must, at a minimum, be picked apart for re-stitching at a correct width. The entire seam may need to be undone, and the seam started from a beginning, for aesthetic or other reasons. In some cases, the noncompliant seam may ruin the article in which the seam is being sewn, causing the article to be scrapped. 
     Certain available sewing machines have an edge guide to space a sewing machine needle from a material&#39;s sewn edge. Such guides are adjustable mechanically, for example, by turning a threaded shaft, but such adjustment is limited to an initial set-up for seam size. A seam may be sewn by an operator with such a machine by pressing material into engagement with the guide surface simultaneously with pushing slightly in a direction to feed material into the machine needle. No adjustability in guide location is contemplated when a seam is being sewn. 
     SUMMARY OF THE INVENTION 
     The invention provides a device automatically to adjust a seam size while sewing the seam in a sewing machine. The invention can be embodied as a clamping foot for a sewing machine. The clamping foot includes an inside foot adapted for attachment to the sewing machine, and an outside foot suspended in transversely adjustable relation from the inside foot. A biasing element is typically arranged to bias the outside foot in an outside direction from the inside foot. The clamping foot may be used in combination with an edge guide operable to assist in feeding material into sewing engagement with a sewing machine on which the clamping foot is attached. Usually, a transducer is affixed between the sewing machine and the edge guide. The transducer transversely displaces the edge guide to control a seam size. A sensor is positioned to validate a seam size and provide a signal in a feedback loop to control the transducer. A stop mechanism may be used to limit a maximum transverse displacement of the outside foot in an inside direction. 
     These features, advantages, and alternative aspects of the present invention will be apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention: 
     FIG. 1 is a front and side view in perspective, from an above and outside position, of an embodiment according to the invention. 
     FIG. 2 is a front and side view in perspective, from an above and inside position, of a portion of the embodiment of FIG.  1 . 
     FIG. 3 is a perspective view, from a below and inside position, of the embodiment of FIG.  2 . 
     FIG. 4 is a rear and side view in perspective, from a below and inside position, of the embodiment of FIG.  2 . 
     FIG. 5 is a close-up front and side view in perspective, from an above and outside position, of a portion of the embodiment in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made to the drawings in which the various elements of the invention will be given numerical designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the claims which follow. 
     The invention relates to sewing seams in material. The invention will typically be described from the reference point of material being sewn. That is, directions are described from the material&#39;s perspective. An outside direction may be characterized by a vector pointing from the material toward an edge, typically the edge being sewn. Similarly, an inside direction may be characterized by a vector oppositely directed from an outside direction. Outboard, or outside, are typically used as relative locations and may indicate being located away from the material, or simply more toward such location than a reference location. A seam size is defined as the distance from a closest edge of the material to the stitches forming the seam. 
     The principal working components of a currently preferred embodiment of the invention, generally indicated at  10 , are illustrated in FIG.  1 . The seam adjustment device  10  includes an edge guide  102 , a sensor, generally indicated at  110 , and a displacement transducer, generally indicated at  120 . A seam adjuster  10  also desirably includes an outside foot, generally indicated at  125 , adapted to accommodate a transverse displacement. Certain of these components can conveniently be carried on a slide plate  127  for installation on a commercial sewing machine. 
     Edge guide  102  can function as a brace element against which material to be sewn is placed by a sewing machine operator. Typically, a small amount of outwardly directed pressure is exerted by the operator on the material to maintain the material against the edge guide  102 . As the material is sewn, the seamed edge passes past sensor  110  which validates the correct seam size. Edge guide  102  may be transversely located to position the guide surface a desired distance transverse and outboard to a sewing needle and at the correct distance to form a desired seam size. The edge guide  102  is configured and arranged for its position, relative to a sewing needle, to be adjusted by transducer  120 . Automated adjustment of a position of the edge guide  102  is controlled by a feedback loop based upon seam size. 
     Illustrated sensor  110  includes light-based sending unit  130  and a light receiving unit  133 . As illustrated, light carried by pipe  135  passes through sending unit  130 , is scattered, refracted, and reflected, with a portion being subsequently received by receiving unit  133 . The return signal from unit  133  is carried by light pipe  137  and is used to operate switch  139 . 
     When the sewn edge is in compliance for size, switch  139  is typically in an open configuration. When the seam goes out of compliance, because sensor  110  indicates the seam is too wide, switch  139  closes, and sends an adjustment signal through cable  142  to adjust the seam width. Cable  142  may carry the adjustment signal to a power supply  145  to boost the signal subsequently sent to a control switch, generally indicated at  149 . However, the boost from a power supply  145  may not be required in certain embodiments of a seam adjuster  10 . In the latter case, the signal may be sent from switch  139  directly to operate a transducer to adjust seam size. 
     As illustrated in FIG. 1, the boosted signal is transmitted from power supply  145  through cable  152  to operate valve  155 . When valve  155  is opened, a fluid is permitted to flow through line  157  and operate displacement transducer  120 . Fluid is typically supplied from a fluid source  161  and brought to a convenient location on, or near, a sewing machine through supply line  163 . A currently preferred fluid is compressed air, although hydraulic fluids are also operable. The illustrated displacement transducer  120  is an air driven piston  170 . The invention is not limited to use of such piston type displacement transducers. Alternative transducers within contemplation to adjust a position of edge guide  102  nonexclusively include individually or in combination: linear motors, rack and gear linkages, single and multibar linkages, cams, cams and followers, DC motors, stepper motors, and any other workable arrangement to convert some form of energy into a transverse displacement of the edge guide  102 . 
     FIGS. 2-5 illustrate certain operational details of the invention. A stationary clamping foot  175  of a commercially available sewing machine is modified to have an independent inside foot  177  and an outside foot  179 . In accordance with conventional sewing machines, stationary foot  175  operates to hold the material being sewn in clamped engagement with the slide plate  127 . Walking foot  183 , in combination with a feed mechanism located under the material (not shown), operates to feed material past needle  185  for stitching. 
     With reference now to FIG. 4, outside foot  179  desirably is adapted for transverse displacement toward and away from needle  185 . One way to accommodate such transverse motion is achieved by suspending outside foot  179  from inside foot  177  with a suspension mechanism, generally indicated at  189 . Alternatively, an outside foot  179  may be suspended from other portions of a sewing machine. As illustrated, suspension mechanism  189  includes a rail  193  which is arranged in sliding capture through inside foot  177 . Rail  193  can be adapted, as illustrated, to form a forward protruding lever portion to assist in positioning an outside foot  179 . Other conformations of suspension systems are within contemplation, nonexclusively including sliding journalled elements, dovetail joints, pivoting rods, and multibar linkages. 
     One or more biasing elements, such as spring  195 , are typically included to bias outside foot  179  in an outboard direction. Outside foot  179  may then be placed into engagement with surface  196  of edge guide  102  when adjusting a sewing machine to sew a given seam size. However, outside foot  179  does not necessarily have to be in engagement with surface  196  for the invention to be operable. Outside foot  179  functions to maintain material in a substantially flat orientation between edge guide  102  and a needle  185 . A transverse displacement of edge guide  102  therefore moves the material by a corresponding amount to adjust a seam size. It is within contemplation for outside foot  179  to be replaceable with alternative outside feet which are either wider or more narrow than illustrated. Wide feet  179  may be more appropriate when sewing wide seams, and narrow feet  179  may be more appropriate when sewing narrow seams. 
     A stop mechanism, such as screw  197 , may be arranged to limit a transverse displacement of outside foot  179  in an inside direction. As illustrated, end  199  of screw  197  is spaced apart from inside surface  201  of outside foot  179 . Stop mechanism  197  desirably is adjustable to provide a range in maximum inward displacement values for outside foot  179 . 
     FIG. 5 illustrates certain distance relationships in one embodiment of the invention. When setting up a sewing machine to sew a seam, edge guide  102  is positioned at a distance D 1  from a centerline of needle  185 . D 1  therefore corresponds to the seam size. Outside foot  179  has a width D 2 , leaving a space between it and walking foot  183  indicated by D 3 . Stop  197  is set to limit displacement of outside foot  179 , by a distance less than D 3 , to prevent contact between outside foot  179  and walking foot  183 . Typically, stop  197  is set to limit an inward displacement of edge guide  102  to a minimum value determined to be sufficient to make a seam size correction, “steering” the material back into seam size compliance. Such “steering” displacement is typically less than the distance indicated by D 3 . Factors affecting a steering displacement include the material type, thickness, weight, and texture. A steering displacement may be generally set at a certain percentage of a seam size. A steering displacement may also be determined by a maximum amount of travel permitted by the displacement stroke of an edge guide  102 . A transducer  120  may be provided having an adjustable stroke, or a stop mechanism may be set to operate on the edge guide  102  directly. 
     The position of a sensor  110  is desirably adjustable to locate the sensing zone  205  at a distance transverse to a sewing machine needle  185  corresponding to the desired seam size. As with the edge guide  102 , a component&#39;s position may be maintained by tightening bolts  207  or  209  subsequent to moving the component into its desired position. A position may be measured relative to a sewing needle  185  by use of a tape measure, or other measuring device. It is also within contemplation for a vernier scale to be incorporated into a slide plate  127  to assist in adjusting a sewing machine for a desired seam size. Other calibrated mechanisms to adjust an edge guide or sensor  110  to a position may include rotating dials or mechanisms adapted to provide audible or mechanical feedback (e.g., “click”) at discrete intervals. 
     It is preferable for the sensing zone  205  of a sensor  110  to be positioned in stitched proximity and fairly close to the needle  185 . That is, the sensor  110  is usually positioned to observe (for feedback) a portion of material in which a seam has just been stitched. A close location to the needle  185  provides feedback of seam size in time to effect a correction in such size before creating scrap, or requiring shutdown of the sewing machine. 
     It is within contemplation to use alternative sensor arrangements, other than illustrated in the figures, for seam size feedback. For example, a single light-based sensor may be self-contained to provide both sending and receiving functions. Other alternative sensors within contemplation include capacitive sensors, direct displacement transducers, other laser or LED-based sensors, sensing arrays, or any other sensor capable of indicating the location of an edge of sewn material. A pair of sensors may be used in harmony, with one sensor observing the stitches, and another simultaneously observing the finished edge to create a pair of signals having information with which a seam size may be calculated, and the information used in a feedback loop. A proportional control and feedback also can be employed to operate the invention. In such a case, larger displacement is applied in correspondence with an increased error in seam size. 
     While the invention has been described in particular with reference to certain illustrated embodiments, such is not intended to limit the scope of the invention. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.