Abstract:
An embroidery frame is disclosed which is detachably attached to an embroidery unit and provided with outer and inner frames that clamp therebetween an embroidery cloth extending across an underside of the inner frame. The embroidery frame includes a first inclined surface which is provided at least on a part of a cloth-clamping surface of the outer frame that holds the cloth between the inner and outer frames, and which is upwardly inclined toward an inside of the outer frame. The embroidery frame further includes a second inclined surface which is provided in a portion of the cloth-clamping surface of the inner frame corresponding to the first inclined surface, the inner frame holding the cloth between the outer and inner frames, and which is upwardly inclined toward an inside of the inner frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-339344, filed on Nov. 24, 2004 the entire contents of which are incorporated herein by reference. 
   BACKGROUND 
   The present disclosure relates to an embroidery frame that holds a workpiece cloth to be sewn between an outer frame and an inner frame. 
   TECHNICAL FIELD 
   Conventional embroidery frames have generally been constructed by an outer frame and an inner frame. Tension is applied to workpiece cloth placed on the outer frame by pressing the inner frame into the outer frame. A fastening screw is provided on the outer frame, and the fastening screw is tightened so that the workpiece cloth is clamped between the outer and inner frames. 
   The embroidery frame having the above construction is disclosed, for example, in JP-U-7-15793. The outer frame of the embroidery frame is provided with a scale corresponding to a thickness of the workpiece cloth. An end of the fastening screw is aligned with the applicable scale in tightening the fastening screw. 
   The embroidery frame is attached to an embroidery frame driving mechanism of a sewing machine, which is capable of embroidery sewing with the workpiece cloth clamped between the outer and inner frames. By moving the embroidery frame independently in two mutually perpendicular directions by the embroidery frame driving mechanism, embroidery is formed on the workpiece cloth. 
   The above-described embroidery frame includes embroidery frames in an oblong form having a pair of circular-arc ends which are connected by a pair of substantially straight portions or substantially rectangular forms having a pair of long sides and a pair of short sides. For example,  FIG. 12  is a longitudinal side section of a substantially rectangular embroidery frame  100 . As shown in  FIG. 12 , the embroidery frame  100  is constructed by an inner frame  101  and an outer frame  102  that clamp a workpiece cloth  103  therebetween. A cloth-clamping surface  101   a  of the inner frame  101  and a cloth-clamping surface  102   a  of the outer frame  102  are arranged so as to be perpendicular to the upper or the lower surface of the inner frame and the outer frame respectively. 
   However, in the embroidery frame  100  having the above described construction, there are cases where long sides  101   b  of the inner frame  101  are deformed so as to be bent in the upward direction by the tension of the workpiece cloth  103 . When the long sides  101   b  of the inner frame  101  are thus deformed so as to be bent upwards, the workpiece cloth  103  cannot securely be clamped by the inner and outer frames  101  and  102 , and the embroidery area of the workpiece cloth  103  cannot be retained in a flat state. Hence, embroidery sewing performed under such a condition results in a shrinking of the workpiece cloth, thereby deforming the embroidery pattern and reducing the sewing quality. 
   Furthermore, in the above embroidery frame  100 , as shown in  FIG. 13 , when a fastening screw  104  is loosened and the outer frame  102  is spread, the shape of the inner periphery of the outer frame  102  and the shape of the outer periphery of the inner frame  101  are not similar. Therefore, it is difficult to accurately determine the location in which the inner frame  101  is to be fitted with the outer frame  102 , which is located below the workpiece cloth  103 ; and in some cases, the workpiece cloth  103  is clamped with the inner frame  101  misplaced with respect to the outer frame  102 . In such a case, since the workpiece cloth  103  is not evenly held between the cloth-clamping surfaces  101   a  and  102   a  of the inner and outer frames  101  and  102 , embroidery sewing performed under such a condition again results in the shrinking of the workpiece cloth, consequently deforming the embroidery pattern and impairing the sewing quality. 
   The above described problem occurs also in substantially elliptic embroidery frames or in oval-form embroidery frames. 
   SUMMARY 
   Therefore the object of the present disclosure is to provide an embroidery frame that prevents the upward-bending deformation which is caused by the tension of the workpiece cloth. 
   An embroidery frame of the present disclosure is detachably attached to an embroidery unit and is provided with an outer frame and an inner frame that clamp embroidery cloth. The embroidery frame comprises a first inclined surface which is provided at least on a part of a cloth-clamping surface of the outer frame that holds the cloth between the inner and outer frames, and which is upwardly inclined toward an inside of the outer frame; and a second inclined surface which is provided in a portion of the cloth-clamping surface of the inner frame corresponding to the first inclined surface, the inner frame holding the cloth between the outer and inner frames, and which is upwardly inclined toward an inside of the inner frame. 
   According to the above-described construction, when the cloth to be embroidered is clamped between the outer and inner frames, the first inclined surface of the outer frame contacts the second inclined surface of the inner frame from the obliquely upward direction. Therefore, even if a force to transform the inner frame in the upward direction is operated on the inner frame by the cloth tension, the outer frame does not allow the upward transformation of the inner frame, and the cloth can be securely clamped between the outer frame and the inner frame. Also, since the embroidery area portion of the cloth can be retained as a flat surface, the quality of the embroidery pattern formed on the embroidery area portion can be improved. 
   In this case, when the outer and inner frames are each formed in a substantially elliptic or oval form that has a circular-arc portion and a substantially straight portion, the first and second inclined surfaces are desirably provided on the cloth-clamping surface of the substantially straight portion of the outer frame and the cloth-clamping surface of the substantially straight portion of the inner frame respectively. 
   Also, in case the outer and inner frames are each formed in a substantially rectangular form having a long side and a short side, the first and second inclined surfaces are desirably provided on the cloth-clamping surfaces of the long sides of the outer and inner frames respectively. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the illustrative aspects with reference to the accompanying drawings, in which, 
       FIG. 1  shows a plan view of an embroidery frame according to a first illustrative aspect of the present disclosure; 
       FIG. 2  shows a plan view of an outer frame; 
       FIG. 3  shows a plan view of an inner frame; 
       FIG. 4  shows a longitudinal sectional side view of the embroidery frame; 
       FIG. 5  shows an enlarged sectional view taken along line  5 — 5  of  FIG. 1 ; 
       FIG. 6  shows an enlarged sectional view taken along line  6 — 6  of  FIG. 1 ; 
       FIG. 7  shows an enlarged sectional view taken along line  7 — 7  of  FIG. 1 ; 
       FIG. 8  shows an enlarged sectional view taken along line  8 — 8  of  FIG. 1 ; 
       FIG. 9  shows an enlarged sectional view taken along line  9 — 9  of  FIG. 1 ; 
       FIG. 10  shows an enlarged sectional view taken along line  10 — 10  of  FIG. 1 ; 
       FIG. 11  shows a plan view of an embroidery frame according to a second illustrative aspect of the present disclosure; 
       FIG. 12  shows a longitudinal sectional side view of a conventional embroidery frame attached with a workpiece cloth; and 
       FIG. 13  shows a plan view of a conventional embroidery frame attached with a workpiece cloth, 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A first embodiment of the present invention will be described with reference to  FIGS. 1 to 10 . In the embodiment, the invention is applied to an embroidery frame attached to an embroidery unit of a sewing machine capable of embroidery sewing. Referring to  FIG. 1 , an embroidery frame  1  according to the present invention is formed in an elongated substantially elliptic form or an oval form; and is constructed by an outer frame  2  and an inner frame  3 , which is attached to the inner side of the outer frame  2  so as to clamp the workpiece cloth. Therefore, an inner peripheral surface of the outer frame  2  is defined as a cloth-clamping surface  2   a  and an outer peripheral surface of the inner frame  3  is defined as a cloth-clamping surface  3   a.    
   The outer frame  2  is formed by a synthetic resin, and as shown in  FIG. 2 , is constructed in an elongate substantially elliptic form having a pair of substantially straight portions  2 A and a pair of circular-arc portions  2 B. In  FIG. 2 , symbol A indicates a range of each substantially straight portion  2 A. 
   The outer frame  2  is provided with a link portion  21 , a fastening screw mechanism  22 , an engagement recess  23  functioning as a locating portions and a plurality of inner frame receiving portions  24   a  formed in a tongue-like form. The link portion  21  is detachably linked to a carriage of an embroidery frame driving mechanism of the embroidery unit. 
   The fastening screw mechanism  22  increases and decreases the width of a splitting portion located near the center of one of the circular-arc portions  2 B of the outer frame  2 , and is provided with an operator  22   a . Before attaching the inner frame  3  to the outer frame  2 , the width of the splitting portion of the outer frame  2  is to be increased by rotating the operator  22   a . Then, after arranging the workpiece cloth  4  in a tensed state by pressing the inner frame  3  into the outer frame  2  along with a workpiece cloth  4 , the operator  22   a  is rotated, and the width of the splitting portion of the outer frame  2  is narrowed. Thus, the workpiece cloth  4  is firmly clamped between the outer and inner frames  2  and  3 . 
   An engagement recess  23  is formed on the inner surface (cloth-clamping surface  2   a ) in the center of the other circular-arc portion  2 B of the outer frame  2 . The engagement recess  23  is provided for locating the inner frame  3  with respect to the outer frame  2  in the predetermined location. 
   The inner frame receiving portions  24   a  are provided on the inner periphery of the outer frame  2 ; specifically near the center of the substantially straight portions  2 A and in the lower portion near the border of the substantially straight portions  2 A and the circular-arc portions  2 B (refer to  FIGS. 7 ,  9  and  10 ). When the inner frame  3  is attached to the outer frame  2 , the inner frame receiving portions  24   a  contact a lower end of the inner frame  3  from the underside and receive the inner frame  3 . Thus, the inner frame  3  is attached to the outer frame  2  in a predetermined vertical location. 
   On the other hand, the inner frame  3  is formed by a synthetic resin. As shown in  FIG. 3 , the inner frame  3  is constructed in an elongated substantially elliptic form having a pair of substantially straight portions  3 A corresponding to the substantially straight portions  2 A of the outer frame  2  and a pair of circular-arcs  3 B corresponding to the circular-arcs  2 B of the outer frame  2 . Symbol A in  FIG. 3  indicates a range of the substantially straight portions  3 A of the inner frame  3 . That is, the range of the substantially straight portions  2 A and the substantially straight portions  3 A are the same. 
   A substantially oblong opening is formed in the inner side of the inner frame  3 , and embroidery can be formed on the portion of the workpiece cloth  4  that corresponds to the opening when the workpiece cloth  4  is clamped between the outer and inner frames  2  and  3 . 
   The substantially straight portions  3 A of the inner frame  3  are formed so that the widths gradually increase toward the center thereof from the lengthwise ends for securement of rigidity. Also, the circular-arcs  3 B of the inner frame  3  are formed so that the widths rapidly increase toward the center from both ends of the circular-arc portion for securement of rigidity. 
   One of the circular-arc portions  3 B corresponding to the circular-arc  2 B of the outer frame  2  is formed with a centrally located protrusion  31  functioning as a locating portion to be engaged to the engagement recess  23 . The protrusion  31  is formed across the entire vertical direction of the cloth-clamping surface  3   a  of the inner frame  3 . 
   As shown in  FIGS. 5 to 8 , the cloth-clamping surfaces  2   a  and  3   a  of the substantially straight portions  2 A and  3 A of the outer frame  2  and the inner frame  3  are constructed as an inclined surface upwardly inclined, for example, 10 to 20 degrees toward the inner side of the embroidery frame  1 . That is, the cloth-clamping surfaces  2   a  and  3   a  correspond to the first and the second inclined surface of the present invention respectively. As opposed to this, as shown in  FIG. 4 , the outer and inner frames  2  and  3  include portions other than the substantially straight portions  2 A and  3 A, that is, the cloth-clamping surfaces of the circular-arc portions  2 B and  3 B formed on surfaces perpendicular to the upper or lower surface of the outer and inner frames  2  and  3  respectively. 
   Therefore, when the workpiece cloth  4  is clamped between the outer and inner frames  2  and  3 , the cloth-clamping surface  2   a  of the straight portion  2 A of the outer frame  2  contacts the cloth-clamping surface  3   a  of the straight portion  3 A of the inner frame  3  from the obliquely upward direction via the workpiece cloth  4 . Hence, even if the tension of the workpiece cloth  4  operates, upward-bending deformation of the straight portion  3 A of the inner frame  3  is restrained by the outer frame  2 , and both the outer frame  2  and the inner frame  3  can be kept in a horizontal state as shown in  FIG. 4 . Also, upward movement of the inner frame  3  by the tension of the workpiece cloth  4  is also restrained by the outer frame  2 . 
   Furthermore, upon attachment of the inner frame  3  to the outer frame  2 , the protrusion  31  is arranged to be engaged to the engagement recess  23  of the outer frame  2 . Thus, the inner frame  3  can be attached to the outer frame  2  in a predetermined location. Moreover, since the inner frame  3  is arranged to be received by the inner frame receiving portion  24   a  provided on the outer frame  2 , the attachment can be made such that the inner frame  3  has a predetermined relation of vertical location with respect to the outer frame  2 . 
     FIG. 11  indicates a second embodiment of the present invention. Only the difference of the second embodiment from the first embodiment will be described. In the second embodiment, an embroidery frame  10  is formed in a substantially oblong form. That is, the outer and inner frames  12  and  13  of the embroidery frame  10  are provided with a pair of long sides  12 A and  13 A and a pair of short sides  12 B and  13 B respectively. 
   Though, not shown, a whole or a part of the cloth-clamping surface of the long sides  12 A and  13 A are arranged in an upward inclined surface inclined inward to the embroidery frame  10 . Also, an engagement recess  23 A is formed in the substantial lengthwise center of the short side  12 B of the outer frame  12 , and a protrusion  31 A is formed in the substantial lengthwise center of the short side  13 B. Furthermore, though not shown, a plurality of inner frame receiving portions similar to the inner frame receiving portions  24   a  are formed on the long side  12 A of the outer frame  12 . 
   The same operational effect obtained in the first embodiment can be achieved in the above construction as well. 
   The present invention is not limited to the above described embodiments but can be transformed, for example, as follows. 
   A plurality of inner frame receiving portions may be provided on the entire range of the inner periphery of the outer frame spaced apart in predetermined intervals. 
   The present invention is not limited to a substantially elliptic form and a substantially oblong embroidery frame but can also be applied to a circular embroidery frame. In such a case, it is preferable to arrange each of the cloth-clamping surfaces of the outer and inner frames entirely as a inclined surface, however, only a part of the cloth-clamping surface may be arranged as a inclined surface. 
   The engagement recess functioning as a locating portion can be provided on the inner frame and the protrusion can be provided on the outer frame. 
   The foregoing description and drawings are merely illustrative of the principles of the present disclosure and are not to be construed in a limited sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the disclosure as defined by the appended claims.