CANVAS STRETCHING SYSTEM WITH CORNER CLAMPS

BACKGROUND OF INVENTION:

1. Field of invention

This invention relates to frames that are used to mount and to provide tension for flexible fabrics, such as artists canvasses, silk screen, digital photograptis. and the like. In particular this invention relates to special purpose corner clamps that allow for the use of adhesive to attach the canvas to the stretcher bars.

2. Description of the related Art

Most prior art stretchers are manufactured as standard dimension lengths with machined ends. These lengths are assembled into frames with interlocking corners. The canvas or material is stretched on this frame using stretching pliers and with staples on the side. Wedges can be inserted into the interlocking corners to expand the frame and tension the canvas. Stretcher bars of this type have a few disadvantages:

1. When first assembled the stretcher bars must be squared and aligned b> the user or the diagonals will be off. making subsequent framing difficult or impossible.

2. The stretching of the material on the stretcher bars requires the use of specific tools like stretching pliers and staple guns, both of which are costly and might not be available in the average consumer ^' s household.

3. When stretching the material with pliers it is very difficult to apply an even tension along every side of the material and this can cause undue siress on the

stretcher bars, quite often causing the frame to warp and the material to wrinkle.

4. This stretching system requires a fair amount of skill, strength and practice in order to get good results. Thus it is intimidating and not user friend]} .

5. In this type of stretching system, the staples are normally placed on the side of the stretcher bars which makes the side edges of the material unsighth .

6. The corners of the material must be folded and fastened on the sides, adding bulk and detracting further from the neat edge appearance of the finished product.

7. The sophisticated nature of the machined ends of the stretcher bars do not allow for resizing and therefore cannot be used if the dimensions of the material to be stretched does not fall within the standard sizes currently being manufactured.

8. Currently available stretcher bars allow for expansion with the use of wedge inserts into the interlocking corners. These inserts, however, are often missing from the corners making it impossible to retighten the comers without them.

9. A lot of material is wasted due to the fact that the stretching pliers need extra material around the frame to grab onto.

It is an object of the present invention to overcome the disadvantages described and provide a canvas stretching system which can be easily used by the novice framer..

SUMMARY OF THE INVENTION

[Insert claim 1 and independent claims here]

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will nov\ be described with reference to the following drawings in which:

FlG l (a) is a top view of the locking corner clamp used for holding the streicher bars square and secure in the open miter position according to one embodiment of the present invention.

FlG l(b) is a right side view of the locking corner clamp used for holding the stretcher bars square and secure in the open miter position according to one embodiment of the present invention.

FIG l (c) is a bottom side view of the locking corner clamp used for holding the stretcher bars square and secure in the open miter position according to one embodiment of the present invention.

FIG 2 (a) is an cut-away side view of typical stretcher bars.

FIG 2 (b) is a bottom cut-awa\ view of typical stretcher bars.

FIG 2 (c) is an inside edge cut-awa\ viev\ of typical stretcher bars.

FIG 2 (d) is a top cut-away view of typical stretcher bars.

FIG 2 (e) is a left end cut-away view of typical stretcher bars.

FIG 3 is an perspective view of a locking corner clamp showing one stretcher bar

inserted.

FIG 4(a) is a top view of the assembled stretcher bars in the open miter position using the locking coiner clamps. The adhesive strips are exposed and read} to adhere to the canvas or material (not shown).

FIG 4(b) is a front side view of the assembled stretcher bars in the open miter position using the locking corner clamps. The adhesive strips are exposed and read} to adhere to the canvas or material.

FIG 5 is a perspective view of the stretcher bars in the open miter position placed over the canvas or material which is placed face down and read} to adhere 1 o the adhesive strips on the stretcher.

FIG 6 is a side view of the stretcher bars in the open miter position placed over the canvas or material, showing the spacing between the stretchers and the cam as so the alignment can take place before the adhesive comes into contact.

FIG 7 is a perspective view of the stretcher frame in the open miter position adhered to the canvas and the locking corner clamps remoλ ed.

FIG 8 is a perspective view of the folding and adhering of the canvas corners onto the open miters of the stretching frame.

FIG 9 is a perspective view of the top of the stretching frame now rotated into the final (miter closed) position. Also shown is the insertion of the locking fastener and a corner brace.

FIG 10(a) is a top view of the finished stretched canvas with all comer braces and locking fasteners inserted.

FIG 10(b) is a right side view of the finished stretched canvas with all corner braces and locking fasteners inserted.

FIGs 10(c) is a back view of the finished stretched canvas with all corner braces and locking fasteners inserted.

FlG 1 1 (a) is a top view of the spacer block used to allow different width of stretchers to be used with the same locking clamp.

FIG 1 1 (b) is a front view of the spacer block used to allow different width of stretchers to be used with the same locking clamp.

FIG 1 1 (c) is a right side view of the spacer block used to allow different w dth of stretchers to be used with the same locking clamp.

FIG 12(a) is a top side view of the corner clamp with the spacer blanks inserted for the medium width stretcher bar inserted.

FIG 12(b) is a side view of the corner clamp with the spacer blanks inserted for the medium width stretcher bar inserted.

FIG 13(a) is a top view of the corner clamp with the spacer blocks inserted for the

Om i ik ¹ V ! 2 ⁽ )8'^- l ~ narrow width stretcher bar inserted.

FIG 13(b) is a front view of the corner clamp w ith the spacer blocks inserted for the narrow width stretcher bar inserted.

FIG 14(a) shows a top view of an alternate corner clamp configuration with single corner raised platform.

FIG 14(b) shows a right side view of an alternate corner clamp configuration with single corner raised platform.

FIG 15 shows an alternate corner clamp for thin stretcher bars where no raised platform is necessan to maintain the adhesive strip from touching the canvas or material before pressing down.

FIG 16(a) shows a top view of an alternate corner clamp configuration with single comer raised platform.

FIG 16(b) shows a right side view of an alternate corner clamp configuration with single corner raised platform.

FIG 17 shows an alternate corner clamp for thin stretcher bars where no rai ?ed platform is necessan to maintain the adhesive strip from touching the canvas or material before pressing down.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention relates to a canvas stretching system which uses locking corner clamps 50 and four stretcher bars 25 to form a generalh square or rectangular stretcher frame 70. In the first operation, the canvas 20 to be stretched in placed on a flat surface, such as a table (not shown), with the image (such as a painting, silk screen, digital photograph, and the like) facing downwards. The corner clamps 50 are placed a few inches inside the corner of the canvas 20. The four stretcher bars 25 are inserted into the respective cavities 4 of the corner clamps 50 in an initial open miter position in such a way that they are square and properh placed relative to each other to form the stretcher frame 70. Each stretcher bar 25 has an adhesive strip 7 which faces the material 20 to be stretched. The corner clamps 50 are also designed to keep the stretcher frame 70 from touching the canvas 20 when mounting thus allowing for easy alignment. When the stretcher frame 70 is in the right position over the canvas 20 the stretcher bars 25 are pressed down and the adhesive strip 7 on the stretcher bars 25 comes into contact with the canvas20 . The locking corner clamps 50 an; removed and the corners of the canvas or material 20 are cut and adhered to the adhesive strip 7 on the exposed miters. The stretchers bars 25 are rotated along their longitudinal axis into their final position. The rotation of the stretcher bars 25 and the interference of the material inside the miters will stretch the canvas 20 resulting in a very uniform tension along every side of the stretching frame 70. A U-shaped fastener 1 3. such as a staple, is inserted into grooves 12 on the stretcher bars 25 and is used to counteract the tension of the canvas 20 in order to keep the stretcher frame 70 closed.

Braces 40 can be inserted into the groove 15 on the inside face opposite to the outer edges of the stretching frame 70 to add stiffness and alignment to the final product. These braces 40 can be further used to increase the tension of the canvas or material 20 by being drawn towards the corners to which the}" are affixed.

Figure 1 shows a top \ iew of the corner clamp 50. The raised mitre stop 1 is used in the corner clamp 50 as a register stop for ends of the stretcher bar 25 (Fig. 3 ) to ensure that the open miter ends 10 are positioned correcth relative to each other. The tabs 2 utilize the resiliency of the material 20 (Fig. 4) to clamp the streicher bars 25 (Fig. 3) and hold them secureh in place. The cavit\ 4 between the tabs 2 must be slightly narrower than the width of the stretcher bar 25 in order for the tabs 2 to deflect properly and clamp the stretcher bars 25 securel) . The raised stabilising platform 5 is used along with raised mitre stop 1 to keep the adhesive strip 7 (Fig. 2 & 3) from touching the canvas 20 and to keep the comer clamp 50 from twisting when it is pressed down.

Figure 2 shows a sideview of a typical stretcher bar 25. An adhesive strip 7 is applied to the stretcher bars 25 on the side that is to be adhered to the canvas or material 20 (Fig. 3). which will be the outer perimeter of the closed stretching frame 70 formed b> the four stretcher bars 25. The adhesive strip 7 also wraps around the open miters 10 of the stretcher bars 25. The typical stretcher bar 25 will have a groove 15 on its ^' inside face to accept a brace 40 to secure and strengthen the finished stretching frame 70. A bead 1 1 on the top of the stretcher bar 25 will keep the canvas 20 away from the inside edge 14 of the stretcher bars 25 to prevent a crease on the image of the finished stretcher frame 70. Grooves 12 are provided to insert the "U" shaped closing fasteners 13 on the back of the stretching frame 70.

Figure 3 shows a perspective view of the corner clamp 50 with the stretcher bar 25 inserted in the cavity 4 on one side. The end of the miter 6 of the stretcher bar 25 is pushed against the raised mitre stop 1 for correct positioning. The raised mitre stop 1 must be higher than the back of the stretcher bar 25 to keep the adhesive strip 7 from touching the back of the canvas 20 for easλ alignment. Tabs 2 hold the stretcher

bar 25 secure!} in place.

Figure 4 shows the stretcher bars 25 held in the open miter position b\ the corner clamps 50. The corners 8 of the stretcher bars 25 must meet in order to achieve proper tension of the canvas 20. The adhesive strips 7 are exposed and ready to fasten to the canvas 20.

Figure 5 shows the stretcher bars 25 in place and aligned over the back of the canvas 20.

Figure 6 shows the space 19 between the stretcher bars 25 and the canvas 20. A downward push on the stretcher bars 25 will adhere them to the canvas 20 by means of the adhesive strip 7.

Figure 7 shows the stretcher bars 25 adhered to the back of the canvas 20 with the corner clamps 50 removed, exposing the adhesive strips 10 on the open miters.

Figure 8 shows the corners 17 of the canvas 20 cut folded and adhered onto adhesive strips 10 on the open miter ends 16.

In Figure 9 the stretcher frame 70 has been rotated into the (closed miter) final position. The U-shaped closing fastener 13 are inserted into the fastener grooves 12 of the stretcher bars 25 to keep the frame 70 in the closed position. The comer braces 40 are inserted into the inner grooves 15 of stretcher bar 25 to add stiffness and allow for increased tension of the canvas 20.

Figure 10 shows a top view of the finished stretcher frame 70 with tne corner

braces 40 inserted.

Figure 1 1 shows a spacer block 30 used to allow different width of stretcher bars 25 to be used with the same locking corner clamp 50. Spacer block 30 has a groove 34 which is dovetail shaped and slides over tab 2 of the corner clamp 50. The spacer block 30 has two sides of different thicknesses. Side 31 is used for narrow width stretcher bars 27 and side 32 is used for medium width stretcher bars 26.

Figure 12 shows a top and side view of the corner clamp 50 with spacer blocks 30 inserted for the medium width stretcher bar 26. The spacer block 30 slides onto tab 2 with side 32 facing the back of stretcher bar 26 in such a way that this width of stretcher bar 26 is held secureh .

Figure 13 shows a top and side view of the corner clamp 50 with spacer blocks 30 inserted for the narrow width stretcher bar 27. The spacer block 30 slides onto tab 2 with side 31 facing the back of stretcher bar 27 in such a way that this width of stretcher bar 27 is held secureh'.

Figure 14 shows an alternate comer clamp configuration with single raised mitre platform 1.

Figure 15 shows an alternate corner clamp 52 narrow stretcher bars 27. In this configuration the outer face of stretcher bar 27 falls below the tops of tabs 2 and the raised mitre stop 1. This will keep the adhesive 7 on stretcher bar 27 from ¹ ouching the canvas 20 when mounting, and therefore a raised mitre stop 1 is not necessary.

It will be clear to a person skilled in the art that modifications could be made

to the above-identified description without departing from the scope of the invention.