Clamp bar for fabrics

[57] ABSTRACT

A clamp bar for fabrics consisting of a straight bar having a straight top shoulder to which the edge of a large sheet of fabric may be drawn, and a series of clamps carried at intervals along the bar for clamping the fabric thereto. The clamps are operated by compressed air, and each is actuated to clamp the fabric by pressing it manually toward its operative position, whereupon the compressed air takes over to hold it in position. All of the clamps may be released simultaneously by pressing a pushbutton valve.

Claims, 7 Drawing Figures

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PATENTED J*N 211STS

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3,861,663

CLAMP BAR FOR FABRICS

This invention relates to new and useful improvements in fabric handling equipment, and has particular reference to a device for clamping an edge of a large sheet of fabric to a straight bar, so that the fabric may be drawn across a supporting surface, such as a large table, so that operations such as cutting, hemming, or the like may be performed on its opposite edge with the assurance that the edge on which said operations are being performed is truly parallel to the clamped edge. Clamp bars of this general type are used, for example, to insure parallelism of a cut or hemmed edge of a drapery panel in relation to a previously cut or hemmed opposite edge. The difficulties of handling very large sheets of fabric under these circumstances are well known. In draperies, the edge to be cut or hemmed may be 32 feet long or even longer. But while the present device has been conceived primarily for use in drapery forming operations, it will be readily apparent that it has general applicability in many fields.

A principal object of the present invention is the provision of a fabric clamp bar consisting of a bar along which an edge of a large sheet of fabric may be arranged in an accurately straight line, and a series of clamps carried in spaced relation along the length of said bar and each operable to clamp the fabric to the bar.

Another object is the provision of a clamp bar of the character described in which the clamps are compressed air-actuated, but may be individually actuated simply by pressing each clamp toward its operative position against a spring, the compressed air taking over automatically at a predetermined point to complete the setting of the clamp. In this manner, the operator may use one hand to align that portion of the fabric to be engaged by a particular clamp, and the other hand to actuate the clamp.

A further object is the provision of a fabric clamp bar of the character described wherein the clamps, though individually actuated, may be released simultaneously simply by pressing a pushbutton.

Other objects are simplicity and economy of construction, efficiency and dependability of operation, and adaptability for use in a wide variety of applications.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. 1 is a front elevational view of a portion of a fabric clamp bar embodying the present invention,

FIG. 2 is a top plan view of the fabric clamp bar as shown in FIG. 1,

FIG. 3 is an enlarged sectional view taken on line III—III of FIG. 1, showing one of the clamps in its released position,

FIG. 4 is a fragmentary view similar to FIG. 3, with the clamp at an intermediate stage in the actuation thereof,

FIG. 5 is a view similar to FIG. 3, showing the clamp fully engaged,

FIG. 6 is a fragmentary sectional view taken on line VI—VI of FIG. 4, and

FIG. 7 is an enlarged sectional view taken on line VII-VII of FIG. 2.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies to a table or other supporting surface over which it may be desired to draw a large sheet of fabric 4 by means 5 of a clamp bar device indicated generally by the numeral 6, and consisting of an elongated base bar 8 lying on and movable over the table surface, and means for clamping an edge of the fabric to said bar. The base bar may be mounted on and movable over the table sur10 face, usually by power means insuring parallelism of the bar to an edge of the table, but such bar mounting and moving means are not pertinent to the present invention, and are not shown. The base bar is provided with a longitudinally extending, forwardly facing shoul15 der 10 against which an edge of fabric 4 may be drawn to insure straight, linear positioning of said fabric edge, the top surface of the bar providing a horizontal ledge 12 forwardly of shoulder 10, with its extreme forward edge portion being bevelled as indicated at 14.

The fabric 4 is adapted to be clamped to ledge 12 by means of a series of foot bars 16 arranged parallel to base bar 8 thereabove, said foot bars being disposed directly above ledge 12 and spaced in a series along base bar 8. Each foot bar may be about 9 inches long, with ²⁵ 2 inches between adjacent ends thereof, although this spacing is of course optional. Clamp bars 30 to 40 feet long are not uncommon. Each foot bar is rigid, though it may be covered with a smooth plastic material, not shown, to prevent snagging or tearing of the fabric, and ³θ is movable downwardly from an elevated position well above ledge 12, as shown in FIG. 3, to a position clamping fabric 4 against ledge 12, as shown in FIG. 5.

Each foot bar 16 is supported by a vertically yieldable spring yoke 18 from the forward end of a rigid hor³⁵ izontal arm 20, said arm extending rearwardly from said yoke and entering a vertically elongated slot 22 formed in a tubular post 24, said post being fixed at its lower end in bar 8 behind shoulder 10 thereof. Said post acts as a pneumatic cylinder, and is sealed at its ⁴⁰ upper end. Within each post, the rearward end of the associated arm 20 is affixed, as by set screw 26, in the lower end of a pneumatic piston 28 carried operably in said post. Said piston is biased upwardly in the post by a compression spring 30. The upper portion of the pis45 ton is bored out as indicated at 32 to be hollow, and is provided with a side air passage 34 at the bottom of the bore thereof. Air passage 34 cooperates with a vertically elongated vent slot 36 formed in the wall of post 24, in a manner to be described. Each post 24 is also ⁵⁰ provided with a side air inlet port 38 spaced below the upper end thereof, the ports 38 of all of the posts being interconnected by branch pipes 40 with a common air supply pipe 42 which extends horizontally behind posts 24 the full length of the base bar. At one end of the ⁵ base bar, pipe 42 is connected through a pressure release valve 44 to a pipe 46, which in turn is connected by a hose 48 to any suitable source of compressed air, not shown. Hose 48 is flexible to permit ready movement of the base bar over the table.

As best shown in FIG. 7, release valve 44 includes a valve body 50 having therein a slidable plunger 52 having a passageway 54. The plunger is normally biased by spring 56 to the position shown, wherein passageway 65 54 interconnects pipes 46 and 42, but may be moved ³ against spring 56 by manual pushbutton 58 to a position in which pipe 46 is sealed off, and passageway 54 interconnects pipe 42 to a vent hole 60 formed in the

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a. an elongated base bar over which the edge portion of said fabric sheet may be laid,

b. a series of clamp devices mounted on said base bar in spaced relation therealong and each including a 5 foot bar movable between an elevated position well above said base bar and a lowered position wherein it clamps said fabric against said base bar, and

c. operating means operable to move said foot bars selectively between said elevated and lowered posi10 tions, said operating means for each foot bar including power means operable when actuated to lower said foot bar to its lowered position, and means operable by manual lowering of said foot bar a predetermined proportion of its travel to said 15 lowered position to actuate said power means.

2. A clamp bar as recited in claim 1 wherein said power means for each of said clamp devices comprises:

a. spring means normally biasing the associated foot bar to its elevated position,

b. air pressure-actuated means operable when supplied with air under pressure to lower said foot bar to its lowered position,

c. air pressure control means operable by manual lowering of said foot bar through a portion of its 25 movement, against said spring means, to supply air under pressure to said air pressure-actuated means, and

d. manually operable means for exhausting air from said air-pressure actuated means.

3. A clamp bar as recited in claim 2 wherein said manually operable means for exhausting air from said air pressure-actuated means is operable to exhaust air simultaneously from the air-pressure actuated means of all of said clamp devices.

4. a clamp bar as recited in claim 1 wherein each of said clamp devices and its operating means comprises:

a. a vertical pneumatic cylinder fixed at its lower end in said base bar and sealed at its upper end.

b. a piston vertically movable in said cylinder ⁴⁰ c. an arm fixed to said piston and projecting outwardly through a vertically elongated slot of said cylinder, the associated foot bar being carried at the outer end of said arm, and

d. spring means biasing said piston upwardly in said ⁴⁵ cylinder to raise said foot bar to its elevated position, said cylinder being provided with an air inlet port connected to a source of air under pressure, said inlet port being sealed by said piston when in said elevated position but opened to supply air to ⁵⁰ said cylinder above said piston when said piston is moved manually downwardly against said spring means a predetermined portion of its travel to its lowered position.

5. A clamp bar as recited in claim 4 wherein said foot ⁵⁵ bar is connected to the outer end of said arm by means of a vertically yieldable spring.

6. A clamp bar as recited in claim 4 wherein said piston is provided with an air passage opening into said cylinder above said piston and through a side of the pis⁶⁰ ton below the upper end thereof, said cylinder having a side vent opening below said inlet port which cooperates with the side opening of said piston air passage to seal said piston air passage at all positions of the upper end of said piston at or below said inlet port, and to ⁵ vent said piston passage to the atmosphere at all positions of the upper end of said piston above said inlet port.

valve body, whereby pipe 42 is vented to the atmosphere.

In operation, it will be seen that when each clamp is released, it has the position shown in FIG. 3, the foot bar 16 thereof being spaced well above ledge 12 of the base bar, being elevated and retained in this position by spring 30, with arm 20 engaged in the upper end of post slot 22. In this position, the cylinder inlet port 38 is sealed off by the piston, so that the piston is not lowered, and piston air passage 34 is in communication with post vent slot 36, so that any air which might leak past the piston is vented to the atmosphere. The operator then arranges fabric 4 beneath the foot bar, bringing the fabric edge into contact with shoulder 10 of the base bar, and then actuates the clamp to lower the foot bar 16 against the fabric as in FIG. 5.

To actuate the clamp, the operator first manually lowers the foot bar against the pressure of spring 30, for example by pressing downwardly on arm 20, to the position shown in FIG. 4. This movement may be very easily accomplished, since piston passage 34 is still in communication with slot 36 so that no vacuum can form above the piston, and since spring 30 need be no stronger than is required to elevate and support the weight of the associated piston 28, arm 20, spring yoke 18 and foot bar 16. At the FIG. 4 position, piston passage 34 passes beyond post slot 36 and is sealed off, and the piston uncovers port 38, so that compressed air enters the post above the piston and forces said piston downwardly until foot bar 16 clamps fabric 4 firmly against ledge 12 as in FIG. 5. The downward motion of arm 20 is limited by engagement thereof in the lower end of slot 22. In the FIG. 5 position, it will be seen that spring yoke 18 has yielded to some degree. This yieldability of the yoke permits the foot bar to better adapt to the fabric surface, for example if the fabric is folded, and also prevents possible injury to the operator in the event he has a finger under the foot bar as the piston is lowered past the FIG. 4 position. It will thus be seen that each clamp may be actuated separately as needed, and this is considered to be advantageous singe large sheets of pliable fabric are notoriously hard to handle, and the present arrangement permits it to be positioned one section at a time proceeding from one end of a long edge, with each section being clamped in place as it is positioned.

The clamps are all released simultaneously by momentary pressure on pushbutton 58 of release valve 44. This vents all of the air cylinder posts to the atmosphere, so that the pistons are elevated by springs 30. During the initial portion of the rise of each piston, until it is raised to the FIG. 4 position, air is vented through ports 38. At the FIG. 4 position, the piston seals port 38, but piston passage 34 then interconnects with slot 36, so that the piston can complete its upward movement with no possibility that impeding air pressure can form thereabove.

While I have shown and described a specific embodiment of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention.