Ultrasonic Perforating Of A Sheet Of Film, Paper Or The Like

Abstract

A hole is punched through a sheet of photographic film or paper by positioning the sheet with one side in contact with a punch, and applying an ultrasonically vibrating horn to the opposite side to force the punch through the sheet. A long web of such material can be passed continuously past a horn while a series of punches are successively brought into register with the horn to pierce a series of spaced holes. Such a series of punches can be carried by a rotating cylindrical anvil over which the web is passing. Cores from the holes are sucked away from the operation, any cores remaining within punches first being expelled by fingers within the punches. The punches can move back and forth radially of the cylindrical anvil. A recess in the horn is adapted to receive the protruding ends of punches.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel method of and apparatus for perforating a sheet of material such as photographic film or paper, or similar material.

2. The Prior Art

In the past webs of such material have been perforated along one or both edges by the intermittent operation of a punch and die set, with periodic indexing of the web. Other methods for perforation have involved laser beams and electrical discharge means. The most commonly used are punch and die combinations because of the great accuracy that can be obtained. However, the speed of operation is lower than desirable, intermittent movement of the film rather than continuous movement is required, a substantial quantity of undesirable dust is created, and separation of coated layers from one another may occur adjacent each hole when punching photographic film or paper.

SUMMARY OF THE INVENTION

In accordance with the present invention the disadvantages discussed above have been overcome by positioning a sheet of film or paper with one side thereof in contact with a punch, and then applying an ultrasonically vibrating horn to the opposite side of the sheet to force the punch through the sheet. The horn vibrates at between about 20 and about 40 KHz or more, and consequently not only exerts a mechanical force against the film but also heats it locally so as to soften the material and reduce energy requirements, while also reducing the possibility of dust being formed. The procedural steps just described apply to the perforation of a stationary web as well as to the repetitive perforation of a continuously moving web which is passing across the ultrasonic horn while a series of accurately spaced punches are successively brought into contact with the opposite side of the web.

THE DRAWINGS

The principles of the invention will become apparent from the following description, having reference to the accompanying drawings wherein:

FIG. 1 is a vertical sectional view, partly in side elevation, showing an arrangement of apparatus for ultrasonically perforating a single hole in a sheet of material;

FIG. 2 is a vertical sectional view, parts being in side elevation, schematically showing apparatus for repetitively ultrasonically perforating a series of accurately spaced holes through a continuously moving web of material;

FIG. 3 is a sectional view taken along the line 3--3 in FIG. 2;

FIG. 4 is a sectional view taken along the line 4--4 in FIG. 2;

FIG. 5 is a side elevational view schematically showing apparatus for perforating a continuously moving web; and

FIG. 6 is a schematic side elevational view of another embodiment of the apparatus for perforating a continuously moving web.

THE SPECIFIC EMBODIMENTS

Referring to FIG. 1 there is shown an anvil 11 of a dense rigid material such as steel or other metal, having a hollow punch 13 mounted within a bore therein and protruding above the top surface of the anvil by a distance equal to, or slightly greater than, the thickness of web 15, to be perforated. An ultrasonic horn 17 is positioned with its bottom surface adjacent the top side of web 15, so that when horn 17 is vibrated rapidly up and down by an ultrasonic transducer of a type which is well known, the horn forces web 15 down over punch 13 while at the same time heating the web, thus forming a hole therein.

Ultrasonic transducers and horns suitable for carrying out this operation are well known and have been described in numerous patents such as U.S. Pat. No. 3,495,104 and 3,022,814.

Generally, such transducers vibrate at a frequency of up to 80 KHz, eg. 20 or 40 KHz, and may have an amplitude of between 0.001 and 0.005 inch, more or less. The transducer generally is carried by a suitable support (not shown) which permits the horn 17 to float rather than being rigidly mounted, thereby permitting the horn to drop down slightly as web 15 is forced over punch 13. However, even with a rigidly mounted transducer, the excursion of the end of horn 17 can be relied upon to perforate the web.

Punch 13 can have any desired shape so that its open end will punch holes of circular, rectangular or other shape, as desired.

When employing the principles described above for perforating by effecting relative movement between a horn and a long web, such as a web of photographic film or paper, rapid and continuous operation is desired. This can be secured with the apparatus shown in FIG. 2 wherein an anvil 21 is cylindrical in shape and is mounted for continuous rotation adjacent the end of horn 23, to carry a long web 25 of photographic film or paper continuously across the horn.

The cylinder 21 carries a series of equally spaced radially extending punches 27 which are successively brought into register with horn 23 as the cylinder rotates. At the same time, each punch 27 is moved radially outwardly from an initial position with its end level or flush with the surface of cylinder 21, so that as it passes across the horn it projects sufficiently to penetrate through the thickness of web 25. Upon further movement of cylinder 21, each punch 27 in turn is moved still further outwardly so as to assure complete penetration through the web; after which each punch in turn then moves radially inwardly and is retracted to its initial position.

The movement of punches 27 radially is accomplished by positioning their inner ends in contact with an eccentric stationary cam 29 which is mounted within cylinder 21. Each punch is held in retracted position by a coil spring 31 which bears at its outer end against the inner periphery of an outer flange 32 of cylinder 21, and bears at its inner end against an abutment such as a flange 33 carried by the punch. Each coil spring 31 is located in a space between outer flange 32 and an inner flange 34.

In order to assure that the core or chip of material formed by each hollow punch is always removed from the area of operation, each punch, as shown in FIG. 3, is provided with a stationary finger 37 which is mounted within cylinder 21 and projects therefrom through a longitudinal slot 39 in the punch. With this construction, when the punch 27 moves outwardly, the horn 23 causes perforation of the web to occur, and a core of the web material sometimes may remain within the punch. Subsequently, when the punch moves radially inwardly, the finger 37 expels the core from the inside of the punch. The cores (both those which separated freely from the punches, and those expelled by fingers 37) are all removed from the vicinity by suction device 43, 43', or by an air jet. Also sprockets or springs which enter the holes can be employed.

Referring to FIGS. 2 and 4, the end surface of horn 23 has about the same curvature as cylinder 21, is rounded or chamfered at its edges to prevent damage to the web, and is provided with a shallow groove 45 providing space for receiving the end of each punch 27 after it penetrates the web and projects slightly therethrough.

Now referring to FIG. 5, the cylindrical anvil 21 is secured by spokes 47 to a shaft 49 which is rotated by a motor M to bring each of the punches 27 successively into register with horn 23, which is carried by a transducer 51 of a well known type. The eccentric cam (not shown) is carried on a stationary shaft 55 supported by a stationary tripod 57 on the opposite side of cylinder 21 from motor M.

In the modification shown in FIG. 6, the ultrasonic horn 23' is cylindrical in shape and is mounted for rotation concurrently with rotation of anvil 21 by mechanism such as that shown in U.S. Pat. No. 3,201,864 to J.B. Jones et al, for "Method and Apparatus for Ultrasonic Welding".

Both horns 23 and 23' are spaced sufficiently from cylindrical anvil 21 to permit entry of the web to be perforated.

Instead of fully penetrating the web with each punch, penetration can be just short of complete (say 95 percent through the web), and the subsequent outward movement of the punches completes the penetration.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

I claim:

1. A method for punching a hole through a sheet of material, comprising

positioning said sheet with one side thereof in contact with a punch, and

applying an ultrasonically vibrating horn to the opposite side of said sheet to force said sheet onto said punch which punches a hole through said sheet.

2. A method in accordance with claim 1, wherein said sheet is of a thermoplastic material, and wherein the vibrations of said ultrasonically vibrating horn heat and soften said material.

3. A method in accordance with claim 1 wherein said punch forms said hole by shaping a removable core, and wherein said core is removed from the vicinity of said sheet.

4. In an apparatus for punching a hole through a sheet of material, the combination comprising: an anvil, a punch protrudable from said anvil and in engagement with one side of the sheet, and an ultrasonic horn for engaging the other side of the sheet and positioned adjacent said punch in axial alignment therewith and adapted to be spaced from said anvil a distance at least equal to the thickness of the sheet to be punched.

5. Apparatus in accordance with claim 4 wherein said punch is hollow.

6. Apparatus in accordance with claim 4 wherein said anvil is cylindrical in shape and is mounted for rotation past the end of said horn to carry said sheet in the form of a long narrow web continuously into and out of punching relationship with said horn, and wherein a plurality of punches are carried by said anvil and successively pass into and out of register with said horn; said apparatus also comprising mechanism for rotating said anvil.

7. Apparatus in accordance with claim 6, wherein said punches are movable back and forth radially of said cylindrical anvil, and wherein said apparatus also comprises mechanism for moving each punch outwardly to protrude from the surface of said anvil during passage of said punch in register with said anvil, and for subsequently moving said punch inwardly.

8. Apparatus in accordance with claim 6 wherein said horn has a groove therein adapted to register with and to receive the protruding portion of each punch for clearing the core formed by each punch from said web.

9. Apparatus in accordance with claim 6, also comprising means for removing the core formed by each punch from the vicinity of said web.

10. Apparatus in accordance with claim 7 wherein said mechanism for moving each punch comprises

spring means urging each punch inwardly; and

a stationary cam mounted internally of said cylindrical anvil, each of said punches having an inner end riding on the surface of said cam.

11. Apparatus in accordance with claim 7 wherein said punches are hollow, said apparatus also comprising a stationary finger within each punch acting to expel a core therefrom upon movement of said punch inwardly.

12. Apparatus in accordance with claim 7 wherein said cylindrical anvil has an annular recess extending laterally in from one side thereof, forming spaced inner and outer cylindrical flanges; wherein said punches extend through said inner and outer flanges and across said recess; and wherein said mechanism for moving each punch comprises a spring within said recess urging said punch resiliently inwardly, and a stationary cam mounted internally of said cylindrical anvil, each of said punches having an inner end riding on said cam.