Platen For Vacuum Holding Of Sheet Material

Abstract

A vacuum holding platen is constructed as a lamination comprised of a thin center aluminum sheet to each side of which is adhered a Masonite sheet, the outward face of which has been routed to provide desired channel patterns through which air may be exhausted by connection to ducts leading from an air exhausting pump. The routed Masonite on the side of the platen upon which the sheet material is to be held, is adhesively covered with a perforated sheet. The other Masonite sheet is similarly covered with an unperforated thin sheet of aluminum. All of the unperforated sheets are appropriately orificed to enable the channels to be selectively connected, depending upon the size of the film or other sheet material to be held by the platen, through a valve block, movably disposed on the back of the platen, to the air exhausting pump. The orificed metal sheets may be of aluminum and punched to provide perforations or passage orifices. The Masonite sheets are routed and all contacting surfaces of the sheets are coated with epoxy and compressed between granite blocks which are hydraulically separable to permit insertion in between them of the sheets to be compressed and removal therefrom of the compressed platen.

Description

RELATED APPLICATIONS

While none of my prior applications are directed to the subject matter described and claimed herein, my applications Ser. Nos. 44,242 and 121,780 filed Jan. 8, 1970 and Mar. 8, 1971 respectively disclose and claim camera systems in which the subject matter herein disclosed and claims has particular utility and application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to vacuum means for holding film or other sheets of flexible material fixedly against a platen or other flat surface, and to a method of preparing such means. The vacuum means of the present invention has particular application to graphic cameras for commercial and industrial uses, such as are disclosed and claimed in my said prior applications.

2. Description of the Prior Art

Within recent decades there have been designed and placed in industrial and commercial uses a number of different types of large cameras. These cameras are adapted to photograph in detail large flat areas such as maps, vellums, drawings, prints, photographs, etc.

Such cameras usually include some type of longitudinally extending base which carries a track on which is movably mounted both a frame to hold the item to be photographed and the lens-shutter end of a large bellows type camera. The frame ordinarily will be disposed near one end of the track and at the opposite end of the latter is a fixedly secured, framing means to receive the film holding platen. There is attached to this framing means the large end of the camera bellows.

In some prior art cameras the film, which must be held perfectly flat, has been held in place by a grooved or channeled platen which is covered by a perforated metal sheet. The grooves or channels are connected to a pump. This pump exhausts the air from the channels and thereby creates a vacuum on the face of the perforated sheet which covers the channels. Film placed on such perforated metal sheets is closely drawn thereto. For convenience, such platens will be herein referred to as "vacuum platens".

Heretofore, vacuum platens have been extremely costly to have fabricated and have been quite heavy (e.g. in the order of 75 lbs. for a 2 feet .times. 2 feet platen), with the result that the framing to receive such vacuum platens and the means to swing and articulate them into their positions have had to be most sturdily and, hence expensively, constructed. This is because such platens have been made by either machining a basic plate of a metal, such as steel or aluminum, of perhaps a one-half inch thickness, or making it of cast iron or aluminum, to provide the necessary channels; and then covering the channeled side of such plate with the perforated metal sheet.

The minimum one-half inch thickness is necessary to insure complete flatness and to prevent warping of the platen.

Prior to the present invention, I attempted to decrease the cost of fabricating the vacuum platen by not having the channels machined or cast into it, but instead, by adhering to the steel or aluminum plate a sheet of Masonite and then routing the necessary channels into the Masonite. Lastly, the channeled Masonite face would be covered with a sheet perforated metal, such as aluminum. This decreased the cost of the platen to the extent that it is cheaper to route Masonite than to machine channels in steel or to have them cast into a cast iron plate. It has not, however, solved the weight problem, nor has it cut the cost inherent in providing the thick aluminum iron or steel plate. All platens heretofore made, moreover, because of their weight and manner of holding for swinging in and out of the fixed frame, have had a tendency to twist slightly out of shape.

SUMMARY OF THE INVENTION

The present invention comprises a platen which is substantially lighter than prior art platens and a method of making the same.

Instead of fabricating the platen of a thick plate of steel, cast iron, or aluminum, I construct it as a laminate consisting of a relatively thin aluminum center sheet to each side of which is secured by epoxy or other suitable adhesive a Masonite sheet. After compressing the laminate, both Masonite sheets are routed to provide the desired channel pattern, and the exposed faces of these Masonite sheets are adhesively covered, one by the perforated metal sheet, and the other, by another sheet of aluminum. The entire laminate is preferably compressed between two hydraulically separable granite or marble blocks. Such blocks are chosen for both their natural weight for compression purposes (e.g. about 3 p.s.i.) as well as because they will not warp once they are cut to plane surfaces.

Although only one routed Masonite sheet is necessary to provide the air passages beneath the perforated sheet, I have found that by providing a substantially matingly routed sheet on the opposite side of the aluminum center sheet and connecting the routed channels to the same air exhaust ducts as are connected to the channels of the other Masonite sheet, with cross-over orifices, the entire laminate is better balanced to prevent warping or such stress as might otherwise tend to bend or twist the laminated platen.

A platen prepared according to the present invention will be found to be only about one-third as heavy as a prior art platen of similar size, and is every bit as effective. Moreover, the cost of manufacturing the platen of the present invention is less than half that of fabricating a heavy steel or cast iron platen. It is even substantially less than the cost of manufacturing my prior platens consisting of the heavy aluminum plate, routed Masonite and perforated sheet.

In addition, because of the substantial decrease in the weight of the platen made according to the present invention, substantial savings may be effected in related structure in the camera which structure serves to support the platen and enable it, to be swung into both loading and film exposing positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a typical camera set-up in which a platen may be employed, with the platen in film exposing position.

FIG. 2 is a partial perspective view similar to FIG. 1, showing the platen moved into loading position.

FIG. 3 is an exploded view of a platen of the present invention.

FIG. 4 is a section taken on the line 4--4 of FIG. 3, but in unexploded condition.

FIG. 5 is an elevational view of compressing apparatus desirably employed in preparing a platen according to the present invention.

FIG. 6 is a plan view of a routed Masonite sheet.

FIG. 7 is a rear view of the platen to which a slidable valve arrangement is attached.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The vacuum platen 10 of the present invention may be seen in FIGS. 1 and 2 to have a particular use in the industrial camera there portrayed to hold film 12 in position for exposure by the camera 14. Since an industrial camera of the type illustrated in FIGS. 1 and 2 is fully described in my co-pending applications, Nos. 44,243 and 121,780, the structure and components of such camera itself will not be again described herein.

The vacuum platen 10, however, is mounted in such a manner that it can be disposed either in the horizontal position for loading shown in FIG. 2 or in the vertical position at the rear of the bellows 16 within the frame 18 for picture taking exposure. In both positions air exhausting means, such as a pump (not shown) is connected by a main hose 19 through a slide valve 20 and short hose 21 (FIG. 7) to one or more of a series of orifices 22 in the back side 10a of the platen 10, which orifices extend from the back side 10a of the platen through a portion of the laminated platen 10 to provide passages 24 to a series of rectangular channels 26, 28, routed in two Masonite sheets 30, 32 respectively, comprising portions of the laminated platen 10, the construction of which is hereinafter to be explained.

This platen 10 is constructed of a center aluminum sheet 34 of approximately one-sixteenth inch in thickness to each side of which is bonded by epoxy 36 a three-sixteenths inch Masonite sheet 30, 32, to constitute an initial laminate 42. This initial laminate 42 is placed between a pair of hydraulically separable marble blocks 44, 46, each cut with horizontally plane faces and pressed together at a pressure of approximately 3 p.s.i. for a period of at least 15 minutes.

The initial laminate 42 is then removed from the block press 48 and each Masonite sheet 30, 32 is routed into its channel pattern 50 and the laminate 42 is drilled to provide the series of orifices 22. My preferred channel pattern 50 is shown in FIG. 6, and includes two cross-over connecting orifices 22a. While other channel patterns may be provided, I prefer that shown in FIG. 6 where the platen is intended to hold rectangularly shaped films in position within the camera.

After the Masonite sheets 30, 32 of the initial laminate 42 have been routed and the orifices 22 have been drilled, a backing sheet 52 of one-thirty-second inch aluminum is drilled to provide orifices 22 to register with those in the initial laminate and this sheet is coated with epoxy 54 and placed in contact with the Masonite sheet 30. A perforated sheet of aluminum 38 of about one-sixteenth inch in thickness is similarly coated with epoxy 58 and placed in contact with the routed side of the other Masonite sheet 32, thereby to comprise the complete laminated platen 10. This complete laminate 10 is also compressed in the marble block 48 at the same 3 p.s.i. pressure for the same time as the initial laminate 42.

As thus formed and constructed, the platen 10 will be found to be considerably lighter in weight than prior art platens, and is substantially less costly to fabricate. By providing channels, and hence, air passages, in the Masonite sheets 30, 32 on both sides of the center sheet 34, stresses are minimized which might otherwise tend to cause twisting or warping of the laminate 10.

Claims

I claim:

1. An improved vacuum platen for holding securely to a first side thereof a sheet of film or other thin material in a system which includes an air exhaust pump, conduit means extending from said pump to the second side of said platen, said platen comprising:

a. a thin center sheet of metal;

b. a pair of Masonite sheets, one being adhered to each side of said center sheet, each of said Masonite sheets being routed on its unadhered face to provide a predetermined series of channels, some of which channels may not be routed to connect with any of the other channels, and some of the channels of one sheet being connected through orifices in the center sheet of metal to channels in the other Masonite sheet;

c. a perforated thin sheet of metal adhered to the routed face of one Masonite sheet to comprise the first face of the platen; and

d. a thin unperforated sheet of metal adhered to the routed face of the other Masonite to comprise the second and back face of the platen;

All of said unperforated sheets being orificed to provide connective passages to the channels in said Masonite sheets from the second face of said platen from said conduit means.

2. An improved vacuum platen for holding securely to a first side thereof a sheet of film or other thin material in a system which includes an air exhaust pump, conduit means extending from said pump to the second side of said platen, said platen comprising:

a. a thin center sheet of metal;

b. a pair of Masonite sheets, one being adhered to each side of said center sheet, each of said Masonite sheets being routed on its unadhered face to provide a predetermined series of channels, some of which channels may not be routed to connect with any of the other channels;

c. a perforated thin sheet of metal adhered to the routed face of one Masonite sheet to comprise the first face of the platen; and

d. a thin unperforated sheet of metal adhered to the routed face of the other Masonite sheet to comprise the second and back face of the platen;

All of said unperforated sheets being orificed to provide connective passages to the channels in said Masonite sheets from the second face of said platen from said conduit means.

3. An improved vacuum platen for holding securely to a first side thereof a sheet of film or other thin material in a system which includes an air exhaust pump, conduit means extending from said pump, valve means on the second side of said platen for selectively connecting said conduit means to one or more orifices in said platen, said platen comprising:

a. a thin center sheet of metal;

b. a pair of Masonite sheets, one being adhered to each side of said center sheet, each of said Masonite sheets being routed on its unadhered face to provide a predetermined series of channels, some of which channels may not be routed to connect with any of the other channels, and some of the channels of one sheet being connected through orifices in the center sheet of metal to channels in the other Masonite sheet;

c. a perforated thin sheet of metal adhered to the routed face of one Masonite sheet to comprise the first face of the platen; and

d. a thin unperforated sheet of metal adhered to the routed face of the other Masonite sheet to comprise the second and back face of the platen;

All of said unperforated sheets being orificed to provide connective passages to selected channels in said Masonite sheets from the second face of said platen through said valve means.

4. An improved vacuum platen for holding securely to a first side thereof a sheet of film or other thin material in a system which includes an air exhaust pump, conduit means extending from said pump, valve means on the second side of said platen for selectively connecting said conduit means to one or more orifices in said platen, said platen comprising:

a. a thin center sheet of metal;

b. a pair of Masonite sheets, one being adhered to each side of said center sheet, each of said Masonite sheets being routed on its unadhered face to provide a predetermined series of channels, some of which may not be routed to connect with any of the other channels;

c. a perforated thin sheet of metal adhered to the routed face of one Masonite sheet to comprise the first face of the platen; and

d. a thin unperforated sheet of metal adhered to the routed face of the other Masonite sheet to comprise the second and back face of the platen;

All of said unperforated sheets being orificed to provide connective passages to selected channels in said Masonite sheets from the second face of said platen through said valve means.

5. The method of fabricating a vacuum holding platen which comprises:

a. first making a three-sheet laminate by taking a thin sheet of aluminum and adhering to each side of said sheet by epoxy or other adhesive having similar properties, a sheet of Masonite and compressing said laminate between horizontal plane faces of two blocks of granite at approximately 3 p.s.i.;

b. routing the exposed side of each of the Masonite sheets of said laminate to provide a series of channels in a similar preselected pattern;

c. providing holes through the said laminate to afford connections to said channels from each side of said laminate;

d. coating the routed faces of said Masonite sheets with similar adhesive; and

i. applying to one of said two routed faces a thin perforated sheet of metal such as aluminum;

ii. applying to the other of said two faces an unperforated sheet of metal having a hole pattern at least to some extent similar to that of the said three sheet laminate and placing it with its holes in registry with those of the last said laminate; and

iii. compressing in like manner the resulting five-sheet laminate to constitute the desired platen.

6. The method of fabricating a vacuum holding platen which comprises:

a. first making a three-sheet laminate by taking a thin sheet of aluminum and adhering to each side a sheet of Masonite and compressing evenly the thus-adhered sheets to form a three-sheet laminate;

b. routing the exposed side of each of the masonite sheets of said laminate to provide a series of channels in a similar preselected pattern;

c. providing holes through the said laminate to afford connections to said channels from each side of said laminate;

d. coating the routed faces of said Masonite sheets with adhesive; and

i. applying to one of said two routed faces a thin perforated sheet of metal such as aluminum;

ii. applying to the other of said two routed faces an unperforated sheet of metal having a similar hole pattern at least to some extent similar to that of the three-sheet laminate and placing it with its holes in registry with those of the laminate; and

iii. compressing in like manner the resulting five-sheet laminate to constitute the desired platen.