US3649152A

US3649152A - Vacuum forming machine

Info

Publication number: US3649152A
Application number: US53511A
Authority: US
Inventors: John W Knack Sr
Original assignee: ACADEMIC DIMENSION SYSTEMS Inc
Current assignee: ACADEMIC DIMENSION SYSTEMS Inc
Priority date: 1970-07-09
Filing date: 1970-07-09
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

A vacuum forming machine comprises a base structure, a porous plate spacedly mounted on the base structure, and a blower mounted on the base for drawing air through the porous plate. A clamping frame for plastic sheets conforms closely to the perimetric contour of the porous plate. The frame is pivoted for movement to a heating element on the base and to the porous plate, which is then inserted through an opening in the frame. A leveling arrangement is mounted on the frame and/or the porous plate, for spacing the frame from the base and for aligning the frame with the adjacent edge of the porous plate.

Description

[45 Mar. 14, 1972 United States Patent Knack, Sr.

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Southfield, Mich.

July 9, 1970 Primary Examiner.l. Howard Flint, Jr. Attorney-Don J. Smith [22] Filed:

[21] Appl. No.:

[57] ABSTRACT A vacuum forming machine comprises a base structure, a porous plate spacedly mounted on the base structure, and a 18/19F blower mounted on the base for drawing air through the porous plate. A clamping frame for plastic sheets conforms 5 m M7 1 m 5 8 n 5 2 4 0% s 3 5 2 [52] U.S. [51] Int. [58] Field of References Cited closely to the perimetric contour of the porous plate. The frame is pivoted for movement to a heating element on the UNITED STATES PATENTS base and to the porous plate, which is then inserted through an opening in the frame. A leveling arrangement is mounted on the frame and/or the porous plate, for spacing the frame from the base and for aligning the frame with the adjacent edge of the porous plate.

7 Claims, 7 Drawing Figures FFF 999 111 III 888 1.11

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LBHR 678457 255666 999999 111111 l/l/l/ 736 45 Patented March 14, 1972 2 Sheets-Sheet l e m w w Patented March 14, 1972 3,549,152

2 Sheets-Sheet 2 H Ha mon/144% DESCRIPTION OF THE INVENTION The present invention relates to vacuum forming machines for shaping thin, substantially twodimensional plastic sheets into three-dimensional shapes or forms, and more particularly to amachine having an improved sheet holder or frame for positioning the plastic sheet properly with respect to the mold or other forming means of the machine.

Vacuum forming machines germane to the machine of the character described have been known for some time and generally include a hinged or pivoted frame in which a twodimensional, sheet of thermoplastic or formable plastic is clamped. The frame can be moved to a first position relative to a heating element of the machine wherein the plastic sheet is heated to its softening temperature The frame can then be moved to a second or forming position in the machine, relative to a vacuum pan. One or more mold structures or forming members are disposed on the vacuum pan which is sufficiently porous that air can be drawn therethrough by a blower or the like forming part of the vacuum forming machine The mold structures are provided with suitable aperture means communicating with the porous surface structure of the vacuum pan. The heated plastic sheet is drawn and shaped about the mold structures by air passing through the vacuum pan to create a partial vacuum between the plastic sheet and the vacuum pan, and other vacuum components of the machine. Similarly the sheet is drawn into the various crevices or indentations in the mold structure by the aforementioned aperture means.

In the operation of such vacuum machines, it is highly desirable to orient the plastic sheet holder or frame properly with respect to the vacuum pan such that the shaped portions of the plastic sheet are properlyoriented with respect to the balance or unformed portions of the sheet. In a typical vacuum forming machine, it is highly desirable, therefore to maintain the plane of the plastic sheet holder or frame substantially parallel to the vacuum pan. In previous machines, no adequate means has been provided for this purpose, with the inevitable result that the residual tensil strength of the heated plastic sheet is utilized in many cases to support or partially support the frame or holder with respect to the vacuum pan, usually at a raised position above the top surface of the base structure of the machine.

The pivoted frame or holder likewise is maintained slightly above the top surface of the machine to allow a proper pivotal movement thereof. As the plastic sheet and frame must be moved quickly from the heating element ofthe machine to the vacuum structure or vacuum pan thereof, little time is allowed for the operator of the machine to orientate or align manually the frame relative to the vacuum pan. In the operation of the vacuum forming machines, then, one side or other of the plastic sheet holder or frame may be permitted to sag with respect to the vacuum pan with the result that the formed areas of the sheet are misorientated relative to the perimeter or other relatively unformed areas of the plastic sheet. The three-dimensional image imparted to the sheet, moreover, is frequently distorted.

Likewise, the operator of the machine in an attempt to prevent the occurrence of the aforementioned frame sagging, may inadvertently and manually support the frame or a side thereof at some position slightly above the vacuum pan. A loss or partial loss of the partial vacuum, which would otherwise be developed between the plastic sheet and the suctional passages of the machine, then occurs and the plastic sheet may be only partially formed about the mold structure or other forming members placed on the vacuum pan.

I overcome these disadvantages by providing self-aligning means on the plastic sheet holder or frame and/or on the vacuum pan structure of the machine. The self-aligning means does not interfere with the normal operation of the vacuum forming machine, in particular its pivotal frame structure. Rather, the alignment means insures in a repetitive manner the levelling of the frame structure with the vacuum pan each time the frame structure is placed thereover, Most importantly, the self-alignment means does not interfere with the proper orientation or disposition of both the frame structure and the vacuum pan at their raised positions above the base structure of vacuum forming machine.

I accomplish these desirable results by providing in avacuum forming machine, the combination comprising a base structure for said machine, a porous plate structure spacedly mounted on said base structure, duct and blower means mounted on said base structure for drawing air through said plate structure, a clamping frame for plastic sheet material and the like, said frame conforming closely to the perimetric contour of said porous plate structure, means for mounting and pivotally moving said frame from a first position on said base structure adjacent a heating element thereof to a second position whereat said plate structure is inserted through an opening in said frame, and means secured to at least one of said frame and said plate structure for engaging and aligning said frame relative to said plate structure at said second positron.

I also desirably provide a similar vacuum forming machine wherein said engaging and aligning means include at least three bracket members secured to said plate structure and spaced thereabout for engagement by and alignment of said frame member.

I also desirably provide a similar vacuum forming machine wherein said bracket members are each secured to a bottom surface of said plate member and include an outward, downwardly stepped section positioned to engage said frame and to align upper edge portions of said frame with an upper perimeter of said plate structure.

I also desirably provide a similar vacuum forming machine wherein said engaging and aligning means include a bracket member secured to said plate structure and at least one foot member secured to said frame member and engageable with an adjacent surface of said base structure to space said frame member therefrom.

During the foregoing discussion, various objects, features and advantages of the invention have beenset forth. These and other objects, features and advantages of the invention together with structural details thereof will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention and presently preferred methods of practicing the same.

In the accompanying drawings I have shown certain presently preferred embodiments of the invention and have illustrated certain presently preferred methods of practicing the same, wherein:

FIG. 1 is an isometric view of one form of vacuum forming machine arranged in accordance with the invention and showing the frame in an intermediate position FIG. 2 is a similar view with the frame in the heating position;

FIG. 3 is a similar view with the frame in the forming position;

FIG. 4 is a partial enlarged elevational view, partially sectioned, of the apparatus as shown in FIG. 2;

FIG. 5 is a similar view of the apparatus as shown in FIG. 3;

FIG. 6 is a front elevational view of a vacuum forming machine similar to that shown in FIG. 1, but illustrating another form of the invention; and

FIG. 7 is an enlarged partial isometric view of the apparatus as shown in FIG. 6.

With reference now to FIGS. 1-5 of the drawings, a vacuum forming machine 10 shown therein comprises a base structure 12, which houses a heating element 14 in a heating well or recess 16. A screen 18 or the like, covers the top opening of the well 16 to prevent inadvertent contact with the heating element 14.

The base structure 12 also houses a blower (not shown) and suitable controls therefor, for drawing air through the vacuum pan or porous plate structure 20. The vacuum pan 20 is spaced above the vacuum forming machine 10, as better shown in FIG. 2 by means of a low profile duct 22 (FIGS. 2 and S) which adjoins the porous plate 20 adjacent its perimeter. The duct 22 together with other air passages (not shown) in the base structure 12 conducts air drawn through the vacuum pan 20 to the aforementioned blower.

A plastic sheet holder or frame 24 is pivotally mounted on the base structure 12 and is spaced above the surface thereof (FIG. 1) to permit alignment of the frame 24 with the vacuum pan 20. The frame hinges 26 in this example are of the pantographic variety to facilitate such alignment. The frame proper includes in this example a rectangular shape of angle material 28 and a complementary rectangular member 30 of a suitable complementary cross section and seatable therein. The complementary member 30 is hinged at 31 to the angle 28 for the purpose of clamping a plastic sheet 32 therebetween.

The plastic sheet holder 24 can be swung about the pivot means 26 to a position (FIGS. 2 and 4) whereat the plastic sheet 32 is closely disposed above the heating well 16. After the plastic sheet softens, the holder 24 is quickly moved to its position generally surrounding the periphery of the vacuum pan 20 as shown (FIGS. 3 and The aforementioned blower is then actuated to withdraw air through the vacuum pan or porous plate structure 20 and duct 22 (arrows 34). The sof tened plastic sheet 32 then is drawn downwardly, over, and around mold structure 36 or other shaping elements (not shown) to impart a corresponding three-dimensional shape to the plastic sheet 32.

The forming of the plastic sheet 32 is facilitated by aperture means 38 in the mold structure 36, which apply suction to specific areas between the plastic sheet 32 and the adjacent surfaces of the mold structure 36. The aperture means 38 for example can be disposed at various recesses and indentations or the like defining the design or message imparted to the mold structure 36.

When the frame 24 is positioned about the vacuum pan 20, it is highly desirable that the frame be properly aligned or levelled with the vacuum pan 20. This assures that those perimetric portions 320 (FIG. 5) of the sheet 32 will flushly engage the perimetric edges 20a of the vacuum pan 20. If the frame 24 and plastic sheet are not initially so aligned, either ridges or depressions will appear in the plastic sheet 32 at the vacuum pan edges 20a of varying elevations, depending on whether the adjacent portion of the frame is depressed below or raised upon the related edge 20a of the vacuum pan. In ad dition to the unsightly character of these ridges or depressions, the form or shape imparted to the plastic sheet 32 by the mold structure 36 will be angularly misorientated relative to the base or perimetric portions 32a of the plastic sheet. Moreover, if one or more sides of the frame 24 is inadvertently elevated above the vacuum pan 20 a substantial quantity of air can enter the resulting spaces between the adjacent sheet edge 32a and the vacuum pan edge 20a, resulting in a partial or complete loss of the partial vacuum necessary for the forming operation. In consequence, the sheet 32 when formed may exhibit a partial vacuum necessary for the forming operation. In consequence, the sheet 32 when formed may exhibit a partial or complete loss of definition.

One form of such levelling means includes, in this example, a three-point suspension for the frame 24 in the forming position thereof, as illustrated in FIGS. 1-3 and 5. Such suspension means assures proper alignment of the frame 24 and the heated plastic sheet 32, which is supported by the frame, with the vacuum pan 20. In this arrangement, such suspension means include an angle bracket 40 secured to the underside of the vacuum pan 20 at its edge adjacent the hinges 26. As evident from FIG. 5, the angle bracket 40 is shaped such that the adjacent portions of the frame 24 seat flushly therein with the adjacent perimetric edge portion 32a of the plastic sheet being disposed substantially flush with the adjacent edge portions 20a of the vacuum pan 20.

The front corners portions 42 (FIG. I) of the frame 24 are provided with feet 44, which can be in the form of grommets or the like (FIG. 5). The feet 44 are of such elevation that the adjacent portions of the frame 24 are supported at the proper elevations by contact of the feet 44 with the adjacent upper surfaces of the base structure 12 of the vacuum forming machine I0. Thus, the front corners 42 and the remainder of the frame structure 24 are likewise aligned with the vacuum pan 20 such that the perimetric edge portions 320 of the sheet 32 flushly engage the perimetric edges 200 about the entire perimeter of the vacuum pan 20. The alignment of the frame 24 in this manner is facilitated by the three-point suspension thereof, including the angle bracket 40 and the feet or grommets 44, relative to the vacuum pan 20. The hinge or pivot members 26 can be spring or gravity loaded (for example by conventional pins and vertical slots) to allow the frame 24 to be thus positioned by the three-point suspension means, particularly the adjacent angle bracket 40. With the arrangement as shown in FIGS. 1-5, it is virtually impossible for the frame 24 or any part thereof to be inadvertently positioned above or below the vacuum pan 20 such that the aforementioned ridges or recesses will appear in the sheet 32 at the vacuum pan edges 200 or such that vacuum leakage will occur at one or more of these edges.

It is contemplated that other arrangements of the aforementioned frame suspension means can be employed within the context of my invention. For example, the feet or grommets 44 of FIGS. 1-5 can be replaced by angle brackets similar to the bracket 40 (FIG. 5). As shown in FIG. 6, the plastic sheet holder or frame 24' is supported adjacent its front comer portions 42' by a pair of angle brackets 46 respectively. Each of the brackets 46 is secured in this example beneath the vacuum pan 20 for proper engagement by the frame 24. The brackets 46 can be secured (by sheet metal screws or the like) to a supporting flange 48 of the air duct 22'. The brackets 46, which are disposed adjacent the front comers of the vacuum pan 20 and remote from the hinges 26, together with the angle bracket 40 (FIG. 5) thus form a desirably three-point suspension of the frame 24 in alignment with the vacuum pan 20' as described previously. In this arrangement, the angle brackets 46 extend from the sides of the vacuum pan 20 adjacent the front corners thereof as better shown in FIG. 7. The

brackets

40, 46 in addition support the frame 24' at the proper spacing above the adjacent upper surface of the base structure 12 of the vacuum forming machine 10.

Other modifications of the suspending means are contemplated within the teachings of my present invention. For example, the

brackets

40, 46 of FIG. 5 and 6 can each be replaced by a foot or grommet similar to the foot 44 (FIGS. 1-5) at each corner of the frame 24. Likewise, the angle bracket 40 (FIG. 5) can be removed and its function replaced by a pair of angle brackets similar to the brackets 46 of FIGS. 5 and 6 disposed adjacent the rear corners of the vacuum pan 20'.

Relative to FIGS. 1-5, the angle bracket 40 can extend the entire length of the adjacent edge portion of the vacuum pan 20. It is preferred, however, that the angle bracket be considerably shorter for example nominally about the width of the angle bracket 46 of FIGS. 5 and 6, and disposed adjacent the midpoint of the adjacent edge of the vacuum pan 20, in order to afford a desirably three-point suspension of the frame or holder 24. The three-point suspension of course, facilitates the self-alignment of the frame 24 when it is moved from its heating position (FIG. 2) to its forming position (FIG. 3).

From the foregoing it will be apparent that novel and efficient forms of Vacuum Forming Machine have been described herein. While I have shown and described certain presently preferred embodiments of the invention and have illustrated presently preferred methods of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the spirit and scope of the invention.

I claim:

1. In a vacuum forming machine, the combination comprising a base structure for said machine, a porous plate structure spacedly mounted on said base structure, duct and blower means mounted on said base structure for drawing air through ncAn said plate porous structure, a clamping frame for plastic sheet material and the like, said frame conforming closely to the perimetric contour of said porous plate structure, means for mounting and pivotally moving said frame between a first position on said base structure adjacent a heating element thereof and a second position whereat said plate structure is inserted through an opening in said frame, and at least one foot member mounted on a lower surface of said frame remote from said hinge means, said foot member being engageable with an adjacent surface of said base structure for spacing said frame therefrom and for aligning said frame with the adjacent edge of said plate member.

2. The combination according to claim 1 wherein a pair of said foot members are provided, said foot members being secured to said frame adjacent corner sections thereof remote from said hinge means.

3. The combination according to claim 2 wherein a frame supporting bracket is secured to said plate structure at a location remote from said feet members for engagement and alignment of the adjacent portion of said frame.

4. In a vacuum forming machine, the combination compris ing a base structure for said machine, a porous plate structure spacedly mounted on said base structure, duct and blower means mounted on said base structure for drawing air through said plate porous structure, a clamping frame for plastic sheet material and the like, said frame conforming closely to the perimetric contour of said porous plate structure, means for mounting and pivotally moving said frame from a first position on said base structure adjacent a heating element thereof to a second position whereat said plate structure is inserted through an opening in said frame, and means secured to at least one of said frame and said plate structure for engaging and aligning said frame relative to said plate structure at said second position.

5. The combination according to claim 4 wherein said engaging and aligning means include at least three bracket members secured to said plate structure and spaced thereabout for engagement by and alignment of said frame member.

6. The combination according to claim 5 wherein said bracket members are each secured to a bottom surface of said plate member and include an outward, downwardly stepped section positioned to engage said frame and to align upper edge portions of said frame with an upper perimeter of said plate structure.

7. The combination according to claim 4 wherein said engaging and aligning means include a bracket member secured to said plate structure and at least one foot member secured to said frame member and engageable with an adjacent surface of said base structure to space said frame member therefrom.

Claims

1. In a vacuum forming machine, the combination comprising a base structure for said machine, a porous plate structure spacedly mounted on said base structure, duct and blower means mounted on said base structure for drawing air through said plate porous structure, a clamping frame for plastic sheet material and the like, said frame conforming closely to the perimetric contour of said porous plate structure, means for mounting and pivotally moving said frame between a first position on said base structure adjacent a heating element thereof and a second position whereat said plate structure is inserted through an opening in said frame, and at least one foot member mounted on a lower surface of said frame remote from said hinge means, said foot member being engageable with an adjacent surface of said base structure for spacing said frame therefrom and for aligning said frame with the adjacent edge of said plate member.

4. In a vacuum forming machine, the combination comprising a base structure for said machine, a porous plate structure spacedly mounted on said base structure, duct and blower means mounted on said base structure for drawing air through said plate porous structure, a clamping frame for plastic sheet material and the like, said frame conforming closely to the perimetric contour of said porous plate structure, means for mounting and pivotally moving said frame from a first position on said base structure adjacent a heating element thereof to a second position whereat said plate structure is inserted through an opening in said frame, and means secured to at least one of said frame and said plate structure for engaging and aligning said frame relative to said plate structure at said second posItion.