US2856695A - Checking fixture or model - Google Patents

Description

Oct. 21, 1958 E. J. HOCHRElTER 2,356,695

I CHECKING FIXTURE 0R MODEL Filed Jan. 28, 1952 5 Sheets-Sheet 1 INVENTOR. Edward lHdchreifiet BY M a, M

4 TTORNE Y Oct. 21, 1958 E. J. HOCHREITER 2,856,695

CHECKING FIXTURE 0R MODEL Filed Jan. 28, 1952 3 Sheets-Sheet 2,

' iiiiimmm lllllllllillllllfllllllllllllllllllll mum INVENTOR- Edward J. Hochreiier A TTORNE) Oct. 21, 1958 E. J. HOCHREITER 2,856,695

' CHECKING FIXTURE OR MODEL Filed Jan. 28, 1952 3 Sheets-Sheet 3 I N V EN TOR. Edward J. Hochrteier BY M G. M

ATTORNEY 2,856,695 Patented Oct. 21, 1958 lice CHECKING FIXTURE R MODEL Edward J. Hochreiter, Bala-Cynwyd, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Application January 28, 1952, Serial No. 268,622 2 Claims. (Cl. 33-174) The invention relates to checking fixtures and models having their working surfaces formed on resin or plastic.

The over-all object of the invention is the general improvement of such checking fixtures and models and of the procedure in making them.

More specifically, an object of the invention is the provision of a model which can replace the hitherto used sectional models laboriously made of expensive wood such as mahogany.

Another specific object of the invention is checking fixtures or models having greater accuracy than heretofore obtainable and allowing the production of any desired number of accurately identical replicas.

A further specific object of the invention is the replacement of the now widely-used, expensive checking fixtures, using low-melting-point alloys.

These and other objects and advantages are obtained by a checking fixture or model compositely formed of metal tubing, sheet metal walls, flexible web material such as reticulated particularly expanded metal, and cast-on plastic providing the Working surface.

The features of the invention and the details and advantages thereof will be more clearly and fully understood from the embodiments described in the following and illustrated in the attached drawing.

In the drawing:

Fig. 1 is an outside perspective of the completed model or fixture for the outer surface of an automobile door;

Fig. 2 is an inside perspective of the supporting struc ture of the fixture or model shown in Fig. 1, prior to the application of the plastic;

Fig. 3 is, on a larger scale, a fragmentary outside perspective of the supporting structure depicting the region at and adjacent the lower forward corner of the Window opening of Fig. 1, certain portions being shown in section;

Figs. 4 and 5 are fragmentary sections along lines 44 and 5-5, respectively, of Fig. 3, showing the outlines of the plastic to be cast-on in dot-and-dash lines;

Figs. 6 and 7 are fragmentary sections along lines 6-6 and 7-7, respectively, of Fig. 1, on a larger scale;

Fig. 8 is a fragmentary view of a modification in regard to the supporting sheet metal and expanded metal;

Fig. 9 is a section taken aproximately along line 9-3 of Fig. 8;

Fig. 10 is a section along line 1010 of Fig. 8 and corresponding to Fig. 6;

Fig. 11 is a perspective of a checking fixture for the deck lid of an automobile; and

Fig. 12 is, on a larger scale, a fragmentary section along line 1212 of Fig. 11.

The making of the models or fixtures shown in the drawings is preceded by certain preparatory, not illustrated, devices and steps such as, for instance: First, a temporary model is made which presents a replica of the working surface of the desired final model or fixture.

This temporary model may be formed of plaster of Paris, modeling clay, soft wood such as balsa, or any other inexpensive and easily workable material. From the temporary model a negative replica is obtained by casting on it plaster of Paris or other relatively inexpensive expendable material. This replica presents a mold for casting on it the plastic of the final model or fixture.

The model or fixture illustrated in Figs. 1 to 7 has a base frame 15 corresponding approximately to a vertical projection of the perimeter of the model to be obtained and is formed by welding together or bending tubular sections 16. These sections 16 are braced against each other by additional tubular sections 17. The members 16 and 17 present a plane supporting surface. Base frame 15 is connected with additional tubular members 18 and with peripheral sheet metal members 19. The outer margins of members 19 and of some of the tubes is follow approximately the working surface to be finally given to the model.

The sheet members 19 are provided with closely spaced holes 20 all along their outer margin. Connected with the sheet metal members 19 near their outer margins and to the outer frame members 18 is reticulated, preferably expanded, metal 21. In the peripheral regions there is a second web 22 of this metal. Web 21 is secured to the outer margin of the sheet metal members 19 and tubes 18, and web 22 is secured to Web 21 and sheet metal members 19 on the inside at a distance from the outer margins. Webs 21 and 22 are secured to frame members 18, sheet metal members 19 and to one another by welding, preferably by electric spot-welding supplemented, if necessary, by are or gas Welding.

Along the inner margin of an opening in the model, web 21 is inwardly looped at 23 (Fig. 5), and looped webs 24 are secured to the margins and to an inwardly spaced location of members 19 (Fig. 4). p

The reticulated webs 21, 22 are given an impervious surface by applying to them a layer 25 of a plastic composition of relatively high consistency, that is: a consistency that will prevent the plastic from dropping ofl or flowing away after it has been ladled on. This initial layer 25 of plastic or of other sealing means is allowed to harden and to make a firm band before proceeding with the next step in the manufacture of the model.

Structure 15 to 25 is now suspended over the negative replica, not shown but described hereinbefore, marginal seals between the replica and the supporting structure are provided, and inlets and risers for the plastic, to be poured, are installed. The replica has previously been provided with a separator, that is: a coating which will prevent binding of the plastic and will allow easy separation of the plastic from the replica. Plastic 26 is then poured into the space between the supporting structure and the replica, is allowed to harden, and is, if recommendable, thermally cured.

The model now is substantially completed after separation from the replica. Its surface may be polished and any flaws may be repaired. Sometimes reinforcing strips 27 of brass are attached such as by screws 28 at this stage, though the strips may have been previously supported in the replica and cast into the model. Other pre-fabricated inserts or supplements may be connected with the device at locations where great wear is expected, where particularly high strength is required, or where the cross-section does not permit a sufficiently thick layer of plastic and interior reinforcement thereof. Aside from brass or other metal, inserts or supplements made of plastic having glass fibers embedded therein were found satisfactory. t i

At the margin the plastic is thicker than in the midregion of the model and projects outwardly beyond the sheet metal members 19. The plastic is firmly anchored to the sheet metal members by extending through the holes 20 in the latter and by having embedded therein the expanded metal 21 to 24 If great accuracy is required in regard to the location of the supporting surface of the model relative to its outer working surface, gauge blocks 29 may be attached to the base frame, and these blocks may then be machined in situ in a planer or shaper. For assuring still greater accuracy, the gauge blocks 29 are machined to less thickness required for the supporting surface, are provided with tapped holes, and gauges or shim plates 30 are secured to them by recessed screws 31. The removable plates 30 can either be selected to give the exact location of the supporting surface upon their attachment to the blocks 29 or they may be used in conjunction with thin shims (not shown) inserted between them and the blocks 29.

Often it may be advantageous to cast an uninterrupted layer 32 (Figs. 4 and of plastic across the region of the window opening and to cut layer 32 out later on.

Reference lines such as the plane of a window or of a plane spaced a certain distance from a base plane (longitudinal, vertical center plane of a vehicle) may be marked on the sheet metal members 19 by lines and/ or by cut-outs. These reference lines are not illustrated; they are customary on wooden models.

The completed model section shown in Fig. l is in its general configuration very similar to the hithertoemployed wooden model sections, and it may therefore be combined with other sections to represent the surface of a larger model structure such as the surface of an automobile body.

Figs. 8 to illustrate a modified, simpler design of a model or fixture along its margins. Secured to the sheet metal member 33 is a web 34 of expanded metal. Sheet 33 and web 34 correspond to members 19 and web 21 as shown in Figs. 1 to 7. The outer margin of member 33 is reinforced by a flange 35. Holes and supplementary webs 22 of the first embodiment are dispensed with and their place and their functions are taken by an embossed or corrugated reticulated web as secured, e. g. welded, to the metal sheet 33 adjoining the margin of web 34. The depth of the corrugations of web 36 may be in the order of inch.

Similar to the first embodiment, a plastic layer 37 is ladled on web 34, and the form-giving final layer 38 is cast on after the hardening of layer 37. The layer 35 is bonded to the sheet metal 33 by embedding in it web 36.

This design is simpler and lighter than the first design, as it does not require the punching of a great number of holes and as it does not require additional corner Webs to be sealed laboriously from the inside of the model.

Figs. 11 and 12 illustrate an application of the same hereinbefore described features to the formation of a checking fixture.

Base frame 39 projects beyond sheet metal members 40, which in turn carry the plastic 41, 42. Large openings 43 are for weight reduction and saving of material.

Removable members 44 are held by screws 45. The exact relative location of members 44 is insured by mating recesses and projections 46 on layer 42 and members 44. The members 44 are obtained by casting of plastic against the finished main portion of the fixture supported in the mold. This is similar to the technique used in making checking fixtures of low-melting-point alloy as disclosed in Patent 2,459,084 (McGary et al.), Method of and Means for Making Dies, issued Jan. 11, 1949, to applicant as co-inventor.

Here are a few data regarding the materials and dimensions found satisfactory in building models and fixtures of the illustrated and described types. Tubes for the base frame: 1.5 X 1.5 inch with .065 inch wall thickness. Other tubes: 1 x 1 inch with .049 inch wall thickness. Sheet metal members: .060 inch gauge. Expanded metal: .050 inch gauge with /2 inch diamondshaped openings. Thickness of sealing layer: About /8 inch. Thickness of total plastic or resin layer in regions of large surfaces: About 1 inch but preferably down to inch or less.

A number of different plastics or resins as now available on the market were found applicable. Good results were achieved with a material available under the designation ARC-120. The resin should preferably not, or as little as possible, change its dimensions during hardening or curing, and it should keep its dimensions and shape practically indefinitely after the completion of the device.

It was found satisfactory to make for large devices an allowance at the perimeter of .030 inch for shrinkage and to work the perimeter of the cast and cured device slightly down to the exact dimensions.

In general it was found appropriate to fit the plastic device into its form with the help of a sticky paint in a similar manner as it is customary to fit mating dies into each other.

Devices of the type illustrated and described hereinbefore were found to be much lighter and cheaper than comparable fixtures hitherto made with the use of lowmelting-point alloys. The price comparison takes into account the fact that a large proportion of the low-melting-point alloy can be re-used when the device has served its purpose, whereas the resin of the new fixtures cannot be re-used. The new models also compare favorably in weight and cost with the wooden models which they replace, and they have the great advantage of not being subject to changes in shape and dimensions as are the wooden models.

Evidently any desired number of models or checking fixtures may be made with practically identical working surfaces. This is not true for wood models, where the shape of the working surface depends largely on the skill and the accuracy of the craftsman who forms it and who, in spite of any amount of diligence, is not able to impart to two models exactly identical surfaces when those surfaces have intricate compound curvatures, as is nowadays the case for the models of automobile bodies.

The invention is obviously not limited to the specific illustrated and described embodiments and the details thereof but is susceptible to modifications and to adaptations for specific requirements and shapes. In short, though the illustrated and described embodiments are characteristic of outstanding features of the invention, many modifications will occur to those skilled in the art so as to adapt the invention to the large variety of forms of stampings as nowadays are produced and to many specific problems that may be encountered.

What is claimed is:

1. Device presenting a replica of the surface of an article and being composed of a metal supporting structure and a layer of artificial resin or plastic; said supporting structure comprising a framework of metal tubing rigidly connected with peripheral sheets of metal, and of a reticulated web extending across open space between said sheets and being secured to them, the web providing a shape approximating the replica surface of the completed device; anchoring means along the meeting margins of said web and sheets; said plastic layer being cast on and held by said web and said anchoring means and providing the exact desired surface.

2. Device according to claim 1, having said anchoring means formed by the provision of holes in said sheets.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Griffith June 5, 1934 Andes Oct. 8, 1935 Cross May 10, 1938 Groehn Mar. 6, 1945 Dasher May 13, 1947 Stewart Jan. 13, 1948 6 Singleton Aug. 24, 1948 McGary Jan. 11, 1949 Renaud Jan. 25, 1949 Landgraf June 23, 1953 Mills Feb. 16, 1954 Kish June 29, 1954 Kish Nov. 23, 1954

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