US2647400A - Load application unit - Google Patents

Description

Aug. 4, 1953 Filed Oct. 15, 1951 J. W. GAINES LOAD APPLICATION UNIT 2 Sheets-Sheet l INVENTOR.

JAMES W. GAINES ATTORNEY Aug. 4, 1953 J. w. GAINES 2,647,400

LOAD APPLICATION UNIT Filed oct. 5, 1951 2 Sheets-Sheet 2 IN V EN TOR.

JAMES W. GAI NES BY [mm ATTORNEY Patented Aug. 4, 1953 UNITE-D PATENT OFFICE LOAD APPLICATION UNIT James W. Los Angeles, -Galif., assignor :to

orth American Aviation, Inc.

Application October 15, 1951, .SerialNu. 251,405

12Claims. (01. 73-88) 1 This invention applies to a load application unit and more particularly to a unit adapted to apply loads to curved'or straight test panels. Present day arrangements for'applying loads to test a specimen normally involve that are glued to the specimen. Each unit is separate and is hacked up by a rigid metal plate. These: units are normally attached to a test specimen by placing a vacuum *blanket over the uni-ts so that the units may be "held against the specimen by the force of a vacuum until the glue has set. The rigid metal plates must he shaped as nearly as possible to the contour of the test specimen which is a time consuming operation, and it is nearly impossible to form the plates to the exact contour required. As a result, there is a tendency to deform the test specimen when the plates are attached by means of the vacuum blanket. In addition, it takes a good deal of time to attach the plates as well as to form them and it is very di-ilicult to remove the glue when the tests are completed. Solvents for the glue will injure a windshield canopy test specimen, and scraping of the glue will also result in damage to the specimen due to scratching. Arrangements utilizing vacuum cups as the load application units have been proposed, but these have proved unsatisfactory because they are difiicult to seal around the edges and will not produce a uniform vacuum load throughout the entire area where the unit is attached. As a result these load units are poorly attached to the test specimen and will not withstand high loads. Further, these will tend to distort the "test specimen due to the non-uniform vacuum produced.

Accordingly, it is an object of this invention to provide a load application unit that may be easily and securely applied to a test specimen and maybe quickly removed.

' Another object of this invention is to provide a load application unit thatdoesnotrequi-regluing to the test specimen. 7

A further object of this invention is to -pro 'vide a load application unit that does not require the use of substances injurious to the test specimen.

.An additional object of this invention is to provide a load application unit that will withstand heavy loads and will not cause distortion .ofthe test specimen.

stillanother-object of this invention is topro wide a dead application unit having a plurality of .load assuming members. .These andiotherohiects of this invention will become apparent from theiollovl-mg detailed sieill) 2 scription taken in connection with the accounpanying drawings in which Fig. 1 is a perspective sectional view-"of the "load application uni-t applied to a test specimen,

Fig. 2 is a fragmentary inverted perspective view illustrating an alternative construction of the non-porous sheet.

Fig. 3 is a plan view illustrating the use of second sheet of non-porous material,

Fig. sis aview along line 4-4 ot-Fig. 3,

Fig. 5 is an elevation of a modification of the load application unit,

Fig. .6 is a plan view of portions of the bottom of a unit of the type shown in Fig. 5, l

"Fig. "7 is a sectional view of a unit of the type of Fig. 5 associated with porous sheets,

Fig. 8 is a sectional view of a pad and-sheet formed from a single piece of material,

Fig. 9 is a sectional view of a pad and sheet formed from a single piece of material wherein the bottom portion is provided with grooves, and

"10 is a one-piece-unit of the type of Fig. associated with porous sheets.

Referring to the drawings, in a preferred em- "bodiment of this invention, load application unit I is made of a sheet of non-porous flexible matori-a1"? to one side of which is applied a thicker pad 3 which is also of a flexible material such as sponge rubber. The pad may be attached to the sheet "by bonding, gluing or other satisfactory methods and should be positioned in the central portion of the sheet so that the periphery 4 of the sheet extends beyond the pad on all sides. on the other side of the pad a plurality of fiat, rigid plates '5 are attached by gluing or other suitable methods. Theseplates should be spaced from each other as illustrated in order to allow 'flexure of the unit. It is normally desirable to put a ll-shaped groove 6 in the pad between the plates to facilitate flexure of the unit. Attached by screwthreads. welding or other suitable means to each plate 5 is a fitting 1 adapted to receive .a ,load producing member such as wire cable 8. The unit may be constructed as large or as small .as desired and as many plates 5 may be attached to the pad as necessitated ,by the size of the unit -;and the number of load producing membersfa ,to heattached. Means arealso provided for pro- .ducing avacuum-beneath sheet 2 which may be accomplished by .nroyiding a length of tubing as projecting .ithrough one of the plates. the red and the sheet. This tubing opens to {the bottom oisheet I and .is aria-medic receive a vacuum hose it on its other end. The vacuum. hose is plate member 5 may receive a load producing member if desired. Detachment of the unit from the test specimen is accomplished by merely releasing the vacuum beneath sheet 2which allows easy removal of the unit from the test specimen. As a vacuum is produced beneath sheet 2 the I It is normally preferred to interposea vacuum sealing material l2 beneath the projecting periphery 4 of sheet 2 in order to assure a'complete vacuum beneath the sheet. This material may be zinc chromate, ordinary caulking compound or other suitable material. When the unit is removed frcm the testspecimen this sealing material will require no scraping and can be easily washed off with a solvent that will not injure a transparentwindshield canopy.

It; is also generally desirable to provide a sheet of porous material l3 between sheet 2 and test specimen ll. Sheet l3 should be of lesser width and length dimensions than sheet 2approximately the dimensions of pad 3-and positioned in the center so that the periphery ll of sheet 2 projects beyond porous sheet 13 in all directions. This porous sheet may be of any suitable material such as'wire-screenor a loosely woven fabric such as burlap. The function of porous sheet I3 is toprevent sheet 2 from'sealing itself off at. a location other than the periphery of this sheet, thus assuring that there is a uniform vacuum throughout the area beneath pad3. V

Another method of assuring that the vacuum is uniform beneath sheet l .is to provide the bottom surface of the unit with grooves 14 or other irregularities in the area beneath the pad, portion in the manner illustrated in Fig. 2 in which the load application unit is inverted from the position shown in Fig. 1. Withthis modification it is unnecessary t use a porous sheet l3 because the grooves will' permit complete exhaustion of the air from beneath the sheet and prevent sealing at positions other than the periphery of sheet 2.

In certain instances it may be desirable to provide a second sheet of non-porous material l5 as illustrated in Figs. 3 and 4.; This sheet should be of a highly flexible material and may be a thin sheet of a plastic material such as a vinyl derivative. Sheet Iii-should have anaperture H5 in its central portion'dimensioned so as to admit pad 3 while allowing" the periphery of the aperture to engagethe periphery of sheet 2. Additional sealing material-'12 should be provided 4 between sheet 15 and periphery 4 of sheet 2, and a ring of the sealing material may be provided between sheet 15 and test specimen H well beyond the periphery of sheet 2. The use of this additional non-porous sheet assures a complete vacuum beneath the load application unit and will assist in rescaling around the periphery of the unit should the seal be broken.

A 'modificationof this invention is-illustrated in Fig. 5-in which the bottom surface of sheet I is provided with depending tabs [1. When a unit provided with these tabs is associated with a testspecimen, tabs [1, sheet 2, and the test specimen cooperate to provide a plurality of separate chambers I8; A suitable vacuum aperture such as tubing 9 is provided to each of these chambers.

.When the unit is applied, vacuum sealing compound l2 may be disposed beneath each of the tabs to. assure that the chambers are separately sealed from each other. To assure a complete and; uniform vacuum beneath sheet 2, each chamber l8 may beprovided with a sheet of porous material i3, as illustrated in Fig. '7, or the surface of sheet 2 may be provided with grooves M or other indentations as shown in Fig.6 or of the type illustrated in Fig. 2. v

When such a modified test unit is applied to a test specimen a separate vacuum line 10 may be attached to each of chambers 18 or these vacuum lines maybe manifolded. together by manifold 20, as shown in- Fig. 5, if desired. The vacuum lines and manifold are connected with suitable vacuum pumps l9. Thus, for example, if failure of the test specimen is anticipated at a certain area a separate vacuum line may be applied to the chambers in that area while the other chambers may be manifolded together. Thus failure of the test specimen at the critical area will not effect adherence of the unitin other positions.

It is possible as a further modification to construct sheet 2 and pad 3 out of a single piece of material in any of the above described embodiments. Fig. 8 illustrates a pad and sheet of the type of Fig. 1 formed from one piece of material 2|. In Fig. 9 is shown a one-piece pad and sheet unit 21 having grooves to assure complete exhaustion of air from beneath the unit in the manner in the embodiment of Fig. 2. A test unit having a plurality of chambers 18 yet made from a single piece of material is illustrated in Fig. 10.

It should be clearly understood that the above detailed description is to be taken by way of illustration only and not to be taken by way of limitation, the spirit and scope of this invention being limited onlyby the terms ofthe appended claims. a

I claim:

l. A load application. unit comprising a sheet of flexible materiahone side of which is adapted to engage a test specimen andassume the contour thereof; a pad of flexiblematerial attached to the opposite side of said sheet; a plurality of laterally spaced reinforcing members secured to said pad-remote from said sheet, each of said reinforcing members being provided with means adapted'to engage load producing means; and means for exhausting-the air from beneath said sheet thereby securing said unit to said specimen.

2. A device as recited in claim 1;.in which the periphery of said sheet of flexible material projects beyond said. pad-on all sides thereof,-and

includes in addition a secondsheet of flexible riphery and said specimen.

3.. A device as recited in claim 1 which includes in addition a sheet of porous material adapted to be interposed between said sheet of flexible material and said specimen with the periphery of said sheet of flexible material projecting beyond the periphery of said sheet of porous material.

4. A device as recited in claim 1 in which the surface of said sheet adapted to engage said test specimen is provided with groove means for facilitating the exhaustion of air from beneath said unit.

5. A load application unit comprising a sheet of non-porous flexible material one side of which is adapted to engage a test specimen and assume the contour thereof; a pad of flexible material attached to the opposite side of said sheet; a plurality of rigid plate members secured to said pad remote from said sheet; said plates being disposed in spaced relationship with each other for permitting flexure of said pad and said sheet; each plate being provided with means adapted to engage load producing means; said pad and said sheet having apertures therethrough for allowing exhaustion of air from beneath said sheet for holding said unit to said specimen.

6. A load application unit comprising a sheet of non-porous flexible rubber, the underside of which is adapted to complementarily engage a test specimen; a pad of flexible rubber attached to the opposite side of said sheet; a plurality of rigid metal plates attached to the surface of said pad remote from said sheet; said plates being disposed in spaced relationship with each other, said pad being provided with grooves between said plates for facilitating fiexure on said unit, said unit being provided with an aperture communicating with the underside of said sheet; and means connected with said aperture for creating a vacuum between said sheet and said specimen or attaching said unit thereto.

7. A load application unit for a test specimen comprising a sheet of porous material engaging the surface of said specimen; a sheet of nonporous material adapted to overlie said porous sheet with its periphery extending beyond said sheet onto the surface of said specimen; a vacuum sealing substance disposed beneath the periphery of said non-porous sheet; a pad of flexible material having substantially the width and length dimensions of said porous sheet attached to the central portion of said non-porous sheet on the side remote from said porous sheet; a plurality of rigid plate members attached to said pad remote from said non-porous sheet, said plate members being disposed in spaced relationship and adapted to engage load producing means; a second sheet of non-porous material adapted to overlie the periphery of said first mentioned non-porous sheet; and means for producing a vacuum between said first mentioned non-porous sheet and said specimen thereby securing said unit thereto.

8. A load application unit comprising an elongated flexible member, one side of which is adapted to engage a test specimen; a plurality of rigid plate members disposed in laterally spaced relationship and attached to said flexible member remote from said side adapted to engage a test specimen; and means for exhausting the air from beneath said flexible member for securing said unit to a test specimen.

9. A device as recited in claim 8 in which said side adapted to engage a test specimen is provided with a plurality of depending tab portions adapted to cooperate with said test specimen to provide a plurality of chambers therewith, and including means for evacuating each of said chambers.

10. A load application unit comprising a sheet of flexible material, one side of which is provided with a plurality of depending tab portions and adapted to engage the surface of a test specimen thereby cooperating with said specimen to provide a plurality of chambers between said sheet and said specimen; a pad of flexible material attached to the opposite side of said sheet; a plurality of rigid plates attached to said pad remote from said sheet in a spaced relationship with each other, said plates being provided with means adapted to engage load producing means; and means for evacuating each of said chambers for holding said unit to said specimen.

11. A device as recited in claim 10 in which said sheet of flexible material is provided with groove means between said tab portion for facilitating the exhaustion of air from said chambers.

12. A device as recited in claim 10 including in addition a sheet of porous material for each of said chambers and adapted to be received therein.

JAMES W. GAINES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,151,584 Bugatti Mar. 21, 1939 2,319,675 Grinter May 18, 1943 2,413,737 Weaver Jan. 7, 1947

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