US3355851A

US3355851A - Method and apparatus for securing thin-skinned structures

Info

Publication number: US3355851A
Application number: US444164A
Authority: US
Inventors: Norman M Imbertson; Loring E Tabor
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-03-31
Filing date: 1965-03-31
Publication date: 1967-12-05
Anticipated expiration: 1984-12-05

Description

Dec. 5, 1967 N. M. IMBERTSON ETAL 3,

METHOD AND APPARATUS FOR SECURING THIN'SKINNED STRUCTURES Filed March 31, 1965 2 Sheets-Sheet 1 jA/VEA/TO/QS- JVZD/QMQA/ M [awzersav l GEM/6 B 1250/? N- M. lMBERTSON ETA; 3,355,851

Dec. 5, 1967 METHOD AND APPARATUS FOR SECURING THIN-SKINNED STRUCTURES Filed March 51. 1965 2 Sheets-Sheet JNVE'A/TOP-S. Woe/144w M 114552750 1 aQ/A/c; 1 11050.?

United States Patent 3,355,851 METHOD AND APPARATUS FOR SECURING THIN-SKINNED STRUCTURES Norman M. Imbertson, 1020 Inverness Drive, Pasadena,

Calif. 91103, and Loring E. Tabor, 3563 Motor Ave.,

Los Angeles, Calif. 90034 Filed Mar. 31-, 1965, Ser. No. 444,164 Claims. (Cl. 52-698) ABSTRACT. OF THE DISCLOSURE A method and structure for securing the extremities of a thin-skinned structure, including a collapsible dam to a base. The structure is a clamping device including a body member adapted to be supported bya base, a first generally hook shaped arm portion extending from the body member and having a portion adapted to be supported by a base and a second generally hook shaped arm extending from the body member and spaced above the base to receive a portion of the thin-skinned structure and maintain it against dislodgment from the clamping device when the device is secured.

This invention relates to a method and to a specific apparatus for securing thin-skinned structures and the like. More particularly, this invention relates to a method and a specific apparatus for securing the extremities of a collapsible damstructure, or the like, to a foundation so that, upon being fully extended, the dam will attain a desired configuration and will be firmly held against. its foundation so as to establish a fluid impervious barrier to fluid contained by thecollapsible dam.

In order for a thin-skinned structure nuch as a collapsible dam to be effective in establishing a fluid impervious obstruction to fluid contained by the. dam, the method of securing the dam to its foundation and the structural means utilized for securing the dam to its foundation must provide a fluid-tight bond between. the floor of the dam and the foundation to which the dam. is secured. Also, in the form of such a dam which has several parts the floor of the dam must be joined with the additional peripheral surfaces of the dam by a method which will provide a fluid impervious obstruction to fluid contained by the dam. In establishing a fluid-tight bond be tween the floor of the dam and the foundation to which the dam is secured, it is necessary to provide securing apparatus which will exert a strong downward force against the extremities of the collapsible darn. Also, since the collapsible dam is made of pliant material, such as rubber or the like, it is necessary to provide a securing apparatus which will not cut, tear or damage the peripheral surface of the dam in any way. Additionally, the method utilized for joining the floor of the dam withthe other peripheral surfaces must produce a fluid impervious bond capable of being securely retained within a securing apparatus usedfor establishing a fluid-tight bond' between. the floor of the dam and the foundation to which the damis secured.

Therefore; an important object ofthis invention" is to provide a method of joining the floor of a thin-skinned structure toother peripheral surfaces of the structure so as to establish the fluid impervious bond between the surfaces so united.

Another'obj'ect of this invention is to provide a method of joining the door of a thin-skinned structure to the other peripheral surfaces of the structure. so as to establi'sh a fluid impervious surface capable of being securely retained within a. securing. apparatus used for establishing a fluid-tight bond between. the floor of the structur and the foundation to which the structure is secured.

Another object of this invention is to provide securin apparatus for a thin-skinned structure which is capabl of exerting suflicient force on the structure so as to estab lish a fluid impervious bond between the floor of th structure and the foundation to which the structure is se cured.

Another object of this invention is to provide securin; apparatus for a thin-skinned structure which has tht requisite strength and configuration for establishing a firn grip on an external surface of the thin-skinned structure and equalizing the stresses in the thin-skinned structurr even though the thin-skinned structure has joints of non uniform thickness throughout its length.

Another object of this invention is to provide a securing apparatus for a thin-skinned structure which may be fastened as firmly against the exterior surface of the struc ture as desired, and yet will not damage the structure it any way.

Another object of this invention is to provide a securing apparatus for a collapsible dam which may be easily and inexpensively manufactured.

Still another object of this invention. is to provide securing apparatus for a thin-skinned structure so that tensile stresses in the thin-skinned peripheral surface section of the structure cause the securing apparatus to tighten and increase its holding power on the thin-skinned structure.

That these and other objects and advantages of the invention are obtained will be readily apparent from a consideration of the following description when taken in conjunction with the drawings, in which:

FIGURE 1 is a sectional view showing a collapsible dam held in position by the securing apparatus of this invention.

FIGURE 2 is a transverse sectional view of the securing apparatus.

FIGURE 3 shows another transverse sectional view of the securing apparatus shown in FIGURE 2.

FIGURE 4 is a fragmented perspective view of a perforated tubular part of the securing apparatus.

FIGURE. 5 shows a transverse sectional view of another embodiment of' the securing apparatus.

FIGURE 6 shows a transverse sectional view of a securing apparatus similar to that shown in FIGURE 5 but usedin a somewhat different manner.

FIGURE 7 shows a transverse sectional view of still another embodiment of the securing apparatus.

FIGURE 8 shows a perspective view of the clamping device and plate portions of the securing apparatus.

FIGURE 9- shows a transverse sectional view' of a still further embodiment of the securing apparatus of this invention;

Since this invention is particularly suitable for securing collapsible dams reference in the following descriptionwill' beto: such a dam.

Referring to FIGURE 1 of the drawings, a fully ex.- tended collapsible dam 10 is shown secured to a concrete foundation 11. Clamping

devices

12 and 12 firmly grip the

lateral extremities

13 and 13 of the dam 1'0, and exert a downward force upon the darn 10 pressing it against the foundation 11'.

A pliant. material such as rubber, plastic or the like, is utilized as an outer'covering for the collapsible dam.10. In constructing the dam, either one or two sections of the pliant material are generally used. In the form hereinafter described two sectionsofthe pliant material are used. A. first. section is used toestablish a floor 14. for the dam", and a second section is used to establish the ad; ditional peripheral surface 15 of the dam. Since the 3 nterior of the dam in this embodiment is closed by two e-parate sections of pliant material, it is of paramount mportance that the two

sections

14 and 15 be joined to- .ether by an effective process whereby the peripheral urface of the dam is made impervious to fluids and also ecured firmly to the foundation 11. If asingle sheet of iliiant material is used it is still necessary that it be se- :ured firmly to the foundation 11 though, of course, here is no problem then with joining sections together.

Numeral 22 designates the central body member of the :lamping device 12, while

numerals

23 and 24 designate generally hook shaped arms projecting from the body 22. the arm 23 adjacent the body 22 is provided with central penings 25 for receiving bolts 26. The nut 26A on bolt 26 nay be adjusted to provide the amount of retaining force ieeded to hold the clamping device 12 in position rela- .ive to dam 10. The retaining bolt 26 may be mounted in larious ways to be more fully described hereinbelow in )rder to secure clamping device 12 to the foundation 11. These bolts 26 are lodged securely in the foundation 11 with a threaded end which can be engaged by nut 26A projecting out from the foundation.

A flat sided plate 27 is secured on top of the bottom section 14 of the dam beneath the clamping device 12. Matched in position and size to openings 25 in clamping device 12 are openings 25A in plate 27 through which bolts 26 may be passed. Extending near the edge of plate 27 is longitudinal rounded stop or bump 27A which is positioned on the surface of plate 27 so that when bolts 26 are passed through both openings 25A in plate 27 and openings 25 in clamping device 12, stop 27A is underneath the rounded end 29 of arm 24 and is close enough thereto to firmly hold layers of material which pass between end 29 and arm 24.

The arm 23 projecting from body 22 contacts plate 27 at surface 30 thereof. Arm 23 has a large radius of curvature and thus provides vertical and lateral strength to the securing apparatus 12.

The arm 24 projecting from body 22 has a relatively small radius of curvature. Arm 24 is provided with a smooth external surface and a rounded end 29 so that arm 24 may grip the plaint material of dam 10 between rounded end 29 and stop 27A of plate 27 firmly but not damage the material in any way. Arm 24 has openings 32 between rounded end 29 and body 22 and also may have threaded holes 34 for receiving screws 36. A cavity 37 is formed between arm 24, body 22 and plate 27.

A cylindrical tubular member 38 having plurality of holes 40 is preferably used with this apparatus and is shaped so that it may be closely fitted within the cavity 37 defined between curved arm 24, body 22 and plate 27 when the clamping device 12 and plate 27 are secured in place by bolt 26. This tubular member 38 is preferably made of a relatively rigid deformable material such as plastic, light metals, etc. which will bend without breaking upon the application of pressure to its surfaces. A solid cylidrical rod 42 which can be fitted loosely within a hollowed-out portion 49 of tubular member 38 is also used with this securing apparatus.

In still another embodiment of this invention a thinskinned structure such as the collapsible dam hereinbefore described can be secured to a foundation 11 directly without using intermediary plate 27 having a rounded stop 27A. Such a clamping device is shown in FIGURE 9. It has a central body member 22 and hook shaped

arms

23 and 24 as previously described. The clamping device is secured to the foundation 11 by screwing down nut 26A on bolt 26 .until

feet

30 and 39 press against the surface of the foundation. A rod 42 is inserted into the cavity formed between arm 24 and foundation 11. A portion of a single sheet 15 of a dam to be secured to foundation 11 is wrapped around the rod 42 and firmly held in place byvbeing-pressed between the outside surface of rod 42 and theinside surface of arm 24. Also, the rounded end 29 of arm 24 extends far enough that it can firmly press the overlapped portions of sheet 15 against the foundation 11 when the clamping device is fixed into place. In all other respects this form of the invention functions substantially the same as that previously de- 5 scribed.

An example of how this securing apparatus is used for a collapsible dam 10 is shown in the drawings. The dam 10 is secured by this invention to a foundation 11 with the floor portion 14 of the dam placed flat against the surface 16 of the foundation 11. Then plates 27 with bump 27A up are placed with their fiat sides on floor portion 14 near each edge which is to be secured to foundation 11.

Then the pliant peripheral surface 15 of the darn 10 is placed over the stop 27A and an adjacent fiat surface of plate 27. i

A hollow tubular member 38 preferably having a loosely fitting rod 42 contained therein is placed on the peripheral surface 15. The peripheral surface 15 is then lapped over the member 38. Securing apparatus 12 is placed over the plate 27 and

darn surfaces

14 and 15 so that the rounded end 29 of arm 24 and stop 27A are aligned and openings 25 are aligned with openings 25A so that bolt 26 will pass through both of these openings. In this position as shown in FIGURE 2 cavity 37 is formed between arm 24, body 22 and plate 27. Within this cavity 37 is tubular member 38 and rod 42. As shown in FIGURES 2, 3 and 6 the peripheral surface 15 may be secured to arm 24 by screws 36 being engaged in holes 34. Also, as shown in FIGURE 6 it is possible to eliminate the tubular member 38 and merely have a rod 42 in the cavity 37. The tubular member 38 is bent by any suitable means so as to make it tend to conform to the shape of cavity 37 as shown in FIGURES 3, 5 and 7. Ordinarily, the tubular member 38 is so deformed when the clamping device 12 is pressed tightly against it.

The next step is to draw the surfaces of the dam together by tightening nut 26A on bolt 26 until the rounded end 29 of arm 24 and stop 27A of plate 27 firmly press the overlapped portions of peripheral surface 15 together. At this time, because of the configuration of the clamping device 12, arm 23 thereof presses against plate 27 at 30 and central portion 22 presses against plate 27 at 39. It should be noted that the shape and size of the parts of the clamping device 12 are designed so that when rounded end 29 of arm 24 is close enough to stop 27A to squeeze overlapped material between them, plate 27 is firmly pressed by central portion 22 at 39 and arm 23 at 30.

Then tapered holes 44 are punched through peripheral surface 15 which correspond to holes 32 in arm 24. Through these holes 32 and 44 a hard setting adhesive in liquid form, such as an epoxy type cement, is injected under pressure so that it fills the space in cavity 37 and hollow portion 49 of tube 38 by passing through the holes 40 in tubular member 38. This cement will urge the deformable tubular member 38 to tend to conform to the internal surfaces of arm 24 and plate 27 defining cavity 37 and cause rod 42 to be suspended in the cement so that it takes a position when the cement sets like that shown in FIGURES 3 and 5.

Another method for joining the

sections

14 and 15 of the collapsible darn 10 so as to establish a fluid impervious dam structure as shown in FIGURE is described with particularity hereinafter. The pliant material which is 5 to constitute the floor 14 of dam is stretched upon the upper surface 16 of the foundation 11. The pliant material which is to constitute the peripheral surface of the dam is placed upon the material of floor 14. The tubular members 38 are placed on top of the two sections 70 of the material and near the edges thereof. Then the

sections

14 and 15 of pliant material of the thin-skinned structure are lapped over the member 38 as showndn FIGURE 5. The

sections

14 and 15 of the dam which are lapped over member 38 establish contact along the sur- 75 faces shown in FIGURE 5 and may be joined by an epoxy cement. The sections of material so united will then be firmly held by securing apparatus such as shown in FIG- URE 5. The cavity 37 and hollow portion 49 of tubular member 38 shown in FIGURE 5 is also filled with epoxy cement as previously described so as to insure the establishment of a firm bond between the peripheral section 15 and the floor 14 of the dam 10. Of course, appropriate tapered openings 44A corresponding to holes 32 in arm 24 and holes 44 in the peripheral section 15 are provided so that cement may be inserted.

The securing apparatus as shown in the drawings may be made long enough to secure the entire length of one side of a collapsible dam to its foundation by means of a single securing apparatus. Alternatively, the securing apparatus may be made considerably shorter than the length of one side of the collapsible dam. In the latter event one side of the darn wil be secured to its foundation by a plurality of adjacently disposed securing apparatus.

Also, because of the manner of securing the thinskinned structure previously described, uniform frictional restraint is provided under stress even though the thinskinned structure may have a non-uniform thickness.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations may be readily apparent to those skilled in the art, and the invention is to be given its broadest possible interpretation consistent with the prior art.

What we claim as our invetnion and desire to secure by Letters Patent is:

1. Apparatus for securing a thin-skinned structure, said apparatus comprising: a clamping device with a central body member having at least one portion which is capable of pressing the surface to which the structure is secured and said clamping device having at least one centrally positioned opening; a first arm member extending from said central body member, said first arm member having at least one portion which is capable of pressing the surface to which the structure is secured; a second arm member extending from said central body member on an opposite side from said first arm member, said second arm member having a radius of curvature less than that of said first arm member; a plate member having at least one opening and being provided with a longitudinally extending stop which is positioned so as to be aligned with the end of the second arm member of said clamping device when the openings of the clamping device and the plate member are aligned so that the end of the second arm of the clamping device and the stop of the plate may secure layers of thin-skinned structure between them when the clamping device and plate are clamped together; holding means extending through the opening in the clamping device and in the plate member, said holding means providing the amount of retaining force needed for holding said clamping device and said plate member in a predetermined position so that a cavity is defined between the plate member and the central body and second arm of the clamping device; a deformable perforated hollow tubular member fitting within said cavity so as to firmly press material lapped around said tubular member against the walls of the cavity; and a cylindrical rod which loosely fits within the hollow tubular member.

2. Apparatus for securing a thin-skinned structure as defined in claim 1 wherein the end of the second arm of the central body member and the stop on the plate memher are rounded.

3. Apparatus for securing a thin-skinned structure as defined in claim 1 wherein the spaces within the cavity be tween the plate member and the second arm of the clamping device are filled with a hard-setting cement.

4. Apparatus for securing a thin-skinned structure, said apparatus comprising: a clamping device with a central body member having at least one portion which is capable of pressing the surface to which the structure is secured and said clamping device having at least om centrally positioned opening; a first arm member extend ing from said central body member, said first arm member having at least one portion which is capable of pressing the surface to which the structure is secured; a second arm member extending from said central body member on an opposite side from said first arm member, said second arm member having a radius of curvature less than that of said first arm member; a plate member having at least one opening and being provided with a longitudinally extending stop which is positioned so as to be aligned with the end of the second arm member of said clamping device when the openings of the clamping device and the plate member are aligned so that the end of the second arm of the clamping device and the stop of the plate may secure layers of thin-skinned structure between them when the clamping device and plate are clamped together; holding means extending through the opening in the clamping device and in the plate member, said holding means providing the amount of retaining force needed for holding said clamping device and said plate member in a predetermined position so that a cavity is defined between the plate member and the central body and second arm of the clamping device; a deformable perforated hollow tubular member fitting within said cavity formed between the second arm, central body and the plate member so as to firmly press material lapped around said tubular member so as to firmly pres-s material lapped around said tubular member against the walls of the cavity; and a cylindrical rod which loosely fits within the hollow tubular member, said cavity having spaces which are filled with a hard-setting cement so that when the thin-skinned structure traverses around the stop, on the plate, within the cement-filled cavity, and around the second arm member to its top position whre it is held by holding means the friction against the thin-skinned structure will be increased under stress and uniform restraint will be provided on the thin-skinned structure.

5. An elongated clamping device retaining a relatively thin-skinned structure to a generally fiat base including tie down means, comprising: a central support body member including a portion suported by said base, a first generally hook shaped arm portion projecting from said body member and including an end supported by said base on a plane with said central support body member portion supported by said base, at least one opening in said first hook shaped arm portion receiving said tie down means, a second generally hook shaped arm portion projecting from said body member opposite said first generally hook shaped arm portion, said second generally hook shaped arm portion terminating in spaced relation from said base with said clamping device supported by said base, a cavity defined between said second generally hook shaped arm portion and said base, said cavity receiving a portion of said thin-skinned structure, a cylindrical rod fixedly secured to said thin-skinned structure Within said cavity and to firmly pressing said thin-skinned structure against the wall of said cavity, whereby said tie down means to secure said clamping device to the base, and said second generally hook shaped arm portion and said cylindrical rod retain said thin-skinned structure against dislodgment from said cavity.

6. An elongated clamping device retaining a relatively thin-skinned structure to a generally flat base including tie down means as defined in claim 5 wherein said base includes an anchor plate disposed under said clamping device, and said anchor plate includes a stop means fixedly positioned below said second hook shaped arm restricting access to said cavity whereby said portion of said thinskinned structure maintained in said cavity is held by said stop and said second book shaped arm in relatively tight frictional engagement.

7. An elongated clamping device retaining a relatively thin-skinned structure to a generally flat base including tie down means as defined in claim 6 wherein said step meanszis an elongated generally half round in cross section bar corresponding-in length to the length'of said clamping-device.

v8. Anapparatus securing a thin-skinned structure comprising: a clamping device having a central body member, said clamping device being provided with at least one opening; a plate-member, said plate member having at leastone-smooth surface on which said central bodymemberis mounted; said plate member being provided with at .least one opening; holding means extending through the opening tin-said clamping device and in said plate member; said holding means providing the necessary amount 'of retaining force needed for holding said central body member in position relative to said structure; an arm member-extending from said central body member, said arm member being provided with a rounded depending end"having.asmooth-rsurfaceso that said arm member :grips saidthin-skinned structure -firmly,as desired without v damagingthe m at'erialvthereof, :a cavity beingdefined by rtherplatevmember, armwmember and central body memberv and receiving said thin-skinned structure and an elong-ated cylindricahmember beingfitted within said cavity wherein the cylindrical member isaa deformable perforated EhDHOW-LtHbBrWhlCh firmly rpresses said-structure lapped .around said tubezagainst the wall of the cavity anda solid cylindrical rod embedded within cement so. as to be fixedly ..maint-ained within the hollow tube whereby .said struc- .tu'reis securelyanchored .against dislodgment from said .1 clampingrdevice.

T 9. Aimethod'of joining sectionsof a thin-skinned structure comprising: stretching a first section of pliant ma- -terialwhich-constitutes the fioor of said structure upon a -supportin g surface; placing a plate with aflat surface down on thefloor near each of the edges of said floor which is -to be secured; placinga second section of pliant material :forming' the peripheral su'rfaceof said thin-skinned struc- =-ture -on- ;said -plates; placing a perforated deformable ho1- low tube containing a loosely fitting rod upon the second vsection-of, pliant-materialwhere-itliesonthe plate; wrap- =ping t-he secondsection ofpliant material around the holv\lowtube; rpositioningta-.clamping'device over the plate and shollowztubeso that it contacts the plate so as to form a cavity between the :clamping device and the plate and -.also contactsfithe peripheral section of pliantwmaterial awhere it is -wrappedaroundthehollow tube; securing the =plateandnclamping:means to the supporting surface so astoipressithqportion of the peripheral surface which lap around the tubular -member together between the clampingidevice and r-t-he qplate; and also to press the peripheral surface of the thin-skinned structure. between the clamping deviceand the hollow tube which is, thereby deformed soas to substantially conform to the shape of said-cavity; and injecting a hard-setting cement into the cavity formed between the plate vmember and the clamping memberso as to fill the spaces in said cavity and within the hollow tube so that the deformable hollow-tube tends to conform to the walls of said cavity thereby securing the peripheral section of said thin-skinned structure within said cavity and causing the rod to be suspended by the cement within said hollow tube.

10. A method of joining sections of a thin-skinned structure comprising: stretching a section of pliant material which constitutes the floor of said structure along'a supporting surface; superimposing upon said first mentioned section a second section of pliantmaterial which constitutes further peripheral surface of said structure; placing a perforated tubular member upon the two sections of pliant material and;near the ends thereof; placing a cylindrical member of smaller diameter than the internal diameter of said tubular member within said tubular member; wrapping the two. sections of pliant material over the tubular member so as to establish a double thickness of the two sections of pliantmaterial; joining said sections of pliantmaterial with a hard setting cement; filling all spaces within the tubular member and between the cylindrical rod and the sections of pliant material .with a hard-setting cement; and clamping said sections of pliant material and tubular member together so as to allow .a

-firm bond to be established betweenall contactingsurfaces of the tubular member and the sectionsof pliant material and also to secure the bonded pliantrnaterial firmly to the supporting surface.

References Cited UNITED STATES PATENTS 1,964,818 8/1934 -HOOd 5 22 2,566,748 9/1951 Ringrose 6130 2,798,502 7/ 1957 'DAzzo 135-5 2,914,776 12/1959 Hotz 52-2 X 3,199,258 8/1965 Jentoft et a1. 52-222 3,208,095 9/1965 Hill 52fi273 X 3,246,474 4/ 1966 Mesnager 61-30 FOREIGN PATENTS 705,684 3/1965 Canada. 1,346,729 11/ 1963 France.

887,137 1 1/1962 Great Britain.

EARL J. WITMER, Primary Examiner.

Claims

5. AN ELONGATED CLAMPING DEVICE RETAINING A RELATIVELY THIN-SKINNED STRUCTURE TO A GENERALLY FLAT BASE INCLUDING TIE DOWN MEANS, COMPRISING: A CENTRAL SUPPORT BODY MEMBER INCLUDING A PORTION SUPPORTED BY SAID BASE, A FIRST GENERALLY HOOK SHAPED ARM PORTION PROJECTING FROM SAID BODY MEMBER AND INCLUDING AN END SUPPORTED BY SAID BASE ON A PLANE WITH SAID CENTRAL SUPPORT BODY MEMBER PORTION SUPPORTED BY SAID BASE, AT LEAST ONE OPENING IN SAID FIRST HOOK SHAPED ARM PORTION RECEIVING SAID TIE DOWN MEANS A SECOND GENERALLY HOOK SHAPED ARM PORTION PROJECTING FROM SAID BODY MEMBER OPPOSITE SAID FIRST GENERALLY HOOK SHAPED ARM PORTION, SAID SECOND GENERALLY HOOK SHAPED ARM PORTION TERMINATING IN SPACED RELATION FROM SAID BASE WITH SAID CLAMPING DEVICE SUPPORTED BY SAID BASE, A CAVITY DEFINED BETWEEN SAID SECOND GENERALLY HOOK SHAPED ARM PORTION AND SAID BASE, SAID CAVITY RECEIVING A PORTION OF SAID THIN-SKINNED STRUCTURE, A CYLINDRICAL ROD FIXEDLY SECURED TO SAID THIN-SKINNED STRUCTURE WITHIN SAID CAVITY AND TO FIRMLY PRESSING SAID THIN-SKINNED STRUCTURE AGAINST THE WALL OF SAID CAVITY, WHEREBY SAID TIE DOWN MEANS TO SECURE SAID CLAMPING DEVICE TO THE BASE, AND SAID SECOND GENERALLY HOOK SHAPED ARM PORTION AND SAID CYLINDRICAL ROD RETAIN SAID THIN-SKINNED STRUCTURE AGAINST DISLODGMENT FROM SAID CAVITY.