Title: Inflatable device for installing strain gage bridges

What is claimed is:

1. In a method for installing in a tubular shaft, multiple electronic devices, such as strain gages, having bonding surfaces and leads extended therefrom, the steps comprising:

A. forming a flexible, template-like component from a thin sheet of Teflon, said template being provided with multiple openings for receiving said electronic devices and characterized by an etched bonding surface;

B. inserting electronic devices into the openings provided for said component with the bonding surfaces of the electronic devices being exposed at the etched surface of the template-like component, and the leads of the electronic devices being extended along the surface of the component opposite the etched surface thereof;

C. wrapping the component around an expansible cylinder with the etched surface of the template facing away from the cylinder thus to form an insertion assembly;

D. coating with adhesive the etched surface of the template and mounting surfaces of the electronic devices;

E. inserting the assembly to a desired depth within the tubular shaft; and

F. expanding the cylinder for forcing the surfaces of the template-like component and the surfaces of the electronic devices to which the adhesive has been applied into bonding contact with the adjacent surface of the shaft for thus bonding the component and electronic devices to the shaft.

2. In a method as defined in claim 1 wherein said expansible cylinder comprises a tube formed of silicon rubber sealed at each of its opposite ends by a rigid plate, the plate at one end of the tube being provided with a pneumatic valve for use in pressurizing the cylinder and said step of expanding the cylinder includes the step of pneumatically pressurizing the cylinder.

3. In a method as defined in claim 1 further including the step of bonding the leads to terminal boards mounted in said tubular shaft.

4. In a method as defined in claim 2 further including the steps of permitting the adhesive to cure, depressurizing the cylinder and removing the cylinder from the shaft, leaving said template-like component and electronic devices bonded to the internal surface of the tubular shaft.

5. In a method as defined in claim 5 wherein said cylinder is pressurized to 30 psi, the template-like component is formed from a sheet of 5 Mil. Teflon, and the plate at one end of the tube is connected to the plate at the other end thereof by a plurality of tie-bolts which serve to preclude axial separation of the plates as the cylinder is expanded.

6. In a device for use in installing in a tubular shaft, multiple electronic devices such as strain gages and the like having electrical leads extending therefrom, the improvement comprising:

A. means comprising an expansible cylinder having an outside diameter slightly less than the inside diameter of said tubular shaft;

B. a flexible template-like component with openings having strain gages secured therein, said component and said strain gages having a surface adapted to be supported by the external surface of said cylinder and an opposite bonding surface coated with an adhesive;

C. means for sealing the opposite ends of said expansible cylinder including a pair of rigid plates adhesively secured to said cylinder at the opposite ends thereof and means interconnecting the plates for preventing axial separation thereof; and

D. means for expanding said cylinder so as to bond said component and strain gages to said inside of said tubular shaft.

7. An improvement as defined in claim 6 wherein said expansible cylinder is made of silicon rubber, said template-like component is formed of 5 Mil. bondable Teflon, said plates comprise aluminum disks, and said means for preventing axial separation of the plates includes tie-bolts extended between and connected to said plate.

8. An improvement as defined in claim 6 wherein said means for expanding said cylinder includes a pneumatic valve coupled with one plate of said pair of plates.

9. A device particularly suited for use in installing strain gages internally of a tubular load bearing shaft, comprising:

A. an expansible cylinder formed of silicon rubber, said cylinder being characterized by an outside diameter less than the internal diameter of said shaft;

B. means for pneumatically sealing each of the opposite ends of said expansible cylinder including a pair of metallic plates adhesively secured to the cylinder and interconnected by a plurality of rigid tie-bolts, at least one of said plates being provided with a pneumatic valve for accommodating a pneumatic pressurization and depressurization of said cylinder;

C. a flexible template-like component for mounting strain gages on the external surface of said cylinder, said component formed of bondable Teflon and including a bonding surface engagable with the internal surface of said shaft and a plurality of openings defined in the template, strain gages secured in said openings in a manner such that a mounting surface for each strain gage protrudes through one of said openings formed in the component; and

D. means comprising an adhesive for uniting the bonding surface of the component and the mounting surface of each strain gage to the internal surface of said shaft in response to a pressurization of the cylinder.

Other info:


Inventors: Cook, Clarence E. (Lancaster, CA)
Smith, Glynn E. (Quartz Hill, CA)
Monaghan, Richard C. (Pearblossom, CA)

Application Number: 06/322314
Filing Date: 1981-11-17
Publication_date: 1983-10-04
Assignee: Nasa (US)

Primary Class(es): 156/215 156/71, 156/540, 156/235, 156/391, 338/2, 156/230, 15
Other Classes: G01L1/22; G01L1/20; E04B2/00; B44C1/00; G01L1/22; E04F13/00
US Patent Ref:

2421764	June, 1947	Swallow	156/230	Affixing characters to transparent drums
2711985	June, 1955	Olson	156/287	Process for bonding polyethylene to butyl rubber
2724672	November, 1955	Rubin	156/294	Method of applying thermoplastic polymers to solid surfaces
2941570	June, 1960	Plym	156/213	Method and apparatus for making tubes and hollow bodies of fibrous plastics
3513051	May, 1970	Lichfield	156/249	METHOD OF APPLYING LINERS WITH A PROTECTIVE COVER,TO ROCKET MOTOR CASINGS
3513430	May, 1970	Heller	338/4	SEMICONDUCTOR STRAIN GAGE TRANSDUCER AND METHOD OF MAKING SAME
4169749	October, 1979	Clark	156/293	Method of making a hollow airfoil
4318936	March, 1982	Moss et al.	338/4	Method of making strain sensor in fragile web

Other Refs: Other References: Moore, Epoxy Transfer and Print Head, p. 15, Western Electric Technical Dig., #50, 4/1978.
Butler et al., A Device for use in Apply Strain Gages to Cylindrical Specimens, Experimental Mechanics, 10/1966.

Primary Examiner: Kimlin, Edward C.
Assistant Examiner: Falasco, Louis
Attorney: Brekke, Darrell G.
Manning, John R.
Marchant, Robert D.