Abstract
The present apparatus provides an assembly that can be inserted into an open ended bore along the central axis of a fastener. The assembly can be used to continuously monitoring clamp load (tensile force) status throughout the life of a fastener and is attached at positions that help to reduce or eliminate problems that occur in existing load indicating fasteners that are associated with yielding, unknown force distribution, or stress versus elongation relationships occurring in non-uniform sections of a fastener. The apparatus has a design which makes it simple and inexpensive to manufacture and install.
Claims
1. An apparatus for measuring tensile load in a fastener, the apparatus comprising: a tubular base piece and a gauge pin; the tubular base piece comprising: a male coupler on the head of the tubular base piece; an inner diameter; the gauge pin comprising: a first section having a diameter less than the inner diameter of the tubular base piece; a second section with radial dimension that exceeds the inner diameter of the tubular base piece; an end section configured to attach within a central bore of a fastener.
2. The apparatus of claim 1, wherein the gauge pin has a second section that bears against the tubular base piece in order to maintains a predetermined distance between the end section of the gauge pin configured to attach within a central bore of a fastener and an outer diameter of the tubular base piece configured to attach within the central bore of the fastener.
3. The apparatus of claim 1, wherein the tubular base piece and the gauge pin are configured to be attached within a central bore of a fastener in order to measure the strain of a known region of the fastener.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0028] FIG. 1A shows an untensioned fastener in a bolted joint and two points that can be used for measuring strain.
[0029] FIG. 1B shows a tensioned fastener in a bolted joint and the new distance between the two points that can be used for measuring strain.
[0030] FIG. 2A shows an untensioned fastener in a bolted joint with an angled surface.
[0031] FIG. 2B shows a tensioned fastener in a bolted joint with an angled surface.
[0032] FIG. 2C shows the resulting permanent deformation of the fastener head.
[0033] FIG. 3A shows an untensioned fastener in a bolted joint with an oversized hole.
[0034] FIG. 3A shows a tensioned fastener in a bolted joint with an oversized hole.
[0035] FIG. 3C shows the resulting permanent deformation of the fastener head.
[0036] FIG. 4A shows a stud with a nut in a first position and depicts a first length from the bottom of the hole to the nut
[0037] FIG. 4B shows a stud with a nut in a second position and depicts a different resulting length from the bottom of the hole to the nut
[0038] FIG. 5A shows an assembly with washers present and depicts a length from the bottom of the hole to a nut.
[0039] FIG. 5B shows an assembly with washers present and depicts a different resulting length from the bottom of the hole to a nut.
[0040] FIG. 6 depicts a tubular base piece and gauge pin inserted into an open ended bore in a fastener.
[0041] FIG. 7A depicts the distance between two reference points along the central bore of an untensioned fastener.
[0042] FIG. 7B depicts the new distance between two reference points along the central bore of a tensioned fastener.
[0043] FIG. 8A depicts an untensioned fastener with a housing and sensor measuring the relative positions of two reference surfaces at the end of the untensioned fastener.
[0044] FIG. 8B depicts a tensioned fastener with a housing and sensor measuring the new resulting relative positions of two reference surfaces at the end of the tensioned fastener
[0045] FIG. 9A depicts an untensioned fastener with a three piece system that includes a tubular sleeve which during installation is used to maintain a known distance between where the gauge pin attaches to the fastener and where the tubular base attaches to the fastener.
[0046] FIG. 9B depicts a tensioned fastener with a three piece system that includes a tubular sleeve which during installation is used to maintain a known distance between where the gauge pin attaches to the fastener and where the tubular base attaches to the fastener.
[0047] FIG. 10 depicts a gauge with a symmetrical protrusion attached to, or a part of, the gauge pin, causing interference that will establish a known gauge length during installation of the device.
[0048] FIG. 11 depicts a gauge with a non-symmetrical protrusion attached to, or a part of, the gauge pin, causing interference that will establish a known gauge length during installation of the device.
[0049] FIG. 12 depicts a tubular base piece and gauge pin inserted into an open ended bore of uniform diameter in a fastener.
[0050] FIG. 13A depicts the present invention used in conjunction with a load indicating sensor residing primarily within the fastener.
[0051] FIG. 13B depicts a second configuration where the present invention used in conjunction with a load indicating sensor residing primarily within the fastener.
[0052] FIG. 14 depicts a bolted joint with a threaded studs where the points of attachment of the tubular base piece and the gauge pin are below the nut.
[0053] FIG. 15 depicts an assembly with a protective cap
[0054] FIG. 16 depicts a second assembly with a protective cap
[0055] FIG. 17 depicts a configuration where a measuring sensor can send a signal to a receiver. The figure also depicts a tightening device that can be controlled with hard wires or wirelessly.
DETAILED DESCRIPTION OF THE APPARATUS
[0056] The following description is of example implementations of the invention only, and is not intended to limit the scope, applicability or configuration of the invention. As will become apparent, various changes may be made in the function and arrangement of the elements described in these implementations without departing from the scope of the invention as set forth herein
[0057] With reference to FIG. 6, this apparatus is a gauge pin 2 having a non-uniform diameter, or having a protrusion, within a tension indicating assembly comprised of two or more pieces such that one piece is a tubular base 3 and one piece is the gauge pin 2, and where both pieces 2, 3 are inserted into a central bore of a tensile member 1 in which the tension is to be monitored. This tensile member 1 may typically be a threaded fastener, such as a bolt or stud, but does not need to be a threaded fastener. Part of the gauge pin 2 may pass through the tubular base 3. Both the tubular base 3 and the gauge pin 2 may be fixed to the fastener within the central bore at specific locations (PT. A shows the region where the base could be attached and PT. B shows the region where the pin could be attached). The means of attachment could be a press fit, adhesive, interference fit, weld or other means.
[0058] There are various methods that could be used for manufacturing the gauge pin 2. In fact, the gauge pin is very similar to ejector pins commonly used in plastic injection molding equipment. The larger diameter can be forged, or the smaller diameter can be turned down in a lathe process. In any case, it is preferred to make a gauge pin 2 with a similar coefficient of thermal expansion as the fastener. The tubular base 3 may also be manufactured with various well known methods such as drilling the central bore and turning the outside surfaces on a conventional lathe. It would also be possible to manufacture the gauge pin 2 and the tubular base 3 with a 3-D printer.
[0059] With reference to FIG. 6, FIG. 7a,b shows that when tensile member 1 is under stress, it may stretch such that the distance between PT. A and PT. B increases. As the distance between PT. A and PT. B increases, since the tubular base 3 and the gauge pin 2 may not stretch, the pin upper surface 4 will move relative to the tubular base upper surface 5 as depicted in FIG. 7b. The amount that the pin upper surface 4 moves relative to the tubular base upper surface 5 may be the same as the increase in distance between PT. A and PT. B. (This distance is exaggerated FIG. 7 and is typically only several thousands of an inch.)
[0060] The amount of increase in the distance between PT. A and PT. B when the tensile member is tensioned can be determined (FIG. 8a,b) by measuring the change of position between the pin upper surface 4 relative to the tubular base upper surface 5.
[0061] In this apparatus, the gauge pin 2 may be made such that it may have two diameters or some other protrusion, such that during installation of the apparatus, the interference and forces between the gauge pin 2 and the tubular base 3 may establish or maintain a desired distance between the PT. A on the tubular base 3 and the PT. B on the gauge pin 2. For example, during installation, while pressure is applied to the upper surface of the tubular base 2 to press or otherwise force it into position at PT. A within the tubular bore, a bearing surface on the tubular bore may simultaneously press the gauge pin 2 to the appropriate attachment position at PT. B.
[0062] In another installation scenario, the gauge pin 2 could first be pressed into the tubular bore of the tensile member 1 and then the tubular base 3 could be inserted into the bore and pressed until it interfered with the larger diameter on the gauge pin 2 or with a protrusion on the gauge pin 2. In any of the installation scenarios, a second diameter or a protrusion on the gauge pin 2 may physically bear against, or interfere with, a part of the base piece 3 such that a desired distance between PT. A and PT. B can be achieved or maintained during the installation of the apparatus.
[0063] Additional embodiments of this apparatus will now be described and some of these descriptions will correspond to specific drawings and figures.
[0064] FIGS. 8A and 8B show a sensor, which can be mechanical or digital. The sensor could mechanically measure 4 the position of the upper surface of the gauge pin 2 relative to 5 the upper surface of the tubular base 3. The sensor could also electronically sense the distance through non mechanical means such as using a circuit to measure changing inductance or capacitance in an air gap or by using sound or electromagnetic waves to reflect off of the top of the gauge pin 2. This sensor could be attached to the tubular base 3 or to the fastener 1 with a housing 6. The housing 6 could be attached with the aid of a recess 7 in the tubular base 3 which could assist in the precise locating of the sensor housing 6. The housing 6 could also attach to the tubular base piece 3 by using a coupling system using a series of movable rings or mechanical pieces similar well known coupling methods such as is used by some quick release pneumatic air hoses. A magnetic force could also be used to attach the sensor housing 6 to the tubular base 3. The sensor housing 6 could also be attached through a threaded interface. While the sensor 8 depicted in FIG. 8A and FIG. 8B shows the percent of proof load, alternative scales or simply colors could be used to indicate the tensile load of the fastener. While FIG. 8A and FIG. 8B show this measurement being made with the use of the housing 6, a measurement could also be made without the use of the housing 6. In this scenario a standard depth micrometer or other measuring device could be placed directly against the tubular base piece to measure 4 the position of the upper surface of the gauge pin 2 relative to 5 the upper surface of the tubular base 3.
[0065] FIGS. 9A and 9B show a three-piece assembly which has a tubular base 3, gauge pin 2, and also a spacer 8. This assembly works similar to the assembly in FIG. 6, however, rather than the tubular base 3 bearing directly against the gauge pin 2, the tubular base 3 may bear against the spacer 8 which may simultaneously bear against the gauge pin 2. One possible advantage of this embodiment is that it could be less expensive to manufacture than a longer base piece shown in FIG. 1. Another advantage is that the spacer 8 could easily be modified to different lengths allowing the apparatus to be customized for different applications. For example if it was desirable to have a longer distance between PT. A and PT. B, the apparatus could be customized by using a standard tubular base piece 3 in conjunction with a longer gauge pin 2 and a longer spacer 8.
[0066] FIG. 10 shows a gauge pin 9 with a symmetrical protrusion 10 attached to, or a part of, the gauge pin 9, causing interference such that the appropriate distance between PT. A and PT. B (where the gauge pin 9 is attached) may be achieved upon installation.
[0067] FIG. 11 shows a gauge pin 11 with a non-symmetrical protrusion 12 attached to the gauge pin 11, or part of, the gauge pin 11, causing interference such that the appropriate distance between PT. A and PT. B (where the gauge pin 11 is attached) may be achieved upon installation.
[0068] FIG. 12 shows an embodiment where the entire apparatus could be inserted into a single diameter central bore within the fastener 13. In this embodiment the machining of the fastener 13 could be as simple as drilling a single diameter hole, and the installation of the apparatus could be done by a relatively unskilled layperson or machinist. This embodiment would also enable a relatively easy installation of the apparatus into a fastener while the fastener was in an installation in the field.
[0069] FIG. 13A and FIG. 13B show an embodiment where the apparatus has a mechanical indicator 14 built into the tensile member 1. The mechanical indicator 14 could, for example, be the apparatus described in U.S. Pat. No. 5,668,323 issued to the present inventor and sold on the market today as the Maxbolt. Rather than using a mechanical indicator, an electronic indicator or sensor could be used within the fastener in a similar manner.
[0070] FIG. 14 shows and embodiment where the apparatus is installed in a threaded stud 15. In this configuration it would be possible to install the apparatus such that PT. A where the tubular base piece 3 is attached is below the bottom of the nut 22 in order to reduce or eliminate well known errors caused due to unknown strain in the region of the fastener where it is engaged with the nut.
[0071] FIG. 15 shows and embodiment where a tubular base 16 does not protrude beyond the end of the fastener. In some installations this would reduce the risk of the tubular base being damaged. In this embodiment there could be a protective cap 17 attached directly to the fastener as shown or attached to the tubular base piece 3. In this embodiment, a sensor could attach to a modified housing that in turn is attached to the tubular base 16 in a way that better accommodates this embodiment such as by using the central bore to help position the housing or by using a magnetic force to attach a sensor housing to the tubular base 16. This embodiment also shows a possible position of a sealing o-ring 23 under the protective cap 17.
[0072] FIG. 16 shows and embodiment with a protective cap 18 that may be plastic, metallic, or some other appropriate material. The cap could be sealed with o-rings and it could attached with a threaded interface, or snap on, or attach through other means.
[0073] FIG. 17 shows and embodiment in which the apparatus could include an attached sensor 19 that sends out a signal through a wire 24 or wirelessly, such as bluetooth or other electromagnetic wave frequencies, that is received by an electronic receiving device 20 such as a smartphone, computer, or other receiver. The received data could be stored or displayed in order to record a history, or current state, of the tension in the fastener, or to set off an alert if the tension deviated from a predetermined range, or to provide other information about the assembly to ensure optimal performance, longevity and safety. The data could also be used to control a tightening device 21 such as a hydraulic torque wrench so that the fastener achieved a desired tension. The connection between the electronic receiving device 20 and the tightening device 21 could be a wire 25 or wirelessly.
[0074] In various additional embodiments the apparatus could include an additional device to receive data from multiple fasteners in an assembly, wherein these data are used to determine, and then inform the user of, a preferred tightening procedure. The procedure could be continually updated as the fasteners are being tightened in the assembly. Since tightening one fastener in an assembly can affect the tension in neighboring fasteners, the device could use the real time data, as well as the historical data, to determine a preferred tightening procedure that could include details of which fasteners to tighten and how much to tighten them. The means by which this embodiment would determine the preferred tightening procedure would involve a computer program or smartphone app that could consider many possible variables, such as the desired tensions, fastener proof loads, temperatures, desired differences in tensions, real time data regarding the dynamic tensions and how fasteners affect one another, and other variables. These programs or phone apps could be easily customized by the manufacturer or end user depending upon their needs and the available tightening equipment. These programs could also connect to, and control, a torque wrench or other type of tightening equipment.
[0075] In various embodiments the apparatus could include a visual or audible signal emitter on the apparatus such that a light or sound or color change or some other means of alert was emitted when the tension deviated from a predetermined range.
[0076] In various embodiments the apparatus could include a receptacle on the sensor or sensor housing for holding the protective cap. The sensor or sensor housing could hold the cap in many ways; for example, the sensor or sensor housing could have a magnet that attracted a metallic metal cap or it could have a face or protrusion similar to the tubular base piece or the fastener head and the cap could attach to the sensor using the same process that it attaches to the load indicating fastener or tubular base.
[0077] In various embodiments of the apparatus the upper surface of the gauge pin 2 and the upper surface of the tubular base 3 are not necessarily flush with one another upon installation in the untensioned fastener 1.
[0078] In various embodiments of the apparatus, one of, or both, the gauge pin 2 and the tubular base 3 could be attached to the internal bore through various means such as an adhesive, welding, threads, press fit, or interference fit. Adhesive bonding methods could involve anaerobic processes as well as exposure to chemicals, light, or certain temperatures.
[0079] In various embodiments the apparatus could have many methods and coverings to protect the surfaces from moisture and dirt. One method of protection could include the use of a flexible or non-flexible sealant used to prevent moisture from entering the apparatus rather than, or in addition to, o-rings. Internal gaps or spaces could be filled with an inert or rust protecting substance such as grease.
[0080] In various embodiments the apparatus could be used to monitor tension and load in a non-threaded fastener or tensile member used to join two or more parts of an assembly and used to support another object such as with a crane hook.
[0081] In additional various embodiments, in order to aid in anchoring the gauge pin at point B, the gauge pin could be comprised of 2 or more pieces. For example in order to attach the gauge pin at point B, a lower section of the gauge pin could be comprised of an expanding section that expands outward and anchors to the fastener as the gauge pin is pressed into the fastener. Such expanding sleeves are used throughout industry and are similar to a sleeve that is commonly used to anchor screws or nails in drywall or concrete. This expanding press fit can be achieved in many ways and can be used to attach the gauge pin as well as attach the tubular base. This expansion attachment method could also be driven by forces applied by a spacer similar to the spacer that was described with FIG. 9 but modified to drive the expansion of the sleeve.
