Methods and systems for measuring hose resistance.

(54) Title: METHODS AND SYSTEMS TO MEASURE THE RESISTANCE OF HOSES. (54) Title: METHODS AND SYSTEMS FOR MEASURING HOSE RESISTANCE.

(57) Summary

Systems and methods are disclosed for detecting degradation and failure, including failure types, in a hose assembly. A system includes a hose degradation monitoring circuit having a hose assembly including a hose having first and second conductive layers, and a degradation monitoring circuit configured to detect resistance of the hose through the conductive layers. The degradation monitoring circuit includes a voltage source electrically connected to the first conductive layer, and a resistor electrically connected between the second conductive layer and ground. The degradation monitoring circuit further includes a voltage monitoring circuit electrically connected between the resistor and the second conductive layer, to periodically monitor a voltage in place and detect possible failure of the hose assembly based on determining that, based on at least in part at a change in voltage in place over time, a resistance of the hose assembly has passed a threshold level.

(57) Abstract

Systems and methods for detecting degradation and failures, includ types of failures, in a hose assembly are disclosed. One system ineludes a hose degradation monitoring Circuit having a hose assembly including a hose having first and second conductive layers, and a degradation monitoring Circuit configured to detect a resistance of the hose across the conductive layers. The degradation monitoring Circuit ineludes a voltage source electrically connected to the first conductive layer, and a resistor electrically connected between the second conductive layer and ground. The degradation monitoring Circuit further ineludes a voltage monitoring Circuit electrically connected between the resistor and the second conductive layer, to periodically monitor a voltage at the location and detect a possible failure of the hose assembly upon determining that, based at least in part on a change in the voltage at the location over time, a resistance of the hose assembly has passed a threshold level.

PATENT TITLE No. 360852

Owner (s): EATON CORPORATION

Address: Eaton Center, 1111 Superior Avenue, Cleveland, Ohio, 44114-2584, USA

Name: METHODS AND SYSTEMS FOR MEASURING HOSE RESISTANCE,

Classification:

Inventor (s):

CIP: F16L11 / 112; F16L11 / 08; F16L11 / 127; F16L25 / 01; F16L33 / 207; G01M5 / 00;

G01N27 / 04; G01N27 / 20

CPC: F16L11 / 086 ;. F16L11 / 112; . F16L11 / 127; F16L25 / 01; F16L33 / 2076;

G01M5 / 0025; G01M5 / 0083; G01N27 / 20; G01N27 / 041

SUBHASH UPASANI SAMEER: SHINDE ABHAY: LLIS PEREIRA

REQUEST

Number: International Presentation Date:

MX / a / 2014/012716 April 23, 2012

Validity: Twenty years

Venclmi eMo date: April 23, 2032

Issue Date: November 20, 2018

The reference patent is granted based on articles 1 '^J. 2 “section V. 6th section lll, and 59 of the Industrial Property Law.

Pursuant to Article 23 of the Industrial Property Law, this patent has a validity of twenty unexpired years, counted from the date of filing of the International application and will be subject to the payment of the fee to maintain the rights in force. .

Who subscribes e! I did this title based on the provisions of articles 6 fractions lll and 7 bis 2 of the Industrial Property Law (Official Gazette of the Federation (DOF j 06/27/1991, amended on 0208/1994, 10/28) / 1995, 12/26/199/1 // 06/1999, 01/26/2004. 06/16/2005, 01/25/2006, 05/06/2009, 06/01/2010, 18, «6 / 2010. 06/26/2010, 01/27/20 ^ 2, 04/09/2012. 06/01/2016 and 03/13/2018); articles 1. 3rd section V subsection a), 4th and 12 * sections I and lll of the Regulations of the Mexican Institute of Industrial Property (DOF 12/14/1999, amended on 07/01/2002, 07/15/2004, 28 / 07/2004 and 7/09/2007); articles Γ, 3 ". 4. 5th fraction V item a). 16 fractions I and lll and 30 of the Organic Statute of! Mexican Institute of Industrial Property (DOF 12/27Ί999 amended on 10/10/2002, 07/29/2004, 08/04/2004 and 09/13/2007); 1, 3 and 5 “subsection a) of the Agreement that delegates powers to the Deputy Directors General, Coordinator, Divisional Directors. Holders of the Regional Offices, Divisional Deputy Directors, Departmental Coordinators and others s., R .-, - lte.-no-, of the Instituto Mexirocan ce a Industrial Property. (DO F. 12/15/1999, amended on 02/04/2000, 07/29/2004, 08/04/2004 and 09/13/2007),

This letter is signed with an advanced electronic signature (FIEL), based on articles 7 BIS 2 of the Industrial Property Law; 3rd of its iRegulation, and 1 section III, 2 section V, 26 BIS and 26 TER of the Agreement establishing the regulations for the use of the Electronic Payment and Services Portal (PASÉ) of the Mexican Institute of Industrial Property , in the procedures indicated.

<img file="MX360852B_D0001.tif" />

DIVISIONAL DIRECTOR OF PATENTS NAHANNY CANAL REYES p »l Original Chain:

NAHANNY MARISOL CANAL REYES100001000000403252793 Tax Administration Service | 1695 |: | MX / 2019. / 3239 | MX / a / 2014/012716 | Patent title PCT | 1223 | GAGV | Page (s) | GWdfWSV83S31 H2AY¡bAccOp + I

Digital stamp:

fqRaYbawOxpOdvR: NJah: NXh9U: NNnQQh200BXirJ3zaUJAZ3eYgpknlOatW4DG + aTGDTc49NER: H2 / 2birJ5YAUPJccxgn djJwPyDrul1Q / 7vbiPeOreCdsYM1QYiKiMiEgHd63 / Ek5plFu139QZ9G1kNLUvK / w5wWnWgQQpgKE: NTv7KcBMz8DfOkRy7 aCdDk5A2Ac¡dtce + YSoASYr31Ws1: NaBjr + F / 3Fc / KXInGQ1FD2SN1sXXHqi6FLvmh2TXwuqOYgjSThXRirOBJ:! B7SGpS hyzNa8xjTvQC6WjA5W + rym SOW / OiT5sUcfl8ufEF3qk8x3shHierHh38Hlx33N3lnKJE IQ ==

Arenal No. 550, Floor 1, Pueblo Sarita Mana Tepepan, Xochimiíco, 1: 6020,

CiudaP de México, (55) 63340700 www.gob..rnxftrnpi

MX / 2019/3239

TMPW

METHODS AND SYSTEMS TO MEASURE ΙΑ I

OF HOSES

Technical Camiao

The present disclosure relates to methods and systems for measuring hose resistance, for example for detecting hose failure.

Background

High pressure, reinforced hydraulic hoses are typically used in a variety of fluid energy operated machines, such as excavator machines, to provide a flexible connection between various moving parts of a hydraulic circuit employed on or within the machine. Such hoses may include a hollow polymeric inner tube, in which successive cylindrical layers of reinforcing material, such as wire or textile material, are applied concentrically to contain the radial and axial pressures developed within the inner tube.

Many applications are demanding hose constructions with both high burst resistance and long-term fatigue resistance. Using conventional technology, the burst resistance of a hose design can be increased by adding reinforcing material and / or additional layers, a practice that is generally discouraged due to its negative impact on the flexibility of the hose, or universally increase the tensile strength of each layer of reinforcing material, which can be done at the expense of the fatigue resistance of the hose.

To determine the robustness of a hose design, a hose manufacturer typically performs, among other tests, an impulse test and a burst test on the hose. An impulse test measures the fatigue failure resistance of a hose design by cyclically submitting the hose to hydraulic pressure. On the other hand, a burst test is a destructive hydraulic test used to determine the final resistance of a hose by uniformly increasing the internal pressure until failure. Based on these and other tests, a manufacturer can estimate a hose life that can be used to determine when a hose has reached the end of its life and may require replacement.

In some circumstances, it is desirable to detect, in a non-destructive and non-disruptive manner, the possibility of failure of a hydraulic hose. A solution that provides this capability is discussed in US Patent 7,555,936, and discloses connecting a monitor circuit between two at least partially conductive, parallel layers of a hose wall. A change in an electrical property observed by that monitor circuit may indicate a change in a property of the wall structure of

-3 hose, which may indicate a future failure of the hose wall. However, even with this solution, it can be difficult to determine if the changed electrical property is in fact due to a change in a physical characteristic of a hose wall, or if the changed electrical property is due to a change in detection electronics. , a change in an electrical property of a harness that connects the monitor circuit to the hose wall, or simply the degradation of an electrical connection to the hose wall. In these cases, there may be a change in observed electrical property, even when the integrity of the hose wall is not compromised, but is instead due to a change in position or pressure within the hose. Consequently, existing arrangements may not adequately detect hose degradation or failure, but may instead attribute some other type of change in position or pressure of the hose to degradation or failure. Additionally, it is difficult to determine the type of failure that may (or may not) be occurring.

Compendium

One aspect of the present disclosure relates to a hose degradation monitoring system including a hose assembly including a hose having a first conductive layer and a second conductive layer, and a degradation monitoring circuit configured to detect a hose resistance through layers

-4 'i first and second conductors. The degradation monitoring circuit includes a voltage source electrically connected to the first conductive layer and a resistor electrically connected between the second conductive layer and ground. The degradation monitoring circuit also includes a voltage monitoring circuit electrically connected at one location between the resistor and the second conducting layer, the voltage monitoring circuit configured to periodically monitor a voltage at the location and detect possible assembly failure of hose by determining that, based at least in part on a change in voltage rather than time, A resistance in the hose assembly has passed a threshold level.

A second aspect of the present disclosure relates to a method of monitoring the degradation of a hose assembly having first and second conductive layers separated by an insulating layer. The method includes applying a voltage to the first conductive layer and measuring a voltage and current through a resistor connected between the second conductive layer and ground. The method also includes determining a resistance attributable to the hose assembly based on the voltage and current measured across the resistor, and comparing the resistance with a threshold resistance value. The method further includes, based at least in part on a determination that the resistance falls below the resistance of

-5th threshold, generate an indication of degradation of the hose assembly.

A third aspect of the present disclosure relates to a method of detecting a type of failure of a hose assembly. The method includes periodically applying a voltage to a first conductive layer of a hose assembly including first and second conducting layers, and by applying the voltage to the first conductive layer, measuring a voltage and current through a resistor connected between the second conductive layer and earth. The method includes determining a resistance attributable to the hose assembly based, at least in part, on the voltage measured between the second conductive layer and ground, and calculating an admittance of the hose assembly from each resistance. The method further includes, based, at least in part, on changes in the calculated admittance of the hose assembly, determining the existence of a failure in the hose assembly.

Brief Description of Drawings

FIG. 1 is a partial cross-sectional view of an exemplary hose assembly employing a fault detector having exemplary features of aspects in accordance with the principles of the present disclosure;

Figure 2 is a perspective view, partially cut away, illustrating an example hose employing a braided conductive layer which is suitable for use with the assembly of

-6 hose of figure 1;

Figure 3 is a perspective view, partially cut away, illustrating an example hose employing a conductive layer of spiral wire that is suitable for use with the hose assembly of Figure 1;

Figure 4 is a generalized schematic view of a monitoring circuit usable with the hose assembly of Figures 1-3 to provide adaptive scaling of a hose resistance measurement to detect failure or degradation of a hose assembly, of in accordance with a possible embodiment of the present disclosure;

Figure 5 is a graph illustrating a first set of experimental results indicating a range of associated voltages and resistive values ​​observed when using the monitoring circuit illustrated in Figure 4;

Figure 6 is a graph illustrating a second set of experimental results indicating a range of voltages and associated resistive values ​​observed when using the monitoring circuit illustrated in Figure 4;

Figure 7 is a generalized schematic view of a monitoring circuit usable with the hose assembly of Figures 1-3 to provide adaptive scaling of a hose resistance measurement to detect failure or degradation of a hose assembly, of

-7 * i in accordance with a second possible embodiment of the present disclosure;

Figure 8 is a logarithmic scale graph illustrating voltage and resistance values ​​in a circuit such as that shown in Figure 4;

FIG. 9 is a flow chart of a method for monitoring degradation of a hose assembly, according to an example embodiment;

Figure 10 is a schematic view of a hose assembly of Figures 1-3 as a set of parallel admits, in accordance with a possible embodiment of the present disclosure;

<td></td><td>the</td><td>figure 11 is</td><td>a</td><td>schematic view of</td><td>Assemble</td><td>of</td>

<td>hose</td><td>of</td><td>the figure</td><td> 10</td><td colspan="2">including an internal failure</td><td>of</td>

<td>hose;</td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td>the</td><td>figure 12 is</td><td>a</td><td>schematic view of</td><td>Assemble</td><td>of</td>

<td>hose</td><td>of</td><td>the figure</td><td> 10</td><td>with external pressure</td><td>applied</td><td>to the</td>

hose assembly at a particular location, according to an example embodiment;

Figure 13 is a schematic view of the hose assembly of Figure 10 in the event of a detachment failure at a particular location, according to an example embodiment;

Figure 14 is a graph illustrating the rate of change of admittance based on internal layer failure and

-8external in a hose assembly, according to an example embodiment.

Detailed description

Reference will now be made in detail to the exemplary aspects of the present disclosure which are illustrated in the accompanying drawings. Whenever possible, the same reference numbers will be used throughout all drawings to refer to the same or similar structure.

In general, the present disclosure generally relates to methods and systems for measuring hose resistance, for example for detecting hose failure. In various embodiments discussed below in relation to the associated drawings, resistance measurements, and other relative measurements, are taken in relation to a particular hose having two or more conductive layers. Methods of scaling those measurements to detect when hose failures are about to occur or have occurred are also disclosed, in which circuits are implemented that can determine various types of errors based on analysis of the rate of change of electrical characteristics. of the hose. Using the methods and systems discussed herein, various types of hose failure and degradation can be detected and distinguished from each other.

Referring now to Figure 1, an example hose failure detection system is shown, designated

-9 'iii i 1 I generally 10. Hose failure detection system 10 includes a hose assembly, generally designated 12, and optionally a monitoring assembly 14 in electrical and physical communication with hose assembly 12.

Hose assembly 12 includes a hose, generally designated 16, having a multi-layered construction. In the present embodiment, hose 16 is generally flexible and includes an inner tube 18 made of a polymeric material, such as rubber or plastic, or another material, depending on the requirements of the particular application, a first conductive layer 20, an intermediate layer 22, a second conductive layer 24, and an outer covering 26. The first and second conductive layers 20, 24 define an electrical characteristic of the hose assembly 12, such as capacitance, inductance, and / or resistance (impedance).

In the present embodiment, the first conductive layer 20 covers the inner tube 18 and the intermediate layer 22 covers the first conductive layer 20. The second conductive layer 24 covers the intermediate layer 22. The first and second conductive layers 20, 24 can be configured as reinforcing layers. Outer jacket 26 may cover second conductive layer 24, and may include, for example, an extruded rubber or plastic layer. The outer cover 26 may itself include a reinforcing layer.

Intermediate layer 22 operates to at least insulate

Partially electrically the first and second conductive layers 20, 24 with each other. Intermediate layer 22 can have any of a variety of constructions. For example, the intermediate layer 22 may consist of a single layer of an electrically resistive material. Intermediate layer 22 may also consist of multiple layers, where at least one of the layers exhibits electrical insulating properties. Certain composite materials can also be employed in intermediate layer 22, such as a woven fabric bonded to a polymeric material. Composite materials having various other constructions can also be used. Composite materials can also be used in combination with other materials to form intermediate layer 22.

The first and second conductive layers 20, 24 generally extend the entire length and span the entire circumference of the hose. This is generally the case when the conductive layer also functions as a reinforcing layer. The intermediate layer 22 can also extend over the entire length and circumference of the hose. However, there may be cases where at least one of the first and second conductive layers 20, 24 extends only over a portion of the length of the hose and / or a portion of its circumference. In that case, the intermediate layer 22 can also be configured to extend generally over the region of the hose containing the partial conductive layer 20, 24. The

-11 partial intermediate layer 22 can be placed inside the hose so as to separate the first and second conductive layers 20, 24 from each other.

Referring now to Figures 2 and 3, the first and second conductive layers 20, 24 may include, for example, an electrically conductive braided reinforcing material, such as that shown in Figure 2, or alternating layers of reinforcing material electrically conductive coil as shown in figure 3. The braided reinforcing material may consist of a single layer or may include multiple layers. Although a two wire spiral reinforcing arrangement is outlined in Figure 3, it will also be appreciated that other configurations, such as four and six wire arrangements, may also be used.

The first and second conductive layers 20, 24 can each have the same configuration, or each layer can be configured differently. For example, the first and second conductive layers 20, 24 may each include the braided material shown in Figure 2, or one of the first and second conductive layers 20, 24 may include the braided material while the other layer First and second conductive layers 20, 24 can include the spiral reinforcing material shown in Figure 3. Additionally, the first and second conductive layers 20, 24 can include a single layer or multiple layers of reinforcing material. The first conductive layers and

-12second 20, 24 may comprise metal wire, natural or synthetic fibers and textiles, and other reinforcing materials, provided that the selected material is electrically conductive.

Referring again to Figure 1, hose assembly 12 may include a hose attachment, generally designated 30, for fluidly coupling hose 16 to another component. Hose attachment 30 can have any of a variety of different configurations, depending, at least in part, on the requirements of the particular application.

In the present embodiment, the hose attachment 30 includes a threaded nipple, generally designated 32, that links the inside of the hose 16, and a pin, generally designated 34, that links the outside of the hose 16. The threaded nipple 32 includes an elongated cylindrical end portion 36 linking the inner tube 18 of the hose 16. A cylindrical end portion 38 of the plug 34 links the outer cover of the hose 16. Pin 34 and threaded nozzle 32 can be constructed of an electrically conductive material.

The pin 34 and the threaded nozzle 32 can be secured to the hose 16 by crimping the end portion 38 of the pin 34 covering the hose 16. The crimping process deforms the end portion 38 of the pin 34, thereby

-13 'i í s ί 1 I compressing the hose 16 between the threaded nozzle 32 and the pin 34. In the present embodiment, the portions of the threaded nozzle 32 and the pin 34 that link the hose 16 include a series of Jagged edges that at least partially attach to the relatively softer hose material when pin 34 is crimped to help secure hose attachment 30 to hose 16. The serrated edges can also be configured to prevent the serrated edges from penetrating the inner tube and outer jacket and contacting the first and second conductive layers 20, 24.

In the present embodiment, pin 34 includes an inwardly extending circumferential lug 40 positioned near one end 42 of pin 34 adjacent an end 44 of hose 16. Lug 40 links a corresponding circumferential groove 46 formed into threaded nipple 32 to hold pin 34 in threaded nipple 32. The end 42 of the pin 34 having the lug 40 is initially formed larger than the threaded nozzle 32 to allow the pin 34 to be assembled into the threaded nozzle 32. During the assembly process, the end 42 of the pin 34 is crimped, which deforms pin 34 and forces lug 40 into engagement with corresponding slot 46 in threaded nipple 32. Pin 34 can be electrically isolated from threaded nozzle 32 by placing an electrically insulating collar

-14 'i between the pin 34 and the nozzle 32 at the point where the lug 40 links the slot 46.

Hose attachment 30 also includes a nut 50 rotatably attached to nozzle 32. Nut 50 provides means to secure hose assembly 12 to another component.

The first conductive layer 20 can be configured to extend beyond the end of the inner tube of the hose 16. The first conductive layer 20 can link the threaded nozzle 32 to create an electrical connection between the threaded nozzle 32 and the first conductive layer 20. Similarly, the second conductive layer 24 can be configured to extend beyond one end of the outer covering of the hose 16. The second conductive layer 24 can link pin 34 to create an electrical connection between pin 34 and second conductive layer 24.

To help prevent portions of the first and second conductive layers 20, 24, extending beyond the end of the hose 16, from contacting each other, an electrically insulating spacer 52 may be placed between the exposed ends of the first conductive layers and second 20, 24. Spacer 52 can be integrally formed as part of collar 48 used to electrically isolate pin 34 from threaded nozzle 32. The separator 52 can also be formed by extending the intermediate layer 22 of the hose 16 plus

-15 'i beyond one end of inner tube 18 and outer jacket 26. Separator 52 can also be configured as a single component, separate from collar 48 and intermediate layer 22 of hose 16.

Monitoring assembly 14 can have any of a variety of configurations. In general, the monitoring assembly 14 is capable of connecting over a portion of the hose assembly 12, in particular the portion illustrated in Figure 1. Monitoring assembly 14, when installed on hose assembly 12, forms a physical and electrical connection with hose assembly 12, and in particular with threaded nipple 32 and plug 34, respectively. In some embodiments, the monitoring assembly 14 includes a monitoring circuit, such as those described below. Generally, the monitoring assembly 14 detects an electrical characteristic of the hose assembly 12, while validating the connection with the threaded nipple 32 and the plug 34. An example monitoring assembly 14 is described in greater detail below, in relation to the Figures 4-9.

Referring now to Figures 4-9, systems and methods for monitoring a hose assembly are illustrated, including circuits that can be included in a monitoring assembly 14 as described above in relation to Figure 1. Figure 4 is a schematic view of

-16 a monitoring circuit 100 that can be used within a monitoring assembly 14. The monitoring circuit includes a voltage source 102 and ground 104, as well as a resistor 106 (marked R_scalar). In this embodiment, the voltage source 102 is connected to a first conductive layer 102 of a hose assembly 110 having first and second conductive layers 112, 114 (e.g., corresponding to layers 20, 24) via a exposed connection location (e.g., threaded nipple 32 and pin 34). The second conductive layer 144 is then electrically connected to the resistor

106, which in turn is connected to ground 104. In some embodiments, such as that shown in FIG. 8 below, the voltage source 102 is a known constant direct current voltage, referred to as V_ref. For example, voltage source 102 and ground 104 can represent opposite ends of a battery, which can be selectively applied through the hose assembly.

To monitor the hose assembly, the voltage and current passing through circuit 100 can be measured. In the shown embodiment, a voltage (V_analog) 120 is measured by a voltage monitoring circuit. Voltage 120 represents a voltage divider between hose assembly 110 and resistor 106. By determining the voltage and current at this location within the circuit, it is possible to determine an overall resistance of the circuit (based on a voltage

-17 known global, V_ref). This can be done using variations in a voltage divider equation, as follows:

^ analog ^— V_ref X (Rsource / Rhose + Rsource)

In various embodiments of the present disclosure, different values ​​can be used for voltage source 102 and resistor 106. However, it is generally recognized that while a good hose may have a widely varying resistance (Rhose), a hose Failure will have a reduced resistance value. For example, a good or newly manufactured hose can have a resistance anywhere from about 10 k Ohms to about 1 M Ohms. Thus, in some embodiments, it may be advantageous to select a value for resistor 106 that maximizes a change in voltage 120 for changes in resistance of hose assembly 110 to relatively low resistance values, to ensure that even small changes in The resistance of the hose assembly is detected. Additionally, as the resistance of the hose decreases, any current passing through circuit 100 will increase, as illustrated in the following current equation:

1-circuit V_xef / (Rhose + Scalar)

Consequently, it would be advantageous, from an energy saving perspective, to maintain a relatively high resistance, to ensure that even in the worst case scenario (i.e. a short circuit formed between layers of the hose), the

-18 'i maximum current passing through circuit 100 would be ^ ref / ^ scalar

Referring now to Figures 5-6, and continuing the discussion of circuit values ​​in monitoring circuit 100, graphs illustrating a voltage-resistance relationship are illustrated using examples at opposite ends of the spectrum of the expected resistances of the assembly of hose. In Figure 5, a graph 200 is shown illustrating the voltage-resistance relationship in an example of low resistance. In this example, a good hose assembly tested in this arrangement is determined to have a resistance R_hoseinitial 5 kilo Ohms. In this arrangement, a 400 Ohm resistor is selected as resistor 106, and a reference voltage of 3 volts is selected for voltage source 102. Because it has been empirically determined that a faulty hose typically has a resistance below around 100 Ohms, when a hose degrades and eventually fails, the hose resistance R_hose will drop, causing voltage 120 to rise as scalar resistor 106 begins (R_scaiar) ^tomaster the voltage divider equation. Thus, for resistance less than around 100 Ohms, the voltage V_analog will rise to around 80% or more of the total voltage provided by the voltage source V_ref. However, during normal operation, the hose resistance will remain high, maintaining the voltage 120 V_analog at a low proportion of the source voltage

-19 * i í 1 ί i global 102 V_ref.

In Figure 6, a graph 300 illustrates the voltage-resistance relationship in an example of high resistance. In this example, a good hose assembly tested in this arrangement is determined to have a resistance R_hose initial 1 mega Ohm. In this arrangement, the 400 Ohm resistor is again selected as resistor 106, and a reference voltage of 3 volts is selected for voltage source 102. Again, because it has been empirically determined that a faulty hose typically has a resistance less than about 100 Ohms, as a hose degrades and eventually fails, the voltage V_analog will rise to around 80% or more of the total voltage provided by the voltage source V_ref in the event of a hose assembly failure.

In alternative arrangements, for example, if hose failures are determined to result in a higher observed resistive value, a larger value can be used for resistor 106 in circuit 100. Altering the value of the resistor

106, it is possible to alter the threshold at which hose degradation or feasible failure can be detected. For example, the use of a larger resistor 106 may allow increased sensitivity to changes in hose resistance near that larger value. 0, if the resistance of the hose can drop well below 100 Ohms without affecting the continuity or operation of the hose, an additional 106 resistor can be used

-20 small. However, it will be understood that in the case of a smaller resistor, higher currents will be experienced. For example, in an extreme case of hose failure (i.e. a hose having a resistance less than about 100 Ohms), the largest resistance would be around 0.75 mA, a more typical value would be around 0.6 mA at the point of failure.

Referring now to Figure 7, an alternative monitoring circuit 400 is illustrated, which can be used to detect degradation or failure in a hose assembly, such as that shown in Figures 1-3 above. The monitoring circuit 400 in this embodiment is configured to be connected to a data acquisition device, such as a microprocessor or microcontroller, which can be used to monitor and track voltage and current measurements over time to determine a typical degradation of a hose over time. In this embodiment, circuit 400 includes a voltage source, shown as a battery 402 (V_bat). As with circuit 100 illustrated in Figure 4, circuit 40G includes a scalar resistor 404 (R_scaiar) · In this embodiment, the hose assembly is modeled as a set of parallel resistors, which combine to form a hose resistor 406 (R_hose) equivalent. The data access points 408a-c allow a remote data acquisition system (not shown) to monitor a positive voltage level (at data access point 408a), an analog voltage point at V_meas (at data access point 408b) and a local ground (at data access point 408c). Using the differences between the signal levels at each point, it is possible to monitor a relationship between the voltage across the entire circuit (V_bat) and the voltage drop across resistor 404, as well as the current passing through circuit (I) to determine the hose resistance (R_hose) .

Optionally, circuit 400 may also include a switch controllable by the data acquisition system or a remote system to periodically connect battery 402 to the rest of circuit 400, thereby limiting the amount of time the global circuit is connected and limiting the battery discharge rate.

The data acquisition device can take any of a variety of forms, and can include a voltage monitoring circuit to determine a voltage V_meas. The data acquisition device may be a programmable circuit integrated with circuit 400, or a separate / remote computing system. Such a device may include, for example, one or more programmable circuits that have general-purpose analog input / output connections.

Referring now to FIG. 8, an example graph 500 of the results of a test of the

-22 circuit illustrated in figure 7. In graph 500, a relationship between the hose resistance (R_hose) and the measurement voltage (V ^ J. The 500 graph was developed using a 6.33 volt voltage source and a 12.85 k Ohm scalar resistor during any given test to provide acceptable battery life, and to plot a graph voltage V_measversus hose resistance R_hose. In this example, it can be seen that as the resistance of the hose decreases, the measured voltage increases at a constant rate until the hose resistance approaches the scalar resistance, at which time small changes in the hose resistance give as smaller changes in voltage result, meaning that the effect of the scalar resistor R_scalar dominates the voltage divider circuit.

Referring now to FIG. 9, a flow chart of a method 600 for monitoring degradation of a hose assembly is shown, in accordance with an example embodiment. Method 600 can be carried out periodically, for example using a programmable circuit or other computer system or data acquisition device interfaced with a monitoring circuit such as those shown in Figures 4 and 7.

Method 600 includes applying voltage to a monitoring circuit, for example applying a battery through a monitoring circuit as illustrated in Figure 7 (step

-23602). The method includes measuring a voltage at a position between the hose assembly and a scalar resistor, as well as optionally determining a current through the global circuit (step 604). The method optionally includes determining a resistance attributable to the hose assembly (step 606), and comparing that resistance to a predetermined threshold resistance, below which the hose is assumed to have degraded or failed (step 608). If the resistance is not below the threshold resistance, method 600 includes periodically repeating this monitoring process. However, if the resistance is below the threshold resistance, this may be due to a variance in operating conditions or another temporary event. Accordingly, a history tracing operation takes place to determine if a sufficient number of comparisons between the hose resistance and the predetermined threshold resistance indicates that the condition is not temporary, but instead represents a current state of the hose (step 610). In example embodiments, this may take place within a microcontroller or other data acquisition device. If such a predetermined number of measurements has not yet occurred, the operation returns to step 602 for continued monitoring of the hose assembly on a periodic basis. If that number of measurements has taken place, an alert or other indication of hose assembly degradation may be generated (step 612), and optionally reported to

-24 a system remotely or locally to notify a user that the hose should be replaced.

Referring generally to the methods and systems of Figures 4-9, it can be appreciated that using a carefully selected scaling mechanism, including a scaling resistor, it is possible to ensure that in the range of hose resistances where faults are expected, even Small changes in resistance will result in relatively large changes in voltage, causing this to directly detect degradation of a hose. Further, using the methods and systems described in Figures 4-9, various types of degradation can be detected, as discussed below.

Referring now to Figures 10-13, schematic models of a hose assembly are shown, along with exemplary ways in which such hose assemblies typically fail. It is recognized that by detecting changes in hose characteristics using a modification of the above resistive measurements, different types of hose failure can be detected (e.g., internal failure versus external failure) and distinguished from each other, for example using periodic resistance measurements discussed above with respect to Figures 4-9.

FIG. 10 illustrates an example schematic of a segment of a hose assembly 700 including layers.

-25 inner and outer conductors 710, 720. When a potential difference is applied across the conductive layers 710, 720, the hose assembly will exhibit some resistance, as described above. However, as further described above, the resistance that appears to be the single resistance that the hose represents overall can in fact also be represented as several parallel resistors and associated capacitances. Consequently, if those parallel resistors are viewed in terms of conductance per unit length, that conductance can be determined between layers 710, 720, is known, and can be represented as:

G = kl / (ln r_or - ln r_±)

Similarly, the capacitance per unit length of the hose assembly can be represented as:

C = k2 / (ln r_or - ln rj

In these equations, kl and k2 are constants that can be determined and can vary based on the exact materials from which the hose assembly is constructed. And r_or yr_±are the outer and inner radii of the hose assembly.

To consider both conductance and capacitance on a unit basis as an added effect, the hose can be viewed as having an admittance and per unit length. As shown in FIG. 10, each unit of length of hose assembly 700 has an admittance y ^ n associated with it. Each local admittance value can be

-2610 * i í 1 ii expressed as:

yi = length * k (ln r_or - ln p¡

A total admittance can be calculated or modeled as the sum of each of these local admittances.

During normal hose operation, similar to the resistance discussed above, it will remain constant over time. However, the characteristics of the hose will change over time. This can be modeled either as a failure of the inner conductive layer (eg, in the case of pressure within the hose that weakens the hose from the inner walls to the outside), or failure of the outer conductive layer (v .gr., due to compression or detachment, where a portion of the hose is worn or torn). Figures 11-13 represent these different scenarios.

Figure 11 illustrates a schematic change to hose assembly 700 in the event of a localized internal failure. In that case, an internal failure results in an increase in radius r_± of the inner layer 710 at the point of failure. This results in the distance between the inner layer 710 r_TO and the outer layer 720 r₀ is reduced at that point. Consequently, the local admittance at that point, and hence the total admittance of the hose assembly, increases.

FIG. 12 illustrates a change in the schematic of the hose assembly 700 in the case of a localized change in the outer layer 720, for example in the case of an object that

-27 'i presses against the outer layer 720. In this case, the outer layer 720 is compressed towards the inner layer 710 in the place of compression. This results in an increase in capacitance and conductance, due to narrowing in the wide area. Because an internal point of failure, as shown in Figure 11, is typically in a much more localized position along the hose assembly than a compression of the hose assembly, the change in overall admittance in the case of Compression is much greater than the change in global admittance in the case of external compression of the hose will exceed the global admittance of the hose, making the two scenarios easily distinguishable. As illustrated in Figure 12, the compression in admittances per unit length and₂ and Y3 will cause a higher admittance due to the substantially smaller external radius through this latter area.

Figure 13 illustrates a change in the schematic of the hose assembly 700 in the case of a localized removal of the outer layer 720, for example in the case of a detachment of a portion of the outer shield from the hose assembly 700. This may occur, for example, due to friction in a hose or cut through a portion of the outer layers of the hose assembly. As illustrated in this example, the outer layer 720 in the admits and₂ yy₃ per unit length it is completely removed due to detachment. As such, admittance in this area essentially

-28 'is 1 ί

returns zero. Consequently, the added admittance will be reduced compared to an original value. This allows the peel effect to be distinguishable as a function of global admittance compared to either internal failure (in Figure 11) or compression (in Figure 12), because in both cases the admittance is increased .

It can be seen that, based on the admittance changes described above, it is possible to trace occurrences in a particular hose assembly. For example, a pronounced increase in admittance, followed by a decrease, would represent a compressed hose that results in a detach condition. Additionally, it is possible to determine, based on the timing of the admittance changes, whether a failure involves only an internal failure, an external failure, or both. Of course, in such circumstances a total admittance must be relatively well defined (to be able to distinguish types of admittance changes); In such circumstances, careful hose construction may be required.

Referring now to Figure 14, a graph 800 is shown illustrating the rate of change and the magnitude of change of admittance based on inner and outer layer failures in a hose assembly, in accordance with one embodiment. of example. As illustrated in this graph 800, the cumulative admittance of the hose changes dramatically in shape.

-29 fast and more effective based on changes in outer radius (i.e. outer layer 720) compared to inner radius (i.e. inner layer 710). These rate changes can be seen in graph 800, and are also represented by the following equations:

dy / ori = k / (lní ^ / rj² rj óy / or0 = k / (ln (ro / rj² ro)

As such, the admittance exchange rate is slower when r_x increases and r₀ remains fixed, more than when r₀ is increased and ri is fixed. Additionally, and as shown in graph 800, the changes in both r_or how r_TO they will be additive, resulting in even higher exchange rates. Consequently, changes in admittance over a threshold value can be determined by ester based on an effect on the outer layer, allowing distinction between failure types, and occurrences when both failure types can occur simultaneously.

Referring to Figures 10-14, it is observed that, although in the illustrated embodiments the admittance is calculated based on measured resistances and as a function of certain characteristics of the hose, it is observed that in some additional embodiments, the capacitive effects of the hose can also be taken into account.

The description, examples and data above provide a complete description of the manufacture and use of the

-30 material of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the appended claims hereinafter.