Abstract:
A pressure testing device for calculating a pressure in a flexible line comprises a housing unit, a force sensor mounted on the housing unit and a clamp assembly having a clamp mounted on the housing unit. The clamp is operable to compress the flexible line against the force sensor by a predetermined degree of deformation of the flexible line. The device includes a displacement sensor adapted to measure a displacement of the clamp. The device also includes a controller having a processor in communication with the force sensor and the displacement sensor, and a memory unit containing stored data. At the predetermined degree of deformation of the flexible line, the processor compares a first signal from the force sensor and a second signal from the displacement senor with the stored data to estimate the pressure within the flexible line.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a pressure detection device. In particular, the present invention relates to portable device for detecting the pressure in flexible hydraulic and pneumatic hoses. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are many applications where it is desirable to test or measure the internal pressure within a flexible hydraulic or pneumatic line. This may be for safety purposes, or for other reasons such as accuracy of measurement of flow conditions. 
         [0003]    In both underground and open-cut mining applications hydraulic lines are commonly used on a variety of equipment ranging from jacking and roof bolting equipment to excavating and long wall shearing devices. As such, hydraulic motors, pumps and pistons provide an integral part of most mining environments. In a similar way, hydraulic equipment is widely used by other industries such as forestry, farming and construction. 
         [0004]    At certain stages of operation of hydraulic machinery, it may become necessary to depressurise and decouple a hydraulic line. During such a process it is important that the hydraulic line is firstly depressurised, to reduce the risk of any personnel being injured by the high pressure hydraulic fluid. Despite safety protocols, accidents still occur. The residual pressure in the hydraulic line may still be too high in some instances, even after depressurisation has been attempted. Alternatively, technicians often incorrectly assume that a line has a low pressure or no pressure. 
         [0005]    Previously, hydraulic couplings utilised corresponding male and female threaded members. The threaded couplings meant that when a user believed the hydraulic line to have been depressurised, by slowly unscrewing the thread, the hydraulic fluid would leak immediately after the seal was broken, indicating to the user if the line still contained high pressure fluid. 
         [0006]    However; in newer machinery, hydraulic lines are typically coupled together with snap lock type fittings. Whilst snap lock fittings are fast to connect and disconnect, they also provide the disadvantage of being very dangerous if they are disconnected while the line pressure is still too high. Because the snap lock fitting is fast to disconnect, there are incidents of personnel being injured and killed by the hose whipping around, and either striking a person, or spraying the person with hydraulic fluid which may be at very high pressures, and temperatures. 
         [0007]    There are known invasive devices for testing the pressure in a hydraulic line. These devices include deadweight pressure testers, pressure transducers and hydraulic multi-meters. However, these devices are all invasive and as such require connection to the hydraulic line through valves, ports and other means. A disadvantage with these devices is that they are not portable and only provide a pressure reading at a given location in the hydraulic circuit. A further disadvantage is that it is not always possible to connect an invasive testing device to a hydraulic circuit. For example, in a complex hydraulic circuit with long lines, not all lines are provided with a test point to allow pressure measurement. 
         [0008]    There are known non-invasive devices for testing fluid flow at a specific point in a hydraulic line. Examples of such devices include strain gauges which require prior installation into the line and calibration. A disadvantage of using such devices is that they often do not provide a sufficient degree of precision, and they tend to be expensive and complex to operate. 
         [0009]    Other fluid pressure testing devices include metal discs moving within the electromagnetic field of an energised coil to sense pressure changes. Such devices generally use a test chamber separated into two parts by a flexible diaphragm. However, these devices are intended for medical applications and other such uses where the fluid pressure in the line is relatively small. 
       OBJECT OF THE INVENTION 
       [0010]    It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or to provide a useful alternative. 
       SUMMARY OF THE INVENTION 
       [0011]    In a first aspect, the present invention provides a pressure testing device for calculating a pressure in a flexible line, the device comprising: 
         [0012]    a housing unit; 
         [0013]    a force sensor mounted on the housing unit; 
         [0014]    a clamp assembly having a clamp mounted on the housing unit, the clamp being operable to compress the flexible line against the force sensor by a predetermined degree of deformation of the flexible line; 
         [0015]    a displacement sensor adapted to measure a displacement of the clamp; and 
         [0016]    a controller having:
       i) a processor in communication with the force sensor and the displacement sensor;   ii) a memory unit containing stored data;       
 
         [0019]    wherein at the predetermined degree of deformation of the flexible line, the processor compares a first signal from the force sensor and a second signal from the displacement senor with the stored data to estimate the pressure within the flexible line. 
         [0020]    The pressure testing device preferably further includes an output device, wherein the controller is adapted to send an output signal to the output device based on an estimated pressure within the flexible line. 
         [0021]    The output device preferably provides a first output corresponding to a low pressure, a second output corresponding to a high pressure, and a third output corresponding to an error, indicating that retesting is required. 
         [0022]    The force sensor preferably includes a probe coupled with a transducer. 
         [0023]    The transducer is preferably a piezoelectric transducer. 
         [0024]    The transducer is preferably in communication with an amplifier which converts an electric charge into an electric signal, proportional to a force applied to the probe. 
         [0025]    The amplifier is preferably in communication with the controller. 
         [0026]    The displacement sensor preferably includes a linear potentiometer. 
         [0027]    The linear potentiometer preferably includes a body mounted on the housing unit, and a sliding arm in engagement with a moving portion of the clamp. 
         [0028]    The linear potentiometer preferably acts as a voltage divider to measure the distance between clamp and the probe. 
         [0029]    The predetermined degree of deformation of the flexible line is preferably about  10  percent of the outer diameter of the flexible line. 
         [0030]    The damp assembly preferably includes: 
         [0031]    a shaft having proximal and distal ends; 
         [0032]    a handle connected to the proximal end; and 
         [0033]    a clamp plate connected to the distal end, 
         [0034]    wherein the handle is rotatable to selectively vary the distance between the clamp plate and the force sensor. 
         [0035]    The shaft preferably includes a primary shaft and a secondary shaft, the primary shaft extending between the handle and a puller block, and the secondary shaft extending between the puller block and the clamp plate. 
         [0036]    The primary shaft is preferably threadingly connected to the puller block such that rotation of the handle causes the puller black to move longitudinally within the housing unit. 
         [0037]    The sliding arm is preferably in engagement with the puller block. 
         [0038]    The pressure testing device further preferably comprises a micro-switch in contact with the puller block, the micro-switch being adapted to turn on the device when the puller block moves longitudinally. 
         [0039]    The pressure testing device preferably further comprises a second force sensor mounted on the housing unit. 
         [0040]    The second force sensor is preferably a resistive strain sensor. 
         [0041]    In a second aspect, the present invention provides a pressure testing device for estimating a pressure within a flexible line, the device comprising: 
         [0042]    a clamp, adapted to compress the flexible line; 
         [0043]    a displacement sensor adapted to measure an outer diameter of the flexible line and output a stop signal when the outer diameter of the flexible line has been compressed by a predetermined percentage; 
         [0044]    a force sensor adapted to measure a force applied by the clamp against an outer wall of the flexible line and output a force signal; 
         [0045]    a processor adapted to compare the force signal with a database of values to estimate whether an internal pressure is safe or unsafe; and 
         [0046]    a display in communication with the processor and adapted to provide an indication of safe or unsafe internal pressure. 
         [0047]    In a third aspect, the present invention provides a pressure testing device for estimating a pressure within a flexible line, the device comprising: 
         [0048]    a clamp, adapted to compress the flexible line; 
         [0049]    a displacement sensor adapted to measure a change in outer diameter of the flexible line and output a displacement signal; 
         [0050]    a force sensor adapted to measure a force acting on an outer wall of the, flexible line and output a force signal; 
         [0051]    a processor adapted to compare the force signal and the displacement signal with a database of stored values to estimate an internal pressure within the flexible line and produce an output. 
         [0052]    In a fourth aspect, the present invention provides a pressure testing device for estimating a pressure within a flexible line, the device comprising: 
         [0053]    a clamp, adapted to compress the flexible line; 
         [0054]    a displacement sensor adapted to measure a change in outer diameter of the flexible line and output a displacement signal; 
         [0055]    a force sensor adapted to measure a force acting on an outer wall of the flexible line and output a force signal; 
         [0056]    wherein the force sensor and the displacement sensor are in communication with a processor adapted to compare the force signal and the displacement signal with a database of stored values to estimate an internal pressure within the flexible line and produce an output. 
         [0057]    In a fifth aspect, the present invention provides a method of calculating a pressure in a flexible line, the method including the steps of: 
         [0058]    calculating an outer diameter of the flexible line with a displacement sensor; compressing the line with a clamp against a force sensor by a predetermined degree of deformation of the flexible line; 
         [0059]    sending a first force signal from the force sensor to a controller; 
         [0060]    sending a second displacement signal from the displacement sensor to the controller; 
         [0061]    comparing the first force signal and the second displacement signal with stored data to estimate the pressure within the flexible line. 
         [0062]    The step of compressing the line preferably includes a user manually actuating the clamp. 
         [0063]    The method preferably further includes the step of sending an output to the user to indicate when the predetermined degree of deformation has occurred. 
         [0064]    The predetermined degree of deformation is preferably about  10  percent of the outer diameter of the flexible line. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0065]    A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which: 
           [0066]      FIG. 1  is an exploded assembly view of a portable pressure detection device; 
           [0067]      FIG. 2  is a flow diagram showing a pressure testing process; 
           [0068]      FIG. 3  is an electrical circuit diagram; and 
           [0069]      FIG. 4  is a schematic view of a portion of a hydraulic line. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0070]    A portable, hand held pressure detection device  10  is depicted in  FIG. 1 . The device  10  includes a manifold or frame  12 . The manifold  12  supports the mechanical and electrical components of the device  10  and is mounted within a rigid casing  14 . The casing  14  can be manufactured from stainless steel, plastic, aluminium or other suitable engineering materials. 
         [0071]    The casing  14  is hand held and portable. The casing  14  has a concave face with respect to the hose clamp that will divert the jet of oil away from the operator in case of an unlikely event of a hose  11  burst. The casing  14  may be made in various sizes to accommodate different sized hydraulic lines  11 . Generally the casing is a hand held unit, which is portable. 
         [0072]    The device  10  includes a handle  16  which is connected to a proximal end  17  of a shaft or screw  18  projecting out of the casing  14 . As depicted in  FIG. 1 , the handle  16  is connected to the screw  18  with a bolted assembly consisting of a threaded bolt  20 , a spring washer  22  and a nut  24 . 
         [0073]    The screw  18  is mounted on the manifold  12  with two thrust washers  26  and two thrust radial bearings  28 . The bearings  28  enable the handle  16  and screw  18  to rotate relative to the manifold  12 . The device  10  includes a puller nut  29  having a threaded connection with the manifold  12 . The puller nut  29  holds the screw  18  in a precise location, while permitting the screw  18  to rotate. 
         [0074]    Two batteries  30  are mounted within the manifold  12  to power the electric components of the device  10 . The batteries  30  are covered with a battery plug  32  with a screwdriver engagement slot  34 . The battery plug  32  secures the batteries  30  in position and protects them from moisture ingression. 
         [0075]    A puller block  40  is mounted within the manifold  12 . The puller block  40  has a first end  42  with a threaded hole for receiving the distal end  19  of the screw  18 . The puller block  40  has a second end  44  with a hole for receiving the proximal end  52  of a clamp shaft  50 . The clamp shaft  50  is secured to the puller block  40  with a pin  46 . The puller block  40  has a generally rectangular cross-sectional profile, and the puller block  40  fits into a corresponding slot  48  formed in the manifold  12 . On account of the engagement between the side walls of the puller block  40  and the manifold  12 , the puller block  40  is prevented from rotating with the screw  18 . Accordingly, when the screw  18  rotates in response to a user turning the handle  16 , the puller block  40  slides within the manifold  12 , along the longitudinal axis XX of the shaft  18 . 
         [0076]    The distal end  54  of the clamp shaft  50  is connected to a clamp plate  60  with a pin  62 . Rotation of the handle  16  causes the puller block  40  to move longitudinally along the axis XX, which in turn results in longitudinal motion of the clamp shaft  50  and the clamp plate  60 . 
         [0077]    On account of the right handed thread of the shaft  18 , clockwise rotation of the handle  16  moves the clamp plate  16  towards the manifold  12 , and anti-clockwise rotation of the handle  16  moves the clamp plate  16  away from the manifold  12 . 
         [0078]    A simplified circuit diagram is shown in  FIG. 3 . The device  10  includes a probe  70  which is seated in a circular hole  72  formed on the manifold  12 , and free to move within the hole  72 , but prevented from passing through the hole  72 , on account of a step change in diameter of the probe  70 . The device  10  includes a screw  71  mounted on the manifold  12  which allows precise movement of the probe  70  between two limits. The mechanical assembly of the device  10  is designed to apply a force on a hydraulic or pneumatic hose or line  11  placed between the clamp plate  60  and the probe  70 . 
         [0079]    The device  10  includes a piezoelectric transducer  100  located in a dedicated slot  102  in the manifold  12 . The piezoelectric, transducer  100  abuts against the probe  70 . The piezoelectric transducer  100  generates an electric potential in response to applied mechanical force on the probe  70 . 
         [0080]    A datalink processor (DLP) plug  110  communicates an electric signal from the piezoelectric transducer  100  to a DLPP board  120 . The DLPP board  120  is an amplifier that converts the electric potential, preferably an electric charge into an electric signal preferably voltage proportional with the force applied by the probe  70  to the piezoelectric transducer  100 . The output of the DLPP board  120  is a first voltage signal between 0 and 5 V DC. 
         [0081]    The device  10  includes a linear potentiometer  90  having a body  92  and a sliding arm  94 . The potentiometer body  92  is secured to the manifold  12  in a slot  96 . The sliding arm  94  of the potentiometer  92  is connected to a recess  98  of the puller block  40 . Accordingly, the sliding arm  94  moves with the puller block  40  when the handle  16  is rotated. 
         [0082]    The linear potentiometer  90  is used as a voltage divider and measures the distance between damp plate  60  and the probe  70 . The output of the linear potentiometer  90  is a second voltage signal. 
         [0083]    The first voltage signal from the DLPP board  120  and the second voltage signal from the potentiometer  90  are connected to a programmable logic controller PLC  122 . The PLC  122  has a stored internal memory or database corresponding to the internal pressure in various hydraulic tubes when a given deformation of the hydraulic tube wall occurs resulting from a given force acting on the tube wall. 
         [0084]    This calculation is possible because, in the case of flexible conduits such as hydraulic and pneumatic hoses, the flexibility and deformability of the hose wall is proportional to the internal pressure within the hose. 
         [0085]    The PLC  122  compares the two voltage signals with pre-recorded values in the internal memory and displays the result on a  7 -segment LED display  130 . The display  130  is protected against water ingress by a lens  132  mounted on the manifold  12 . The LED display  130  may indicate paramaters other than the pressure within the line  11 , such as the diameter of the line  11  or an indication of remaining battery power etc, or other such variables. 
         [0086]    A micro switch  140  having a micro lever  142  is mounted to the manifold  12 . The micro switch  140  powers on and off the device  10  when the puller block  40  comes into contact with the micro lever  142 . 
         [0087]    The electrical power is provided by the batteries  30 . A 24V terminal  150  provides electrical contact to the micro switch  140 . 
         [0088]    The operation of the device  10  will now be described. When a user wishes to test the internal pressure within a hydraulic line  11 , the user places a portion of the line  11  between the probe  70  and the clamp plate  60 . The user then commences to rotate the handle  16  in a clockwise direction, which gradually reduces the distance between the clamp plate  60  and the probe  70 . The movement of the puller block  40  engages the microswitch  140 , causing the device  10  to power on and activating the LED display  130 . 
         [0089]    When the probe  70  and the clamp plate  60  both come into contact with the hose  11 , and the initial force applied to the probe  70  reaches some predetermined level, this indicates to the PLC  120  that the space between the clamp plate  60  and the probe  70  corresponds to the starting, outer diameter of the tube  11 . The PLC  120  then calibrates using a high speed counter or another such means. This is taken to be the starting position for the second voltage signal received by the potentiometer  90 . The segments on the display  130  begin to light up in a clockwise pattern confirming that hose  11 , probe  70  and piezoelectric transducer  100 ′ are in contact and a force exists on the outer wall of the hose  11 . At this moment the outer diameter of the hose  11  is measured by the potentiometer  90  and the value of the signal generated by the potentiometer  90  is stored in the memory of the PLC  122 . A circuit diagram is included as  FIG. 3 . 
         [0090]    The operator continues turning the handle  16  clockwise. The hydraulic hose is deformed between the clamp plate  60  and the probe  70 . When the deformation of the hose reaches 10% of the outside diameter of the hose, the letter “S” is displayed on the LED display  130 . The operator stops turning the handle. The PLC  122  then compares the first voltage signal from the DLPP board  120  and the second voltage signal from the potentiometer  90  with the data stored in the memory. 
         [0091]    If the results of the data comparison indicate that the pressure in the line is safe, such as a pressure of less than 20 Bar, the letter “L” is displayed on the LED display  130  indicating low pressure. When the pressure is calculated to be greater than a safe level, such as more than 20 Bar, the letter “H” is displayed on the LED display  130 , indicating high pressure. 
         [0092]    In the event that the operator does not follow the procedure correctly, or an accurate reading cannot be obtained, or the pressure varies in the hose at the time of measurement around the 20 Bar value. The letter “R” is displayed indicating a repeat of the procedure is required. 
         [0093]    The database of information can be customised to particular brands and types of hose, or simply set to generic hose specifications of a given diameter. The database can be downloaded from a website on a SD card and then placed in the portable device providing a simple automatic upgrade. 
         [0094]    In an alternative embodiment, a magnetic sensor is used instead of the potentiometer  90  to provide accurate measurement of the distance in real time between the clamp plate  60  and the probe  70 . However, it will be appreciated by a person skilled in the art that a different sensor may be used to measure the deformation, such as an angular encoder. 
         [0095]    In an alternative embodiment, a resistive strain sensor may be used instead or in addition to the piezoelectric sensor  90  to provide accurate behaviour of the hose  11  under deformation. However, it will be appreciated by a person skilled in the art that a different PLC  122  will be used. 
         [0096]    Some hoses  11  may become brittle being exposed to high temperature or ultraviolet radiation. In this case the deformation is stopped early in the course of measurement to prevent damaging the hose  11  being tested. This is possible by using two force sensors: one with a very dynamic output as the piezoelectric sensor  90  and one resistive strain sensor with a better static characteristic. The PLC  122  will compare these values (static and dynamic) for a better accuracy and if the dynamic value has a certain behaviour will stop the deformation before it reaches  10 % displaying letter “F”: Faulty Hose  11 . Also having the capability to compare more parameters enables the device  10  to be used on a variety of hydraulic hoses  11  and pneumatic hoses as well without the need of a selector or operator intervention. 
         [0097]    The device  10  may have download port such as a USB port so that information can be transmitted to a computer. Alternatively, the device  10  may utilise a Bluetooth transmitter or RFID to communicate with a computer. In this embodiment, the raw data concerning pressure and displacement may be provided to a remote computer such as a laptop computer. The laptop computer may be provided with software to estimate the internal pressure within the hydraulic hose  11 , and the ability for a user to specify the hose type and other parameters. Alternatively, an updated data table may be downloaded from a computer through the download port, to accommodate different data for different hydraulic lines  11 , or new data. 
         [0098]    It will be appreciated by those skilled in the art that the clamp plate  60  may be driven by other means such as a hydraulic pump, or ratchet mechanism. 
         [0099]    Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.