Patent Application
20120132043
The present invention relates generally to mechanical torque wrenches. More particularly, the present invention relates to a ratcheting mechanical clicker type torque wrench and a sensor for determining an amount of angular rotation of the torque wrench.
Often, fasteners used to assemble performance critical components are tightened to a specified torque level to introduce a “pretension” in the fastener. As torque is applied to the head of the fastener, the fastener may begin to stretch beyond a certain level of applied torque. The stretching results in pretension in the fastener which then holds the joint together. Additionally, it is often necessary to further rotate the fastener through a specified angle after the desired torque level is applied. Over-stressing fasteners can lead to their failure whereas under-stressing can lead to joint failure, leakage, etc. Furthermore, in situations where gaskets are being utilized between the components being joined, an unequally stressed set of fasteners can result in gasket distortion and subsequent problems like leakage. Accurate and reliable torque wrenches help insure that fasteners are tightened to the proper specifications.
Torque wrenches may be of the mechanical or electronic type. Mechanical torque wrenches are generally less expensive than electronic. There are several types of mechanical torque wrenches that are routinely used to tighten fasteners to specified torque levels. Of these, clicker type mechanical torque wrenches are very popular. Clicker type mechanical torque wrenches make an audible click to let the user know when a preset torque level has been achieved and simultaneously provide a feeling of sudden torque release to the user.
One example of a clicker type torque wrench includes a hollow tube in which a spring and block mechanism is housed. The block is forced against one end of a bar that extends from a drive head. The bar and drive head are pinned to the hollow tube about a pivot joint and rotate relative thereto once the preset torque level is exceeded. The preset torque level is selected by a user by causing the spring to exert either greater or lesser force on the block. The force acts on the bar through the block to resist the bar's rotation relative to the hollow tube. As the torque exerted on the fastener exceeds the preset torque value, the force tending to cause the bar to pivot relative to the hollow tube exceeds the force exerted by the block that prevents the bar's rotation, and the block “trips.” When released by the block's action, the bar pivots and hits the inside of the tube, thereby producing a click sound and a sudden torque release that is detectable by the user.
Another example of a clicker type torque wrench measures the deflection of a deflectable beam relative to a non-deflectable beam, the deflectable beam causing a click once the preset torque is reached. These and other types of clicker type mechanical torque wrenches are popular since they are relatively easy to operate and make torquing relatively quick and simple. The user merely sets the desired torque value and pulls on the handle until he hears and feels the click and torque release, indicating that the desired torque value has been reached.
One drawback that limits the usage of many mechanical type torque wrenches is the inability to measure the angular rotation of the fastener. Typically, mechanical torque wrenches lack this ability because they do not include a power source and, therefore, cannot support the use of the required sensor, such as a gyroscopic sensor. As such, for fasteners where it is necessary to rotate the fastener through a specified angle after the desired torque level is applied with the mechanical torque wrench, an electronic torque wrench with the ability to measure angular rotation is often required to complete tightening the fastener.
Some electronic torque wrenches (ETWs) are capable of measuring angular rotation of the wrench, and therefore the fastener, in addition to measuring the amount of torque applied to the fastener. As such, for those fasteners that require further rotation after the initial application of the desired torque value, an electronic torque wrench may be desirable since only one torque wrench is required. However, fasteners are often positioned such that both the torque and the desired additional angular rotation may not be applied with the torque wrench in a single, continuous motion. In such cases, an electronic torque wrench having a ratcheting feature can be used.
The present invention recognizes and addresses certain or all the foregoing considerations, and others, of prior art constructions.
One embodiment of the present invention provides a mechanical torque wrench with a wrench body defining an elongated interior compartment, a wrench head including a workpiece engaging portion and a bar extending therefrom, the wrench head being pivotably secured to a first end of the wrench body at a pivot joint, the bar extending into the interior compartment and the workpiece engaging portion extending outwardly from the wrench body. A set spring is disposed within the interior compartment of the wrench body, a block is disposed between a rear face of the bar and the set spring, and a dial screw is threadably received within the interior compartment of the wrench body such that the dial screw moves along a longitudinal axis of the wrench body when rotated, rotation of the dial screw in a first direction compressing the set spring and rotation in a second direction allowing expansion of the set spring. A resistive element is operatively coupled to the dial screw and produces an output signal, the output signal being dependent on a position of the dial screw relative to the resistive element. A first sensor is operatively coupled to the wrench body and produces a first output signal, the first output signal being proportional to an amount of rotation being applied to the workpiece by the torque wrench during a first rotational cycle of the mechanical torque wrench. A processor converts the output signal into an equivalent torque value, the equivalent torque value indicating a preset torque to be applied by the mechanical torque wrench to the workpiece, and converting the first output signal into a first angle value through which the workpiece has been rotated. A user interface includes a display for displaying the equivalent torque value. The application of a torque greater than the preset torque to the workpiece causes the wrench head to pivot relative to the wrench body about the pivot joint.
Another embodiment of the present invention provides a mechanical torque wrench with a wrench body defining an elongated interior compartment, a wrench head pivotably received in the interior compartment, the wrench head including a drive portion for engaging the workpiece and a bar extending into the interior compartment. A set spring is disposed within the interior compartment of the wrench body, a dial screw is rotatably received within the interior compartment of the wrench body, rotation of the dial screw in a first direction increasing force exerted on the set spring and rotation of the dial screw in a second direction decreasing force exerted on the set spring by the dial screw. A gyroscopic sensor is operatively coupled to the wrench body and produces a first output signal, the first output signal being proportional to an amount of rotation being applied to the workpiece by the torque wrench. A processor converts the first output signal into a first angle value through which the workpiece has been rotated during a first rotational cycle of the torque wrench. A user interface includes a display for displaying the first angle value. The application of a torque greater than a preset torque value to the workpiece causes the wrench head to pivot relative to the wrench body about the pivot joint
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention according to the disclosure.
Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring now to
Electronics unit 12, including a user interface, is received on wrench body 14 between the hand grip and wrench head 16. An interior compartment 19 of wrench body 14 houses a clicker mechanism 26 that includes a set spring 28, a plug assembly 30, a block 32, and slender bar 20, as best seen in
An adjustment assembly 34 is disposed on wrench body 14 opposite wrench head 16 for selectively adjusting a resistive element assembly 36 mounted to wrench body 14. Adjustment assembly 34 includes an end cap 38, a dial screw 40, and a nut 45 (
Wrench head 16 is pivotably secured to a first end of wrench body 14 such that bar 20 extends into interior compartment 19 and ratcheting mechanism 18 protrudes outwardly from wrench body 14. Wrench head 16 is secured to wrench body at pivot joint 50 that includes a pivot pin 52 that is both perpendicular to longitudinal center axis 48 of wrench body 14 and transverse to a plane defined by torque wrench 10 as it is rotated about a workpiece during torquing operations. As shown, wrench head 16 includes ratchet mechanism 18 so that torque may be selectively applied to a workpiece (not shown) in either the clockwise or counterclockwise direction. However, alternate embodiments need not include a ratcheting mechanism.
Electronics unit 12 includes a user interface including a visual display 54, preferably a liquid crystal display, and a user input device 56 that includes a bank of buttons. Visual display 54 and input device 56 are both supported on printed circuit board 42 which is in turn supported by a housing 58, preferably formed of injection molded plastic. Printed circuit board 42 additionally carries a microcontroller and any additional electronic components for operation of the electronics unit. Visual display 54 includes a numerical display 60 (
Referring now to
As best seen in
Referring now to
End cap 38 includes an axial bore 33 that is configured to slidably receive first end 44 of dial screw 40. As shown, an outer surface of dial screw first end 44 and an inner surface of axial bore 33 define corresponding hexagonal cross-sectional shapes such that end cap 38 is non-rotatable relative to dial screw 40. Second end 46 of dial screw 40 is threaded and received by correspondingly threaded nut 45 that is rotationally fixed inside inner compartment 19 of wrench body 14. As such, rotation of end cap 38, and therefore dial screw 40, relative to wrench body 14 causes dial screw 40 to translate axially along longitudinal center axis 48 of wrench body 14. The direction of axial motion is dependent on the direction of rotation of end cap 38 and causes dial screw 40 to either increase or decrease the torque value at which block 32 trips.
As best seen in
As shown, an annular groove 41 is formed about a central portion of dial screw 40 by a pair of radially outwardly extending shoulders 43a and 43b. Annular groove 41 is configured such that its fore and aft dimensions are substantially the same as the fore and aft dimensions of adjustment pin 82 of sliding potentiometer 72a. Annular groove 41 is configured to slidably receive adjustment pin 82 of sliding potentiometer 72a such that, as dial screw 40 is rotated in either direction and is translated along longitudinal center axis 48 of wrench body 14, adjustment pin 82 is engaged and moved by either radial shoulder 43a or 43b, depending upon the direction of axial motion of dial screw 40, so that the overall resistance provided by the sliding potentiometer is altered. Annular groove 41 is dimensioned and configured such that minimal friction is encountered as radial shoulders 43a and 43b are rotated relative to adjustment pin 82, and adjustment pin 82 is configured to have a smooth cylindrical outer surface. As well, adjustment pin 82 is received in annular groove 41 so as to minimize unwanted vibrations that can possibly be transferred to the sliding potentiometer during use. Vibrations are also reduced since dial screw 40 is threadedly received by nut 45, and thereby immobilized with respect to the wrench body. These features help to maintain a stable display of the preset torque value on the display. Alternate embodiments of dial screw 40 may include an annular groove that extends radially inwardly into the body of dial screw 40 rather than being formed by a pair of radial solders 43a and 43b, as shown.
Referring now to
After the desired preset torque value is selected, the user presses angle mode selector button 66c to enter the angle mode of the torque wrench so that a desired preset angle value may be selected. As best seen in
Referring again to
When mechanical torque wrench 10 is used to measure angular rotation, gyroscopic sensor 27 senses the rotation of the mechanical torque wrench and sends an analog electrical signal 61 that varies in voltage proportionally to the rate of rotation to a gyroscopic signal conditioning unit 63 that amplifies the signal and filters it to remove noise from the signal. Gyroscope signal conditioning unit 63 outputs an amplified and conditioned analog electrical signal 65 to microcontroller 102 that converts electrical signal 65 to an equivalent angular value in degrees and adjusts for any offset of the signal. Adjusting for the offset of the signal increases the accuracy of the wrench by compensating the signal for any reading that may be present before the wrench is actually rotated. Microcontroller 102 sends an electrical signal 69, including the current accumulated angle value to digital display 54, via LCD driver circuit 68. Preferably, digital display 54 displays the current accumulated angle value in the form of both a bar graph display 71 and a numeric value display 60 during the rotation of the wrench up to a preset target accumulated angle value, as shown in
Referring additionally to
In one embodiment, microcontroller 102 utilizes a moving window digital filtering algorithm to convert the digital data points from analog-to-digital converter 91 into a plurality of equivalent digital values that it then uses to determine the accumulated angular rotation being applied with the mechanical torque wrench 10, as discussed in greater detail below. In the present example, microcontroller 102 samples one thousand digital data points per second and uses a moving sample window of 10 milliseconds. As the mechanical torque wrench rotates, microcontroller 102 averages the first ten digital data points, one taken each millisecond, thereby producing a first equivalent digital value at time t=0.01 seconds, wherein t=0.0 seconds marks the initiation of rotation of the torque wrench. At time t=0.011 seconds, microcontroller 102 averages the digital data points taken between times t=0.002 and t=0.011 seconds, thereby producing a second equivalent digital value. At time t=0.012 seconds, microcontroller 102 averages the digital data points taken between times t=0.003 seconds and t=0.012 seconds, thereby producing a third equivalent digital value. This continues such that an equivalent digital value is provided every millisecond until the mechanical torque wrench 10 is no longer being rotated. Microcontroller 102 utilizes these equivalent digital values and a numerical integration method, as discussed below with regard to
Microcontroller 102 performs a numerical integration with the average angular velocity values determined for each 10 millisecond period to determine the accumulated angle value through which the mechanical torque wrench is rotated, and subsequently, the fastener as well. Microcontroller 102 sends an electrical signal including the current accumulated angle value to the digital display. In the present embodiment of the torque wrench, microcontroller 102 performs the numerical integration in accordance with the equation:
where, (θ) is the accumulated angle value, (ω) is the calibration constant retrieved by the microcontroller 102 in response to receiving the (ith) average equivalent digital value, and Δt is the preferred sample period of 10 milliseconds.
Note, in alternate embodiments of the mechanical torque wrench, the digital filtering algorithm does not utilize the moving window method of averaging to determine the individual equivalent digital values. Rather, the digital filtering algorithm determines an independent equivalent digital value each millisecond that corresponds to the electrical signal produced by gyroscopic sensor 27, beginning at time t=0.001. The digital filtering algorithm then averages the individual equivalent digital values over a selected window of time, that being 10 milliseconds in the present example, and provides the average equivalent digital value to microcontroller 102 for use in the previously discussed numerical integration method. In yet another alternate embodiment of the mechanical torque wrench, no averaging feature is utilized by the digital filtering algorithm in providing equivalent digital values. Rather, the digital filtering algorithm simply produces an equivalent digital value at the end of a selected window of time, that being 10 milliseconds in the present example, and provides this equivalent digital value to microcontroller 102 for use in the previously discussed numerical integration method. These embodiments may be desirable when a lesser degree of accuracy from the mechanical torque wrench is acceptable.
Preferably, after assembly, each mechanical torque wrench 10 is calibrated in order to derive the previously discussed calibration constants that are stored in flash memory. The mechanical torque wrench is rotated at a plurality of known angular velocities that would be expected to be encountered during normal operation of the mechanical torque wrench. The equivalent digital value produced at each known angular velocity is measured and recorded. A curve is fit to these data points that allows the determination of the angular rotational value, or calibration constant, for each received equivalent digital value.
Microcontroller 102 generates alarm signals in the form of audio signals and light displays of appropriate color once it is determined that the current accumulated angle value of the fastener is within a pre-selected range of the preset target accumulated angle value. As previously discussed, once the mechanical torque wrench trips at the preset torque value, the user manually switches the torque wrench and digital display 54 from the torque mode to the angle mode such that it displays accumulated angle values rather than the preset torque values.
As shown, two small arrows 83 are located on opposing sides of the eighth segment. Arrows 83 are graphical indicators to the user that accumulated angle measurement is above 75% of the preset value. Each segment 79 within frame 81 represents 10% of the preset angle value, starting from the left or bottom of each bar graph, respectively. For example, if only the first two of segments 79 are displayed, the current angle value is above 15% and below 24% of the preset angle value, and is therefore approximately 20% of the preset angle value. Simultaneously, digital display 54a/54b also displays the accumulated angle value applied up until that time in numeric display 60, as discussed in greater detail below.
Once the target preset torque value has been reached and the angle mode of the torque wrench is entered by the user depressing angle mode selector button 66c, numeric display 60 displays the accumulated angular rotation of the torque wrench, rather than the preset target torque value, and angle mode indicator 97 shows “Ang” to indicate the wrench is in the angle mode, as best seen in
Referring additionally to
The amount of torque applied to the fastener increases until clicker mechanism 26 (
Microcontroller 102 also determines whether the current accumulated angle value is equal to or greater than the preset target accumulated angle value. If the current accumulated angle value has not yet reached the target value, microcontroller 102 sends electrical signal commands 69 to LCD driver circuit 68 to generate appropriate signals to digital display unit for updating the number of segments 79 shown in current accumulated angle indicator 71 and the current accumulated angle value shown in numeric display 60.
As well, microcontroller 102 switches green 56a, yellow 56b, and red 56c LEDs on or off depending on the current accumulated angle value applied to the fastener up until that time. Preferably, microcontroller 102 maintains green LED 56a on as long as the current accumulated angle value is below 85% of the preset target accumulated angle value and switches it off once the current accumulated angle reaches 85% of the preset target accumulated angle value. Microcontroller 102 switches yellow LED 56b on for current accumulated angle values greater than 85% but less than 96% of the preset target accumulated angle value. Microcontroller 102 switches red LED 56c on once the current accumulated angle value reaches 96% of the preset target accumulated angle value and stays on thereafter. Once the current torque value reaches the preset target accumulated angle value, or is within a user selected range, microcontroller 102 generates electrical signals to generate an alarm sound on annunciator 47. At this point, the user ceases to rotate the mechanical torque wrench, and numeric display 60 alternately flashes both the preset torque value and the final accumulated angle value to which the fastener was subjected. Note, however, it may be possible to achieve the preset target accumulated angle value without having to use the ratcheting feature of the mechanical torque wrench, i.e., the desired rotation of the fastener is achieved with a single rotational stroke of the torque wrench. In many applications, the fastener will need to be rotated by using multiple ratcheting cycles. The selection of percentage ranges for each color may be programmed, and the percentages at which the LEDs are switched on or off can be changed to suit the specific application.
The torque wrench continues to accumulate angle either until the wrench is powered off or until the user depresses the angle mode selector button 66c twice in rapid succession (thereby ending the while loop indicated in
The algorithm also keeps track of the activity of the torque wrench. If the wrench is inactive for a predetermined period of time, the electronics unit shuts off the power to save battery life. Preferably, a predetermined period of three minutes is used. Regardless of whether the unit is switched off by manually pressing the power button or due to an inactivity-triggered auto shutoff, the microcontroller saves the unit selected in non-volatile memory (flash memory in the preferred embodiments). This feature allows the electronic unit to come on and display the last preset torque value and selected unit.
The embodiments of the mechanisms for converting the mechanical rotary dialing motion into an equivalent electrical signal described herein are for illustration purposes only. It is envisioned that other embodiments may also use optical, magnetic, or capacitance based mechanisms as position sensors for the dial screw rather than the resistance-based mechanism discussed above. For example, magnetic sensors such as magnetostriction rods with ring wipers can be used. Similarly, optical scales and laser diode readers can be used, as can capacitance sensors having two sliding grid patterns with one stationary and the other movable to change the capacitance. Furthermore, the mechanical rotary motion of a thumb wheel used in split beam type mechanical torque wrenches falls within the scope of this invention. No matter what mechanism is used to generate the rotary motion, the methodology needed to convert the rotary motion to an equivalent electrical signal does not change from what is described in this invention. These and other like mechanisms that can be used to convert a mechanical rotary motion into an equivalent electrical signal are within the scope of this invention.
While one or more preferred embodiments of the invention are described above, it should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit thereof. It is intended that the present invention cover such modifications and variations as come within the scope and spirit of the appended claims and their equivalents.
This application claims priority to U.S. Provisional Patent Application No. 61/417,930 filed Nov. 30, 2010, the entire disclosure of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61417930 | Nov 2010 | US |
