LINEAR MEASURING DEVICES

Abstract: A measuring instrument comprises a portable case (45) housing a drum (11) on which is wound a flexible mesuring line or tape (10) which runs over a rotary capstan (15) provided with teeth (16) engaged by a sensor (24) acting as a pulse generator to an electronic counter (27). In addition there is a direction sensor (21) arranged to provide a count-up or count-down signal and a further direct measuring wheel (30) as teeth (32) acting as a pulse generator to the same counter (27).

Description: "Linear Measuring Devices" This invention relates to linear measuring devices as used for example for measuring dimensions of rooms, buildings, or other objects, or for measur¬ ing the distance travelled along a surface. The term 'linear' is intended also to include measurement of distances along non-straight paths or over non-flat surfaces. So-called "tape measures" are well-known, consisting of a l-ength of tape along which are marked the units of measurement, (e.g. centimetres or inches) , the tape being wound on a rotary reel provided with rewind facilities. Such tape measures have certain limitations, for example only a limited length of tape can be stored on a reel, the tape cannot easily be read in the dark, or by the blind, and it may become dirty or be damaged. Wheel measuring devices have also been proposed in which the wheel is run along the surface to be measured and the motion of the wheel operates a counter or display which represents units of measurement. These wheel measuring devices, are only applicable to certain specific uses and are subject to certain operating difficulties. I ' t is an object of the invention accordingly to provide an improved measuring device which will overcome some of the problems experienced with existing instruments. Broadly stated the invention consists in a linear measuring device comprising a holder, a movable measuring element, a sensor for detecting movements of the measuring element, an electrical pulse generator coupled to the sensor, an electronic digital counter or calculator circuit connected to the pulse generator, and an output circuit connected to a visible or audible or recording output unit. According to a preferred feature of the invention the sensing means includes a pulse generator sensitive to the movements of the element, and an electronic counter or calculator circuit connected to the pulse generator. In some forms of the invention the sensing means includes a rotary element engaging the measuring element so as to be turned by linear movement thereof, and arranged to generate pulses - 3 - accordingly. Thus, in most instances the measuring element is elongate and has physical, mechanical, magnetic or optical linear measuring points, and the sensing means includes a detector capable of sensing such measuring points. According to another preferred feature of the invention the measuring element is movable in one direction for measuring purposes, and includes means for shifting the measuring element in the opposite direction into a starting position. In some forms of the invention the measuring element may be a rigid extendable member, this being particularly useful for measuring small dimensions. In other forms of the invention the measuring element is a long thin flexible line, tape or the like, wound in a coil or drum. Conveniently, it may be in the form of a fine thread. This is the most economical form and permits the maximum length to be contained on a drum of given dimensions. Preferably the device also includes a spring, or motor-driven or manual rewind mechanism for the coil or drum. Alternatively or in addition to the measuring element referred to, it may be in the form of a direct- rotary measuring device comprising a rotor with at least part of its periphery exposed. This allows the device to measure uneven or non-linear surfaces or _ 4 - dimensions and it may, for example, be used to measure the internal circumference of a drum. For a number of purposes such as use by the blind it is of advantage that the device should include an audible signalling device to provide audible informa¬ tion on the movement of the measuring element. Furthermor the device may also include means for converting the display from imperial to metric or other units. It is also of advantage to include means for connection to an external remote signal generator The device may also be incorporated with a height-measuring system operating on the "vertical sextant angle" principle. Thus the device may include a vertical angle measuring device and a calculator programmed to combine the tangent of the measured angle with the sensed linear measurement to provide a measure of the vertical height of an object. To establish the vertical datum there may be a bubble level, pendulum or the like. The device preferably includes means for totalling the movement of the measuring element in one direction," and for subtracting measured movements in the opposite direction and it may also include means for setting and/ or adjusting the datum or zero of the sensed measurement. In a particular preferred form σf the inven- tion the device includes means for attaching the holder to a tool such as an electric power drill, saw or moulder, with the measuring element engaging the work- piece so as to indicate the depth of 'cut' made by the tool The invention may be performed in various ways and several preferred embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a diagram illustrating the main mechanical and electrical components of one embodiment of the invention, Figure 2 is an external view of this same example Figure 2A is an end view on an enlarged scale illustrating the clip at the end of the measuring line, Figure 3 is a block circuit diagram illustrating the main electrical components of another embodiment, Figure 4 is a sectional elevation through anothe embodiment of the invention illustrating the main mechanical components, Figure 5 is an external view of another embodiment illustrating an auxiliary measuring wheel, Figure 6 is a perspective view illustrating a modified clip at the end of the measuring line, and Figure 7 is a block circuit diagram illustrating the main electrical and mechanical components in another example of the invention. Referring first to Figure 1 the measuring apparatus in this example comprises a flexible line 10 wound on a drum 11 provided with an automatic rewind spring 12 and. having a clip or other fitting 13 at its free end. -The line may be formed of any suitable flexible non-extensible, rotproof,material such as nylon,steel,or synthetic plastics. The line in this example is preferably a circular section monofilament and it is wound around a friction pulley or capstan 15 having a shallow external groove with which the line makes a good frictional grip. This Capstan is formed with a number of closely spaced teeth or notches 16 at intervals corresponding to the smallest unit of measurement required for the measuring line. For example, if the smallest required unit of measurement is 0.5 m.m. the teeth will be spaced at the appropriate angle 'measured from the rotary axis 17 to give a circumferential measurement of 0.5 m.m. at the periphery of the groove between adjacent tooth positions The apparatus also includes a first detector comprising a feeler 23 positioned to engage the teeth 16 as the Capstan rotates and to influence a sensor 24 which may, for example, be a piezo electric crystal or a microswitch, the output from the sensor being fed on line 25 to the digital counter circuit to be described. The apparatus also includes a further directional sensor comprising another finger 20 also arranged to engage the notches 16.and connected to a sensor 21 which may take a variety of forms but produces an output signal on line 22 which provides an indication of either forward or reverse movement of the Capstan 15. This directional sensor may, for example, be an electronic filter circuit coupled with a piezo electric crystal designed to detect the shape of the pulses generated by the crystal in response to movements of the feeler 20. Alternatively the two sensor 21,24 may be coupled with circuitry designed to produce a directional signal in response to the phase difference or phase change between the two feelers. The electronic digital counter includes a "de-bouncing unit" 26,including filter circuitry to eliminate unwanted or unintensional pulses, a binary coded decimal counter 27, and a binary coded decimal de-coder 28 linked with a seven segment LCD display 29 arranged to display the measured incrementsin decimal for ,in this case in metres, centimetres and millimetres. When the line is rewound on to the drum 11 by the spring 12 the sensor 21 detects the reverse rotation of the capstan wheel 15 and provides a pulse on line 22 to the counter 27 to indicate that the pulses are to be subtracted thereby providing a countdown towards zero. At any instant the resultant measurement from the counter 27 may be held on the display 29 or in an electronic memory by pressing a button 35, which prevents- further pulses reaching the counter 27 and holds the last reading on the display 29. When switched off the device is automatically reset to zero. The apparatus also includes a .direct wheel measuring facility comprising an exposed rotor wheel 30 mounted to rotate on an axis 31 and having a rotary pulse generator including a toothed rotor 32 ga ed by a feeler 33 attached to a piezo electric or other electric pulse generator 34. The output from this pulse generator is fed to the de-bounching unit 26 and to the other components of the counter already described. In addition there is a further feeler 37 connected to a sensor 38 providing an electric signal signifying forward or reverse movement of the wheel 30.- This component of the instrument operates in somewhat the same manner as the flexible line measuring device, but the measuringpulses are generated by running the wheel 30 along a surface whose measurements are required. In addition this instrument includes an auxiliary input 40 in the form of an electrical socket intended to co-operate with an auxiliary jack attached to an external pulse generator such as a pedometer, or manual or foot operated switch. These pulses will be added and displayed in the unit 29 as previously described. In the instrument illustrated in Figure 2 and Figure 2A the case 45 has a centimetre scale 46 along one edge with the flexible measuring line 10 issuing through a hole at the centre, the line having a flat clip or plate 48 at its free end with a slot 49 which allows the clip to be temporarily held at the end of the scale when required, or alternatively to allow the line to be temporarily anchored round any suitable fixed object such as a hook or pole. In this example the external direct measurement wheel 30 is located at one corner of the case, the LCD display unit 29 is located centrally, the auxiliary input 40 on the opposite edge of the case and, in-addition, there is a switch or button 41 controlling a metric to imperial conversion circuit, and a mode selector switch 42. In the alternative embodiment illustrated in Figure 3 like parts are indicated by the same reference numerals. This unit includes an additional audible unit indicated generally at 50, which includes a loudspeaker 51 connected to a tone generator 52 combined with counter and register store. In addition there is an audio on/off switch 53 and an external audio line 54 operated by switch 55. In the example illustrated in Figure 4 again the main components are indicated by the same reference numerals as in Figure 1 and in this case the rewind drum 11 is connected to a "Tensator" (RTM) spring 60 whose opposite ends are wound around the rewind drum 11 and the spring housing drum 61. This provides a substantially constant rewind force over the whole length of the measuring line. The other components in this illustrated example are similar to those of Figure 1. In the further example illustrated in Figure 5 the direct measuring wheel 30 of the Figure 1 example is replaced by a detachable measuring wheel 63 of larger diameter mounted on a fitting or bracket 64, which is designed to clip on to the body or housing 65 of the instrument and is provided with electrical contacts 66,67 to engage corresponding contacts 68,69 on the body of the housing so that the impulses generated by the wheel are fed to the counter and display unit in the same manner as previously described. Figure 6 illustrates a modified form of clip 70 at the end of the measuring line 10 intended to facilitate fastening of the line around a fixed pole or hook 71. A further example illustrated in Figure 7 contains components similar to those of the Figure 1 example and indicated by the same reference numerals. In addition, this example includes a sextant and bubble level unit 75 linked to the first calculator unit76. The mercury"bubble gauge"77 has an output 78providing an indication when the instrument is held level. The sight tube 79 is coupled to an angle meter 80 providing a pulsed output on line 81 which is a measure of tan where Q is the angle of elevation of the sight tube. When combined with the measurement signal D generated by the pulse generator 21 from the measuring line 10, the calculator 76 provides an output equivalent to D tan ϋ , i.e. the height of the object being observed. In the Figure 7 example 87 is an external pulse generator such as a foot switch, connected via jack 40 to the calculator, 82 is the metric/ imperial conversion switch, 83 is the zero or reset datum switch, 84 is a manual on-off switch for the tone generator/synthesiser 52, and 85 is an external printer connected to the counter circuit through the jack 86. The calculator 76 includes a decimal keyboard 88 by which programmedmathematical functions or further numerals may be introduced. It will be appreciated that the line or tape 10 may in use accummulate dirt or in other ways suffer an increase or change in thickness, and this may affect the accuracy of the measurements made by the rotary capstan 15 and sensor device 16,24. To eliminate or compensate for this the device preferably includes a cleaning element 18 in the form of a felt or fibre wiper and an electrical thickness sensor or gauge 19 which continually senses the dimensions of the element 10, and applies a corresponding correction as a negative percentage factor to the counter 27, the correction being proportional to the sensed change in dimensions. Alternatively or in addition the gauge 19 may be connected to an electrical warning device, such as a flashing light or audible alarm, to indicate that the element 10 needs to be cleaned, and that the measurements are suspect. In the embodiment of Figure 3 the audible unit 50 with the loudspeaker 51 may take various different forms. For example, the tone generator may be linked to the counter circuit to produce a series of tones or "bleeps" equivalent in number to the digits which would be displayed visibly, for the assistance of the blind, or in the dark for example. Alternatively or in addition to the tone generator there may be a speech synthesiser also linked to the counter/calculator unit and arranged to generate speech sounds representing the digits in the display unit. The calculator preferably includes an electronic memory which' may, for example, be of the magnetic or diode type and the calculator preferably includes at least the basic mathematical functions of a portable, hand-held instrument, i.e. ,+,-,x and . Thus, for example, it is possible to take a first measurement a_ which will be held in the memory to be followe by a second linear measurement b_ also held in the memory, so that the operator can selectively either add a. + b,or multiply a_ x b to produce an area. Like¬ wise, the volume of a room or tank having sides a_,b,c_, can be obtained by three successive measurements a.,b,£, combined by a double multiplying function. Likewise, simple mathematical calculations can be performed with simple inbuilt or programable functions; for example, the radius of a cylinder R can be obtained from a measurement Q of its circumference using the programmed .- function R= Q/2π ' Conveniently the calculator unit is coupled to the counter so that the measured values can be entered directly in the calculator. Alternatively, however, the calculator may be a separate unit in the same holder having manual binary decimal input keys . The operator then enters the measured values into the calculator as in a normal independent calculator unit. The sextant-bubble^level unit 75 may have a fixed sextant angle if preferred, in which case the calculator may have a pre-programed tan £7 value to obtain the height h of the observed object directly from the formula h_ = d tan ζ , where d is the measured distance from the object. The output from the counter may, if required, . be connected to an internal or external printer to provide a permanent record of the measured or calculated values. The instrument may also include mechanical and/ or electronic "hold" or locking devices to retain the instantaneous position of the capstan or measuring wheel or to maintain the sensed measurement in the electronic memory. The direct measuring wheel may, if required, be provided with an adjustable zero/datum index to facilitate direct measurements and to afford an adjustable set zero. The control buttons on the casing of. the instrument may be recessed and they may be combined with an electronic bleeper circuit to provide an audible indication when any button is actuated. - 15 - It will be appreciated that in these preferred examples of the invention it is unnecessary to provide any measuring points or indicia on the flexible measuring line since movements of the line are trans¬ ferred to the rotary capstan which carries the measuring points. This greatly increases the life of the instrument and eliminates risk of malfunction from loss of indicia.

Claims: CLAIMS 1. A linear measuring device comprising a holder, a movable measuring element, a sensor for detecting movements of the measuring element, an electrical pulse generator coupled to the sensor, an " electronic digital counter or calculator circuit connected to the pulse generator, and an output circuit connected to a visible or audible or recording output unit. 2. A measuring device according to claim 1, in which the measuring element 0 is flexible and the sensor includes a rotary element engaging the measuring element so as to be turned by linear* movement thereof, and arranged to actuate the pulse generator accordingly. 3. A measuring device according to claim 5 2 , in which the rotary element is provided with physical, magnetic, or optical measuring points, and the sensor includes a corresponding detector capable of sensing such measuring points . 4. A measuring device according to Claim 1, 0 in which the measuring element is elongate and flexible and has physical, magnetic or optical spaced measuring points , and the sensor includes a detector capable of sensing such measuring points. 5. A measuring device according to any of 5 the preceding claims , in which the measuring element is movable in two opposed directions for measuring purposes, and including means sensitive to the direction of move ¬ ment thereof, and arranged to provide a corresponding modification to the signal supplied to the counter/ calculator circuit. 6. A measuring device according to claim 5, in which the counter/calculator includes an ; electronic memory for totalling the movements of the measuring element in one direction, and means for subtracting measured movements in the opposite direction. 7. A measuring device according to any of the preceding claims , in which the measuring element is an elongate flexible line or tape, and including a winding drum, and a rewind spring, or motor capable of applying a substantially constant torque thereto. ' 8. A measuring device according to any of the preceding claims , in which the measuring element is in the form of a thin flexible line of approximately circular cross-section. . A measuring device according to any of the preceding claims, in which the audible output unit includes a tone generator or speech synthesiser arranged to provide audible information on the movement of the measuring element. 10. A measuring device according to any of the preceding claims, including an additional direct rotary measuring device comprising a rotor with at least part of its periphery exposed, a sensor for detecting movements thereof, and a pulse generator coupled to the - 18 " sensor and having an output to the same counter/calculator output circuit. 11. A measuring device according to any of the preceding claims τ including means for converting the output from imperial to metric or other units. 12. A measuring device according to any of the preceding claims, including an auxiliary input comτec:tion to the counter or calculator circuit, for connection to an external remote signal generator. 13. A measuring device according to any of the preceding claims , including a vertical angle measuring device, and in which the calculator is programmed- to combine the tangent of the angle with the sensed linear measurement to pro-vide a measure of the vertical height of an object. 14. A measuring device according to claim 13, including a bubble level, pendulum or the like to provide a horizontal or vertical datum for the angle. 15. A measuring device according to any of the preceding claims, including means for setting and/or " adjusting the datum or zero of the sensed measurement. 16. A measuring device according to any of the preceding claims , including a mechanical and/or electronic "hold" device for retaining a measurement in the device. 17. A linear measuring device comprising a holder, a winding drum, an extendable flexible measuring element wound on the drum, a rotary pulley engaging the element for rotational movement in response to linear movement of the element, means for sensing rotary move¬ ments of the pulley, a pulse generator operated thereby, an electronic digital counter/calculator having an input connected to the pulse generator, and an output to a visible or audible output unit , a second direct measuring device including an exposed wheel , and a pulse generator associated therewith, and having an output to the same digital counter/calculator circuit. 18. A measuring device according to claim 17, including means for selectively switching the connection between the counter and the two pulse generators. 19. A portable measuring and calculating device including a movable measuring element, a sensor coupled thereto to detect movements thereof, a pulse generator connected to the sensor to generate- pulses in accordance with the sensed movements, an electronic memory for retaining the sensed measurement signal, a programmed or programmable calculator circuit associated with the memory to apply selected mathematical functions or operations to the retained signal, and an output unit for displaying or -recording the output of the calculator. 20. A portable linear measuring device combined with an electronic calculator having a data storage, and means for transferring sensed linear measurements into the data storage, the calculator including a programmed or programmable logic function circuit for performing one or more mathematical operations, and a visible or audible display or recording unit.

Inventors: CARE RONALD JAMES, CARE, RONALD, JAMES
Applicants: CARE RONALD JAMES, CARE, RONALD, JAMES
Application year: 1987
Main classification: H03M1
IPC codes: G01B3, G01B21, G01D7