GB1594833A

GB1594833A - Measuring device

Info

Publication number: GB1594833A
Application number: GB24236/77A
Authority: GB
Original assignee: Day A T; Goodale J S C
Current assignee: Day A T; Goodale J S C
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-08-05

Description

(54) MEASURING DEVICE (71) We, ALBERT THOMAS DAY, a British Subject, of 9, Cavendish Avenue, Harrogate, North Yorkshire, and JOHN STUART CHARLES GOODALE, a British Subject, of 82, Farnborough Road, Farnborough, Hampshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a measuring device intended primarily but not exclusively for the measurement of human limb joints such as finger joints. Analysis of human limb joint dimensions provides valuable information on the development of disease and the efficaciousness of related medical treatment.

The value of the analysis is determined by the accuracy of initial measurement and the repeatability of equipment and conditions in subsequent measurements. Apparatus already used for this purpose is either reliant on operator skill or is of such 'economical' design as to make impossible any accurate and reliable cross correlation of results on a long term basis.

According to the present invention, there is provided a measuring device comprising a housing containing a store of flexible and inextensible tape; means for feeding tape from said store out of the housing to form a loop, and a trigger mechanism operatively connected to the feeding means such that actuation of the trigger causes tape. to be fed from the store; means for applying a predetermined tension to the tape in the loop so that the tape can encompass and substantially conform to the shape of an object to be measured when that object is, in use, placed within the loop; and means for determining the amount of tape forming the loop, the device being such that at least a substantial part of the tape in the loop is returnable to said store within the housing after removal of said object from the loop.

Thus a measuring device according to the invention enables the making of accurate and reliable measurements of an object, such as a finger joint, since the tension in the loop as it is tightened around the object has a predetermined value and thus will not vary substantially from one to another.

Preferably, the tape store is a rotary member on which the tape is wound and which is rotatably mounted in the housing adjacent a passage through which the tape extends leading to the exterior of the housing, one end of a length of tape being secured to the rotary member, and the other end thereof being secured to the housing, preferably adjacent the outer opening of said passage. Thus rotation of said rotary member in one direction causes tape to be unwound from the rotary member, and the unwound tape to be fed through said passage and out of the housing to form said loop, and rotation of the rotary member in the opposite direction causes tape in said loop to be withdrawn into said housing and taken up on the rotary member once again.

Conveniently, the rotary member is arranged for rotation in said one direction by a drive tape which is connected to a spindle on which the rotary member rotates, the drive tape being longitudinally movable in order to rotate said rotary member in said one direction on actuation of said trigger mechanism, preferably via a pulley system in the housing.

Rotation of said rotary member in said other direction is preferably performed by a return spring, for example a coil spring wound around the spindle.

The means for determining the amount of tape in a loop of tape extending from the housing preferably comprises a wheel which is mounted on and is rotatable with the spindle on which the rotary member rotates, the periphery of the wheel bearing a calibrated scale of which part is visible through a transparent portion of the housing, there being provided a relatively stationary cursor which is also visible through said transparent portion so that the indicia of the scale lying adjacent said cursor at any time is an indication of the amount of tape in said loop at that time.

The calibration of the scale may be representative of the actual tape loop length, or any other suitable dimension of the tape loop, such as its diameter, when the tape loop is, in use, tightened about an object to be measured.

Conveniently, the means for determining amount of tape in a loop of tape extending from the housing includes means for deriving electrical signals indicative of said amount of tape at any instant. said electrical signal deriving means being adapted for supplying said signals to external data processing equipment.

Reference will now be made to the accompanying drawings, which illustrate, by way of example, one embodiment of the invention, and of which: Figure 1 is a side view of a measuring device according to the invention, with the housing partly removed to illustrate the disposition of the measuring tape within the housing; Figure 2 is a view similar to that of Figure 1, except that it is partly sectioned to illustrate the calibration mechanism; Figure 3 is a view of the device in the direction of arrow A in Figure l; Figure 4 is a view of the device from the opposite side to that shown in Figure I, partly sectioned to illustrate the trigger mechanism; Figure 5 is a diagrammatic view of the rotary parts of the device, viewed in the same direction as In Figure 3; Figure 6 illustrates a view similar to a part of Figure 3 illustrating the orientation of the loop to the housing according to another embodiment of the invention; and Figure 7 is a view similar to that of Figure 2, showing how the device can be modified according to a further embodiment of the invention for feeding measurement data directly to automatic processing equipment.

The measuring device illustrated in the drawings comprises a housing 1, of a suitable durable plastics material which is moulded or otherwise formed so that it can be fitted around the various components housed therein, during assembly of the device. The size of the housing is such that it can be comfortably held in the hand; the housing is generally rectangular in side view, having two opposed broad side walls 2, 3, narrow side walls 4, 5 and top bottom walls 6, 7 respectively. A window 8 is provided in an angled wall 9, interconnecting top wall 6 and elide wnll 4. for purposes described herei nafter.

Within the housing, a rotary spindle 10 is journalled in the opposed broad side walls 2 and 3. A rotary member or drum 11 is mounted on the spindle 10 for rotation therewith. A length of flexible, inextensible tape 12 is wound around the drum 11, the number of turns of tape around the drum being determined by the relative sizes of the drum and the object which the device is to be used to measure. In the case illustrated, the device is to be used to measure a finger joint, or the like, and thus a single turn is sufficient.

One end of the tape is anchored on the drum at a point 13, whilst the other end of the tape extends through a tangential passage or volute 14 in the housing and is anchored to the housing at 15 adjacent the mouth 16 of the volute 14. Since it is pointless to measure from zero, the tape is arranged so that a small loop 17 of the tape remains between the mount 16 of volute 14 and the anchoring point 15, even when the tape is fully taken up on the drum 11. The drum is fitted with means for limiting its rotational movement in either direction to inhibit breakage of the tape 12.

Also mounted on the spindle 10 for rotation therewith is a wheel 18, of which the periphery bears a calibrated scale 19. The wheel 18 is positioned adjacent the drum 11 so that the scale 19 is readily visible through the window 8 (as best shown in Figure 3) which is adapted to magnify the scale numbers for easy and accurate measurement. On the inner surface of window 8 is formed a cursor line 20 against which measurements are made. Clearly, since the wheel 18 and drum 11 rotate conjointly on the spindle 10, the scale 20 provides an indication of the angular displacement of the drum 11 from a predetermined zero or inoperative position (such as that shown in Figure 1) and hence the amount of tape unwound from the drum to increase the size of loop 17. A coiled return spring 21 is fitted on the spindle 10 adjacent the wheel 18 to provide a return, rotational force to the drum to rewind tape thereon both during and after a measurement operation, as described below.

The trigger mechanism for feeding tape from the drum 11 out of the housing is shown in Figure 4, and comprises a plate 22 which is mounted in the housing for slidable movement in a direction parallel to the broad side walls 3, 4. On the plate 22 are rotatably mounted pulleys or rollers 23, disposed one on either side of an idler roller 24 which is rotatably mounted on a part 25 of the housing which is fixed relative to the plate 22. A drive tape 26, of which one end is anchored to the housing by a post 27, extends across plate 22, passing around first the adjacent one of the rollers 23, around roller 24 and then around the other roller 23; subsequently the drive tape 26 passes around a second idler roller 28 which like pulley 24 is mounted for rotation about a relatively fixed axis before being attached at its other end to a flanged drive hub 29 which is mounted on spindle 10 for rotation therewith adjacent drum 11. The plate 22 is attached to a manually operable trigger button 30 which slidably extends through an aperture in the wall 5 of the housing. Thus depression of the trigger button 30 into the housing, producing leftward movement of plate 22, as viewed in Figure 4, lengthens the respective runs of drive tape between the rollers 23 and 24, and causes the drive tape to rotate the hub 29 in the anti-clockwise direction of arrow B in Figure 4. Due to the coaxial mounting of the hub 29, drum 11 and wheel 18 on the spindle 10, thus rotation of hub 29 causes the tape 12 to be unwound from the drum 11 to an extent indicated by the scale 19 on wheel 18.

The rollers 23, 24 and 28 are made of suitable low friction material, and are spaced to provide an appropriate velocity ratio to produce a relatively large angle of rotation of drum 11 from a relatively short travel of the trigger button 30.

The operation of the device to take a measurement is as follows: First of all, the trigger button 30 is depressed to rotate drum 11 and feed tape 12 out of the housing via volute 14 to increase the size of loop 17. The provision of a restricted passage or volute 14 for the tape 12 is desirable if the tape is not to buckle and thus jam as it is driven out of the housing.

The tape and volute dimensions are accordingly chosen to avoid this possibility. The object to be measured, i.e. a finger joint in this case, is inserted into the enlarged loop 17 and the trigger button 30 is released, allowing the tape 12 to be withdrawn into the housing by the action of the coil spring 21, until the loop of tape is tightened around the object.

The flexibility of the tape ensures that the loop encloses and conforms to the shape of the object. Since the return force exerted by spring 21 is known and is substantially constant, whatever the angle of rotation of spindle 10, the tension exerted in the tape when tightened around the object is known and can be repeated during subsequent measuring operations, making the results obtained therefore directly comparable. The angle of rotation of the drum at this stage reflects the amount of tape 12 still remaining therein, and thus indirectly the amount of tape in the loop around the object. Thus the reading from scale 19 visible through window 8 provides an indication of the dimension of the object to be measured. Conveniently, the diameter of wheel 18 is as large as possible, to maximize the scale intervals possible on the scale 19, thereby improving the readability and accuracy of interpolation of the scale measurement.

The object is then removed from the loop possibly by further depression of trigger button 30 to relieve the tape tension, after which the spring 21, used to tension the tape during measurement, acts to return the tape 12 apart from the residual loop 17 to the drum 11. Although it is convenient to use the spring 21 for this secondary purpose, a separate tape return mechanism may be provided.

When the device is used to measure a finger joint, the patient's hand is preferably presented with the back of the hand facing upwardly in as natural a posture as possible in order that the effects of muscle strain are not included as a variable in the measurement. The measurements are taken from underneath, i.e. from the palm side of the hand, with the window 8 nearest to the thumb side.

It should be noted that the position of the loop of tape in relation to the housing permits the scale 19 to be viewed via window 8 even when measurements are made underneath fingers, whilst the angled window 8 provides for easy reading in any normal measuring position.

The orientation of the tape loop to the housing is not critical. In Figures 1 to 5, the tape loop is generally parallel to the broad side walls 2, 3, but the construction may be such that as shown in Figure 6, the tape loop is generally perpendicular to the broad side walls 2, 3. This may be done, for example, by providing a twist in the volute passage 14 through 90 about its longitudinal axis, or by some other suitable means.

It is often desirable as well as, or instead of, being able to read the relevant measurement data (i.e. the length of tape in the tape loop at any instant) from a visible calibrated gauge, to be able to feed this measurement data directly to suitable processing equipment.

One way in which the device of Figures 1 to 5 might be modified to provide this function is illustrated schematically in Figure 7. A suitable "pick-off' 31, such as a digital encoder which is appropriately calibrated, is located in the housing adjacent the wheel 18.

An alternative, analogue form of "pick-off' might be a linear voltage differential transformer (LVDT) or a magnetic Hall effect transducer suitably mounted adjacent wheel 18. The "pick-off' 31 is arranged to transmit, via a line 32, electrical signals representative of the instantaneous angular disposition of the wheel 18 relative to a suitable datum to electronic circuitry, shown schematically at, 33, preferably of printed circuit board construction located with a hollow part of the housing, for example, as illustrated, that part of the housing forming a handle for the measuring device. The electronic circuitry is adapted to condition the signals received from the "pick-off' 31, to render them into a form acceptable to the data processing equipment which is to be plugged into the measuring device as at 34 for receipt of said conditioned signals. Selector or encoding switches, such as those indicated at 35 may be arranged at convenient locations on the housing to permit one-handed operatlon of the device if necessary and connected via line 36 to the electronic circuitry 33. This modifi cation of the device has the advantage that a permanent record of measurement data can be made automatically without the need for the operator of the device to halt a measurement procedure to write down or dictate the measurements visible on the calibrated scale or wheel 18.

WIIAT WE CLAIM IS:- 1. A measuring device comprising a housing containing a store of flexible and inextensible tape; means for feeding tape from said store out of the housing to form a loop, and a trigger mechanism operatively connected to the feeding means such that actuation of the trigger causes tape to be fed from the store; means for applying a predetermined tension to the tape in the loop so that the tape can encompass and substantially conform to the shape of an object to be measured when that object is, in use, placed within the loop; and means for determining the amount of tape forming the loop, the device being such that at least a substantial part of the tape in the loop is returnable to said store within the housing after removal of said object from the loop.

2. A measuring device as claimed in claim 1, in which the tape store comprises a rotary member on which the tape is wound and which is rotatably mounted in the housing adjacent a passage through which the tape extends leading to the exterior of the housing, one end of a length of tape being secured to the rotary member, and the other end thereof being secured to the housing, so that rotation of said rotary member in one direction causes tape to be unwound from the rotary member and the unwound tape to be fed through said passage and out of the housing to form said loop, and rotation of the rotary member in the opposite direction causes tape in said loop to be withdrawn into said housing and taken up on the rotary member once again.

3. A measuring device as claimed in claim 2, in which said other end of the tape is secured to the housing adjacent the outer opening of said passage.

4. A measuring device as claimed in claim 2 or claim 3, in which the rotary member is arranged for rotation in said one direction by a drive tape which is connected to a spindle on which the rotary member rotates, the drive tape being longitudinally movable in order to rotate said rotary member in said one direction on actuation of said trigger mechanism.

5. A measuring device as claimed in claim 4. in which the trigger mechanism is operatively connected to the drive tape via a puley system mounted in the housing.

6. A measuring device as claimed in any of claims 2 to 5, in which rotation of said rotary member in said other direction is performed by a return spring.

7. A measuring device as claimed in claim 6, in which said return spring is a coil spring which is wound around the spindle.

8. A measuring device as claimed in any of claims I to 7 in which the means for determining the amount of tape in a loop of tape extending from the housing comprises a wheel which is mounted on and is rotatable with the spindle on which the rotary member rotates, the periphery of the wheel bearing a calibrated scale of which part is visible through a transparent portion of the housing, there being provided a relatively stationary cursor which is also visible through said transparent portion, so that the indicia of the scale lying adjacent said cursor at any time is an indication of the amount of tape in said loop at that time.

9. A measuring device as claimed in claim 8, in which the calibration of the scale is representative of the actual tape loop length.

10. A measuring device as claimed in claim 8, in which the calibration of the scale is representative of a dimension of the tape loop when it is, in use, tightened about an object to be measured.

I I. A measuring device as claimed in claim 10, in which said dimension is the tape loop diameter.

12. A measuring device as claimed in any of claims I to 11, in which the means for determining the amount of tape in a loop of tape extending from the housing includes means for deriving electrical signals indicative of said amount of tape at any instant said electrical signal deriving means being adapted for supplying said signals to external data processing equipment.

13. A measuring device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cation of the device has the advantage that a permanent record of measurement data can be made automatically without the need for the operator of the device to halt a measurement procedure to write down or dictate the measurements visible on the calibrated scale or wheel 18. WIIAT WE CLAIM IS:-

1. A measuring device comprising a housing containing a store of flexible and inextensible tape; means for feeding tape from said store out of the housing to form a loop, and a trigger mechanism operatively connected to the feeding means such that actuation of the trigger causes tape to be fed from the store; means for applying a predetermined tension to the tape in the loop so that the tape can encompass and substantially conform to the shape of an object to be measured when that object is, in use, placed within the loop; and means for determining the amount of tape forming the loop, the device being such that at least a substantial part of the tape in the loop is returnable to said store within the housing after removal of said object from the loop.