Apparatus for measuring tensile properties of hair

Abstract

A strand of hair is clamped between two posts, both of which are movably supported on a base. The first post is urged in one direction by a spring. Initially the spring and associated post are latched in position with the spring compressed. The second post remains unloaded between two compression springs. To make a measurement, the latch is released and the first post permitted to move away from the second post under urging of the spring. The rate of movement of the post is limited by a dash-pot device. As the first post moves away, the force of the pull of the hair is transferred to the second post. This force is detected by an electronic sensor. The extent of movement between the two posts is also detected electronically providing a measure of the elongation of the hair. Both readings are recorded on dials.

Description

BACKGROUND OF THE INVENTION

This invention relates to apparatus for testing the physical characteristics of human hair, and more particularly, is concerned with apparatus for measuring the elongation and tensile strength of a single hair strand.

It has long been recognized in the care and treatment of hair that one of the clues to the health and vitality of the hair is its strength and elasticity as measured by the extent the hair stretches or elongates before breaking. For example, a weak tensile strength indicates a breakdown of the cross linkages which unite the keratin protein molecules and/or an excessive loss of the protein molecules themselves. Such a condition might be caused, for example, by subjecting the hair to harsh alkaline chemicals or excessive exposure to the sun's ultraviolet rays. A high tensile strength, on the other hand, indicates a sufficient protein structure with many cross linkages uniting the entire molecular structure of the hair.

While the elasticity of the hair also is related to the unity of this protein structure, it is more directly related to the water molecules which are present to a greater or lesser extent in the hair structure. The water molecules soften the attraction between keratin protein molecules, and when present in the proper amount allow the hair to stretch to 175% normal elongation before breaking. Excessive water molecules in the hair allow the hair to stretch beyond the normal limits. If the hair's moisture is removed, the hair becomes brittle and lacks the proper elongation.

While devices have heretofore been proposed which purport to measure the strength and elongation of hair, such known devices have been lacking in accuracy and reproducibility of results, particularly in the hands of inexperienced operators, or have been too complex and expensive to be sold and used in great numbers.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus for simultaneously measuring both the strength and elongation of human hair. The apparatus is designed to operate in a manner which substantially eliminates the human element of the operator in obtaining consistently accurate and reproducible results. This is accomplished in brief by providing apparatus in which hair is clamped around two posts. One of the posts is moved away from the other post at a substantially constant velocity, transferring a force to the other post through tension in the hair strand. This force is resisted by a spring. An electronic sensor measures the displacement of the spring-loaded post relative to a fixed reference and equates this distance for forcing exerted by the hair. A second sensor electronically measures the displacement of the constantly moving post relative to the other post, which indicates the elongation of the hair. An electronic processor interprets the data from the sensors, and displays the data on two meters.

DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference should be made to the accompanying drawings, wherein:

FIG. 1 is a perspective view of the instrument of the present invention;

FIG. 2 is a plan view of the instrument with the cover removed;

FIG. 3 is a sectional view taken substantially on the line 3--3 of FIG. 2;

FIG. 4 is a perspective view of the molded diaphragm used in the hydraulic damping system; and

FIG. 5 is a schematic wiring diagram of the electronic measuring circuit.

DETAILED DESCRIPTION

Referring to the drawings in detail, the numeral 10 indicates generally a hair measurement apparatus having a cover 12 and a base 14. The cover is preferably formed with a slanting front on which are mounted a pair of meters 16 and 18 which are calibrated to indicate respectively elongation, in suitable units of length, and strength in suitable units of force. Projecting out of the front of the cover are a pair of relatively movable binding posts 20 and 22. The binding posts 20 and 22. The binding post 20 is provided with a V-shaped groove 24 extending around the periphery thereof. The binding post 22 is provided with an outer flange 26 and a shaft 28 on which is threaded a rotatable clamping member 30. Rotation of the clamping member 30 by a radially projecting knob 32 causes the clamping member 30 to move axially of the shaft 28, bringing a clamping surface 34 into clamping relationship with the inside surface of the flange 26. A pin 36 limits the rotation of the clamping member 30. In operation of the apparatus, a single strand of hair is formed in a loop. The bight portion of the loop is positioned in the groove 24 with the two ends of the loop extending over the shaft 28 where they are clamped between the clamping surface 34 of the clamping member 30 and the inside of the flange 26.

In addition to the meters 16 and 18, the slanting front panel of the instrument also includes a knob of an On/Off control switch 38, which is turned on to activate the measurement circuit as hereinafter described. Also, there is provided a Start control knob 39. When moved to the start position, the knob 39 initiates movement of the binding post 22 to the right, as viewed in FIG. 1, causing the loop of hair under test to be brought into tension around the binding post 20 and tending to pull the binding post 20 to the right also. As hereinafter described, as the binding post 20 is pulled to the right by the strand of hair, it resists the movement with increasing force, thus causing the hair to be placed under increasing tension as the binding post 22 continues to move to the right, until the tension on the hair exceeds the breaking point and the hair loop snaps, thereby releasing the binding post 20 to return to its initial position.

Referring to FIGS. 2 and 3, the numeral 40 indicates a shaft which is journaled in supporting blocks 42 and 44, the supporting blocks being rigidly mounted on the base 14. Block 42 is clamped to the base by means of screws 46 and 48 extending through elongated slots in the block 42, the slots extending parallel to the longitudinal axis of the shaft 40. Thus the supporting block 42 is adjustable relative to the base 14 by loosening the screws 46 and 48. The shaft 40 passes through a third block 50 also mounted on the base 14.

A first slider assembly, indicated generally at 52, is slidably mounted on the shaft 40 by means of a ball bearing type sleeve 54. The sleeve 54 permits the slider assembly 52 to move freely along the shaft 40 with very low frictional resistance. The binding post 20 is anchored to the slider assembly 52 and is laterally movable therewith along the shaft 40. The slider assembly 52 is prevented from rotating about the axis of the shaft 40 by means of a ball bearing roller 58 which runs in a slot 59 in the block 50.

The null position of the binding post 20 and associated slider assembly 52 is determined by a pair of compression coil springs 62 and 64 which are positioned concentrically on the shaft 40 in either side of the slide assembly. The spring 62 is held in a counterbore 66 in the supporting block 42. Similarly the spring 64 is seated in a counterbore 68 in the intermediate block 50 and in a counterbore 70 in the first slider assembly 52. Adjustment of the supporting block 42 to the right or left permits the null position of the binding post 20 to be shifted while still maintaining a zero net force on the slider assembly 52 longitudinally of the shaft 40.

The binding post 22 and associated hair clamping mechanism is mounted on a slider block 72. The block 72 has a hole which receives the shaft 40, the block being fixedly secured to the shaft 40, for example, by clamping set screws 74. The block 72 has the portion 76 extending parallel to the shaft and extending beyond the block 50 toward the slide assembly 52. The binding post 22 is mounted on the portion 76 in close proximity to the post 20 when in the initial or starting position. A compression spring 78 concentric with the shaft 40 and extending between the fixed block 50 and the slider block 72 urges the block 72 to the right together with the shaft 40. The block 72 is held in the initial position against the force of the spring 78 by a release lever 80 which is pivotally supported on the block 44 for horizontal movement about an axis 82. A roller 84 normally engages the block 72 under the urging of a tension spring 86 extending between the lever 80 and block 44. The Start knob 39 which projects out to the top of the cover, as described in connection with FIG. 1, is attached to the lever 80, permitting the lever 80 to be moved away from the block 72, thereby moving the stop roller 84 out of contact with the block 72. The block 72 is then urged to the right by the compression spring 78.

The rate of movement of the block 72 with its binding post 22 is limited by a dash-pot assembly mounted in the block 44. The dash-pot assembly includes two cylindrical openings 88 and 89. The opening 88 extends in axial alignment with the shaft 40, one end of the shaft 40 extending into the opening 88. The second opening 89 is substantially larger in diameter than the opening 88 and includes a piston 90 and compression spring 92 therein. A single molded flexible rubber diaphragm has a base portion 94 and two cylindrical shaped bubble portions 96 and 98 having a diameter corresponding respectively to the openings 88 and 89. The bubble portions are inserted in the openings and the base 94 is clamped in place by a plate 100. The two bubble portions of the diaphragm are connected by a hollow ridge portion 102 which forms a passage connecting the interior of the two bubble portions when the base 94 is clamped in position by the plate 100.

It will be seen that in operation the dash-pot assembly operates to resist the movement of the shaft 40. As the shaft 40 moved to the right, as viewed in FIG. 2, it forces hydraulic fluid within the bubble 96 out through the passage 102 into the bubble 98. A set screw 106 extending through the plate 100 opposite the passage 102 can be adjusted to adjust the rate of flow at which fluid passes between the two bubbles, thereby controlling the rate at which the shaft 40 moves the binding post 22 under the urging of spring 78.

Strength and elongation measurements are performed by the electronic circuit shown in FIG. 5. The circuit is controlled by two sensors, which preferably are in the form of linear potentiometers. A strength measuring sensor, indicated generally at 110, is mounted on the base 14 and has a movable plunger 112 connected to the slider assembly 52 by a pin 114, as shown in FIG. 2. An elongation sensor, indicated generally at 115, is mounted on the slider assembly 52. The sensor has a movable plunger 116 which extends through an opening in a lug 118 on top of the slider block 72. The plunger 116 is secured to the block by a pin 120.

As the binding post 20 is moved from its null position by the movement of the binding post 22 through the strand of hair looping the post 20, the sliding contact of the sensor 110 is moved proportionately. As the hair in the loop elongates under tension, the slider block 72 moves away from the slider assembly 52. As a result the sliding contact of the sensor 115 move in direct proportion to the elongation of the hair strand.

Referring to the circuit diagram of FIG. 5, the sensor 110 is connected across a positive potential source. The moving contact 112 of the sensor is connected through a resistor 122 to the base of an NPN transistor 124 connected as an emitter follower across a potential source. The emitter load is a capacitor 126. The milliammeter 18 is controlled in response to the voltage across the capacitor 126 through two transistor stages 128 and 130. The meter 18 is calibrated in grams or other suitable units of force. As greater and greater force is applied through tension in the hair fiber to the post 20, the change in the position of the contact 112 of the sensor 110 is reflected in a corresponding increase in current through the meter 18.

When the tension on the hair strand under test reaches the breaking point, the voltage on the output of the potentiometer wiper contact 112 drops back to substantially zero. However, the capacitor 126 retains its charge, holding the meter 18 at the reading corresponding to the force required to break the hair.

Similarly, the elongation sensor 115 has the wiper contact 116 connected through a series resistor 132 to the base of a transistor 134 connected as an emitter follower, with a capacitor 136 as the emitter load. The milliammeter 16 is controlled from the voltage across the capacitor 136 through a pair of transistors 138 and 140.

In order to derive a measurement of the elongation of the hair at the time the hair breaks, an interlock circuit is provided which turns off the transistor 134 when the sensor 110 drops back to its null position at the time the hair strand snaps. To this end, an NPN transistor 142 is connected with the collector and emitter circuit in shunt between the base of the transistor 134 and ground. The NPN transistor 142 is normally turned off, but when turned on acts to turn off the transistor 134, thereby holding the meter 16 at the level determined by the existing charge on the capacitor 136. The transistor 142 is controlled by a transistor 144 having its base connected to the wiper contact 112 of the sensor 110. The emitter is connected to ground through a capacitor 146 while the collector is connected through a resistor 148 to the base of a PNP transistor 150. The collector of the transistor 150 is connected through a resistor 152 to the base of a transistor 154, having a collector load resistor 156. The base of the transistor 142 is in turn connected to the collector of the transistor 154. Normally the transistor 144 is conducting as are the transistors 150 and 154, causing the transistor 142 to be biased off. However, a transistor 158 having its base connected also to the wiper contact 112 is connected as an emitter follower, having the capacitor 146 as the emitter load.

When the hair strand breaks, the wiper contact 112 drops back to its initial position, causing the transistor 144 to be turned off, which in turn causes the transistors 150 and 154 to be turned off and the transistor 142 to be turned on. This turn off the transistor 134, causing the meter 16 to be held at the level set by the charge on the capacitor 136.

More reliable hair strength measurements are obtained if the tension force is measured at a level less than the maximum elongation of the hair at the breaking point. For this reason, a transistor 160 is provided having its collector-emitter circuit connecting the base of the transistor 124 to ground. The base of the transistor 160 is connected through a resistor 162 to the emitter of the transistor 140. By this arrangement, the transistor 160 is initially biased off, allowing the capacitor 126 to charge to the potential of the wiper contact 112. At some predetermined amount of elongation, preferably of the order of 10 to 15 percent, the voltage across the resistor 164 reaches a level sufficient to turn on the transistor 160, thereby preventing further charging of the capacitor 126. The meter is held at the reading level corresponding to the predetermined amount of elongation. The meters 16 and 18 are reset to zero by the switch 38 being turned off.

Thus it will be seen that a measurement device is provided which indicates tensile strength and elongation of hair. By increasing the tension on the hair at a fixed rate, highly reproducible results are obtained. At the same time, the device is very simple and fool-proof in its operation.

Claims

What is claimed is:

1. Apparatus for measuring the tensile properties of hair or other fibers, comprising:

a base member,

a movable first hair engaging member,

means supported on the base for guiding said first member along a linear path,

a movable second hair engaging member spaced from the first member;

the hair under test extending between the first and second members,

means supported on the base for guiding said second member along a linear path parallel to the path of movement of the first member,

first spring means extending between the first member and the base for resisting movement of the first member with increasing force with displacement of the first member in the direction of the second member,

means including second spring means extending between the second member and the base for moving the second member in the opposite direction at substantially constant velocity to put the hair under uniformly increasing tension against the urging of the first member by the first spring means,

first indicating means for indicating changes in position of the first member relative to the base,

second indicating means for indicating changes in position of the second member relative to the first member , and a third spring means extending between the first member and the base for urging the first member in the opposite direction than that of the first spring means to provide an adjustable null position of the first member.

2. Apparatus for measuring the tensile properties of hair or other fibers, comprising:

a base member,

a movable first hair engaging member,

means supported on the base for guiding said first member along a linear path,

a movable second hair engaging member spaced from the first member;

the hair under test extending between the first and second members,

means supported on the base for guiding said second member along a linear path parallel to the path of movement of the first member,

first spring means extending between the first member and the base for resisting movement of the first member with increasing force with displacement of the first member in the direction of the second member,

means for moving the second member in the opposite direction at substantially constant velocity to put the hair under uniformily increasing tension against the urging of the first member by the first spring means,

first indicating means for indicating changes in position of the first member relative to the base,

second indicating means for indicating changes in position of the second member relative to the first member, and

means responsive to said second indicating means for locking the first indicating means when said second indicating means indicates a predetermined change in position of the second member.

3. Apparatus of claim 1 further including means responsive to the first indicating means for locking the second indicating means when the first member drops back to its initial position on breaking of the hair.