FR2533030A1 - Ballistometer for measuring the elastic properties of skin. - Google Patents

Abstract

Ballistometer comprising a hammer 2 carried by one of the ends of an oscillating arm 1, the other end of which is equipped with a counterweight 4, this arm being firmly attached to a spindle 5 allowing it to pivot in the vertical plane, characterised in that the said spindle is firmly attached to the core 10 of a linear inductive potentiometer, the output signals of which are amplified and displayed by an electronic device known per se.

Description

Balistometer for measuring the elastic properties of the skin.

The present invention relates to a balistometer for measuring the elastic properties of the skin, of the type comprising an oscillating hammer provided with a counterweight and intended to be released on the chosen skin surface, from an imbalance position, and the successive rebounds of decreasing amplitude until it is immobilized in the equilibrium position are used to generate electrical signals which are recorded and displayed by a graphical representation.

The known apparatus of this kind (USA - The Journal of Investigative Dermatology, 69: 315-317, 1977) comprises a hammer arranged at one end of an arm pivoting around an axis perpendicular to said arm whose opposite end equipped with a counterweight is also provided with a plunger core cooperating with the winding of an electromagnet placed on the trajectory of the oscillations of said plunger core.

This device has several important imperfections which are probably the cause of its non-popularization. The following disadvantages can in particular be highlighted - The published results show a significant drive, compared to the baseline, of the response curves. On the other hand, these curves do not represent a perfect damped movement and the rebounds are not regular, as shown in the graph shown in Figure 10 These phenomena probably result from the existence of a parasitic magnetic field, induced by the system for measuring the rotation of the arm around the axis. This parasitic effect alters the periodic movement of the arm or the drift of the line and the irregularity of the rebounds.

- The rebounds are not always symmetrical with respect to the axis of maximum amplitude; which calls into question the validity of the calculation of absorbed energy which consists in averaging the ratios of successive amplitudes.

- The weight of the hammer used is very low (0.5 g), it seems difficult to make objective measurements without taking into account parameters such as the friction of the axis, the stray magnetic field which opposes the movement of the arm and even air circulation at the time of measurement.

An object of the present invention is, in particular, to eliminate the aforementioned drawbacks.

This objective is achieved by means of a balistometer comprising a hammer carried by one end of an arm, the other end of which is equipped with a counterweight, this arm being secured to an axis perpendicular to said arm and thanks to which the latter is mounted with an aptitude for free oscillation in the vertical plane, this balistometer being remarkable in that said axis is integral with the core of a linear inductive potentiometer, so that the oscillations of the arm generate rotational movements alternating and decreasing amplitude of said core inside the magnetic field created by the potentiometer coil, the resulting modifications of said magnetic field causing variations in the output signal of said potentiometer which can be amplified and displayed at using an appropriate device.

The balistometer according to the invention allows more precise evaluations of the plasto-elastic properties or tone of the skin, thanks to which it is possible to control the health of the latter and, if necessary, to prescribe treatments better suited to its state or to his characteristics. In addition, the use and arrangement of the linear inductive potentiometer makes it possible to avoid friction which distorts the accuracy of the measurements and which is encountered in other mechanical or electro-mechanical devices.

These aims, characteristics and advantages, and others still, will emerge more clearly from the description which follows and from the appended drawings in which
Figure 1 is a plan view of the balistometer according to the invention.

Figure 2 is a side view in section along line 2 - 2 of Figure 1.

Figure 3 is a cross-sectional view along line 3 - 3 of Figure 1.

FIG. 4 is a side view in section along the line 4 - 4 in FIG. 3.

Figure 5 is a detail view in cross section of the means for adjusting the angular position of the electromagnet for releasing the swinging arm.

Figure 6 is a detail view in cross section of similar means for adjusting the zero of the linear inductive potentiometer.

Figure 7 is a detail view in cross section showing the device for immobilizing the arm in the rest position.

FIG. 8 is a plan view of FIG. 7.

Figure 9 is a side view and in section illustrating the operation of the apparatus according to the invention.

FIG. 10 represents a graph of the curves of a measurement obtained using the known device.

FIG. 11 represents a graph of the curves of a measurement-carried out using the balistometer according to the invention.

Reference is made to said drawings to describe an advantageous, although in no way limiting, embodiment of the balistometer according to the invention.

This apparatus comprises an arm 1 which, for ease of execution, is formed in three rigidly assembled parts, is a tubular central part 1a in which are housed and blocked the internal extra parts of an anterior part 1b and a posterior part 1c.

On the free end of the front part 1b of the arm, is mounted a hammer 2 having a substantially cylindro-conical conformation and the tip of which is oriented downwards. The cylindrical portion of this hammer comprises a transverse bore 2a into which opens an axial thread 2b,
The free end of the front portion 1a of the arm 1 is housed in the bore 2a and the hammer 2 is immobilized on this extremTte by means of a screw 3 which is screwed into the tapping 2b and the end of which bears on a flat read that said end. This assembly allows a certain adjustment of the position of the hammer on the anterior portion of the arm. the hammer has, interestingly, a twisting weight of 4.465 gr.

The rear portion 1c is equipped with a counterweight 4 advantageously constituted by a nut screwing onto the terminal part thread it of said rear portion. The threading of this threaded portion is very fine with a pitch of 1/10 mm and allows: to reach the horizontal equilibrium position with great precision and thus gives the possibility of modifying the weight.

The central portion 1a of the arm 1 is rigidly secured to an axis 5 disposed perpendicularly to the said arm.

This axis is mounted to rotate, via its ends, in bearings 6 and 7. The bearing 6 is a spring-loaded thrust bearing and it is carried by one of the flanges 8a of a base 8 in the form of U, the base of which is equipped with a fixing device 9, for example constituted by a threaded rod and a nut, making it possible to fix the balistometer on an appropriate mobile support.

The pivots of the axis 5 and the bearings 6 and 7 in which the said pivots rotate are executed very precisely, in order to reduce, as much as possible, the friction.

According to an important characteristic of the invention, the axis 5 is integral in rotation with the core 10 of a linear inductive potentiometer generally designated by the reference 11 and whose coil 11a surrounds said core. This inductive linear potentiometer is powered by an oscillator known per se (not shown) with a frequency of 1600 Hz, with a voltage of 9 V. It is fixed, by means of its cylindrical body 11b, on the second flange 8b of the base 8. It is closed by a cover 11c which is screwed into the corpllb and in which the bearing 7 of the axis 5 is installed.

The latter carries a metal plate 12 called upon to cooperate with an electromagnet 13 intended to maintain the arm 1 in an inclined starting position and making it possible then to release said arm while preventing the value of the kinetic energy acquired by the hammer shank # 2 is distorted by a parasitic impulse from manual intervention.

The plate 12 and the electromagnet # i3 are, in fact, arranged so that when the latter is supplied, it retains said plate and the arm 1 is placed in an inclined position according to which its end equipped with the hammer 2 is in the high position.

The electromagnet-13 is mounted with an adjustable angular position, so as to allow the angle of spacing of the arm 1 to be modified relative to its horizontal equilibrium positionev Thanks to this adjustable mounting, it is possible to control and possibly to modify the quantity of kinetic energy communicated to the skin at the time of the first shock following the release of the arm 1 entrained by
the opening of the supply circuit of said electromagnet.

The latter is carried by the internal lateral face of a rotary ring 14 mounted around the thrust bearing 6, that is to say coaxially with
the axis 5, and installed in the cylindrical housing that has a mount 15 rigidly fixed on the base 89 against the flange 8a The ring 14 has a radial thread 14a into which the threaded end 16a of a handle 16 is screwed passing through a slot 15a in the form of an arc of a circle formed radially in the frame 15 and at the upper part of the latter. This slot allows the lever 16 to slide during its angular movement making it possible to adjust the position of electro-magnet 13. A locking shoe 17 is mounted around the lower portion of the handle and held around the latter by a circular shoulder 16b that said handle.

This locking shoe is provided with an arcuate bearing surface which is in contact with the cylindrical lateral surface of the frame 15, and it comprises a guide boss 17a housed with a sliding capacity in the slot 15a. By screwing the lever 16, the shoe 17 is pressed by the shoulder 16b of the latter, against the edges of said slot, which makes it possible to immobilize the ring 14 and, consequently, the electro-magnet 13, in the position desired. The internal edge of the slot 15a carries a graduation opposite the degrees or marks of which an indicator needle 18 can be placed integral with the axis 5.

A device substantially similar to that which is provided for adjusting the angular position of the electromagnet 13> makes it possible to adjust the zero of the linear inductive potentiometer. The cylindrical carcass iid in which the coil 11a of the potentiometer is housed is mounted with an aptitude for rotation in the cylindrical bore of the fixed body 11b, and it has a radial thread # 1ie. In this thread, is screwed the threaded lower portion 19a of a lever 19 passing through a radial slot 11f in the form of an arc of a circle formed in the upper part of the body, said slot allowing said lever to slide when adjusting the zero of the potentiometer.A blocking shoe 20 is mounted around the lower portion of the handle and is held on the latter thanks to a circular shoulder 19b that said handle. The blocking shoe has an arcuate bearing surface which is in contact with the cylindrical lateral surface of the body 11b of the potentiometer, and it comprises a guide boss 20a housed with a latitude of sliding in the radial slot 11f. By screwing the lever 19, the blocking shoe is pressed by the shoulder 19b of the latter, against the edges of said slot, which makes it possible to immobilize the carcass 11d and, consequently, the coil 11a of the potentiometer in the desirable position. At least one of the edges of the slot 11f carries a graduation opposite the degrees or marks from which the shoe 20 can be placed or a mark carried by the latter.

The balistometer is also advantageously equipped with a device for immobilizing the arm 1 when the device is not in use.

This device can simply be constituted by a retractable fork 21 mounted with a sliding ability in a transverse bore 8c reserved in the flange 8b of the base 8. A screw 22 screwing into a thread 8d that has the flange 8b perpendicular to the bore 8c and opening into the latter, allows, by its end bearing against the rod 21a of the fork retracted bye 21, to immobilize the latter in the desired position; Figures 7 and 8 illustrating a locking position of the arm 1.

We understand the operation of the device described in the foregoing description.

The cutaneous measurement zone, for example the forehead, is placed substantially in the horizontal plane where the tip of the hammer 2 is located when the arm 1 is in the horizontal equilibrium position.

The arm is then moved away from this position and placed in an inclined position in which it is held by the action of the electromagnet 13. By opening the latter's circuit, the arm is released and the hammer 2 strikes said skin area. After hitting the skin, the hammer rebounds several times, before absorbing and coming to rest on the skin surface.

 These successive rebounds result in opposite direction of rotation movements and decreasing amplitude of the core 10 of the linear inductive potentiometer 11, which modify the magnetic field created by the coil lia of the latter, this modirv.'cation causing variations in the output signal from said potentiometer. These variations are amplified and visualized by an electronic device known per se, allowing for example their recording and their graphic representation in the form of curves corresponding to the rebounds and whose height and number provide interesting information on the tone of the skin.

FIG. 11 illustrates an example of a graph of curves obtained using the balistometer according to the invention. These curves show regular and symmetrical rebounds with respect to the axis of maximum amplitude.

 It is pointed out that most of the important organs of the balistometer according to the invention such as arm 1, hammer-2, counterweight.-4, axis 5, etc., are made of aluminum.

The balistometer according to the invention is applicable, in a particularly advantageous manner, to the measurement of the elasticity of the skin, but this advantageous application should not be considered as an absolute limitation, since the use cannot be excluded. of this balistometer for measuring the elastic properties of certain materials (plastics, for example).

Claims (10)

R E Y E N D IC A T I O N S  1. - Balistometer for measuring the elastic properties of the skin  comprising a hammer (2) carried by one end of an arm  oscillating (1), the other end of which is fitted with a counterweight (4),  this arm being integral with an axis (5) allowing it to pivot in the  vertical plane, characterized in that said axis is integral with the core  (10) of a linear inductive potentiometer whose output signals are  amplified and displayed by an electronic device known per se.  2. - balistometer according to claim 1, characterized in that the  inductive linear potentiometer is powered by an oscillator.  3. - balistometer according to claim 1, characterized in that  the hammer- (2) has an adjustable position along the anterior portion  (lb) of the arm (1).  preferably, a slow pitch thread cooperating with an axial thread - of said counterweight.  posterior portion (tic) of the arm (1), the latter comprising, of  in that the counterweight (4) # has an adjustable position along the  4. - Balistometer according to one of claims 1 or-3, characterized  5. - Balistometer according to any one of claims 1, 3 and 4  comprising an electromagnet (13) for holding the arm (1)  in an inclined position and release the latter without intervention  manual, characterized in that said electromagnet has a position  adjustable.  6. - balistometer according to claim 5, characterized in that  The solenoid (13) is carried by the internal lateral face of a  rotating ring (14) installed in the cylindrical housing of a  fixed mount (15), coaxial to the axis (5), means (16, 17)  to immobilize said ring and, therefore, said electro  magnet, in the desired position. 7. - Balistometer according to reven # dication 6, characterized in that the axis (5) of the arm (1) is integral with an indicator needle (18) moving opposite a graduation carried by the cylindrical surface of the fixed frame (15). 8. - Balistometer according to any one of claims 1, 3 and 4, characterized in that it comprises means (nib, îîd, 19 #, 20) for adjusting the zero of the linear inductive potentiometer (11). 9. - Balistometer according to claim 8, characterized in that the coil (11a) of the potentiometer (11) is carried by a rotary carcass (ild) installed in the cylindrical bore of the fixed body (lad) of said potentiometer; means (19 20) for immobilizing said rotary carcass in the desirable position. 10. - Balistometer according to one of claims 6 or 9, characterized in that the locking means making it possible to immobilize the rotating ring (14) carrying the electromagnet (13) or the rotating carcass (lid) carrying the coil (11a) of the potentiometer (11) comprise a handle (16, 19) comprising a threaded portion (16a, 19a) which is screwed into a radial thread (14a, lie) which has said ring or said carcass, this handle being mounted with a sliding ability in a radial slot (15a, 11f) in the form of an arc of a circle formed in the fixed mount (15) or in the fixed body (it), a blocking shoe (17, 20) being, preferably mounted around said lever and being held on it by means of a shoulder (16b, 19b) which the latter has, this blocking shoe being provided with an arcuate bearing surface being in contact with the cylindrical lateral surface of said frame or of said body and comprising a guide boss (17a, 20a) housed with a sliding latitude in said radial slot (15a, 11f).