APPARATUS FOR MEASURING COMPONENTS OF A POINT FORCE

• US 20100206091A1
• Filed: 02/18/2010
• Published: 08/19/2010
• Est. Priority Date: 02/19/2009
• Status: Abandoned Application

• Current Assignee: Nexense, Ltd.
• Original Assignee: Nexense, Ltd.
• Inventors: Ravitch, Vladimir, Ariav, Arie
• Application Number:
  US12/707,763
• Publication Number:
  US 20100206091A1
• Time in Patent Office: Days
• US Class Current: 73/862.41
• CPC Class Codes: G01L 1/255 using acoustic waves, or acoustic emission G01L1/10 and G01L1/16 take precedence
• CPC Class Codes: G01L 5/173 using acoustic means

Abstract

Apparatus for measuring components of a point force includes a first rigid member having an outer surface to receive the point force to be measured, and three spherical force transmitting elements, each of spherical or partial-spherical configuration, projecting from its inner surface, and a second rigid member having an inner surface facing the inner surface of the first member and formed with three sockets for receiving the three spherical force transmitting elements, each of the sockets includes two planar walls diverging in the direction towards the inner surface of the second member so as to be engaged by the respective spherical force transmitting element of the first member at two contact points, and to space apart the inner surfaces of the first and second members. A force sensor is located at each of the two contact points of each of the spherical force transmitting elements to sense the force applied by the respective spherical force transmitting element to each of the two planar surfaces of the second member.

Claims

1. Apparatus for measuring components of a point force, comprising:

a first rigid member having an outer surface to receive the point force to be measured, and an inner surface carrying three spherical force transmitting elements each of spherical or partial-spherical configuration projecting from said inner surface of the first rigid member;

a second rigid member having an inner surface facing the inner surface of said first rigid member and formed with three sockets for receiving said three spherical force transmitting elements;

each of said sockets including at least two planar walls diverging in the direction towards said inner surface of the second rigid member so as to be engaged by its respective spherical force transmitting element of the first rigid member at least at two contact points, and to space apart said inner surfaces of the first and second rigid members;

and a force sensor at each of said two contact points of each of each of said spherical force transmitting elements to sense thereat the force applied by the respective spherical force transmitting element to each of said two planar surfaces of the second rigid member.

2. The apparatus according to claim 1, wherein said three spherical force transmitting elements carried by said first rigid member, and said three sockets formed in the second rigid member, are symmetrically arrayed around the center of the respective rigid member.

3. The apparatus according to claim 2, wherein said planar surfaces of each socket are perpendicular to each other;

and wherein the magnitudes of the force components (F_x, F_y, F_z) of the applied point force along the x, y and z axes are determined as follows;

F_X=cos(π

/4)·

[(F₁−

F₂)+sin(π

/6)·

((F₄−

F₃)+(F₅−

F₆))]

F_Y=cos(π

/4)·

cos(π

/6)·

((F₃−

F₄)+(F₆−

F₅))

F_Z=cos(π

/4)·

(F₁+F₂+F₃+F₄+F₅+F₆)

wherein;

(F₁, F₂), (F₃, F₄), and (F₅, F₆) being the forces measured at the two contact points of the respective spherical force transmitting element.

4. The apparatus according to claim 3, wherein the location of the force components along the x and y axes (x_o, y_o) are determined as follows:

$x_0=\frac{\cos <br><br>\left(\mathrm{\pi <br><br>}/4\right)·<br><br>\cos <br><br>\left(\mathrm{\pi <br><br>}/6\right)·<br><br>\left(\left(F_3+F_4\right)-\left(F_5+F_6\right)\right)·<br><br>R+F_X·<br><br>h}{F_Z}$ $y_0=\frac{\cos <br><br>\left(\mathrm{\pi <br><br>}/4\right)·<br><br>\left(\begin{array}{c}\left(F_1+F_2\right)-\sin <br><br>\left(\mathrm{\pi <br><br>}/6\right)·<br><br>\\ \left(\left(F_3+F_4\right)+\left(F_5+F_6\right)\right)\end{array}\right)·<br><br>R+F_Y·<br><br>h}{F_Z}$

where, R is the horizontal distance between the disk center and each sphere center; and

h is the vertical distance between the disk top surface and each sphere center; and

x₀,y₀ are the position of the center the forces applied to the top surface.

5. The apparatus according to claim 1, wherein each of said first and second rigid members is of a circular disk shape.

6. The apparatus according to claim 1, wherein each of said force sensors includes an acoustical transmitter an acoustical receiver defining an acoustical wave transmission channel between it and the acoustical transmitters.

7. The apparatus according to claim 1, wherein each of said force sensors includes an acoustical transmitter, an acoustical receiver defining an acoustic wave transmission channel between it and the acoustical transmitters, and a measuring circuit for measuring the transit time of an acoustical wave transmitted from said transmitter to said receiver via the respective acoustical transmission channel.