Force-measuring device

Abstract

A force-measuring device is provided for integrating measurement of at least three radial forces acting centrally, in particular for radial presses or collets. The force-measuring device comprises a stretching-element assembly, which is concentric to a measurement axis and which comprises at least one stretching element. The force-measuring device also has at least three pressure elements spaced from each other in a circumferential direction, wherein two spreading elements are connected to the at least one stretching element at ends of the stretching element, the pressure elements are supported, by means of pressure inclines, on corresponding sliding inclines of the spreading elements, a transmitting element is fastened to a first of the two spreading elements, and a measuring sensor acts between the second of the two spreading elements and the transmitting element.

Claims

1. A force-measuring device (1) for integrating measurement of at least three centrally acting radial forces (F.sub.R), especially for radial presses or collet chucks, comprising an expander element arrangement concentric with an axis of measurement (M) and comprising at least one expander element and at least three thrust members (3) spaced apart from one another in circumferential direction, wherein two spreader members (4) are joined to the ends of the at least one expander element (2, 19), wherein: the thrust members (3) are braced via thrust chamfers (5) against corresponding sliding chamfers (6) of the spreader members (4), a transmission member (7) is fixed on a first of the two spreader members (4), and a measuring sensor (9) acts between the second of the two spreader members (4) and the transmission member (7).

2. The force-measuring device (1) of claim 1, wherein the expander element arrangement is formed by an expander sleeve (2), around which the thrust members (3) are disposed in a manner spaced apart from one another in circumferential direction and radially apart from the expander sleeve (2).

3. The force-measuring device (1) of claim 1, wherein the expander element arrangement is formed by several expander rods (19) disposed parallel to the axis of measurement and respectively between two neighboring thrust members (3).

4. The force-measuring device (1) of claim 1, wherein the expander element (2, 19) consists of a material with lower modulus of elasticity than that of the thrust members (3).

5. The force-measuring device (1) of claim 1, wherein the spreader members (4) form a one-piece unit together with the expander element (2, 19).

6. The force-measuring device (1) of claim 1, wherein the spreader members (4) have a greater radial extent than the expander element (2).

7. The force-measuring device (1) of claim 1, wherein the two spreader elements (4) are constructed in the form of end plates.

8. The force-measuring device (1) of claim 1, wherein the transmission member (7) is constructed as an axially disposed transmission rod (7).

9. The force-measuring device (1) of claim 1, wherein the sliding chamfers (6) on the two spreader members (4) are constructed as mirror images of one another.

10. The force-measuring device (1) of claim 1, wherein the sliding chamfers (6) converge toward the axis of measurement (M).

11. The force-measuring device (1) of claim 1, wherein the thrust members (3) are secured in position at the ends of the spreader elements (4) via securing elements (14) that provide radial play.

12. The force-measuring device (1) of claim 1, wherein the force-measuring device (1) has at least one handle (16, 17) at the end.

13. The force-measuring device (1) of claim 12, wherein a handle (16, 17) is provided respectively at both ends.

14. The force-measuring device (1) of claim 1, wherein the measuring sensor (9) is equipped with a dial gauge (18).

15. The force-measuring device (1) of claim 1, wherein the measuring sensor (9) is equipped with an electrical signal converter.

16. The force-measuring device (1) of claim 1, wherein the force-measuring device (1) has eight thrust members (3).

17. The force-measuring device (1) of claim 1, wherein the thrust chamfers (5) and the sliding chamfers (6) are formed by corresponding faces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail hereinafter on the basis of the drawing, wherein:

(2) FIG. 1 shows a partial longitudinal section through an embodiment of the inventive force-measuring device in unloaded condition,

(3) FIG. 2a shows a side view of a further embodiment of the inventive force-measuring device with several expander rods and

(4) FIG. 2b shows a cross section through the force-measuring device from FIG. 2a according to section plane 2b-2b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIG. 1 shows an inventive force-measuring device 1 for measuring radial forces F.sub.R acting centrally perpendicular to an axis of measurement M. An expander element arrangement comprises a single expander element, which is formed by a central expander sleeve 2. Force-measuring instrument 1 further comprises eight thrust members 3 spaced apart from one another in circumferential direction. In FIG. 1, force-measuring device 1 is in unloaded condition, i.e. no external radial forces F.sub.R are acting on thrust members 3 (F.sub.R=0).

(6) At each end, expander sleeve 2 is joined to respectively one spreader member 4, wherein expander sleeve 2 together with spreader members 4 forms a one-piece unit and spreader members 4 are constructed in the form of end plates. The unit comprising expander sleeve 2 and spreader members 4 consists of a material with a smaller modulus of elasticity than thrust members 3. Thrust members 3 are braced via thrust chamfers 5 on corresponding sliding chamfers 6 of spreader members 4. These sliding chamfers 6 are constructed as mirror images of one another.

(7) The transitions between expander sleeve 2 and spreader members 4 are indicated in FIG. 1 by broken lines perpendicular to axis of measurement M. The transitions are defined by the inner ends of sliding chamfers 6 as the innermost points of contact for thrust chamfers 5 of thrust members 3. Thrust chamfers 5 and sliding chamfers 6 are plane, corresponding faces, which converge toward axis of measurement M. Because of sliding chamfers 6, spreader members 4 have a greater radial extent than expander element 2.

(8) On spreader member 4 illustrated at the left in FIG. 1, a transition member in the form of a transmission rod 7 is fastened indirectly via a retaining arrangement 8. A measuring sensor 9, which is designed to measure the axial force acting on transmission rod 7 acts between spreader member 4 illustrated at the right in FIG. 1 and transmission member 7. A bolt 10 can be retracted into and extended from a sleeve 11 of measuring sensor 9. Bolt 10 is biased by a spring, not illustrated, into the extended position, where its end face 12 is in contact with a corresponding end face 13 of transmission rod 7. If transmission rod 7 is displaced in the direction away from bolt 10, bolt 10 is correspondingly displaced by the spring, whereby the change of position of transmission rod 7 and thus also the axial force acting thereon is sensed and can be displayed by a dial gauge 18. An analogous result is obtained for movement of transmission rod 7 in the opposite direction.

(9) A radial force F.sub.R can be transmitted to each of the thrust members 3. When radial forces F.sub.R are transmitted to thrust members 3, the latter are displaced radially and perpendicular to axis of measurement M. In the process, thrust chamfers 5 of thrust members 3 slide on sliding chamfers 6 of spreader members 4. Thereby spreader members 4 and also expander sleeve 2 are expanded in axial direction perpendicular to the direction of radial forces F.sub.R and in a direction parallel to axis of measurement M by a travel distance that is proportional to the superposition of the radial forces F.sub.R acting on thrust members 3. Transmission rod 7 together with retaining arrangement 8 is moved in axial direction toward the left. Bolt 10 is extended from sleeve 11 by the same travel distance as transmission rod 7 and retaining arrangement 8.

(10) Each thrust member 3 is secured in position at its ends by securing elements 14. For this purpose thrust members 3 have bores in axial direction at both ends. Spreader members 4 have corresponding bores in axial direction. Securing pins 15, which have a smaller outside diameter than the bore diameters of thrust members 3 and spreader members 4, are inserted into the corresponding bores of thrust members 3 and spreader members 4, whereby thrust members 3 are secured in position with radial play. The force-measuring device is further provided at both ends with respective handles 16, 17.

(11) FIG. 2a and FIG. 2b show a further embodiment of inventive force-measuring device 1, which does not have any expander sleeve but instead has in total eight expander rods 19, which are disposed respectively between two thrust members 3, of which there are likewise in total eight, and which are spaced apart therefrom in circumferential direction. For better clarity, respectively only one expander rod 19 and one thrust member 3 are marked with reference symbols in FIGS. 2a and 2b. Expander rods 19 extend parallel to axis of measurement M and at each end are respectively joined in one piece to spreader members 4. Expander rods 19 and the thrust members as a whole form substantially an octagon in cross section. In a manner similar to FIG. 1, radial forces F.sub.R on thrust members 3 can be transmitted by thrust chamfers and sliding chamfers, not illustrated in FIGS. 2a and 2b, to spreader members 4 and thus converted to an axial force, which is perpendicular to the radial forces and which can be measured within force-measuring device 1 by analogy with the embodiment illustrated in FIG. 1 and displayed via dial gauge 18. Furthermore, FIG. 2a shows a handle 16 and a retaining arrangement 8, while FIG. 2b illustrates a transmission rod 7, all of which have the same features as the corresponding handle 16 and transmission rod 7 according to the embodiment illustrated in FIG. 1.