FR2505978A1 - Adjustable hinged lamp linkage - has fulcrum at point of zero resultant moment of linkage with counterweight - Google Patents

Abstract

The linkage can be applied to a desk lamp or magnifying glass and consists of a pivot arm (11) hinged (at '0') to a fixed support (13). Two transverse links (8,10) are hinged to the ends (C,A) respectively, of the pivot arm. The link (8) carries the workpiece (7) at one end (D) and is extended beyond the hinge (C) to the other end (F). The link (10) carries a counterweight (9) on its overhanging extremity (B) and is hinged to the third link (12) at a point (E) between links (A,B). The other end of the link (12) is hinged to the end (F) of one transverse link. The workpiece can be placed in any position as the total moment about the fulcrum '0' is zero.

Description

The subject of the present invention is a balanced deformable mechanical device, a device which can be used as a support for objects which it is desired to be able to easily
impose any position in space: lamps, mirrors, microphones, control boxes, etc.

 According to the invention, such objects capable of being moved inside a spherical volume are balanced using a single force, a counterweight for example, this balancing being theoretically able to be perfect in any position of the system.

 Known systems of this kind, however, have significant limitations, the best of them allowing the movement of the object in question only on the surface of a certain sphere. We also know systems with two arms and two counterweights, which allows them to have three degrees of freedom, this, however, at the cost of too large a total mass, often prohibitive.

The balanced deformable mechanical device according to the invention consists of a plurality of elements hinged together and subjected to the action of a set of forces parallel to each other, in such a way that in any position said device retains its state of equilibrium, device characterized in that it comprises: lû.un central element AC, articulated at one of its points C on a fixed support; and 20. as many peripheral elements AB,
CD, that there are forces F1, F2 acting on the system, these elements being articulated on the central element AC at respective points A, C, which form an alignment AOC with the point O of the central element AC , said peripheral elements being, moreover, arranged so as to remain constantly parallel to one another, whatever the angle G that their common direction forms, in space, with that of said alignment AOC, the device being, moreover,
characterized in that one of said forces F1 is intended to balance together the remaining forces such as F2 acting on the device and applied, each, to one of the peripheral elements such as CD, articulated at points such as C, 1 The device according to the invention is also characterized in that the ratio between, on the one hand, the value of the resultant of all the forces to be balanced such as F2 and, on the other hand, the value of the balancing force F1 must be equal and of opposite sign to the inverse ratio of the distances separating from said point O of the central element AC, the joints C, A of the respective peripheral elements CD,
AB and, also, in the inverse ratio of the distances separating, on each of said peripheral elements CD, AB, the points of articulation C, A, on the central element AC, of the respective points of application of the result of the forces such as F2 and force F1.

 In addition to the above arrangements, the invention also comprises other arrangements which will emerge from the description which follows, referring in particular to the appended drawings and in which - Figure 1 is a theoretical diagram defining the construction of a device according to the invention, if one has to balance a single useful force, - Figure 2 is a theoretical diagram defining the construction of a device according to the invention, if one has to balance a set of two useful forces, - FIG. 3 represents the application of the invention to a device where one has to balance a single useful force, - FIG. 4 represents the application of the invention to an articulated assembly so as to form a deformable parallelogram subjected to the action of four forces in a state of equilibrium, - Figure 5 shows the application of the invention to the construction of an articulated arm-lamp support.

FIG. 1 shows the central element AC of a device according to the present invention. This element is assumed to be articulated at one of its points O, on a fixed support, not shown. At one of its ends, the element AC comprises a peripheral element or arm AB, at the end B of which is applied a force F1. At its other end, the central element AC comprises a second arm CD, parallel to the first and to the end D of which a force is applied
F2. The joint direction of the two arms, AB and CD, forms with
AC an angle G, essentially variable. The common direction of the forces F1 and F2 forms, with the central element, an angle J, also, essentially variable. In the case shown,
F2 is the useful force, for example the weight of the object fixed at point D, the force F1 being the balancing force, for example a counterweight intended to compensate for the weight of the useful object fixed at D.

We know that the resulting moment O of the forces F1 and -F2 is zero, whatever the angles G and J, provided that the equality is verified
F2 = OA = AB
F1 OC CD
It should be noted that the equilibrium in O remains valid even if the points B and D of application of the forces F1 and F2 are no longer in the same plane.

This is how assuming, for example
AB directed towards the front of the plane of the figure, CD will necessarily be directed towards the rear of this plane, the points B and D describing, then, circles situated in planes respectively at the front and at the rear of the plane of the table and parallel to the latter respective distances from point O to these two planes will be between them in the inverse relationship, changed sign, of the magnitudes of the forces F2 and F1.

 FIG. 2 corresponds to the case where it is proposed to no longer balance a single useful force, such as F2, but two forces, F2 and F3, the latter being assumed to be applied to the end of an EH arm parallel to the two previous ones and whose articulation point on the central element AC is located on the same side of the point O as the point C previously defined.

We can show that the forces F2 and F3 can be replaced by their resultant F'2 applied at a point K of CD and defined by the two relations
F'2 = F2 + F3. OE
F
OC
CK = F3.EH + F2.CD
F'2
It is easy to see that, starting from the above, we can extend the calculation to a device such that it is possible to balance a plurality of useful forces such as F2, F3, etc ... by means of a unique force such as F1, and this by determining step by step, in value and position, the successive results, in the manner indicated above, that is to say by first determining the value and the position, on CD of the resultant of F1 and the first of the other forces, then, still on this same CD support, the value and the position of the resultant obtained by adding, to the one which has just been defined, one of the forces additional, etc ...

 The device represented by FIG. 3 essentially comprises: - a base, reference 1, articulated in 2 on a support 3, base comprising, at one of its ends an arm 4 on which acts a force F2 to be balanced and at its other end, an arm 5 at the end of which the balancing force F1 acts.

 6 shows an angular connection device between the two arms, a device intended to ensure, in all circumstances, parallelism between these arms.

The articulation in 2 can advantageously be carried out using a ball joint which allows the base 1 to pivot in all directions. The arms 4 and 5 are assumed to be pivotally mounted on axes placed respectively at C and A and perpendicular to the plane of the figure, this plane
can however take any desired orientation, thanks to the ball joint 2.The forces F1 and F2 can be of any kind (gravity, elasticity, buoyancy, etc ...)
The angular connection 6 between the arms can be achieved using any known system (cogwheels and chains, gears, connecting rods, etc.), the members serving for the transmission can have a center of gravity movable relative to base 1, on the condition that they satisfy the previously defined implementation rules.

 Under these same conditions, the device is stable, the moment resulting in O being zero, the respective moments of F1, of F2 in A and in C being opposite and compensated using the link 6.

 The simple case above being assumed to satisfy the preceding relationships 1, 2 and 3, it may prove necessary, to compensate for any defects in production, to provide one or more brakes afi rotation, in order to compensate for these imperfections, and, Also, avoid the action of parasitic forces such as shocks, the traction effect of the electric power wire of a lamp, the effects of wind, etc ...

FIG. 4 shows a structure with a deformable parallelogram, to which four forces are applied, respectively F1, F2, F3, F4, the first being intended to balance all of the other three, including
F2 is the useful force proper, F3 and F4 being the forces inherent in the respective elements AC and EF, the weight of these elements for example, if we also consider the forces F2 and F1 as being respectively the useful weight and the counterweight.

 It should be noted that in the known devices of this species, it is generally specified that the centers of gravity of the two brass supports respectively the useful object, for example a drawing table and its counterweight, are aligned with the pivot center O duvsysteme, but that we systematically forget to take into account the weights of the two other elements of the system, such as AC and EF, weights which are far from negligible in relative impedance, when it is a robust support intended to support a light useful object, such as a microphone, for example.

As for the forces present, these were completed by a first resultant F'2 applied at D 'and the final resultant F "2 applied at D", hence the condition of alignment of the three points B, O and D ", according to the principles previously stated and the equations which follow

 It is therefore seen that the fact, in the prior art, of neglecting the forces F3 and F4 would result in a. the alignment of points B, O and D and not of points B, O and D "as is the case for the present invention, hence the technical progress brought by the latter.

 We see in Figure 5, a system according to the invention articulated in a deformable parallelogram and intended to support a lamp, such as 7. The long sides of the parallelogram are, respectively, 12 and 11, the latter comprising at point O a ball joint the fixing on the support 13. The lamp is carried by an arm 8, the counterweight 9 by an arm 10, parts of these last two arms constituting the small sides of the deformable parallelogram.

 The angular travel allowed is limited & a little less than 1800.

 The O-shaped ball joint can be economically produced by a fork in which the element ll is capable of pivoting in the plane of the switchboard, this fork itself being pivotable about its axis, assumed, here, to be vertical.

Due to the indifferent balance of the system, the support 13, shown here as being vertical, can between fixed in any position, in particular against murn wall or ceiling.

 As for the lamp 7, it is obviously adjustable in any position around its center of gravity without changing the balance of the system.

 The counterweight 9 can advantageously be constituted by the transformer, if such a member is part of the electrical equipment of the device. Finally, due to the balance of the latter, its stability remains ensured, even when the dead weight of the foot of the support is very inferior to that of other elements of the system.

 It follows from the foregoing descriptions that, whatever the embodiments and application adopted, a balanced deformable mechanical device is obtained which, while serving the same purpose as the previously known devices, presents with respect to the latter , important advantages, some of which have been mentioned in the foregoing and others of which will emerge from the use of the various devices according to the invention.

 As is apparent from the above, the invention is in no way limited to those of its embodiments and of application which have just been described in a more explicit manner; on the contrary, it embraces all the variants which may come to the mind of the technician in the field without departing from the scope, or the scope, of the present invention.

Claims (6)

 1. Balanced deformable mechanical device, consisting of a plurality of elements hinged together and subjected to the action of a set of forces parallel to each other, in such a way that in any position said device retains its state of equilibrium, device characterized (in that it comprises: 1 3 - a central element AC, articulated at one of its points O on a fixed support, and 20. AC the joints C, A of the respective peripheral elements CD, AB and, also, in the inverse ratio of the distances separating, on each of said peripheral elements CD, AB, the points of articulation C, A, on the central element AC, of the respective points of application of the result of forces such as F2 and of force F1. C, this device also being characterized in that the ratio between, on the one hand, the value of the resultant of the set of forces to be balanced such as F2 and, on the other hand, the value of the balancing force F1 must be equal and of opposite sign to the inverse ratio of the distances separating from said point O of the central element C, which form an alignment AOC with the point O of the central element AC, said peripheral elements being moreover, arranged so as to remain constantly parallel to one another, whatever the angle G that their common direction forms, in the space, with that of said AOC alignment, the device being further characterized in that one of said forces F1 is intended to balance all of the remaining forces such as F2 acting on the device and applied, each to one of the peripheral elements such as CD, articulated in points such as F1, F2 acting on the device, these elements being articulated on the central element AC at respective points A, as many peripheral elements AB, CD as there are forces  2. Device according to Claim 1, characterized in that, in the case where the set of forces to be balanced consists of two forces such as F2, F3, 10. the value of their resultant F'2 is obtained by adding at the value of the force F2, that of the other force F3, multiplied by the ratio of the distances on the alignment AOC of the central element AC, between the point O of this element and each of the painted joints, respectively , E and C, alesaid respective forces F3, applied to the peripheral element EH and F2 mentioned above;  20. said resultant F "2 is applied, on the peripheral element CD at a point K distant from point C by a length which is obtained by dividing, by the previously established value of this resultant, the sum of the products of each of said forces respectsvemert F2 and F3, by the distance separating, on its corresponding support, the point of application of each of these forces, ie points D and H, from the corresponding points C and E mentioned above.  3. Device according to Claim 2, characterized in that, in the case where the set of forces to be balanced is constituted by more than two forces, one obtains, in value and position, their resultant, by adding, to that of the first two forces, the third of these forces, in value and position, then the fourth and so on, until the exhaustion of said set of forces to be balanced.  4. Application of the device as defined by Claim 3 to an assembly comprising a base (l) articulated at one of its points (2) on a support (3), said base comprising, at one of its ends, a arm (4) to which the force to be balanced F2 is applied and, at the other end, an arm (5) to which the balancing force F1 is applied, said assembly further comprising an angular connection (6) intended to maintain constantly said two arms (4,5) parallel to each other.  5. Application of the device according to event 3, to a set of four elements AB, CD, AC, EF, articulated together so as to form a deformable parallelogram, of the respective forces F1, F2, F3, F4, being applied to the center of gravity of each of these elements, forces of which the first F1 must balance all of the other three F2, F3, F4, said system being characterized in that the point of application B of said balancing force F1 and the point of application D "of the result of the forces F2, F3, F4 form an alignment with the articulation point O of the device on its support.  6. Application of the assembly according to Claim 5 to a structure with four elements, arranged in a deformable parallelogram, structure intended to carry a lamp (7) at the end of a first arm (8) and a counterweight (9) at the end a second arm (10), two other arms (11, 12) completing said parallelogram, the articulation of this structure on its support (13) being produced by any known means such as, in particular, a ball joint, this means being disposed at a point O of the arm (11) meeting the alignment condition set out in Claim 5.