Abstract:
A self-driven articulation designed for automatically deploying the elements that it connects comprises two articulation fittings made to rotate under the action of at least one passive drive element. The articulation comprises means for regulating the speed at which it deploys.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to foreign French patent application No. FR 1005090, filed on Dec. 23, 2010, the disclosure of which is incorporated by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a self-driven articulation designed both automatically to deploy elements that it connects and to lock these elements in the deployed position. The invention also relates to an articulated assembly made up of various elements joined together by at least one articulation. 
         [0003]    The invention applies more particularly, although not exclusively, to the field of space and notably to the manufacture of solar panels for satellites which panels are made up of various elements articulated together and which are deployed once they arrive in space. Numerous other applications can be imagined, both in the field of space and on earth. 
       BACKGROUND 
       [0004]    Such an articulation is, for example, described in patent applications FR 2 635 077 and FR 2 902 763. This articulation takes the form of a mechanical system that is self-driven allowing it to open and therefore allowing the elements connected to it to be deployed. The articulation comprises two articulation fittings made to rotate under the action of at least one flexible element. The articulation is held without play by means of rolling strips that cross around the articulation fittings and are kept under tension by two rollers fitted with flexible tracks, each belonging to one of the articulation fittings. The articulation comprises a device for keeping it in what is known as the stored position, this for example being achieved by means of an explosive bolt or bolt cutter positioned in the region of the solar panels to which the articulation is attached. 
         [0005]    The flexible element is for example formed by a Carpentier joint which applies a driving torque to cause the articulation to pass from its storage position into a position known as the deployed position. The drive torque is very uneven over the travel of the articulation and this leads to a speed of opening that is likewise uneven. 
         [0006]    Moreover, in order to be certain of achieving the deployed position, it is necessary for the flexible element used to generate the torque that deploys the articulation to be oversized. For example, it is necessary to take into consideration the resistive torques due, for example, to the electrical cables situated between the panels and the friction inherent to any articulation. This oversizing means that energy is restored at the end of deployment in the form of an impact against the end stops of the articulation. The energy absorbed by the end stops is dependent on the speed of impact, and therefore difficult to predict. The oversizing of the driving element of the articulation leads to an oversizing of the articulation end stops and of the elements connected by the articulation which likewise experience impacts at the end of deployment. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention seeks to alleviate all or some of the abovementioned problems by proposing a self-driven articulation in which the speed of opening is regulated thus making it possible to reduce the effect of impact at the end of opening even if the drive torque is significantly overrated. 
         [0008]    To this end, the subject of the invention is a self-driven articulation intended to be mounted between two adjacent elements, comprising two articulation fittings made to rotate under the action of at least one passive drive element, which articulation comprises means for regulating the speed at which it deploys. 
         [0009]    According to one particular embodiment, a first of the two articulation fittings comprises a first surface intended to roll without slipping at a point against a second surface belonging to a second of the two articulation fittings as the articulation turns. The means for regulating the speed at which the articulation deploys comprise a flexible duct compressed between the two surfaces at a moving point known as the rolling point. The duct comprises a restriction situated between two zones of the duct which are separated by the rolling point, and the duct contains a fluid the pressure of which increases ahead of the rolling point as the articulation fittings rotate. 
         [0010]    Another subject of the invention is an articulated assembly made up of various elements joined together by an articulation according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention will be better understood and other advantages will become apparent from reading the detailed description of one embodiment given by way of example, which description is illustrated by the attached drawing in which: 
           [0012]      FIG. 1  depicts one example of an articulation according to the invention, the articulation being in the “storage” position; 
           [0013]      FIG. 2  depicts the articulation of  FIG. 1  in the “deployed” position;  FIG. 3  schematically depicts the deployment dynamics of the articulation in the storage configuration; 
           [0014]      FIG. 4  schematically depicts the deployment dynamics of the articulation in the deployed configuration; 
           [0015]      FIG. 5  schematically depicts a first embodiment of means for regulating the speed at which the articulation deploys; 
           [0016]      FIG. 6  schematically depicts a second embodiment of means for regulating the speed at which the articulation deploys; 
           [0017]      FIGS. 7A and 7B  depict means for controlling the speed regulation as a function of temperature, which means are suited to the first embodiment; 
           [0018]      FIGS. 8A and 8B  depict means for controlling the speed regulation as a function of temperature, which means are suited to the second embodiment; 
           [0019]      FIGS. 9 to 12  depict another embodiment of an articulation according to the invention. 
       
    
    
       [0020]    For the sake of clarity, in the various figures the same elements will bear the same references. 
       DETAILED DESCRIPTION 
       [0021]    An articulation  10  according to the invention comprises two articulation fittings  12  and  14  consisting, for example, of two machined cylindrical metal blocks. The articulation fittings  12  and  14  may be made lighter in weight by cavities when the application justifies so-doing, as is notably the case in the field of space. Each of the articulation fittings  12  and  14  is designed to be fixed to a corresponding element E 1 , E 2  by any suitable means such as screws or rivets at anchor points  15 . 
         [0022]    The articulation may be fitted with rolling bearings, ball swivels or plain bearings to allow the two articulation fittings  12  and  14  to move relative to one another. 
         [0023]    Each articulation fitting  12  and  14  comprises at least one flexible cylindrical surface,  22  and  24 , respectively, which surfaces are intended to roll one against the other as the articulation moves. In the example depicted, the diameters of the cylindrical surfaces  22  and  24  are the same. 
         [0024]    It is possible to produce the articulation with surfaces of any shape. One of the two surfaces is advantageously cylindrical so that it can roll over the other of the two surfaces. The term “cylindrical” is to be understood in the broadest sense. The radius of the cylinder may vary, for example as in the case of a cam or of a scroll. 
         [0025]    The flexible cylindrical surfaces  22  and  24  roll over one another to allow the elements E 1  and E 2  to move between two extreme positions which are offset by 180° from one another. When the elements E 1  and E 2  are flat elements, the first of these positions is known as the furled or storage position, which corresponds to the scenario in which the elements E 1  and E 2  are folded one against the other and parallel to one another, while the second position, known as the deployed position, corresponds to the scenario in which these elements are open and lying in the same plane.  FIGS. 1 and 3  correspond to the storage position and  FIGS. 2 and 4  correspond to the deployed position. 
         [0026]    In order to keep the flexible cylindrical surfaces  22  and  24  in permanent contact with one another as they roll against each other, the articulation  10  additionally comprises flexible metal strips  26  and  28  the ends of which are fixed to each of the articulation fittings so as to roll over the surfaces  22  and  24 . These strips are rigid in their plane and flexible outside of the plane. They are made, for example, of stainless steel. They are known as rolling strips or guide strips. 
         [0027]    By way of example, the articulation  10  comprises two central adjacent rolling strips  26 , positioned in the central part of the articulation fittings  12  and  14  and rolled in the same direction over the cylindrical surfaces  22  and  24  on each side of a mid plane common to these articulation fittings. A first end of each of the rolling strips  26  is fixed directly to the articulation fitting  12 . This attachment is performed for example using screws  18 . From this end, the strips  26  pass between the cylindrical surfaces  22  and  24  so that they are successively in contact with the surface  22  and then with the surface  24 . A movement of the articulation  10  in the direction of deployment therefore has the effect of unrolling the strips from one articulation fitting and at the same time rolling them up on the opposite articulation fitting. 
         [0028]    In the example illustrated, the articulation  10  comprises two other rolling strips  28 , fixed to the exterior parts of the articulation fittings  12  and  14 , near each of the strips  26  (which are themselves fixed to the interior parts of the articulation fittings  12 ,  14 ), likewise symmetrical with respect to a mid plane of the articulation fittings. The rolling strips  28  are wound in opposite directions to the strips  26  over the articulation fittings so that the strips  26  and  28  cross one another over cylindrical parts of the articulation fittings  12  and  14 . 
         [0029]    The drive for the articulation  10  is, for example, afforded by means of elastic belts, not visible in the various figures, and which cause automatic deployment of the articulation and lock it in the deployed position. One exemplary embodiment of such elastic belts is described in patent application FR 2 635 077. 
         [0030]    According to the invention, the articulation  10  comprises means for regulating the speed at which it deploys. These means for example are formed of a flexible duct  30  which may be secured to one of the articulation fittings, in this instance the fitting  14 , and compressed by the other articulation fitting  12 . The duct  30  is therefore secured to the cylindrical surface  24  and the compression of the duct  30  occurs at rolling point  32  of the two cylindrical surfaces  22  and  24 . 
         [0031]    The duct  30  comprises a restriction  34  situated between two zones  36  and  38  of the duct  30  which are separated by the rolling point  32 . In order to have good control over the dimensions of the restriction at the rolling point  32 , a groove  33  may be machined in both of the cylindrical surfaces  22  and  24 . The duct  30  contains a fluid the pressure of which increases ahead of the rolling point  32  as the articulation fittings  12  and  14  rotate. The difference in pressure between the two zones  36  and  38  increases with the speed at which the rolling point  32  shifts along the duct  30 . This difference in pressure generates a restrictive torque in the rotation of the two cylindrical surfaces  22  and  24 . Hence, the more the rotational speed increases, the more the resistive torque increases, thus allowing the speed at which the two articulation fittings  12  and  14  rotate relative to one another to be regulated. 
         [0032]    The fluid is, for example, liquid, and the speed is regulated by throttling the fluid in the restriction  34 . The liquid chosen is one that is capable of remaining liquid in all the storage and operating conditions of the articulation  10 . In the field of space, an alcohol based liquid that can be used in a temperature range of the order of −100° C. to +100° C. may be chosen. A fluid laden with microparticles or nanoparticles may also be used for its thickening and damping properties. For example, ferromagnetic particles, particles of titanium dioxide, or carbon nanotubes may be used. 
         [0033]    The restriction  34  may be a simple reduction in cross section realized in the duct  30 . It is also possible to place within the duct a foam or a filter that generates a pressure drop as the fluid moves in the duct  30 . 
         [0034]      FIG. 5  schematically depicts a first embodiment of means for regulating the speed of deployment of the articulation  10 . In this first embodiment, the restriction  34  is formed by the compression of the duct  30  at the rolling point  32  so that fluid can pass therethrough under stress. Ends  40  and  42  of the duct  30  are blocked. As the two articulation fittings  12  and  14  rotate on one another, which rotation is depicted by arrows  44  in the case of the fitting  12  and  46  in the case of the fitting  14 , the pressure of the fluid increases in the zone  38  as compared with that of the zone  36 . The fluid tends to balance out the pressures in the two zones  36  and  38  by flowing through the restriction  34 . A characteristic dimension of the restriction  34 , in this instance its bore section, is given by the distance that separates the axes of rotation of the two cylindrical surfaces  22  and  24  or by the depth of the cylindrical groove  33  when this groove is made in both of the cylindrical surfaces  22  and  24 . 
         [0035]      FIG. 6  schematically depicts a second embodiment of means for regulating the speed of deployment of the articulation  10 . In this second embodiment, the restriction  34  is separate from the rolling point  32  which, in the example depicted, completely nips the duct  30  and does not allow the fluid to pass. The two zones  36  and  38  are located between the restriction  34  and the rolling point  32 . The duct  30  forms a closed circuit. The fluid is driven through the duct  30  by the shifting of the rolling point  32  and this shifting is depicted by arrows  48 . 
         [0036]      FIGS. 5 and 6  depict the duct  30  nipped between the cylindrical surfaces  22  and  24  at the rolling point  32 . Near this point the duct  30  is straight. Alternatively, the duct  30  may be secured to and wound around one of the cylindrical surfaces, as depicted in  FIGS. 3 and 4 . 
         [0037]    The torque resisting the rotation of the two cylindrical surfaces  22  and  24  relative to one another is dependent on viscosity of the fluid. This viscosity changes with the temperature of the fluid. This is particularly a sensitive issue in the field of space where the amount of heat may be significant. In general, the viscosity is higher at low temperatures than at higher temperatures. The speed of the articulation  10  therefore increases with an increase in temperature. In order to reduce the effects that variations in temperature have on the speed regulation, the articulation  10  may comprise means for varying a characteristic dimension of the restriction  34  as a function of a variation in the viscosity of the fluid. 
         [0038]      FIGS. 7A and 7B  depict one example of these means suited to the first embodiment depicted in  FIG. 5 . More specifically, the two cylindrical surfaces  22  and  24  are formed of rollers  52  and  54  respectively, each secured to two wheels  56  and  58  in the case of the roller  52  and  60  and  62  in the case of the roller  54 . On one side of the rollers  52  and  54  the wheels  56  and  60  roll one over the other and on the other side of the rollers  52  and  54  the wheels  58  and  62  roll one over the other. The wheels  56  and  58  have the same diameter which is greater than that of the roller  52 . Likewise, the wheels  60  and  62  have the same diameter which is greater than that of the roller  54 . These differences in diameter make it possible to create a space  64  between the two rollers  52  and  54  in which space the duct  30  is nipped to form the restriction  34 . By choosing, for the rollers  52  and  54  on the one hand and for the wheels  56  to  62  on the other, materials the respective thermal expansion coefficients of which differ, it is possible to vary the separation of the rollers  52  and  54 , the dimensions of the space  64  and, therefore, the characteristic dimension of the restriction  34 . For example, the material chosen for the rollers  52  and  54  is one that has a thermal expansion coefficient that is higher than that of the material of the wheels  56  to  62 . Thus, at low temperature, as depicted in  FIG. 7B , the characteristic dimension of the restriction  34  is smaller than it is at high temperature as depicted in  FIG. 7A . 
         [0039]      FIGS. 8A and 8B  depict another example of means for varying a characteristic dimension of the restriction  34  which is suited to the second embodiment depicted in  FIG. 6 . More specifically, the restriction  34  may be partially obstructed by a needle valve  70 . The needle valve is assembled at a first end  72  of a support  74  secured to the duct  30 . The restriction  34  for its part is assembled with a second end  76  of the support  74 . As before, by choosing for the needle valve  70  a material the thermal expansion coefficient of which is higher than that of the support, the tip  78  of the needle valve  70  is made to shift and blocks off the restriction  34  to a greater or less extent according to the variations in the temperature of the fluid, as depicted at high temperature in  FIG. 8  in which the characteristic dimension of the restriction  34  is small by comparison with  FIG. 8B  which is at a lower temperature. 
         [0040]      FIGS. 9 to 12  depict another embodiment of an articulation comprising means for regulating the speed at which it deploys. 
         [0041]    The duct  30  is secured to the cylindrical surface  24 . In this example, a rolling wheel  80  rolls without slipping on the cylindrical surface  24 . The rolling wheel  80  has a circular cross section and a diameter smaller than that of the cylindrical surface  24 . In this example, it is possible to use a rolling wheel that is not of circular cross section, such as a variable radius cam for example.  FIGS. 9 to 12  depict the articulation in various positions starting out from the storage position in  FIG. 9  as far as the deployed position in  FIG. 12 .