Abstract:
A flexible control device of the push-pull type for mechanical power transmissions; the device comprises a flexible member provided by a plurality of cup-shaped elements having a central hole; a pull cable is passing through the aligned holes of the cup-shaped elements which freely slide within a sheath. Each cup-shaped element comprises semi-spherical inner surface, and a partially spherical outer surface meshing with a cylindrical outer surface along the front edge of the cup-shaped element. The device is suitable for transmitting high pushing-pulling forces for the remote control of mechanical members and devices.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention refers to mechanical control systems, and more in particular is directed to a control device of the push-pull type, capable of transmitting high pushing and pulling forces between a linear or rotary actuator, such as a pneumatic or hydraulic cylinder or an electric motor, and a mechanical member or device which in turn can be provided with linear or rotary motion, regardless of the type of actuator used.  
           [0002]    The control device according to this invention is particularly suitable for use with remote control systems, in which a movement transmitting line can extend on a surface or in the space along any rectilinear, curved and/or circular path, of any length and in any desired direction.  
         STATE OF THE ART  
         [0003]    Flexible or articulated control devices for a remote controlled movement transmission are widely known and are used in various mechanical fields, for example in the automotive and nautical fields, on machine tools and for other applications; in general, these systems make use of articulated chains, variably composed cables and/or ropes, if necessary sliding in guide sheaths for guiding the cable.  
           [0004]    In general, flexible or articulated push-pull control devices of the aforementioned type are prevalently capable of exerting pulling forces, also of a high value, whereas their pushing action proves to be either inexistent or wholly irrelevant due to the flexibility of the connecting cable, rope or chain which extends between the power actuator and the controlled device.  
           [0005]    For example, with a usual flexible push-pull transmission device comprising a metal cable sliding within an outer sheath, possibly strengthened by a wire helically wound around the sheath, the amount of thrust that can be exerted generally proves to be extremely limited since, at the most, it can range from 10 to 20% of the pulling force that can be exerted by the same cable. In addition, in flexible transmissions of this kind, the amount of thrust or pushing force is in any case conditioned by the combined bending and compressive stress acting on the inner cable, as well as by the flexibility of the sheath and the inner cable whose radius of curvature, in general, must be of a considerably high value.  
           [0006]    Consequently, with the articulated or flexible push-pull devices of the known type it is not possible to obtain remote control systems which extend on a surface or in space along any transmission line, and which at the same time makes it possible to exert pushing and pulling forces of high value, wholly independent from one another, as well as from the path and length of the transmission line itself.  
           [0007]    To partially remedy to the problems involved by flexible push-pull devices of the known type, has been suggested to use a cable in combination with profiled or ball shaped members, ad described for example in DE 43 08 181, EP 0 301 453, GB 2178505, FR 685616 and DE 195 34 643; nevertheless these push-pull devices make use of pushing members of large dimensions, which are to be manufactured by costly machining operations and again are limiting any possibility to extend along any transmission line on a surface and/or in the space with extremely limited radiuses of curvature or bending angles without affecting the operation of the same device.  
           [0008]    Another inherent problem in the flexible control system of the known kind consists in that the pulling cable is not guided at its ends over the entire working stroke, and is consequently subjected to considerable fatigue stress, by bending, in the attachment point to the actuator and to the controlled mechanical member, resulting in its deterioration or rupture after a number of operations.  
           [0009]    For these reasons, it is currently necessary to use rigid force-transmission system, or to connect an actuator directly and in close proximity to the controlled device or member to be operated.  
           [0010]    For example, by positioning a hydraulic cylinder close to the controlled member in a machine tool, consequently involves considerable problems in terms of consume of space, especially whenever high powered actuators must be used, due to the fact that in general they are considerably larger in dimensions than the working member or device to be controlled.  
           [0011]    In an attempt to solve the problems involved by previously known devices, EP 1 059 462 suggests the use of a push-pull device of which the present invention constitutes an improvement. In particular EP 1 059 462 suggests a push-pull device in which the pushing members are suitably guided over the entire working stroke; nevertheless the pushing members are again in the form of ball or differently shaped members of substantial length or thickness, which do not allow to conform to any force transmitting line having a large amount of flexibility and an extremely reduced bending radius; furthermore the pushing member are again to be manufacture by costly machining operations.  
         OBJECTS OF THE INVENTION  
         [0012]    The general object of this invention is to provide a flexible control system, of the push-pull type, capable of obviating the above mentioned problems inherent in the flexible or articulated control systems of the known kind.  
           [0013]    More in particular, one object of this invention is to provide a flexible control device of the push-pull type, for power transmissions, whereby it is possible to exert both pushing and pulling forces of a high value wholly independent from one another.  
           [0014]    A further scope of this invention is to provide a control device, as mentioned previously, which can be used, in particular, for mechanical remote control, in which the force transmitting line can extend for any length on a surface and/or in the space, making it possible to exert pushing and/or pulling forces along rectilinear, curved and/or circular paths with extremely limited radiuses of curvature or bending angles, without negatively affecting the working stroke and the amount of the exerted forces.  
           [0015]    A still further object of the invention is to provide a highly versatile and reliable flexible control device which, at the same time, comprises very few cup shaped members which are obtained by simple operations.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0016]    All the above can be achieved by means of a control device of the push-pull type, comprising a flexible control member substantially provided by a plurality of face to face arranged cup-shaped elements having a front edge, longitudinally aligned and in close contact with one another, and a pull cable passing through central holes in the aforesaid cup-shaped shaped members, said cup-shaped elements having partially spherical inner and outer surfaces and being freely sliding within an outer guide sheath, wherein each cup-shaped element comprises a coining shaped semi-spherical inner surface, and a coining shaped partially spherical outer surface meshing with a cylindrical surface close to the front edge. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    These and further objects and features of a flexible control device according to the invention, will be more clearly evident from the following description with reference to the accompanying drawings, in which:  
         [0018]    [0018]FIG. 1 shows a plan view of a push-pull control device according to the invention, suitable for linear movements;  
         [0019]    [0019]FIG. 2 shows an enlarged sectional detail of the device of FIG. 1 along a linear portion;  
         [0020]    [0020]FIG. 3 shows an enlarged cross-sectional view of a cup-shaped element. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    With reference to figures from  1  to  3 , a description is given hereunder of a preferred embodiment of a control device according to the invention, and one of its possible applications.  
         [0022]    In FIG. 1, reference  10  indicates a linear actuator, for example a pneumatic or hydraulic cylinder, connected to a member  11  to be controlled, by means of the push-pull control device comprising a flexible force transmission member according to the invention, indicated by reference  12 .  
         [0023]    More precisely, the rod  10 ′ of the cylinder  10  is connected to the flexible member  12  of the control device, by means of a slider  13  which runs along a guide  14  capable of guiding the slider  13  and an end portion  12 ′ of the same flexible force transmitting member  12  along the entire working stroke.  
         [0024]    Likewise, the other end portion  12 ″ of the flexible member  12  of the control device, is connected to the controlled member  11  by means of a second slider  15  moving along a guide  16  which also extends for the entire length of the working stroke.  
         [0025]    As shown in the same FIG. 1, the flexible member  12  can extend along any path defining a transmission line for transmitting movements, having rectilinear and/or curved portions, both on a plane or a surface and in the space, according to need.  
         [0026]    The basic features of the control device according to the invention will be now described in greater detail hereunder with reference to FIGS. 2 and 3 of the accompanying drawings.  
         [0027]    As shown in the aforesaid figures, and in FIG. 1, the flexible force transmitting member  12  of the control device, substantially comprises two structurally independent, albeit functionally integrated, portions; more precisely, it comprises a first portion  17  designed to exert a pushing action or force, and a second portion  19  designed to exert a pulling action or force.  
         [0028]    As shown in the detail of FIGS. 2 and 3, the pushing portion of the flexible control device is provided by a plurality of cup-shaped articulated elements  17  having semi-spherical inner and outer coupling surfaces which are maintained in close contact with one another so as to allow any relative angular and/or rotational movement between one pushing element and another, both in the space and on any desired plane or surface.  
         [0029]    Each individual pushing element  17  is provided with a central hole  18  to allow the passage of a pull member  19  consisting for example of a metal wire, or of synthetic fibers or any other material, or combination of suitable materials, the ends of which are connected to the sliders  14  and  15 , respectively, by means of a clamp  20 .  
         [0030]    The flexible control member  12 , comprising the pushing elements  17  and the pull cable  19 , is suitably tensioned by means of the clamps  20  to maintain the articulated pushing elements  17  in close contract with one another, inside a sliding and reaction sheath  21 , the ends of which are suitably fastened to the guides  14  and  16 , for example by means of a screw nut  22  or in any other suitable way.  
         [0031]    [0031]FIG. 3 of the accompanying drawings shows an enlarged cross-sectional view of a push element  17  constituting part of the flexible control member  12  according to the invention.  
         [0032]    As shown in FIG. 3, the push element  17  comprises a semi-spherical inner surface  23  having a pre-established radius of curvature and its center on the longitudinal axis of the through hole  18  for passage of the pull cable  19 ; the cup-shaped element  17  also comprises a partially spherical outer surface  24  which meshes with a cylindrical surface  25  close to the front edge.  
         [0033]    Since the outer partially spherical surface  24  of each push element  17  is designed to be in contact in an articulated mode with the inner semi-spherical surface  23  of an adjacent push element  17 , the partially spherical surface  24  also presents a radius of curvature corresponding to that of the inner semi-spherical surface  23 , whose center also lies on the longitudinal axis of the hole  18 .  
         [0034]    The cylindrical surface  25  may be of any desired width, provided it is capable of allowing a wide angular and/or rotational movement or articulation between adjacent cup-shaped elements  17 , and in any case sufficient to allow very sharp bends of the flexible control member, of up to 360° and over, thereby also creating possible spiral turns.  
         [0035]    In general, as shown, the width of the cylindrical surface  25 , in the direction of the axis of the hole  18 , must be smaller than the maximum thickness of the semi-spherical wall of the member  17  in the region of the central hole  18 . For example, for cup-shaped elements having an external diameter of the cylindrical surface  25  equal to 5.6 mm, and a diameter of the central hole equal to 2.3 mm on the inner surface  26 , the maximum thickness of the wall can be 1 mm, with a cylindrical surface  25  having a length equal to or smaller than 0.8 mm.  
         [0036]    In FIG. 3 it can also be seen that, in order to prevent possible interference between the inner surface of the hole  18  and the cable  19  that passes through it, especially in the condition of a minimum radius of curvature of the flexible member  12 , the hole  18  presents a conical shape converging towards the inner semi-spherical surface  23 . Also in FIG. 3 it can be seen that the thickness of the wall of the cup-shaped element  17  is progressively reducing from the hole  18  towards the front edge of the surface  25 . This has been made possible by manufacturing the cup-shaped elements  17  by coining, starting from a metal disk of appropriate diameter and thickness, provided with a central hole.  
         [0037]    The use of the coining technology, as compared to the conventional machining methods, makes it possible to obtain cup-shaped elements wholly identical to one another with the utmost precision, thereby making the entire device more reliable.  
         [0038]    From what has been described and shown in the accompanying drawings, it will consequently be clear that what is provided is a control device of the “push and pull” type, to connect an actuator to a control member, which utilises a particular flexible member for transmitting the movement substantially comprising a pull cable which extends within a plurality of cup-shaped push elements articulated to one another, which carry out, in a correlated fashion, differentiated functions of pushing and pulling, making the system totally independent from any type and length of the transmission path, and from the required working stroke.  
         [0039]    It is understood, however, that what has been described and shown with reference to the accompanying drawings has been given purely by way of example in order to illustrate several embodiments and possible applications. Consequently, other modifications or variations may be made compared to what has been shown, or the device itself may be used in other different fields of application, without departing from the scopes of the enclosed claims.