Patent Publication Number: US-11383741-B2

Title: Flexible clamp

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Stage filing under 35 U.S.C. § 371 of International Application PCT/EP2020/058575, filed Mar. 26, 2020, which claims priority to U.S. Patent Application Ser. No. 62/824,006 filed on Mar. 26, 2019, and to Foreign Poland Patent Application Ser. No. P.429363 filed on Mar. 26, 2019, entitled “FLEXIBLE CLAMP”. 
    
    
     TECHNICAL FIELD 
     The present application relates to a field of railway couplers, trucks, and bogies. In particular it relates to an articulated joint connection element to be used in connection of adjacent vehicle bodies. 
     BACKGROUND ART 
     Publication EP 1 884 434 discloses a typical hinge for an articulated connection of adjacent vehicle bodies of a rail vehicle, in particular in cooperation with a bogie, wherein the said hinge comprises a first joint arm having an end section on the vehicle body side connected to a base plate of the first vehicle body and a front end section having a first joint head; a second joint arm having an end section on the vehicle body side connected to a base plate of the second vehicle body and a front end section having a second joint head configured complementary to said first joint head; a joint bearing comprising a pivot pin for the articulated connection of the first and second joint heads in a joining plane, wherein the pivot pin establishes a common pivoting axis for the hinge. The pivot pin is mounted by means of clamps, which are secured in place with screws. However, when such conventional clamps are used to mount the pivot pins, there exists a problem of insufficient fit between the clamp and the base, to which the clamp is attached. This results in gaps between the surfaces of the clamp and the flat ends of the base, when the clamp is secured to the base. These gaps lead to a fatigue stress on the screws, which are used to attach the clamp to the base. This may, in turn, result in breaking off of the screws. 
     DISCLOSURE OF INVENTION 
     The inventors of the present invention have invented a flexible clamp that can be used in an articulated joint connection for joining parts of a coupler, truck, or bogie of a rail car. The clamp of the invention secures a pin to a base yoke in an articulated joint connection. The clamp of the invention comprises a body configured for mounting to the base yoke, wherein the body comprises a pin contact part extending on one side of the body and configured to engage the pin, when the clamp is mounted to the base. The clamp of the invention comprises at least one recess or at least one aperture arranged in the body in a vicinity of the pin contact part, wherein said recess is configured for deforming said body upon engagement with the pin, when the clamp is mounted to said base yoke. The shape and size, as well as location of the recess or the aperture on the body of the clamp, are determined based on a strength calculation for the clamp. 
     In a preferred embodiment, the body of the clamp of the invention is provided with the aperture that extends across the body from a first side to a second side of the clamp. More preferably, the clamp comprises only one aperture, which enables deformation of the clamp. Most preferably, the aperture has a kidney-shaped cross section, which corresponds to the arced shape of the pin contact part engaging with the cylindrical pin when the clamp is mounted on the base. However, the aperture or recess can have any other shape, for example, it can have a trapezoidal, circular, triangular or rectangular cross section, provided that said aperture or recess provides the clamp with the desired susceptibility to deformation or flexing of the clamp. In general, the shape and size of the recess or aperture will correspond to the form of the pin contact part and the pin engaged by the clamp. For example, in case the pin has a conical shape the recess instead of aperture can be used to provide susceptibility to deformation or flexibility of the clamp. Alternatively, the clamp of the invention can be equipped with two, three or more recesses or apertures. The susceptibility for deformation of the clamp of the invention can be therefore provided by more than one recess or aperture or their combination. 
     In a preferred embodiment, the clamp of the invention is flexible and it is capable of undergoing elastic deformation as the clamp is secured to the base. Thus the recess or aperture in the body of the clamp is shaped and sized to control elastic deformation of the pin contact part. Moreover, the pin contact part of the clamp flexes and works as a spring when the clamp is screwed down and secured to top flat ends of the base yoke. In order to ensure that, the pin contact part has to have slightly bigger dimensions than the pin it is to engage with. Preferably, if the pin has a cylindrical shape, the pin contact part of the clamp is in a form of a concave surface defined by a cylinder segment, wherein the radius (r arc ) of the cylinder segment constituting the pin contact part of the clamp is greater than the radius (r pin ) of the pin. More preferably, the difference between r arc  and r pin  is in the range of 0.05 to 5.0 mm, most preferably by 0.1 to 2.0 mm. 
     The body of the clamp of the invention is defined by a top surface, a bottom surface, and side surfaces extending between the top surface and the bottom surface, wherein the side surfaces include a first side surface and a second side surface located on the opposite sides of the body. The pin contact part extends across the bottom surface of the body in the direction from the first side surface towards the second side surface, and the recess or the aperture is located above the pin contact part and extends across the body in the same direction as the pin contact part. In the most preferred embodiment, the clamp is provided with the aperture that extends from the first side surface to the second side surface. 
     In a preferred embodiment, when the clamp of the invention in the mounted position engages with a cylindrical pin, the pin contact part thereof has a form of a concave surface constituting a segment of a cylinder surface, preferably a cylinder having a circular or elliptic base, or a segment of an ellipsoid surface. In the most preferred embodiment the pin contact part has a form of a longitudinal cylinder segment. In this embodiment the aperture located in the body of the clamp has an elongated kidney-shaped cross section, wherein the longer dimension of the cross section extends in the manner corresponding to the concave surface of the pin contact part. 
     The clamp of the invention is provided with the means to secure the clamp to the base. In a preferred embodiment it comprises securement holes extending across the body for receiving screws for securing the clamp to the base yoke. However, the clamp of the invention can be secured to the base by any other suitable means. 
     Due to a fact that the clamp of the invention undergoes deformation when it is mounted to the base, the clamp body adheres to the flat surface of the base yoke. That way no gap is formed between the bottom surface of the clamp and the flat surface of the base yoke and no strain is exerted on the screws, which secure the clamp to the base yoke. Therefore the clamp in accordance with the present disclosure reduces or eliminates the fatigue stress on the screws used to attach the clamp to the base. 
     The clamp of the invention may be made of any suitable metal including steel or other iron alloys, aluminum and cast iron. 
     The invention also provides an articulated joint connection and a railway coupler comprising the clamp according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject of the invention was illustrated in a drawing, in which: 
         FIG. 1  shows a perspective view of the clamp according to the invention. 
         FIG. 2  shows a perspective view of the coupler comprising the clamp according to the invention. 
         FIG. 3A  shows a front view of the coupler comprising the clamp according to the present invention, and 
         FIG. 3B  presents an enlarged view of a part of the coupler (section B) comprising the clamp according to the present invention. 
     
    
    
       FIG. 1  presents a preferred embodiment of the flexible clamp of the invention for securing a pin  30  to a base yoke  221  in an articulated joint connection  20 . The flexible clamp  10  comprises a T-shaped body  11  comprising a head part  12  and a shank part  13 . The body  11  of the clamp  10  has a top surface  14  extending on the top of the head part  12  and a bottom surface  15  extending below the head part  12 . The shank part  13  of the body  11  extends from the bottom surface  15  in a form of a protrusion. The side surfaces  16  defining the body  11  of the clamp  10  extend from the top surface  14  throughout the head part  12  and the shank part  13  of the body  11 . The side surfaces  16  comprise a first side surface  161  and a second side surface  162  located on the opposite sides of the body  11 , on the front and back of the T-shaped body  11 , accordingly. These first  161  and second  162  side surfaces are parallel to each other and perpendicular to the top surface  14  of the body  11 . 
     The body  11  of the clamp  10  is provided with a pin contact part  151  for engaging the pin  30 , when the clamp  10  is secured to the base yoke  221 . The pin contact part  151  has a form of a longitudinal cylinder segment (i.e. a cylindrical surface segment) extending across the shank part  13  in the direction from the first side surface  161  to the second side surface  162 . In this manner the pin contact part  151  forms a concave surface (i.e. an arc), which corresponds to the cylindrical shape of the pin  30 . The radius of the cylinder, a segment of which forms the pin contact part  151  of the clamp  10 , is denoted in  FIG. 3B  as r arc . The said cylinder is substantially coaxial with the pin  30 , which is in a form of a solid cylinder. The pin contact part  151  of the clamp  10  is configured to elastically deform or flex against the pin  30  as the clamp  10  is screwed down and secured to top flat ends of the base yoke  221  with screws  40 . 
     The body  11  is provided with one aperture  17  located above the pin contact part  151 , wherein said aperture  17  extends across the body  11  of the clamp  10  from the first side surface  161  to the second side surface  162 . The aperture  17  has an elongated kidney-shaped cross section, wherein the longer dimension of the cross section extends in the manner corresponding to the concave surface cross section of the pin contact part  151  (i.e. in the direction across the shank part  13  of the body). This aperture  17  allows for elastic deformation of the clamp  10  when the clamp  10  is being secured to the base yoke  221  with the screws  40 . This deformation ensures that the bottom surface  15  of the head part  12  of the body  11  adheres to the flat ends of the base yoke  221 . This way the strain exerted on the screws  40  connecting the clamp  10  to the base yoke  221  is eliminated. 
     Finally, body  11  is also provided with two securement holes  18  for receiving screws  40  for securing the clamp  10  to the base yoke  221 . The securement holes  18  extend across the head part  12  of the body  11  from the top surface  14  to the bottom surface  15 . The screws  40 , which lock the clamp  10  in place on the base yoke  221  are inserted in the securement holes  18 . 
       FIGS. 2 and 3  present a coupler  20 , in which the flexible clamp  10  of the invention is used to secure the pin  30  to the base yoke  221  of a coupler  20 . As shown in  FIGS. 2 and 3  the pin  30 , which is in a form of a solid cylinder with the radius denoted as r pin , connects a joint between a first part  21  and a second part  22  of the coupler  20 . The pin  30  is thread through an opening defined by walls of the first part  21  of the coupler  20 . The first part  21  pivots axially around the pin  30 . The pin  30  is secured to a curved section of a base yoke  221  of the second part  22  of the coupler  20 . The pin  30  is secured to the curved sections of base yoke  221  by the clamp  10 . 
     By providing the aperture  17  in the body  11 , the clamp  10  undergoes elastic deformation while being secured to the base yoke  221  by the means of the screws  40 . At the same time, the clamp material is not weakened by the presence of the aperture  17 , so that the proper functioning of the clamp  10  is not affected in any way. As the clamp  10  is secured to top flat ends of the base yoke  221 , the pin contact part  151  of the clamp  10  also elastically deforms or flexes against the pin  30  as the clamp  10 . This deformation or flexure depends on a location, shape, and size of the aperture  17 . Thus the aperture  17  is shaped and sized to control elastic deformation of the pin contact part  151  of clamp  10 . Due to this deformation the bottom surface  15  of the clamp body adheres to the flat surface of the base yoke  221 . That way no gap is formed between the bottom surface  15  of the clamp and the flat surface of the base yoke  221  and no strain is exerted on the screws  40 , which secure the clamp  10  to the base yoke  221 . 
     The pin contact part  151  of the clamp  10  flexes and works as a spring when the clamp  10  is screwed down and secured to top flat ends of the base yoke  221 . To allow the pin contact part  151  to deform, the radius r arc  of the cylinder, a segment of which forms the pin contact part  151 , is greater than the radius r pin  of the pin  30 , wherein the difference in the radius length is in the range of 0.1 to 2 mm, as depicted by the following equation:
 
 r   arc   =r   pin +0.1to 2.0 mm
 
     The flexible clamp of the invention when used to secure the pin  30  to the base yoke  221  reduces or eliminates fatigue stress on the screws  40  used to attach the clamp  10  to the base yoke  221 . This is achieved by securing flush the flexible clamp  10  to top flat ends of the base yoke  221  with full contact between the top flat ends of the base yoke  221  and the bottom surface  15  of the clamp body  11 . 
     REFERENCES 
     
         
           10 —clamp 
           11 —body of the clamp 
           12 —head part of the body 
           13 —shank part of the body 
           14 —top surface of the body 
           15 —bottom surface of the body 
           151 —pin contact part 
           16 —side surfaces of the body 
           161 —first side surface of the body 
           162 —second side surface of the body 
           17 —recess/aperture 
           18 —securement hole 
           20 —articulated joint connection/coupler 
           21 —first part of the articulated joint connection/coupler 
           22 —second part of the articulated joint connection/coupler 
           221 —base yoke of the second part of the articulated joint connection/coupler 
           30 —pin 
           40 —screw