Patent Publication Number: US-6713223-B2

Title: Device for articulated connection between a control element and a control rod with a ball head

Description:
DESCRIPTION OF THE PRIOR ART 
     This invention relates to a device for articulated connection between a control element and a control bar with a ball head according to the characterising definition of claim 1. In particular, the invention relates to a device designed to provide an articulated connection between a control element in the form of a pedal and a piston rod attached to a piston of a hydraulic cylinder. 
     Such devices are used for example in motorized vehicles where it is necessary to connect a pedal hinged to a pedal box to a piston rod with a ball head at its end to ensure its efficient operation, the other end of the piston rod being hinged at the piston or a clutch control or main brake cylinder. At the same time, compressive or pulling forces must be transmitted during a working cycle between the parts such as the pedal and the piston rod moving in their angular position in relation to each other depending on whether the pedal is being pressed down or released. 
     European patent specification EP 0 229 350 B1 discloses a generic articulated connection having a one-piece insert part which connects a pedal with a ball head of a piston rod ensuring efficient operation. The insert part made of plastic is clipped here into a part of the pedal which is approximately U-shaped and has a bearing socket to hold the ball head. The bearing socket has an undercut into which the ball head can be pressed as if it were a snap-in connection and serving the purpose of retaining the ball head in the bearing socket during operation. The insert part has a hopper-like inlet area at the entry to the bearing socket. During assembly of the known articulated connection, the ball head is pressed through the entry section into the bearing socket by forcing the undercut. The piston rod extends through the entry area when this articulated connection is in its assembled condition or in operation. 
     A disadvantage of this state of the art can be seen in the fact that there is a danger, particularly at high temperatures, of the ball head permanently deforming the undercut at the bearing socket when a higher tension load is applied to the piston rod, possibly resulting in unacceptable play at the controls or, in the worst instance, in the ball head even being forced out of the bearing socket when the pedal is moved back rapidly and uncontrollably from its control position to its resting position or when it is pulled by the pedal. 
     The purpose of the invention is to create a device of the simplest possible design, to provide an articulated connection between a control element and a control rod with a ball head guaranteeing a reliable connection between the control element and a control rod which would be permanently backlash-free or have little backlash. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a device to provide an articulated connection between a control element and a control rod with a ball head, the device having a main body, attachable at the control element, that envelops a locator section, for positive location of the ball head and that has an opening section, through which the control rod extends when the device is assembled; wherein the locator section is in two parts, the main body forming one of said parts and having a joint duct located outside the opening area, into which the ball head can be introduced, the other part of the locator section being formed by a molding insertable in the joint duct. 
     In particular the locator section enclosed by the main body locatable at the control element on a device of a generic type is in two parts, the main body forming one part into which the ball head can be introduced through a joint duct located outside the opening area surrounding the piston rod in operation, while a molding insertable in the joint duct forms the other part of the locating section. 
     In this design of articulated connection, the ball head is enveloped to a greater degree than according to the known state of the art; in other words, it can be said that the size of the undercut at the locator section provided for positive location of the ball head in the direction of the opening area, that is in the direction in which the main part of the control forces are acting in operation, can be made larger. This is not hindered by the assembly of the articulated connection because the undercut at the locator section in the direction of the opening area does not have to be overcome when joining the ball head since it is on the other hand possible to join the ball head to the main body through the joint duct which is outside the opening area before the locator section is completed by inserting the molding. Therefore, the direction in which the ball head is joined to the main body is different from the direction in which most of the operating forces act, that is different than in the case of the state of the art referred to. 
     As a result, the mechanical capacity of the articulated connection is improved and greater forces can be transmitted than in the case of the abovementioned state of the part, particularly at higher temperatures, without the main body and/or the molding suffering permanent deformation or the ball head being pulled out of the main body which would be unacceptable. This guarantees absence of backlash or very little backlash at the articulated connection and greater safety against pulling out. 
     The main body and the molding which form parts of the locator section for the ball head are each provided with a spherical cup to produce surface contact between the ball head and the locator section which would be almost non-wearing. 
     In principle, it is possible to provide the part of the locator section positively locating the ball head on the main body side with a small undercut in the direction of the joint duct so that the ball head can be snapped into the main body when assembling the articulated connection, before inserting the molding into the joint duct. However, a design is preferred according to which the inside dimension of the joint duct in the main body is greater or the same as the diameter of the ball head at each point of the joint duct. This allows on the other hand joining the ball head to the main body to advantage mainly without applying a force. On the other hand, making the injection cast main body preferably from plastic is simplified according to claim 12 because it is not necessary to release the main body from the mold by force and thus no specific mold release sequence needs to be observed. In addition, a design of the locator section for the ball head on the main body side without an undercut in the direction of the joint duct allows the base body to be released economically from the mold immediately after the injection casting process. If there were an undercut at the main body in the direction of the joint duct, the injection cast main body would first have to cool down for a certain time before it could be released from the mold; otherwise, there would be a risk of permanently deforming the undercut while releasing a warm main body from the mold, possibly resulting in unacceptable backlash in the articulated connection during operation. 
     The molding at the main body can be fixed by means of a snap connection. This feature facilitates assembly of the articulated connection because the molding inserted into the joint duct of the main body cannot drop out of the joint duct of the main body when joining the main body to the control element. The joint duct can have a suitable recess for positive location of the molding, this recess having a section protruding to the inside at the open end of the joint duct which, as part of the snap connection, engages the molding towards the back in its inserted position in the joint duct. 
     The main body may be provided with locating lugs clicking into the recesses in the control element to hold the main body positively at the control element. The main body of this design makes the articulated connection simple and economical to assemble. 
     The main body, viewed from above, may be generally U-shaped, having a base in which part of the locating section is shaped to provide a positive hold for the ball head and two arms extending away from the base which have the locating lugs on them and delimit the opening area for the control rod. The main body can be easily set to a defined position at the control element if the main body base is provided with a traverse slot on the side away from the locating section for positively locating the ball head. 
     The main body and/or the molding may be provided with protrusions, the purpose of which is to compensate any tolerances to advantage. Assembling the articulated connection is made easier if each of the protrusions at the main body and/or the molding has a bevel which is on the side facing the control element when joining it to the control element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:— 
     FIG. 1 is a perspective view of a device providing an articulated connection between a piston rod with a ball head and a pedal (not shown here), the ball head being located in a part of a main body forming part of a locator section for positive location of a ball head, without the molding which completes the locating section not yet inserted into the main body; 
     FIG. 2 is a perspective view of the device in FIG. 1, with the molding inserted into the main body to complete the locating section; 
     FIG. 3 is a longitudinal section through the device shown in FIG. 2, with a partly shown pedal inserted into a locating section; 
     FIG. 4 is a view of the main body of the device in FIGS. 1 to  3  to a different scale, shown in perspective; 
     FIG. 5 is a longitudinal section through the main body shown in FIG. 4; 
     FIG. 6 is a plan view of the main body shown in FIG. 4; 
     FIG. 7 is an enlarged section showing part of the main body along line A—A in FIG. 6, rotated clockwise through 90° in the drawing plane; 
     FIG. 8 is a view from below of the main body shown in FIG. 4; 
     FIG. 9 is an enlarged plan view of the molding of the device shown in FIGS. 1 to  3 ; 
     FIG. 10 is a front view of the molding shown in FIG. 9; 
     FIG. 11 is an enlarged view of detail X in FIG. 10; 
     FIG. 12 is a section through the molding along line B—B in FIG. 9, and 
     FIG. 13 is a view from below of the molding shown in FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 to  3  show a device  10  for an articulated connection between a pedal, not shown in detail, and a piston rod  12  with a ball head  14 . The device  10  has a main body  16  which can be fixed at the pedal in a way described in greater detail below. The main body  16  encloses a locator section generally marked  18  in FIG. 3 which serves the purpose of positively holding the ball head  14  and has an opening area  20  through which the piston rod  12  extends when the device  10  is in assembled condition or in operation. It is essential that the locator section  18  is in two parts, as will be explained in greater detail, whereby the main body  16  forms one part into which the ball head  14  can be introduced through a joint duct generally marked  22  in FIG. 1, located outside the opening area  20 , or offset in relation to the opening area  20 , while a molding  24  which can be inserted into the joint duct  22  forms the other part of the locator section  18 . 
     FIGS. 4 to  8  show the injection molded main body  16  from a plastic such as POM (polyoxymethylene) in detail. The main body  16  as seen from above in FIG. 6 is mainly U-shaped with a base  26  in which one part of the locating section  18  designed to provide positive location for the ball head  14  is in the form of a spherical cup section  28 , two mirror-like opposite arms  30  extending from the base  26  delimiting the opening area  20  on the side. Seen in section, the main body  16  has a generally rectangular outer outline with rounded corners formed by one top flat surface  32 , one-bottom flat surface  34 , two flat side faces  36  and rounded edge sections  38 . On the side of the base  26  away from the spherical cup section  28 , the main body  16  has a flat end face  40  adjoining the top face  32 , the bottom face  34  and the side face  36  over the bevels  42  which facilitate joining the main body  16  to the pedal. Starting from the end face  40 , the base  26  of the main body  16  is provided with a transverse slot  44  in the center in one plane with the joint duct  22  and serving the purpose of positioning the main body  16  at the pedal. 
     The arms  30  of the main body  16  carry on their outside faces facing away from each other locating lugs  46  adjoining the side faces  36 , clicking into the recesses in the pedal, not shown here, with the arms  30  flexibly deforming, to hold the main body  16  at the pedal. With regard to the pedal, which is preferably made of steel plate or plastic, it must be mentioned at this point that it has a locator for the main body  16  with a rectangular section which is delimited by the side cheeks of the pedal and the stays  48  extending between them, indicated in FIG. 3, apertures for the locating lugs  46  being provided in the side cheeks. A section extending between the stays  48  of the pedal and engaging into the transverse slot  44  of the main body  16  to hold it in positive location when the device  10  is assembled, is not shown in FIG. 3 for the sake of clarity. 
     As can be seen in particular in FIGS. 6 and 8, the arms  30  of the main body  16 , narrower towards their ends are slightly beveled on the inside, at the transition between the side faces  36  and the locating lugs  46 , to enlarge the opening area  20  for the piston rod  12 . FIGS. 5 and 6 show the ball head  14  and the angle ranges a and b within which the center axis of the piston rod  12  moves when the articulated connection is in operation, viewed in the direction of the two planes at right angles to each other. As can be seen from FIG. 6, the piston rod  12  cannot swing beyond the operating angle range b, being prevented from doing so by the arms  30  of the main body  16 . However, it is possible to swing the piston rod  12  beyond the operating angle range a, e.g. for assembly purposes, because in the example of the design shown the main body  16  is provided at its bottom face  34  with an appropriate longitudinal slot  50  (FIGS. 3,  5  and  8 ), and so is the molding  24  with the longitudinal slot  52  (FIGS. 3,  9  and  13 ). 
     According to FIG. 5 in particular, the joint duct  22  for the ball head  14  extends up to the spherical cup section  28 , starting from the top face  32  of the main body  16 . The joint duct  22  has a recess  54  in its top area, shown in FIG. 5, for positive location of the molding  24 . This recess  54  is delineated on the side by a cylindrical surface section  56  with a circumferential angle greater than 180° extending at right angles to the top face  32  of the main body  16 , two adjacent flat side faces  58  opposite to each other which include an angle and also extend at right angles to the top face  32 , and, as in FIG. 5, on the left by two bevels  60  in one plane, extending at an angle to the top face  32 . A cylindrical surface section  64  adjoins the recess  54  in the direction of the spherical cup section  28  over a shoulder  62  extending parallel to the top face  32 , its centerline being marked by a dot and dash line in FIG. 5 extending parallel to the bevels  60 , at an angle to the top surface  32 . The diameter of the cylindrical surface section  64  in the version of the design shown is mainly the same as the diameter of the ball head  14  or the spherical cup section  28  so that the inside diameter of the joint duct  22  in the main body  16  at each point of the main body  22  is the same or larger than the diameter of the ball head  14 . As shown in FIGS. 5 and 6, the plane of the shoulder  62  passes through the cylindrical surface section  64  at an angle c which is smaller than 90° resulting in an elliptical opening section  0 , the smaller axis of which is the same as the diameter of the ball head  14 . It is obvious that the ball head  14  can therefore be joined to the spherical cup section  28  through the joint duct  22  without applying force, that is, without overcoming an undercut. 
     The molding  24  shown in greater detail in FIGS. 9 to  13  is also injection molded from a plastic such as POM and has a spherical cup section  66  for forming the other part of the locator section  18  for the ball head  14 , the radius of which is also equal to the radius of the ball head  14 . The molding  24  which is mainly crescent-shaped in the views in FIGS. 9 and 13 due to the longitudinal slot  52 , has a flat top face  68  shown in FIG. 10 and a flat bottom face  70  parallel to it, in which the spherical cup section  66  is formed. As shown in FIG. 3, the vertical distance between the top face  68  and the bottom face  70  of the molding is slightly smaller than the distance between the top face  32  and the shoulder  62  of the main body  16  so that there is a small gap between the bottom face  70  of the molding  24  and the shoulder  62  of the main body  16  when the device  10  is in assembled condition in which the spherical cup sections  28  and  66  rest with their surfaces at the ball head. 
     The molding  24  also has a cylindrical surface section  72 , adjoining side faces  74  which together include an angle and the bevels  76  closing the molding  24  to the left in FIGS. 10 and 13, consistent with the recess  54 . The molding  24  has such dimensions that when the device  10  is assembled, the cylindrical surface section  56  of the main body  16  and the side faces  74  of the molding  24  rest at the side faces  58  of the main body  16  while the bevels  76  of the molding  24  are at a slight distance away from the bevels  60  of the main body  16 , as shown by a slightly thicker line in FIG.  3 . 
     In the version of the design shown, the molding  24  is fixed to the main body  16  by means of a snap connection. For this purpose, to ensure positive location for the molding  24 , the recess  54  provided at the main body  16  has at the open end of the joint duct  22  a profile  78  protruding inwards, shown in an enlargement in FIG. 7, formed by two curved sections, as in FIGS. 1,  4 ,  5  and  6 , arranged mirror-like opposite to each other and extending from the cylindrical surface section  56  to the side faces  58  of the recess  54 . With the molding  24  inserted into the joint duct  22  of the main body  16 , the profile  78  engages behind the molding  24 , the molding  24  being provided for this purpose with a chamfer  80  between the top face  68  and the cylindrical surface section  72  or the side faces  74 . A corresponding chamfer  82  is provided between the bottom face  70  and the cylindrical surface section  72  or the side faces  74  of the molding  24 . 
     Furthermore, the main body  16  and the molding  24  of the illustrated example of design has protrusions or projections  84  at suitable places on the top face  32  and the bottom face  34  or the top face  68 , which serve the purpose of compensating any tolerances by flexible or plastic deformation. As the enlargement in FIG. 11 in particular shows, each of the protrusions or projections  84  has a bevel  86  which is on the side facing the pedal during the joining operation, to facilitate joining. According to FIG. 3 showing the assembled device  10 , the protrusions  84  are pressed together with the pedal stays  48 . 
     Finally, it must be noted with regard to the piston rod  12  made of steel or plastic, partly shown in FIGS. 1 to  3 , that it is attached by means of an articulated joint at the end away from the ball head  14  at a hydraulic piston not shown here, and provided with two flanges  88  between its ends, the flange facing away from the ball head  14  serving as a stop to limit the stroke of the hydraulic piston in the thrust direction, a bellows, not shown here, of a hydraulic cylinder, not shown here either, being attached between them. 
     To assemble the device  10  described above, the ball head  14  of the piston rod  12  is introduced through the joint duct  22  into the main body  16  in the main without applying a force, until the ball head  14  comes into contact with the face of the spherical cup section  28  of the main body  16 . The molding  24  is then introduced into the recess  54  of the joint duct  22  until the spherical cup section  66  of the molding  24  comes into contact with the face of the ball head  14 . In the main, the molding  24  simultaneously engages behind the profile  78  of the aperture  54 . 
     The unit preassembled in this way, comprising the main body  16  and the molding  24 , is then pushed, together with the ball head  14  of the piston rod  12  held between them, from the left in FIG. 3 into the recess between the stays  48  of the pedal, until the section between the stays  48  of the pedal, not shown here, engages into the transverse slot  44  of the main body  16  and the main body  16  abuts with its end face  40  in the pedal recess. During this push-in movement, the arms  30  of the main body  16  spring towards each other due to the locating lugs  46  coming into contact with the side cheeks of the pedal, until the locating lugs  46  engage the recesses, not shown here, in the side cheeks of the pedal. 
     It is evident that the locator section  18  providing positive location for the ball head  14  can transmit thrust or traction forces from the pedal to the piston rod  12  or from the piston rod  12  to the pedal, the ball head  14  being supported on the locator section  18 . The forces transmitted at the same time to the main body  16  directly through the ball head  14  or indirectly through the molding  24  are for their part backed up at the pedal in the traction direction over the locating lugs  46  and in the thrust direction over the end faces  40  of the main body  16 . 
     To dismantle the device  10 , the arms  30  of the main body  16  must be pressed inwards until the locating lugs  46  are released from the recesses in the pedal. The device  10  can then be pulled by the piston rod  12  out of the pedal. Swinging the piston rod  12  as in FIG. 3 up or down until the piston rod  12  hits the longitudinal slot  52  of the molding  24  or the longitudinal slot  50  of the main body  16 , will produce an upward component of force in FIG. 3 due to the lever action of the piston rod  12  which will release the molding  24  from its engagement with the main body  16 . Finally, the ball head  14  can be removed from the main body  16  along the joint duct  22  without having to apply any significant force. 
     In summary, therefore, the device provides articulated connection between a control element and a control rod with a ball head with a main body attached to the control element. The main body envelops a locating section providing positive location for the ball head and has an opening area through which the control rod extends when the device is assembled. The locating section is in two parts, the main body forming one part into which the ball head can be introduced through a joint duct located outside the opening area, the other part of the locating section being formed by a molding insertable into the joint duct. The result is a simple device which guarantees reliable connection between the control element and the control rod permanently backlash-free or having very little backlash.