Abstract:
Brake systems are disclosed for use in motor vehicles comprising a brake cylinder including a push rod, a brake key for activating a wheel brake on the motor vehicle, a braking lever having a first end for connection to the brake key and a second end for connection to the push rod, and a mount affixed to the push rod between the brake cylinder and the end of the push rod, the mount including a predetermined shape such as a pin and the braking lever including a predetermined shape such as an aperture so that the mount can be coupled to the push rod at a location between the brake cylinder and the end of the push rod by attaching the pin to the aperture. Methods for mounting brake systems in motor vehicles are also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device utilized in braking systems for motor vehicles. More particularly, the present invention has its main application in connection with braking systems for commercial vehicles. Still more particularly, the present invention relates to a method for mounting such a braking system on a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Larger motor vehicles, e.g. commercial vehicles, are presently designed with lower and lower ground clearances. A primary reason for this is the need to maximize the available cargo space in the vehicle. Since the maximum cargo space is limited by the maximum height allowed and the height of the vehicle chassis, there is consequently a desire to reduce the height of the chassis in order to thereby increase the cargo space. At the same time, maximum ground clearance is desired in order to avoid damage to the vehicle when driving over rough ground. The demands of low height of the chassis and large ground clearance in turn set limitations when designing the braking system of the commercial vehicle. This is particularly true in the case where the braking system comprises a compressed-air driven brake cylinder, which may be mounted standing in a given position in relation to a wheel shaft, and when the brake cylinder comprises a substantially vertically projecting push rod. With such a construction, the height of the chassis of the vehicle is limited by the length of the push rod. 
     It is known in the prior art that the end of the push rod, which protrudes from the brake cylinder, is normally threaded and connected to a brake key by means of a special lever member. 
     When the braking system is activated by the driver of the vehicle, the push rod is pressed out from the brake cylinder, thereby influencing the brake key by means of the lever. The brake key, in turn, activates the wheel brake. 
     With reference to FIG. 1, a previously known system of the above-mentioned kind will be described. FIG. 1 shows a brake cylinder  1 , intended to be mounted on a wheel shaft in a commercial vehicle. The brake cylinder  1  comprises a push rod  2 , which is pressed out essentially in a vertical direction (i.e., downwards in the drawing) when the braking system is activated by the driver of the vehicle. The movement of the push rod  2  is transferred to a brake key  3  by means of a braking lever  4 . The brake key  3  is arranged substantially parallel to the wheel shaft which is to be braked. 
     When mounting this previously known device, i.e. when the braking lever  4  is to be mounted in order to join the push rod  2  to the brake key  3 , the brake cylinder  1  and the brake key  3  have to be pre-installed, i.e. they are placed in the vehicle in advance. In this way, installation of the lever  4  may be accomplished by mounting one end of lever  4 , comprising an aperture  5  with internal splines, onto outer splines  6  on the brake key  3 . The spline separation which is utilized in this spline coupling will cause the opposite end of the lever  4  to be positioned adjacent to the push rod  2  in a position which may vary within a certain interval in relation to the end of the push rod  4 . The exact position for the end of the lever  4  is determined by the fixed spline separation and the length of the lever  4 . The splined coupling  5 ,  6  is thereafter locked by means of a locking screw  7  with appurtenant nut  8 . 
     The next step in the mounting operation is that a link element, consisting of two link members  9  and  10 , respectively, is brought together on both sides of the push rod  2  and the end of the lever  4 , which has been placed adjacent to the push rod  2 . The first link member  9  is joined to the second link member  10  by means of two screws,  11  and  12 , which are inserted into corresponding holes,  13  and  14 , in the second link member  10 , while a pin  15  in the first link member  9  is passed through a hole  16  in the lever  4  and into a further hole  17  in the second link member  10 . Thereafter, the link element  9 ,  10  is screwed on by means of the screws,  11  and  12 , and nuts,  18  and  19 . The link members,  9  and  10 , further comprise internal threads  20  (which are only evident from the link member  10  in FIG. 1) which interact with threads  21  on the push rod  2 . In this way, the push rod  2  may be locked to the link elements  9 ,  10  and transfer its movement to the brake key  3  by means of the lever  4 . 
     As mentioned above, the spline separation of the splined coupling  5 ,  6  implies that the end portion of the lever  4  facing towards the push rod  2  will be positioned in a position which may vary vertically within a certain interval. This interval is normally of the magnitude of approx. 30 mm. Thus, the length of the link element  9 ,  10  cannot be below this interval, since it has to be utilized for bridging the distance between the push rod  2  and the lever  4 . The fact that the interval must be accomodated by the link element  9 ,  10 , in its turn, means that this has to project downwards a relatively long distance below the push rod  2 . This constitutes a disadvantage, since it creates an essential limitation when the ground clearance and the height of the chassis of the vehicles are concerned. 
     SUMMARY OF THE INVENTION 
     A main object of the present invention is to achieve an improved device for joining a push rod and a brake key in a braking system, particularly for commercial vehicles, which braking system utilizes a compressed-air driven brake cylinder with a vertically projecting push rod. In particular, it is an object of the present invention to create conditions for optimizing the relation between the ground clearance and the height of the chassis of the vehicle. 
     A further object of the invention is to provide a simplified mounting of a braking system for a commercial vehicle, having a minimum number of components and working steps in the mounting operation. 
     In accordance with the present invention, these and other objects have now been realized by the invention of brake system for use in motor vehicles comprising a brake cylinder including a push rod having an end portion projecting from the brake cylinder upon activation of the brake cylinder, a brake key for activating a wheel brake on the motor vehicle, a braking lever including a first end and a second end, the first end of the braking lever adapted for connection to the brake key and the second end of the braking lever adapted for connection to the push rod, and a mounting member affixed to the push rod at a location between the brake cylinder and the end of the push rod, the mounting member including a first attachment member and the braking lever including a second attachment member whereby the braking lever can be coupled to the push rod at a location between the brake cylinder and the end of the push rod by attaching the first and second attachment members to each other. In accordance with one embodiment of the brake system of the present invention, the first attachment member comprises a predetermined shape of the mounting member and the second attachment member comprises a predetermined complementary shape of the braking lever. In a preferred embodiment, the predetermined shape of the mounting member comprises a pin and the predetermined complementary shape of the braking lever comprises an aperture. 
     In accordance with one embodiment of the brake system of the present invention, the push rod includes external threads and the mounting member comprises a substantially sleeve-shaped member including internal threads adapted to mate with the external threads of the push rod. 
     In accordance with another embodiment of the brake system of the present invention, the system includes a support including a first end and a second end, the first end of the support adapted for connection to the mounting member and the second end of the support adapted for connection to the braking lever. In a preferred embodiment, the mounting member includes a third attachment member and the first end of the support includes a fourth attachment member. More preferably, the third attachment member comprises a predetermined shape of the mounting member and the fourth attachment member comprises a predetermined complementary shape of the support. Most preferably, the predetermined shape of the mounting member comprises a pin and the predetermined complementary shape of the support comprises an aperture. 
     In accordance with another embodiment of the brake system of the present invention, the first end of the braking lever is adapted for connection to the brake key by means of a splined coupling. 
     In accordance with the method of the present invention, a method has been developed for mounting a brake system in a motor vehicle, the brake system comprising a brake cylinder including a push rod having an end portion projecting from the brake cylinder upon activation of the brake cylinder and a brake key for activating a wheel brake on the motor vehicle, the method comprising mounting a mounting member on the push rod at a location between the brake cylinder and the end of the push rod, providing a braking lever having a first end and a second end, connecting the second end of the braking lever to the mounting member at the location between the brake cylinder and the end of the push rod, and connecting the second end of the braking lever to the brake key in a direction substantially parallel to the longitudinal direction of the brake key. In a preferred embodiment, the mounting member includes a first attachment member having a predetermined shape integral therewith and the second end of the braking lever includes a second attachment member having a predetermined complementary shape integral therewith, the method further comprising connecting the second end of the braking lever to the mounting member by guiding the predetermined shape of the mounting member into the predetermined complementary shape of the second end of the braking lever. 
     In accordance with one embodiment of the method of the present invention, the method includes separately connecting the mounting member to the braking lever by means of a separate support. 
     The present invention is based on a mounting device which, together with the braking lever, comprises means for coupling the push rod to the braking lever, by means of the mounting device, at a point which is situated within the end of the push rod which projects from the brake cylinder. In this way, the only limitation for the height of the chassis/ground clearance is given by the length of the push rod, i.e. the distance between the brake cylinder and the lever may be made shorter than in previously known devices. 
     According to a preferred embodiment of the present invention, the push rod may be coupled to the lever by means of the mounting device since the mounting device comprises a modification of shape, preferably in the form of a pin, which interacts with a corresponding modification of shape, preferably a hole, which has been provided in the braking lever. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following detailed description, the invention will be described in greater detail with reference to the attached drawings, in which 
     FIG. 1 is a front, exploded, perspective view of a known device in a braking system; 
     FIG. 2 is a front, perspective view of a device in a braking system according to the present invention; 
     FIG. 3 is a side, perspective view of a rear axle in which the present invention may be utilized; 
     FIG. 4 a  is a top, elevational view showing the relationship between the push rod and the brake key prior to mounting the device according to the present invention; 
     FIG. 4 b  is a side, elevational view of the braking lever during mounting the device according to the present invention; and 
     FIG. 4 c  is a side, elevational view of the device according to the present invention after mounting. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, FIG. 2 is a perspective view of a device in accordance with the present invention which, according to a preferred embodiment, is utilized in connection with a braking system for a commercial vehicle. The drawing shows the device in its mounted state. The braking system comprises a compressed-air driven brake cylinder  22 , of a previously known type, which may be influenced by the driver of the vehicle when braking. The brake cylinder  22  comprises a push rod  23 , the lower end of which is provided with external threads  24 . According to this embodiment, the brake cylinder  22  is mounted standing up by means of an attachment bracket  25 , which is firmly affixed to the vehicle. The brake cylinder  22  may be mounted with an extension substantially in the vertical direction, or with another orientation. 
     The push rod  23  is known to be arranged to be pushed out from the brake cylinder  22  when the braking system is activated. In this manner, the movements of the push rod  23  are transferred to a brake key  26  by means of a braking lever  27 . The brake key  26 , in turn, is connected to a (not shown) wheel brake. The brake key  26  is preferably oriented with an extension which runs along an axis  28  which is substantially parallel to the wheel shaft of the vehicle, which supports the wheel which is to be braked. 
     The lever  27  and the brake key  26  may be connected by means of a splined coupling  29 , which is formed by external splines  30  on the brake key  26 , and internal splines  31  arranged in a hole  32  at one end of the lever  27 . The hole  32  is slotted, whereby the splined coupling  29  may be clamped by means of a locking screw  33 , interacting with a (not shown) nut on the underside of the right end portion of the lever  27 . 
     When mounting the device, it is required that the brake cylinder  22  and the appurtenant push rod  23  have been pre-mounted and are in position. Furthermore, the brake key  26  is pre-mounted. For this reason, the lever  27  must be brought into position in the direction which is marked with an arrow  34  in FIG. 2, i.e. in a direction which is essentially parallel to the axis  28 . Before the lever  27  is brought into position, however, in accordance with the present invention, a special mounting device, in the form of a cross  35 , is mounted on the push rod  23 . As will become evident by the discussion below, the cross  35  is composed of a sleeve-shaped element which is provided with internal threads, interacting with the threads  24  on the push rod  23 . Furthermore, the cross  35  comprises an intermediate portion  36 , having a square (optionally rectangular) cross-section and which is provided with two pins, out of which a first pin is intended to project through a hole in the lever  27  (not evident from FIG.  2 ), and a second pin  37  is intended to project through a hole  38  which has been tooled into a separate supporting member  39 . This supporting member  39  may, in turn, be mounted to the lever  27  by tightening two screws  40  which interact with corresponding holes in the lever  27 . 
     In FIG. 3, a rear axle  41  for a commercial vehicle is shown, for which the invention has its main application. The location of the brake cylinder  22  on the bracket  25  is evident from the drawing. The brake cylinder  22  is arranged such that the push rod  23 , when activated, can project a certain distance from the brake cylinder  22 . Furthermore, the push rod  23  is connected to the braking lever  27  by means of the supporting member  39 . The brake key  26  runs inside a brake key cover  42  comprising an opening which emerges where the braking device of the rear axle  41  (not shown) is arranged, i.e. in connection to a wheel shaft  43 . 
     In FIGS. 4 a - 4   c,  the procedure for mounting the device in accordance with the present invention is illustrated. FIG. 4 a  shows the initial position, whereby the push rod  23  is shown in cross section, and the brake key  26  is arranged in a certain predetermined position in relation to the push rod  23 . Firstly, the cross  35  is screwed upwards a certain distance on the push rod  23 . It can therefore be seen that the pins,  37  and  44 , on the intermediate section  36  of the cross  35  are directed substantially parallel to the brake key  26 . As is evident from FIG. 4 b,  the braking lever  27  is thereafter mounted substantially parallel to the direction in which the brake key  26  has its extension. The mounting direction is indicated by the arrow  34 . When mounting, it is ensured that the hole  32  in one end of the lever  27  is brought inwards over the brake key  26  so that the external splines  30 , which are located on the brake key  26 , come into contact with the internal splines  31  located in the hole  32 . Furthermore, it is ensured that the pin  44  is aligned with the pin hole  45  in the lever  27 . If a fine adjustment of the position of the cross  35  along the push rod  22  is necessary, this is achieved by screwing the cross  35  a number of turns upwards or downwards. 
     The lever  27  is curved in such a way that it comprises an intermediate portion  46 , the extension of which is mainly parallel to the brake key  26 . In this way it is possible for the location of the pin hole  45  to be slightly displaced in the direction along the length thereof in relation to the hole  32  in the opposite end of the lever  27 . This, in turn, implies that the lever  27 , may be brought a small distance over the brake key  26 , while the cross  35  still may be turned in order to be finely adjusted. This facilitates mounting of the lever  27 . 
     The construction of the above-mentioned supporting member  39 , comprising a planar support surface  47  for contacting the intermediate portion  46  of the lever  27 , is also evident from FIG. 4 b.  As mentioned above, the supporting member  39  additionally comprises a pin hole  38  arranged to interact with the pin  37 . Furthermore, the supporting member  39  comprises two holes  48  (of which only one is evident from FIG. 4 b ), intended for the through screws  40 , which are screwed into the corresponding holes in the lever  27 . In FIG. 4 c,  the device is shown in its mounted state, whereby the cross  35  has been adjusted into the correct position and its pins  37  and  44  have been fitted into the lever  27  and the supporting member  39 , respectively. When the lever  27  is then pushed completely into position on the brake key  26 , the splined coupling  29  is locked by means of tightening the fastening screw  33 . Finally, the supporting member  39  is locked by means of the screws  40 . 
     By means of the present invention, it is ensured that the end portion of the lever  27 , facing the push rod  23 , is positioned so that it is connected to the cross  35  at a point which lies within the end of the push rod  23  which projects from the brake cylinder. In the case where the brake cylinder is mounted vertically, this accordingly implies that this point is situated above the lower end of the push rod  23  (cf. FIG.  2 ). This means that no unnecessary extension of the push rod  23  is required. Instead, it is the maximum length of the push rod  23  which sets the limit to the height of the chassis and the ground clearance of the vehicle. 
     The present invention is not limited to the above-mentioned embodiment, but may be varied within the scope of the subsequent claims. The intermediate portion  46  of the lever  27  may, for instance, be adapted in length according to an existing mutual distance between the push rod  23  and the brake key  26 . Furthermore, the cross  35  may be provided with small holes which interact with pins in the lever and the supporting member, instead of the reverse thereof. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.