Abstract:
An assembly for mounting a leaf spring suspension system to a vehicle. The assembly includes an arrangement of a plurality of shackles that movably secure at least a rear portion of a leaf spring, which carries an axle of the vehicle, to a frame of the vehicle.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to an apparatus and method for mounting a suspension system. In one aspect, it relates to an apparatus and method for mounting a leaf spring suspension system to the frame of a vehicle. 
     BACKGROUND OF THE INVENTION 
     A leaf spring suspension system is a common form of suspension system. Leaf spring suspension systems can be used in many applications, including stationary conveyor systems and many other systems sensitive to mechanical vibrations. However, the most common use of leaf spring suspension systems is for commercial vehicles such as trucks, vans, and other large payload vehicles. 
     In particular, vehicle suspensions have commonly used leaf spring assemblies to resiliently support the axle relative to the frame and to carry loads on the axle fore and aft to frame-mounted supporting devices. Generally, a leaf spring assembly is pivotally connected at one end to a bracket rigidly mounted on the frame of the vehicle in a manner such that the leaf spring is free to rotate about a fixed pivot relative to the frame when the axle moves vertically. The other end of the leaf spring assembly is connected at another end to a second bracket also rigidly mounted to the frame of the vehicle. However, it is desirable that this connection at the rear end of the leaf spring have a double rotatable configuration (i.e., have two parallel axes of rotation) to help prevent buckling of the leaf spring as the axle moves relative to the frame and deflection of the leaf spring causes the spring to change its horizontal length. As a result, one or more shackles or links are generally used which are pivotally attached at their top ends to the second bracket and are pivotally attached at their bottom ends to the leaf spring. In this manner, the rear end of the leaf spring assembly is still pivotally attached to the axle, but also may still move in the fore and aft directions relative to the frame of the vehicle to help prevent buckling of the leaf spring. 
     The most common mechanism for mounting a leaf spring suspension system utilizes caps and pinch bolts to secure the spring pins and shackles used. In particular, the front end of a leaf spring assembly is pivotally connected to the front bracket using a spring pin rotatably attached to the front end of the leaf spring and to the front bracket. The spring pin is secured in place using a fitted cap that is attached to one end of the spring pin such that lateral movement of the spring pin relative to the leaf spring and the front bracket is prevented. 
     The rear end of the leaf spring assembly is connected in a double rotatable configuration to the rear bracket using two spring pins, two shackles, four pinch bolts, and two caps. One spring pin is rotatably attached to the rear end of the leaf spring and one spring pin is rotatably attached to the rear bracket. Each spring pin in the cap and pinch bolt mounting apparatus has a semi-circular groove near both ends of the spring pin, wherein the axis of each semi-circular groove is substantially perpendicular to the longitudinal axis of the spring pin. Two shackles are used wherein each shackle links one end of one spring pin to a corresponding end of the other spring pin. Each shackle has a central body portion and two ends; each end comprises two arms forming a substantially cylindrical hole but the arms do not form a complete cylinder in that the arms do not contact each other at the end farthest from the central body portion. Each end also has a bolt hole passing through both arms in a direction perpendicular to the substantially cylindrical hole such that the diameter of the substantially cylindrical hole can be reduced by threading a bolt through the bolt holes in the arms and tightening the bolt. Additionally, the bolt hole is oriented such that a bolt passing through both arms partially enters the substantially cylindrical hole formed by the arms. When assembled, a spring pin is aligned through the substantially cylindrical hole formed by the arms of the shackle such that a bolt threaded through the bolt hole in the arms of the shackle is aligned with the semi-circular groove near the end of the spring pin, and the bolt is tightened to form an interference fit between the spring pin and the shackle. In this manner, the spring is prevented from rotating relative to the shackle and is prevented from moving laterally relative to the shackle. In applications using this type of mounting apparatus, each shackle requires this assembly to be performed two separate times. Because two shackles are used to mount the leaf spring suspension system, one on each side of the leaf spring and the rear bracket, this assembly must be performed four times with four different bolts. Finally, a cap is placed on the end of each spring pin to further secure the spring pins in place. 
     Although the cap and pinch bolt apparatus for mounting a leaf spring suspension system does secure the suspension system to the frame, it is difficult and costly to utilize such an apparatus because of the amount of parts necessary for mounting the suspension. A mounting apparatus that utilizes fewer parts would be provide the following advantages: lower cost, simpler and easier installation and maintenance, lower weight, and a decreased probability of failure. For obvious reasons, fewer parts results in lower cost, simpler and easier installation and maintenance, and lower weight. Additionally, the probability of failure of an apparatus having fewer parts is statistically reduced. Therefore, a need exists to improve upon the cap and pinch bolt apparatus by reducing the number of parts necessary to mount a leaf spring suspension system. 
     SUMMARY OF THE INVENTION 
     An apparatus and method is provided for mounting a leaf spring suspension system to a structure using fewer parts than the prior art. Specifically, the mounting apparatus and method of the current invention can be used for many vehicle applications, but is particularly suited for use in commercial trucks, vans, and other large vehicles intended to carry large payloads. The mounting apparatus includes a spring pin and two fastening bolts for mounting one end of the leaf spring suspension system, and includes two spring pins, two shackles, and two fastening bolts for mounting the other end of the leaf spring suspension system. Each end of the leaf spring suspension system is attached to the frame of the vehicle (or to a bracket rigidly attached to the frame). In the preferred embodiment, each spring pin has a cylindrical center portion and two flattened ends located symmetrically about the cylindrical center portion, wherein each flattened end has a transverse cylindrical hole passing through it. Also in the preferred embodiment, each shackle has a central body portion and two U-shaped ends symmetrical about the central body portion, wherein each U-shaped end has an open-ended portion that is directed away from the central body portion of the shackle. Additionally, a cylindrical hole passes from the open-ended portion of one U-shaped end, through a longitudinal axis of the central body portion, and through the open-ended portion of the other U-shaped end. 
     In the preferred embodiment, one end of the leaf spring is rotatably attached to a bracket on the frame of the vehicle using only a spring pin and two fastening bolts. The spring pin is rotatably secured to the end of the leaf spring such that the flattened ends of the spring pin make contact with the bracket and a fastening bolt secures each flattened end to the bracket. The other end of the leaf spring is attached to another bracket on the frame of the vehicle in a double rotatable configuration using only two spring pins, two shackles, and two fastening bolts. One spring pin is rotatably secured to the end of the leaf spring and the other spring pin is rotatably secured to the bracket such that the flattened ends of both spring pins extend beyond both sides of the leaf spring and the bracket, respectively. One shackle is oriented such that one flattened end of the spring pin attached to the end of the leaf spring is seated in one of the U-shaped open ends of the shackle and a corresponding flattened end of the spring pin attached to the bracket is seated in the other U-shaped open end of the shackle. Similarly, the second shackle also seats corresponding flattened ends of these two spring pins. When assembled, the cylindrical transverse holes through the flattened ends of these two spring pins and the cylindrical holes in the shackles are aligned such that one fastening bolt secures the first shackle to the corresponding flattened ends of the spring pins and a second fastening bolt secures the second shackle to the other corresponding flattened ends of the spring pins. 
     In one embodiment, one spring pin is rotatably secured to each end of the leaf spring by forming a substantially circular loop in each end of the leaf spring and aligning a spring pin inside each looped end. Alternatively, the spring pins can be rotatably secured to each end of the leaf spring using other embodiments. For example, a U-shaped bolt or other U-shaped attachment member can be connected to the leaf spring such that the spring pin is encircled and thereby rotatably secured. 
     In yet another embodiment, the preferred U-shaped open ends of the shackles can be replaced as long as a single fastening bolt can still be used to fasten a single shackle to two spring pins. For example, the preferred U-shaped open ends can be replaced with square-shaped ends that encircle the spring pin. In this alternative embodiment, the cylindrical hole through the shackle also continues through the outer walls of the square-shaped ends such that a fastening bolt can pass through the entire length of the shackle. In still another alternative embodiment, the preferred U-shaped open ends can be replaced with O-shaped ends that encircle the spring pin. In this alternative embodiment, the spring pins can have cylindrical ends rather than flattened ends (but still have cylindrical transverse holes therethrough) so that the circumference of the cylindrical ends of the spring pins make uniform contact with the interior of the O-shaped ends of the shackle. Furthermore, it is preferred in this alternative embodiment that the O-shaped ends have a countersink encircling the cylindrical hole so that the head of the fastening bolt makes uniform contact with the surface of the O-shaped ends. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better and more complete understanding of the present invention and the advantages thereof will be gained from the following detailed description, claims, and accompanying drawings in which: 
     FIG. 1 is a perspective view of a fully assembled leaf spring suspension system utilizing a mounting apparatus for a suspension system according to the present invention; 
     FIG. 2 is a plan view of a spring pin according to the present invention; 
     FIG. 3 is a side elevational view of the spring pin depicted in FIG. 2; 
     FIG. 4 is an end elevational view of the spring pin depicted in FIG. 2; 
     FIG. 5 is a plan view of a shackle according to the present invention; 
     FIG. 6 is an elevational view of one U-shaped end of the shackle depicted in FIG.  4  and the cylindrical hole passing through a longitudinal axis of the shackle; 
     FIG. 7 is an enlarged bottom perspective view of the front of the fully assembled leaf spring suspension system depicted in FIG. 1; 
     FIG. 8 is an enlarged side perspective view of the rear of the fully assembled leaf spring suspension system depicted in FIG. 1; 
     FIG. 9 is an elevational view of an alternative embodiment for rotatably securing a leaf spring to the front and rear brackets, using U-shaped attachment members; 
     FIG. 10 is a perspective view of a shackle having square-shaped ends according to an alternative embodiment of the current invention; 
     FIG. 11 is a perspective view of a shackle having O-shaped ends according to an alternative embodiment of the current invention; and 
     FIG. 12 is a perspective view of a spring pin for use with the shackle depicted in FIG. 11 having O-shaped ends according to an alternative embodiment of the current invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to the accompanying FIGS. 1-12, wherein like reference numerals designate like or corresponding parts throughout the several views, the present invention is explained hereafter. 
     FIG. 1 illustrates a fully assembled leaf spring suspension system  10  utilizing the mounting apparatus  12  of the current invention. Although mounting apparatus  12  can be used for mounting a leaf spring suspension system  10  to any type of structure utilizing such a suspension, the preferred embodiment of this invention will be described in the context of a heavy-duty, large payload wheeled vehicle. It is important to note, however, that other applications such as stationary conveyor systems or any other apparatus utilizing a leaf spring suspension system can benefit from using the mounting apparatus  12  of the current invention. 
     In the preferred embodiment shown in FIG. 1, leaf spring suspension system  10  includes a leaf spring  14  attached to the frame  16  of a vehicle. Leaf spring  14  has an axle/dampener attachment point  18  near its center, which is used to attach leaf spring  14  to an axle (not shown) and a dampening mechanism (not shown). Leaf spring  14  allows the frame  16  to move relative to the axle and the ground when the vehicle is driven over irregular terrain or when a load is placed on frame  16 . The dampening mechanism provides a dampening force to the vibration of leaf spring  14 , thus returning the axle and frame  16  back to an equilibrium position relative to one another. Because of the large forces that are exerted on leaf spring  14  by this relative motion between frame  16  and the axle, a mounting between leaf spring  14  and frame  16  is necessary that is strong and durable yet also provides flexibility such that leaf spring  14  will not buckle under the large deflecting force to which it is subjected. The mounting apparatus  12  of the current invention simply and effectively provides such qualities. 
     The hardware used in mounting apparatus  12  for mounting leaf spring suspension system  10  to frame  16  includes three spring pins  20 , two shackles (or links)  22 , two front fastening bolts  24 , and two rear fastening bolts  26 . As best illustrated in FIGS. 2-4, each spring pin  20  generally comprises a cylindrical center portion  28  and two flattened ends  30  symmetrical about center portion  28  Each flattened end  30  has a transverse hole  32  to accommodate a front fastening bolt  24 . As best illustrated in FIGS. 5-6, each shackle (or link)  22  comprises a central body portion  34  and two U-shaped open ends  36  symmetrical about body portion  34 . A cylindrical hole  38  passes from one U-shaped open end  36 , through a longitudinal axis  40  along central body portion  34 , and to the second U-shaped open end  36 , such that a rear fastening bolt  26  can pass through the length of shackle  22 . 
     As shown in FIG. 1, leaf spring  14  has a front end  42  and a rear end  44 , each of which is securely attached to frame  16  using mounting apparatus  12 . In a preferred embodiment, a front bracket  46  and a rear bracket  48  are rigidly attached to frame  16  and the front and rear ends  42 ,  44  of leaf spring  14  are attached to the front and rear brackets  46 ,  48 , respectively. As can be seen in FIG. 7, front bracket  46  is a rigid structure having two connection points  50  for connecting the front end  42  of leaf spring  14  through the use of mounting apparatus  12 . Each connection point  50  on front bracket  46  has a cylindrical hole  52  for accommodating a front fastening bolt  24  (shown in FIGS. 1 and 7 with a fastening bolt  24  already inserted therethrough). The front end  42  of leaf spring  14  is capable of rotatably securing a spring pin  20  such that the longitudinal axis of spring pin  20  is substantially coplanar with leaf spring  14  and is substantially perpendicular to the length of leaf spring  14 . In a preferred embodiment as best shown in FIG. 7, the front end  42  of leaf spring  14  forms a loop  54  such that spring pin  20  can be aligned within looped front end  54  and the flattened ends  30  of spring pin  20  extend beyond the width of leaf spring  14 , thereby creating an axis of rotation  55  through looped front end  54 . The flattened ends  30  of spring pin  20  are placed in contact with the corresponding connection points  50  on front bracket  46  in an orientation such that the transverse hole  32  through each flattened end  30  is aligned with the corresponding cylindrical hole  52  through each connection point  50 . In the preferred embodiment shown in FIG. 7, it can be seen that each connection point  50  comprises a U-shaped notch in front bracket  46  to aid in seating and securing the flattened ends  30  of spring pin  20  to connection points  50 . Once properly aligned, one front fastening bolt  24  is threaded through each flattened end  30  and the corresponding connection point  50  and fastened with a nut, thereby rotatably securing the front end  42  of leaf spring  14  to front bracket  46  using only a single spring pin  20  and two front fastening bolts  24 . 
     Referring now to FIG. 8, shown is the mounting apparatus for rotatably securing the rear end  44  of leaf spring  14  to rear bracket  48 . Specifically, in this application a double rotatable connection (or a floating connection) is used to reduce the risk of buckling of leaf spring  14 . With a double rotatable connection, in addition to allowing rotation of the rear end  44  of leaf spring  14  relative to rear bracket  48 , the rear end  44  is also allowed to move laterally relative to rear bracket  48  (i.e., closer to or further from front bracket  46 ) to compensate for deflection of the center portion  58  of leaf spring  14 . Generally speaking, a double rotatable connection means that the rear end  44  of leaf spring  14  is provided with two parallel axes of rotation. As with the front end  42  of leaf spring  14 , the rear end  44  is also capable of rotatably securing a spring pin  20  such that the longitudinal axis of spring pin  20  is substantially coplanar with leaf spring  14  and is substantially perpendicular to the length of leaf spring  14 . In a preferred embodiment, the rear end  44  of leaf spring  14  forms a loop  60  such that spring pin  20  can be aligned within looped rear end  60  and the flattened ends  30  of spring pin  20  extend beyond the width of leaf spring  14 . Rear bracket  48  is also capable of rotatably securing another spring pin  20  such that the length of spring pin  20  is substantially coplanar with leaf spring  14  and is substantially perpendicular to the length of leaf spring  14 , i.e., rotatably secures a spring pin  20  with an axis of rotation  64  parallel to the axis of rotation  66  of the rotatable attachment to the rear end  44  of leaf spring  14 . In the preferred embodiment shown in FIG. 8, rear bracket  48  has a cylindrical hole  62  having an axis  64  parallel to the axis  66  of looped rear end  60  (cylindrical hole  62  shown in FIGS. 1 and 8 with spring pin  20  already inserted therethrough). By providing looped rear end  60  and the cylindrical hole  62  through rear bracket  48 , the two parallel axes of rotation  64 ,  66  necessary for a double rotatable connection of the rear end  44  of leaf spring  14  to rear bracket  48  are created. 
     For the physical connection between the parallel axes of rotation  64 ,  66  of the rear end  44  of leaf spring  14 , the mounting hardware comprises two spring pins  20 , two shackles  22 , and two rear fastening bolts  26 . One spring pin  20  is aligned within looped rear end  60  such that the flattened ends  30  of spring pin  20  extend beyond the width of leaf spring  14 . Another spring pin  20  is aligned with the cylindrical hole  62  through rear bracket  48  such that the flattened ends  30  of spring pin  20  extend beyond the width of rear bracket  48 . As can be seen in FIG. 8, one shackle  22  is located on each side of leaf spring  14  and rear bracket  48 . Specifically, each shackle  22  is oriented such that the top U-shaped open end  36  of shackle  22  seats a flattened end  30  of spring pin  20  aligned in cylindrical hole  62  and the bottom U-shaped open end  36  of shackle  22  seats a corresponding flattened end  30  of spring pin  20  aligned in looped rear end  60 . In this arrangement, the transverse holes  32  through the corresponding flattened ends  30  of spring pins  20  seated on shackle  22  are aligned with the cylindrical hole  38  through shackle  22 . For each shackle  22 , one rear fastening bolt  26  is threaded through the transverse hole  32  through flattened end  30  of spring pin  20  seated on the top U-shaped open end  36  of shackle  22 , through the cylindrical hole  38  through shackle  22 , and through the transverse hole  32  through flattened end  30  of spring pin  20  seated on the bottom U-shaped open end  36  of shackle  22 . Each rear fastening bolt  26  is then fastened with a nut, thereby physically connecting the two parallel axes of rotation  64 ,  66  and rotatably securing the rear end  44  of leaf spring  14  to rear bracket  48  in a double rotatable configuration that allows rotation and lateral movement of the rear end  44  of leaf spring  14  relative to rear bracket  48 . 
     It will be appreciated that variations from this preferred embodiment are within the scope of the current invention. For example, the mechanism for rotatably securing spring pin  20  to the front end  42  of leaf spring  14  and the rear end  44  of leaf spring  14  may vary. Specifically, as shown in FIG. 9, this rotatable attachment can be created by connecting a U-shaped attachment member  70  to both ends  42 ,  44  of leaf spring  14  that can encircle spring pins  20 , thereby rotatably securing leaf spring  14  to spring pins  20 . Any other mechanism for rotatably securing spring pin  20  can also be used without departing from the scope of the current invention. As another example, shackle  22  can be embodied differently as long as a solid link that can be connected with a single rear fastening bolt  26  is provided. Specifically, as shown in FIG. 10, shackle  22  could have two square-shaped ends  72  rather than the U-shaped open ends  36  of the preferred embodiment. In this alternative embodiment, the cylindrical hole  38  through shackle  22  extends through the outer walls  74  of square-shaped ends  72  and the flattened ends  30  of spring pins  20  fit inside square-shaped ends  72 . In this manner, mounting apparatus can be secured by threading rear fastening bolt  26  through the outer wall  74  of one square-shaped end  72 , through the flattened end  30  of a first spring pin  20 , through the central body portion  34  of shackle  22 , through the flattened end  30  of a second spring pin  20 , and through the outer wall  74  of a second square-shaped end  72 . Similarly, as shown in FIG. 11, shackle  22  can have two O-shaped ends  76  rather than the U-shaped open ends  36  of the preferred embodiment. In this alternative embodiment, it is preferred that cylindrical hole  38  through shackle  22  have a countersink  80  surrounding cylindrical hole  38  at the outer walls  82  of the O-shaped ends  76  such that the head of rear fastening bolt  26  makes contact with a flat surface. As illustrated in FIG. 12, in order that spring pins  20  fit snugly within the O-shaped ends  76  of shackle  22 , spring pins  20  can have cylindrical ends  78  that still have transverse holes  32  through which rear fastening bolt  26  is threaded. 
     The current invention also encompasses a method of mounting a suspension system to a frame  16  wherein the frame  16  will likely be subjected to mechanical vibrations during use. As best illustrated in FIG. 1, the components to be attached using this method are a front bracket  46 , a rear bracket  48 , and a leaf spring  14  with a front end  42  and a rear end  44 . To mount the leaf spring  14  to the front bracket  46  and the rear bracket  48 , this method uses three spring pins  20 , two shackles  22 , two front fasteners  24 , and two rear fasteners  26 , each of which has been described above. As shown in FIG. 7, the front end  42  of the leaf spring  14  is rotatably attached to the front bracket  46  by rotatably mounting one spring pin  20  to the front end  42  of the leaf spring  14  and then securing the opposite ends of this spring pin  20  to the front bracket  46  using the two front fasteners  24 . As shown in FIG. 8, the rear end  44  of the leaf spring  14  is rotatably attached to the rear bracket  48  in a double rotatable configuration (i.e., a connection that has two parallel axes of rotation). This double rotatable configuration is achieved by creating two rotatable connections, one at the rear end  44  of the leaf spring  14  and another at the rear bracket  48 , and linking the two rotatable connections using two shackles  22 . The first rotatable connection is established by rotatably mounting a second spring pin  20  to the rear end  44  of the leaf spring  14  and the second rotatable connection is established by rotatably mounting a third spring pin  20  to the rear bracket  48 . The two rotatable connections are linked by linking a first end of the second spring pin  20  to a corresponding first end of the third spring pin  20  using a first shackle  22  and by linking the second end of the second spring pin  20  to a corresponding second end of the third spring pin  20  using a second shackle  22 . These links are then secured by using a first rear fastener  26  to fasten the first end of the second spring pin  20 , the corresponding first end of the third spring pin  20 , and the first shackle  22 , and by using a second rear fastener  26  to fasten the second end of the second spring pin  20 , the corresponding second end of the third spring pin  20 , and the second shackle  22 . 
     In a preferred embodiment of the method of this invention that is best illustrated in FIGS. 7 and 8, the spring pins  20  and the shackles  22  are linked in a particular manner. Specifically, each of the two spring pins  20  includes two ends  30 , wherein each end has a transverse hole  32  passing through the diameter of the spring pin  20 , and each shackle  22  includes a cylindrical hole  38  passing along its longitudinal axis  40 . The link between the spring pins  20  and the shackles  22  are thus secured using these transverse holes  32  and cylindrical holes  38 . In particular, the first end of the second spring pin  20  and the corresponding first end of the third spring pin  20  are secured to the first shackle  22  by inserting a rear fastener  26  through the cylindrical hole  38  along the longitudinal axis  40  of the first shackle  22  and through the aligned transverse holes  32  through the second spring pin  20  and the third spring pin  20 . The second end of the second spring pin  20  and the corresponding second end of the third spring pin  20  are secured to the second shackle  22  by inserting a rear fastener  26  through the cylindrical hole  38  along the longitudinal axis  40  of the second shackle  22  and through the aligned transverse holes  32  through the second spring pin  20  and the third spring pin  20 . 
     Finally, it should be readily apparent that the method of this invention is not limited to any particular order. For example, the method disclosed and claimed herein is equally advantageous regardless of which end of the leaf spring  14  is attached first, regardless of which shackle  22  is attached first, and regardless of which spring pin  20  is attached first. As a result, the order in which this method is described should not be considered a limitation to the scope of this invention. 
     Having thus described in detail a preferred selection of embodiments of the present invention, it is to be appreciated and will be apparent to those skilled in the art that many physical changes could be made in the apparatus without altering the inventive concepts and principles embodied therein.