Abstract:
A suspension system for wheeled vehicles, particularly trailers, that is mounted underneath the vehicle frame and forward of the axle (in case of a single axle suspension) and both forward and rearward of axles (in case of a tandem axle suspension). The suspension system at each side of the vehicle frame comprises a hanger, a control arm and an elastomer spring. The hanger has a support bracket and a hanger channel and is the frame bracket connecting the suspension to the vehicle frame. The elastomer spring biases the control arm and the hanger and therefore isolates the vibration of the suspended portion of the vehicle (the sprung mass) from that of the axle(s) and wheels (the unsprung mass).

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to suspension systems. More particularly, the invention relates to a suspension system for a vehicle such as a light, or medium duty trailer.  
       BACKGROUND OF THE INVENTION  
       [0002]     The use of suspension systems for wheeled vehicles such as light to medium duty trailers is well known. Suspension systems are generally a set of components, including springs and shock absorbers, which suspend the vehicle above the wheels to isolate vibration of the sprung mass. Many different suspension systems are available for vehicle owners with the most common types of suspension systems being leaf spring suspensions, air suspensions and/or rubber-torsion-bar suspensions.  
         [0003]     Leaf spring suspensions are well known and have been used for a long time. In general, if a solid axle connects the rear wheels of the vehicle, the suspension is usually quite simple and is based on a leaf spring suspension system. The leaf spring clamps directly to the axle while the ends of the leaf spring attach to the frame of the vehicle through hanger brackets. For many years, vehicle manufacturers preferred this design due to its simplicity, but leaf springs suffer from various disadvantages. These disadvantages include a poor quality of ride for the vehicle occupants since a leaf spring suspension system contains little or no energy absorbing medium to dampen shocks and to reduce the natural frequency of vibration of the sprung mass (which is the mass of the vehicle supported on the suspension system). Also, since the spring rate of steel leaf springs is linear, the vibration frequency of the sprung mass may vary significantly from empty to loaded conditions. Furthermore, the suspension system is typically quite noisy since there are many moving joints and parts. Another disadvantage of a leaf spring suspension system is that the system comprises many components which need to be installed together which leads to a need for more regular maintenance. Also, over time, leaf springs deform permanently and once a leaf spring is deformed, its length also changes which causes an equalizer bar to permanently lean to one side reducing the operating range of the suspension system.  
         [0004]     With air suspension systems, these are generally less reliable since they are subject to air leaks which may take place within fittings, the tubing, height control valves, inflate/deflate valves, air compressors or the air springs themselves. The performance of an air suspension is dependent on the ability of the system to regulate the air pressure in the air springs which is not an easy task. If there is too much pressure in the air springs of the suspension system, the ride becomes rough but if there is not enough pressure in the air springs, the suspension system is ineffective. Furthermore, due to the size of air springs, they are not adaptable for some applications. Also, for vehicles using air suspension systems, thicker wall axles are preferred which result in heavier and more expensive axles being used.  
         [0005]     In rubber torsion-bar suspensions, there is no load equalization for multiple-axle trailers since each torsion-bar suspension works independently of the others. Maintenance and the replacement of damaged or worn parts in a rubber torsion-bar suspension system is also quite difficult such that when a part requires repair, the entire system is generally replaced. The suspension system is also large and bulky which makes it more difficult to store and ship the rubber torsion-bar suspension systems. Furthermore, when the crank arm of the torsion-bar suspension system acts as a cantilever beam, the crank arm experiences combined bending and torsion stresses. In order to reduce the stress level being experienced, the crank arms are generally manufactured quite short. However, these short crank arms require a large range of rotation to provide an adequate amount of spindle travel and therefore, when combined with a predetermined camber causes a wide range of change in toe-in angle. This change in toe-in angle causes an increase in the amount of scrubbing, chafing and/or wearing of tires especially when the vehicle is in a loaded condition.  
         [0006]     It is, therefore, desirable to provide a novel suspension system for a vehicle.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to obviate or mitigate at least one disadvantage of previous suspension systems for vehicles.  
         [0008]     The present invention is directed at a suspension system which endeavours to provide a quieter ride than conventional suspension systems. The pressure and forces which the suspension system experiences during transportation are received and absorbed by an elastomer spring. The elastomer spring provides the necessary elasticity to absorb the forces and operates in a quiet manner thus providing a quieter ride. Furthermore, there are very few parts to the suspension system of the invention and therefore maintenance of the present invention is relatively simple. Moreover, disassembly of the suspension system is quite simple due to the use of fewer parts. The present suspension system is also quite versatile in its use since it may be installed on steel frames as well as on aluminum and composite frames. Furthermore, the suspension systems of the driver and passenger sides are independent compared to various known suspension systems allowing the suspension system to be installed on vehicles with different widths. This also allows the suspension systems to provider greater roll stability.  
         [0009]     In a first aspect, the invention provides a suspension system for a vehicle comprising a control arm having an axle end and a hanger end, the axle end configured for mounting the control arm to an axle of the vehicle; a hanger, mounted to the control arm at the hanger end, having means for mounting the suspension system to a frame of the vehicle; and an elastomer spring, located between the control arm and the hanger, away from the axle end of the control arm.  
         [0010]     In a further embodiment, there is provided a tandem axle suspension system for a vehicle comprising an equalizer bar; a hanger, mounted to the equalizer bar, for mounting to a frame of the vehicle; a pair of control arms, each connected at an end of the equalizer bar; wherein each of the pair of control arms having an axle end and an equalizer end, the axle end configured for mounting the control arm to an axle of the vehicle; and an elastomer spring, located between each of the pair of control arms and the corresponding end of the equalizer bar, away from the axle end of each of the pair of control arms.  
         [0011]     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:  
         [0013]      FIG. 1   a  is a perspective view of an embodiment of a single axle suspension system in accordance with the invention;  
         [0014]      FIG. 1   b  is a side view of the embodiment of  FIG. 1   a  with an elastomer spring compressed;  
         [0015]      FIG. 1   c  is a side view of the embodiment of  FIG. 1   a  with the elastomer spring uncompressed;  
         [0016]      FIG. 2   a  is a perspective view of a control arm;  
         [0017]      FIG. 2   b  is a side view of the control arm of  FIG. 2   a;    
         [0018]      FIG. 3  is a cross-section taken along line  3 - 3  of  FIG. 2   a;    
         [0019]      FIG. 4   a  is a perspective view of an elastomer spring;  
         [0020]      FIG. 4   b  is a top view of the elastomer spring;  
         [0021]      FIG. 4   c  is a cut away view taken along line  4   c - 4   c  of  FIG. 4   b;    
         [0022]      FIG. 4   d  is a top view of a second embodiment of an elastomer spring;  
         [0023]      FIG. 4   e  is a cut away view taken along line  4   e - 4   e  of  FIG. 4   d;    
         [0024]      FIG. 5   a  is a perspective view of a tandem axle suspension system when there is no load on the suspension system;  
         [0025]      FIG. 5   b  is a perspective view of the tandem axle suspension system of  FIG. 5   a  when there is a load on the suspension system;  
         [0026]      FIGS. 6   a  and  6   b  are schematic illustrations of an equalization process; and  
         [0027]      FIG. 7  is a schematic view of different ride heights. 
     
    
     DETAILED DESCRIPTION  
       [0028]     Generally, the present invention provides a novel suspension system for a vehicle.  
         [0029]      FIGS. 1   a  to  1   c  provide, respectively, a perspective view and two side views of a suspension system which is to be installed at one end of an axle of a vehicle.  FIG. 1   b  is a side view of the suspension system with the elastomer spring compressed and  FIG. 1   c  is a side view of the suspension system with the elastomer spring uncompressed.  
         [0030]     In the present application, the term suspension system has been used to describe the suspension system for one end of a vehicle axle. However, as will be appreciated by one skilled in the art, a pair of suspension systems are generally mounted at opposite ends of an axle to provide adequate support and stability for a vehicle. The axle is a fixed bar or beam with bearings at its ends to mount the axle to a tire, or wheel, at each end about which the tires rotate. Although it is not common for only one suspension system to be mounted to an axle, this embodiment is contemplated.  
         [0031]     In the present embodiment, in which a single axle suspension system is shown, the suspension system  10  comprises a hanger  12 , comprising a support bracket  14  (including a mounting plate  15 ) and a hanger channel  16 , connected to a control arm  18  via the hanger channel  16 . The support bracket  14  is connected to, preferably by welding, the hanger channel  16  and generally mounted to the under-carriage or side of a vehicle  100  such as a light or medium duty trailer. Although many methods of mounting the suspension system  10  to the vehicle are known, in the preferred embodiment, the suspension system  10  is bolted or welded to the frame of the vehicle.  
         [0032]     The control arm  18  is preferably bolted (via fastening means  21 , seen as a bolt), at a hanger end  20 , to the hanger channel  16  and also includes a set of holes  22  (at an axle end  24 ) for receiving a pair of U-bolts  26  which are used to assist in mounting the suspension system  10  to an axle  102  of the vehicle frame  100 . Other fastening means  21  such as a pin or a stud may also be used. The control arm acts as a trailing arm connecting the axle  102  of the vehicle to the hanger channel  16  causing isolation of the vibration of the axle of the vehicle (when the vehicle is in motion) from the sprung mass (which is the mass of the vehicle supported on the suspension system).  
         [0033]     As will be understood by one skilled in the art, the suspension system shown in  FIG. 1 a  is for a tire located on the driver side of the vehicle. The axle end  24  of the control arm  18  is located closer to the rear of the vehicle (with respect to the hanger channel  16 ), so that the mounting plate  15  (via the mounting holes  27 ) is mounted to a side of the trailer frame using fastening means. A similarly shaped suspension system (with the difference being the position of the mounting plate  15  of the support bracket  14 ) is mounted to the opposite (or passenger side) end of the axle to provide a complete suspension system at both ends of the axle as is normally provided for vehicles. The mounting of the axle to a wheel is well known.  
         [0034]     The mounting of the suspension system  10  to the axle  102  will be known to one skilled in the art and one example of how the suspension system is mounted to an axle is shown in  FIG. 1   b.  The curved portion of the U-bolts  26  conforms to the shape of the axle tube and assists in locking the axle  102  in place atop the axle end  24  of the control arm  18 .  
         [0035]     An elastomer spring  28 , such as one manufactured under the trade name AEON® by TIMBREN Industries Incorporated of Ajax, Ontario, Canada, is located between the bottom surface of the support bracket  14  and the top surface of the control arm  18 . Although described as an elastomer spring, the spring is preferably manufactured from natural rubber but may also be manufactured from urethane, micro-cellular urethane or other like materials. Unlike some conventional suspension systems where the spring is located over the axle of the vehicle, the location of the elastomer spring  28  in the present invention is away from the axle end  24  of the control arm  18 . The spring  28  absorbs the vertical force or forces which occur while the vehicle is moving, or stationary, in order to protect other parts of the vehicle such as the axle from damage or wear and tear due to the substantial forces being applied to these parts. The spring  28  also assists in providing a more protected method of transporting goods in a trailer. Furthermore, the use of the elastomer spring  28  provides a quieter ride since there is no metal on metal contact between moving parts as is present with some other conventional suspension systems.  
         [0036]     As shown in  FIGS. 2   a  and  2   b,  a perspective view and a side view of the control arm are provided. In these figures, the hanger end  20  and the axle end  24  of the control arm  18  are more clearly shown. At the axle end  24 , the suspension system  10  is mounted to the axle of a vehicle by locating the axle on a saddle-shaped portion  25  of the control arm  18  and inserted U-bolts  26 . The U-bolts, then by gravity, come to rest around the axle and lock the axle in place as shown in  FIG. 1   b  with the assistance of a number of washers and nuts.  
         [0037]     The hanger end  20 , comprises a tube  29 , preferably of metal, having an inner hole  30  for receiving the fastening means  21  (as shown in  FIG. 1   a ). A control arm bushing  37  (described with respect to  FIG. 3 ) is preferably press fitted into the hole  30  of tube  29  and also includes an inner hole for receiving the fastening means  21 . The axis of the circular tube  29  also represents an axis about which the control arm  18  pivots when a vertical force is applied to the suspension system  10 . As will be understood, when the suspension system  10  experiences a downward force from the vehicle, the support bracket  14  of the hanger  12  moves with respect to the control arm  18  or else the suspension system  10  may break or be damaged. Therefore, as the elastomer spring  28  absorbs the forces exerted on the suspension system, some of the force is also absorbed by the control arm bushing  37 . This is described in further detail below.  
         [0038]     In order to secure the control arm  18  to the hanger channel  16  of the hanger  12 , the hanger channel  16  and the control arm  18  are aligned so that holes in the hanger are aligned with the hole  30  in the tube  29  and the hole in the control arm bushing  37 . Both the tube  29  and the control arm bushing  37  rest between the inner walls of the hanger channel  16 . Once aligned, the bolt is placed through the holes and secured via a nut  34  or any other fastening member.  
         [0039]     As shown in cross-section in  FIG. 3  (taken along line  3 - 3  of  FIG. 2   a ), the control arm bushing  37  comprises a tube (preferably of steel)  38  and a circular layer of an elastomer material (such as rubber)  42  surrounding the tube  38 . The layer of elastomer  42  is preferably moulded to the outer surface of the tube  38 . The tube  38  also encircles the fastening means  21 . The fastening means  21  is protected from the inside hole of the tube  38  by a cylindrical sleeve  40 , preferably manufactured from nylon, however, other materials such as ultra-high molecular weight (UHMW) polyethylene or rubber may also be used. The circular layer of elastomer material  42  provides elasticity to the suspension system  10  to absorb the vertical forces experienced at the hanger channel  16  allowing control arm  18  to pivot with respect to the hanger channel  16 . The layer of elastomer  42  also assist in transferring lateral loads of axle  102  to the hanger  12  through a shock absorbing material allowing the hanger  12  to pivot with respect to the control arm  18 . The inner surface of the tube  29  is also protected from the outer surface of the tube  38  by the layer of elastomer  42 .  
         [0040]     The control arm  18  also includes means  43  for locating the elastomer spring, which in the preferred embodiment is shown as a pair of guides on the top surface of the control arm  18 .  
         [0041]     In  FIG. 4   a,  a perspective view of the elastomer spring is provided while in  FIG. 4   b,  a top view of the elastomer spring is shown. The elastomer spring  28  preferably has a top portion  52  and a bottom portion  54  although, as can be seen in  FIG. 4   c  (which is a cross-section taken along line  4   c - 4   c  of  FIG. 4   b ), the elastomer spring is preferably of one-piece construction. The elastomer spring preferably includes a pair of holes  56  in which the means  43  for locating the spring are inserted in order to locate the spring during the assembly process. As indicated above, the positioning of the spring  28  with respect to the control arm (i.e. away from the axle end) is an advantage over prior art suspension systems. The shape of the elastomer spring (in the preferred embodiment), allows the axle to have more space above it which allows lower ride heights to be experienced. The shape of the spring also allows for the ride quality to be improved since the frequency of vibration is lowered.  
         [0042]      FIG. 4   d  and  4   e  provide views of a second embodiment of an elastomer spring which may be used with the suspension system. In this embodiment, the size of the holes  56  for the guides are reduced to provide more elastomer material to assist in absorbing the forces.  
         [0043]     Turning to  FIGS. 5   a  and  5   b,  another embodiment of a suspension system in accordance with the invention is shown. In this embodiment, the suspension system is for a tandem axle configuration. The suspension system is designed for vehicles which have tandem axles connecting a set of at least four wheels.  FIG. 5   a  shows the tandem axle suspension system when there is no load on the suspension system while  FIG. 5   b  shows the tandem axle suspension system when there is a load on the suspension system.  
         [0044]     The tandem axle suspension system  200  comprises a hanger  202  which is connected to an equalizer bar  204  which, in turn, is connected at each end to a control arm  206 . An elastomer spring  28  is located between each end of the equalizer bar  204 , connected at its top surface to the equalizer bar  204  and at its bottom surface to the respective control arm.  
         [0045]     The hanger  202  is a rigid interface between the frame of the vehicle  210 , or trailer, and the rest of the suspension system  200  and is preferably attached to the frame of the vehicle or trailer by welding, bolting or riveting but other mounting methods are also known and contemplated.  
         [0046]     The equalizer bar  204  is a beam or bar with a set of joints  208  (preferably three) for pivoting which assists in balancing (equalizing) the load being experienced by the tandem axles so that there is an even distribution of load between the two axles during operation of the vehicle. One of the joints  208   a  is located in the middle of the equalizer bar  204 , and the other two joints  208   b  and  208   c  are located at opposite and equally spaced distances from the middle joint  208   a.  The equalizer bar  204  is connected to the hanger via fastening means  210  at the middle joint  208   a  and is able to articulate, or rotate about that axis.  
         [0047]     The control arms  206  located at opposite ends of the equalizer bar are similar to the control arms  18  described above. The difference being that the hanger  12  is replaced by the ends of the equalizer bar  204 . The control arm  206  also includes a control arm bushing (not shown) which operates in a manner similar to the one described above at an equalizer end of the control arm  206 .  
         [0048]     Similar to the control arm bushing  37  described above, an equalizer bushing is located in the axis of the middle joint  208   a.  The fastening means, seen as a bolt,  210  which fastens the hanger  202  to the equalizer bar  204  is inserted through the equalizer bushing (which is located in the under-carriage of the equalizer bar) and then fasten on the other side to lock the equalizer bushing in place. As with the control arm bushing, the equalizer bushing provides further assistance in absorbing the forces experienced by the suspension system during use.  
         [0049]     The equalizer bushing allows the equalizer bar  204  to articulate and also acts as an interface to transfer the load being experienced on the tandem axle to the hanger  202  through a flexible member to improve ride quality and to prolong the life of the suspension system and axle.  
         [0050]     This equalization process is shown with respect to  FIGS. 6   a  and  6   b.    FIG. 6   a  shown the tandem axle suspension system in operation on even ground while  FIG. 6   b  shows the tandem axle suspension system in operation on uneven ground.  
         [0051]     On even ground, the equalizer bar  204  remains parallel to the frame of the vehicle (when the vehicle is level) in order to distribute the load evenly. However, when the tandem axle system is in operation on uneven ground, the equalizer bushing allows the equalizer bar  204  to adjust itself in accordance with the profile of the ground. In operation, the equalizer bar  204  articulates and adjusts the position of the tandem axles relative to the frame of the vehicle until there is conformity between the profile of the ground and the location of the axles. This allows both tires to stay on the uneven ground and maintains equal loads between the axles so that one axle will not be more overloaded than the other (as long as the equalizer bar  204  is free to articulate. This assists to reduce the stress on the suspension systems parts and minimizes twisting and undue stress on the frame of the vehicle.  
         [0052]     Another advantage of the invention is that the ride height (vertical distance from the centre of the spindle to the bottom of the vehicle frame) may be easily changed by inverting the control arm causing the suspension system to be bottom mounted (axle is below control arm) rather than top mounted (as described).  FIG. 7  provides a schematic view of different ride heights which may be achieved with the suspension system of the invention.  
         [0053]     In each of the embodiments, the elastomer spring is preferably tapered-shape and generally designed to match/mate with the contours and shape of the surface with which it is fastened or abutting. The tapered shape of the elastomer spring is designed to be consistent with the range of articulation of the control arm and the geometry of the suspension system. The compact design of the spring provides an advantage in that the spring may be located closer to the outboard of the frame of the vehicle to maximize the roll stability of the trailer. The reduced footprint width of the spring also allows the suspension system to have a narrower width and therefore be designed lighter, making it possible to minimize the unsprung mass of the suspension system and to achieve better ride quality. In use, as the vertical load on the axle increases, the spring deforms in a gradual manner (in accordance with the load) and its spring rate progressively increases, its height shortens and the pressure on the spring surfaces contacting the support bracket and the control arm increases. This increased pressure is distributed over the length of the spring to produce a resultant force that counteracts with the axle load to establish a new stable position for the control arm  18  and the axle with respect to the frame of the vehicle.  
         [0054]     In another embodiment, although described with U-bolts, other methods of mounting the suspension system to the axle of the vehicle are contemplated which allow a rigid or semi-rigid connection to be achieved between the suspension system and the axle. These methods include, but are not limited to, welding, bolting, clamping or press-fitting.  
         [0055]     One other advantage of the suspension system of the present invention is that it is easy to install to a vehicle since there is only a single hanger to install to the vehicle at each end of the axle.  
         [0056]     As is understood, although a pair of suspension systems are generally required to be installed at opposite ends of the axle, the suspension systems are independent from each other and therefore can be packaged separated. This provides an improvement over conventional suspension systems which are large and bulky.  
         [0057]     Another advantage is that the suspension system of the present invention can be easily disassembled. Damaged or worn parts may be very quickly and easily replaced.  
         [0058]     The modular assembly design also allows the metal parts of the suspension system be easily rust proofed (if necessary) along with other processes such as painting, e-coating, plating, galvanizing etc.  
         [0059]     Another advantage of the suspension system is that it is quiet since there are fewer moving parts and also no metal on metal contact.  
         [0060]     The suspension system of the present invention also requires very little or no maintenance since elastomer springs, especially rubber springs, have been proven to be long lasting and are relatively unaffected by changes in climates or environments.  
         [0061]     Although described with respect to single axles, the suspension system may also be mounted on drop axles. The suspension system may also be mounted on any vehicle frame such as steel, aluminium or a composite frames.  
         [0062]     Advantages are also experienced with the tandem axle suspension system in that the suspension system is fully equalized. Equalization is known as the ability of a suspension system to distribute the combined load of an axle group equally at all times between individual axles so that any load (downward force) which is being experienced by the axles is equally distributed to the multiple control arms. This also reduces the amount of stress which is experienced by the parts of the suspension system to prolong the life of these components.  
         [0063]     Another advantage of the tandem axle suspension system is the ease with which the axles may be aligned. Since the driver side and passenger side suspension systems are pre-assembled and the distance between axles pre-determined, there will be parallelism in the positioning of the axles and the suspensions systems by design during installation of the axles.  
         [0064]     Although directed at light and medium duty trailers, it will be understood that since vehicles may have different axle sizes, the axle end of the control arm may be manufactured to accordingly mate with any axle.  
         [0065]     Also, although the suspension system of the invention is geared towards trailers, the suspension system may be installed in vehicles such as cars.  
         [0066]     In an alternative embodiment, the control arm bushing  37  or the equalizer bushing may be moulded to the control arm and does not have to be press fitted.  
         [0067]     The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.