Motor vehicles such as dump trucks, refuse trucks, transit concrete mixing trucks, open-bed trucks, utility trucks, military trucks and other vehicles of various types to which a significant load may be added for transport are limited in their load transporting ability by various factors. Such as the weight bearing capacity of their supporting axles and applicable federal and state law. With such laws for example limiting the gross vehicle weight to 80,000 pounds, the weight carried by a single axle to 20,000 pounds and there being an exception as to consecutive axles that limits them to carrying a prescribed combined weight depending on their number and spacing. For example, the combined axle carrying weight is limited to 34,000 pounds in regard to the two powered tandem axles that are typically employed with heavy duty load-transporting motor vehicles. And with such factors as a result impacting the use of such motor vehicles in that the more weight the vehicle can transport at a time, the more useful the vehicle can be provided other factors that impact the ability of the vehicle to perform in an acceptable manner are also taken into account. With such factors including the axle manufacturers rated load capacity.
And in regard to such motor vehicles where it is desired to increase their load carrying capacity within the prescribed limits, it is common practice to provide one or more auxiliary axles that are deployed on command to help support the motor vehicle and thereby reduce the weight carried by the axles that normally support the vehicle. Wherein the axles that normally support the vehicle are then referred to as primary axles and include at least one axle with steerable wheels and one or more powered axles with wheels. And the auxiliary axles are referred to as either a pusher axle, tag axle or trailing axle in distinguishing between where and how they are employed to help support the motor vehicle. Wherein a pusher axle is suspended from the motor vehicle chassis in a location to operate between a forwardly-located primary axle with steerable wheels under the control of the vehicle operator and one or more rearwardly-located primary axles with powered wheels. Whereas a tag axle is suspended from the motor vehicle chassis to operate rearward of one or more primary axles with powered wheels but not normally at any substantial distance behind the motor vehicle chassis. And a trailing axle (that has also been referred to as a tag axle and trailing tag axle) is also suspended from the motor vehicle chassis but in a manner to operate at a substantial distance rearward of the motor vehicle chassis.
And in considering the use of such auxiliary axles, their individual weight bearing capacity and their number available in being suitably applied to a particular motor vehicle limits their ability to provide the vehicle support desired. And in the case of trailing axles, their number has been limited for the lack of a suitable suspension system that can accommodate more than one to operate in a satisfactory manner at a substantial distance behind the motor vehicle chassis.
The present invention resides in a dual trailing axle suspension system wherein a pair of axles that serve as trailing axles are directly suspended from an auxiliary chassis with axle suspensions that provide spring action for isolating road induced axle movement from the auxiliary chassis. And the auxiliary chassis is suspended from a chassis of a motor vehicle by an auxiliary chassis suspension adapted to deploy the auxiliary chassis from a stowed location on the motor vehicle to a deployed location at a substantial distance behind the motor vehicle chassis. And the auxiliary chassis suspension is adapted to then cause the auxiliary chassis to help support the motor vehicle chassis to a variable degree by acting on the auxiliary chassis at a location substantially midway between the two axles in a manner determined by whether the spring action provided by the axle suspensions is set or variable.
These and other features of the invention are disclosed in the accompanying drawings and description of exemplary embodiments.
The present invention is shown as applied to a dedicated load-carrying motor vehicle in the form of a dump truck 10 having a cab 12 that serves as a vehicle operator and passenger compartment and a tiltable dump body 14 that serves as a load container and has a latchable top-hinged tail gate 16 for releasing a load when the dump body is tilted. With the cab 12 and tiltable dump body 14 mounted on a chassis 18 in a conventional manner and the truck chassis in turn supported on a road surface 20 by both primary axles and deployable auxiliary axles that are available to help support the truck chassis. With the primary axles consisting of a forwardly-located front axle 22 with steerable wheels 24 at its outboard ends under the control of the vehicle operator and rearwardly-located powered tandem axles 26A and 26B with dual wheels 28A and 28B respectively at their outboard ends. And with the auxiliary axles comprising a pair of trailing axles 30A and 30B with wheels 32A and 32B respectively at their outboard ends.
Wherein the front axle 22 and powered tandem axles 26A and 26B are suspended in parallel relationship from laterally spaced locations on the truck chassis 18. With the front axle 22 located under a front end portion of the truck chassis and the powered tandem axles 26A and 26B located under a rear end potion of the truck chassis and dump body 14. And with the tandem axles 26A and 26B and thus their wheels 28A and 28B powered by a power train of a suitable conventional type that includes an engine and transmission (not shown) that are controlled from the cab by the vehicle operator. And wherein the suspension systems suspending the primary axles from the truck chassis 18 are of a conventional type and of which only a portion of the tandem axles' suspension system 34 is shown and is of the rocking-beam type.
Turning now to the trailing axles 30A and 30B, they are suspended from the dump body 14 and thereby from the truck chassis 18 by a dual trailing axle suspension system 36 according to the present invention as adapted to the dump truck and generally comprising an auxiliary chassis 38 from which the trailing axles 30A and 30B are directly suspended, a carriage 40, a pair of suspension arms 42, and a pair of hydraulically-operated actuators 44. Wherein the auxiliary chassis 38 for clearance purposes with respect to the tailgate 16 when stowing and deploying the trailing axles 30A and 30B as described later is slidably guided and retained on the underside of the carriage 40 by a pair of straight parallel guide rails 46 of U-channel shape that are rigidly fixed to the bottom side of the carriage 40 and slidably receive straight parallel guide members 48 of square tubular shape that are rigidly fixed to a box 49 of rectangular shape that is rigidly fixed to the upper side of the auxiliary chassis 38. See
Referring to
And with the chassis-retracting valve (CRV) 64 opened and the exhaust valve (EV) 66 closed and the chassis-extending valve (CEV) 68 closed and the exhaust valve (EV) 70 opened by the MCVC 72 under vehicle operator control at the CCM 74, the auxiliary chassis 38 is positioned relative to the carriage 40 by the actuator 50 in a fully-retracted position as shown in
Continuing on with the trailing axles 30A and 30B, they are separately directly suspended in parallel relationship at laterally-spaced locations from the frame 76 of the auxiliary chassis 38 by matching axle suspensions 78A and 78B respectively. And the trailing axle wheels 32A and 32B are mounted on the ends of the trailing axles 30A and 30B with steering knuckles 80A and 80B respectively that establish the wheels with a suitable positive caster angle and have steering arms 82A and 82B that are connected by tie rods 84A and 84B respectively that provide the wheels with a suitable toe-in and with the thus interconnected trailing axle wheels stabilized and returned to a normal condition by coil spring/shock absorber assemblies 85A and 85B like that in U.S. Pat. No. 7,775,308 following forced steerage in reaction to the steered turning movement of the truck. Whereby the trailing axle wheels 32A and 32B with the trailing axles deployed in their active condition are enabled to align with forward and rearward truck movement as shown in solid lines in
Continuing on with the separate axle suspensions 78A and 78B, they each comprise a pair of parallel arms 86A and 86B of equal length that are pivotally connected at one end by pivot pins 88A and 88B to the auxiliary chassis frame 76 and pivotally connected at the other end by pivot pins 90A and 90B to the respective trailing axles 30A and 30B inboard of the steering knuckle at this end of the axles. See
Referring now to
And for the operation of the air springs 94A separate from the air springs 94B, there is provided a regulator valve (RV) 108 for regulating the air pressure supplied to the air springs 94A, a pressure sensor (PS) 110 that senses the regulated air pressure and provides feedback for controlling the operation of the regulator valve (RV) 108 in providing the desired pressure for the functioning of the air springs 94A and indication of the pressure presently acting in the air springs 94A, an axle deploying/lowering valve (DV) 112 and associated exhaust valve (EV) 114 that provide for establishing this air pressure in the air springs 94A and thereby deploying/lowering the trailing axle 30A with respect to the auxiliary chassis 38 using the pressure determined by the pressure regulator valve (RV) 108. With the exhaust valve (EV) 114 also providing for exhausting the air springs 94A of pressure to allow the pneumatically-operated actuators 92A when pressurized to forcibly raise the trailing axle 30A to its stowed position with respect to the auxiliary chassis 38 as shown in solid lines in
The valves in the pneumatic circuit 96 are of a conventional electrically-operated type, are interconnected as shown and like the pneumatic circuit 60, the valves are controlled by the MCVC 72 that is under the command of the CCM 74 at the direction of the vehicle operator. And with the regulator valves (RV) 108 and (RV) 116 being operable to regulate the air pressure supplied to the respective air springs 94A and 94B in accordance with controlled voltage input.
Continuing on with the remaining dual trailing axle suspension system components, the carriage 40 and thereby the auxiliary chassis 38 with the trailing axles 30A and 30B are suspended from the dump body 14 and thereby from the truck chassis 18 by the suspension arms 42 and hydraulically-operated actuators 44 that are located to clear the sides of the dump body 14 and are connected with the truck body 14 and thereby with the truck chassis 18 in a reinforced manner by suspension support members 124 that are fixed to the outboard side of a rear end-portion of the truck body. Describing first the suspension arms 42, they are pivotally connected at one end by a pivot pin 126 to a lower end portion of the respective support members 124 to swing about an axis parallel to the primary axles, are rigidly joined together at their other end by a cross-member 128, and are pivotally connected adjacent the cross-member 128 with the ends of a laterally extending tubular shaft 130 by which the carriage 40 and thereby the auxiliary chassis 38 is supported by the suspension arms 42 for pivotal movement. With such pivotal support being provided by the ends of the shaft 130 being supported with flange bearings 132 that are mounted in a reinforced U-shaped channel portion 134 of the suspension arms 42. See
Completing the connection of the suspension arms 42 with the carriage 40 and thereby the auxiliary chassis 38, the auxiliary chassis supporting shaft 130 is received along a mid-portion thereof by a pair of reinforcing tubular sleeves 136 that are welded to the shaft 130 and to bracing structure of the carriage 40 to thereby provide for rigid support of the auxiliary chassis supporting shaft 130 in a fixed position on the carriage. See
Turning now to the hydraulically-operated actuators 44, they are like those in U.S. Pat. No. 7,775,308 wherein they comprise a cylinder 138 and piston 140 and incorporate a gas spring 142. With the gas springs 142 each comprising a piston 144 that is slidably received in the related actuator piston 140 and is acted on at one end by the hydraulic pressure acting on the actuator piston and is acted on at the other end by gas pressure at a prescribed charge pressure that is made available in adequate supply to both gas springs 142 by a gas pressure accumulator tank 146. See
Continuing on with the employment of the hydraulically-operated actuators 44, their cylinders 138 are pivotally connected at their closed end by a pivot pin 148 to the respective suspension support members 124 at a location above the respective pivotal connections of the suspension arms 42 with these support members. And the actuator pistons 140 are pivotally connected at their operating end within and to the channel portion 134 of the suspension arms 42 by a pivot pin 150 at a relatively short distance from where the suspension arms 42 are pivotally connected with the auxiliary chassis supporting shaft 130 that is fixed to the carriage. Whereby the trailing axles 30A and 30B are also located and maintained by the actuators 44 in parallel relationship with the primary axles 22, 26A and 26B and from a higher location on the suspension support members 124 and thus in a significant trussing manner when the trailing axles are deployed with the actuators 44 extended. Moreover, the trailing axles 30A and 30B are located with their axle suspensions 78A and 78B at opposite sides of the pivotal axis of the carriage 40 and auxiliary chassis 38 provided by the auxiliary chassis supporting shaft 130 when the trailing axles are deployed so that the force provided by the actuators 44 on the shaft 130 is located substantially midway between the trailing axles throughout their range of movement relative to the auxiliary chassis 38 and thereby resists the action of both of the air springs 94A and 94B in a substantially balanced structural manner in causing the auxiliary chassis to help support the truck chassis 18 as further described later. While the actuator gas springs 142 and trailing axle suspension air springs 94A and 94B are available to allow the trailing axles 30A and 30B to adjust to differences in elevation when the trailing axle wheels 32A and 32B are supported by a road surface at one elevation and the primary axle wheels 24, 28A and 28B are supported by the road surface at a different elevation as further described later.
Referring again to
Describing now a typical sequence of vehicle operator directed operation of the dual trailing axle suspension system 36 via the CCM 74 and MCVC 72 and starting with establishing the trailing axles 30A and 30B in their stowed condition shown in
With the above established location of the trailing axle wheels 32A and 32B, the auxiliary chassis 38 is then extended by the pneumatically-operated actuator 50 with the pneumatic circuit 60 by (A) closing the chassis-retracting valve (CRV) 64 and exhaust valve (EV) 70 and (B) opening the chassis-extending valve (CEV) 68 and exhaust valve (EV) 66. Thereby positioning the auxiliary chassis 38 so that the rear trailing axle wheels 32B do not interfere with the pivotal movement of the tail gate 16 during subsequent opening and closing. Where after both of the trailing axles 30A and 30B are lowered forcing the trailing axle wheels 32A and 32B downward against the top edge 172 of the dump body sides to thereby firmly hold the carriage 40 and auxiliary chassis 38 and thus the trailing axles in a stowed condition that stabilizes this entire assembly from movement on the truck when the truck is moving and also when dumping a load. With this holding action accomplished with the pneumatic circuit 96 by (A) closing the axle-stowing valves (SV) 100 and (SV) 104 and opening the exhaust valves (EV)102 and (EV) 106 serving the respective pneumatically-operated actuators 92A and 92B, (B) opening the axle-deploying valves (DV) 112 and (DV) 120 and closing the exhaust valves (EV)114 and (EV) 122 serving the respective air springs 94A and 94B, and (C) establishing with the regulator valves (RV) 108 and (RV) 116) the air pressure then supplied to the respective air springs 94A and 94B at a relatively low pressure compared to that provided for forced trailing axle support of the truck chassis 18. And with this holding action accomplished with the assistance of the cross-member 128 by being strategically positioned to engage the top 56 of the carriage 40 to prevent the carriage and thereby the auxiliary chassis 38 from pivoting about the auxiliary chassis supporting shaft 130 in the clockwise direction as viewed in
Then when a load is added to the dump truck 10 and there is recognized that certain trailing axle use is warranted such as that recommended by the axle load monitoring system disclosed in U.S. patent application Ser. No. 14/803,048 entitled “AXLE LOAD MONITORING SYSTEM”, the vehicle operator can deploy the trailing axles 30A and 30B via the CCM 74 and MCVC 72 by releasing the holding of the carriage 40 and auxiliary chassis 38 with the pneumatic circuit 96. And then retracting the auxiliary chassis 38 with respect to the carriage 40 with the pneumatic circuit 60 by (A) opening the chassis-retracting valve (CRV) 64 and exhaust valve (EV) 70, and (B) closing the chassis-extending valve (CEV) 68 and exhaust valve (EV) 66. Whereby the auxiliary chassis 38 is positioned as shown in
Continuing on with the deployment of the trailing axles 30A and 30B, the vehicle operator acting through the CCM 74 and MCVC 72 then effects full extension of the actuators 44 from their condition shown in
Continuing on with the deployment of the trailing axles 30A and 30B, the vehicle operator acting through the CCM 74 and MCVC 72 then closes the axle-stowing valves (SV) 100 and (SV) 104 and opens the exhaust valves (EV) 102 and (EV) 106 serving the respective pneumatically-operated actuators 92A and 92B, and (B) opens the axle-deploying valves (DV) 112 and (DV) 120 and closes the exhaust valves (EV) 114 and (EV) 122 serving the respective air springs 94A and 94B thereby deploying the trailing axles for their supporting role in helping to support the truck chassis 18 with the auxiliary chassis 38. Wherein with the trailing axles 30A and 30B thus deployed for action, the hydraulically-operated actuators 44 then provide a resisting force with the controllable hydraulic pressure that acts on the auxiliary chassis 38 at a location substantially midway between the trailing axles 30A and 30B preventing upward auxiliary chassis movement enabling the air springs 94A and 94B and thereby the auxiliary chassis 38 to help support the truck chassis 18 to a variable degree determined by the air pressure being supplied. And wherein the resisting force acting on the auxiliary chassis 38 provided by the hydraulically-operated actuators 44 as noted previously is applied at its pivotal support on the suspension arms 42 provided by the auxiliary chassis supporting shaft 130 and thereby at a location on the auxiliary chassis 38 between the trailing axles 30A and 30B throughout their operating range of movement relative to the auxiliary chassis in helping to support the truck chassis 18 with the auxiliary chassis 38 and to the degree/extent determined by the air pressure supplied to the trailing axle air springs 94A and 94B by their separate control circuits that provide flexibility in addressing the various circumstances that can exist.
For example, when the trailing axles 30A and 30B are not bearing equal weight as the result of the external load on the auxiliary axles including their weight, the weight distribution of the auxiliary chassis and the remainder of the dual trailing axle assembly or any additional load placed on the auxiliary chassis that is not equally distributed to the two axles, the trailing axle bearing more weight will then require more lift force. And if the trailing axle air springs 94A and 94B are functionally equivalent and the same air pressure is applied to both, the result will be the axle with greater weight will have its air springs more compressed than the other axle since the air springs increase lift force as they are compressed and decrease lift force as they are extended. And this would undesirably result in the auxiliary chassis 38 being angled relative to the road (not level) and with the degree of the angle being proportional to the difference in weight acting on the trailing axles. But with the control circuits for the air spring 94A and 94B being separate, higher air pressure can be applied to the air springs at the trailing axle bearing more weight so that the air springs at both of the trailing axles are at the same ride height but provide different lift force. Furthermore, when equal lift force is desired by the trailing axles and their air springs are not the same, they may not be equal in reacting to the air spring force being applied whereby equal air pressure does not equate to equal down force and as a result, one trailing axle may require higher air spring pressure than the other to achieve the same lift force. Moreover, by providing independent control circuits for the air springs 94A and 94B, the dual trailing axle system according to the present invention lends itself to controlling the lift force on the two trailing axles in a manner that provides improved vehicle handling as well as controlling the operation of the trailing axles 30A and 30B automatically with a control system like that in U.S. patent application Ser. No. 14/803,045 entitled “AUTOMATIC AUXILIARY AXLE CONTROL SYSTEM”.
Continuing on with the operation of the dual trailing axle suspension system 36 with the auxiliary chassis 38 continuing to help support the truck chassis 18, the trailing axle wheels 32A and 32B at one side or both sides of the auxiliary chassis 38 while traveling over a bump in the road surface are allowed to travel up and down reaction in reaction thereto until the trailing axle air springs 94A and 94B are fully compressed and then allowed to continue to travel upward if necessary because of the height of the bump and to the extent allowed of the carriage 40 and auxiliary chassis 38 provided by the actuator gas springs 142 in allowing road-induced retraction of the actuators 44 to accommodate such extended upward travel of the trailing axles. On the other hand, the trailing axles 30A and 30B continue to help support the truck chassis 18 while the trailing axle wheels 32A and 32B at one side or both sides of the auxiliary chassis 38 sequentially travel over a depression such as a pothole in the road surface. And in that case the trailing axles 30A and 30B maintain their support of the truck chassis 18 until the trailing axle air springs 94A and 94B are fully extended and thereby limit further downward trailing axle movement.
Apart from bumps and depressions in the road surface, there can occur significant differences in elevation between the road surface supporting the primary axles 24, 26A and 26B and that supporting the trailing axles 30A and 30B wherein the trailing axles will continue to help in supporting the truck chassis 18. For example, in the road situation shown in
And by further example in the road situation shown in
Referring now to the road situation shown in
Referring now to the road situation shown in
In considering the different road situations that can be encountered including those that have been shown and described, the air springs 94A and 94B are like those generally used to provide lift force with both pusher axles and tag axles. And as these air springs compress, their diameter increases. As a result, when a constant air pressure is supplied to the air springs, the lift force produced by the air springs is least when they are fully extended and their diameters are minimized, and is greatest when they are fully compressed and their diameters are maximized And for example and with reference to the different road situations shown in
Considering now an example of the dual trailing axle suspension system 36 utilizing commercially available trailing axles and air springs, the spacing provided between the trailing axles 30A and 30B is set at 40 inches and the distance provided from the rearmost primary axle 26B to the midpoint between the trailing axles 30A and 30B when deployed is set at 12 feet. With this resulting in the distance from the rearmost primary axle 26B to the forward most trailing axle 30A being 10 feet-4 inches and to the rearmost trailing axle 30B being 13 feet-8 inches. And using commercially available trailing axles 30A and 30B and air springs 94A and 94B with this dimensional arrangement, the dual trailing axle suspension system 36 is capable of allowing elevation changes of the trailing axles 30A and 30B of 16 inches below the trucks primary axles 22, 26A and 26B and 20 inches above the primary axles. Resulting in the downward trailing axle travel limitation of 16 inches being more than sufficient for public roadways as such downward travel at 12 feet behind the truck is capable of handling road grade changes over 10 percent. And if more downward travel of the trailing axles 30A and 30B is desired, this can be provided in the selection of air springs suited to the desired tasks. On the other hand, the relative upward travel limitation of 20 inches allowed of the trailing axles 30A and 30B in this exemplary is dependent on the total volume of the gas accumulator portion of the gas springs 142 associated with the hydraulically-operated actuators 44, the total volume of the hydraulic fluid within the actuators 44, the volume of hydraulic fluid displaced when the actuators retract to allow such upward travel, and the maximum increase in the hydraulic pressure desired. And if more relative upward travel of the trailing axles 30A and 30B is desired, this can be obtained without increasing the hydraulic pressure by simply increasing the gas accumulator volume associated with the gas springs 142.
Describing now the stowing of the trailing axles 30A and 30B following their use and with reference to
And having described the operation of the dual trailing axle suspension system 36 covering various road conditions that can be encountered, it will be appreciated that the resisting force acting on the auxiliary chassis 38 provided by the hydraulically-operated actuators 44 in enabling the air springs 94A and 94B to force the auxiliary chassis 38 to help support the truck chassis 18 is established and maintained at a location between the trailing axles 30A and 30B throughout their range of movement relative to the auxiliary chassis with such varying road conditions. Thereby providing for the net lifting force of the two trailing axles (the lifting force minus any external load including the axle's weight) to directly oppose the resisting force of the hydraulically-operated actuators and thereby be transferred to provide the intended auxiliary support. And if the location of the resisting force on the auxiliary chassis was not provided and maintained between the trailing axles throughout their range of movement relative to the auxiliary chassis, the trailing axles could not lift against the resistance of the hydraulically-operated actuators. And instead, the air springs acting on the trailing axles would extend to their maximum extent allowing the auxiliary chassis to pivot with the result that no lifting force would be applied to help support the motor vehicle chassis. And wherein the forces and torques would balance only by the air springs becoming fully extended and the auxiliary chassis would then be pivoted to such a degree that only the wheels of one of the trailing axles would maintain contact with the road surface while the wheels of the other trailing axle would lose contact with the road surface.
Furthermore, by the dual trailing axle suspension system according to the present invention providing for substantially equal loading of the two trailing axles when the external loading of these two axles is substantially equal, if one of the trailing axles is closer to the pivot axis of the auxiliary chassis than the companion trailing axle, its moment arm is shorter and therefore it applies less torque about the axis than the companion trailing axle at any given force. And therefore, the trailing axle closer to the auxiliary chassis pivot axis must apply a greater lifting force than the companion trailing axle to balance the torques. And the amount of additional force required by the trailing axle that is closer to the auxiliary chassis pivot axis is directly proportional to how much closer it is to the axis thereby making it possible to readily determine how to proportion the loading of the trailing axles with their air springs in providing the desired vehicle support in a particularly advantageous manner For example, if one of the auxiliary axles is 25 percent closer to the pivot axis of the auxiliary chassis, it will require 25 percent more net lifting force/air pressure than the companion trailing axle. And if the external loading of the two trailing axles (the weight that each bear apart from the air spring loading) is substantially equal, then the required lifting force of the two trailing axles and their air spring pressure will be substantially equal in providing the desired motor vehicle chassis support. Furthermore, if the two trailing axles are substantially identical in all respects, the air pressure applied to each axle's air springs will be substantially equal in obtaining the desired vehicle support.
Furthermore, the dual trailing axle suspension system according to the present invention provides for accommodating the widest possible range of external loading imbalance between the two trailing axles if an external load is placed on the auxiliary chassis, or the weight of the auxiliary chassis and trailing axles is not distributed equally to the two axles, and this results in one trailing axle bearing a weight that is significantly more than the other trailing axle. As the system can accommodate this to the maximum degree with either trailing axle bearing the greater load by virtue of the pivot axis of the auxiliary chassis always being located between the two trailing axles throughout their range of movement relative to the auxiliary chassis. And wherein the trailing axle bearing more weight will then need to apply a greater lifting force than the companion trailing axle that can be accomplished with the air pressure provided by its separate pneumatic circuit.
Furthermore, the dual trailing axle suspension system according to the present invention provides for maximizing the pivotal balancing capabilities of the trailing axle wheels when encountering elevation changes such as shown in
It will also be appreciated that other embodiments of the invention can take various forms and whether it is applied to a motor vehicle having powered tandem axles or only one powered axle. Or there may be no load container and depending on the accommodating space on a particular vehicle for stowing the dual trailing axles, there may be no need to provide for relative movement between the auxiliary chassis and carriage for clearance purposes during stowing and deploying of the trailing axles. In that case as shown in
In addition to the above manner of operation of the dual trailing axle suspension system 36, it will also be appreciated that the air springs 94A and 94B can be maintained at a constant pressure thus providing the axle suspensions 78A and 78B with a set spring action instead of the variable spring action provided by varying the pressure in the air springs in determining the degree of help provided by the auxiliary chassis in supporting a motor vehicle chassis. And in that case the hydraulically-operated actuators 108 are operated to apply a force on the auxiliary chassis 38 forcing its downward movement against the air springs 94A and 94B in causing the auxiliary chassis to help support the truck chassis 18 to a variable degree. Instead of the actuators 108 providing a resisting force on the auxiliary chassis 38 and the pressure in the trailing axle air springs 94A and 94B being controlled to vary the support of the truck chassis provided by the auxiliary chassis as previously described.
Furthermore, the dual trailing axle suspension system according to the present invention can have the two axles suspended from the auxiliary chassis 38 with a wide range of axle suspensions having a set spring action in causing the auxiliary chassis 38 to help support the motor vehicle chassis 18 to a variable degree in essentially the same manner as the axle suspensions 78A and 78B when their air springs are provided with a set pressure as described above. For example, there is shown in
Wherein the auxiliary chassis 38 is now supported by trailing axles 178A and 178 B with self-steering wheels 180A and 180B that are linked by tie rods 182A and 182B, stabilized with coil spring/shock absorber assemblies 184A and 184B and suspended from the auxiliary chassis 38 with elastic spring action by semi-elliptic leaf spring suspension systems 186A and 186B. With the suspension systems 186A and 186B comprising a pair of semi-elliptical leaf spring arrangements 188A and 188B extending longitudinally of the auxiliary chassis 38 between the respective trailing axles 178A and 178B and side members 76A of the frame 76 that are braced along their length by transverse cross-members 76B.
And in suspending the trailing axles 178A and 178B, the forward end of the longest and uppermost leaf spring in the leaf spring arrangements 188A are pivotally mounted on the lower side of the opposing frame side member 76A with pin and hanger assemblies 190A, the rearward end of the longest and uppermost leaf spring in the leaf spring arrangements 188B are pivotally mounted on the lower side of the opposing frame side member 76A with pin and hanger assemblies 190B, and a mid-portion of the leaf spring arrangements 188A and 188B is rigidly mounted on the upper side of the trailing axles 178A and 178B with bracket assemblies 192A and 192B respectively. And with the opposing ends of the longest and uppermost leaf spring in the leaf spring arrangements 188A and 188B mounted on the lower side of the opposing frame side member 76A with shackles 194A and 194B respectively that are pivotally connected at their lower end to the ends of a rocking link 196 that is pivotally supported with a pivot pin 198 by a bracket 200 fixed to the lower side of the opposing frame side member 76A.
And wherein the rocking link pivot pins 198 are located above and equidistant from the pivotal connections of the shackles 194A and 194B with the rocking link 196 and the shackles are oriented in a substantially vertical position as shown in
It will also be appreciated that in the case of the two trailing axles 30A and 30B being suspended from the auxiliary chassis 38 with the air spring axle suspensions 78A and 78B, the air springs 94A and 94B without air pressure can be fully compressed with the pneumatically-operated actuators 92A and 92B to thereby minimize the overall height of the auxiliary chassis and trailing axles 30A and 30B in order to clear the tailgate 16 and dump body 14 as the suspension arms 42 are raised and lowered by the hydraulically-operated actuators 44 for stowage and deployment of the auxiliary chassis and thereby the trailing axles 30A and 30B . And in respect to stowage and once the suspension arms 42 are raised to the extent possible on full retraction of the actuators 44 and the auxiliary chassis 38 positioned above the dump body 14, the air springs 94A and 94B or only the air springs 94A can be pressurized forcing the trailing axle wheels 32A and 32B against the top edges 172 of the dump body 14 to thereby firmly hold the auxiliary chassis on the load container when the truck is in motion and when the load container is tilted to dump a load. And wherein the cross-member 128 extending between the suspension arms 42 prevents the carriage 40 and thereby the auxiliary chassis 38 from pivoting in reaction to the pressuring of the air springs.
And with regard to stowage and deployment of the trailing axles 178A and 178B wherein they are suspended from the auxiliary chassis 38 with the leaf spring suspension systems 186A and 186B, the trailing axles will be extended from the auxiliary chassis by the springs in these suspension systems to the maximum extent as the trailing axle wheels 180A and 180B are lifted from a road surface when the hydraulically-operated actuators 44 are retracted. And to compensate for this, the suspension arms 42 and hydraulically-operated actuators 44 are lengthened compared to that utilized with the pneumatically-operated actuators 92A and 92B and air springs 94A and 94 B such that the auxiliary chassis supporting shaft 130 is further distanced from the suspension arm pivot pins 126 to the extent necessary for the trailing axle wheels 180A and 180B to clear the top of the dump body 14 and tail gate 16 as the trailing axles pass over for stowage or deployment. And with the suspension arms 42 angled forward of vertical when the hydraulically-operated actuators 44 are fully retracted and the auxiliary chassis 38 is in the fully stowed position, the auxiliary chassis 38 moves downward toward the dump body after the suspension arms pass vertical in the stowage direction following further retraction of the hydraulically-operated actuators 44.
With the trailing axle wheels 180A and 180B then making contact with the top edges 172 of the dump body 14 before the hydraulically-operated actuators 44 are fully retracted whereby the trailing axle suspension springs are compressed to firmly hold the trailing axle wheels against the top edges of the dump body and thereby hold the auxiliary chassis 38 in place on the dump body when the actuators are eventually fully retracted. And wherein the cross-member 128 extending between the suspension arms 42 prevents the carriage 40 and thereby the auxiliary chassis 38 from pivoting in reaction to the force being applied to compress these trailing axle springs in providing the holding action. And wherein the above sequence of events is reversed to deploy the trailing axles 178A and 178B with extension of the hydraulically-operated actuators 44.
It will also be appreciated that in addition to the above exemplary embodiments, the dual trailing axle suspension system according to the present invention is readily adaptable to a wide range of motor vehicles. For example, the motor vehicle can take various other forms such as refuse trucks, transit concrete mixing trucks, open-bed trucks, utility trucks, and military trucks. Wherein the motor vehicle may have only two primary axles with one of them powered and also one or more pusher axles and/or tag axles for auxiliary use. Or the motor vehicle may have three primary axles with two of them powered as well as one or more pusher axles and/or tag axles for auxiliary use. And the dual trailing axle suspension system is readily adaptable to accommodate such in the manner of operation described above with respect to stowing the auxiliary chassis and thereby the two trailing axles with respect to the particular motor vehicle.
In addition, it will be appreciated that actuators providing the intended operation of helping to support the motor vehicle chassis can be utilized that are not of the hydraulically-operated type shown and take other forms. Such as pneumatically-operated actuators and ball nut and screw actuators that are operated in a manner suited to the objectives of the present invention. And it will also be appreciated that the trailer hitch latching mechanism can be released with a powered actuator rather than manually.
Furthermore, the gas springs that provide for extended upward travel of the trailing axles can have their piston arranged separate from the hydraulically-operated piston to operate in a likewise hydraulic and gas pressured manner and separately provided with a gas accumulator of adequate volume with the prescribed gas pressure charge instead of with a common gas accumulator that serves both of the actuator gas springs. Or the actuator gas springs can be dispensed with if the added trailing axle movement they provide is not called for. And instead of there being only dual trailing axles serving as the auxiliary axles, the motor vehicle may have one or more pusher axles and/or one or more tag axles for added vehicle support. And instead of a tiltable dump body serving as a load container, the load container could be fixed to the motor vehicle chassis and have a roof or a stowing platform for the dual trailing axles that is provided or the motor vehicle may have an open bed with no load container and the carriage and auxiliary chassis with the trailing axles would then be firmly held in the stowed condition on what is available or added. In addition, it will also be recognized that the force acting on the auxiliary chassis could also be located below as well above the trailing axles taking into account in the latter case the provision of adequate ground clearance.
And thus the scope of the invention is intended to be limited only by the accompanying claims.
This invention relates to auxiliary axle suspension systems for motor vehicles and more particularly to trailing axle suspension systems and is related to U.S. patent application Ser. No. 14/803,041 entitled “TRAILER HITCH”, U.S. patent application Ser. No. 14/803,045 entitled “AUTOMATIC AUXILIARY AXLE CONTROL SYSTEM”, and U.S. patent application Ser. No. 14/803,048 entitled “AXLE LOAD MONITORING SYSTEM”.