Description:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of drive shafts for commercial vehicles with lift axle arrangement, and in specific relates to a rear drive shaft structure and its designing process that increases clearance between the drive shaft and lift axle beam in raised condition.
Background of the invention:
[0002] Haulage refers to transport vehicles that are utilized to carry goods in containers and thereof. Haulage may include a range of vehicles including trucks, tractor units to carry either a towed or a trailered load. In general, these vehicles are classified as heavy-duty vehicles since they are designed to transport heavy loads. The power transmitting components and other components that aid in carrying the load are designed considering the load conditions in view.

[0003] Propeller shafts transmit the rotational power from the gearbox to axle assembly in a vehicle. Several types of vehicles, including semi-trailer truck vehicles and thereof, have multi-axle assemblies so as to adequately support relatively heavy loads. To adjust the load support provided by these multi-axle assemblies, leaf springs and suspension springs are utilized. When the vehicle is carrying a relatively light load, it is desirable to relieve the load transmitting relationship between the vehicle and one or more of the tandem axle/wheel assemblies, and also to disengage the axle/wheel assembly from ground contact so as to reduce the wear of tires. In general, these axles are equipped with a lifting mechanism and are known as lift axles.

[0004] Most of the vehicles with a longer wheelbase are fitted with lift axles. During the unladen condition, when the lift axle is raised, then the clearance between the Rear shaft and the lift axle is very less. In the raised condition of the lift axle, the lift axle beam touches the propeller shaft tube. Even in off-road conditions, the lift axle beam may strike the propeller shaft tube which damages the propeller shaft. When the propeller shaft is rotating at very high speeds, even the slightest strike may cause huge vibrations and noise.

[0005] If any part of the vehicle touches the rear shaft tube continuously, it leads to a bent in the tube causing breakage of complete Rear shaft. In such failure, the propeller shaft damages the surrounding components of the vehicle. Hence the severity of the problem is very high.

[0006] In existing technology, a bent type lift axle beam is often utilized to provide clearance between the lift axle and the propeller shaft. This bent type axle beam is designed with a semi-circle profile at the center to provide clearance between the propeller shaft and the lift axle beam in raised condition. The lift axle passes through the semi-circle profile and sufficient gap is provided to avoid contact. But, the vehicle manufacturer needs to develop a completely new bent type lift axle which is time consuming and incurs huge cost.

[0007] In updated technology, a centralized drop shaft is utilized to allow the driveshaft to pass through. This shaft increases the lift height to which the wheels are raised. The centralized drop of the shaft aids to customize the height to which the wheels can be lifted. The amount of lift obtained depends on the amount of centralized drop on the shaft. The shaft is designed considering maximum load conditions. The shaft is lifted using a bellow type expanding mechanism that also acts as a spring and a shock absorber. However, this configuration requires modifications to the shaft which is very costly. There is a need for an economical way to increase the clearance between the lift axle and the propeller shaft.

[0008] Hence, there exists a need for a drive shaft structure for haulage vehicles that aids to increase the clearance between the lift axle and driveshaft when the lift axle is in raised condition. There is a need for a shaft structure that provides fail safe clearance between the lift axle and the propeller shaft. There is a need for a shaft design with uniform varying sections to reduce the stress and provide uniform stress distribution. There exists a need for a cost-effective solution to increase the clearance between the lift axle and the propeller shaft. There is a need to reduce the damage to the propeller shaft due to less clearance between the shaft and the lift axle.
Objectives of the invention:
[0009] The primary objective of the invention is to provide a rear drive shaft structure for haulage vehicles that aids to increase the clearance between the lift axle and the rear drive shaft assembly when the lift axle is in raised condition.

[0010] The other objective of the invention is to provide a failsafe clearance between the lift axle and the propeller shaft.

[0011] Yet another objective of the invention is to provide a rear shaft structure with reduced cross section at the centre and large diameter at the ends.

[0012] Another objective of the invention is to provide a uniform varying section to the rear shaft to reduce the stress and provide uniform stress distribution.

[0013] Further objective of the invention is to provide a cost-effective solution to increase the clearance between the front axle and the propeller shaft.

[0014] The other objective of the invention is to reduce the damage to the propeller shaft due to less clearance between the shaft and the lift axle.

[0015] Further objective of the invention is to avoid modifications to other parts such as lift axle to increase clearance between the propeller shaft and the lift axle to thereby reduce huge cost and time involved in the process.
Summary of the invention:
[0016] The present disclosure proposes a rear drive shaft structure for haulage vehicles. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0017] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a rear drive shaft structure and its designing process that increases clearance between the drive shaft and lift axle beam in raised condition.

[0018] According to an aspect, the invention provides a rear drive shaft structure for haulage vehicles. The rear drive shaft structure comprises a first end portion, a second end portion, and a middle portion. The rear shaft with uniform varying cross section increases clearance between the driveshaft and the lift axle in raised condition.

[0019] The first end portion is configured with a first cross section and is connected to a short fork. The second end portion is configured with a second cross section and is connected to a tube. The middle portion is configured with a reduced cross section and merged with the first end portion and the second end portion by a uniform taper profile that provides uniform stress distribution. In specific, the first cross section and second cross section are same and larger in diameter compared to the reduced cross section of the middle portion. The intersection points of the merged middle portion are provided with smooth radii to avoid stress concentration.

[0020] The length of the middle portion is larger than width of the lift axle. The first end portion and the second end portion are merged with the middle portion with 30 degrees angle and a merging radius of R100. The rear drive shaft structure provides increased clearance between the drive shaft and the lift axle beam by 40 mm. The rear drive shaft structure is manufactured by special steel forging, followed by machining and precise induction hardening. In specific, the rear drive shaft structure and its connecting shaft components are designed based on the strength requirements of the haulage vehicle.

[0021] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0022] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

[0023] FIG. 1 refers to a rear drive shaft structure for haulage vehicles in accordance to an embodiment of the invention.

[0024] FIG. 2A refers to a front view of a drive shaft assembly with rear drive shaft structure for haulage vehicle in accordance to an embodiment of the invention.

[0025] FIG. 2B refers to an isometric view of a drive shaft assembly with designed shaft structure for haulage vehicle in accordance to an embodiment of the invention.

[0026] FIG. 3A refers to an isometric view of a driveshaft assembled with designed shaft structure in accordance to an embodiment of the invention.

[0027] FIG. 3B refers to an exploded view of a drive shaft assembled with designed shaft structure in accordance to an embodiment of the invention.
Detailed invention disclosure:
[0028] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

[0029] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a rear drive shaft structure and its designing process that increases clearance between the drive shaft and lift axle beam in raised condition.

[0030] According to an exemplary embodiment of the invention, FIG. 1 refers to a rear drive shaft structure 100 for haulage vehicles. The rear drive shaft structure 100 comprises a first end portion 101, a second end portion 102, and a middle portion 103. The rear shaft with uniform varying cross section increases clearance between the driveshaft and the lift axle in raised condition.

[0031] The first end portion 101 is configured with a first cross section. The second end portion 102 is configured with a second cross section. The middle portion 103 is configured with a reduced cross section and merged with the first end portion 101 and the second end portion 102 by a uniform taper profile that provides uniform stress distribution. In specific, the first cross section and second cross section are same and larger in diameter compared to the reduced cross section of the middle portion. The intersection points of the merged middle portion are provided with smooth radii to avoid stress concentration. The rear drive shaft structure is in the form of a knuckle head shape.

[0032] The first end portion 101 and the second end portion 102 are merged with the middle portion 103 with 30 degrees angle and a merging radius of R100. The rear drive shaft structure 100 is manufactured by special steel forging, followed by machining and precise induction hardening. The rear drive shaft structure 100 is machined using CNC turning to obtain required dimensions and later it is hardened using precise induction hardening. In specific, the rear drive shaft structure 100 and its connecting shaft components are designed based on the strength requirements of the haulage vehicle.

[0033] According to another exemplary embodiment of the invention, FIG. 2A and FIG. 2B refer to different views (front view and isometric view) of a drive shaft assembly 200 with rear drive shaft structure 202. The drive shaft 201 is fitted with the rear drive shaft structure 202 to increase the clearance between the lift axle 203 and the rear drive shaft 201. The drive shaft structure 202 provides fail safe clearance between the rear drive shaft 201 and the lift axle 203when the lift axle 203 is in the raised condition.

[0034] According to another exemplary embodiment of the invention, FIG. 3A and FIG. 3B refer to different views (isometric view and exploded view) of drive shaft 300 assembled with designed shaft structure. The drive shaft 300 is fitted with the designed shaft structure 304. The first flange yoke 301 is connected to the short fork 303 using a first universal joint 302. The other end of short fork 303 is connected to the designed shaft structure 304.

[0035] The other end of designed shaft structure 304 is connected with the one end of a cylindrical tube 305. In specific, the short fork 303 and the cylindrical tube 305 are welded to the drive shaft structure 304 using rotary welding. The other end of cylindrical tube 305 is connected with a Rear housing 306. The Rear housing 306 is connected to a pipe dust cover assembly 307.

[0036] The other end of the pipe dust cover assembly 307 is connected to a long fork 308. The pipe dust cover assembly 307 consists of a metallic pipe dust cover and a special multi lip seal. The Long fork 308 comprises a spline at one end and a provision to assemble a second universal joint 309 at the other end. The other end of long fork 308 is connected to the second flange yoke 310 by means of a second universal joint 309.

[0037] The position of the shaft structure 304 in the shaft assembly depends on the position of the lift axle in the vehicle. The drive shaft structure can be assembled with the existing lift axle assembly of a vehicle. The length of the middle portion of the rear drive shaft structure 304 is larger than width of the lift axle. The rear drive shaft structure 304 increases the clearance between the drive shaft and the lift axle beam by 40 mm.

[0038] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a rear drive shaft structure for haulage vehicles that aids to increase the clearance between the lift axle and the rear drive shaft assembly when the lift axle is in raised condition. The drive shaft structure provides a failsafe clearance between the lift axle and the drive shaft. The drive shaft structure is designed with uniform varying section to the rear shaft to reduce the stress and provide uniform stress distribution. The designed shaft structure provides a cost-effective solution to increase the clearance between the front axle and the drive shaft. The drive shaft structure reduces damage to the driveshaft due to less clearance between the shaft and the lift axle. The drive shaft structure design aids to avoid modifications to other parts such as lift axle to increase clearance between the driveshaft and the lift axle to thereby reduce huge cost and time involved in the process.

[0039] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.

Claims:CLAIMS:
I / We Claim:
1. A rear drive shaft structure for haulage vehicles, comprising:
a first end portion configured with a first cross section and connected to a short fork;
a second end portion configured with a second cross section and connected to a tube; and
a middle portion configured with a reduced cross section and merged with said first end portion and said second end portion by a uniform taper profile that provides uniform stress distribution,
whereby said rear shaft with uniform varying cross section increases clearance between the driveshaft and the lift axle in raised condition.
2. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein said rear drive shaft structure provides increased clearance between the drive shaft and the lift axle beam by 40 mm.
3. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein said rear drive shaft structure is manufactured by special steel forging, followed by machining and precise induction hardening.
4. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein length of said middle portion is larger than width of the lift axle.
5. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein said first end portion and said second end portion are merged with said middle portion with 30 degrees angle and a merging radius of R100.
6. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein saidrear drive shaft structure and its connecting shaft components are designed based on the strength requirements of the haulage vehicle.
7. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein said first cross section and said second cross section are same and larger in diameter compared to said reduced cross section of said middle portion.
8. The rear drive shaft structure for haulage vehicles as recited in claim 1, wherein intersection points of the merged middle portion are provided with smooth radii to avoid stress concentration.