Complete specification

Surface miner belt drive system

Field of Invention:

The present invention relates to power transmission systems, more particularly to a synchronous belt tensioning arrangement in a multi stage belt drive systems using a single point operation.

Background of the Invention:

Surface mining equipment is a machine which extracts minerals from the mine face with a rotary mining tool fixed to a mobile frame. The mining tool is driven with the prime mover by a mechanical belt drive arrangement. The major limitation here is the overhang that can be permitted on the engine flywheel housing and clutch that are driving the drive pulley. Various methods have been proposed such as multi stage belt drive assembly and twin stage belt drive system to overcome these limitations.

The tensioning arrangement of the multi stage belt drive system uses individual and independent belt tensioning arrangements for each stage which results in more number of components that have to be used in terms of hydraulic cylinders, pulleys, levers, bearings, supporting members, structures etc. This makes the entire system more prone to failures.

In case of twin stage belt drive system the two tensioning arrangements are asynchronous with each other which will make the drive line lesser efficient and lead to reduced life of drive line due to increased wear.

The present invention overcomes the drawbacks of the existing tensioning arrangements in the multi stage belt drive system by employing increased belt length and controlling the same using force values and geometrical proportions. The main objective of our proposed invention is to synchronize the belt tensioning arrangement mechanically by varying the geometric proportions and also simultaneously reduce the total number of components used in the belt drive assembly.

Objective of the Invention:

The main objective of the present invention is to synchronize the belt tensioning arrangement in the multi stage belt drive systems by using a single point operation.

The second objective of the present invention is to reduce the total number of components used in the belt drive assembly.

To Improve Drive Efficiency by simplified single point operation.

Brief description of the prior art:

EP2078144A2 discloses a synchronous belt drive system comprising an ohround sprocket with toothed surface to control the fluctuating torques. The synchronous belt drive system also comprises of one linear portion disposed between two circular portions of constant radius. The linear portion having a length which relates to torque fluctuation amplitude cancels the alternating belt tensions caused by fluctuating load torque. This system is mainly used in automotive and industrial internal combustion engines.

CA2050065C discloses a spring type tensioner which is used in a synchronous belt drive system to solve the belt tension problems associated with camshaft belt drive systems. Fixed idler pulley is used to minimize the resonance tension variations effected due to the dynamic torque variations in the drive system. It operates over a range of temperature conditions to prevent belt tooth failure, tooth jump and shortening of belt. But it is difficult to consistently maintain the belt tensions at a desirable level using this fixed idler system.

WO2002029279A3 provides an improved belt tensioner and a configuration for belt drive systems having a motor/generator. The belt drive system includes a belt tensioner, a crankshaft pulley, an accessory pulley, a motor/generator pulley and a power transmission belt. The improved belt tensioner consists of a first belt tensioner pulley, a biasing member, a connective portion and a second belt tensioner pulley.

The improved version asymmetrically biases the first tensioner pulley and the second tensioner pulley toward movement tending to increase tension upon the power transmission belt. It is mostly used in internal combustion engine and other automotive applications.

WO2002095262A2 deals with asymmetric damping tensioner system for belt drive systems. As the belt drive system operates the belt stretches slightly over its length. This results in decreased belt tension, which causes the belt to slip. Consequently, a belt tensioner is used to maintain the proper belt tension. A biasing member in the tensioner is used to maintain a tension in the belt. The tensioner further comprises a damping mechanism to damp belt vibrations caused by the operation of the engine. Tensioner damping friction is unequal or asymmetric which significantly climinishes overall vibration in the belt during all phases of operation.

EP 2613957 Al discloses an intelligent belt drive system with a belt tensioner which is capable of precognitively anticipating when it is desirable to increase the tension in a belt so as to prevent belt slip. The belt tensioning system comprises a tensioner actuator and a tensioning system controller operatively connected to the tensioner actuator so as to control the tensioning force.

All of the above mentioned belt tensioning systems uses an external element/component such as obround sprocket, fixed idler pulley, tensioner actuator and controller etc to control the belt tension. This also increases the number of components used in the system. The present invention eliminates the drawbacks of existing systems by employing increased belt length and controlling the same using force values and geometrical proportions.

The present invention synchronizes the belt tensioning arrangement mechanically by single point operation and also simultaneously reduces the total number of components used in the belt drive assembly.

Summary of the invention:

The present invention provides a geometric synchronous belt tensioning arrangement in a multi stage belt drive systems using a single point operation. The invention uses a geometrical principle to achieve the desired belt tensioning and power transmission in the belt drive system. The geometric synchronous belt tensioning arrangement comprises a main drive pulley; a primary drive pulley; a belt connecting the main drive pulley and primary drive pulley; a secondary drive; a common shaft connecting the primary drive pulley and secondary drive pulley; a main driven pulley; a belt connecting the main driven pulley and secondary drive pulley; idler pulley for pre-tightening the belt length; a jack arrangement; and a hydraulic cylinder. The jack arrangement is mounted exactly on the perpendicular bisector of the centerline joining the main drive pulley and main driven pulley. This geometric position of jack arrangement is used to maintain the desired belt tension in the multi stage belt drive systems. The jack arrangement is controlled by a hydraulic cylinder which is continuously maintained at a pre-set pressure. The idler pulley is used to offset any manufacturing errors that may arise during the operation. The present invention synchronizes the belt tensioning arrangement mechanically by varying the geometric proportions and also simultaneously reduces the total number of components used in the belt drive assembly.

Brief description of the drawing:

Fig 1 shows the belt tensioning arrangement and its components.

Fig 2 shows the plan view of the belt tensioning arrangement and its components.

Detailed description of the invention with respect to drawing:

The present invention provides a belt tensioning arrangement for a multi-stage belt drive system used in high power drive applications such as Surface miners or other belt driven equipment that has offset between the drive and driven pulleys.

The invention uses a geometrical principle to achieve the desired belt tensioning and power transmission in the belt drive system. The present invention is used maintain a common belt tension value in all stages of the power train, by means of a single point control.

Construction of belt tensioning arrangement:

The belt tensioning arrangement for a multi-stage belt drive system comprises a main drive pulley (14) which is connected to the prime mover transmits power to the primary driven pulley (15) by means of a belt (16). The belt length will be sufficient enough to overlap the main drive pulley (14) and primary driven pulley (15) directly. The primary driven pulley (15) transmits power to the secondary drive pulley (17) by means of a common shaft (18). The secondary drive pulley (17) is connected to the main driven pulley (19) by a belt (20) of bigger length than the earlier belt (16). The idler pulley (21) is used to pre-tighten the longer belt (20) length during the initial assembly of the belts.

The common shaft (18) between primary driven pulley (15) and secondary drive pulley (17) is mounted using a plumber block (22) with sufficiently designed bearings. The plumber block (22) is mounted on mining tool housing using a jack arrangement (23).

The jack arrangement has to be mounted exactly on the perpendicular bisector of the centerline joining the main drive pulley (14) and main driven pulley (18). The jack arrangement is controlled by a hydraulic cylinder (24) which is continuously maintained at a pre-set pressure. This will aid in a common tension value in both the belts. Because of the geometric position of the jack arrangement, when the cylinder is forcing the jack out, elongation will be exactly same in both belts.

In the preferred embodiment the jack arrangement is a telescopic mechanism which is used to move the tensioning arrangement along the perpendicular bisector of the imaginary line connecting the centerlines of the main drive pulley (14) and main driven pulley (18). The tensioning force and movement are achieved by means of various linear motion mechanisms like screw jack, pneumatic cylinder, a hydraulic cylinder.etc.

In the preferred embodiment the telescopic arrangement with linear degree of freedom along its axis is achieved using multiple methods like a scissor arrangement, a telescopic square or rectangular pipe arrangement, a telescopic cylinder locked with key to prevent it from rotation etc. All the systems are sufficiently designed to withstand the torsional loads that arise from the belt pull on the frame.

In the preferred embodiment the bearing housing arrangement with bearings and shaft on which the pulleys are connected is to be sufficiently designed to withstand all the loads that are generated during operation.

In the preferred embodiment, belt tensioning arrangement for a multi-stage belt drive system can be constructed without the use of idler pulley (21) and with same belt length for both belts (16 & 20). This eliminates the need for a separate idler arrangement for both the belts.

In the preferred embodiment the belt tensioning arrangement of the multi-stage belt drive system results in reduction of total number of components being used.

In another embodiment the belt tensioning arrangement results in higher contact arcs of the belts on the pulleys, leading to better power transmission in belt drive system and also extends the life of the components.

The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.

Claim:

1. A geometric synchronous belt tensioning arrangement in a multi stage belt drive systems using a single point operation comprising: a main drive pulley; a primary drive pulley; a belt connecting the main drive pulley and primary drive pulley; a secondary drive pulley; a common shaft connecting the primary drive pulley and secondary drive pulley; a main driven pulley; a belt connecting the main driven pulley and secondary drive pulley; idler pulley for pre-tightening the belt length; a jack arrangement; and a hydraulic cylinder.

2. The geometric synchronous belt tensioning arrangement as claimed in claim 1, wherein the said jack arrangement is mounted exactly on the perpendicular bisector of the centerline joining the main drive pulley and main driven pulley.

3. The geometric synchronous belt tensioning arrangement as claimed in claim 1, wherein the said jack arrangement is a telescopic mechanism with linear degree of freedom along the axis.

4. The geometric synchronous belt tensioning arrangement as claimed in claim 1, wherein the said telescopic arrangement with linear degree of freedom is achieved using scissor arrangement, telescopic square arrangement, rectangular pipe arrangement, telescopic cylinder locked with key to prevent it from rotation.

5. The geometric synchronous belt tensioning arrangement as claimed in claim 1, wherein the said tensioning force and movement are achieved by means of various linear motion mechanisms like screw jack, pneumatic cylinder, hydraulic cylinder.

6. The geometric synchronous belt tensioning arrangement as claimed in claim 1, wherein the said jack arrangement can be replaced by any mechanical or electrical pneumatic propelled motion drives.

7. The geometric synchronous belt tensioning arrangement as claimed in claim 1, is constructed using reduced number of components.

8. The geometric synchronous belt tensioning arrangement as claimed in claim 1, can be used in all equipments and systems with multi stage belt tensioning systems.