2. Prior Art Industrial machines such as a skid loader or a tractor perform frequently the operation for transmitting the power and converting the direction of the power of a power source. Thus, the power transmission used in the industrial machines functions to transmit the driving power of an engine to an object to be driven, as well as to convert the rotational direction of the engine.

For example, the skid loader generally works while repeatedly moving forward and backward and rotating in a narrow space, so it is equipped with a power transmission for transmitting the rotational power of an engine to the left and the right wheels independently. In such a situation, wheels on both sides are rotated in a forward direction in order that the skid loader moves forward, and rotated in a backward direction in order that it moves backward. And wheels on both sides are rotated-

to directions opposite to each other for the rotation of the skid loader.

The conventional power transmission for transmitting the power and converting the direction of the power is classified to a belt type transmission and a hydraulic pump type transmission, according to the driving fashion thereof.

The belt type transmission causes a great loss of the driving power, and is not durable. Furthermore, the belt type transmission cannot perform rapid transmission of the power, and requires a frequent maintenance since the sliding between a belt and a pulley occurs frequently.

The hydraulic pump type transmission generates a great power by reducing the rotational power of an engine properly, and generates great hydraulic power by driving a hydraulic pump using the power. A hydraulic motor is rotated by the hydraulic power generated by the hydraulic pump. The rotational direction can be converted easily by controlling the flowing direction of oil supplied into the hydraulic motor using a simple hydraulic valve.

However, such a hydraulic pump type power transmission has a shortcoming that it requires great manufacturing cost and maintenance cost since it should be manufactured and kept in an airtight state.

Moreover, since the driving power generated by the hydraulic motor is small relative to the high pressure generated by the hydraulic pump, the efficiency for transmitting the power is low. And since it should be equipped with many auxiliary devices, it is voluminous and weighs too much.

Summary of the Invention The present invention has been proposed to overcome the above- described problems in the prior art, and accordingly it is the object of the present invention to provide an industrial power transmission which has a simple construction, consumes small manufacturing cost, and can perform a rapid transmission and conversion of power.

To achieve the above-described object, the present invention provides an industrial power transmission comprising: a first and a second rotational shafts rotated by a power source in directions opposite to each other; a driving shaft connected to an object to be driven; a first and a second clutches for connecting/disconnecting the driving shaft with the first rotational shaft and the second rotational shafts, respectively; and an operating means for controlling the first and the second clutches so that the driving shaft is selectively connected with the first and the second rotational shafts.

Here, the second rotational shaft is connected with the first rotational shaft through even number of gears engaged with each other successively so as to be rotated by the first rotational shaft.

Furthermore, the power source and the first rotational shaft are connected with each other by a plurality of gears engaged with each other successively. Thus, a rotational velocity of the first rotational shaft is reduced in comparison with a rotational velocity of the power source. The ratio of a rotational velocity of the power source to a rotational velocity of the first rotational shaft is changed by a changing means.

Preferably, the driving shaft is connected to the first and the second clutches through a first and second speed-reduction gears, respectively. Furthermore, the driving shaft and the object are connected with each other by a universal joint. Thus, even when the direction of the driving shaft is changed, the rotation of the driving shaft is transmitted stably to the object.

According to the preferred embodiment of the present invention, the rotation of the driving shaft is braked by a brake. The brake is operated by the operating means cooperatively with the first and the second clutches so that the driving shaft is braked only when all of the first and the second clutches are released.

According to another preferred embodiment of the present invention, the first and the second clutches and the brake are encompassed by an oil tank filled up with oil. Then, the first and the second clutches and the brake are protected from dirts.

According to the present invention, the power transmission capable of performing the transmission and conversion of the power effectively is provided. Moreover, the construction of the power transmission is simple, and the size thereof is small. Thus, the manufacturing cost of the power transmission decreases, and the durability thereof increases.

Brief Description of the Drawings The present invention will be better understood and its various objects and advantages will be more fully appreciated from the following

description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a side view of a skid loader to which a power transmission of the present invention is adopted; FIG. 2 is a plan view of FIG. 1; FIG. 3 is a perspective view of the power transmission according to the present invention shown in FIG. 2; FIG. 4 is a development of FIG. 3; FIG. 5 is a transverse sectional view of FIG. 4; FIG. 6 is an enlarged sectional view of the clutch shown in FIG. 2; FIGS. 7 through 9 are enlarged perspective views of the operating device shown in FIG. 2; FIG. 10 is a schematic side view of FIG. 3; and FIG. 11 is another embodiment of the present invention.

Detailed Description of the Preferred Embodiment Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the description of the present embodiment, the example that the power transmission according to the present invention is adopted to a skid loader will be described.

At first, the construction of the skid loader is explained.

FIG. 1 is a side view of a skid loader to which the power transmission according to the present invention is adopted. The skid loader 100 has a base frame 101, an engine 104 for generating power, a

pair of front wheels 103 and a pair of rear wheels 102 driven by the engine 104, a power transmission 1 for transmitting the rotational power of the engine 104 to the front wheels 103 and the rear wheels 102, and a bucket 105 for performing a desired work.

FIG. 2 shows the power transmission 1 according to the present invention together with the skid loader 100 shown in FIG 1. The construction and operation of the power transmission 1 according to the present invention will be described approximately with reference to FIG.

2.

The skid loader 100 has two left wheels 103L and 102L respectively installed on the front and rear areas of the left side thereof, and two right wheels 103R and 102R respectively installed on the front and rear areas of the right side thereof. Four wheels 102L, 102R, 103L and 103R are objects to be driven by the power transmission 1 according to the present invention. When the left wheels 103L and 102L and the right wheels 103R and 102R are driven in a forward direction, the skid loader 100 moves forward, and when the left wheels 103L and 102L and the right wheels 103R and 102R are driven in a backward direction, the skid loader 100 moves backward. When the left wheels I03L and 102L are driven in the forward direction and the right wheels 103R and 102R are driven in the backward direction, the skid loader 100 rotates right, that is clockwise, and when the left wheels 103L and 102L are driven in the backward direction and the right wheels 103R and 102R are driven in the forward direction, the skid loader 100 rotates left, that is counterclockwise.

The power transmission 1 has a bevel gear part 10 connected to the rotational shaft 2 of the engine 104, a change part 20 for changing the rotational velocity of the engine 104, a first driving part 30 for driving the skid loader 100 in the forward direction, a second driving part 50 for driving the skid loader 100 in the backward direction, and a connection part 40 for connecting the first driving part 30 and the second driving part 50 with each other so that the first driving part 30 and the second driving part 50 drive the objects in directions opposite to each other.

On the right area of the skid loader 100 are installed a right driving shaft 38R for driving the right wheels 102R and 103R, a first right clutch 31R for controlling the connection between the first driving part 30 and the right driving shaft 38R, a second right clutch 51R for controlling the connection between the second driving part 50 and the right driving shaft 38R, a right speed-reducing part 37R for reducing the rotational velocity of the right driving shaft 38R, a universal joint 33R for connecting the right driving shaft 38R with the right speed-reducing part 37R, a pair of driving belts 34R and 54R for connecting the right speed-reducing part 37R with the right wheels 102R and 103R, a right brake 35R for braking the right driving shaft 38R, a right operation lever 80R for operating the first and the second right clutches 31R and 51R and the right brake 35R, a right clutch rod 82R for controlling the operation of the first and the second right clutches 31R and 51R according to the operation of the right operation lever 80R, a right brake rod 81R for controlling the right brake 35R according to the operation of the right operation lever 80R,

and a right change lever 71R for controlling the speed-change operation of the change part 20.

According to the operational status of the right operation lever 80R, the first and the second right clutches 31R and 51R operate so that the first driving part 30 and the second driving part 50 are selectively connected to the right driving shaft 38R. Then the right driving shaft 38R rotates. The rotational power of the right driving shaft 38R is transmitted to the right wheels 102R and 103R through the universal joint 33R, the right speed-reducing part 37R and the driving belts 34R and 54R, and thereby the right wheels 102R and 103R are rotated. In such a situation, when the right driving shaft 38R is connected with the first driving part 30, the right wheels 102R and 103R are rotated in the forward direction, and when the right driving shaft 38R is connected with the second driving part 50, the right wheels 102R and 103R are rotated in the backward direction. The right brake 35R operates only when all of the first and the second clutches 31R and 51R are released.

Therefore, when the right driving shaft 38R is connected to the first driving part 30 by the first right clutch 31R or to the second driving part 50 by the second right clutch 51R, the right driving shaft 38R is released from the right brake 35R so as to be capable of rotating.

On the left area of the skid loader 100 are installed a left driving shaft 38L, a first left clutch 31L, a second left clutch 51L, a left speed- reducing part 37L, a universal joint 33L, driving belts 34L and 54L, a left brake 35L, a left operation lever 80L, a left clutch rod 82L, a left brake rod 81L, and a left change lever 71L, which have the constructions

same with those described above. The operations of those are the same as described above.

Hereinbelow, the construction and the operation of the power transmission 1 according to the present invention will be described in more detail with reference to FIGS. 3 through 10. In the following description, the construction of the right part of the power transmission 1 will be mainly described, and the detailed description of the left part thereof will be omitted. The construction and the operation of the left part are identical to those of the right part.

FIG. 3 is a perspective view of the power transmission 1 shown in FIG. 2, and the FIGS. 4 and 5 are development of FIG. 3 in which parts of the power transmission 1 are developed in a plane for the convenience of explanation. Meanwhile, FIG. 10 is a side view of FIG. 3 which shows the connection of the parts of the power transmission 1 schematically.

The bevel gear part 10 is comprised of bevel gears 3 connected to the rotational shaft 2 of the engine 104. The bevel gear part 10 converts the axis of the rotational shaft 2 of the engine 104.

The change part 20 is comprised of a pair of speed changer 21 and 22 for connecting the bevel gear part 10 with the first driving part 30.

The main speed changer 21 has a main speed changer shaft 7 disposed in parallel with a bevel gear shaft 4, and a main speed change gear 8 installed on the main speed changer shaft 7. The sub speed changer 22 has a sub speed changer shaft 12 disposed in parallel with the main speed changer shaft 7, and a sub speed change gear 11 installed on the sub

speed changer shaft 12. A connection gear 5 formed on the bevel gear shaft 4 is engaged with the main speed changer 21, the main speed change gear 8 of the main speed changer 21 is engaged with a neutral gear 6 of a neutral shaft 9, and the neutral gear 6 is engaged with the sub speed change gear 11 of the sub speed changer shaft 12.

The first driving shaft 30 consists of a first rotational shaft 31.

The sub speed changer 22 is engaged with the first rotational shaft 31.

Thus, the rotational power of the rotational shaft 2 of the engine 104 is transmitted to the first rotational shaft 31. The main speed changer 21 and the sub speed changer 22 can be moved along the longitudinal direction thereof by shift forks (not shown), whereby the gear ratio can be changed so that the ratio of the rotational velocity is changed. Thus, the rotational velocity transmitted to the first rotational shaft 31 from the rotational shaft 2 can be changed.

The second driving part 50 consists of a second rotational shaft 51 disposed in parallel with the first rotational shaft 31.

The connection part 40 is comprised of two gears 41 and 42 for connecting the first rotational shaft 31 with the second rotational shaft 51.

Since the connection part 40 is comprised of even number of gears 41 and 42, the first rotational shaft 31 and the second rotational shaft 51 always rotate in directions opposite to each other. Further, the first rotational shaft 31 has the same number of teeth with the second rotational shaft 51, so the rotational velocities thereof are identical with each other.

The first clutch 31R is installed on the first rotational shaft 31, and

the second clutch 51R is installed on the second rotational shaft 51.

FIG. 6 shows the construction of the clutches 31R and 51R. In FIG. 6, only the first clutch 31R installed on the right side of the rotational shaft 31 is shown, however, other clutches have the same construction with that.

The first clutch 3 1 R has a clutch disc 65 fixed to the first rotational shaft 31, a clutch plate 62 and a clutch hub 66 which are installed rotatably on the first rotational shaft 31. The clutch disc 65 is disposed between the clutch plate 62 and the clutch hub 66. On the outer side of the clutch hub 66, a clutch cam 67 and a clutch cam base 68 are installed.

The clutch cam 67 is operated by the clutch rod 82R.

When the clutch rod 82R is not pulled, the clutch cam 67 is positioned at the bottom dead point, whereby the clutch disc 65 is distanced from the clutch plate 62 and the clutch hub 66. Thus, only the clutch disc 65 rotates while the first rotational shaft 31 is rotating.

When the clutch rod 82R is pulled, the clutch cam 67 is positioned at the top dead point, whereby the clutch hub 66 is pressed left by the clutch cam 67. Thus, the clutch plate 62 and the clutch hub 66 are contacted with the clutch disc 65, and thereby the clutch plate 62, the clutch disc 65 and the clutch hub 66 rotate together while the first rotational shaft 31 is rotating.

A first speed-reducing gear 32R is engaged with the first rotational shaft 31, and a second speed-reducing gear 52R is engaged with the second rotational shaft 51. The first and the second speed-reducing gears 32R and 52R are engaged with the driving shaft 38R. The first

speed-reducing gear 32R is not engaged directly with the first rotational shaft 31, but is engaged with the clutch plate 62 installed on the first rotational shaft 31 as shown in FIG. 6. Therefore, the rotation of the first rotational shaft 31 is transmitted to the driving shaft 38R through the first speed-reducing gear 32R only when the first clutch 31R operates. Furthermore, the second speed-reducing gear 52R is not engaged directly with the second rotational shaft 51, too, but is engaged with the clutch plate 62 installed on the second rotational shaft 51.

Therefore, the rotation of the second rotational shaft 51 is transmitted to the driving shaft 38R through the second speed-reducing gear 52R only when the second clutch 51R operates. When all of the first and the second clutches 31R and 51R do not operate, the rotation of the first and the second rotational shafts 31 and 51 is not transmitted to the driving shaft 38R.

The brake 35R is comprised of a brake wheel 35R-2, a connection gear 35R-1 rotated together with the brake wheel 35R-2, and a brake belt 35R-3 for connecting the connection gear 35R-1 with the first speed- reducing gear 32R. The brake wheel 35R-2 is normally in contact with a brake block which is not shown. Therefore, the rotation of the brake wheel 35R-2 is braked by the brake block, by which the first speed- reducing gear 32R is braked. As the brake rod 81R is pulled, the brake block is distanced from the brake wheel 35R-2, so the first speed- reducing gear 32R lies in a rotatable condition.

FIGS. 7 through 9 show an operating device of the power transmission 1. The operating device is comprised of the operation

lever 80R installed on the base frame 101 so as to be capable of pivoting, a hinge pin 91 installed on the lower part of the operation lever 80R, a clutch rod arm 92 and a brake driving member 93 installed respectively on both side of the hinge pin 91, a brake release plate 95 driven by the brake driving member 93, a brake release boss 94 for supporting the brake release plate 95 so as to be capable of pivoting, and a brake rod arm 96 connected with the brake release plate 95. The clutch rod arm 92 is connected to the clutch rod 82R, and the brake rod arm 96 is connected to the brake rod 81R.

When a worker moves the operation lever 80R forward as shown in FIG. 8, the brake driving member 93 pushes the lower part of the brake release plate 95, and thereby the brake release plate 95 drives the brake rod arm 96. Then, the brake rod 81R is pulled by the brake rod arm 96, and the driving shaft 38R is released from the brake 35R. Meanwhile, as the operation lever 80R is moved forward, the clutch rod arm 92 drives the first clutch 31R through the clutch rod 82R so that the first rotation shaft 31 is engaged with the first speed-reducing gear 32R.

Then, the rotation of the first rotational shaft 31 is transmitted to the driving shaft 38R through the first speed-reducing gear 32R, and the rotation of the driving shaft 38R is transmitted to the right wheels 102R and 103R through the universal joint 33R, the speed-reducing part 37R, and the driving belts 34R and 54R. Therefore, the right wheels 102R and 103R are rotated in the forward direction.

When the worker moves the operation lever 80R backward as shown in FIG. 9, the brake driving member 93 pushes the upper part of

the brake release plate 95, and thereby the brake release plate 95 drives the brake rod arm 96. Then, the brake rod 81R is pulled by the brake rod arm 96, and the driving shaft 38R is released from the brake 35R.

Meanwhile, as the operation lever 80R is moved backward, the clutch rod arm 92 drives the second clutch 51R through the clutch rod 82R so that the second rotation shaft 51 is engaged with the second speed- reducing gear 52R. Then, the rotation of the second rotational shaft 51 is transmitted to the driving shaft 38R through the second speed- reducing gear 52R, and the rotation of the driving shaft 38R is transmitted to the right wheels 102R and 103R through the universal joint 33R, the speed-reducing part 37R, and the driving belts 34R and 54R. Therefore, the right wheels 102R and 103R are rotated in the backward direction.

When the operation lever 80R lies in the middle position as shown in FIG. 7, all of the first and the second clutches 31R and 51R do not operate, and thereby the first rotational shaft 31 is disconnected with the first speed-reducing gear 32R and the second rotational shaft 51 is disconnected with the second speed-reducing rear 52R. Furthermore, since the brake rod 81R is not pulled, the first speed-reducing gear 32R is braked by the brake 35R, whereby the driving shaft 38R and the right wheels 102R and 103R are braked.

As described above, the brake 35R operates according to the operation of the operation lever 80R cooperatively with the first and the second clutches 31R and 51R. Furthermore, the brake 35R brakes the driving shaft 38R only when all of the first and the second clutches 31R

and 51R are released.

On the left part of the power transmission 1 are installed a first and a second clutches 31L and 51L, a first and a second speed-reducing gears 32L and 52L, a brake 35L, a brake wheel 35L-2, a connection gear 35L-1, a brake belt 35L-3, a brake rod 81L, a clutch rod 82L, an operation lever 80L, a driving shaft 38L, a speed-reducing part 37L, a universal joint 33L, driving belts 34L and 54L, and a change lever 71L.

The construction and the operation of those are the same as described above.

Hereinbelow, the operation of the skid loader 100 having the power transmission 1 according to the present invention will be described.

As the engine operates, the rotational velocity of the engine 104 is reduced by the change part 20, and the first and the second rotational shafts 31 and 51 are rotated at the reduced velocity in directions opposite to each other. In such a situation, the rotational direction of the first rotational shaft 31 is the direction that the skid loader 100 moves forward, and the rotational direction of the second rotational shaft 51 is the direction that the skid loader 100 moves backward. The worker can change the speed-reduction ratio by controlling the change levers 71R and 71L.

As the worker moves the right operation lever 80R forward, the first speed-reducing gear 32R is released from the brake 35R, and simultaneously, the first rotational shaft 31 is engaged with the first speed-reducing gear 32R by the first clutch 31R. Then, the driving shaft 38R is rotated in the forward direction, and thereby the right wheels

102R and 103R are rotated in the forward direction.

As the worker moves the right operation lever 80R backward, the first speed-reducing gear 32R is released from the brake 35R, and simultaneously, the second rotational shaft 51 is engaged with the second speed-reducing gear 52R by the second clutch 51R. Then, the driving shaft 38R is rotated in the backward direction, and thereby the right wheels 102R and 103R are rotated in the backward direction.

As the worker operates the left operation lever 80L according to the same fashion as described above, the left wheels 102L and 103L are rotated in the forward or the backward direction. The worker moves both operation levers 80R and 80L forward when he wants to move the skid loader 100 forward, and moves both operation levers 80R and 80L backward when he wants to move the skid loader 100 backward. The worker moves the left operation lever 80L backward and moves the right operation lever 80R forward when he wants to rotate the skid loader 100 left, and moves the left operation lever 80L forward and moves the right operation lever 80R backward when he wants to rotate the skid loader 100 right. Therefore, the direction of the skid loader 100 can be changed easily even in a narrow space.

According to the present invention, as described above, the rotational power of the first and the second rotational shafts 31 and 51 which are rotated continuously is selectively transmitted to the driving shafts 38R and 38L, so the connection/disconnection and the conversion of the driving power are performed effectively. Furthermore, since the power transmission 1 is comprised of the assembly of gears and clutches

31R, 31L, 51R and 51L, the construction thereof is simple and the size thereof is small. Therefore, manufacturing cost decreases, and the durability increases. Meanwhile, since the driving shafts 38R and 38L are braked by the brakes 35R and 35L while the rotational power of the first and the second rotational shafts 31 and 51 is not transmitted to the driving shafts 38R and 38L, the position of the skid loader 100 is fixed steadfastly. Therefore, the skid loader 100 can work while being fixed steadfastly, so it is easy to do the work. In special, since the driving shafts 38R and 38L are connected with the wheels 102R, 102L, 103R and 103L by the universal joints 33R and 33L, the driving power of the driving shafts 38R and 38L are transmitted stably even when the axis direction of the driving shafts 38R and 38L is changed by the weight of the skid loader 100.

FIG. 11 shows another embodiment of the present invention. In the present embodiment, the construction of the skid loader 100 and the power transmission 1 is identical with the above-described embodiment.

In the present embodiment, the power transmission 1 is encompassed by an oil tank 1-1. The oil tank 101 encompasses the clutches 31R, 31L, 51R and 51L and the brakes 35R and 35L airtightly, and the oil tank 1-1 is filled up with oil of which frictional coefficient is great. Since the skid loader 100 is used in a place in which much dirts exist, the clutches 31R, 31L, 51R and 51L and the brakes 35R and 35L may wear down easily. However, according to the present embodiment, the clutches 31R, 31L, 51R and 51L and the brakes 35R and 35L are protected from the dirts, so they do not wear down easily.

According to the present invention, the power transmission 1 capable of performing the transmission and conversion of the power effectively is provided. Moreover, the construction of the power transmission 1 is simple, and the size thereof is small. Thus, the manufacturing cost decreases, and the durability increases.

Therefore, the loss of the driving power is reduced, the power is transmitted rapidly, and maintenance is not troublesome, in comparison with the conventional belt type power transmission. Furthermore, manufacturing cost and maintenance cost are low, the efficiency for transmitting the power is high, auxiliary devices are not needed, the volume is small, and the weight is low, in comparison with the conventional hydraulic pump type power transmission.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, wherein the spirit and scope of the present invention is limited only by the terms of the appended claims.