WO2017051954A1

WO2017051954A1 - Pneumatic tire compactor speed adjusting system

Info

Publication number: WO2017051954A1
Application number: PCT/KR2015/010174
Authority: WO
Inventors: Dinesh DURAISAMY
Original assignee: Volvo Construction Equipment Ab
Priority date: 2015-09-25
Filing date: 2015-09-25
Publication date: 2017-03-30

Abstract

A maximum speed adjusting system for a pneumatic tire compactor is disclosed. The maximum speed adjusting system includes a hydraulic motor circuit with a speed shift solenoid. The hydraulic motor circuit is configured in such way that maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized. Further, a speed switch is connected to the speed shift solenoid. The speed switch is configured to selectively energize the speed shift solenoid. Further, a connector is connected between the speed switch and the speed shift solenoid. The connector is configured to be disconnected when the operating weight of the pneumatic tire compactor is larger than a preset value.

Description

PNEUMATIC TIRE COMPACTOR SPEED ADJUSTING SYSTEM

The present disclosure relates to a pneumatic tire compactor, and more particularly, to an apparatus for adjusting maximum speed of the pneumatic tire compactor according to the operating weight of the pneumatic compactor.

Compactors or road rollers are construction vehicles used to compact dirt, gravel, asphalt and other compactable surfaces, for example, in the construction of roads. As they use the weight of the vehicle including rollers to compress the surface being rolled, the working parts for compacting are mostly steel drums. However, pneumatic tire rollers have their own function and merit distinguished from compactors having steel drums. For example, pneumatic tire compactors are used to follow normal steel drum compactors to even the surface more smoothly and densely in road construction. Such as this, pneumatic tire rollers are generally used to travel on freshly compacted asphalt giving a kneading effect to finished road with its operating weight and suspension cylinder mounted on to the machine.

As the operating weight of pneumatic tire compactors needs to be adjusted according to road conditions, pneumatic tire compactors have ballasting compartments and operating weight of the machine can be increased by ballasting with a variety of ballast options, such as water, steel shot and sand. For example, for the case of a pneumatic tire compactor from Volvo, the operating weight can vary from 10 to 24 tons via ballasting, from none ballasted to fully ballasted state.

For time and efficiency sake, it is surely desirable that pneumatic tire compactors can be operated at higher speed. In this regard, the inventor becomes to know from a brief survey that customers generally want to have maximum speed of 20 km/h from a machine by Volvo, the operating weight of which can be varied from 10 to 24 tons via ballasting. However, due to current design and safety constraints, high speed like this is not viable for the machine. As the operating weight of pneumatic tire compactors increases via ballasting, inertia of the machine becomes bigger, and thus, to operate the machine safely, more braking torque should be provided by the hydraulic motor driving the machine. However, there is a limitation in the braking torque the motor can provide and maximum braking torque is fixed for the given hydraulic motor. Thus, maximum speed of the machine is regulated to 13 km/h because the hydraulic motor adopted in the machine cannot provide enough braking torque to meet safety requirement when the fully ballasted machine operates faster than this speed.

20 km/h speed specification would be possible, if we adopt external braking system assisting braking done by the motor. However, the external braking system will cost a lot and, moreover, it can spoil the asphalt mat on which the machine works.

As described above, maximum speed of the machine is regulated to 13 km/h to meet safety requirement applied to fully ballasted machine. However, we find out that only around 20 % of the duty cycle of the machine is fully ballasted, which means that 80% of the duty cycle can be done in higher speed without any safety problem.

Although we explained a case related to the machine by Volvo as an example, the problem described above is common to all pneumatic tire compactors. Accordingly, it would be beneficial to provide a simple and inexpensive system to increase overall maximum speed of pneumatic tire compactors and to improve efficiency thereby.

According to one aspect of the present disclosure, there provides a maximum speed adjusting system for a pneumatic tire compactor. The maximum speed adjusting system includes a hydraulic motor circuit with a speed shift solenoid. The hydraulic motor circuit is configured in such way that maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized. Further, a speed switch is connected to the speed shift solenoid. The speed switch is configured to selectively energize the speed shift solenoid. Further, a connector is connected between the speed switch and the speed shift solenoid. The connector is configured to be disconnected when the operating weight of the pneumatic tire compactor is larger than a preset value.

According to another aspect of the present disclosure, there provides a pneumatic tire compactor. The pneumatic tire compactor includes a power source and a hydraulic motor circuit with a speed shift solenoid. The hydraulic motor circuit is powered by the power source and configured in such way that maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized. Further, a speed switch is connected to the speed shift solenoid. The speed switch is configured to selectively energize the speed shift solenoid. Further, a connector is connected between the speed switch and the speed shift solenoid. The connector is configured to be disconnected when the operating weight of the pneumatic tire compactor is larger than a preset value.

Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

The present disclosure is advantageous in that high speed can be achieved without having expensive external brakes and better road quality and operatoer can operate the machine at higher speed without any safety constraint (added braking power) when the machine, for example, is not fully ballasted. The machine can be very productive, for example, at non-ballasted duty cycle without expensive external brakes and better road quality.

FIG. 1 is a perspective view of a pneumatic tire compactor according to one embodiment of the present disclosure;

FIG. 2 is a perspective view of the front tires and suspension cylinders of the pneumatic tire compactor; and

FIGS. 3 to 6 are schematic circuit diagrams of a maximum speed adjusting system according to one embodiment of the present disclosure in different conditions, respectively.

Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While the present disclosure will be described in conjunction with the following embodiments, it will be understood that they are not intended to limit the present disclosure to these embodiments alone. On the contrary, the present disclosure is intended to cover alternatives, modifications, and equivalents which may be included within the spirit and scope of the present disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, embodiments of the present disclosure may be practiced without these specific details.

FIG. 1 represents an exemplary machine 100 according to one embodiment of the present disclosure. More specifically, the machine 100 is a pneumatic tire compactor 102 as shown in the illustrated embodiment.

The pneumatic compactor 102 may be useful for compacting and/or increasing density of a compaction surface, such as dirt, gravel, and/or bituminous mixtures. The pneumatic tire compactor 102 has set of compacting wheels containing pneumatically inflated front and

rear tires

104, 106, both the front and the

rear tires

104, 106 being rotatably mounted on a main frame 108 of the pneumatic compactor 102.

The main frame 108 of the pneumatic tire compactor 102 may also support ballast or ballast tank (not shown) for providing an additional weight to the pneumatic tire compactor 102. The additional weight, ballast weight, may be added in accordance with and/or to meet surface compaction demands. The ballast weight can include sand or water, or other substances like steel shot.

FIG. 2 illustrates the front tires 104 and suspension cylinders 202 of the pneumatic tire compactor 102. Although not shown, the rear tires 106 can also have their suspension cylinders. As such, each of the pair of the

tires

104, 106 is supported by a suspension cylinder 202. With this configuration, as the operating weight of the pneumatic tire compactor 102 increases, ground reaction force on the suspension cylinder 202 will increase and the pressure inside the suspension cylinder 202 will also increases. To make use of this pressure value depending on the operating weight of the pneumatic tire compactor 102, a pressure switch 210 having two

terminals

212, 214 is mounted in communication with the suspension cylinder 202.

FIGS. 3 to 6 show schematic circuit diagrams of a maximum speed adjusting system according to one embodiment of the present disclosure in different conditions, respectively. As shown, for example, in FIGS. 3 and 5, the pressure switch 210 is configured to be able to connect or disconnect the two

terminals

212, 214, and switching between connection state and disconnection state depends on the pressure exerted to the pressure switch 210, which is the same as the pressure inside the suspension cylinder 202 because the pressure switch 210 is in communication with the suspension cylinder 202. The threshold value or preset value of disconnection can be changed by adjusting resisting force provided, for example, by a spring 216 installed inside the pressure switch 210.

As can be seen in the accompanying figures, one terminal 212 of the pressure switch 210 is connected to a speed switch 220, and the other terminal 214 is connected to a speed shift solenoid 232 of a hydraulic motor circuit 230. The speed switch 220 is to be controlled by an operator, and may be installed in a dashboard near an operator seat. The speed switch 220 is connected to the speed shift solenoid 232 via the pressure switch 210, and thus, when the pressure switch is in connection state, the speed shift solenoid 232 can energized by controlling of the speed switch 220.

The speed shift solenoid 232, also called as two speed solenoid in the art this disclosure belongs to, belongs to a hydraulic motor circuit 230 which has a hydraulic motor 234 powered by a power source and complicated hydraulic components connected to the hydraulic motor 234, which are omitted in the drawings. The hydraulic motor circuit 230 is configured in such way that there are two different modes with different maximum speed of the pneumatic tire compactor 102, and the maximum speed of the pneumatic tire compactor 102 is higher when the speed shift solenoid 232 is energized. For the purpose of focusing on features related to present disclosure, many components of the hydraulic motor circuit 230 are omitted and even the remaining components of the hydraulic motor circuit 230 are illustrated in a simplified and conceptual manner. However, a person of ordinary skill in the art will easily understand structure of the hydraulic motor circuit 230 which can provide two different maximum speeds for the pneumatic tire compactor 102, the maximum speed of the pneumatic tire compactor 102 being higher when the speed shift solenoid 232 is energized. Thus, detailed explanation about the hydraulic motor circuit 230 including the speed shift solenoid 232 is not given in this disclosure.

The pressure switch 210 is just an example, and any type of connector connected between the speed switch 220 and the speed shift solenoid 232 can be used only if the connector is configured to be disconnected when the operating weight of the pneumatic tire compactor 102 is larger than a preset value. When using the pressure switch 210, the pressure switch 210 does not directly react to the operating weight of the pneumatic tire compactor 102 but, as an indirect manner, react to the pressure inside the suspension cylinder 202 which changes according to the operating weight of the pneumatic tire compactor. However, a switch or a connector configured to receive output signals form a load cell which can measure reaction force of axle of the front tires or the rear tires, and configured to be disconnected when it is determined that the operating weight of the pneumatic tire compactor is larger than a preset value based on the output signal based on the signals.

The following description is now provided about the operation of the maximum speed adjusting system described above.

Referring to FIG. 3, when the operating weight of the pneumatic tire compactor 102 is not greater than a preset value of the pressure switch 210, the pressure switch 210 is in connection state in which the two

terminals

212, 214 are connected each other. As the speed shift solenoid 232 is not energized, a fluid flow into the speed shift solenoid 232 (an arrow on the right of the speed shift solenoid) cannot pass the speed shift solenoid 232, and the motor control circuit 230 does not operate in a mode with higher maximum speed.

Referring to FIG. 4, from the state illustrated in FIG. 3, when an operator control the speed switch 220 in a hope of operating the pneumatic tire compactor 102 in higher speed, i.e., with higher maximum speed, electric power from upstream of the speed switch 220 is delivered to the speed shift solenoid 232, and the speed shift solenoid 232 is energized. When the speed shift solenoid 232 is energized, the fluid flow into the speed shift solenoid 232 (an arrow on the right of the speed shift solenoid) can pass the speed shift solenoid 232 and a fluid flow out of the speed shift solenoid 232 (an arrow on the left of the speed shift solenoid) is provided to the hydraulic motor 234, and thus, the motor control circuit 230 operates in the mode with higher maximum speed.

Referring to FIG. 5, when the operating weight of the pneumatic tire compactor 102 is greater than a preset value of the pressure switch 210, the pressure switch 210 is in disconnection state in which the two

terminals

212, 214 are disconnected each other. As the speed shift solenoid 232 is not energized, a fluid flow into the speed shift solenoid 232 (an arrow on the left of the speed shift solenoid) cannot pass the speed shift solenoid 232, and the motor control circuit 230 does not operate in the mode with higher maximum speed.

Referring to FIG. 6, from the state illustrated in FIG. 5, when an operator control the speed switch 220 in a hope of operating the pneumatic tire compactor 102 in higher speed, i.e., with higher maximum speed, electric power from upstream of the speed switch 220 is not delivered to the speed shift solenoid 232 as the pressure switch 210 is disconnected, and the speed shift solenoid 232 is not energized. As the speed shift solenoid 232 is not energized, a fluid flow into the speed shift solenoid 232 (an arrow on the left of the speed shift solenoid) cannot pass the speed shift solenoid 232, and the motor control circuit 230 does not operate in the mode with higher maximum speed.

Alternatively, the speed switch 220 can be configured to constantly deliver electric power from upstream of the speed switch 220 to downstream of the speed switch 220, that is the speed switch 220 is constantly closed or ON. In that case, the maximum speed will be automatically selected only by the state of the pressure switch 210. This may seem to be more convenient than those depicted in FIGS. 3 to 6. However, as the operator occasionally wants to lower the maximum speed deliberately due to gradient of roads, the speed switch 220 which can be ON and OFF is not meaningless.

The lower maximum speed which is a maximum speed for the case of FIGS. 3, 5 and 6, is a value adapted to fully ballasted state. The higher maximum speed which is a maximum speed for the case of FIG. 4, can be a value adapted to, for example, 50% ballasted state. That is, the higher maximum speed can be chosen such that 50% ballasted pneumatic tire compactor cannot operate safely over that speed. In that case, the preset value or threshold value of the pressure switch 210 is adapted to the pressure corresponding to 50% ballasted state, or the preset value or threshold value of the pressure switch 210 is adapted to the pressure corresponding to 52 to 54% ballasted state adopting a margin of 2 to 4% for more safety.

The higher maximum speed and corresponding preset value of the pressure switch 210 will be chosen by a designer of the machine, and the designer will determine them by analyzing needs of customer, actual duty cycle of similar machine in use, and so on.

On one hand, for 0~50% ballasted state, by controlling the speed switch 220, the operator can operate the pneumatic tire compactor with higher maximum speed, and thus, overall maximum speed of the pneumatic tire compactor is increased and efficiency is increased without any safety problem.

On the other hand, for more than 50 % ballasted state, even if the operator control the speed switch 220 to get the higher maximum speed, the speed shift solenoid 232 will not be energized as the pressure switch 210 is disconnected, and the lower maximum speed which is adapted to fully ballasted state will be applied and there is no safety problem.

Although the invention has been described with reference to the preferred embodiments in the attached figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.

The present disclosure is applicable to a construction vehicle, and more specifically, to a pneumatic tire compactor.

Claims

A maximum speed adjusting system for a pneumatic tire compactor, the maximum speed adjusting system comprising:

a hydraulic motor circuit with a speed shift solenoid, the hydraulic motor circuit configured in such way that maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized;

a speed switch connected to the speed shift solenoid, the speed switch configured to selectively energize the speed shift solenoid; and

a connector connected between the speed switch and the speed shift solenoid, the connector configured to be disconnected when the operating weight of the pneumatic tire compactor is larger than a preset value.
The maximum speed adjusting system as claimed in claim 1, wherein the connector is a pressure switch in communication with a suspension cylinder of the pneumatic tire compactor, the pressure switch has two terminals each of which is connected to the speed switch and the speed shift solenoid, and the pressure switch has a preset value of pressure causing disconnection of the two terminals.
The maximum speed adjusting system as claimed in claim 1, wherein the hydraulic motor circuit is configured in such way that there are two different modes with different maximum speed of the pneumatic tire compactor, and the maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized.
The maximum speed adjusting system as claimed in claim 1, wherein the preset value is selected such that the pneumatic tire compactor having the operating weight corresponding to the preset value can be operated safely at the higher maximum speed.
The maximum speed adjusting system as claimed in claim 1, wherein the speed switch is configured to constantly deliver electric power from upstream of the speed switch to downstream of the speed switch, that is, to be constantly ON.
A pneumatic tire compactor comprising:

a power source;

a hydraulic motor circuit with a speed shift solenoid, the hydraulic motor circuit configured in such way that maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized;

a speed switch connected to the speed shift solenoid, the speed switch configured to selectively energize the speed shift solenoid; and

a connector connected between the speed switch and the speed shift solenoid, the connector configured to be disconnected when the operating weight of the pneumatic tire compactor is larger than a preset value.
The pneumatic tire compactor as claimed in claim 6, wherein the connector is a pressure switch in communication with a suspension cylinder of the pneumatic tire compactor, the pressure switch has two terminals each of which is connected to the speed switch and the speed shift solenoid, and the pressure switch has a preset value of pressure causing disconnection of the two terminals.
The pneumatic tire compactor as claimed in claim 6, wherein the hydraulic motor circuit is configured in such way that there are two different modes with different maximum speed of the pneumatic tire compactor, and the maximum speed of the pneumatic tire compactor is higher when the speed shift solenoid is energized.
The pneumatic tire compactor as claimed in claim 6, wherein the preset value is selected such that the pneumatic tire compactor having the operating weight corresponding to the preset value can be operated safely at the higher maximum speed.
The pneumatic tire compactor as claimed in claim 6, wherein the speed switch is configured to constantly deliver electric power from upstream of the speed switch to downstream of the speed switch, that is, to be constantly ON.