WO1999002865A1

WO1999002865A1 - Energy recovery system

Info

Publication number: WO1999002865A1
Application number: PCT/CA1998/000678
Authority: WO
Inventors: Alain Villeneuve
Original assignee: Alain Villeneuve
Priority date: 1997-07-11
Filing date: 1998-07-10
Publication date: 1999-01-21
Also published as: CA2209703A1; AU8328498A

Abstract

The system (10) comprises a deviation circuit (12) having an inlet (14) and an outlet (16) to be connected to the hydraulic fluid supply line (102) of a mechanism (108) subjected to high-frequency shocks. The shocks travel back in the supply line (102) in the upstream direction. The inlet (14) and the outlet (16) are in spaced relationship on the supply line (102), the inlet (14) being upstream on the supply line (102) with reference to the outlet (16). A piloted valve is used to admit a portion of the fluid during a shock. The deviated fluid flows through a first check valve (20) mounted on the deviation circuit (12) downstream the inlet (14). Then, an accumulator (22) is connected to the deviation circuit (12) at a location downstream the first check valve (20). Some of the deviated hydraulic fluid flows in and out of the accumulator (22) in proportion of the pressure at that location. Finally, a second check valve (24) is mounted on the deviation circuit (12) between the location where the accumulator (22) is connected and the outlet (16). The result is that a portion of the shocks is trapped in the deviation circuit (12) and the stored energy from the previous stroke is reinjected into the supply line (102) as positive energy, thereby lowering the overall vibrations and the energy to operate the mechanism (108). A method of recovering energy in the hydraulic fluid supply line (102) of a mechanism (108) subjected to high-frequency shocks is also disclosed.

Description

ENERGY RECOVERY SYSTEM

BACKGROUND

The propagation of shocks in the hydraulic circuit is a problem experienced with the vast majority of hydraulically-powered mechanisms subjected to high- frequency shocks against another object. This problem is especially important in the case of impact tools, such as rock drills, whereby the recoil after each impact of the tool head with the rock surface creates a shock in the upstream direction. As a result, these successive shocks increase the power that has to be supplied by the hydraulic motor to operate the mechanism, create excessive wear of the hydraulic components and reduce the service life of the mechanism. The risks of cavitation in the hydraulic circuit are also very high with these shocks, especially in the case of rock drills, where cavitation is the main cause of major internal damages. Yet, other problems are experienced due to these high-frequency shocks propagating upstream, such as the increased risks of failures due to fatigue and excessive external vibrations that may create health problems to the operators of the apparatus on which the mechanism is mounted.

A common attempt to lower those shocks is to use one or more accumulators directly connected to the supply line in order to damp them. However, these arrangements have not completely solved the problems since they usually only absorb a limited portion of the shock peaks. Other complicated arrangements have been thought of but none have been proven to be effective. Therefore, the control of shocks remains a paramount concern, especially for the tool manufacturers whose numerous arrangements have not been satisfactory in spite of all the resources put forward to deal with the problem.

There was thus a need to provide a system and a method to solve the problem of these shocks. Such system should effectively lower those shocks in a hydraulic supply line and also restitute a large portion of the negative energy thereof back into the supply line as positive energy. SUMMARY

The present invention provides an arrangement that deviates a portion of the hydraulic fluid from the supply line of the mechanism to trap a substantial portion of the shock pressure peaks and restitute them back into the supply line so that the energy thereof be added to the energy to be supplied to the mechanism. To do so, the energy recovery system comprises a deviation circuit having an inlet and an outlet to be connected to the supply line. The inlet and outlet are in spaced relationship on the supply line, the inlet being upstream on the supply line with reference to the outlet. A valve means is used for restricting the flow of hydraulic fluid.

The flow of hydraulic fluid in the deviation circuit is occurring in one direction, namely from the inlet to the outlet. To do so, a first check valve is mounted on the deviation circuit downstream the inlet. Then, an accumulator is connected to the deviation circuit at a location downstream the first check valve. Some of the deviated hydraulic fluid flows in and out of the accumulator in proportion of the pressure at that location. Finally, a second check valve is mounted on the deviation circuit between the location where the accumulator is connected and the outlet.

The energy recovery system may comprises two, three or more accumulators, each separated by check valves to keep the flow in one direction.

A method of recovering energy in the hydraulic fluid supply line is also provided. This method comprises the steps of: deviating a portion of the hydraulic fluid through a deviation circuit having an inlet and an outlet to be connected to the supply line, the inlet and the outlet being in spaced relationship; passing the deviated hydraulic fluid through a first check valve mounted on the deviation circuit downstream the inlet; damping shocks in the deviated hydraulic fluid at a location downstream the first check valve; passing the deviated hydraulic fluid through a second check valve mounted on the deviation circuit between the location where the shocks are damped and the outlet; and returning the deviated hydraulic fluid into the supply line.

A non restrictive description of the preferred embodiments will now be given with reference to the appended drawings.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 is a schematic diagram of an energy recovery system according to a preferred embodiment of the present invention, as used in conjunction with a typical hydraulic circuit of a rock drill.

IDENTIFICATION OF THE COMPONENTS

The following is a list of the reference numerals, along with the names of the corresponding components, that are used in the appended figure and in the description.

10 energy recovery system

12 deviation circuit

14 inlet 16 outlet

20 first check valve

22 accumulators

24 intermediary check valves

26 final check valve 30 pressure control valve

100 rock drill (example of application)

102 supply line

104 hydraulic pumps 106 hydraulic motors

108 actuator

110 conventional accumulator

DESCRIPTION

FIG. 1 shows an energy recovery system (10) according to a preferred embodiment of the present invention. The illustrated system (10) is connected to the hydraulic circuit of a rock drill (100), which is a typical example of a mechanism subjected to high-frequency shocks. A press used for stamping metal parts would be another example. Although impact tools are the main category of devices on which the present invention can be used, other applications are also possible as apparent to a person skilled in the art, including rotating mechanisms. Moreover, the system (10) can retrofit existing hydraulic circuits or be integrated therewith in newly design circuits.

The rock drill (100) used as the example is an high-power impact tool using hydraulic fluid flowing in the hydraulic circuit through the supply lines (102) between one or more sources, such as pumps (104), and components such as a motor (106) and an actuator (108) connected to a tool head (not shown). There are typically around 2800 strokes per minute of the actuator (108). The hydraulic circuit comprises other components that are well known in the art, such as filters, valves, pressure gages, relief valves, check valves, etc. The conventional accumulator (110) that is directly connected to the supply line (102) may be left in place. The pressure of the hydraulic fluid in the supply line is typically between 2400 and 3000 psi.

The high-frequency shocks are defined as pressure peaks in the form of waves that are transmitted upstream in the hydraulic circuit. Those peaks can reach sometimes as high as 7000 psi in a supply of 2700 psi. Also, the expression "high frequency" does not necessarily mean a high number of hertz and is opposed to "low frequency" that relates to shocks generated occasionally or that are dissipated between two successive strokes so that no recovery or adequate recovery thereof is possible. For instance, the 2800 strokes per minute of the typical rock drill (100) generate shocks at a frequency of about 46,7 Hz, which is an example of a high frequency in the present context.

The system (10) comprises a deviation circuit (12) having an inlet (14) and an outlet (16) which are to be connected to the corresponding supply line (102) by appropriate connectors (18). As shown in FIG. 1 , the system (10) is connected upstream the main check valve of the supply line (102). The inlet (14) and outlet (16) are in spaced relationship on the supply line (102). The inlet (14) is to be connected at a location which is upstream in the supply line (102) compared to the outlet (16) so that the inlet (14) be closer to the actuator (108). The deviation circuit (12) deviates a portion of the shocks.

The hydraulic fluid flows in one direction in the deviation circuit, namely from the inlet (14) to the outlet (16). To do so, a first check valve (20) is mounted on the deviation circuit (12) downstream the inlet (14). Then, an accumulator (22) is connected to the deviation circuit (12) at a location downstream the first check valve (20) to damp the shocks, more particularly to attenuate the pressure peaks and to temporary store the energy. The capacity of the accumulator (22) is proportional to the energy to be stored. Two, three or more accumulators (22) can be used. The accumulators (22) are preferably loaded with a gas, such as nitrogen. One larger accumulator (not shown) could replace two or more smaller accumulators (22).

It has been found that the amount of the hydraulic fluid that enters the deviation circuit (12) is about 50% that of the fluid that flows in and out of the conventional accumulator (110). For instance, a typical fluid displacement in the conventional accumulator (110) of a rock drill is about 25 ml during a shock, the exact value being proportional to the peak pressure of the shock. As a result, 12,5 ml is expected to flow in the deviation circuit (12). If two or more accumulators (22) are used, intermediary check valves (24) are mounted between them so that the hydraulic fluid flows only towards the outlet (16). A final or outlet check valve (26) is mounted on the deviation circuit (12) between the location where the last accumulator (22) is connected and the outlet (16). The final check valve (26) prevents the hydraulic fluid in the supply line (102) from directly reaching the sole or last accumulator (22) through the outlet (16).

A valve (30) is mounted between the inlet (14) and the first check valve (20). The purpose of the valve (30) is to restrict the flow of hydraulic fluid so that the actuator (108) be given priority over the deviation circuit (12). Preferably, the valve (30) is a piloted valve which is set to open at a pressure higher than the supply pressure. The threshold pressure is set so that the shocks be allowed in the deviation circuit (12). Alternatively, the piloted valve (30) can be replaced by a spool valve, a dropping valve or even a small tube or pipe.

The deviation circuit (12) may be in the form of a single block that comprises a plurality of channels in fluid communication with each other. The block has a plurality of bores interposed between adjacent channels to receive the check valves and the accumulator or accumulators (22).

In use, a portion of the hydraulic fluid is deviated from the supply line (102) through the deviation circuit (12). The deviated hydraulic fluid is then passed through the valve (30) and the first check valve (20) mounted on the deviation circuit (12) downstream the valve (30). Shocks are damped in the deviated hydraulic fluid at a location downstream the first check valve (20) using the accumulator (22). If two or more accumulators (22) are used, the deviated hydraulic fluid flows from damping location to another to be damped by those other accumulators (22) and are passed through an intermediary check valve (24) between locations. The deviated hydraulic fluid passes through a final check valve (26) returning into the supply line (102). The result is that the peak pressures of the shocks are trapped in the deviation circuit (12) and the energy of the previous stroke is reinjected into the supply line (102) as positive energy. EXAMPLE

Tests have been conducted under laboratory conditions with a rock drill similar to the one illustrated in FIG. 1. This rock drill was operating at around 2800 strokes per minute and had a hydraulic supply at a pressure of 2750 psi. Three accumulators (22) version "AF 500 bar" by Hydro Rene Leduc™ were used, all loaded at a pressure of about 1100 psi.

Results showed that the energy recovery system reduces the overall vibrations and the highest pressure peaks were lowered from the original 4200 psi level without the system (10), to 3450 psi with the system (10).

The invention is not limited to the described embodiment and encompasses any alternative embodiments within the limits defined by the claims.

Claims

CLAIMS.

1. An energy recovery system (10) for use with the hydraulic fluid supply line (102) of a mechanism (108) subjected to high-frequency shocks, the system (10) being characterized in that it comprises: a deviation circuit (12) having an inlet (14) and an outlet (16) to be connected to the supply line (102), the inlet (14) and the outlet (16) being in spaced relationship and the inlet (14) of the deviation circuit (12) being connected to the supply line (102) at a location upstream with reference to the outlet (16); a valve means (30) mounted on the deviation circuit (12) downstream the inlet (14) for restricting the flow of hydraulic fluid from the supply line (102); a first check valve (20) mounted on the deviation circuit (12) downstream the valve means (30); an accumulator (22) connected to the deviation circuit (12) at a location downstream the first check valve (20); and a second check valve (24) mounted on the deviation circuit (12) between the location where the accumulator (22) is connected and the outlet

(16).

2. An energy recovery system (10) according to claim 1 , characterized in that the accumulator (22) is a gas-loaded accumulator.

3. An energy recovery system (10) according to claim 1 , characterized in that the system (10) further comprises: a second accumulator (22) connected to the deviation circuit (12) at a location which is downstream the second check valve (24); a third check valve (24) mounted on the deviation circuit (12) between the location where the second accumulator (22) is connected and the outlet (16).

4. An energy recovery system (10) according to claim 3, characterized in that the system (10) further comprises: a third accumulator (22) connected to the deviation circuit (12) at a location which is downstream the third check valve (24); and a fourth check valve (26) mounted on the deviation circuit (12) between the location where the third accumulator (22) is connected and the outlet (16).

5. An energy recovery system (10) according to claim 1 , 3 or 4, characterized in that the reciprocating mechanism (108) is an impact tool.

6. An energy recovery system (10) according to claim 5, characterized in that the impact tool is a rock drill (100).

7. An energy recovery system (10) according to claim 1 , 3 or 4, characterized in that the valve means (30) comprises a piloted valve opening when pressure in the fluid supply line (102) is above a supply pressure at which the mechanism (108) operates.

8. An energy recovery system (10) according to claim 3 or 4, characterized in that the accumulators (22) are gas-loaded accumulators.

9. An energy recovery system (10) according to claim 8, characterized in that the accumulators (22) are loaded at a same pressure.

10. A method of recovering energy in the hydraulic fluid supply line (102) of a mechanism (108) subjected to high-frequency shocks, the method being characterized in that it comprises the steps of: deviating a portion of the hydraulic fluid through a deviation circuit (12) having an inlet (14) and an outlet (16) to be connected to the supply line (102), the inlet (14) and the outlet (16) being in spaced relationship and the inlet (14) of the deviation circuit (12) being connected to the supply line (102) at a location upstream with reference to the outlet (16) of the deviation circuit (12); passing the deviated hydraulic fluid through a first check valve (20) mounted on the deviation circuit (12) downstream the inlet (14); damping shocks in the deviated hydraulic fluid at a location downstream the first check valve (20); passing the deviated hydraulic fluid through a second check valve (24) mounted on the deviation circuit (12) between the location where the shocks are damped and the outlet (16); and returning the deviated hydraulic fluid into the supply line (102).

11. A method according to claim 10, characterized in that it further comprises the steps of: damping shocks in the deviated hydraulic fluid at a location downstream the second check valve (24); passing the deviated hydraulic fluid through a third check valve (24) mounted on the deviation circuit (12) between the location downstream the second valve and the outlet (16).

12. A method according to claim 11 , characterized in that it further comprises the steps of: damping shocks in the deviated hydraulic fluid at a location downstream the third check valve (24); passing the deviated hydraulic fluid through a fourth check valve (26) mounted on the deviation circuit (12) between the location downstream the third valve and the outlet (16).

13. A method according to claim 10, 11 or 12, characterized in that it further comprises the step of monitoring the pressure in the fluid supply line (102) controlling the pressure of the deviated hydraulic fluid in the deviation circuit (12).

14. A method according to claim 10, 11 , 12 or 13, characterized in that the mechanism (108) is an impact tool.

15. A method according to claim 14, characterized in that the impact tool is a rock drill (100).