[Not Applicable]
[Not Applicable]
The present invention relates to hydraulic systems, and in particular to hydraulic systems used on refuse collection vehicles to compact refuse and operate auxiliary hydraulic equipment such as refuse cart lifting devices.
Refuse collection vehicle hydraulic systems are primarily used to operate a ram that drives a packer panel, which compacts refuse dumped into the refuse collection vehicle's hopper. Many refuse collection vehicles are often also equipped with hydraulically operated auxiliary equipment such as refuse cart lifters. Refuse cart lifters are commonly known as lifters or tippers because they assist the vehicle operator in lifting and tipping heavy refuse carts into the refuse collection vehicle hopper or intermediate container.
A flow diverting apparatus, is commonly used to divert hydraulic fluid flow out of the main hydraulic system into the lifter circuit that operates these refuse cart lifting devices. The use of a flow-diverting apparatus, such as a diverter control assembly, to control hydraulic fluid flow to auxiliary hydraulic circuits is well known to those familiar with the design and operation of hydraulic systems.
Flow can be diverted by numerous means. The simplest method involves nothing more than a tee fitting placed in line of one of the pressure lines, with the primary flow directed towards the packer panel ram and the tee flow being directed to the lifter circuit. There are, however, several problems associated with this type of simple system. For example, the simple tee system will not maintain a consistent flow to the refuse cart lifters. The flow to the refuse cart lifters will be proportional to the flow to the downstream functions (such as the refuse collection vehicle packer ram) based on the size of the hydraulic lines and the downstream back pressure.
As inlet flow increases, the outlet flows increase and remain proportional to each other. This is because mobile refuse collection equipment typically utilizes a positive displacement “power take off” pump to provide refuse collection vehicle hydraulic system flow and pressure. The amount of hydraulic fluid flow in the system varies with the speed of the pump, and the pump speed directly corresponds to the refuse collection vehicle engine speed. Thus, the simple tee system cannot control the amount of hydraulic fluid flow to the refuse cart lifters as pump speeds vary.
Hydraulic refuse cart lifters require more precise control of hydraulic fluid flow. The time of the refuse cart lifter operating cycle is critical to performance, life of the refuse cart lifter, and life of the refuse cart. Most refuse cart lifters require a flow of 2 to 2.5 gallons per minute (gpm). The simple tee system can be improved by placing an orifice in the outlet line to the refuse cart lifters. This will change the proportion of flow and restrict the flow to a more suitable level.
For example, diverter control assemblies may use a priority flow valve containing an orifice. However, the pressure required to operate the priority flow valve is high, causing a pressure drop across the block. In order to maintain a controlled flow to two refuse cart lifters, a flow divider valve may be used to evenly divide the flow provided by the priority flow valve. However, when the refuse cart lifter bottoms out or the flow divider valve fails, the priority flow valve will shut down flow to downstream functions.
Moreover, this configuration can require significantly more pressure to operate than the priority flow valve. In fact, the pressure drop is more than doubled in the dual refuse cart lifter configuration. The combination of the two devices causes the pressure drop in the valve to be very high (as high as 350 to 400 psi, or more in certain instances). However, all mobile refuse equipment is not the same. System flow rates can range from less than 20 gpm to more than 60 gpm. The simple tee system is therefore often equipped with an adjustable orifice so that the flow can be fine tuned to make the flow to the refuse cart lifters acceptable regardless of the flow coming in to the tee. This relatively inexpensive type of flow diverter technology is currently used in many systems, but presents many disadvantages when used to control flow to refuse cart lifters.
For example, once the flow to the refuse cart lifters is adjusted, it will still allow for the flow to vary with the primary system flow. This will cause the refuse cart lifters to operate at different speeds relative to the primary system flow. Moreover, the use of a variable orifice results in a significant pressure drop across the system. This causes a reduction in the pressure available to downstream operations and can noticeably affect their operation and performance.
Furthermore, the additional work being done to move the oil through this restriction is dissipated through heat. The addition of heat to the hydraulic system is generally unacceptable as it also reduces the performance of the system. It can also be dangerous and lead to potential component failures and possibly system fires. Finally, if the adjustable orifice is improperly adjusted, it may allow the refuse cart lifters to cycle too quickly and lead to premature lifter failure and cart damage, or even personal injury.
The present priority hydraulic flow diverter control assembly eliminates many disadvantages of existing mobile refuse hydraulic flow control systems and gives flow priority to the auxiliary hydraulic circuit, regardless of the incoming flow. The present priority hydraulic flow diverter control assembly may provide precise flow regardless of the primary hydraulic system flow so that the refuse cart lifter and the refuse cart may operate properly and efficiently.
The present priority hydraulic flow diverter control assembly uses a differential pressure sensing valve and flow regulating valves to provide a precision flow. The flow regulating valves employ an orifice to meter hydraulic fluid flow to the refuse cart lifters. The differential pressure sensing valve may reduce the pressure differential across the flow regulating valve, but may also maintain the pressure differential required to allow the flow regulating valves to operate properly.
The failure mode of the differential pressure sensing valve and flow regulating valves may also be such that the valve can not block the downstream flow in any way. A relief valve may be used to ensure that the unit is compatible with other manufacturer's products.
A control orifice in the priority flow hydraulic diverter control assembly may stabilize the differential pressure sensing valve to keep it from modulating erratically which reduces vibrations and noise. The control orifice may compensate for flow variations due to pump characteristics in individual applications.
A pressure sequence valve may enable the system to operate in the most efficient manner with respect to pressure drop and flow loss. The pressure sequence valve may divert the hydraulic fluid into a line downstream of the refuse cart lifters when the downstream back pressure is low. This allows the hydraulically operated equipment in the refuse collection vehicle hydraulic system to operate at their intended speed. When the back pressure climbs to a predetermined set point, the pressure sequence valve may sense the increased back pressure and diverts the flow leaving the refuse cart lifters to the hydraulic system reservoir or tank. This may result in a significantly reduced pressure drop across the priority flow hydraulic diverter control assembly.
The design of the present priority flow hydraulic diverter control assembly may prevent variation of the hydraulic fluid flow in the refuse cart lifter hydraulic circuit as the pressure varies in the main refuse collection vehicle hydraulic system or packer ram hydraulic circuit. Thus, the refuse cart lifters may operate at a consistent speed relative to the primary system flow. This may prevent excessively fast cycle times that may cause personal injury, and prolongs the life of the refuse cart lifter and the refuse carts. The significant reduction in the pressure drop across the priority flow hydraulic diverter control assembly greatly reduces the work required to move hydraulic fluid through the orifice in the flow regulating valve that can lead to potential component failures and possibly system fires.
Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on or with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations. Other objects, features and aspects of the present invention are disclosed in or are apparent from the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.
Referring to
Turning to
If priority flow hydraulic diverter control assembly 100 is configured for a second refuse cart lifter 30, hydraulic fluid may also flow out of priority flow hydraulic diverter control assembly 100 to refuse cart lifter 30 through threaded port 175 (shown plugged in
Hydraulic fluid exits priority flow hydraulic diverter control assembly 100 into the main hydraulic system through threaded outlet port 185. Threaded outlet port 190 (plugged in
Priority flow hydraulic diverter control assembly 100 components include a differential pressure sensing valve 110, and a first flow regulating valve 120. Both differential pressure sensing valve 110 and first flow regulating valve 120 are threaded into priority flow hydraulic diverter control assembly 100. First flow regulating valve 120 contains an orifice sized to assist in maintaining the desired flow rate to refuse cart lifter 20. Refuse cart lifters typically require a flow rate of 2.0 to 2.5 gpm. A threaded port 125 for a second flow regulating valve 127 (see
Differential pressure sensing valve 110 is a spring-loaded valve designed to establish flow through flow regulating valve 120 at low hydraulic pressures, and open a path around flow regulating valve 120 at high hydraulic pressures. Thus, differential pressure sensing valve 110 establishes the necessary pressure drop that is required to allow flow regulating valve 120 to operate properly, without generating an excessively high differential pressure across flow regulating valve 120. Using differential pressure sensing valve 110, the pressure drop across flow regulating valve 120 can be reduced to as low as 120 pounds per square inch (psi) in any configuration.
Threaded fitting 145 secures control orifice 147 in priority flow hydraulic diverter control assembly 100 (
Control orifice 147 may also be machined into priority flow hydraulic diverter control assembly 100 (not shown) and may prevent erratic modulation in most applications. In some cases, however, a particular hydraulic system may require a different size orifice to correct the unique modulation of the system. Thus, a single control orifice that is adjustable in size (not shown) may be used to try to match the characteristics of each individual truck hydraulic system. Preferably, however, a non-adjustable control orifice 147 that can be swapped out for a different sized non-adjustable control orifice 147 is preferred.
Priority flow hydraulic diverter control assembly 100 also includes an adjustable, spring-loaded relief valve 130 that is designed to relieve hydraulic pressure within priority flow hydraulic diverter control assembly 100 when a particular hydraulic pressure is reached. Hydraulic pressure within priority flow hydraulic diverter control assembly 100 may rise dramatically for several reasons. For example, hydraulic pressure within priority flow hydraulic diverter control assembly 100 will greatly increase when flow through priority flow hydraulic diverter control assembly 100 is blocked. This can occur when the operator of refuse cart lifter 20 “bottoms out” hand valve 40 (
Hydraulic pressure within priority flow hydraulic diverter control assembly 100 will also greatly increase if refuse cart lifter 20 is attempting to lift a particularly heavy refuse cart. Moreover, the attempted lifting of such a heavy refuse cart may damage the refuse cart. Thus, relief valve 130 is typically adjusted to relieve hydraulic pressure within priority flow hydraulic diverter control assembly 100 that occurs when refuse cart lifter 20 attempts to lift a refuse cart weighing 350 lbs or greater.
Pressure sequence valve 140 and relief valve 130 are preferably manufactured using different thread sizes to prevent the accidental switching of pressure sequence valve 140 and relief valve 130 during assembly of priority flow hydraulic diverter control assembly 100. Incorrect assembly could ultimately cause equipment damage or personal injury.
Pressure sequence valve 140 enables the system to operate in the most efficient manner with respect to pressure drop and flow loss. Pressure sequence valve 140 senses the pressure from the main hydraulic system within priority flow hydraulic diverter control assembly 100 near outlet port 185. Pressure sequence valve 140 recycles hydraulic fluid from refuse cart lifter 20 back to the main hydraulic system for use in driving the refuse collection vehicle packer ram, or other hydraulic equipment, when the pressure sensed in the main hydraulic system is low enough to permit the desired hydraulic fluid flow through refuse cart lifter 20.
At a predetermined set point (typically where the pressure in the main hydraulic system is too high to permit enough hydraulic fluid flow through refuse cart lifter 20 to maintain normal lifter speed), pressure sequence valve 140 directs the fluid flow from refuse cart lifter 20 through outlet port 190 to the hydraulic system tank 192. Thus, proper lifter speed may be maintained both above and below the predetermined set point. Packer ram operation is not significantly affected at this point because the hydraulic fluid flow required by the packer ram is typically low when the main hydraulic system pressure is high. The predetermined set point of pressure sequence valve 140 will vary by individual system, but many systems operate at a predetermined set point of around 1300 psi.
In the preferred embodiment, a spring force in pressure sequence valve 140 mechanically opposes the hydraulic force exerted by the hydraulic pressure from the main hydraulic system (see
A check valve 195 is threaded into priority flow hydraulic diverter control assembly 100. Check valve 195 prevents back flow from the main hydraulic system into priority flow hydraulic diverter control assembly 100 through outlet port 185.
A threaded port 150 (shown in
Dual sequence valve 152 is needed in the dual lifter configuration because if first refuse cart lifter 20 is building more pressure than the second refuse cart lifter 30, e.g. because first refuse cart lifter 20 is lifting a heavier refuse cart than second refuse cart lifter 30, second refuse cart lifter 30 may not receive sufficient flow to operate properly. To correct this situation, dual sequence valve 152 directs hydraulic fluid flow from downstream of first flow regulating valve 120 to provide hydraulic feedback to differential pressure sensing valve 110 and raise the hydraulic pressure upstream of flow regulating valves 120 and 127. This helps to maintain the operability of both refuse cart lifters 20 and 30 despite the increased pressure build up associated with first refuse cart lifter 20.
Hydraulic fluid flow from first refuse cart lifter 20 returns to first hand valve 40 through line 47 if first refuse cart lifter 20 is being raised, or line 45 if first refuse cart lifter 20 is being lowered. Hydraulic fluid returned to first hand valve 40 flows back to priority flow hydraulic diverter control assembly 100 through line 43. Hydraulic fluid from priority flow hydraulic diverter control assembly 100 returns to either the main hydraulic system through line 187 or the hydraulic system tank 192. The flow path from priority flow hydraulic diverter control assembly 100 depends upon the position of pressure sequence valve 140.
Turning to
The refuse collection vehicle hydraulic system pump (not shown) pumps hydraulic fluid through supply line 182 and into priority flow hydraulic diverter control assembly 100 at threaded connection 180. Flow is then directed into first flow regulating valve 120. A portion of the flow out of flow regulating valve 120 is metered by control orifice 147 to differential pressure sensing valve 110. If the hydraulic pressure in line 182 is high enough to overcome the spring force of differential pressure sensing valve 110 and the force applied to differential pressure sensing valve 110 by pressure downstream of control orifice 147, a portion of the flow from line 182 will flow through differential pressure sensing valve 110 to main hydraulic supply line 187. This keeps the differential pressure across priority flow hydraulic diverter control assembly 100 low, but adequate for refuse cart lifter operation.
Hydraulic fluid exits priority flow hydraulic diverter control assembly 100 at threaded port 160 and flows towards first hand valve 40. If the hydraulic pressure downstream of flow regulating valve 120 is high enough to overcome the spring force of relief valve 130 or hand valve relief valve 41, i.e. meets or exceeds the set point of relief valves 130 or 41, hydraulic fluid will flow either back to the main hydraulic system through port 185 or to the hydraulic system tank 192 through port 190. The flow path taken by the hydraulic fluid from the outlet of relief valve 130 is dependent on the set point of pressure sequence valve 140 and the hydraulic pressure in line 187. If the hydraulic pressure in line 187 is high enough to overcome the spring force of pressure sequence valve 140, i.e. meets or exceeds the predetermined set point of pressure sequence valve 140, hydraulic fluid will flow to the hydraulic system tank 192 through port 190. If the hydraulic pressure in line 187 is not high enough to overcome the spring force of pressure sequence valve 140, i.e. is below the predetermined set point of pressure sequence valve 140, hydraulic fluid will flow to the main hydraulic system through port 185.
If the hydraulic pressure downstream of flow regulating valve 120 does not actuate relief valve 130 or hand valve relief valve 41, hydraulic fluid flow may continue to first refuse cart lifter 20 through line 45 if the hand valve is positioned to raise the lifter, or line 47 if the hand valve is positioned to lower the lifter. Hydraulic fluid flow from first refuse cart lifter 20 returns to first hand valve 40 through line 47 if the operator raises the lifter, or line 45 if the operator lowers the lifter. Hydraulic fluid returned to first hand valve 40 flows back to priority flow hydraulic diverter control assembly 100 through line 43. Hydraulic fluid from priority flow hydraulic diverter control assembly 100 returns to either the main hydraulic system through line 187 or the hydraulic system tank 192, again dependent on the set point of pressure sequence valve 140 and the hydraulic pressure in line 187. Check valve 195 prevents backflow from main hydraulic system line 187 into priority flow hydraulic diverter control assembly 100.
Hydraulic fluid flow from first refuse cart lifter 20 returns to first hand valve 40 through line 47 if the operator raises the lifter, or line 45 if the operator lowers the lifter. Hydraulic fluid returned to first hand valve 40 flows back to priority flow hydraulic diverter control assembly 100 through line 43. Hydraulic fluid flow from second refuse cart lifter 30 returns to second hand valve 50 through line 57 if the operator raises refuse cart lifter 30, or line 55 if the operator lowers refuse cart lifter 30. Hydraulic fluid returned to second hand valve 50 flows back to priority flow hydraulic diverter control assembly 100 through line 53.
Again, priority flow hydraulic diverter control assembly 100 returns the hydraulic fluid flowing from refuse cart lifters 20 and 30 to either the main hydraulic system through line 187 or the hydraulic system tank 192. The flow path from priority flow hydraulic diverter control assembly 100 depends upon the position of pressure sequence valve 140.
If the hydraulic pressure in line 182 is high enough to overcome the spring force of differential pressure sensing valve 110 and the force applied to differential pressure sensing valve 110 by pressure downstream of control orifice 147, a portion of the flow from line 182 will flow through differential pressure sensing valve 110 to main hydraulic supply line 187. This keeps the differential pressure across flow regulating valves 120 and 127 low, but adequate for normal operation of both first refuse cart lifter 20 and second refuse cart lifter 30.
Hydraulic fluid from first flow regulating valve 120 exits priority flow hydraulic diverter control assembly 100 at threaded port 160 and may flow via line 42 towards first hand valve 40. Similarly, hydraulic fluid from second flow regulating valve 127 exits priority flow hydraulic diverter control assembly 100 at threaded port 165 may flow via line 52 towards second hand valve 50. If the hydraulic pressure immediately downstream of flow regulating valves 120 or 127 is high enough to overcome the spring force of relief valve 130 or hand valve relief valves 41 and 51, i.e. meets or exceeds the set point of relief valves 130, 41, or 51, hydraulic fluid from one or both of flow regulating valves 120 and 127 will flow either back to the main hydraulic system through port 185 or to the hydraulic system tank 192 through port 190. The flow path taken by the hydraulic fluid from the outlet of relief valves 130, 41 and 51 is dependent on the predetermined set point of pressure sequence valve 140 and the hydraulic pressure in line 187.
Similar to the single lifter configuration of priority flow hydraulic diverter control assembly 100, if the hydraulic pressure in line 187 is high enough to overcome the spring force of pressure sequence valve 140, i.e. meets or exceeds the predetermined set point of pressure sequence valve 140, hydraulic fluid exiting priority flow hydraulic diverter control assembly 100 will flow to the hydraulic system tank 192 through port 190. If the hydraulic pressure in line 187 is not high enough to overcome the spring force of pressure sequence valve 140, i.e. is below the predetermined set point of pressure sequence valve 140, hydraulic fluid will flow to the main hydraulic system through port 185.
If the hydraulic pressure downstream of flow regulating valves 120 and 127 does not actuate relief valves 130, 41, or 51, hydraulic fluid flow may continue to first refuse cart lifter 20 through line 45 if first hand valve 40 is positioned to raise first refuse cart lifter 20, or line 47 if first hand valve 40 is positioned to lower first refuse cart lifter 20. Similarly, hydraulic fluid flow may continue to second refuse cart lifter 30 through line 55 if second hand valve 50 is positioned to raise second refuse cart lifter 30, or line 47 if second hand valve 50 is positioned to lower second refuse cart lifter 30. Hydraulic fluid flow from first refuse cart lifter 20 returns to first hand valve 40 through line 47 if the operator raises the lifter, or line 45 if the operator lowers the lifter.
Hydraulic fluid returned to first hand valve 40 flows back to priority flow hydraulic diverter control assembly 100 through line 43. Similarly, hydraulic fluid returned to second hand valve 50 flows back to priority flow hydraulic diverter control assembly 100 through line 53. Hydraulic fluid from priority flow hydraulic diverter control assembly 100 returns to either the main hydraulic system through line 187 or the hydraulic system tank 192, again dependent on the set point of pressure sequence valve 140 and the hydraulic pressure in line 187. Check valve 195 prevents backflow from main hydraulic system line 187 into priority flow hydraulic diverter control assembly 100.
Although the present priority flow hydraulic diverter control assembly 100 has been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of the present priority flow hydraulic diverter control assembly may be interchanged both in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.
This application makes reference to, claims priority to, and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/650,021, entitled “Priority Hydraulic Flow Diverter Valve”, filed Feb. 4, 2005, the complete subject matter of which is hereby incorporated herein by reference in its entirety.
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