Variable volume accumulator

#This patent disclosure relates generally to accumulators and, more particularly to accumulators having a volume which is variable.

#Hydraulic hammers are used on work sites to break up large hard objects before such objects can be moved away. Hydraulic hammers may be mounted to back hoes or excavators or other machines. Typically, the hammer assembly is powered by either a hydraulic or pneumatic pressure source or a combination of both. With those hammer assemblies powered by a combination of hydraulic and pneumatic pressure, a piston is retracted against a volume of compressible gas by applying a hydraulic fluid pressure to a first shoulder of a piston. As the piston retracts, the volume of gas decreases, increasing its pressure. Once the piston reaches a predetermined position, high pressure hydraulic fluid is applied to a second shoulder of a piston that drives the piston in a downward direction for a work or power stroke. The downward movement of the piston allows the compressed gas to expand, releasing energy which further propels the downward movement of the piston. During the power stroke, the downward moving piston strikes a work tool, which, in turn, is driven in the downward direction. The work tool strikes the object to be broken up.

#Hydraulic hammers may be used to break-up a variety of materials such as rock, concrete, asphalt, or other hard objects. The physical properties of these materials can vary. For example, some materials may be harder than others. Harder materials typically require higher impact energy to fracture. One way to deal with this issue may be to use the hammer for a longer period of time on such materials. Another may be to switch to larger, more powerful hammers when encountering harder materials. However, both of these methods are inefficient and time-consuming. Moreover, while some hydraulic hammers have external, manual adjustments that can be used to shorten the length of the piston stroke, such adjustments do not allow for any increase in impact energy. To the contrary, while shortening the length of the piston stroke increases the frequency of the hammering, it decreases the impact energy produced by each stroke of the piston. Additionally, increasing the charging pressure of the compressible gas chamber in order to increase the impact energy produced by the hammer may undesirably shorten the life of the seals associated with the gas chamber as higher gas pressures are generally harder on the seals.

#FIG. 1 is a schematic side sectional view of a hammer assembly according to the present disclosure.

#FIG. 2 is an enlarged, schematic side sectional view of the hammer assembly of FIG. 1 showing the accumulator assembly with the movable barrier positioned so as to define a relatively larger volume for receiving pressurized gas as compared to the position shown in FIG. 3.

#FIG. 3 is an enlarged, schematic side sectional view of the hammer assembly of FIG. 1 showing the accumulator assembly with the movable barrier positioned so as to define a relatively smaller volume for receiving pressurized gas as compared to the position shown in FIG. 2.

#This disclosure relates to an accumulator assembly having a volume that can be varied in order to adjust the effective volume of a compressed gas system with which the accumulator assembly communicates. With particular reference to FIG. 1 of the drawings, a cross-sectional view of an exemplary hammer assembly 10 is provided. In a known manner, the hammer assembly 10 may be attached to any suitable machine such as an excavator, backhoe loader, skid steer or similar machine. While the accumulator assembly is illustrated and described in connection with a hammer assembly, the accumulator assembly has applicability in various other types of machines as well. For example, the accumulator assembly may be used in any application involving a fluid system that is subject to pressure.

#As shown in FIG. 1, the hammer assembly 10 may include a housing 12 within which a piston 14 may be slidably supported. Additionally, a work tool 16 may be supported in a lower end of the housing 12 with a portion of the work tool 16 extending outward therefrom. The work tool 16 may have any configuration, such as for example a chisel, that would be useful in hammering application. The work tool 16 also may be configured so as to be removable so as to allow a variety of tools with different configurations to be attached to the hammer assembly 10.

#The piston 14 may be supported so as to be movable relative to the housing 12 in a reciprocating manner generally in the direction of arrows 17 and 18 in FIG. 1. More specifically, during an impact or work stroke, the piston 14 moves in the general direction of arrow 17 and near the end of the work stroke comes into contact with the work tool 16 such as shown in FIG. 1. Conversely, during a return stroke, the piston 14 retracts away from contact with the work tool 16 (the position shown in FIG. 1) in the general direction of arrow 18. The reciprocating impacts of the piston 14 on the work tool 16, in turn, drive a corresponding reciprocating movement of the work tool 16. When the piston 14 strikes the work tool 16, the force of the piston 14 is transmitted to the work tool 16 in the general direction of arrow 17. This force may be applied to a hard object such as rock, concrete or asphalt in order to break up the object.