Patent Application
20170113337
This disclosure relates generally to hydraulic hammers, and more specifically to magnetic guide systems used in hydraulic hammers.
Hydraulic hammers are generally known to include a tool extending partially out of a housing. Such hammers may include a hydraulically actuated power cell having an impact system operatively coupled to the tool. The impact system generates repeated, longitudinally directed forces against a proximal end of the tool disposed inside the housing. The distal end of the tool, extending outside of the housing, may be positioned against rock, stone or other materials to break up those materials. During operation, the hydraulic hammer will form large pieces of broken material as well as stone dust and fine grit. The stone dust may include abrasive material, such as quartz, which could increase wear and cause premature failure of components should it migrate along the tool and into the interior of the hydraulic hammer.
Various seal arrangements have been proposed to address the issue of migrating dust. In many of these devices, the seal is positioned centrally within the housing, near the internal components of the power cell. However, other arrangements of seals and sealing strategies have been proposed, which have resulted in various levels of success in isolating the piston and internal workings of the hydraulic hammer from harmful contamination.
However, despite the presence of various seals, bushings and lubrication in a hydraulic hammer, one of the most common, most critical and most expensive failures for a hydraulic hammer is galling of the piston to the cylinder or sleeve in which the piston reciprocates. There are a number of potential causes of galling, ranging from the presence of harmful contaminants to a lack of precise machining of the piston and cylinder elements and poor quality surface finish.
One use of a hydraulic hammer is tunneling where the hydraulic hammer is used in a horizontal position. Horizontal use of a hydraulic hammer tends to cause more wear on the piston and cylinder assembly. Galling and wear would at least be reduced if it were possible to prevent the piston from mechanically touching the cylinder and if it were possible to maintain a selected clearance between them. Further, galling and wear would be reduced if it were possible to reduce the extent and magnitude of radial motion of the piston within the hydraulic hammer.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.
In one aspect, the present disclosure describes a hydraulic hammer with a power cell. A work tool is partially received in and is movable with respect to the power cell. A sleeve is positioned in the power cell that defines a centerline. A piston is concentrically positioned in the sleeve and movable in the sleeve between a first position in contact with the work tool and a second position out of contact with the work tool. A magnetic guide system includes at least one of a first magnetic guide component disposed in the piston and at least one of a second magnetic guide component disposed in the sleeve that interact to produce magnetic repellent forces therebetween to urge the radial position of the piston towards the center line.
In other aspects of the disclosure, the magnetic guide system may include an electrodynamic bearing system. The first magnetic guide component may include a first ring magnet and a second ring magnet disposed in an axially spaced apart configuration in the piston. The second magnetic guide component may include a first conductive cylinder and a second conductive cylinder, the first and second conductive cylinders disposed adjacent respective first and second ring magnets. The piston may have a stroke and the first and second ring magnets may have a first axial length, the first axial length greater than the stroke. The first and second ring magnets may have a first axial length and the first and second conductive cylinders may have a second axial length, the first axial length less than the second axial length. The magnetic guide system may include a magnetic suspension system. The first magnetic guide component of the magnetic suspension system may include a first magnetic ring component and a second magnetic ring component disposed in an axially spaced apart configuration in the piston. The first and second magnetic ring components may be permanent magnets. The first and second magnetic ring components may be diametrically magnetized. The second magnetic guide component of the magnetic suspension system may include an array of electromagnetic elements disposed adjacent the first and second permanent magnets. The hydraulic hammer may further include a power source in operative communication with the array of electromagnetic elements. The magnetic guide system may include a diamagnetic suspension system. The first magnetic guide component of the diamagnetic suspension system may include a first diamagnetic ring and a second diamagnetic ring disposed in an axially spaced apart configuration in the piston. The second magnetic guide component of the diamagnetic suspension system may include a first permanent magnet ring and a second permanent magnet ring, the first and second permanent magnet rings disposed adjacent respective first and second diamagnetic rings.
In yet another aspect of the disclosure, a machine includes an implement system attached to the machine. A hydraulic hammer is attached to the implement system, the hydraulic hammer including a power cell. A work tool is partially received in, and movable with respect to, the power cell. A sleeve is positioned in the power cell and defines a centerline. A piston includes a plurality of hydraulic surfaces. The piston is concentrically positioned in the sleeve and movable in the sleeve between a first position in contact with the work tool and a second position out of contact with the work tool. A magnetic guide system includes at least one of a first magnetic guide component disposed in the piston and at least one of a second magnetic guide component disposed in the sleeve that interact to produce magnetic repellent forces therebetween to urge the radial position of the piston towards the center line.
In other aspects of the disclosure, the magnetic guide system may include one of an electrodynamic bearing system, a magnetic suspension system, and diamagnetic suspension system.
The disclosure provides a method of reducing wear in a hydraulic hammer, including providing a hydraulic hammer with a piston and a sleeve concentrically disposed about the piston. A magnetic guide system is disposed in the hydraulic hammer, wherein the magnetic guide system includes at least one of a first magnetic guide component in the piston and at least one of a second magnetic guide component in the sleeve. A first magnetic guide component and the second magnetic guide component are caused to interact to produce magnetic repellent forces therebetween to urge the radial position of the piston towards a center line of the sleeve. The magnetic guide system may include one of an electrodynamic bearing system, a magnetic suspension system, and diamagnetic suspension system.
Further and alternative aspects and features of the disclosed principles will be appreciated from the following detailed description and the accompanying drawings. As will be appreciated, the principles related to a hydraulic hammer with electrodynamic bearings in disclosed herein are capable of being carried out in other and different embodiments, and capable of being modified in various respects. Accordingly, it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the scope of the appended claims.
This disclosure relates to a hydraulic hammer with a magnetic guide system.
Machine 10 may embody a fixed or mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, machine 10 may be an earth-moving machine such as a backhoe, an excavator, a dozer, a loader, a motor grader, or any other earth-moving machine. Machine 10 may include an implement system 12 configured to move the hydraulic hammer 14, a drive system 16 for propelling machine 10, a power source 18 that provides power to implement system 12 and drive system 16, and an operator station 20 for operator control of at least implement system 12 and drive system 16.
Power source 18 may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine or any other type of combustion engine known in the art. It is contemplated that power source 18 may alternatively embody a non-combustion source of power such as a fuel cell, an electrical or mechanical power storage device, or another source known in the art. Power source 18 may produce a mechanical or electrical power output that may then be converted to hydraulic power for moving implement system 12.
Implement system 12 may include a linkage structure acted on by fluid actuators to move the hydraulic hammer 14. The linkage structure of implement system 12 may be complex, for example, including three or more degrees of freedom. The implement system 12 may carry the hydraulic hammer 14 which has a tool 22 for impacting an object or ground surface 26.
A power cell 40 is disposed inside the housing chamber 32 and includes several internal components of the hydraulic hammer 14. As shown in
A sleeve 72 is disposed within chamber 32 about piston 42 and aligned with longitudinal axis 44. The sleeve 72 has an inner surface 74 facing the piston 42, which is provided with lubricant to lubricate and support the piston as it moves within the sleeve.
A distal portion of the power cell 40 includes the work tool 22 and structure for guiding the work tool 22 during operation. Accordingly, the power cell 40 includes a front head 50 inserted into the lower housing member 36 with wear plates 52 interposed between the front head 50 and the housing 30. A lower bushing 54 is inserted into a distal end of the front head 50 so that a distal end 56 of the lower bushing 54 is positioned adjacent the distal end of the housing 30. The bushing further defines an inner guide surface 58. The work tool 22 includes a proximal section 60 sized to be slidably received within the inner guide surface 58 of the lower bushing 54. The work tool 22 further has a distal section 62, which projects from the lower bushing 54 and housing 30 through the opening 38.
A hydraulic circuit (not shown) provides pressurized fluid to drive the piston 42 toward the work tool 22 during the work stroke and to return the piston 42 during the return stroke. The hydraulic circuit is not described further, since it will be apparent to one skilled in the art that any suitable hydraulic system may be used to provide pressurized fluid to the piston 42, such as the arrangement described in U.S. Pat. No. 5,944,120. Alternatively, a pneumatic or other type of motive power may be used to drive the piston 42.
In operation, near the end of the work stroke, the piston 42 strikes the proximal section 60 of the work tool 22. The distal section of the work tool 22 may include a tip 64 positioned to engage an object or ground surface 26. The impact of the piston 42 on the proximal section 60 drives the tip 64 into the object or ground surface 26, thereby creating pieces of broken material as well as dust, grit, and other debris. The hydraulic hammer 14 may further include a composite seal 70 for preventing dust and other broken material from migrating along the work tool 22 and into the interior components of the power cell 40.
The piston 42 reciprocates within the sleeve 72. When the piston 42 exhibits undesired motion, i.e., radial displacement, the piston can cause damage to the inner surface 74 of the sleeve. One form of damage is galling, which is a form of wear caused by adhesion between sliding surfaces. Galling can occur if the lubrication property of the lubricating oil is compromised by age, for example, or overwhelmed by sudden and/or large forces.
The magnetic guide system 76 of the present embodiment includes elements of an electrodynamic bearing system 78.
The working principles of electrodynamic bearings (EDBs) are generally known in the art. The operation of an electrodynamic bearing is based on the induction of eddy currents in a conductor that moves through a magnetic field. When an electrically conducting material moves through a magnetic field, a current is generated in the material that counters the change in the magnetic field. In other words, the generated current in the object moving through the magnetic field results in a magnetic field created within the moving object that is oriented opposite to the magnetic field that the object is moving through. The electrically conducting material thus acts as a magnetic mirror. EDBs exploit the repulsive mirror forces generated by the eddy currents to achieve the maintenance of spacing between elements. In this case, the relative motion between the conductor and the magnetic field induces eddy currents inside the conductor, thereby generating forces that can be used to maintain a desired or selected spacing. Different configurations relying on the same basic principle are possible and unnecessary eddy current losses can be virtually eliminated.
The illustrated electrodynamic bearing system 78 includes at least one of a first magnetic guide component 79 in the piston 42. The first magnetic guide component 79 may be a pair of spaced axially magnetized ring magnets 80, 82. A first ring magnet 80 is positioned generally proximally (direction P) in the piston 42 and centered about the centerline 44 of the piston. A second ring magnet 82 is positioned generally distally (direction D) in the piston and centered about the centerline of the piston. The orientation of the poles of the ring magnets are the same, e.g., the south poles of both the first and second ring magnet 80, 82 are both provided at the distal ends thereof. The axial length of each of the first and second ring magnets 80, 82 is at least the length of the stroke of the piston 42. The piston 42 may be made of a non-magnetic material. In an alternative embodiment, the ring magnets 80, 82 may be constructed as electromagnets.
The illustrated electrodynamic bearing system 78 includes at least one of a second magnetic guide component 83 in the sleeve 72. The second magnetic guide component 83 may include a first conductive cylinder 84 and a second conductive cylinder 86 surrounding respectively the first and second ring magnets 80, 82. The conductive cylinders 84, 86 are disposed within the sleeve 72 and are also centered about the centerline 44 of the piston 42 such that when the piston is centered about the centerline, the ring magnets 80, 82 are respectively positioned concentrically within cylinders 84, 86 at least when the piston is in the initial or starting position shown in
The axial length of each of the first and second conductive cylinders 84, 86 is greater than the axial length of the first and second ring magnets 80, 82. The conductive cylinders 84, 86 are formed of an electrically conductive material, such as copper. The sleeve 72 is made of a non-magnetic material.
The illustrated example of an electrodynamic bearing system 78 is based on passive magnetic technology. It does not require any control electronics to operate and works because electrical currents generated by relative motion between the piston 42 and sleeve 72 cause a restoring force. In one embodiment of such a system, the natural motion of the piston 42 generates the necessary relative motion to create the restoring force. Another example, (not shown) of an electrodynamic bearing system 78 is based on active magnetic control, the implementation of which is considered within the ability of one skilled in the art to execute.
In a hydraulic hammer 14 with the illustrated electrodynamic bearing system 78 of
In particular, the magnetic guide system 176 includes first and second magnetic ring components 180, 182 in an axially spaced apart configuration and disposed within piston 42. The first and second magnetic ring components 180, 182 may be permanent magnets. The first and second magnetic ring components 180, 182 may be diametrically magnetized. Disposed in the sleeve 72 and generally surrounding the piston 42—in particular the portion of the piston containing the first and second magnetic ring components 180, 182—is an array of electromagnetic elements 184 arranged in a linear fashion or as a series.
In one embodiment, the array of electromagnetic elements 184 may be powered by a power source 200 connected to individual elements of the array. The power source 200 may energize each of the elements 184 of the array such that the magnetic fields generated alternate in adjacent elements. The power source 200 may include amplifiers and control and feedback circuitry as is known and may additionally respond to sensors that measure the distance between the piston 42 and sleeve 72 to maintain a selected gap therebetween.
Alternatively, the magnetic guide system 176 may generate its own electricity. When the piston 42 moves axially within the sleeve 72, the first and second magnetic ring components 180, 182 are also moved relative to the array of electromagnetic elements 184 in the sleeve. The magnetic fields of the first and second magnetic ring components 180, 182 cause a current in the array of electromagnetic elements 184 in the sleeve by inductance. The magnetic field thus generated creates a magnetic suspension force that urges the radial position of the piston towards the centerline 44, i.e., radially away from the electromagnetic elements 184, which extend peripherally around the piston. The implementation of magnetic guide system 176, according to the present disclosure, is considered within the ability of one skilled in the art to execute.
The illustrated diamagnetic suspension system 276 includes at least one of a second magnetic guide component 283 in the sleeve 72. The second magnetic guide component 283 may include a first permanent magnet ring 284 and a second permanent magnet ring 286 surrounding respectively the first and second diamagnetic rings 280, 282. The first and second permanent magnet rings 284, 286 are disposed within the sleeve 72 and are also centered about the centerline 44 of the piston 42 such that when the piston is centered about the centerline, the first and second diamagnetic rings 280, 282 are respectively positioned concentrically within first and second permanent magnet rings 284, 286 at least when the piston is in the initial or starting position shown in
In operation, diamagnetic materials create an induced magnetic field in a direction opposite to an externally applied magnetic field, and are repelled by the applied magnetic field. Thus, in the illustrated embodiment, the first and second diamagnetic rings 280, 282 are repelled by the externally applied magnetic field of the first and second permanent magnet rings 284, 286. In this manner, the piston 42, which contains the first and second diamagnetic rings 280, 282, is urged radially towards the centerline 44 of the power cell 40.
In accordance with the embodiments disclosed herein, galling and wear may be reduced within the hydraulic hammer.
The present disclosure is applicable to any form of hydraulic hammer and to any machine with a moving piston in which forces generated by motion of the piston are significant. In particular, where the motion of a piston exhibits deleterious lateral or radial motion, it would be advantageous to employ a magnetic guide system according to the disclosure. Systems according to embodiments of the disclosure provide a reduction of the deleterious motion and contribute to a reduction or elimination of galling and wear.
Although the disclosed embodiments have been described with reference to a hammer assembly in which the tool is driven by a hydraulically actuated piston, the disclosed embodiments are applicable to any tool assembly having a reciprocating work tool movable within a chamber by suitable drive structure and/or return structure. The disclosed embodiments encompass pneumatic tools and other impact tools.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
