Piston and magnetic bearing for hydraulic hammer

Abstract

A hydraulic hammer includes 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 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.

Claims

1. A hydraulic hammer, comprising: a power cell; a work tool partially received in, and movable with respect to, the power cell; a sleeve positioned in the power cell and defining a centerline; a piston with a plurality of hydraulic surfaces, the piston 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; and a magnetic guide system including 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 centerline, wherein one of the first guide component or the second guide component includes a first ring magnet and a second ring magnet disposed in an axially spaced apart configuration in the piston, one of the first magnetic guide component or the second magnetic guide component includes a first conductive cylinder and a second conductive cylinder, the first and second conductive cylinders disposed adjacent and extending concentrically around respective ones of the first and second ring magnets.

2. The hydraulic hammer of claim 1, wherein the magnetic guide system includes an electrodynamic bearing system.

3. The hydraulic hammer of claim 1, wherein the piston has a stroke and the first and second ring magnets have a first axial length, the first axial length greater than the stroke.

4. The hydraulic hammer of claim 1, wherein the first and second ring magnets have a first axial length and the first and second conductive cylinders have a second axial length, the first axial length less than the second axial length.

5. The hydraulic hammer of claim 1, wherein the magnetic guide system includes a magnetic suspension system.

6. The hydraulic hammer of claim 5, wherein the first magnetic guide component of the magnetic suspension system includes a first magnetic ring component and a second magnetic ring component disposed in an axially spaced apart configuration in the piston.

7. The hydraulic hammer of claim 6, wherein the first and second magnetic ring components are permanent magnets.

8. The hydraulic hammer of claim 7, wherein the first and second magnetic ring components are diametrically magnetized.

9. The hydraulic hammer of claim 7, wherein the second magnetic guide component of the magnetic suspension system includes an array of electromagnetic elements disposed adjacent the first and second permanent magnets.

10. The hydraulic hammer of claim 9, further comprising a power source in operative communication with the array of electromagnetic elements.

11. The hydraulic hammer of claim 1, wherein the piston and sleeve are made of non-magnetic materials.

12. A machine, comprising: an implement system attached to the machine; a hydraulic hammer attached to the implement system, the hydraulic hammer comprising: a power cell; a work tool partially received in, and movable with respect to, the power cell; a sleeve positioned in the power cell and defining a centerline; a piston with a plurality of hydraulic surfaces, the piston 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; and a magnetic guide system including 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, one of the first magnetic guide component and the second magnetic guide component comprising a pair of spaced apart ring magnets, each ring magnet having a first end and a second end, the first and second ends having opposite poles, and an axis extending between the first and second ends, the axis being collinear with the centerline of the sleeve.

13. The hydraulic hammer of claim 12, wherein the magnetic guide system includes one of an electrodynamic bearing system, a magnetic suspension system, and diamagnetic suspension system.

14. The hydraulic hammer of claim 1, wherein the first and second axially spaced apart ring magnets each have a first end and a second end, the first and second ends have opposite poles, and an axis extends between the first and second ends and is collinear with the centerline of the sleeve.

15. A hydraulic hammer, comprising: a power cell; a work tool partially received in, and movable with respect to, the power cell; a sleeve positioned in the power cell and defining a centerline; a piston with a plurality of hydraulic surfaces, the piston 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; and a magnetic guide system including 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 centerline, the magnetic guide system including a diamagnetic suspension system having a diamagnetic ring and a permanent magnet ring, the diamagnetic ring and the permanent magnet ring being disposed concentrically about the centerline, and one of the diamagnetic ring and the permanent magnet ring extending concentrically around another of the diamagnetic ring and the permanent magnet ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagrammatic illustration of a machine having a hydraulic hammer.

(2) FIG. 2 is a side elevation view, in cross-section, of a hydraulic hammer.

(3) FIG. 3 is a partial cross-section view of the hydraulic hammer of FIG. 2 showing an electrodynamic bearing system in a power cell thereof with a piston at a maximum top working position.

(4) FIG. 4 is a partial cross-section view of the hydraulic hammer of FIG. 2 showing an electrodynamic bearing system in a power cell thereof with a piston at a lower working position relative to that illustrated in FIG. 3.

(5) FIG. 5 is a partial cross-section view of the hydraulic hammer of FIG. 2 showing a magnetic suspension system in a power cell thereof.

(6) FIG. 6 is a partial cross-section view of the hydraulic hammer of FIG. 2 showing a diamagnetic suspension system in a power cell thereof.

DETAILED DESCRIPTION

(7) This disclosure relates to a hydraulic hammer with a magnetic guide system. FIG. 1 illustrates an exemplary machine 10 including a hydraulic hammer 14 that employs a magnetic guide system that functions to maintain alignment of a piston of the hydraulic hammer and thereby reduce or eliminate galling and other effects of misalignment and unintended or undesired motion of the piston. It will be understood that magnetic components employed in the various embodiments of the invention may include use of permanent magnets, electromagnets, ferromagnetism, diamagnetism, superconducting magnets and magnetism due to induced currents in conductors and suitable combinations thereof.

(8) 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.

(9) 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.

(10) 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.

(11) FIG. 2 is a cross-sectional view of the hydraulic hammer 14 of FIG. 1. The hydraulic hammer 14 includes a housing 30 defining a chamber 32. The housing 30 may include an upper housing member 34 and a lower housing member 36 that are welded or otherwise joined together. The upper and lower housing members 34, 36 define upper and lower chambers, respectively, and together make up the chamber 32. A distal end of the housing 30 (i.e., the lower housing member 36) defines an opening 38.

(12) A power cell 40 is disposed inside the housing chamber 32 and includes several internal components of the hydraulic hammer 14. As shown in FIG. 2, a proximal portion of the power cell 40 provides an impact assembly that includes a piston 42. The piston 42 is operatively housed in the chamber 32 such that the piston 42 can translate along a centerline or longitudinal axis 44, which will also be referred to as the centerline, in the general direction of arrows 46 and 48. In particular, during a work stroke, the piston 42 moves in the general direction of arrow 46, while during a return stroke the piston 42 moves in the general direction of arrow 48.

(13) 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.

(14) 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.

(15) 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.

(16) 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.

(17) 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.

(18) FIGS. 3 and 4 show a magnetic guide system 76 that provides a restoring force to a radially displaced piston 42 in a first embodiment of a hydraulic hammer 14. The hydraulic hammer 14 of FIG. 4 is in a first position in contact with the work tool and the hydraulic hammer of FIG. 3 is in a second position out of contact with the work tool.

(19) The magnetic guide system 76 of the present embodiment includes elements of an electrodynamic bearing system 78. FIG. 3 illustrates a hydraulic hammer in an initial or starting position or state wherein the piston 42 is positioned proximally and FIG. 4 illustrates an extended position of the piston moved distally relative to the starting position.

(20) 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.

(21) 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.

(22) 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 FIG. 3.

(23) 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.

(24) 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.

(25) In a hydraulic hammer 14 with the illustrated electrodynamic bearing system 78 of FIGS. 3 and 4, when the piston 42 is displaced from the centerline 44 in operation of the hydraulic hammer, the interaction of fields generated by the first and second ring magnets 80, 82 and the first and second conductive cylinder 84, 86 causes the generation of repositioning forces to re-center the piston in the sleeve 72. The repositioning forces are repulsive and greatest in the vicinity between the piston 42 and sleeve 72 where the gap therebetween is the narrowest in a displaced system. The repositioning forces are attractive but lesser in the vicinity between the piston 42 and sleeve 72 where the gap therebetween is the greatest in a displaced system.

(26) FIG. 5 illustrates a further embodiment of a magnetic guide system 176 according to the disclosure. The hydraulic hammer 14 is shown with a magnetic guide system 176 including a magnetic suspension system 188 provided in power cell 40. The magnetic suspension system 188 is disposed in a hydraulic hammer 14 that is similar to that described above and generates a similar repositioning effect as the electrodynamic bearing system 78 of the system disclosed in FIGS. 3 and 4.

(27) 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 42in particular the portion of the piston containing the first and second magnetic ring components 180, 182is an array of electromagnetic elements 184 arranged in a linear fashion or as a series.

(28) 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.

(29) 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.

(30) FIG. 6 illustrates a magnetic guide system 267 comprising a diamagnetic suspension system 276. The diamagnetic suspension system 276 includes at least one of a first magnetic guide component 279 in the piston 42. The first magnetic guide component 279 may be a pair of spaced diamagnetic rings 280, 282. The pair of spaced diamagnetic rings 280, 282 may be solid or hollow cylinders. A first diamagnetic ring 280 is positioned generally proximally (direction P) in the piston 42 and centered about the centerline 44 of the piston and a second diamagnetic ring 282 is positioned generally distally (direction D) in the piston and centered about the centerline of the piston. The first and second diamagnetic rings 280, 282 may be made of any suitable diamagnetic material such as pyrolytic graphite, bismuth and the like.

(31) 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 FIG. 3. Additional magnetic rings may be disposed along the length of the cylinder. The axial length of each of the first and second permanent magnet rings 284, 286 is greater than the axial length of the first and second diamagnetic rings 280, 282. The axial length of the first and second diamagnetic rings 280, 282 is at least equal to the axial stroke of the piston 42.

(32) 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.

(33) In accordance with the embodiments disclosed herein, galling and wear may be reduced within the hydraulic hammer.

INDUSTRIAL APPLICABILITY

(34) 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.

(35) 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.

(36) 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.

(37) 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.

(38) 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.