WO2011129702A1 - Arrangement and method for protection, mounting and retention of magnetic pole - Google Patents

Arrangement and method for protection, mounting and retention of magnetic pole Download PDF

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Publication number
WO2011129702A1
WO2011129702A1 PCT/NO2011/000121 NO2011000121W WO2011129702A1 WO 2011129702 A1 WO2011129702 A1 WO 2011129702A1 NO 2011000121 W NO2011000121 W NO 2011000121W WO 2011129702 A1 WO2011129702 A1 WO 2011129702A1
Authority
WO
WIPO (PCT)
Prior art keywords
base plate
permanent magnet
protective casing
polar element
permanent magnets
Prior art date
Application number
PCT/NO2011/000121
Other languages
French (fr)
Inventor
Stev Erlend Skaar
Stig Ove Stornes
Original Assignee
Smartmotor As
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Smartmotor As filed Critical Smartmotor As
Publication of WO2011129702A1 publication Critical patent/WO2011129702A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
    • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
    • H02K15/03—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies having permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H01F7/0221—Mounting means for PM, supporting, coating, encapsulating PM
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets

Definitions

  • the present invention relates to a permanent magnet polar element for arrangement onto a rotor yoke of an electrical machine according to the preamble of claim 1.
  • the invention also relates to a method for providing a hermetically sealed permanent magnet polar element according to the preamble of claim 12 and 13.
  • Permanent magnets are used to an increasing extent in large electrical machines. There are three general problems with the use of permanent magnets as poles of large electric machines:
  • the machines are often used in harsh environments like, for example, saline environment. Therefore, the permanent magnet elements should be protected against corrosion as efficiently as possible. Corrosion protection is often provided by coating and/or encasing against outside air. Surface protection of magnets is expensive and due to new technologies it is not proven over a long lifetime, so using protective casing looks like a viable alternative.
  • the magnet element should hold both tangential and radial mechanical stress in radial-flux machines (tangential and axial stress in axial flux machines), which is why the magnets should be locked, in addition to the magnetic grip, in place as reliably as possible, mechanically and/or by gluing.
  • the permanent magnets are quite sensitive to mechanical interventions and brittle so drilling them for fixing them to by bolting may result in loss of magnetic properties and even damage.
  • the polar elements usually consist of one or several stacked permanent magnets fixed to a base plate and covered with some sort of protective casing around.
  • the base plate has arrangements for fixing the polar element to the rotor yoke.
  • the magnets in the polar element may be magnetized after they are assembled with the base plate and casing, so the process of assembly of the polar element happens with non-magnetized magnets.
  • the polar element concept solves all the above problems providing convenient mounting and dismantling of magnetic poles as well as protection and retention of the magnets.
  • the advantage of the solution with polar elements is to perform machining, gluing and welding (if required) on a demagnetized system.
  • the objective of the invention is to provide a permanent magnet polar element which is free from the drawbacks referred to above, namely from using the unreliable mechanical joint, having holes in casing and/or base plate and using filler mass.
  • the objective of the invention is to provide a permanent magnet polar element in which complete sealing is achieved by relatively simple measures and at the same time providing more reliable and long-term operation of the arrangement.
  • a permanent magnet polar element according to the invention is described in claim 1. Details and preferred features of the permanent magnet polar element are described in claim 2-11.
  • a method for providing a permanent magnet polar element according to the invention is described in claim 12 and 13. Details and preferred features of the method are described in claim 14.
  • a joint between a base plate and a protective casing is made by welding.
  • through holes are made neither in the casing nor in the base plate.
  • No filling mass is to be used under the protective casing.
  • protective casing is manufactured with small tolerances and follows the shape of the permanent magnets in a stack.
  • the base plate To prevent corrosion in the joint between the base plate and the casing, they are made of the same material or of compatible materials.
  • the base plate must have high magnetic permeability for conducting magnetic flux it can be made of soft iron.
  • the protective casing may be made of soft iron as well.
  • the base plate has arrangements for fastening to a rotor yoke. It can be for example screwing or bolting.
  • the magnets can be magnetized after the assembly is totally sealed. This way there would be no concerns on the heat developed during welding destroying the magnets.
  • a method according to the present invention can be summarized as follows:
  • the method further includes that the permanent magnets are arranged to the base plate by means of e.g. gluing.
  • the magnets can alternatively be magnetized before the arrangement.
  • Figure 1 shows an exploded view of a polar element or part of a polar element and shows details of this
  • Figure 2 shows a part (section) of a rotor yoke with magnet poles, where each pole consists of many small permanent magnets
  • Figure 3 shows details of permanent magnets with and without a protective casing.
  • FIG. 1 shows details of a permanent magnet polar element 11 according to the invention for arrangement to a rotor yoke 12 (shown in Figure 2 and 3) of an electrical machine.
  • a permanent magnet polar element 11 according to the invention includes one or more permanent magnets 13, which one or more magnets 13 are arranged to one or more base plates 14 by suitable means, such as by gluing.
  • the permanent magnet polar element 11 further includes one or more protective casings 15.
  • FIG. 2 shows a part 16 (section) of a rotor yoke 12 of an electrical machine, with magnet poles 17.
  • the base plate(s) 14 and protective casing(s) 15 are not shown in this Figure.
  • One pole 17 of the machine may consist of several polar elements 11 or of only one polar element 11. The size and number of polar elements 11 is chosen from production and mounting point of view.
  • each pole 17 consisting of a stack of small permanent magnets 13.
  • the poles 17 preferably have alternating polarity, i.e. North (N) and South (S).
  • FIG. 3 shows polar elements 11 arranged to the rotor yoke 12, both with the protective casing 15 and without the protective casing 15.
  • the base plate 14 is provided with means 18, such as protruding elements provided with through holes for connection screws for fastening of the base plate 14 to the rotor yoke 12 of the electrical machine.
  • the protective casing 15 preferably extends so that it surrounds the permanent magnets 13 from all sides except bottom side, and also surrounds the base plate 14.
  • the protective casing 15 is arranged to the base plate 14 by means of a welded joint 19, as shown in Figure 1. This ensures a complete sealing of the permanent magnets 13.
  • neither the base plate 14 nor casing 15 has through holes which fall inside the casing 15 after assembling the casing 15 to the base plate 14 by means of the welded joint 19.
  • the permanent magnet(s) 13 is/are preferably arranged to the base plate 14 prior to the protective casing 15 and base plate 14 are welded together, ensuring that the permanent magnet(s) 13 are hermetically sealed between the protective casing 15 and the base plate 14. By doing it like this no filling mass, for example epoxy or resin, or other filler elements is used to fill the space between the permanent magnets 13 and the casing 15 for sealing the permanent magnets 13.
  • no filling mass for example epoxy or resin, or other filler elements is used to fill the space between the permanent magnets 13 and the casing 15 for sealing the permanent magnets 13.
  • the protective casing 15 can further be sectionalized to form one whole protective cover 15 covering the polar element 11.
  • the protective casing 15 further preferably has a shape which follows the shape the permanent magnet(s) 13 arranged to the base plate 14 under the protective casing 15, so that the space needed between the permanent magnet(s) 13 and the protective casing 15 is minimized.
  • Both the base plate 14 and the protective casing 15 are preferably made of the same material or the materials which are compatible so that no corrosion occurs at the welded joint 19. Suitable materials for the base plate 14 and the protective casing 15 are soft-magnetic steel or black iron.
  • the permanent magnet(s) 13 can be arranged like un-magnetized permanent magnet(s) 13, and the permanent magnet(s) 13 is/are magnetized after the base plate 14 and the protective casing 15 are welded together ensuring that heat developed during the welding process will not destroy the permanent magnet(s) 13.
  • the permanent magnet(s) 13 can alternatively be magnetized before arranging to the base plate 14.
  • galvanization of polar elements prior to magnetization and galvanization of remaining yoke parts can be done.
  • Other alternatives could be hot spraying of protective metal, metallization of the polar elements and rotor yoke, or painting the protective metal.
  • the permanent magnets can be arranged to the base plate by means of magnetic force.

Abstract

The invention relates to protection, mounting and retention of magnetic poles consisting of permanent magnets in large electrical machines. Each pole consists of one or more permanent magnet polar elements. The polar element intended to be mounted onto the rotor yoke of an electrical machine, consists of at least one permanent magnet, protective casing, surrounding the magnet from all sides except bottom side, and base plate, on which said at least one magnet is fastened, for fixing the polar element to the rotor yoke. Both the base plate and the protective casing are made of the same material or the materials which are compatible so that no corrosion happens at the joint. The base plate and the protective casing are welded together.

Description

Arrangement and method for protection, mounting and retention of magnetic pole
The present invention relates to a permanent magnet polar element for arrangement onto a rotor yoke of an electrical machine according to the preamble of claim 1.
The invention also relates to a method for providing a hermetically sealed permanent magnet polar element according to the preamble of claim 12 and 13.
Background
Permanent magnets are used to an increasing extent in large electrical machines. There are three general problems with the use of permanent magnets as poles of large electric machines:
- protection of permanent magnets,
- mounting and dismantling of large magnetic poles onto/from the rotor yoke, and
- retention of the magnetic poles.
The machines are often used in harsh environments like, for example, saline environment. Therefore, the permanent magnet elements should be protected against corrosion as efficiently as possible. Corrosion protection is often provided by coating and/or encasing against outside air. Surface protection of magnets is expensive and due to new technologies it is not proven over a long lifetime, so using protective casing looks like a viable alternative.
Mounting the large poles consisting of magnetized permanent magnets onto the surface of the rotor is difficult. Also removing the magnet pieces glued to the rotor is problematic.
The magnet element should hold both tangential and radial mechanical stress in radial-flux machines (tangential and axial stress in axial flux machines), which is why the magnets should be locked, in addition to the magnetic grip, in place as reliably as possible, mechanically and/or by gluing. The permanent magnets are quite sensitive to mechanical interventions and brittle so drilling them for fixing them to by bolting may result in loss of magnetic properties and even damage.
Often the three problems of protection, mounting and retention are solved as the complex. For example wrapping complete rotor with fiberglass bandage solves the problems of protection and retention of poles but has the disadvantage that this technology cannot be applied in radial-flux machines with external rotor and in axial-flux machines and the magnets cannot be removed for magnetization in case of an irreversible demagnetization event. The alternative, especially for large machines, is the use of polar elements. Each pole may consist of one or several polar elements.
The polar elements usually consist of one or several stacked permanent magnets fixed to a base plate and covered with some sort of protective casing around. The base plate has arrangements for fixing the polar element to the rotor yoke. The magnets in the polar element may be magnetized after they are assembled with the base plate and casing, so the process of assembly of the polar element happens with non-magnetized magnets.
The polar element concept solves all the above problems providing convenient mounting and dismantling of magnetic poles as well as protection and retention of the magnets.
The advantage of the solution with polar elements is to perform machining, gluing and welding (if required) on a demagnetized system.
Various concepts of polar elements have been proposed, for example, in patent applications WO2007116118 (Al) and WO2009068736 (Al) by Neorem and US2008276449 (Al) by Siemens. Connection of the base plate and protective casing in WO2009068736 (Al) is made by a groove which extends substantially over the entire length of the lateral surface of the base plate and a joint member which is formed by bending the edge of the skirt of the housing inside the groove over a substantial portion of the total length of the skirt. This solution is not ideal as it is difficult to make and its long lifetime is doubtful. In WO2007116118 (Al) as well as in WO2009068736 (Al) the base plate and the casing are made of soft-iron steel and stainless steel, respectively, which may result in corrosion of the joint due to materials incompatibility.
Drawbacks of the solution in US2008276449 (Al) are that the layer of filler mass between the protective casing and the magnet reduces the mechanical air gap and that evacuation of cavity and injection of the filling mass are quite complex operations. Moreover, the holes in base plate or the casing do not make the solution ideally sealed for applications like, for example, the ones where rotor is submerged.
Object
The objective of the invention is to provide a permanent magnet polar element which is free from the drawbacks referred to above, namely from using the unreliable mechanical joint, having holes in casing and/or base plate and using filler mass.
Specifically, the objective of the invention is to provide a permanent magnet polar element in which complete sealing is achieved by relatively simple measures and at the same time providing more reliable and long-term operation of the arrangement.
The invention
A permanent magnet polar element according to the invention is described in claim 1. Details and preferred features of the permanent magnet polar element are described in claim 2-11. A method for providing a permanent magnet polar element according to the invention is described in claim 12 and 13. Details and preferred features of the method are described in claim 14.
To provide complete sealing of magnets, a joint between a base plate and a protective casing is made by welding. For the same purpose through holes are made neither in the casing nor in the base plate. No filling mass is to be used under the protective casing. To ensure minimum air space under the protective casing, protective casing is manufactured with small tolerances and follows the shape of the permanent magnets in a stack.
To prevent corrosion in the joint between the base plate and the casing, they are made of the same material or of compatible materials. As the base plate must have high magnetic permeability for conducting magnetic flux it can be made of soft iron. Accordingly the protective casing may be made of soft iron as well. The base plate has arrangements for fastening to a rotor yoke. It can be for example screwing or bolting.
The magnets can be magnetized after the assembly is totally sealed. This way there would be no concerns on the heat developed during welding destroying the magnets.
A method according to the present invention can be summarized as follows:
arranging one or more un-magnetized permanent magnets to a base plate, arranging a protective casing over the base plate and the one or more permanent magnets and welding the protective casing and the base plate together,
- magnetizing the permanent magnets after the base plate and the protective casing are welded together and the assembly is totally sealed, and
arranging the base plate and the permanent magnets to a rotor yoke of an electrical machine.
The method further includes that the permanent magnets are arranged to the base plate by means of e.g. gluing.
The magnets can alternatively be magnetized before the arrangement.
Further details and advantageous features of the invention will appear from the following example description. Example
The invention is further described with reference to accompanying drawings:
Figure 1 shows an exploded view of a polar element or part of a polar element and shows details of this,
Figure 2 shows a part (section) of a rotor yoke with magnet poles, where each pole consists of many small permanent magnets, and Figure 3 shows details of permanent magnets with and without a protective casing.
Reference is now made to Figure 1 which shows details of a permanent magnet polar element 11 according to the invention for arrangement to a rotor yoke 12 (shown in Figure 2 and 3) of an electrical machine. A permanent magnet polar element 11 according to the invention includes one or more permanent magnets 13, which one or more magnets 13 are arranged to one or more base plates 14 by suitable means, such as by gluing. The permanent magnet polar element 11 further includes one or more protective casings 15.
Reference is now made to Figure 2 which shows a part 16 (section) of a rotor yoke 12 of an electrical machine, with magnet poles 17. The base plate(s) 14 and protective casing(s) 15 are not shown in this Figure. One pole 17 of the machine may consist of several polar elements 11 or of only one polar element 11. The size and number of polar elements 11 is chosen from production and mounting point of view.
In the figure this is shown by each pole 17 consisting of a stack of small permanent magnets 13. The poles 17 preferably have alternating polarity, i.e. North (N) and South (S).
Reference is now made to Figure 3 which shows polar elements 11 arranged to the rotor yoke 12, both with the protective casing 15 and without the protective casing 15.
The base plate 14 is provided with means 18, such as protruding elements provided with through holes for connection screws for fastening of the base plate 14 to the rotor yoke 12 of the electrical machine.
The protective casing 15 preferably extends so that it surrounds the permanent magnets 13 from all sides except bottom side, and also surrounds the base plate 14.
According to the invention the protective casing 15 is arranged to the base plate 14 by means of a welded joint 19, as shown in Figure 1. This ensures a complete sealing of the permanent magnets 13. For the same purpose neither the base plate 14 nor casing 15 has through holes which fall inside the casing 15 after assembling the casing 15 to the base plate 14 by means of the welded joint 19.
The permanent magnet(s) 13 is/are preferably arranged to the base plate 14 prior to the protective casing 15 and base plate 14 are welded together, ensuring that the permanent magnet(s) 13 are hermetically sealed between the protective casing 15 and the base plate 14. By doing it like this no filling mass, for example epoxy or resin, or other filler elements is used to fill the space between the permanent magnets 13 and the casing 15 for sealing the permanent magnets 13.
The protective casing 15 can further be sectionalized to form one whole protective cover 15 covering the polar element 11. The protective casing 15 further preferably has a shape which follows the shape the permanent magnet(s) 13 arranged to the base plate 14 under the protective casing 15, so that the space needed between the permanent magnet(s) 13 and the protective casing 15 is minimized.
Both the base plate 14 and the protective casing 15 are preferably made of the same material or the materials which are compatible so that no corrosion occurs at the welded joint 19. Suitable materials for the base plate 14 and the protective casing 15 are soft-magnetic steel or black iron.
The permanent magnet(s) 13 can be arranged like un-magnetized permanent magnet(s) 13, and the permanent magnet(s) 13 is/are magnetized after the base plate 14 and the protective casing 15 are welded together ensuring that heat developed during the welding process will not destroy the permanent magnet(s) 13.
The permanent magnet(s) 13 can alternatively be magnetized before arranging to the base plate 14.
Modifications
To improve corrosion protection, galvanization of polar elements prior to magnetization and galvanization of remaining yoke parts can be done. Other alternatives could be hot spraying of protective metal, metallization of the polar elements and rotor yoke, or painting the protective metal.
If magnetized magnets are used for assembly, the permanent magnets can be arranged to the base plate by means of magnetic force.

Claims

Claims
1. A permanent magnet polar element (11) for arrangement onto a rotor yoke (12) of an electrical machine, including one or more permanent magnets (13), one or more protective casings (15), surrounding the permanent magnet(s) (13) from all sides except bottom side, and a base plate (14), on which at least one permanent magnet (13) is arranged for fixing the polar element (11) to the rotor yoke (12), characterized in that
the base plate (14) and the protective casing (15) are joined by means of a welded joint (19), after the one or more permanent magnets (13) are arranged on the base plate (14) and the base plate (14) is arranged to the rotor yoke (12), providing that the permanent magnet(s) (13) are hermetically sealed between the protective casing (15) and the base plate (14).
2. Permanent magnet polar element according to claim 1, characterized in that both the base plate (14) and the protective casing (15) are made of the same material or materials being compatible to one another so that no corrosion occurs at the welded joint (19).
3. Permanent magnet polar element according to claim 1, characterized in that the protective casing (15) has a shape following the shape of the permanent magnet(s) (13) arranged on the base plate (14) so that a space between the permanent magnets (13) and the protective casing (15) is minimized.
4. Permanent magnet polar element according to claim 1, characterized in that the base plate (14) is provided with means (18) for arrangement to the rotor yoke (12).
5. Permanent magnet polar element according to claim 4, characterized in that the means (18) are protruding elements provided with through holes for connection screws or bolts for fastening of the base plate (14) to the rotor yoke (12).
6. Permanent magnet polar element according to claim 1, characterized in that there are no through holes in the protective casing (15) or in the part of the base plate (14) covered by the protective casing (15).
7. The permanent magnet polar element in claim 1, characterized in that the one or more permanent magnets (13) are arranged to the base plate (14) in un-magnetized state and the polar element (11) is magnetized after the base plate and the protective casing are welded together.
8. The permanent magnet polar element in claim 1, characterized in that the one or more permanent magnets (13) are arranged to the base plate (14) in magnetized state and the base plate and the protective casing is welded together.
9. The permanent magnet polar element in claim 1, characterized in that the permanent magnets (13) are arranged to the base plate (14) by means of gluing or, if magnetized permanent magnets (13) are used for assembly, by means of magnetic force.
10. The permanent magnet polar element in claim 1, characterized in that the base plate (14) and the protective casing (15) are made of soft-magnetic steel or black iron.
11. The permanent magnet polar element in claim 1, characterized in that additional protection of the permanent magnet polar element (11) is provided by galvanization, painting or spraying hot metal on the permanent magnet polar element (11) and the rotor yoke (12).
12. Method for providing a hermetically sealed permanent magnet polar element (11) for arrangement onto a rotor yoke (12) of an electrical machine, characterized in that the method includes:
arranging one or more un-magnetized permanent magnets to a base plate, - arranging a protective casing over the base plate and one or more permanent magnets and welding the protective casing and the base plate together,
magnetizing the permanent magnets after the base plate and the protective casing are welded together and the assembly is totally sealed, and
arranging the base plate and the permanent magnets to a rotor yoke of an electrical machine.
13. Method for providing a hermetically sealed permanent magnet polar element (11) for arrangement onto a rotor yoke (12) of an electrical machine, characterized in that the method includes:
- arranging one or more magnetized permanent magnets to a base plate,
arranging a protective casing over the base plate and one or more permanent magnets and welding the protective casing and the base plate together,
arranging the base plate and the permanent magnet to a rotor yoke of an electrical machine.
14. Method according to claim 12 or 13; characterized in galvanizing, painting or spraying hot metal on the permanent magnet polar element and of remaining yoke parts for additional protection against corrosion.
PCT/NO2011/000121 2010-04-13 2011-04-12 Arrangement and method for protection, mounting and retention of magnetic pole WO2011129702A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20100524A NO331238B1 (en) 2010-04-13 2010-04-13 Arrangement and method for protection, mounting and retention of magnetic pole
NO20100524 2010-04-13

Publications (1)

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WO2011129702A1 true WO2011129702A1 (en) 2011-10-20

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WO (1) WO2011129702A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130120505A1 (en) * 2011-11-10 2013-05-16 Xerox Corporation Bonded silicon structure for high density print head

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Publication number Priority date Publication date Assignee Title
NO333881B1 (en) 2012-03-26 2013-10-07 Rolls Royce Marine As Rotor comprising segmented yoke

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Publication number Priority date Publication date Assignee Title
EP0269216A1 (en) * 1986-10-30 1988-06-01 General Motors Corporation Permanent magnet assembly
WO2007116118A1 (en) * 2006-04-07 2007-10-18 Neorem Magnets Oy Polar element for a permanent magnet
EP1990811A1 (en) * 2007-05-09 2008-11-12 Siemens Aktiengesellschaft Method for permanent magnet protection
WO2009068736A1 (en) * 2007-11-30 2009-06-04 Neorem Magnets Oy Surface-mountable permanent magnet element
EP2075898A1 (en) * 2007-12-31 2009-07-01 General Electric Company Permanent magnet assembly and method of manufacturing same

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Publication number Priority date Publication date Assignee Title
FI113308B (en) * 2001-06-14 2004-03-31 Abb Oy Permanent magnet element and electric machine

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Publication number Priority date Publication date Assignee Title
EP0269216A1 (en) * 1986-10-30 1988-06-01 General Motors Corporation Permanent magnet assembly
WO2007116118A1 (en) * 2006-04-07 2007-10-18 Neorem Magnets Oy Polar element for a permanent magnet
EP1990811A1 (en) * 2007-05-09 2008-11-12 Siemens Aktiengesellschaft Method for permanent magnet protection
WO2009068736A1 (en) * 2007-11-30 2009-06-04 Neorem Magnets Oy Surface-mountable permanent magnet element
EP2075898A1 (en) * 2007-12-31 2009-07-01 General Electric Company Permanent magnet assembly and method of manufacturing same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130120505A1 (en) * 2011-11-10 2013-05-16 Xerox Corporation Bonded silicon structure for high density print head
US8727508B2 (en) * 2011-11-10 2014-05-20 Xerox Corporation Bonded silicon structure for high density print head

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NO20100524A1 (en) 2011-10-14
NO331238B1 (en) 2011-11-07

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