PATENT DOCUMENT

Publication Number: US-9914250-B2
Application Number: US-201313955996-A
Country: US
Kind Code: B2

Title: Retention of magnetic properties

Abstract:
Methods, systems, and apparatuses for retaining magnetic properties of magnetic elements while undergoing manufacturing processes are presented. In one embodiment, a manufacturing fixture includes a temperature controlled region suitable for retaining a magnetic element. The manufacturing fixture also includes a cooling mechanism configured to maintain the magnetic element at an acceptable temperature range during a thermally active manufacturing process. The temperature controlled or stabilized region can include a structure configured to receive the magnetic element and a sensor, or sensors. In one embodiment, the sensor can be configured to measure an ambient temperature of the temperature stabilized region. In another embodiment, the sensor can be a magnetic sensor configured to determine a magnetic property of the magnetic element.

Claims:
What is claimed is: 
     
       1. A fixturing device for maintaining a magnetic flux density of a magnetic element during a thermally active manufacturing process, the fixturing device comprising:
 a fixturing device housing having walls that define a cavity that is capable of receiving the magnetic element; 
 a magnetometer configured to measure a change in the magnetic flux density of the magnetic element; 
 a cooling mechanism in communication with the magnetometer and having a channel embedded at least partially within the magnetic element; and 
 a feedback control mechanism in communication with the cooling mechanism and configured to receive the change in the magnetic flux density from the magnetometer, wherein the feedback control mechanism is capable of (i) comparing the change in the magnetic flux density to a pre-determined range of magnetic flux density, and (ii) activating the cooling mechanism to move coolant medium through the channel to directly cool the magnetic element during the thermally active manufacturing process in response to determining that the change in the magnetic flux density is outside the pre-determined range. 
 
     
     
       2. The fixturing device as recited in  claim 1 , wherein the magnetic element includes a plurality of magnets and the cooling mechanism is configured to receive heat directly from the plurality of magnets. 
     
     
       3. The fixturing device as recited in  claim 1 , wherein the magnetic element is a high flux density magnet or magnetic array. 
     
     
       4. The fixturing device as recited in  claim 1 , wherein the channel comprises seals that prevent the coolant medium from passing through the walls that define the cavity. 
     
     
       5. The fixturing device as recited in  claim 1 , wherein the walls confine the magnetic element within the cavity. 
     
     
       6. The fixturing device as recited in  claim 1 , wherein the channel includes a thermal insulated jacket that is configured to limit cooling to the magnetic element. 
     
     
       7. The fixturing device as recited in  claim 1 , wherein a rate of moving the coolant medium through the channel corresponds to the change in the magnetic flux density of the magnetic element. 
     
     
       8. The fixturing device as recited in  claim 1 , wherein the magnetic element is encased within a thermal isolation layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/745,479, filed Dec. 21, 2012 and entitled “RETENTION OF MAGNETIC PROPERTIES” by Rappoport et al., which is incorporated by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present discussion relates generally to magnetic properties of magnets and more particularly to retaining magnetic properties of magnets during processing at elevated temperatures. 
     BACKGROUND 
     Magnets are becoming more and more common in consumer products. In particular, magnets can be found in computing device such as laptops, covers for tablet devices, wearable devices such as wrist straps, and so on. Generally speaking it is preferable that magnets provide as strong a magnetic field as possible in as small a space as possible. Accordingly magnets that provide a high magnetic flux density and yet are relatively small in size can be used in a number of applications. Unfortunately, elevated temperatures can cause magnets to become partially or totally demagnetized. In particular, high flux density magnets such as neodymium (NIB) magnets are highly sensitive to elevated temperatures. More particularly, the strongest grade (N50 to N52 range) magnets can experience serious demagnetization at relatively low temperatures. For example, a NIB magnet of grade N52 can have a maximum operating temperature of about 50° C. above which the desired magnetic properties (such as magnetic strength expressed as magnetic flux density, for example) of the NIB magnet will seriously degrade. Unfortunately, however, in order to effectuate magnets in various consumer products, a thermally active manufacturing process (such as injection molding) is used in which a thermoplastic or resin at an elevated temperature exposes the magnetic element to temperatures above the maximum operating temperature. In these situations, the magnetic element can suffer serious demagnetization. 
     Therefore, what is needed is a way to configure magnets to be able to withstand elevated temperatures without losing some or all of their magnetic properties. 
     SUMMARY 
     The present application describes various embodiments regarding systems and methods for maintaining magnetic properties of a magnet at an acceptable value during a heat based manufacturing process. 
     In one embodiment, a fixturing device for maintaining magnetic properties of a magnetic element during a thermally active manufacturing process is disclosed. The fixturing device includes at least the following elements: a fixturing device housing having walls that define a cavity; a magnetic element retaining feature disposed within the cavity and configured to retain the magnetic element within the cavity of the fixturing device housing; a sensor configured to provide information in accordance with a characteristic of the magnetic element; and a cooling mechanism in communication with the sensor and having a transport conduit embedded at least partially within the walls of the fixturing device housing. The cooling mechanism is configured to move coolant medium through the transport conduit and into thermal contact with the magnetic element during the thermally active manufacturing process in response to information received from the sensor. 
     In another embodiment, a magnetic element can include a thermal isolation layer. The thermal isolation layer can act to increase a thermal resistance between the magnetic element and an external environment. The thermal isolation layer can effectively isolate the magnetic element from heat associated with the external environment. In this way, the magnetic properties of the magnetic element can be maintained within an acceptable level during a thermally active manufacturing process. 
     In another embodiment a method of maintaining a magnetization value of a magnetic element during a thermally active manufacturing process is described. The method can be carried out by determining a current temperature of the magnetic element and comparing the current temperature to a predetermined temperature limit. In some aspects of the described embodiment, the predetermined temperature can be below a critical operating temperature being that temperature at which a magnetization of the magnetic element is reduced below a first threshold. If the current temperature of the magnetic element is determined to be at or above the predetermined temperature limit, then cooling resources are provided until the current temperature of the magnetic element is determined to be within an acceptable temperature range. 
     In yet another embodiment, a method of maintaining a magnetization value of a magnetic element during a thermally active manufacturing process is described. The method is carried out by measuring a current magnetic property of the magnetic element. The magnetic property can be related to a magnetic flux density of the magnetic element. The magnetic property can be related to a magnetic strength value. The magnetic property can be determined using a magnetometer. The magnetic property can be monitored during the thermally active manufacturing process. The magnetic property can trigger the providing of and an amount of cooling resources provided to the magnetic element. For example, a decrease in the measured magnetic property can cause an increase in an amount of cooling resources provided. In this way, the amount of cooling resources can be directly related to a measured magnetic property. 
     Other apparatuses, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The included drawings are for illustrative purposes and serve only to provide examples of possible structures and arrangements for the disclosed inventive apparatuses and methods for providing portable computing devices. These drawings in no way limit any changes in form and detail that may be made to the invention by one skilled in the art without departing from the spirit and scope of the invention. The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIGS. 1A-1E  show by way of example magnetic elements useable in thermally active processes. 
         FIGS. 2A-2E  show by way of example magnetic elements embedded within substrates formed through thermally active processes 
         FIG. 3  shows a manufacturing system in according with the described embodiments. 
         FIGS. 4A-4B  show manufacturing fixtures of a manufacturing system in accordance with the described embodiments. 
         FIG. 5  is a flow chart of a process in accordance with the described embodiments. 
         FIG. 6  is a flow chart of a process in accordance with the described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Representative applications of apparatuses and methods according to the presently described embodiments are provided in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the presently described embodiments can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the presently described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     The following paper describes a system and method suitable for maintaining magnetic properties of magnetic element during a thermally active manufacturing process. For example, a magnet can be embedded in an elastomeric material and/or thermoplastic resin during an injection molding process. Any temperature related degradation of magnetic properties can be reduced or avoided altogether. In one embodiment, a manufacturing fixture includes a temperature controlled region suitable for retaining a magnetic element. The manufacturing fixture also includes a cooling mechanism configured to maintain the magnetic element at an acceptable temperature range during a thermally active manufacturing process. The temperature controlled or stabilized region can include a structure configured to receive the magnetic element and a sensor, or sensors. In one embodiment, the sensor can be configured to measure an ambient temperature of the temperature stabilized region. In another embodiment, the sensor can be a magnetic sensor configured to determine a magnetic property of the magnetic element. 
     Using information from the sensor, the cooling mechanism can mitigate any adverse changes to a temperature sensitive property of the magnetic element. For example, an ambient temperature of the temperature stabilized region can be maintained within an acceptable temperature range. In one embodiment, thermal feedback control between a temperature sensor in the temperature stabilized region and the cooling mechanism can be used. In another embodiment, a magnetic sensor can provide a signal corresponding to a measured value of a magnetic parameter of the magnetic element to a feedback controller that uses the signal to maintain to the desired magnetic property by adjusting a temperature of the magnetic element. The sensor can take the form of a magnetometer. For example, a change in a measured magnetic property of the magnetic element below a specific threshold can be used as a trigger to control an amount of cooling provided by the cooling mechanism. 
     In another embodiment, a magnetic element can include a thermal isolation layer. The thermal isolation layer can act to increase a thermal resistance between the magnetic element and heat associated with an external environment. The thermal isolation layer can effectively isolate the magnetic element from the external environment. In this way, the magnetic properties of the magnetic element can be maintained within an acceptable level during a thermally active process. 
     In another embodiment a method of maintaining a magnetization value of a magnetic element during a thermally active manufacturing process is described. The method can be carried out by determining a current temperature of the magnetic element and comparing the current temperature to a predetermined temperature limit. In some aspects of the described embodiment, the predetermined temperature can be below a critical operating temperature being that temperature at which a magnetization of the magnetic element is reduced below a first threshold. If the current temperature of the magnetic element is determined to be at or above the predetermined temperature limit, then cooling resources are provided until the current temperature of the magnetic element is determined to be within an acceptable temperature range. 
     In yet another embodiment, a method of maintaining a magnetization value of a magnetic element during a thermally active manufacturing process is described. The method is carried out by measuring a current magnetic property of the magnetic element. The magnetic property can be related to a magnetic flux density of the magnetic element. The magnetic property can be related to a magnetic strength value. The magnetic property can be determined using a magnetometer. The magnetic property can be monitored during the thermally active manufacturing process. The magnetic property can trigger the providing and amount of cooling resources provided to the magnetic element. A decrease in the measured magnetic property can cause an increase in an amount of cooling resources provided. In this way, the amount of cooling resources can be directly related to a measured magnetic property. 
     According to the embodiments described herein, a magnetic element can be embedded within a substrate while maintaining desired magnetic properties. The thermally active process includes at least an injection molding process, molding magnets in thermosets (such as, for example, compression molded rubbers), laminating magnets inside of soft materials (such as stackups of TPU, neoprene, leather, cotton, microfibers, and polyesters). By maintaining the original magnetic properties of the magnetic element, the need for re-magnetizing the magnetic element can be greatly reduced or even eliminated. In this way, complex magnetic patterns (used, for example, in auto location applications) can be more easily maintained. 
     This and other embodiments are discussed below with reference to the many Figures. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
       FIGS. 1A-1E  show by way of example magnetic elements useable in thermally active processes. As depicted in  FIG. 1A , a magnetic element  11  may include two magnetic poles useful in attracting other magnetic elements and/or ferromagnetic materials. For example, the magnetic element  11  may be embedded within a substrate and used to attract, lock, engage, or otherwise exert attractive/repulsive forces on a neighboring substrate (or material embedded in the substrate). Although only two poles are illustrated, the same may be varied by forming arrays of magnets or magnetic elements. As depicted in  FIG. 1B , a magnetic element  14  may be formed from a plurality of magnetic elements  20 ,  21 ,  22 ,  23 , each being aligned or coordinated with adjacent elements to achieve a desired magnetic property (e.g., for auto-location features or other features). Although illustrated as having one pole, it is understood that each element  20 ,  21 ,  22 ,  23  has two proper magnetic poles not labeled for clarity of illustration. Magnetic elements  11  and  14  may be embedded within a substrate in a thermally active process as described herein, for example, using a cooling mechanism to maintain desired magnetic properties. However, enhanced magnetic elements having thermal isolation layers to further facilitate retention of magnetic properties are also described herein. 
     For example, as illustrated in  FIG. 1C , magnetic element  32  may be encased or otherwise coated in a thermal isolation layer  31 . The thermal isolation layer  31  can act to increase a thermal resistance between the magnetic element  32  and heat associated with an external environment. The thermal isolation layer  31  can effectively isolate the magnetic element  32  from the external environment. The thermal isolation layer  31  may include any suitable material, including, for example, leather, ceramic, polymer, rubber (synthetic or natural), and/or any other suitable material capable of at least partially increasing a thermal resistance between the magnetic element  32  and heat associated with an external environment. The thermal isolation layer  31  may be used to cover a plurality of individual magnetic elements as illustrated in  FIG. 1D . Additionally, the thermal isolation layer  31  may be used to individually cover separate magnetic elements  42 ,  43  with individual isolation layers as illustrated in  FIG. 1E . 
     Turning now to  FIGS. 2A-3E , several magnetic elements described above are illustrated embedded within substrates formed through a thermally active process. As depicted in  FIG. 2A , magnetic element  11  is embedded within substrate  10 , formed using a thermally active process. The thermally active process includes at least an injection molding process (used to create the substrate  10  while embedding element  11 ), molding magnetic element  11  in thermosets (such as, for example, compression molded rubbers), laminating magnetic element  11  inside of soft materials (such as stackups of TPU, neoprene, leather, cotton, microfibers, and polyesters), or other suitable processes. Although illustrated as a single layer, it is understood that the substrate  10  may include a plurality of differing layers, segments, or other portions not particularly illustrated. Similar to element  11 , magnetic element  14  may also be embedded within substrate  14  as illustrated in  FIG. 2B . 
       FIGS. 2C-2E  also show magnetic elements  20 ,  21 ,  22 ,  23 ,  32 ,  42 ,  43  embedded within substrate  10 . However, it is noted that as thermal isolation layer  31  is arranged to protect these elements, a cooling mechanism may or may not have been used for the entire thermally active manufacturing process (i.e., not run at full cooling capacity or otherwise altered to accommodate the isolation properties of layer  31 ). In some embodiments, the thermally active manufacturing process remains the same or similar across manufacturing of the substrates illustrated in  FIGS. 2A-2E . In some other embodiments, the thermally active manufacturing process is slightly or significantly changed according to the type of magnetic element (i.e., linear array, multiple magnets, multiple arrays, etc) being embedded, the type of cooling mechanism or thermal isolation layer implemented, or other attributes. 
     The substrate  10  may differ from the particular forms illustrated and described above according to some embodiments. Furthermore, although illustrated as having magnetic elements totally embedded within the substrate  10 , it should be understood that the same may be varied such that one or more surfaces of a magnetic element are exposed to an area external to the substrate (e.g., through a window, recess, against an exterior surface of the substrate, etc). Accordingly, the particular forms illustrated represent only several possible example implementations, and are in no way limiting. 
     The substrate  10  illustrated in  FIGS. 2A-2E  may be formed in any suitable system. According to one embodiment,  FIG. 3  shows an exemplary system  100  for forming substrates with magnets embedded therein. The system  100  may include a controller  101  arranged to control the system  100 . The controller  101  may include any suitable controller, including a programmable logic controller, computer processer, or any other suitable controller. 
     The system  100  further includes cooling system  102  in communication with the controller  101 . The cooling system  102  may include a cooling mechanism configured to provide or cycle coolant through the system  100  based on commands from the controller  101  or through other manners (e.g., by opening of a valve by controller  101 , by receipt of a signal from controller  101 , etc). Generally, the cooling system  102  may include any suitable components for operation, including heat exchangers, pumps, valves, and any other cooling component. 
     The system  100  further includes a Hopper/Material Provision Component  103  in communication with controller  101 . The hopper  103  may provide ingots, pellets, pieces, or otherwise configured material for the thermally active manufacturing process implemented by system  100 . The hopper  103  may receive commands to begin operation or provision of material from controller  101 , or may be otherwise controlled (e.g., by a user/technician, through machine interlocks from another component, system, or machine, etc). 
     The system  100  further includes thermal system  104  in communication with the controller  101 . The thermal system  104  may include a power source (or may receive power external thereto) and may be configured to heat a portion of the system  100  (e.g., a die or manufacturing implement such as a fixture, a mixing nozzle, etc) to melt or otherwise transform material provided through the hopper  103  at molding components  105  and mold fixture  106 . As material is provided from hopper  103 , molding components  105  receive the material, heat and at least partially melt the material, and mold the same in mold fixture  106  to form a substrate (e.g.,  10 ) with a magnetic element embedded therein. Generally, cooling system  102  maintains an acceptable temperature about the magnetic element or elements in the mold fixture  106  such that desirable magnetic properties are maintained. 
       FIG. 4A  shows a detailed view of a fixture portion (e.g.,  105 / 106 ) of system  100  in accordance with the described embodiments. System  100  can include the fixture  106  that can include temperature controlled region  141  suitably sized and shaped to accommodate magnetic element  161 , for example, by way of a magnetic element retention feature, indentations, standoffs, or any other suitable feature. In some embodiments, magnetic element  161  can be surrounded by a thermal isolation layer (e.g.,  31 ; not shown here) that can provide additional thermal isolation between magnetic element  161  and embeddant  181  (such as thermoplastic resin, rubber, elastomer, etc) injected into cavity  111  during a thermally active manufacturing process (such as injection molding process). In order to maintain magnetic element within an acceptable temperature range, sensor  120  (e.g., thermocouple, magnetometer, diode, etc) can provide information to a processor (e.g., controller  101 ) that can control an amount of coolant provided through cooling system portion  114  (e.g., shown coupled to cooling system  102 ). Cooling system  102  is an active cooling system as it is configured to circulate coolant through system  100 . In one embodiment, cooling system portion  114  can include conduits  116  that can direct coolant to temperature controlled region  141 . In some cases, the coolant can be in direct thermal contact with magnetic element  161  using a thermal conductor (not shown) between the coolant and magnetic element  161 . In order to prevent undo exposure of embeddant  181  to the coolant (with a possible adverse affect on the properties of embeddant  181 ) the coolant can be thermally isolated from cavity  111 . For example, cooling system portion  114  can include jacket  118  formed of thermally insulating material having the effect of limiting the thermal effects of the coolant to only magnetic element  161 . 
     An alternative embodiment is illustrated in  FIG. 4B  in which the coolant is configured to flow through a portion of magnetic element  161 . Interfaces  151  can be provided to interface with a conduit disposed within magnetic element  161  to facilitate coolant transfer between mold  100  and magnetic element  161 . Interfaces  151  can be configured to position magnetic element  161  within mold  100 . Furthermore, interfaces  151  can include seals that couple with corresponding ones of a number of conduit openings in magnetic element  161 . The seals are operative to establish a secure channel between interfaces  151  and magnetic element  161 , such that coolant is prevented from escaping into the mold cavity during an injection molding operation. In this way, the coolant can come into direct contact with magnetic element  161 , thereby allowing heat to be removed by direct thermal conduction between the coolant and magnetic element  161 . In such a configuration sensor  120  can be disposed on a surface of one of interfaces  151  such that sensor  120  can be in close proximity to magnetic element  161 . 
       FIG. 5  is a flow chart of process  200  for maintaining magnetic properties of a magnetic element during a thermally active manufacturing process in accordance with the described embodiments. Process  200  begins at  202  by measuring a property of the magnetic element. In one embodiment, the property is a temperature of the magnetic element (or a magnetic property of the magnetic element). At  204 , the measured temperature is compared to a maximum operating temperature of the magnetic element. If the measured temperature is greater or within a predetermined range of the maximum operating temperature of the magnetic element that does not exceed the maximum operating temperature, then the temperature of the magnetic element is reduced at  206 . At  208 , if the process is not complete than control is passed back to  202 , otherwise, process  200  ends. 
       FIG. 6  is a flow chart of process  300  for maintaining magnetic properties of a magnetic element during a thermally active manufacturing process in accordance with the described embodiments. Process  300  begins at  302  by measuring a property of the magnetic element. In the illustrated embodiment, the property is a magnetic flux density of the magnetic element (or another magnetic property of the magnetic element). At  304 , the measured property is compared to a design threshold of the magnetic element. If the measured property is within a predetermined range of the design threshold of the magnetic element, then the temperature of the magnetic element is reduced at  306  to maintain the desired design threshold and/or measured magnetic property. At  308 , if the process is not complete than control is passed back to  302 , otherwise, process  300  ends. 
     Although the foregoing invention has been described in detail by way of illustration and example for purposes of clarity and understanding, it will be recognized that the above described invention may be embodied in numerous other specific variations and embodiments without departing from the spirit or essential characteristics of the invention. Certain changes and modifications may be practiced, and it is understood that the invention is not to be limited by the foregoing details, but rather is to be defined by the scope of the appended claims.

Metadata:
Filing Date: 20130731
Publication Date: 20180313
Grant Date: 20180313
Priority Date: 20121221
Inventors: WEBER DOUGLAS JOSEPH
QUINTERO JULIO C.
RAPPOPORT BENJAMIN M.
SMITH, IV HARRY W.
Assignee: APPLE INC
CPC Classifications: [{"code": "B29C2945/76157", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29K2995/0008", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/14836", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C2945/76545", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76531", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76772", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76933", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76782", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76294", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/78", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C2945/76294", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76772", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/14836", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C2945/76157", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76545", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C45/78", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C2945/76782", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29K2995/0008", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76933", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C2945/76531", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50973282