AU2015101725A4 - A magnetic lifter - Google Patents

Abstract

A magnetic lifter (10) for lifting a target object having a relatively high magnetic susceptibility includes a body (12) and a magnetic component (22) received within the body (12). The body (12) has a spacer (20) at one end to space the magnetic 5 component (22) from the target object. The magnetic component (22) is driven between an operative position on one side of the spacer (20), such that the magnetic force of the magnetic component (22) attracts the target object against the other side of the spacer (20) and an inoperative position spaced from the spacer (20) such that the magnetic force on the target object is reduced to release the target object. The magnetic 10 component (22) is connected to a driver (14) providing a mechanical force to move the magnetic component (22) from the operative to the inoperative position. A method of lifting a lid of an oven tin is also disclosed.

Description

AUSTRALIA Patents Act 1990 INNOVATION PATENT SPECIFICATION FOR THE INVENTION ENTITLED: A magnetic lifter Applicant: George Weston Foods Limited The invention is described in the following statement: 1 A MAGNETIC LIFTER Field of the invention The present invention relates to a magnetic lifter for lifting a target object having a relatively high magnetic susceptibility such as a ferromagnetic object. In particular, 5 although not exclusively, the invention relates to a magnetic lifter for lifting a lid of a bread tin such as those typically found in a commercial scale bakery. The invention also relates to a method of lifting a bread tin lid. Background of the invention Magnetic lifters have been used in commercial scale bakeries. Typically, they 10 comprise a magnetic component acting as a piston within a housing having a cylindrical bore. The magnetic component is movable within the housing and is driven pneumatically to move between upper and lower positions by the introduction of air either above or below the magnetic component. Seals interface between the magnetic component and the inside wall of the whole housing. In the lower position, the magnetic 15 component rests against the base plate of the housing, which is relatively thin so as to minimise the disruption to the magnetic field below the base plate. In the lower position, the magnetic component attracts the lid of the bread tin and lifting and moving of the lid is achieved by movement of the housing. To release the lid, the magnetic component is moved to the upper position whereby the magnetic force acting upon the lid is 20 insufficient to hold the lid and the lid is released. The weak strength of the base plate thus limits the pressure rating of the housing and the effectiveness of the pneumatics in moving the magnetic component. Thus, once the seals lose their effectiveness due to accelerated wear in the high temperature environment, the pressure cannot be increased to compensate for this and the magnetic lifters are prone to failure. 25 Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art. 2 It is therefore an objection of the present invention to overcome or at least ameliorate the abovementioned disadvantage. An alternative object of the present invention is to provide the public with a useful choice over known magnetic lifters. 5 Summary of the invention In accordance with the first aspect of the present invention, there is provided a magnetic lifter for lifting a target object having a relatively high magnetic susceptibility, the magnetic lifter including: a body; 10 a magnetic component received within the body; the body having a spacer at one end to space the magnetic component from the target object; the magnetic component being driven between: an operative position on one side of the spacer, such that the magnetic 15 force of the magnetic component attracts the target object against the other side of the spacer; and an inoperative position spaced from the spacer such that the magnetic force on the target object is reduced to release the target object, wherein the magnetic component is connected to a driver providing a 20 mechanical force to move the magnetic component from the operative to the inoperative position. The provision of a driver providing a non-pneumatic mechanical force to the magnetic component obviates the need to pressurise the housing/body and obviates the need for seals on the magnetic component. 25 The magnetic component may comprise a magnet alone. Alternatively, the magnetic component may comprise a magnetic assembly having a magnet and 3 additional components designed to attach the magnet to the driver and/or to guide the magnet within the body. The body may be in any form provided it receives the magnetic components and provides for movement between the operative and inoperative position of the magnetic 5 component. The body may act as a guide for the magnetic component in the course of its movement. In a preferred form of the invention, the body is in the form of a housing or a receptacle. The housing or the receptacle may have a bore commensurate with the shape of the magnetic component. A clearance fit or larger may be provided between the magnetic component and the bore of the housing/receptacle. The 10 magnetic component is absent the seals that were required in the prior art because the magnetic component is no longer driven by pneumatic force. This simplifies the magnetic component and obviates the problem associated with failure of the seals. The spacer preferably forms one wall of the housing/receptacle. Preferably, the spacer is disposed to define the bottom wall of the housing. The housing is preferably 15 constructed of a non-magnetisable material, in other words a material with low magnetic susceptibility such as aluminium. The spacer is relatively thin e.g. 2mm maximum. The operative position of the magnetic component is preferably adjacent the spacer and most preferably, in contact with the spacer. The driver may be a linear actuator. Preferably, the linear actuator is substantially 20 external to the body, with the shaft projecting into the body for connection to the magnetic component. It will be understood that the connection between the driver and the magnetic component is a physical connection. Intervening components may be provided between the shaft and the magnetic component. In a preferred form of the invention, the shaft of the linear actuator extends through an aperture in a wall of the 25 receptacle/housing and is guided within the aperture. The aperture may be disposed in a wall of the housing opposite the spacer. Most preferably, the aperture is defined in the top wall and the linear actuator is disposed above the body. The linear actuator may comprise a pneumatic or hydraulic cylinder. In a most preferred form, the linear actuator is a high temperature pneumatic linear actuator. 4 The magnetic component may include a keeper plate and a magnet holder to secure the magnetic component to the shaft of the linear actuator. The keeper plate may have a high magnetic susceptibility and the magnetic force provides the connection between the keeper plate and the magnet. The magnet holder may have low magnetic 5 susceptibility and defines a collar to surround the magnet so that the magnet is shrouded and does not contact the side wall of the bore in the housing/receptacle. The magnet holder is attached to the keeper plate by suitable fasteners. When referring to "magnetic susceptibility" we refer to the degree of magnetisation of a material in response to an applied magnetic field. A reference to 10 relatively high magnetic susceptibility typically includes ferromagnetic materials such as iron, nickel, cobalt and manganese, or their compounds. By low magnetic susceptibility, we mean those materials that are relatively non magnetisable in comparison to ferromagnetic materials. Typically, aluminium has a low magnetic susceptibility. 15 In accordance with a second aspect of the present invention, there is a provided a method of lifting a lid of an oven tin wherein the lid has a high degree of magnetic susceptibility, the method including: providing a magnetic lifter which includes a magnetic component received within a body having a spacer at one end, wherein the magnetic component is connected to a 20 driver providing a mechanical force to move the magnetic component; driving the magnetic component to an operative position within the body, on one side of the spacer to attract and attach the lid to the other side of the spacer; driving the magnetic component to an inoperative position spaced from the spacer, to reduce the magnetic force on the lid and thereby release the lid. 25 Preferably, the body is oriented such that the spacer lies substantially horizontally. The method includes driving the magnetic component to the operative position and moving the body so that the target lid lies underneath the spacer. In this position of the magnetic component, the magnetic force exceeds the weight of the lid, enabling the lid to be lifted by moving the body. When desired, the lid may be released 5 by moving the magnet to the inoperative position such that the magnetic force is less than the weight of the lid so that the lid falls under its own weight. The lid is preferably the lid of a bread tin for a commercial scale bakery. Any of the features described above in connection with the first aspect of the 5 invention may be applied to the second aspect of the invention. As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. 10 Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. Brief description of the drawings In order that the invention may be more fully understood, one embodiment will 15 now be described by way of example with reference to the figures in which: Figure Ia is a cross sectional view of the magnetic lifter according to a preferred embodiment of the present invention, with the magnetic component in the upper, inoperative position; Figure lb is a cross sectional view of the magnetic lifter of Figure la, with the 20 magnetic component in the lower, operative position; Figure 2 is an exploded view of the component of the magnetic lifter of Figure 1; Figures 3a and 3b are cross sectional and top views of the housing; Figures 4a, 4b and 4c are top plan, cross-sectional and underside views of the closure for the housing of Figure 3; 25 Figures 5a, 5b and 5c are top plan, cross-sectional and underside views of the keeper plate; 6 Figures 6a, 6b and 6c are top plan, cross-sectional and underside views of the magnet holder, Figures 7a, 7b and 7c are top plan, cross-section and underside views of the post mounting plate. 5 Detailed description of the embodiments Figure 1 illustrates a magnetic lifter 10 including a body 12 in the form of a receptacle with a pneumatic linear actuator 14 mounted above the receptacle 12. The receptacle 12 is in the form of a housing 16 providing a cylindrical bore with an upper open end which is closed by a closure 18. The bottom wall of the housing 16 is a 10 relatively thin plate 20. The thin plate 20 acts as a spacer between the magnetic component 22 within the receptacle 12 and the lid of the bread tin (not shown). The housing 16 and the closure 18 are made of aluminium and the closure 18 is screw-fastened to the top of the cylindrical housing 16. The top and bottom of the cylindrical housing 16 have rims 26, 28 of enlarged cross section compared to a middle 15 region of the housing 16. The rim 26 accommodates evenly spaced threaded bores 27 for receipt of respective screw fasteners 30 which attach the closure 18 to the housing 16. Additionally, a spring washer 32 and a flat washer 34 is provided with each screw fastener 30. The closure 18 is provided with spaced apertures 36 which align with the apertures in the housing 16 and allow passage of the screw fasteners 30. 20 The bottom rim 28 of the housing 16 is provided with a annular recess 38 having its opening facing downwardly, with an constant cross-section which provides a narrower throat and a wider base. The annular recess 38 receives an O-ring 40. The narrow throat of the O-ring 40 maintains the O-ring 40 in position. The O-ring 40 will protrude beyond the annular recess 38 and provide a cushion as the lid comes into 25 contact with the base plate 20 of the housing 16. The O-ring is made of elastomeric material. The magnetic component 22 is made up of a rare-earth magnet 42, keeper plate 44 and a magnet holder 46. 7 The keeper plate 44 is constructed of ferromagnetic material such as mild steel and this maintains the keeper plate 44 attached to the rare-earth magnet 42. The keeper plate 44 includes two diametrically opposed apertures 45 which are threaded for receipt of screws 47. The screws 47 pass through apertures 50 in the magnet holder 5 46, the apertures 50 being aligned with the threaded apertures 48. The screws 47 engage with the threaded apertures 48 to fasten the magnet holder to the keeper plate. The magnet holder 46, the keeper plate 44 and the magnet 42 are thus assembled and moved together as a unit. The magnet holder 46 has a downwardly projecting annular collar 52 which 10 defines a cylindrical recess on the underside of the magnet holder 46. The keeper plate 44 and the rare-earth magnet 42 are received within this cylindrical recess. Thus, the collar 52 provides a shroud around the magnet 42, preventing the magnet 42 from coming into contact with the internal bore of the housing 16. This will prevent the magnet 42, which is harder than the aluminium housing 16 from coming into contact 15 with the internal bore of the housing 16 and accelerating wear. The magnet holder 46, like the housing 16 is made of aluminium. The pneumatic linear actuator 14 includes a high temperature pneumatic cylinder 53 having a piston 54 and a dependant shaft 56. The piston 54 and the dependant shaft 56 move up and down under pneumatic pressure, as will be understood by those 20 skilled in the field. The lower end of the shaft 56 has a threaded bore 58. The keeper plate 44 has an upwardly extending boss 60. The boss 60 is received in a complementarily shaped central aperture 62 of the magnet holder 46. The keeper plate 44 has a central aperture 64, extending through the boss 60. The lower extent of the aperture 64 flares outwardly in the downward direction to provide a seat for the 25 countersink screw 66. The countersink screw 66 seats in the flared part of aperture 64 and is screwed into the threaded bore 58 in the shaft 56. Because the keeper plate 44 is seated in the magnet holder 46, the bottom of the shaft 56 abuts against the boss 60 in the keeper plate 44. The closure 18 for the receptacle 12 is provided with a central aperture 68 which 30 receives the shaft 56 and provides a guide for the up and down motion of the shaft 56. The top of the closure 18 has a complementary profile to the underside of the cylinder 8 53, enabling the cylinder 53 to be seated on top of the lid. The cylinder 53 and the lid 18 are securely fastened together. In order to move the linear actuator14 and the receptacle 12 into position as required, a post 70 is mounted to the top of the linear actuator 14. The post 70 may be 5 received within the grip of a robot arm, for example, to remove the lid from a bread tin over to a stacking position. The post 70 is mounted to the top of the linear actuator as follows. Firstly, a post mounting plate 72 is provided. The post mounting plate 72 is made of stainless steel. The post mounting plate 72 is of square shape in plan as shown in Figure 7a and 10 includes four mounting apertures 74 near the corners. The mounting apertures each receives a socket cap head screw 76 which extends through spring washer 78. The lower end of the screw 76 is threaded to engage with a correspondingly threaded aperture 77 in the closure 18. The post mounting plate 72 is provided with a central aperture 80 having a countersunk face 82 to receive a countersink screw 84. The 15 screw 84 is received within a threaded bore 86 on the post 70. The post 70 is thus secured to the top of the linear actuator 14. The foregoing describes only one embodiment of the present invention and modifications may be made thereto without departing from the scope of the invention. It will be understood that the invention disclosed and defined in this specification 20 extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. 9

Claims (5)

1. A magnetic lifter for lifting a target object having a relatively high magnetic susceptibility, the magnetic lifter including: a body; 5 a magnetic component received within the body; the body having a spacer at one end to space the magnetic component from the target object; the magnetic component being driven between: an operative position on one side of the spacer, such that the magnetic 10 force of the magnetic component attracts the target object against the other side of the spacer; and an inoperative position spaced from the spacer such that the magnetic force on the target object is reduced to release the target object, wherein the magnetic component is connected to a driver providing a 15 mechanical force to move the magnetic component from the operative to the inoperative position.

2. A method of lifting a lid of an oven tin wherein the lid has a high degree of magnetic susceptibility, the method including: providing a magnetic lifter which includes a magnetic component received within 20 a body having a spacer at one end, wherein the magnetic component is connected to a driver providing a mechanical force to move the magnetic component; driving the magnetic component to an operative position within the body, on one side of the spacer to attract and attach the lid to the other side of the spacer; driving the magnetic component to an inoperative position spaced from the 25 spacer, to reduce the magnetic force on the lid and thereby release the lid. 10

3. The lifter as claimed in claim 1 or the method as claimed in claim 2 wherein the driver is a linear actuator substantially external to the body, the linear actuator having a shaft projecting into the body for physical connection to the magnetic component. 5

4. The lifter or method as claimed in claim 3, wherein the body comprises a receptacle or housing and the spacer forms one wall of the receptacle or housing, with the shaft of the linear actuator extending through an aperture provided in a wall of the receptacle or housing opposite the spacer.

5. The lifter or method as claimed in any one of the preceding claims, 10 wherein the magnetic component includes a magnet, a keeper plate and a magnet holder, the keeper plate having high magnetic susceptibility to provide the connection between the keeper plate and the magnet and the magnet holder having low magnetic susceptibility and surrounding the magnet. 11