Patent Publication Number: US-2019170201-A1

Title: Rotational Coupling Device Having Means for Sealing the Interface Between the Armature and the Electromagnet

Description:
BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     This disclosure relates to a rotational coupling device such as a brake. In particular, the instant disclosure relates to a rotational coupling device having means for sealing an interface between an armature and an electromagnet of the rotational coupling device. 
     b. Background Art 
     One conventional type of rotational coupling device used in industrial applications comprises a spring-set, electromagnetically released brake. In such a brake, a rotor or friction disc is coupled to a rotating member. Springs bias a non-rotating armature into engagement with the rotor, trapping the rotor against a brake plate, in order to engage the brake. An electromagnet is then used to create an electromagnetic circuit to draw the armature away from the rotor when it is desired to disengage the brake. 
     The above-described brakes work well for their intended purpose. The brakes have drawbacks, however. Dust and other particulate matter often accumulates in the interface between the armature and the electromagnet. The particulate matter can cause damage to the surfaces of the armature and electromagnet and weaken the electromagnetic circuit thereby reducing the operational life of the brake. 
     The inventor herein has recognized a need for a rotational coupling device that will minimize and/or eliminate one or more of the above-identified deficiencies. 
     BRIEF SUMMARY OF THE INVENTION 
     A rotational coupling device is provided. In particular, a rotational coupling device is provided having means for sealing the interface between the armature and the electromagnet. 
     A rotational coupling device in accordance with one embodiment of the invention includes a rotor configured for rotation about a rotational axis. The device further includes a brake plate disposed on a first axial side of the rotor and an armature disposed on a second axial side of the rotor opposite the brake plate. The device further includes an electromagnet disposed on one axial side of the armature opposite the rotor and the brake plate. The device further includes a spacer disposed axially between the brake plate and the electromagnet and radially outwardly of the rotor and the armature. The device further includes a seal supported on a radially inner surface of the spacer radially outward of the armature. 
     A rotational coupling device in accordance with another embodiment of the invention includes a rotor configured for rotation about a rotational axis. The device further includes a brake plate disposed on a first axial side of the rotor and an armature disposed on a second axial side of the rotor opposite the brake plate. The device further includes an electromagnet disposed on one axial side of the armature opposite the rotor and the brake plate. The device further includes a spacer disposed axially between the brake plate and the electromagnet and radially outwardly of the rotor and the armature. The device further includes means, supported on a radially inner surface of the spacer, for sealing an interface between the armature and the electromagnet. 
     A rotational coupling device in accordance with the present teachings is advantageous relative to conventional devices. In particular, the inventive device provides a relatively inexpensive and less complex means for sealing the interface between the armature and electromagnet in the device in such a way that the accumulation of dust and other particular matter in the interface is minimized. As a result, the operational life of the device is extended relative to conventional devices. 
     The foregoing and other aspects, features, details, utilities, and advantages of the invention will be apparent from reading the following detailed description and claims, and from reviewing the accompanying drawings illustrating features of this invention by way of example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rotational coupling device in accordance with one embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a rotational coupling device in accordance with one embodiment of the present invention. 
         FIG. 3  is a plan view of a portion of the device of  FIGS. 1-2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views,  FIG. 1-2  illustrate one embodiment of a rotational coupling device  10 . In the illustrated embodiment, device  10  provides a braking torque to a rotating body such as a shaft, gear, pulley, blade, etc. in order to slow or halt rotation of the rotating body. It will be understood by those of ordinary skill in the art that device  10  could also be may be used in a wide variety of industrial and other applications requiring a brake. Device  10  may include a rotor  12 , a brake plate  14 , an armature  16 , springs  18 , an electromagnet  20 , a spacer  22  and means, such as seal  24 , for sealing an interface between armature  16  and electromagnet  18 . 
     Rotor  12  is provided to transmit a braking torque to a shaft or other rotating body. Rotor  12  may be made from conventional metals or plastics and may be made by stamping, molding and/or machining. Rotor  12  may be annular in shape and disposed about, and centered about, a rotational axis  26 . Rotor  12  is coupled to, and configured for rotation with, a shaft (not shown) about axis  26  and may be rotationally coupled to the shaft in a variety of ways that permit axial movement of rotor  12  relative to the shaft to enable proper operation of device  10  and account for wear, vibration, runout or thermal expansion. For example, the radially inner surface of rotor  12  and the radially outer surface of the shaft may have complementary, torque transmitting, shapes such as splines (as shown in the illustrated embodiment), a key and keyway, single or double D-shape or hexagonal shape. Rotor  12  includes friction surfaces on opposed sides  28 ,  30  configured to engage brake plate  14  and armature  16 , respectively, during application or engagement of the brake. 
     Brake plate  14  is configured to engage rotor  12  during application of the brake to transmit a braking torque to rotor  12 . Brake plate  14  provides a reaction surface against which armature  16  presses rotor  12  during application of the brake. Brake plate  14  may be made from conventional metals or plastics and may be made from steel (including stainless steel) in some embodiments. Brake plate  14  is disposed on side  28  of rotor  12 . Brake plate  14  may further be disposed about, and centered about, axis  26 . Brake plate  14  is fixed against rotation and may be coupled to electromagnet  20  using a plurality of axially extending fasteners  31  such as bolts, pin, screws or the like as described in greater detail below. 
     Armature  16  is also configured to engage rotor  12  during application of the brake to transmit a braking torque to rotor  12 . Armature  16  may be made from metals or metal alloys or other materials having relatively low magnetic reluctance such as iron or steel. Armature  16  is disposed on side  30  of rotor  12 . Armature  16  may further be disposed about, and centered about, axis  26 . Armature  16  is fixed against rotation, but is axially movable towards and away from rotor  12  and brake plate  14  to permit engagement and disengagement of the brake. Armature  16  may include a plurality of bores extending through armature  16  or a plurality of recesses in the radially outer surface of armature  16  configured to permit fasteners  31  connecting brake plate  12  and electromagnet  20  to pass through armature  16 . In this manner, the fasteners  31  limit or prevent rotation of armature  16  about axis  26 , but armature  16  is permitted to move along axis  26 . 
     Springs  18  provide a means for biasing armature  16  in one direction along axis  26  towards rotor  12  and brake plate  14  to engage the brake. Springs  18  may be disposed between electromagnet  20  and armature  16 . It should be understood that device  10  may include either a single annular spring  18  or a plurality of springs  18  disposed in an annular array about axis  26 . In the latter case, springs  18  may be spaced equally circumferentially spaced about axis  26 . 
     Electromagnet  20  provides a means for urging armature  16  in the opposite direction along axis  26  away from rotor  12  and brake plate  14  to disengage the brake. Electromagnet  20  may include a field shell  32  and a conductor  34 . Field shell  32  houses conductor  34  and may also provide structural support and orient other components of device  10  including brake plate  14  and springs  18 . Field shell  32  may be annular in shape and disposed about, and centered about, axis  26  and may be disposed on a side of armature  16  opposite rotor  12 . Field shell  32  may be made from materials having a relatively low magnetic reluctance such as ferromagnetic materials. Field shell  32  may define a radially extending end wall  36  and axially extending, radially aligned, inner and outer walls  38 ,  40  that extend axially from end wall  36  towards armature  16 . Outer wall  40  may define one or more closed bores  42  configured to receive one end of each spring  18 . Outer wall  40  may also define one or more closed bores (not shown) configured to receive fasteners  31  coupling brake plate  14 , electromagnet  20  and spacer  22 . Conductor  34  may comprise a conventional wound coil or similar conductor and is configured to be received within field shell  32  between walls  38 ,  40 . Current supplied to conductor  34  creates an electromagnetic circuit that includes armature  16  and field shell  32 . The electromagnetic circuit urges armature  16  towards field shell  32  and away from rotor  12  against the force of springs  18  to disengage the brake. 
     Spacer  22  is provided to positon and orient brake plate  14  and electromagnet  20  relative to one another and to define, together with brake plate  14  and electromagnet  20 , an enclosed space containing rotor  12  and armature  16 . In accordance with one aspect of the present teachings, spacer  22  is further configured to support seal  24 . Spacer  22  may be made from conventional materials including metals, such as aluminum, or plastics that are non-magnetic or have a relatively high magnetic reluctance. Referring to  FIG. 3 , spacer  22  is annular in shape and may comprise a unitary (i.e., one-piece) body. Spacer  22  may include a plurality of equally circumferentially spaced, radially inwardly extending flanges  44 . Each flange  44  may define a fastener bore  46  aligned with corresponding bores in brake plate  14  and field shell  32  of electromagnet  20  and configured to receive a corresponding fastener  31  extending through brake plate  14 , spacer  22  and field shell  32  of electromagnet  20  in order to couple brake plate  14 , spacer  22  and field shell  32  together. Referring again to  FIG. 2 , upon assembly, spacer  22  is disposed radially outwardly of rotor  12  and armature  16  with one axial end of spacer  22  abutting brake plate  14  and an opposite axial end abutting field shell  32 . 
     Seal  24  provides a means for sealing the interface between armature  16  and electromagnet  20 . Seal  24  may comprise a fabric woven from a plurality of fibers. In accordance with certain aspects of the present teachings, the fibers may comprise synthetic fibers and, in particular, aromatic polyamide (or “aramid”) fibers. Seal  24  may comprise an annular, unitary (one-piece) body in some embodiments. Alternatively, seal  24  may comprise a plurality of separate, circumferential segments. In this case, the segments may have a circumferential length such that each circumferential end terminates adjacent to a corresponding flange  44 . Seal  24  is supported on, and carried by, spacer  22 . Seal  24  may be disposed on, and bonded to, a radially inner surface of spacer  22  using conventional adhesives. Upon assembly, seal  24  is disposed radially outwardly of rotor  12  and armature  16  and seal  24  extends across the axial length of spacer  22  such that one axial end of seal  24  abuts brake plate  12  and an opposite axial end of spacer  24  abuts field shell  32  of electromagnet  20 . During operation of device  10 , seal  24  contains dust and other particulates on one side of armature  16  facing rotor  12 . Seal  24  prevents particulates from reaching the opposite side of armature  16  facing electromagnet  20  to prevent particulates from reaching the interface between armature  16  and electromagnet  20 . In this manner, buildup of particulates at the interface and damage to the engagement surfaces of armature  16  and electromagnet  20  is reduced thereby allowing maintenance of the strength of the electromagnetic circuit and prolonging the operational life of device  10 . 
     A rotational coupling device  10  in accordance with the present teachings is advantageous relative to conventional devices. In particular, the inventive device  10  provides a relatively inexpensive and less complex means for sealing the interface between the armature  16  and electromagnet  20  in device  10  in such a way that the accumulation of dust and other particular matter in the interface is minimized. As a result, the operational life of device  10  is extended relative to conventional devices 
     While the invention has been shown and described with reference to one or more particular embodiments thereof, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.