FR2683405A1 - TORQUE LIMITING COUPLING WITH MAGNETIC OPERATION. - Google Patents

Abstract

A torque limiting coupling capable of connecting a first component to a second component is disclosed. According to the invention, it comprises a hollow cylinder (16) connectable to the first component and formed of a material with magnetic hysteresis, first and second drive members (21, 24) connectable to the second component, the first member being hollow and defining an inner surface around the cylinder, the second defining an outer surface in the cylinder, magnets (40) fixed around the inner surface of the first driver, other magnets fixed around the outer surface of the second drive member, means for mounting the second drive member for rotation relative to the first so that the second magnets can be circumferentially moved relative to the first without relative axial movement between them and means (31) for connecting releasably the first drive member to the second to prevent relative rotation between them. The invention applies in particular to the drive of machines.

Description

This invention relates generally to coupling mechanisms and

  in particular to a magnetically operating torque limiting coupling having means for adjusting the maximum amount of torque

that he can transmit.

  Couplings and torque limiting clutches are well known devices which are adapted to transmit a limited amount of power, typically a torque, from an input member to an output member. Such couplings are characterized by a maximum quantity. predetermined torque they can transmit If the torque transmitted is lower than or equal to the maximum torque, the coupling allows the input member to drive the output member in rotation However, if one tries exceeding the maximum torque, the coupling reacts to disconnect the input member from the output member In some couplings, such

  disconnection is complete with the result that no torque is transmitted.

  In other couplings, this disconnection is only partial, with

  result that only the predetermined maximum amount of torque is transmitted.

  Torque limiting couplings are used in a wide variety of machines. For example, such couplings are commonly used in machines for screwing threaded caps onto bottles and other containers. In this application, a drive shaft of the machine is connected. to the input member of the coupling and a head of positioning of the capsule by screwing it is connected to the output member The torque limit of the coupling is set to define the maximum amount of torque that can be applied to the capsules during the process of placing the capsules by screwing them Thus, only a predetermined amount of torque can be exerted on the capsules when they are screwed on the containers When a capsule is screwed on a container , the coupling disconnects the drive shaft of the machine and the positioning head of the capsule in the

  screwing, thus preventing an excessive amount of torque from being applied to it.

  This is particularly important to prevent degradation if a

  capsule is stuck while screwed to the container.

  Many coupling structures limiting the torque are known.

  Some of these known structures employ magnets and the principles of magnetic attraction to establish the torque-limiting connection between the input and output members. However, the torque limiting couplings

  magnetic operation which are known to be either non-adjustable (i.e.

  ie, the maximum torque can not be changed) or they are difficult to adjust Similarly, known couplings of this type can transmit only a relatively small amount of torque for a given physical dimension of the coupling. These limitations can cause problems when the coupling is used on a machine where access to the coupling is restricted and the physical space available for mating is small. Thus, it would be desirable to provide an improved structure for a torque coupler coupling with magnetic operation where the maximum torque amount can be quickly and easily adjusted and which is capable of transmitting a relatively large amount of torque for a

given physical size.

  The present invention relates to an improved structure of a magnetically operating torque limiting coupling. The coupling comprises an input drive shaft which is connected to a hollow cylinder for rotation with it. The cylinder is formed of a material which is magnetizable and which, when magnetized, withstands changes in its magnetic condition A first cylindrical and hollow output drive member is concentrically journalled around the cylinder for rotation relative thereto A second drive member outlet is connected to the first drive member to extend concentrically into the cylinder Magnet pairs are attached to the first and second drive members to establish magnetic fields around the cylinder When the drive shaft and the cylinder rotate, magnetic fields produce a couple that tends to spin the first and seco As a result, a drive connection is produced by the coupling. The first and second drive members are rotatable relative to one another to change the relative positions of the pairs of magnets and consequently the strength of the magnetic fields thus produced. The invention will be better understood and other purposes, features, details

  and benefits of it will become clearer during the description

  explanatory text which will follow with reference to the accompanying schematic drawings given solely by way of example illustrating several embodiments of the invention and in which: FIG. 1 is an elevational sectional view of a torque limiting clutch coupling; magnetic operation according to the present invention; Figure 2 is an extreme elevational view of the coupling, taken from the right side in Figure 1; Figure 3 is an elevational sectional view of the coupling, taken along line 3-3 of Figure 1; and FIG. 4 is an elevational and sectional view similar to FIG. 3 showing the first and second drive members in a different relative position in order to change the maximum amount of torque that can be

transmitted by the coupling.

  Referring now to the drawings, Figs. 1 and 2 show a magnetically operating torque limiting coupling which is generally indicated at 10, according to the present invention. The coupling 10 includes a drive shaft 11 which is adapted to be connected to any conventional source of rotational energy (not shown) A key 12 is provided on the drive shaft 11 to facilitate this connection. The drive shaft 11 terminates in an enlarged portion of hub 13 having an annular groove 14 which is formed at its end A number of radially inwardly extending bores 15 are also formed in the hub portion 13 of the drive shaft 11 The bores 15 pass through

a portion of the throat 14.

  A hollow drive cylinder 16 is attached to the drive shaft 11 for rotation with it. One end of the drive cylinder 16 is received in the groove 14 which is formed in the hub portion 13 of the drive shaft. 11 Radially extending openings 17 are formed through this end of the drive cylinder 16 The openings 17 of the cylinder are positioned to align with the holes 15 of the hub portion when this end of the cylinder The driver 16 is disposed in the groove 14. Pins 18 are inserted through the holes in the hub portion and the openings 17 of the cylinder to secure the drive cylinder 15 to the drive shaft 11. pressure-fitted or otherwise retained in holes 15 and openings

  17 to prevent their removal during use.

  The coupling 10 further comprises an output drive assembly, generally indicated at 20, which is adapted to be connected to any driven component (not shown). The drive assembly 20 includes a first drive member 21 which is arranged around the drive shaft 11 and the drive cylinder 16 The first drive member 21 comprises a hub portion which is rotatably supported on the drive shaft 11 by two bearings 22 and 23. 23 journall the entire drive assembly 20 and the drive shaft 11 for relative rotation about a common axis The first drive member 21 further includes a cylindrical portion extending axially from the portion The first drive member 21 terminates in a radially outwardly extending flange portion which is located at the end of the hub.

  the coupling 10 opposite to the drive shaft 1.

  The drive assembly 20 further comprises a second drive member 24 The second drive member 24 has a portion which is generally hollow and cylindrical in shape and which is arranged concentrically in the drive roll 16 and the cylindrical portion of the first member The second drive member 24 also includes a radially outwardly extending collar portion which is located at the end of the coupling 10 which is opposite to the drive shaft 11. Thus, the collar portion of the second The drive member 24 is adjacent to the flange portion of the first drive member 21. If desired, a recess may be formed in one of the flange portions (as shown at the second drive member 24) for concentric positioning of the flange portions. first and second members 21 and 24 The flange portion of the second drive member 24 may be be provided with a number of peripheral openings 26, an inner key 27 or other means for its connection to the components carried out

mentioned above.

  Means are provided for connecting the first drive member 21 to the second drive member 24 for common rotation. In the illustrated embodiment, two opposite arcuate slots 30 are formed through the flange portion of the first drive member 21. each of the slots 30 is provided with a threaded fixing means 31 and a washer 32 The threaded fastening means 31 pass through the washers 32 and the slots 30 to respective threaded openings 33 which are formed in the flange portion of the second drive member When the threaded fastening means 31 are loosened, the first and second drive members 21 and 24 are free to rotate relative to one another over the arc defined by the slots 30. However, when they are tight , the first and second drive members 21 and 24 are in friction engagement, which prevents this relative rotational movement The purpose of this tructure will be

explained below.

  As can best be seen in FIG. 3, a first quantity of axially extending magnets 40 is fixed to the inner surface of the cylindrical portion of the first driving member 21 Eight magnets 40 are equidistant on the inner periphery of the first 21, in the embodiment illustrated, although it is possible to provide, if desired, a larger or smaller number The magnets 40 are traditional and they are magnetized so that their inner surface has In the illustrated embodiment, the inner surfaces of the magnets 20 are polarized as alternating north and south magnetic poles on the inner circumference of the first drive member 21. Likewise, a second of axially extending magnets 41 is fixed to the outer surface of the cylindrical portion of the second drive member 24 The number of magnets 41 which are The magnets 41 are preferably magnetized so that their outer surface has a magnetic polarity which is fixed to the second drive member 24 is preferably equal to the number of magnets 40 which are attached to the first drive member 21.

  which is opposed to the magnetic polarity of the internal surfaces of the magnets 40.

  Thus, in the illustrated embodiment, the outer surfaces of the magnets 41 are also polarized as north and south magnetic poles, alternately on the outer circumference of the second entrainment member.

  Each of the radially aligned magnets 40 and 41 is of the same polarity.

  Thus, the north outer magnets 40 are radially aligned with the north inner magnets 41 and the south outer magnets 40 are radially aligned with the south inner magnets 41 The magnets 40 and 41 may be formed of a rare earth material such as cobalt samarium or any other similar magnetic material. As described above, the drive cylinder 16 is arranged concentrically between the first quantity of magnets 40 (which are attached to the first drive member 21) and the second quantity of magnets 41 (which are attached to the second drive member 24) The drive cylinder 16 is formed of a material which is magnetizable and which, when magnetized, withstands changes in magnetic condition. One example is a hysteresis material. which has been found to function satisfactorily as a driving cylinder 16, Alnico (Quality 5 of the

  Magnetic Manufacturers and Producers Association).

  In operation, the pairs of magnets 40 and 41 produce magnetic fields which pass through the first and second drive members 21 and 24 and through the cylinder 16. These magnetic fields produce a magnetic flux (lines of force) of which one part is schematically illustrated at 42 and 43 in FIGS. 3 and 4 The flow lines 42 of each north-side external magnet 40 extend radially inwards in the cylinder 16, circumferentially in a direction through the cylinder 16, radially towards the outside in an adjacent south outer magnet 40 and circumferentially in the opposite direction through the first driving member 21 for a return to the outer north magnet 40 Similarly, the flow lines 43 from each inner north magnet 41 s extend radially outwardly in the cylinder 16, circumferentially in a direction through the cylinder 16, radially inwards in an internal magnet e adjacent south 41 and circumferentially in opposite direction through the second drive member 24 for a return to the inner north magnet 41 As shown in Figure 3, each of the magnets 40 and 41 is involved in two magnetic circuits, one with each of its adjacent magnets and of opposite polarity 40

and 41.

  Given the material used here, the cylinder 16 is magnetized in alignment with the magnetic flux. This magnetization forces the cylinder 16 to resist movement relative to the magnets 40 and 41 and therefore to the first and second drive members 21 and 24. As a result, when the drive shaft 11 and the cylinder 16 are rotated, the magnetic flux produces a torque that pulls the magnetic fields produced by the magnets 40 and 41 with the cylinder 16. As a result, the first and second members 21 and 24 are forced to rotate with the cylinder 16 and a drive connection is provided by the coupling 10 of the shaft

  11 to the driving members 21 and 24.

  The ability of the coupling 10 to transmit the torque is related to the strength of the magnetic fields produced by the magnets 40 and 41 and the material used to form the cylinder 16. If an attempt is made to transmit a greater amount of torque by the coupling 10, the magnetic attraction between the cylinder 16 and the magnets 40 and 41 is insufficient to maintain the drive connection Thus, the drive shaft 1 1 can not rotate the first and second organs of training 21 and 24 On the contrary, the organs

  21 and 24 slide relative to the cylinder 16 while it rotates.

  Consequently, the torque transmitted by the coupling 10 can not exceed the

  predetermined maximum quantity.

  Referring to FIG. 3, it can be seen that the magnets 40 and 41 are oriented so that the north and south poles are radially aligned. As a result, the magnetic flux paths 42 and 43 which pass through the cylinder 16 substantially overlap with each other. eight arcuate segments around the cylinder (only two of these overlapping arcuate segments are shown) The magnetic flux density 42 and 43 passing through the cylinder 16 (i.e., the amount of magnetic lines of force 42 and 43 through As a result, the magnetic attraction of the cylinder 16 to the pairs of magnets 40 and 41 is also at a maximum. This relative position of the first and second members 21 and 24 represents the position at which the maximum amount of torque can

  pass through the coupling 10.

  In some cases, it may be desirable to adjust the coupling 10 so that the amount of torque that can pass through it is smaller than the maximum amount. To accomplish this, the threaded fastening means 31 are loosened to release the clutch. friction engagement between the first and second drive members 21 and 24 Then, the first drive member 21 is rotated relative to the second drive member 24 so that the respective magnets 40 and 41 are not radially aligned. 4 Finally, the threaded fixing means 31 are again tightened in order to reestablish the friction engagement between the first and second drive members 21 and 24. The coupling 10 can then

  operate in the manner described above.

  When the first and second drive members 21 and 24 are oriented at the non-aligned position radially, shown in FIG. 4, the magnetic flux paths 42 and 43 which pass through the cylinder 16 overlap only partially. the magnetic flux 42 and 43 which passes through the cylinder 16 is smaller than the maximum value and it is the same for the magnetic attraction of the cylinder 16 vis-à-vis the pairs of magnets and 41 While the magnets 40 and 41 further away from the radially aligned positions and illustrated in Figure 3, the amount of torque that can be transmitted by the coupling 10 decreases When the first and second drive members 21 and 24 are oriented so that the outer magnets north be radially aligned with the internal magnets south 41 and vice versa,

  the coupling 10 is adjusted to transmit the minimum amount of torque.

  A major advantage of this coupling lies in the fact that the relative rotation of the first and second drive members 21 and 24 during

  the adjustment of the torque does not cause relative axial movement between them.

  As a result, the total size of the coupling 10 is kept to a minimum, since no space must be provided which takes into account the relative axial movement between the first and second drive members 21 and 24. drive 11 of the coupling 10 has been described as functioning as an input to the coupling 10 and that the drive members 21 and 24 have been described as functioning as an output, it will be appreciated that the coupling 10 will function in reverse mode Thus, the drive members 21 and 24 can be connected to the power source of

  rotation and the drive shaft 11 can be connected to the components driven.

  This may be advantageous in some applications because the inertia associated with the rotational movement of the first and second drive members 21 and 24 (as shown in the illustrated embodiment) is more important

  than the inertia associated with the rotational movement of the cylinder 16 alone.

Claims (1)

CLAIM   Torque limiting coupling adapted to connect a first component to a second component characterized in that it comprises: a hollow cylinder (16) connectable to the first component and which is formed of a magnetic hysteresis material, first and second members of driving (21, 24) adapted to be connected to the second component, said first driving member being hollow and defining an inner surface disposed around said cylinder, said second driving member defining an outer surface disposed in said cylinder, a first quantity of magnets (40) fixed around said inner surface of said first driving member, a second quantity of magnets (41) fixed around said outer surface of said second driving member, means (30) for mounting said second driving member for rotation relative to said first drive member so that said second amount of magnet nts can be displaced circumferentially relative to said first quantity of magnets, without relative axial movement therebetween, and means (31) for releasably connecting said first drive member to said second drive member to prevent relative rotation between them.