JPH05202947A - Torque-restrictive joint - Google Patents

Abstract

PURPOSE: To provide a magnetically activated torque limit joint which can quickly and easily adjust the maximum transmittable torque and transmit torque larger compared to given physical dimensions. CONSTITUTION: A cylindrical body 16 connected to an input drive shaft 11 is formed of a magnetizable material resistant against magnetizing condition in magnetization. A first hollow cylindrical output drive member 21 is concentrically supported around the cylindrical body 16 so as to be rotatable around the cylindrical body 16. A second output drive member 24 is connected to the first output drive member 21 so as to be extended concentrically in the cylindrical body 16. Plural pairs of magnets 40, 41 are fixed to the first and second output drive members 21, 24 to make a magnetic field generated around the cylindrical body 16. When the input drive shaft 11 and the cylindrical body 16 are rotated, torque to rotate the first and second output drive members 21, 24 together is generated. The first and second output drive members 21, 24 are rotated to enable the relative positions to be changed and accordingly the intensity of the magnetic field generated thereby can be also changed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention generally relates to a magnetically actuated torque limiting joint (tor) having adjustment means for adjusting the maximum amount of torque that can be transmitted, particularly through a coupling mechanism.
que limiting coupling).

[0002]

BACKGROUND OF THE INVENTION Torque limiting couplings and clutches suitable for transmitting a limited amount of power from an input member to an output member, typically a rotational torque, are well known devices. Such a joint is characterized in that it is capable of transmitting a predetermined maximum amount of torque through the joint. If the transmitted torque is less than or equal to the maximum torque, the joint can drive the output member to rotate with the input member. However, if you try to exceed the maximum torque, the joint will react and disconnect the input member from the output member. With some joints, once such disengagement is complete, no torque is transmitted through the joint. In other joints, such disengagement is only partial and only a certain maximum amount of torque is transmitted through this joint.

Torque limiting joints are used in a wide variety of machines. For example, such fittings are commonly used in machines for screwing screw caps into bottles and other containers. In this application, the drive shaft of the machine is connected to the input member of the fitting and the screw cap head is connected to the output member. The torque limit of the joint is
Set to specify the maximum amount of torque that can be applied to the screw cap. That is, only a certain amount of torque is applied to these screw caps when they are screwed into the container. When properly screwing the screw cap into the container, the coupling decouples the drive shaft of the machine from the screw cap head to prevent excessive torque from being applied to the screw cap head. This is especially important to prevent damage if the screw cap locks when it is screwed into the container.

Many torque limiting joint structures are known in the art. Some of these known structures use magnets and the principle of magnetic attraction to create a torque limiting connection between the input and output members. However, known magnetically actuated or torque limiting joints cannot be adjusted (the maximum amount of torque cannot be changed) or are difficult to adjust. Also, known joints of this kind can only transmit a relatively small amount of torque through a joint of a given physical size. These limitations are problematic when using the joint in machines where the joint operation is limited and the physical space available for the joint is small.
That is, to provide an improved structure for a magnetically actuated torque limiting joint which is capable of quickly and easily adjusting the maximum amount of torque that can be transmitted and which can transmit a relatively large amount of torque for a given specific size. Is desirable.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to an improved structure for magnetically actuated torque limiting joints. The joint of the present invention comprises an input drive shaft rotatably coupled together with a hollow cylinder. The cylinder is formed of a material that can be magnetized and, when magnetized, resists changes in magnetic conditions. A first hollow cylindrical output drive member is concentrically supported for relative rotation about the cylinder. The second output drive member is connected to the first output drive member and extends concentrically within the cylinder. A plurality of pairs of magnets are fixed to the first and second output driving members so as to generate a magnetic field around the cylindrical body.
When the output drive shaft and the cylinder are rotated, the magnetic field produces a torque which together rotates the first and second output drive members. Therefore, a connecting state with a driving action occurs via this joint. The first and second output drive members can rotate relative to one another to change the relative position of the magnet pairs and thus change the strength of the magnetic field produced thereby.

Various objects and advantages of the present invention will now be described in detail with reference to the preferred embodiments with reference to the accompanying drawings.

[0007]

1 and 2 illustrate a magnetically actuated torque limiting joint 10 according to the present invention. Torque limiting joint 10
Comprises a drive shaft 11 suitable for being connected to any conventional rotary power source (not shown). A key 12 is provided on the drive shaft 11 to facilitate this connection. The drive shaft 11 ends in an enlarged hub portion 13 with an annular groove 14 formed at the end. Further, a plurality of holes 15 extending inward in the radial direction are formed in the hub portion 13 of the drive shaft 11. Each hole 15 extends through a portion of the groove 14.

Hollow drive cylinder
nder) 16 is fixed to the drive shaft 11 so as to rotate therewith. One end of the drive cylinder 16 is housed in a groove 14 formed in the hub portion 13 of the drive shaft 11. The plurality of holes 17 extending in the radial direction are formed in the driving cylinder 1.
It is formed by penetrating one end of 6. The hole 17 in the cylinder is
When one end of the drive cylinder 16 is placed in the groove 14, it is aligned with the hole 15 in the hub portion. The drive cylinder 16 is fixed to the drive shaft 11 by inserting a plurality of pins 18 through the hole 15 in the hub portion and the hole 17 in the cylinder. Each pin 18 is press fit or otherwise retained within holes 15 and 17 to prevent it from slipping during use.

The torque limiting coupling 10 further comprises an output drive assembly 20 suitable for being coupled to any driven components (not shown). Output drive assembly 20
Comprises a first drive member 21 arranged around the drive shaft 11 and the drive cylinder 16. First drive member 21
Has a hub rotatably supported on the drive shaft 11 by a pair of bearings 22 and 23. Each bearing 22, 23 supports the entire output drive assembly 20 and drive shaft 11 for relative rotation about a common axis. First drive member 21
Further comprises a cylindrical portion extending axially from the hub portion about drive cylinder 16. The first drive member 21 terminates in a radially outwardly extending flange portion located at the end of the torque limiting joint 10 opposite the drive shaft 11.

The output drive assembly 20 further includes a second drive member 24. The second drive member 24 is generally hollow-cylindrical in shape and comprises a portion concentrically arranged within the drive cylinder 16 and the cylindrical portion of the first drive member 21. The second drive member 24 also includes a radially outwardly extending flange portion located at the end of the torque limiting joint 10 opposite the drive shaft 11. That is, the flange portion of the second drive member 24 is located adjacent to the flange portion of the first drive member 21. If desired, a recess may be formed in one of the flange portions to concentrically position the first and second drive members 21, 24. The second drive member 24 is provided on the flange portion of the second drive member 24.
A plurality of peripheral holes 2 to connect the driven parts to the driven parts described above.
6, an internal key 27 or other means is provided.

The first drive member 21 is replaced by the second drive member 2
Means are provided for rotationally coupling together with 4.
In the illustrated embodiment, a pair of mutually facing arcuate groove holes 30 are formed through the flange portion of the first drive member 21. Within each groove 30 are screw fasteners 31
A screw fastener 31 having a washer 32 disposed therein extends through the washer 32 and the slot 30 into a screw hole 33 formed in a flange portion of the second drive member 24. When the screw fastener 31 is loosened, the first and second drive members 2
1, 24 are relatively freely rotatable by the arc formed by the slot 30. But when tightened, the first and second
The drive members 21 and 24 of FIG. 1 are engaged with each other with friction, and such relative rotation is prevented. The purpose of this structure is described below.

As shown in FIG. 3, a plurality of first magnets 40 extending in the axial direction are fixed to the inner surface of the cylindrical portion of the first drive member 21. In the illustrated embodiment, eight such magnets 40 are provided equidistantly spaced from each other around the inner circumference of the first drive member 21. However, if desired, the number may be more or less. The magnet 40 is a conventional one, and its inner surface is magnetized so as to have a predetermined magnetic polarity. In the illustrated embodiment, the inner surface of the magnet 40 is alternately polarized as a magnetic north and south pole around the inner peripheral surface of the first drive member 21.

Similarly, a plurality of second magnets 41 extending in the axial direction are fixed to the outer surface of the cylindrical portion of the second drive member 24. The number of magnets 41 fixed to the second driving member 24 is preferably equal to the number of magnets 40 fixed to the first driving member 21. The outer surface of the second magnet 41 is
The magnet 40 is preferably magnetized so as to have a magnetic polarity opposite to that of the inner surface of the magnet 40. That is, in the illustrated embodiment, the first
The outer surface of the magnet 41 is also poled around the outer perimeter of the second drive member 24 as alternating magnetic north and south poles. The magnets 40 and 41 aligned in the radial direction have the same polarity. That is, the outer north pole magnet 40 is radially aligned with the inner north pole magnet 41 and the outer south pole magnet 40
Align radially with the inner south pole magnet 41. Each magnet 40, 41 may be formed of a rare earth material such as samarium-cobalt or other similar magnetic material.

As described above, the drive cylinder 16 includes a plurality of first magnets 40 [fixed to the first drive member 21] and a plurality of second magnets 41 [second drive member 24]. It is fixed to [] and is concentrically arranged. The drive cylinder 16 is made of a material that can be magnetized and, when magnetized, resists changes in magnetic conditions. Alnico (A
lnico) [Magnet Manufacturers and Producers Association Grade 5]
Is an example of a magnetic hysteresis material that can provide a satisfactory function as the drive cylinder 16.

In operation, each pair of magnets 40, 41 has a first
And a magnetic field passing through the first drive members 21 and 24 and the cylindrical body 16 is generated. These magnetic fields produce magnetic flux (lines of force). Some of them are illustrated as magnetic flux lines 42 and 43 in FIGS. Magnetic flux lines 42 from each outer north pole magnet 40
Extends radially inward into drive cylinder 16, through drive cylinder 16 in one circumferential direction, into radially outwardly adjacent outer south pole magnet 40, and Through the drive member 21 of No. 1, extending in the opposite direction of the circumferential direction,
Return to the outer north pole magnet 40. Similarly, magnetic flux lines 43 from each inner north pole magnet 41 extend radially outward into drive cylinder 16 and extend in one circumferential direction through drive cylinder 16 and radially inward. It extends into the adjacent inner south pole magnet 41 and then in the opposite circumferential direction via the second drive member 24 back to the inner north pole magnet 41. As shown in FIG. 3, the magnets 40 and 41 are included in two magnetic circuits each having the magnets 40 and 41 that are adjacent to each other and have opposite polarities.

Due to the material used in this case, the drive cylinder 16 is magnetized in alignment with the magnetic flux. Such magnetization resists the drive cylinder 16 from being moved relative to each magnet 40, 41 and thus the first and second drive members 21, 24. Therefore, when the drive shaft 11 and the drive cylinder 16 are rotated, the magnetic flux generates a torque that pulls the magnetic field generated by the drive cylinder 16 together with the magnets 40 and 41. Therefore, the first and second drive members 21, 24 rotate together with the drive cylindrical body 16, and the torque limiting joint 10 causes the drive shaft 11 to drive the drive members 21, 24 in a connected state.

The ability of the torque limiting joint 10 to transmit torque therethrough is related to the strength of the magnetic field generated by the magnets 40, 41 and the material used to form the drive cylinder 16. Torque limiting joint 10
To transmit via the drive cylinder 16 and each magnet 4
The magnetic attraction between 0 and 41 is insufficient to maintain the connected state with the driving action. That is, the drive shaft 11 does not rotationally drive the first and second drive members 21 and 24, and the drive members 21 and 24 slide with respect to the drive cylinder 16 when the drive cylinder rotates. Therefore, the torque limiting joint 10
The torque transmitted through does not exceed a predetermined maximum amount.

As is apparent from FIG. 3, the magnets 40 and 41 are
Orient the North Pole and South Pole to be radially aligned with each other. Therefore, the magnetic fluxes 42, 4 passing through the drive cylinder 16
The three paths substantially overlap each other in the eight arcuate sections around the drive cylinder 16 (only two of these overlapping arcuate sections are shown). The density of the magnetic fluxes 42, 43 passing through the drive cylinder 16 in these overlapping arcuate sections [ie the amount of magnetic field lines 42, 43 per unit cross-sectional area of the drive cylinder 16] is the highest. Therefore, the magnetic attraction of the drive cylinder 16 to each pair of magnets 40, 41 is also highest. First and second drive members 21,
This relative position of 24 represents the position where the highest amount of torque can pass through the torque limiting joint 10.

In some cases, it is desirable to adjust the torque limiting joint 10 so that the amount of torque that can pass through it is less than the maximum amount. For that, screw fasteners 3
1 is loosened to release the frictional engagement between the first and second drive members 21, 24. The first drive member 21 is then rotated relative to the second drive member 24 so that the magnets 40, 41 are not radially aligned with each other as shown in FIG. Finally, the screw fastener 31 is tightened again so that a frictional engagement between the first and second drive members 21, 24 again occurs. In this case, the torque limiting joint 10 can operate as described above.

When the first and second drive members 21, 24 are oriented in the radially non-aligned position shown in FIG. 4, the path of the magnetic flux 42, 43 through the drive cylinder 16 is They only partially overlap each other. Therefore, the density of the magnetic fluxes 42, 43 passing through the drive cylinder 16 is smaller than the maximum value, as in the case of magnetic attraction for each pair of magnets 40, 41. Further movement of the magnets 40, 41 from the radial alignment position illustrated in FIG. 3 reduces the amount of torque that can be transmitted through the torque limiting joint 10. The first and second drive members 21, 24 are connected to the outer north pole magnet 40.
The torque limiting joint 10 is adjusted to transfer a minimum amount of torque therethrough when is oriented to radially align with the inner south pole magnet 41 and vice versa.

The main advantage of the joint according to the invention is that the relative rotation of the first and second drive members 21, 24 during torque adjustment
There is no relative movement in the axial direction between these members. Therefore, the overall size of the torque limiting joint 10 can be made extremely small because it is not necessary to provide a space adapted to the relative movement in the axial direction between the first and second drive members 21 and 24. The drive shaft 11 of the torque limiting joint 10 functions as an input member to the torque limiting joint 10, and the drive members 21, 2
Although 4 has been described as functioning as an output member from the torque limiting coupling 10, it is clear that the torque limiting coupling 10 can operate in the opposite mode. That is, the drive member 2
1, 24 can be connected to a rotary power source, and the drive shaft 11 can be connected to a driven component. This means that the first and second
The inertia (as shown in the illustrated embodiment) associated with causing the rotational movement of both drive members 21, 24 of the drive cylinder 1
It is advantageous for some applications because it is greater than the inertia associated with producing a rotational motion of only 6.

Although the principle and mode of operation of the present invention has been described in detail with reference to the preferred embodiments, it is needless to say that the present invention can be modified in various ways without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is an axial cross-sectional view of one embodiment of a magnetically actuated torque limiting joint according to the present invention.

FIG. 2 is an end view of the torque limiting joint of FIG. 1 viewed from the right side.

FIG. 3 is a sectional view taken along line 3-3 of FIG.

4 is a cross-sectional view similar to FIG. 3 showing the first and second drive members in different relative positions so as to vary the maximum amount of torque that can be transmitted through the joint of the present invention.

[Explanation of symbols]

 10 Torque Limiting Joint 11 Drive Shaft 16 Drive Cylindrical Body 21 First Drive Member 24 Second Drive Member 30 Groove Hole 31 Screw Fastener 32 Washer 40, 41 Magnet

Claims (1)

[Claims] 1. A torque limiting joint suitable for connecting a first part to a second part, comprising: a hollow cylinder formed of magnetic hysteresis material and suitable for being connected to said first part; A first driving member that is hollow and that is adapted to be connected to the second part, forming an inner surface disposed around the cylindrical body, and forming an outer surface disposed inside the cylindrical body, and A second drive member suitable for being connected to two parts, a plurality of first magnets fixed around the inner surface of the first drive member, and a plurality of first magnets fixed on the outer surface of the second drive member. A plurality of second magnets fixed around the plurality of second magnets, and a plurality of the second magnets with respect to the plurality of first magnets, with relative axial movement between both of these magnets. So that it can be moved in the circumferential direction without Mounting means for rotatably mounting material to the first drive member; and the first drive member to prevent relative rotation between the first drive member and the second drive member. Limiting means for releasably connecting the second drive member to the torque limiting joint.