Magnetic brake for braking the line spool of a fishing reel
This invention relates to a magnetic brake for inductive braking of the line spool of a fishing reel. 
     Magnetic brakes of this type are used for braking the line spool during casting, thereby to prevent rotation of the line spool at a speed higher than the reeling-out speed of the line, which usually results in backlash and over-running of the spool with consequent tangling of the line. 
     Prior art magnetic brakes comprise permanent magnets which are stationarily mounted outside the line spool but are grouped around the extension of the axis of rotation of the line spool and which brake the line spool by magnetic induction in a part (rotor) rotatable together with the spool spindle. 
     The present invention aims at simplifying and making the construction of prior art inductively operating line spool brakes more efficient. More particularly, the invention aims at providing a line spool brake which requires but little space, which permits the use of a relatively large number of permanent magnets, which operates efficiently in close conjunction to one spool end wall, which is readily adjusted to give the desired braking effect, and which comprises a minimum number of component parts. 
     These objects of the invention are achieved in that the magnetic brake according to the invention has been given the characteristic features stated in claim 1 and, for preferred embodiments, the characteristic features stated in claims 2 and 3. 
    
    
     The invention will be described in more detail in the following, reference being had to the accompanying drawings in which: 
     FIG. 1 shows a stationary outer end wall of the fishing reel, with the adjusting knob for the magnetic brake; 
     FIG. 2 is a fragmentary section of the fishing reel, taken along line II--II in FIG. 1; 
     FIG. 3 is a plan view of the magnet support, showing the magnets mounted in position; and 
     FIG. 4 is a side view of the magnet support which is shown partly in section along line IV--IV in FIG. 3. 
    
    
     The magnetic brake according to the invention, in the embodiment illustrated in the drawings, comprises an annular magnet support which is generally designated 1 and detachably mounted in a circular hollow space which is provided in one end wall 2 of the fishing reel and which is open towards one end wall 4 of the line spool 3. Disposed in the annular support 1 is an annular plate 5 which constitutes a planar bottom plate for a plurality of small cylindrical permanent magnets 6. As will appear from FIGS. 3 and 4, the support has a radially inner ring-shaped wall 1&#39; having a number of circular pockets with segmental walls for partially enclosing the cylindrical permanent magnets 6 and the head of a threaded bolt 7 which has a cylindrical shank portion extending through a sleeve-shaped portion 8 of the support 1 and is displaceably mounted in a sleeve-shaped portion 8&#39; of the outer end wall 2, on the outer side of which the bolt 7, on a threaded end portion 7&#39;, carries an adjusting knob 9. As shown in FIG. 2, the bolt 7 and the support 1 are spring-loaded in a direction inwardly towards the line spool 3, 4 by means of a helical spring 10 inserted between the support 1 and the outer end wall 2. The bolt preferably is secured to the support 1 by friction or in some other manner and is displaceable relative to the sleeve-shaped portion 8&#39;. The adjusting knob 9 which is mounted on the threaded portion of the bolt 7, has an inner flange engaging a planar supporting surface of the outer end wall 2. By turning the knob in one direction, the magnet support 1 can be moved away from the end wall 4 of the line spool 3, and by turning the knob in the opposite direction, the support is returned by the spring towards the line spool. At all times, the support 1 remains essentially parallel to the outer end wall 4. In this manner, the gap 12 between the ends of the permanent magnets 6 and the spool end wall 4, and thus the magnetic force, can be varied while the magnets 6 axially moved in relation to the end wall 4. 
     As is shown in FIG. 4, the small cylindrical magnets 6 are so positioned that every other magnet has its north pole end and every other magnet has its south pole end facing the line spool. According to need, two magnets may be inserted or dispensed with, as is indicated by the dash and dot lines in FIG. 3. Thus, it is possible to use in a magnet support ring a desired number of magnets for different types and sizes of fishing reels, depending on the braking power which is required for braking line spools of different weights. 
     That part of the outer end wall of the fishing reel which is designated 2 in FIG. 1 may be in the form of a detachable cap, and the magnet support ring 1 which preferably is made of plastic, is displaceably guided on the inner side of the cap. The end wall 4 may be made of metal, such as aluminum, or metallised for magnetic inductive cooperation with the magnets. The bottom plate 5 may be made of sheet metal or other magnetic material. The magnets are supported on the plate by their rear ends, and the plate closes the magnetic circuit. If desired, the plastic ring may be formed such that the magnets can be pressed into position in the pockets within the ring where they can be retained by friction and elastic clamping. It is also conceivable to combine these practical methods of securing the magnets in the magnet support. 
     The bottom plate 5 in the support 1 can engage a shoulder on the outer annular wall 1&#34; of the support and can either be glued to the plastic ring or be detachable therefrom. As has been mentioned before, the bottom plate 5 should consist of a metal establishing a magnetic connection between the north and south poles of the magnets, but the bottom plate 5 may also be a plastic plate which for instance, or preferably, is made integral with the plastic ring, in which case the surface of the bottom plate in contact with the magnets should be metallised or carry a magnetically conductive metal disc. 
     The adjusting device is extremely simple in that it comprises but three independently dismountable components: the bolt, the adjusting knob and the spring. Mounting of the bolt only requires a cylindrical bearing surface on the bolt and a corresponding bearing surface in the sleeve-shaped portion of the cap 2 connected to the fishing reel. 
     In the magnetic brake according to the invention, the braking effect is controlled by axial adjustment of the distance of the magnets from the adjacent side of one end wall 4 of the line spool 3. In this manner, the total end area of the magnet poles and the maximum circumference of the line spool end wall 4 can be utilised. The air gap between the magnet poles and the line spool end wall 4 can be adjusted from a minimum which merely requires the line spool to go free from mechanical contact with the magnetic brake, to a maximum at which the brake effect of the magnets by magnetic induction in the line spool end wall 4 is substantially zero. The air gap or clearance can be reduced by means of a flange 4&#39; on the outer circumference of the end wall 4. 
     The adjustment of the magnetic brake can be registered by means of an index marking from 0 to 9 on the adjusting knob and an index point on the end wall cap 2. By providing, for example, a pin and a spring as well as a number of recesses in the cap, a series of stop locations 0, 1, 2 . . . 10 can be established and sensed. 
     As is evident from the above description, the brake according to the invention comprises but a few component parts: the magnet support, i.e. the plastic ring and the bottom plate which consists of a sheet metal ring, the adjusting knob and the adjusting bolt (two components) with bearing surfaces, the sleeve-shaped portion in the cap with its bearing surface for the bolt, the planar bearing surface on the cap for supporting the knob, and the simple cylindrical magnets which may be from five to eight in number. 
     A further advantage is that the magnetic brake according to the invention is readily dismantled. The quickest way of doing this, is to remove the cap which carries the entire brake. The magnet support is readily detached from the cap by unscrewing the knob from the bolt and removing the entire magnet support together with the bolt. This means that the magnetic brake can be mounted without difficulty also by unskilled workers during manufacture of the fishing reel, and that overhaul and maintenance can readily be carried out by the fisherman himself under field conditions. 
     The invention is not restricted to the embodiment described above but can be modified in different ways within the scope of the appended claims.