Abstract:
A grass-cutting head ( 1 ) including: a housing ( 3 ); and at least one spool ( 5 ) placed in the housing and on which a cutting line (F) can be wound. The spool is accessible from the outside to enable a supply of cutting line to be wound onto it without taking said spool out of the housing. A stop is provided to hold the spool in the housing while the supply of cutting line is being wound onto the spool.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a grass-cutting head for brushcutters or similar appliances.  
           [0002]    More specifically, the invention relates to a grass-cutting head of the type that comprises a housing, at least one spool placed in the housing and on which one or more cutting lines can be wound, and a mechanism for feeding the cutting line from the spool to restore the length of the cutting line projecting from the housing following wear due to the use of the head, and in which the feed mechanism includes a spring-action member.  
         BACKGROUND OF THE INVENTION  
         [0003]    Heads of the kind indicated above are widely used in this sphere. Examples of this kind of head are disclosed in U.S. Pat. No. 5,095,688, U.S. Pat. No. 4,823,465, U.S. Pat. No. 4,893,410, U.S. Pat. No. 4,882,843, U.S. Pat. No. 4,274,201, U.S. Pat. No. 4,584,771 and U.S. Pat. No. 4,524,515.  
           [0004]    All these heads possess systems for lengthening the line (i.e. a feed mechanism) with spring-action members which act on a moveable slider or directly on the spool.  
           [0005]    When the line wound on the spool is exhausted owing to having been repeatedly lengthened to restore the length of line projecting from the head, it becomes necessary to open the housing and remove the spool in order to wind a new supply of line onto it. This operation is very difficult because of the presence of the spring-action member which, as soon as the housing is opened, ejects the actuating slider used to lengthen the line, or ejects the winding spool. Afterward, closing the head is a complicated and trying operation. Even the winding of the line onto the spool is a trying and problematic operation, as the turns of cutting line tend to overlap during winding. This leads to jamming later, when the cutting line is being fed out during use.  
         SUMMARY AND OBJECTS OF THE INVENTION  
         [0006]    It is an object of the present invention to provide a grass-cutting head that does not exhibit the drawbacks of conventional heads. More specifically, it is an object of the present invention to provide a grass-cutting head that will make the winding of a supply of line onto the spool an easy process.  
           [0007]    Basically, according to the invention the head is so configured that the spool is accessible from the outside to enable a supply of cutting line to be wound onto it without taking the spool out of the housing, means being provided to hold the spool in the head when the latter is opened to make the spool accessible for reloading of the line. During winding, the cutting line is advantageously passed through the feed bushings, in the opposite direction to the normal direction of feed during use.  
           [0008]    Particular advantages are achieved when the grass-cutting head possesses a cutting line feed mechanism of the type comprising a spring-action member. In this version, retention members prevent the spring-action member and/or the spool which the latter acts upon and/or other parts of the feed mechanism from escaping from the housing in the head when the head is opened to insert the ends of the supply of line into the spool.  
           [0009]    It thus becomes possible to load the cutting line into the spool while keeping the latter in its seat inside the head, avoiding the need to remove and refit the spool and/or parts of the feed mechanism thereof. Besides the advantage of an easier and quicker reloading operation, the line is wound more evenly onto the spool, without overlapping of the turns, as the line is correctly guided by the feed bushings of the head during winding of the line.  
           [0010]    In an especially advantageous embodiment, the retention members comprise anti-rotation means that allow manual rotation of the spool in the line winding direction so that the supply of cutting line is wound onto it, and that prevent or otherwise obstruct spontaneous rotation of the spool in the line unwinding direction. These anti-rotation means facilitate the winding of the supply of line onto the spool.  
           [0011]    In one possible embodiment, the grass-cutting head comprises a feed mechanism that has stop teeth integral with the spool and arresting stops engaging with said teeth to define angularly offset positions of said spool. An actuating slider is provided to cause an angular step by step rotation of the spool inside the housing in the cutting line unwinding direction when the head is spinning. The action of the actuating slider is opposed by the spring-action member, which forms a slider return means.  
           [0012]    The feed mechanism may also be of the automatic type.  
           [0013]    The slider can act on an axially moveable spool that carries two series of stop teeth which engage with corresponding stops or groups of stops integral with the housing. Alternatively, in a different embodiment, the stop teeth may again be integral with the spool, which however is situated in a fixed axial position, while the stop teeth engage with a moveable slider comprising the stops that engage with the teeth on the spool.  
           [0014]    In this version the housing may comprise a first portion through which there extends an axial hub that transmits the rotary drive to the grass-cutting head. Inside this housing portion is the spool from which the line is fed through bushings in the circumferential wall of the housing portion. A support is also provided for the spool mounted on the axial hub and elastically pressed against the first housing portion. The support retains the spool inside the housing. Said support possesses axially elongate openings through which pass the moveable stops carried by the actuating slider. The moveable stops engage with the teeth on the spool. An annular cover is also provided in order to close the housing around the spool support.  
           [0015]    The spool support may comprise, in an especially advantageous embodiment, end teeth engaging with the corresponding end teeth on the housing portion, thus forming anti-rotation means which prevent or obstruct spontaneous rotation of the spool in the unwinding direction. The teeth may be shaped so as to allow rotation of the spool support in the winding direction and prevent rotation in the opposite direction. As an alternative to the two sets of end teeth, inserts made of friction material may be used to increase the coefficient of friction.  
           [0016]    In a different embodiment, the spool is axially moveable under the action of an actuating slider, against which the spring-action member of the line feed mechanism acts. When pushed by the spring-action member, which also acts on the spool, the latter is held against the retention members which in this case are integral with the housing. The anti-rotation means that prevent or otherwise obstruct rotation of the spool in the cutting line unwinding direction may be arranged between the spool and the retention members.  
           [0017]    These anti-rotation means may comprise a layer of friction material or teeth of various shapes.  
           [0018]    The retention members may take various forms, some of which will be described in greater detail with reference to the examples of embodiments illustrated in the appended drawings.  
           [0019]    Other advantageous embodiments and features of the grass-cutting head according to the invention are indicated in the appended dependent claims and will be described in greater detail with the aid of the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    A clearer understanding of the invention will be gained from the description and from the attached drawing, which shows a practical, non-restrictive example of an embodiment of the invention. In the drawing:  
         [0021]    [0021]FIG. 1 shows an axial section through a head in a first embodiment of the invention;  
         [0022]    [0022]FIG. 2 shows a sectioned perspective view of the head shown in FIG. 1;  
         [0023]    [0023]FIGS. 2A and 2B show two perspective views of a head similar to the head of FIGS.  1  and  2 , during the insertion of a supply of cutting line;  
         [0024]    [0024]FIG. 3 shows an axial section through a head in a second embodiment;  
         [0025]    [0025]FIG. 4 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 3;  
         [0026]    [0026]FIG. 5 shows a third embodiment of the head according to the invention in axial section;  
         [0027]    [0027]FIG. 6 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 5;  
         [0028]    [0028]FIG. 7 shows a fourth embodiment of the head according to the invention in axial section;  
         [0029]    [0029]FIG. 8 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 7;  
         [0030]    [0030]FIG. 9 shows an axial section through a modified form of the head shown in FIG. 7;  
         [0031]    [0031]FIG. 10 shows a perspective view, with parts removed, of the head shown in FIG. 9;  
         [0032]    [0032]FIG. 11 shows another embodiment of the head according to the invention in an axial section;  
         [0033]    [0033]FIG. 12 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 11;  
         [0034]    [0034]FIG. 13 shows an embodiment similar to that illustrated in FIG. 11;  
         [0035]    [0035]FIG. 14 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 13;  
         [0036]    [0036]FIG. 15 shows another embodiment of the head according to the invention in an axial section;  
         [0037]    [0037]FIG. 16 shows a cutaway perspective view of the head shown in FIG. 15;  
         [0038]    [0038]FIG. 17 shows an axial view on a different plane of the head shown in FIG. 15;  
         [0039]    [0039]FIG. 18 shows a cutaway perspective view of the head shown in FIGS. 15 through 17, similar to FIG. 16, but in which the spool has been cut through to show the part of the extender mechanism;  
         [0040]    [0040]FIG. 19 shows another embodiment of the head according to the invention in an axial section;  
         [0041]    [0041]FIG. 20 shows a cutaway perspective view of the head shown in FIG. 19;  
         [0042]    [0042]FIG. 21 shows the head shown in FIG. 19 in section on an axial plane taken at a different angle;  
         [0043]    [0043]FIG. 22 shows a cutaway perspective view of the head shown in FIGS. 19 through 21 in a different angle to that of FIG. 20;  
         [0044]    [0044]FIG. 23 shows an axial section through another head according to the invention;  
         [0045]    [0045]FIGS. 24, 25,  26  show cutaway perspective views, at various angles, of the head shown in FIG. 23;  
         [0046]    [0046]FIG. 27 shows an axial section through another embodiment of the head according to the invention;  
         [0047]    [0047]FIG. 28 shows a cutaway perspective view, with parts removed, of the head shown in FIG. 27;  
         [0048]    [0048]FIG. 29 shows an axial section through a modified embodiment of the head shown in FIG. 27;  
         [0049]    [0049]FIG. 30 shows an axial section through another embodiment according to the invention; and  
         [0050]    [0050]FIGS. 31, 32,  33  show cutaway perspective views at various angles of the head shown in FIG. 30.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0051]    A first embodiment of the head according to the invention is illustrated in FIGS. 1 and 2. The head has the general reference  1  and comprises a housing  3  containing a spool  5  on which is wound a cutting line F, depicted as a series of turns in the longitudinal section of FIG. 1.  
         [0052]    The housing  3  has a cylindrical circumferential wall  3 A with bushings  4  through which the cutting line F passes out. Extending axially through the inside of the housing  3  is a hub  7  with a threaded portion  7 A and a hexagonal-section portion  7 B coupled in torsion inside the through seat formed in the housing  3 . The hub  7  is locked to the housing  3  by a journal or stop  9  that screws onto a second threaded portion  7 C of the hub  7  and that has an elastic ring  11 .  
         [0053]    Fitted onto the hub  7 , and journal  9  is a stop component  13  that forms a support for the spool  5 , being provided with a collar  13 A on which the spool  5  sits. The support  13  is held against the housing  3  by a spring-action member consisting of a helical spring  17  housed in a cylindrical seat formed in the support  13 . Inside this cylindrical seat is a moveable actuating slider  19  with projections  19 A that project through longitudinal slots  13 X in the cylindrical wall of the support  13 .  
         [0054]    The projections  19 A form stops acting on two series of teeth  5 A and  5 B which are offset relative to each other angularly and axially inside the through hole of the spool  5 .  
         [0055]    The actuating slider  19  is pushed by the spring-action member  17  against a knob  21  mounted on and retained by the journal  9 .  
         [0056]    The operation of the line feed mechanism, including the actuating slider  19 , with its projections  19 A, the spring action member  17  and the teeth  5 A,  5 B of the spool  5  is similar to that described in U.S. Pat. No. 5,095,688, and will therefore be described only briefly here. Pressing on the knob  21  compresses the spring-action member  17  and therefore moves the actuating slider  19  in such a way that the projections  19 A of the latter disengage from teeth  5 B and engage teeth  5 A, which are offset angularly relative to teeth  5 B. When this actuation is performed with the head  1  turning, the centrifugal force acting on the cutting line F turns the spool  5  until teeth  5 A are stopped by the projections  19 A. Releasing the knob  21  causes the actuating slider  19  to be moved back to the initial position (illustrated in FIGS. 1 and 2) by the spring-action member  17 , with consequent disengagement of teeth  5 A and engagement of teeth  5 B by the projections  19 A as a result of a further angular rotation of the spool  5  due to centrifugal force.  
         [0057]    Each time the knob  21  is pressed, therefore, the spool  5  turns through an angle equal to twice the offset between the teeth  5 A and  5 B.  
         [0058]    Around the collar  13 A supporting the spool  5  is a basically cylindrical closing wall  13 B on which is mounted an annular cover  25 . This cover has an edge  25 A that surrounds the free edge of the circumferential wall  3 A of the housing  3 . The cover  25  may be held in position by its interference with the closing wall  13 B and/or by interference between the edge  25 A and the circumferential wall  3 A, or by means of spring-action projections (not shown in FIGS. 1 and 2).  
         [0059]    During the operation of the head, which for this purpose is fitted to the rotating hub of a brushcutter via the threaded portion  7 A of the hub  7 , and revolved with the lines F projecting from the bushings  4 , the cutting lines F wear away and it therefore becomes necessary to restore the cutting lines projecting from the head  1  to their correct length by depressing the knob  21  and thus operating the actuating slider  19 . After repeated line feed operations, when the line is exhausted, a new supply of cutting line F must be wound onto the spool  5 .  
         [0060]    To do this, it is sufficient to remove the annular cover  25  to give access from below to a pair of anchor holes  5 D for the ends of the cutting line F. The anchor holes  5 D are in line with slots  5 C in the lower flange  5 G of the spool  5 . The initial end of the new supply of line can be passed through the bushings  4  and through the radial slots  5 C to allow the operator to grasp it in the area made accessible by the removal of the annular cover  25 , and then insert it in the corresponding anchor hole  5 D.  
         [0061]    Having secured the ends of the line in the holes  5 D, the operator, by twisting the closing wall  13 B of the spool support  13 , can rotate, in the winding direction, the assembly made up of the button  21 , the actuating slider  19 , the support  13  and the spool  5  around the hub  7  axis. Rotation in the winding direction is permitted by the shaping of sawtooth section end teeth  29  formed on that portion of the support  13  which is pushed against the housing  3 , the latter having complementary teeth, as can be seen in particular in the cutaway view, FIG. 2.  
         [0062]    The reverse rotation between the support  13  and the housing  3  (the direction in which the line in unwound) is not permitted, so that spontaneous rotation in the line unwinding direction is prevented, not only during rewinding of the supply of line but also when the head is in operation. The teeth  29  and the complementary teeth on the housing  3  thus form an anti-rotation means for rotating in a winding direction, but not in an unwinding direction.  
         [0063]    The system of mutual locking between the housing  3 , the support  13  and the knob  21  may differ from this. For example, the central hub  7  may be omitted and the connection may be provided by a system of spring-action fingers. Similarly, the connection between the head and the brushcutter may be provided by a snap-engaging quick-coupling system or the like, of a type known per se, rather than by means of a threaded journal. Similarly, the knob  21  and the actuating slider  19  may be constructed in one piece. The journal  9  may be screwed in by a socket wrench passing through a hole in the knob  21 , or the latter may be coupled in torsion to the journal  9  to enable it to rotate.  
         [0064]    [0064]FIGS. 2A and 2B show a perspective view of a modified housing  3 ′ of a head  1 ′ equivalent to the head shown in FIGS. 1 and 2 in the open condition and show the operation of inserting a new supply of cutting line F. Parts identical or equivalent to those of FIGS. 1 and 2 are indicated by the same reference numbers. The annular cover  25  has been removed to allow access from the outside to the underside of the spool  5 . This spool has slots  5 C′ which are closed off toward the edge of the respective flange of the spool, rather than open as in FIG. 1. Also, the lower flange  5 G′ of the spool  5  is provided on its outermost surface with arcuate projections  5 H to facilitate the winding of the new supply of cutting line F by hand. The knob  21 ′ is made of a smaller diameter than the knob  21  of FIGS. 1 and 2, and a protective membrane  22  is arranged between it and the annular closing wall  13 B of the support  13 .  
         [0065]    Also shown in FIGS. 2A and 2B are spring-action tabs  6  formed integrally with the housing  3 . These are for fastening the annular cover  25  (omitted in FIGS. 2A and 213) in place.  
         [0066]    [0066]FIG. 2A shows the ends Fx of two lengths of cutting line F that have been passed from the outside of the housing  3  in through the bushings  4 . The ends Fx project out through the slots  5 C′ and can therefore be grasped by the user, pulled further to draw more line F through the bushings  4  and then inserted—thereby forming a loop Fy (FIG. 213)—in the anchor holes SD. The line F can then be pulled radially from the outside to take up the loop Fy and then be wound up by turning the spool  5  with the aid of the arcuate projections  5 H.  
         [0067]    [0067]FIGS. 3 and 4 show a different embodiment of the head according to the invention. The head, indicated by the general reference  101 , comprises a housing made up of a main portion  103  and a lower cover  106 . Inside the housing is a spool  105  with two annular flanges  105 X and  105 Y. The spool  105  includes a central through hole through which extends a cylindrical skirt  103 A integral with the portion  103  of the housing. A spring-action component  117  in the form of a helical spring extends between the cylindrical skirt  103 A and the inner wall of the axial through hole of the spool  105 . The spring-action member pushes the spool  105  against a lower slider  119  projecting from the housing cover  106 .  
         [0068]    On the outside of the upper flange  105 X of the spool  105  are a plurality of teeth  124  while on the outside of the lower flange  105 Y are teeth  126  offset angularly relative to the teeth  124 . The shape and the position of the teeth  126  can be seen particularly in FIG. 4 where for greater clarity the cover  106  and its projecting knob  119  have been removed.  
         [0069]    The upper teeth  124  engage with stops defined by fingers  128  formed on the upper wall of the portion  103  of the housing containing the spool  105 , while the lower teeth  126  engage with stops formed by similar fingers on the cover  106 , though these latter fingers are not visible as they are offset at an angle of 90° to the fingers  128 .  
         [0070]    The circumferential wall  10313  contains bushings  104  for the passage of the cutting line wound onto the spool  105 , this line being omitted from the figure for greater clarity.  
         [0071]    To restore the lengths of cutting line projecting from the bushings  104  to their correct length following wear due to operation of the head, pressure is applied to the actuating slider  119 , while the head is turning, causing compression of the spring-action member  117  and therefore axial movement of the spool  105 . This releases the teeth  126  from the lower stops and engages the teeth  124  with the upper stops  128 .  
         [0072]    The angular offset between the teeth  124  and  126  and between their respective stops means that, as the spool  105  is traveling upward, said spool executes a rotary movement and a consequent unwinding of the line. This is caused by the centrifugal force acting on the line itself which continues until the teeth  124  meet the fingers  128 . On releasing the actuating slider  119  the spring-action member  117  returns the spool  105  to the fully down position resulting in a second rotation of one step in the line-unwinding direction. This extender mechanism is known per se.  
         [0073]    Once the supply of cutting line wound on the spool  105  is exhausted it must be replaced. In conventional heads this had to be done by removing the cover  106 , the slider  119  and the spool  105 , which resulted in the spring-action member  117  also escaping. In the head according to the invention, however, the spool  105  is held in place axially by tabs  141  fitted into corresponding slots in the circumferential wall  103 B of the housing portion  103 . The tabs  141  form a stop for the lower surface of the flange  105 X of the spool  105 , preventing the latter escaping when the cover  106  is removed. Removing the cover.  106  and actuating slider  119  gives free access to the underside of the spool  105  to allow a new supply of line to be anchored in anchor holes similar to those marked  5 D in FIGS. 1 and 2 and not shown, for simplicity of the drawing in FIGS. 3 and 4.  
         [0074]    The spool  105  and the spring-action member  117  remain in their positions inside the housing portion  103 . The line is wound in by, for example, pushing the teeth  126  and turning the spool in the winding direction, conveniently indicated by an arrow on the lower face of the flange  105 Y of the spool. To prevent spontaneous unwinding of the spool, the spool is provided with teeth  143  on the lower surface of the upper flange  105 X. The teeth  143  engage with corresponding teeth  145  on the tabs  141 . Operating the spool  105  by hand to turn it in the winding direction exerts sufficient force to cause the teeth  143  to ride over the teeth  145  and thus slightly compress the spring-action member  117 , thus causing the spool  105  to rotate in the winding direction. The resistance presented by the teeth  143 ,  145  and the force of the spring-action member  117  are sufficient to prevent spontaneous unwinding.  
         [0075]    [0075]FIGS. 5 and 6 show an embodiment equivalent to that of FIGS. 3 and 4 and identical parts are indicated by the same reference numbers. Here, the tabs  141  engage with teeth  143  on the lower face of the lower flange  105 Y of the spool  105 .  
         [0076]    [0076]FIGS. 7 and 8 show a variant of the head seen in FIGS. 3 and 4. Identical or corresponding parts are indicated by the same reference number increased by 100. So, for example, the head as a whole has the reference  201  and the housing portion  203 . In this version the spool  205  is held in position, to prevent it from escaping when the cover  206  is opened, by spring-action tabs  241  formed integrally with the wall  203 B of the housing portion  203 . To simplify the drawing, FIG. 8 omits not only the cover  206  and the actuating slider  219  but also the spring-action  5  member  217 .  
         [0077]    Shown in FIGS. 9 and 10 is a variant of the head seen in FIGS. 7 and 8, in which the spring-action tabs  241 , again formed integrally with the wall  203 B of the housing portion  203 , engage with the lower flange  205 Y of the spool  205 , rather than with its upper flange. Parts identical or corresponding to those of FIGS. 7 and 8 are indicated by the same reference numbers.  
         [0078]    In the embodiments shown in FIGS.  3 - 10  the slider  119  or  219  may be formed in one piece with its respective spool  105 ,  205 .  
         [0079]    [0079]FIGS. 11 and 12 show a variant of the head depicted in FIGS. 9 and 10. Identical or corresponding parts are indicated by the same reference numbers increased—by 100 over the numbers given in the embodiment in FIGS. 9 and 10. In this version the lower flange  305 Y of the spool  305  possesses teeth  343  that engage with pegs  341  inserted through the wall  303 D of the housing portion  303 . The pegs  341  have the same function as the tabs  241  and  141  of the earlier embodiments. The line feed mechanism is the same as that described above. The dimensions of the pegs  341  are such as to ensure, in conjunction with the teeth  343 , the anti-rotation action of the spool  305  in order to prevent spontaneous unwinding. The pegs  341  or the tabs  141 ,  241  may also be replaced by other annular retention members built into the internal cylindrical wall of the housing portion of the head.  
         [0080]    [0080]FIGS. 13 and 14 show a variant of the head seen in FIGS. 11 and 12, such that the pegs  341  engage with the upper flange  305 X of the spool  305 , on the underside of which latter are the teeth  343 . Identical numbers indicate parts identical or corresponding to those of FIGS. 11 and 12.  
         [0081]    FIGS.  15 - 18  show, in various cross sections and perspective views, another embodiment of the head according to the invention. The head, designated  401  as a whole, comprises a housing with a main portion  403  that has bushings  404  on its circumferential wall  4038  for the cutting line to be passed from the inside to the outside of the housing. The line is wound onto a spool  405  having flanges  405 X and  405 Y and holes  405 D in which the ends of the cutting line are anchored.  407  denotes a hub comprising a threaded projecting end  407 A for connection to the brushcutter.  407 B denotes a portion of the hub  407  of hexagonal section for transmitting the rotary drive to the head. For this purpose the portion  407 B sits in a seat formed in the portion  403  of the housing.  
         [0082]    The head is closed on the underside by a cover  406  which is fixed to the portion  403  of the housing by spring-action tabs  406 A engaging in windows  403 C in the circumferential wall  403 B of the housing portion  403 . The cover  406  is released by pressing inward from the outside on the spring-action tabs  406 A to disengage them from the windows  403  C.  
         [0083]    The spool  405  is provided with a series of upper teeth  424  and a series of lower teeth  426  which engage with respective stops  428  and  430  on the portion  403  and on the cover  406 , respectively. The teeth  424  and  426  and the stops  428  and  430  are angularly offset to allow the cutting line to be fed out gradually step by step from the spool  405  through the bushings  404  to compensate for line wear. To this end the spool  405  is moved axially so that there is alternate engagement between the teeth  426  and the stops  430  on the one hand, and between the teeth  424  and the stops  428  on the other.  
         [0084]    The axial movement of the spool  405  is brought about by pressure on the actuating slider  419  which pushes the spool  405  up, overcoming the elastic force of the spring-action member  417  which is situated between a collar  403 X (integral with the portion  403  of the housing) and an annular shoulder  405 S on the spool  405 .  
         [0085]    To prevent the spool  405  from escaping from the seat formed by the housing portion  403  when the cover  406  is removed by detaching the spring-action tabs  406 A from the windows  403 C, there is an axial retention member  451  comprising a lower plate  451  A and spring-action tabs  451 E that engage in windows  403 Y formed in the collar  403 X integral with the housing portion  403 .  
         [0086]    The discoidal portion  451  A of the retention member  451  has teeth  451  B engaging with corresponding teeth  405 E on the spool  405 . The teeth  451 B and  405 E form anti-rotation means to prevent spontaneous rotation of the spool  405  in the unwinding direction while a new supply of line is being wound on. This operation takes place as follows. The actuating slider  419  is removed together with the cover  406 , exposing the lower surface of the spool  405 , which is held in place, along with the spring-action member  417 , by the retention members  451 . The new supply of line is passed in from the outside through the bushings  404  and the operator can easily engage the initial end of a length of line in the corresponding hole  405 D formed on the spool. By hand, using the teeth  426  to assist, the user winds a supply of line onto the spool  405  by rotating it in the winding direction. The torque applied by the operator on the spool generates an axial force through the teeth  405 F,  451 B, which overcomes the force of the spring-action member  417 , allowing the teeth  405 E to ride over the teeth  451  B so that the spool  405  rotates in the winding direction. The force of the spring  417  and the shape of the teeth  451  B,  405 E are sufficient to prevent spontaneous rotation in the opposite direction.  
         [0087]    Once the new supply of line has been wound on, the housing can be reclosed by once again fitting on the cover  406  with a snap-action, having first inserted the actuating slider  419  into its central seat in the cover  406 .  
         [0088]    FIGS.  19 - 22  show a modified embodiment of the head seen in FIGS.  15 - 18 . Identical numbers indicate parts identical or corresponding to those of the embodiment seen in FIGS.  15 - 18 .  
         [0089]    The embodiment shown in FIGS.  19 - 22  differs in the different method of anchorage of the retention members  451 , which in this case are fixed to the axial hub  407  which extends down into the lower region of the head, where a screw  408  fastens the retention members  451  consisting of a disk  451  A with the teeth  451  B.  
         [0090]    FIGS.  23 - 26  show a modified embodiment of the head seen in FIGS.  15 - 18 . This embodiment differs from the previous embodiment by having a different design of the retention members  451  of the spool  405 . Identical or corresponding parts are indicated by the same reference numbers as were used in FIGS.  15 - 18 .  
         [0091]    In this embodiment the retention members  451  are held in place by spring-action fingers again marked  451  E in end windows marked  403 Z in the top surface of the housing portion  403 . In this version the seat for the hub  407  is formed in a sleeve  451  C in the retention members  451 , rather than directly on the housing portion  403  as in FIGS.  15 - 18 . The latter portion again has a collar  403 X coaxial with the sleeve  451 C of the retention members  451 , forming a stop for the spring-action member  417  which is housed between this stop and an annular stop formed in the internal through hole of the spool  405 . The retention members  451  again comprise a discoidal terminal portion  451  A that forms end teeth  45   1 B engaging with the teeth  405 E of the spool.  
         [0092]    The retention members  451  may also be formed in one piece with the housing portion  403  and may have spring-action tabs at the lower end for engagement on the spool. This solution is illustrated diagrammatically in FIGS. 27 and 28, where identical numbers denote parts identical or corresponding to those of FIGS.  23 - 26 . The retention members  451  again retain the spool  405  in its position against the action of the spring-action member  417 . They consist in the present case of spring-action tabs extending axially through the inside of the housing portion  403 , and have end teeth engaging with the teeth  405 E of the spool.  
         [0093]    The spool can be removed from the housing by radially compressing the spring-action tabs forming the retention members  451 , whereas in the previous version release was by acting on the tabs  451  E.  
         [0094]    [0094]FIG. 29 shows an embodiment with some slight modifications compared with that of FIGS. 27 and 28. In this version the mutually meshing end teeth on the retention members  451  and on the spool  405 E are replaced by a ring  460  of friction material interposed between the tabs forming the retention members  451  and the lower surface of the spool  405 . This solution, which involves using a friction material rather than a toothed coupling to prevent or hinder spontaneous rotation in the unwinding direction, can also be adopted in the embodiments described earlier.  
         [0095]    FIGS.  30 - 33  show yet another embodiment of the head according to the invention. The head, which bears the general reference  501 , comprises a housing formed largely by a main portion  503  with a circumferential wall  503 B containing outlet bushings  504  for the cutting line which is wound onto a spool  505  housed inside the housing. The spool has flanges  505 X and  505 Y with teeth  524  and  526  projecting outward from the flanges  505 X,  505 Y so as to engage with respective stops  528  and  530 . In this version the stops  530  are formed on the bottom of the housing portion  503 , while the stops  528  are formed on the inner wall of a cover  506  which fits above the housing portion  503  to close the housing. The cover  506  is held in place by spring-action tabs  503 C extending axially along the circumferential wall  503 B of the housing portion  503 .  
         [0096]    Around the circumferential wall  503 B are windows  503 D into which spring-action tabs  561 E belonging to retention members with the general reference  561  engage. These retention members define an annular seat  561 S that runs around an axial sleeve  506 M formed in one piece with the cover  506 . Around the sleeve  506 M is a spring-action member  517  formed by a helical spring which is contained between the seat  561 S and the upper surface of the upper flange  505 X of the spool  505 . The spring-action member  517  thus pushes the spool  505  against an actuating slider  519  projecting down from the housing portion  503 .  
         [0097]    The cover  506  is traversed by a hub  507  with the threaded portion  507 A and a hexagonal-section portion  507 B which is coupled in torsion in a seat of similar cross section formed in the sleeve  506 M of the cover  506 . The threaded portion  507 A of the hub  507  fits onto the brushcutter, and the hub itself transmits the rotation to the head  501 .  
         [0098]    As in the previous versions, the cutting line is fed by pressing the actuating slider  519  in so that it overcomes the force of the spring-action member  517  and displaces the spool  505  axially to bring the teeth  524  and  526  into engagement alternately with the stops  528  and  530 , respectively. The angular offset between the teeth  524 ,  526  and the stops  528 ,  530  allows the spool  505  to rotate in steps under the impulse of centrifugal force when the head  501  is spinning, thus giving a gradual lengthening of the cutting line. When the latter is exhausted a new supply of cutting line can be inserted into the spool  505  without removing the spring-action member  517  and said spool, simply by removing the cover  506  by applying pressure to the two spring-action tabs  503 C. This allows access from the outside to the upper part of the spool  505  so that the user can insert the initial end of a new supply of line from the outside through the bushings  504  and anchor this end of the line to the spool, for example by pushing it into the holes  505 D as shown in FIG. 30. Winding is by rotating the spool in the winding direction.  
         [0099]    Rotation is permitted because the lower teeth  526  are sloping on one side as shown at  526 X in FIG. 32. This allows the teeth  526  to ride over the stops  530  when a torque is applied to the spool  505  in the winding direction. Spontaneous rotation in the cutting line unwinding direction is prevented by the surfaces of the teeth  526  parallel to the axis of the head, which butts against the stops  530 .  
         [0100]    If it is wished to strip the head completely, all that is required is to push the spring-action tabs  561 E in out of the windows  503 D of the housing portion  503 .  
         [0101]    It will be understood that the drawing shows only an example purely as a practical demonstration of the invention, which invention can be varied in its shapes and arrangements without however departing from the scope of the concept on which the invention is based.