Patent Publication Number: US-7581322-B2

Title: Trimmer head for use in flexible line rotary trimmers having improved line loading mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part of U.S. application Ser. No. 11/133,404, filed May 19, 2005, now U.S. Pat. No. 7,513,046 entitled “Trimmer Head for Use in Flexible Line Rotary Trimmers Having Improved Line Loading Mechanism,” which is a continuation-in-part of Ser. No. 10/933,486 filed Sep. 3, 2004, U.S. Pat. No. 7,275,324, issued Oct. 2, 2007, entitled “Trimmer Head for Use in Flexible Line Rotary Trimmers Having Improved Line Loading Mechanism,” which is a continuation-in-part of Ser. No. 10/677,700 filed Oct. 2, 2003, U.S. Pat. No. 6,901,667, issued Jun. 7, 2005, entitled “Trimmer Head for Use in Flexible Line Rotary Trimmers.” 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an improved trimmer head for use in flexible line rotary trimming devices used to trim grass, weeds and other vegetation. More particularly, the invention is directed to an improvement in the line loading of both “bump-feed” type trimmer heads such as those disclosed in U.S. Pat Nos. 4,458,419 and 4,959,904 and the more simple manually operated heads such as that disclosed in U.S. Pat. No. 4,145,809, the contents of said patents being incorporated herein by reference as though fully set forth below. 
   Trimmer heads used in flexible line rotary trimmers generally carry one or two lengths of flexible nylon cutting line wrapped about an interior spool with the ends of the line or lines projecting outwardly through opposed apertures in the side wall of the trimmer head. The head is threadably mounted on the end of an elongated shaft and rotated at a high velocity by a gas or electric motor so that the ends of the cutting line project radially from the head and sever weeds or other vegetation. When cutting line projecting from the head breaks off or becomes overly worn, it must be severed and fresh line extended from the spool through the line outlet eyelets in the side of the housing. Bump-feed type heads include a line feed-out mechanism which responds to a bump on the ground intentionally applied by the operator to feed out a measured length of fresh cutting line which is typically cut to the desired length by a knife blade projecting from a shield attached to the trimmer above the cutting head and spaced a predetermined distance from the perimeter of the trimmer head housing. Manual heads do not include any such line feed-out mechanism. A fastening nut that holds the housing portion of the trimmer head to the spool must be loosened so that the spool can be separated from the housing and manually rotated relative to the housing to pay out additional cutting line. The spool and housing are then re-secured by the fastening member. 
   In both bump-feed and manual heads, the length or lengths of cutting line are typically wound onto the spool by hand. As most cutting heads employ two lengths of line projecting from opposed sides of the cutting head, care must be taken during the winding of the spool to avoid crossing or otherwise tangling of the two lines within the spool which interferes with the paying out of fresh line. This is particularly important in bump-feed heads where centrifugal force is utilized to pull the new lengths of line from the spool during use as the head is being bumped against the ground as any line tangle will interfere with the proper feeding of the line. Difficulty in properly loading the line on the spool is the most common complaint of home users of flexible line trimmers. It also is a time consuming task for the professional user. 
   The early bump-feed mechanisms typically consisted of a dog or friction clutch located between the spool of line and the surrounding housing. By bumping an extension of the spool on the ground, or other fixed object, the friction clutch was temporarily disengaged for a length of time dependant on the duration of the bump. The dog clutch released by the bump then abruptly engaged at the next opportunity to feed out line in segment lengths which were related to the engagement points of the dog clutch. Such dog clutches had outwardly extending ribs which engaged inwardly extending abutment tangs and therefore depended upon a skillful bump when it was desired to deliver only one segment length. However, friction within such devices and overzealous bumping often resulted in two or more line segments being fed out, particularly especially when the device has been in use and the corners on the ribs and tangs became worn such that positive engagement was no longer assured. The unavoidable abrupt operation of the dog clutch caused such wear to occur. 
   A bump-feed-out mechanism was subsequently developed that automatically fed out a predetermined length of line with each bump, regardless of the duration of the bump, and which did not lose this ability with extended use. That device is disclosed in and is the subject of the incorporated reference, U.S. Pat. No. 4,458,419. As described therein in detail, the improved trimmer head contained a spool holding one or more coils of cutting line and a simplified mechanism that selectively allowed relative movement of the spool with respect to the housing in response to bumping of the head on the ground to pay out measured lengths of line. The simplified pay-out mechanism included a novel spring-loaded cam and cam follower arrangement in which the cam follower included two pair of diametrically opposed and generally inwardly facing abutment surfaces arrayed about the axis of rotation of the trimmer housing. The abutment surfaces were thus spaced 90° apart and were carried by a depending cylindrical wall that circumscribed an interior chamber. The cam member was disposed within the chamber in threaded engagement with the extended lower end of the drive bolt of the trimmer housing and defined two vertically adjacent cams, each cam being of a square configuration and defining four perpendicularly disposed cam surfaces adapted to engage the abutment surfaces on the cam follower. The upper cam was rotationally offset 45° from the lower cam. 
   In operation, the housing was rotationally driven by the drive bolt through a connection between the upper end of the bolt and the trimmer drive means. The housing and cam member was thus driven by the drive bolt, which in turn drove the cam follower and the spool mounted thereon due to the engagement between the cam surfaces on the cam member and the abutment surfaces on the cam follower. The line carrying spool was disposed about the cylindrical wall of the cam follower and attached thereto via a pair of opposed outwardly projecting studs on the cam follower member that extend into slots formed in the inner portion of the spool. The spool was provided with a bumper at its lower end such that when the bumper was pressed against or bumped on the ground, the housing moved downwardly with respect to the spool against the force of a spring, disengaged the lower cam from the abutment surfaces on the cam follower and allowed the cam member to rotate 45° relative to the cam follower, whereupon the cam surfaces of the upper cam would abut the abutment surfaces on the cam follower. That imparted a similar degree of relative rotation between the spool and the housing. Once the force of the bump was dissipated, the spring loading forced the spool and housing back to their relative positions, which released the cam surfaces on the upper cam from the cam follower abutment surfaces and allowed another 45° of relative rotation of the cam member and cam follower and thus of the spool and housing, for a total of 90° of rotation per bump, which provided the predetermined relative rotation between the housing and spool needed to pay out a desired length of line through the apertures in the trimmer housing. Since the cams interacted with simple, inwardly facing cam follower surfaces formed only on a single level, the release mechanism was deemed relatively economical to manufacture and, due to the large abutment surface areas presented between the cams and cam follower, the device was durable, trouble free and reliable. 
   Because of early difficulties in molding some of the components of the cutting head disclosed in U.S. Pat. No. 4,458,419, the head became more expensive to manufacture than anticipated. New material developments subsequently reduced the cost of manufacture. In the meantime, however, a similar bump-feed drive mechanism was developed in which large square cams were formed on the upper and lower outer radial surfaces of the spool and the corresponding cam followers were formed by upper and lower portions of the housing which surrounded the spool. Such a head is disclosed in the incorporated reference, U.S. Pat. No. 4,959,904, and is still in production. 
   Over the years, with increasing competition from offshore manufacturers, it became clear that even with the development of new materials the earlier bump-feed mechanism covered by U.S. Pat. No. 4,459,419 was not as economical to manufacture as earlier believed. It contained several parts, some of which had to be hand assembled. In addition, vibration, the threaded engagement between the cam member and the drive bolt, and the heat generated by the trimmer required the use of a chemical bonding agent having a high melting point to prevent the cam member and cam follower from breaking loose from the drive bolt. Such agents, however, had extremely high break way torques, rendering the threaded connection effectively permanent. As a result, certain components of the head could not be replaced when worn. Thus, that head was significantly modified so as to retain all of the advantages of its predecessor yet utilize fewer component parts and obviate the need for any hand assembly and use of chemical bonding. That modification is the subject of a pending U.S. patent application entitled “Trimmer Head for Use in Flexible Line Rotary Trimmers”, filed Oct. 2, 2003 and identified by Ser. No. 10/677,700, of which this application is a continuation-in-part. The bump-feed and manual heads of the present invention retain all of the advantages of the above-described heads and adds thereto the ability to far more quickly and easily uniformly wind lengths of cutting line onto the spool without materially increasing the cost of production. 
   SUMMARY OF THE INVENTION 
   Briefly, the present invention comprises an improved bump-feed-type rotary trimmer head including a housing defining a depending axially disposed tubular extension adapted to receive the drive bolt therein and shaped so as to define a first interference fit with the drive bolt and a second interference fit with a cam member such that rotation of the drive bolt effects corresponding rotation of the housing and cam member. The cam member defines a pair of vertically adjacent cams, preferably square in cross-section with each cam defining four perpendicularly disposed cam surfaces, the upper of said cams being rotationally offset 45° with respect to the lower of the two cams. A generally cylindrical cam follower defining two pair of diametrically opposed and inwardly facing abutment members arrayed about the central axis of the housing channel is disposed about the cam member. The abutment members are spaced 90° apart in a common horizontal plane and are carried by a cylindrical wall of the cam follower that extends about the cam follower. Each of the abutment members defines angularly disposed leading and trailing surfaces, the trailing surfaces defining cam abutment surfaces. A coil spring urges the cam follower downwardly against the cam member and a slidably disposed fastener engages the extended lower end of the drive bolt adjacent the lower end of the cam member such that the cam member is vertically moveable against the force of the coil spring relative to the cam follower between a first drive position in which the leading cam surfaces on the lower cam are in planar alignment with the trailing cam abutment surfaces on the cam follower and a second drive position in which the leading cam surfaces on the upper cam are in planar alignment with the trailing cam abutment surfaces of the cam follower. 
   In operation, the drive motor on the trimmer rotates the trimmer housing and cam member in a first direction that is imparted to the cam follower as a result of the abutment of the cam surfaces on the lower cam with the trailing cam abutment surfaces on the cam follower. Corresponding rotation of the spool is effected by the projection of the engagement lugs on the cam follower in the slots in the inner spool wall. Upon the cutting head being bumped upon the ground, a 45° rotation of the cam relative to the cam follower is effected and a subsequent 45° rotation occurs upon the head being released from the ground so as to effect a relative rotation of 90° between the spool and the housing and the paying out of predetermined lengths of fresh cutting line with each bump of the head upon the ground, regardless of the duration of the bump. 
   To facilitate loading the head with cutting line, the spool is provided with line receptor channels, that are preferably tapered and polygonal in cross-section, that project into an upper spool flange in a generally radial direction and are adapted to be radially aligned with the outlet eyelets in the housing wall by rotating the spool relative to the housing. Upon inserting the end portion of a length of cutting line through each of the eyelets and pushing the line firmly into the aligned receptor channels, the line will be securely held in place by the channel walls when pulled at an acute angle back toward the spool. Thus, by holding the housing stationary and rotating the spool in the same direction as the spool rotates in the drive mode, the secured lengths of line will be wrapped about the rotating spool, obviating the need to separate the spool from the housing for line loading purposes. 
   To provide an even distribution of the lengths of cutting line about the spool and prevent tangling within the spool, the trailing surfaces on the lower cam that are adjacent and perpendicular to the cam surfaces thereon and the leading surfaces on the abutment members on the cam follower are oppositely inclined such that rotation of the spool in the drive direction while holding the housing stationary will cause the inclined leading surfaces on the abutment members on the cam follower to periodically abut and slide upwardly along and over the trailing surfaces on the lower cam, compressing the coil spring. Once the cam surfaces clear the cam abutment members, the coil spring will force the cam follower downwardly, realigning the cam abutment surfaces with the lower cam. As a result, continual manual rotation of the spool relative to the housing will wrap the lines about the spool while providing a vertical reciprocating or ratcheting effect of the spool with respect to the housing as the line is wrapped thereon so that the line is uniformly disposed about the spool. Printed indicia are preferably molded into the upper surface of the spool to allow the user to easily orient the spool relative to the housing such that the receptor channels are radially aligned with the exit apertures in the housing enabling the line to be readily inserted through the eyelets and into the receptor channels to load the line about the spool. 
   The line receptor channels and spool ratcheting mechanism of the present invention that facilitate line loading can also be utilized in other bump and feed head configurations and in manual heads. In each case, the line receptors are provided on the spool flange radially alignable with the outlet eyelets in the housing. In a bump-feed head such as that disclosed in U.S. Pat. No. 4,959,904 at least the trailing surfaces on the lower cam follower that is defined by lower outer radial surfaces of the spool is inclined such that rotation of the spool in the drive direction while maintaining the housing in a stationary disposition will cause the spool to periodically ratchet upwardly and downwardly within the housing as the line is drawn inwardly through the eyelets and wrapped about the spool to effect an even distribution of the lengths of line about the spool within the housing. The leading radial surfaces of the lower cam follower and the trailing surfaces of the cams formed by the upper and lower portions of the housing may also be inclined to provide a smoother ratcheting movement for the head during the winding of the line onto the spool. 
   In a manual feed head such as that disclosed in U.S. Pat. No. 4,145,809, a plurality of pins or drive lugs are disposed about and project upwardly from the upper surface of the spool and project into correspondingly sized and spaced apertures in the upper surface of the housing such that rotation of the housing will effect corresponding rotation of the spool. By providing radially alignable line receptors in the spool flange and ramping the interior upper surface of the housing between each of the aperatures therein, the line ends can be inserted through eyelets into the receptor channels and gripped by the spool so that rotation of the spool relative to the housing as above described will cause the lugs on the spool to repeatedly travel downwardly along adjacent ramps and snap upwardly into the next aperture. Continued relative rotation will thus effect the desired reciprocating motion of the spool within the housing to evenly distribute the cutting line about the spool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a first embodiment of the trimmer head of the present invention shown secured to the drive bolt of a rotary trimmer. 
       FIG. 2  is an exploded perspective view of the various elements comprising the embodiment of the trimmer head of the present invention illustrated in  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the trimmer head housing of the present invention taken along line  3 - 3  in  FIG. 2 . 
       FIG. 4A  is a top view of the cam member of the present invention. 
       FIG. 4B  is a side view of the cam member of the present invention. 
       FIG. 5A  is a top view of the cam follower member of the present invention. 
       FIG. 5B  is a side view of the cam follower member of the present invention. 
       FIG. 5C  is a sectional view taken along the line  5 C- 5 C in  FIG. 5A . 
       FIG. 6  is a top view showing the relative positioning of the cam member and cam follower in their normal operating position. 
       FIG. 6A  is a cross-sectional view taken along the line  6 A- 6 A in  FIG. 6 . 
       FIG. 7  is a top view showing the relative positioning of the cam member and cam follower in the line feeding position. 
       FIG. 8  is a top view showing the relative positioning of the cam member and cam follower in the line wrapping position. 
       FIG. 8A  is a cross-sectional view taken along the line  8 A- 8 A in  FIG. 8 . 
       FIG. 8B  is a sectional view illustrating the movement of one of the cam abutment members on the cam follower upwardly along and over one of the trailing surfaces of the lower cam during the winding of line onto the spool. 
       FIG. 9  is a sectional view of the embodiment of the trimmer head of the present invention illustrated in  FIGS. 1-8B . 
       FIG. 10  is a perspective view of the spool used in the embodiment of the trimmer head of the present invention illustrated in  FIGS. 1-9  with a portion of the spool broken away to illustrate the configuration of one of the line receptor channels therein. 
       FIG. 11A  is an enlarged cross-sectional view taken along the line  11 A in  FIG. 10 . 
       FIG. 11B  is an enlarged partial side view showing the guide surface adjacent the outlet ends of the line receptor channels. 
       FIG. 11C  is a further enlarged partial side view showing the line receptor channel wall surface adjacent the outlet end of the receptor channel. 
       FIG. 11D  is an enlarged partial side view showing the preferred angular orientation of a line receptor channel having a diamond-shaped cross-sectional configuration relative to the guide wall surface adjacent the outlet end of the receptor channel. 
       FIG. 11E  is an enlarged partial side view showing the preferred angular orientation of a line receptor channel having a triangularly-shaped cross-sectional configuration relative to the guide wall surface adjacent the outlet end of the receptor channel. 
     FIG.  11 F 1  is an enlarged partial side view showing the outlet end of a line receptor channel and adjacent guide surface wherein the channel wall is cylindrical and provided with a roughened surface to grip and hold the line. 
     FIG.  11 F 2  is an enlarged partial side view showing the desired orientation of a ribbed channel wall configuration relative to the guide surfaces adjacent the outlet end of the line receptor channel. 
       FIG. 11G  is an enlarged partial side view showing the preferred angular orientation of a line receptor channel having a oval-shaped channel wall configuration relative to the guide wall surface adjacent the outlet end of the receptor channel. 
       FIG. 11H  is a perspective view of a portion of a length of particularly configured cutting line employable in the trimmer head of the present invention. 
       FIG. 11I  is a sectional view taken along the line  11 I- 11 I of  FIG. 11H . 
       FIG. 11J  is an enlarged partial side view showing the outlet end of a line receptor channel and adjacent guide surface adapted for use with the cutting line illustrated in  FIGS. 11H and 11I . 
       FIG. 11K  is a perspective view of a portion of a length of another example of a particularly configured cutting line employable in the trimmer head of the present invention. 
       FIG. 11L  is an enlarged partial side view showing the outlet end of a line receptor channel and adjacent guide surface adapted for use with the cutting line illustrated in  FIG. 11K . 
       FIG. 12  is a sectional exploded view showing a modification of the housing portion of a trimmer head of the present invention and the drive bolt used with the modified housing. 
       FIG. 13  is a sectional view of one of the trimmer head eyelets. 
       FIG. 14A  is a sectional view of the spool showing the inner end portion of a length of cutting line being held within one of the line receptors and being wound about the spool. 
       FIG. 14B  is a sectional view of the spool having an inwardly inclined line receptor channel and showing the inner end portion of a length of cutting line being held within one of the line receptors and being wound about the spool. 
       FIG. 14C  is a partial sectional view of a spool having a single line guide wall surface and showing the inner end portion of a length of cutting line exiting the adjacent line receptor channel and being pulled against the guide wall surface. 
       FIG. 15  is a bottom plan view of the spool showing the eyelet alignment indicia thereon. 
       FIG. 16  is a bottom plan view of an alternate embodiment of the spool employing a second opposed pair of line receptors for accommodating different sized line. 
       FIG. 17  is an enlarged exploded view of portions of an alternate embodiment of housing and cam member employable in the present invention. 
       FIG. 18  is an enlarged exploded view of another alternate embodiment of the housing and drive cam of the present invention similar to that shown in  FIG. 17  but with the elements creating the interference fit between the housing and the cam member being reversed. 
       FIG. 19  is an enlarged partial exploded view of yet another alternate embodiment of the housing and drive cam employable in the present invention. 
       FIG. 20  is a perspective view of a second embodiment of the trimmer head of the present invention as seen from below. 
       FIG. 21  is a perspective view of a second embodiment of the trimmer head of the present invention as seen from above. 
       FIG. 22  is an exploded perspective view of the various elements comprising the second embodiment of the trimmer head of the present invention illustrated in  FIGS. 20 and 21 . 
       FIG. 23  is a top plan view of the trimmer head housing of the second embodiment of the present invention. 
       FIG. 24  is bottom plan view of the trimmer head housing of the second embodiment of the present invention. 
       FIG. 25  is a cross-sectional view taken along the line  25 - 25  in  FIG. 24 . 
       FIG. 26  is a perspective view of the underside of the housing of the second embodiment of the present invention showing the interior surface of the upper wall of the housing and the ratcheting ramps formed therein. 
       FIG. 27  is a sectional view of the spool of the second embodiment of the present invention. 
       FIG. 28  is a top plan view of the spool of the second embodiment of the present invention. 
       FIG. 29  is a sectional view of the second embodiment of the trimmer head of the present invention illustrating the spool and trimmer head housing in the drive mode. 
       FIG. 30  is a sectional view of the second embodiment of the trimmer head of the present invention illustrating the spool and trimmer head housing in the initial line winding mode. 
       FIG. 31  is a cross-sectional view of the trimmer head spool of the second embodiment of the present invention taken along line  31 - 31  of  FIG. 27  and showing the inner end portions of the cutting line being wound about the spool. 
       FIG. 32  is a perspective view of a third embodiment of the trimmer head of the present invention as seen from below. 
       FIG. 33  is a perspective view of a third embodiment of the trimmer head of the present invention as seen from above. 
       FIG. 34  is an exploded perspective view as seen from below of the various elements comprising the third embodiment of the trimmer head of the present invention illustrated in  FIGS. 20 and 21 . 
       FIG. 35  is an exploded perspective view of the various elements comprising the third embodiment of the trimmer head similar to  FIG. 34  but as viewed from above. 
       FIG. 36  is a sectional view of the third embodiment of the trimmer head of the present invention illustrating the spool and trimmer head housing in the line loading and bump-feed modes. 
       FIG. 37  is a sectional view of the third embodiment of the trimmer head of the present invention illustrating the spool and trimmer head housing in the initial line loading and drive modes. 
       FIG. 38  is a bottom plan view of the upper portion of the housing of the third embodiment of the present invention. 
       FIG. 39  is a cross-sectional view taken along the line  39 - 39  in  FIG. 38 . 
       FIG. 40  is a top plan view of the lower portion of the housing in the third embodiment of the present invention. 
       FIG. 41  is a cross-sectional view taken along the line  41 - 41  in  FIG. 40 . 
       FIG. 42  is a top view of the spool of the present invention showing the relative positioning of the lower cam follower with respect to the upper cam follower with the lower cam follower and line receptors being shown in dotted lines. 
       FIG. 43  is a cross-sectional view taken along the line  43 - 43  in  FIG. 42 . 
       FIG. 44  is a bottom plan view of the spool of the third embodiment of the trimmer head of the present invention showing the relative positioning of the upper cam follower with respect to the lower cam follower with the upper cam follower and line receptors being shown in dotted lines. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now in detail to the drawings, a first embodiment of a bump-feed type trimmer head  10  of the present invention is shown in  FIG. 1  mounted on the extended end of a rotatable drive shaft  12  on a gasoline or electric powered rotary trimmer (not shown). The trimmer head  10  generally comprises a housing  14 , a spool  16  for carrying one or more lengths of coiled monofilament nylon cutting line  17 , a cam member  18 , a cam follower  20 , a coil spring  22 , a drive bolt  24  and a retaining nut  25 . The trimmer housing  14  is preferably formed by injection molding a nylon  6  copolymer and defines a circular upper wall  26 , a cylindrical depending skirt  28  and a centrally disposed tubular extension  30  depending from upper housing surface  26  into the interior of the housing about the central axis of rotation “Y” of the head. The tubular extension  30  in the trimmer head housing  14  defines an annular outer shoulder  32  for coil spring  22  and an axial channel  34  through which the drive bolt  24  extends. Channel  34  is configured to create a mating fitment with both the drive bolt  24  and cam member  18 . The upper end portion  36  of channel  34  is preferably square in cross-section; the central portion  38  is of a constant radius and the lower portion  40  is hexagonal in cross-section. 
   As seen in  FIGS. 2 and 9 , the drive bolt  24  defines a square head portion  24   a  which is received within the correspondingly configured upper portion  36  of channel  34 , a cylindrical body portion  24   b  that extends through the central cylindrical portion  38  of channel  34 , and a lower shaft portion  24   c  that projects from the larger diameter body portion  24   b  and extends through and projects from the lower hexagonal portion  40  of channel  34 . The drive bolt also defines an internally threaded cylindrical bore  24   d  extending axially through the head portion  24   a  and a substantial part of central portion  24   b  for threaded engagement with the drive shaft  12  of the trimmer. Thus, with the drive bolt  24  disposed in channel  34  and in threaded engagement with the drive shaft  12 , rotation of the drive shaft imparts corresponding rotation to the drive bolt  24  and housing  14  due to the interference fit between the square head portion  24   a  of the drive bolt and the upper portion  36  of channel  34  defined by housing extension  30 . 
   It should be noted that the head portion of the drive bolt and the cross-section of the upper portion of the axially depending tubular member could be formed of shapes other than square to form the desired interference fit. For example, they could both be hexagonally shaped and rotation of the drive bolt would still be imparted to the trimmer head. 
   The cam member  18  is preferably molded of nylon 6 glass reinforced material, is of single-piece construction and, in the preferred embodiment, defines a hexagonally-shaped head portion  42 , an upper cam  44 , a lower cam  46  and a lower skirt portion  48 . Head portion  42  is sized and shaped so as to be received within the lower portion  40  of channel  34  in extension  30  such that rotation of the housing  14  in a counterclockwise direction (as seen from above and indicated by arrow D in  FIGS. 6 and 7 ) will impart corresponding rotation to the cam member  18 . In the preferred embodiment, the head portion  42  of the cam member  18  and the cross-section of the lower portion  40  of channel  34  are hexagonal. It is to be understood, however, that other non-circular shapes (e.g. square) could be used to provide the desired interference fit between the tubular extension  30  in the housing and the cam member. 
   In alternative embodiments of the housing and cam member, the head portion  42 A of cam member  18 A and the cross-section of the lower portion  40 A of the tubular extension  30 A in the housing  14 A is cylindrical and the interference fit between the housing and the cam member is provided by means of a plurality of ribs or lugs  45 A projecting vertically from the extended end  47 A of the tubular extension  30 A and a corresponding plurality of receiving slots or apertures  49 A formed in upper surface  51 A of cam  44 A as seen in  FIG. 17 . While at least one complimentary pair of ribs and slots or lugs and apertures would be required to prevent relative rotational movement between the housing and cam member, a greater number is preferable and, from a manufacturing and operational standpoint, four equally spaced pairs of ribs and slots or lugs and apertures would appear to be ideal. Such a configuration is illustrated in  FIG. 17 . It is to be understood that the male element of such an interference fit (e.g., rib or lug) could be provided on either the extended end  47 A of the tubular housing extension  30 A as shown in  FIG. 17  or on the upper surface  51 A of the cam  44 A. In either case, the corresponding female elements (e.g., slot or aperture) would be provided in the other component. Such a reversal of parts is shown in  FIG. 18 . In yet another alternative embodiment, the head portion of the cam member could be eliminated altogether and the required interference fit provided by the same or similar plurality of ribs or lugs  45 A′ and receiving slots or apertures  47 A′. Such a variation is illustrated in  FIG. 19 . Again, the corresponding male and female elements could be reversed. 
   The upper and lower cams  44  and  46  are preferably each of a square configuration so as to define four identical perpendicularly disposed surfaces,  44 ′ and  46 ′ on each cam. That portion of each of those surfaces that is adjacent a corner of one of the cams  44  or  46  on the drive or leading side of the cam, as the cam rotates in a counterclockwise direction D (as seen from above), defines a cam surface  44   a  or  46   a . Each cam surface on each cam is parallel to the axis of rotation Y of the head. The upper cam  44  is rotationally offset 45° from the lower cam  46  as seen, for example, in  FIG. 4A . Those portions of lower cam surfaces  46 ′ that are perpendicular to and adjacent cam surfaces  46   a  (and thus on the trailing sides of the cam  46  as the cam member  18  rotates counterclockwise) are inclined upwardly as seen, for example, in  FIGS. 2 and 4B  and define slide surfaces  46   b . Slide surfaces  46   b  can be formed by an inclined linear surface or a curvilinear surface. In the embodiment of the invention illustrated in  FIGS. 1-9 , the slide surfaces are preferably radiused. By way of example, in a cam member  18  in which the upper and lower cams  44  and  46  each define surfaces  44 ′ and  46 ′ of about 0.90 in. in length and the lower cam  46  has a thickness of about 0.20 in. The inclinations on trailing slide surfaces  46   b  define a circular segment having a radius of 0.125 in. Alternatively, surfaces  46   b  could be upwardly inclined at an angle of about 25 degrees. 
   Cam member  18  further defines an axially disposed channel  50  extending vertically therethrough. Channel  50  has a first upper constant radius portion  50   a  adapted to receive the first constant radius portion  24   b  of drive bolt  24  and a second smaller diameter constant radius portion  50   b  adapted to receive in a slip fit the second and smaller constant radius portion  24   c  of drive bolt  24 , which extends therethrough. 
   The cam member  18  is disposed within trimmer head  10  interiorly of the cam follower  20 , the configuration which is best seen in  FIGS. 5A and 5B . To properly align the cam member  18  with respect to the line outlet eyelets  78  in the trimmer head housing, a key  42 ′ is molded into the side of the head portion  42  of the cam member which is received in a slot  40 + in lower portion  40  of the central housing channel  34 . 
   The cam follower  20  is preferably molded of the same material as cam member  18 , is of single-piece construction and defines a cylindrical wall portion  52  circumscribing a chamber  54  and four equiangularly disposed projections defining abutment members  56  extending radially inwardly of chamber  54  from the upper interior end portions of cylindrical wall  52 . Each of the abutment members  56  defines an angularly disposed cam abutment surface  56   a  and an inclined slide surface,  56   b . Relief areas  60  are disposed between members  56 . The abutment surfaces  56   a  are on the trailing side of each abutment member, extend parallel to the axis of rotation Y of the cutting head and are angled at 135° with respect to an adjacent slide surface  56   b . A plurality of outwardly projecting radial lugs  62  (four being shown) are equiangularly disposed about the cylindrical wall portion  52  of the cam follower  20  for the releasable securement of the spool  16  to the cam follower. 
   The spool  16  defines an upper annular flange  70  and a lower annular flange  72  carried by a hollow cylindrical body portion  74  so as to define an annular area  76  between flanges  72  and  74  for carrying coils of flexible nylon cutting line  17  wrapped about body portion  74  such that upon assembly, the end portions  17 ′ of the cutting line extend outwardly through eyelets  78  which are press fit through opposed apertures  80  in the sidewall of the head formed by housing skirt  28 . In the preferred head configuration shown in  FIG. 1 , the portions of the housing skirt  28  adjacent the eyelets  78  are raised or ramped radially outwardly to protect the eyelets during use from foreign objects. 
   The body portion  74  of spool  16  further defines a rounded bumper  81  at its lower end, an interior cylindrical chamber  82 , a pair of diametrically opposed and identically configured vertical locking channels  84  in the interior side wall thereof and a pair of diametrically opposed and identically configured vertical guide channels  88  transversely aligned with respect to locking channels  84 . As seen in  FIG. 10 , locking channels  84  terminate at their lower ends in somewhat shallower offset portions  90  that terminate in a pair of opposed securement apertures  92  extending through the cylindrical body portion  74 . The locking and guide channels are each adapted to slidably receive one of the outward projecting radial lugs  62  on the cam follower  20 . The guide channels  88  differ from locking channels  84  in that they are wider, of a constant length and do not terminate in apertures. The guide channels preferably have a width equal to the width of the locking channels plus the length of the offset portions  90  of the locking channels  84 . 
   The spool  16  is secured to the cam follower  20  upon aligning the lugs  62  with the locking and guide channels  84  and  88  such that the end portions  17 ′ of the cutting line  17  project radially from the spool  16  proximate eyelets  78 , the spool is pressed over the cam follower until the lugs  62  reach the lower ends of the guide and locking channels. The spool is then rotated such that the lugs in the two locking channels  84  pass into the slightly shallower offset portions  90  thereof, slightly compressing the cam follower until the two lugs reach the apertures  92  whereupon the resiliency in the cam follower material causes the lugs to snap into apertures  92 , securing the spool to the cam follower. In the locked position, the two lugs in apertures  92  are disposed adjacent the aperture walls and the two lugs in the guide channels  88  are adjacent the leading walls of the channels such that during use, all four lugs will abut their adjacent walls to effect corresponding rotation of the spool  16  with the cam follower  20 . To remove the spool, one need only twist the spool relative to the cam follower and when the lugs are pulled back into the vertical portion of the locking channels, the spool can be easily axially withdrawn from the housing. 
   The above-described lug and channel configuration allows the spool  16  to be used with cam followers having either four equally-spaced drive lugs  62  (as shown) or two opposed lugs if desired. In addition, the driving force is evenly distributed among the four lugs  62  on the cam follower  20 . Guide channels  88  are provided in lieu of a second pair of locking channels  84  for mold forming purposes only. Otherwise, four identical locking channels could be employed. If desired, the two guide channels in the spool could be widened so as to each define an arcuate length of about 95° such that the spool could accommodate cam follower configurations having six equally-spaced projecting lugs. Again, the guide channels would be sized such that two of the lugs in each of the guide channels would be adjacent a leading wall of the channel such that during use, four lugs will again function as drive lugs to effect rotation of the spool. 
   To provide rapid loading of the trimmer line about spool  16 , the upper spool flange  70  is provided with a pair of opposed line receptors  91  for gripping inner end portions  17 ″ of two separate lengths of cutting line  17 . Each of the receptors  91  comprises a line receptor channel  93  that extends radially inwardly from an enlarged outer flared portion  93 ′ adjacent the outer edge of the spool to the spool&#39;s cylindrical body portion  74 . The receptor channels  93  are configured and oriented so as to tightly grip the cutting line  17  when an end portion of the line is inserted therein, through the aligned eyelet, and pulled at an acute angle back toward the spool, as will be described. Examples of channels  93  are shown in detail in  FIGS. 11A-G ,  11 J,  11 L,  14 A and B. A preferred channel configuration is polygonal in cross section, most preferably hexagonally shaped, and tapers inwardly from the enlarged flared portion  93 ′ to body portion  74  at an angle of about 5°. The size of the receptor channels depends on the size of the line to be secured therein. By tapering the channel walls inwardly at an angle of about 5°, the channels can accommodate variations in line size. 
   By way of example, a tapered channel  93 , hexagonal in cross-section and having a length (exclusive of flared portion  93 ′) of about 0.650 in., a transverse dimension measured across the two parallel sides adjacent the enlarged flared outlet end of about 0.130 in. and a transverse dimension across the inner channel end of about 0.075 in. (see, e.g.,  FIG. 11A ), has been successfully employed in trimmer head  10 . Conventional nylon cutting line having diameters of 0.080 in., 0.095 in. and 0.105 in. can be received therein and tightly gripped by the receptor channel walls as the line is pulled from the outer end of the channel and wrapped about the spool as shown in  FIGS. 14A and 14B . 
   To properly direct the line inwardly upon exiting the receptor channel, the downstream or left side of the enlarged flared portion  93 ′ of each receptor  91  is cut away so as to define flat guide wall surfaces  94   a  and  94   b  as shown in FIGS.  11 B and  13 - 15 . Surface  94   a  is substantially perpendicular to the central axis of the receptor channel and inclined slightly downwardly such that the central longitudinal axis “X” of the guide wall surface defines an angle declination of about 5°-10°, depending on the configuration of the spool, with respect to the horizontal. Adjacent surface  94   b  is inclined inwardly to direct the line toward the center of the spool. Thus, when the cutting line is inserted into one of the receptor channels  93  and pulled laterally against guide surface  94   a  and inwardly against guide surface  94   b , the line effectively forms an acute angle with the central channel axis. In addition, the lower inner surface  95  of the flange extending under channel  93  is rounded so as to avoid any abrupt surface deviations on the spool adjacent the line receptors  91  which could interfere with the proper winding of the line and to direct the line downwardly toward the lower flange  72 . The channel  93  is preferably oriented about its central axis such that opposed corners of the channel align with the central axis X of guide wall surface  94   a  as shown in  FIG. 11C . 
   By aligning opposed channel corners with the central axis “X” of guide wall surface  94   a , the cutting line is pinched by the converging channel walls as the line is pulled from the channel and along the adjacent guide wall surface  94   a . Due to the inherent stiffness in the nylon cutting line, this pinching of the cutting line occurs not only at the channel wall corner  93 ″ adjacent guide surface  94   a  (see  FIG. 11C ), but also at the opposed corner at the inner end of the line receptor channel, enhancing the gripping of the line. While a line receptor channel having a hexagonally configured cross-section that is not aligned with the central axis of surface  94   a  as above described (see, e.g.,  FIG. 11B ), will still grip the line, the alignment illustrated in  FIG. 11C  takes better advantage of the pinching effect created by the hexagonal cross-sectional configuration of the channel and is thus preferred. Further, by inwardly inclining the central axis of the receptor channel  93  at about 5° toward guide wall  94   a , as seen in  FIG. 14B , as opposed to radially aligning the central axis of the channel with the center of the spool as seen in  FIG. 14A , the central channel axis forms an acute angle with respect to a line tangent to the flange at the outlet end of the channel. As a result, cutting line is caused immediately to form an acute angle with respect to the central channel axis as it exits the receptor channel and is pulled against the adjacent guide wall surface  94   b . This further increases the pinching effect of the channel wall on the line, further enhancing the gripping of the cutting line. The more securely the receptor channel grips the line, the easier it is for the user to effect the initial winding of the line about the spool without the line being inadvertently pulled from the receptor channel. However, the acute angle formed adjacent to the outlet ends of the receptor channels by inclining the central axis of the channels inwardly as described, may be too tight for 0.105 in. diameter line. Accordingly, in trimmer head designed to accommodate such larger line, a radially directed channel may be preferred. 
   Additional line receptor channel configurations are illustrated in  FIGS. 11D-G .  FIGS. 11D  and E illustrate other polygonal configurations particularly suited for use with the present invention.  FIG. 11D  illustrates a line receptor channel  93   a  having a diamond-shaped cross-section. To maximize the line pinching effect of such a channel, the channel should be oriented such that the opposed corners lying on the minor axis of the cross-section lie on the longitudinal axis “X” of the guide wall surface as shown in the drawing.  FIG. 11E  illustrates a line receptor channel  93   b  having a triangularly-shaped cross-section. To maximize the line pinching effect of such a channel configuration, one of the apexes of the triangle defined by the channel at the outlet end thereof is positioned on the longitudinal axis of the guide wall surface adjacent the guide wall surface as shown in  FIG. 11E . 
   Other polygonal cross-sectional configurations could also be employed in the formation of the line receptor channels  93  of the present invention. It was believed that a channel formed by more than about eight side walls would be sufficiently round so as to not provide the desired gripping force on the line. Round radial channels had been found not to provide adequate grip on the line as have channels defining a square cross-sectional configuration when the flat sides of the square lie on the longitudinal axis of the guide wall surface. These findings were made using spools formed by injection molding a nylon 6 copolymer, as in the formation of the trimmer housing  14 , which provides a relatively slick channel wall surface. By providing cylindrical (or round) receptor channels  93   c  with roughened wall surfaces  93   c ′, the channel walls can provide the necessary gripping force on the line to hold the line in place to effect the loading of the line on the spool as described earlier herein. Such a roughened surface, illustrated in FIG.  11 F 1 , can be formed in the channel wall, for example, by using a textured pin during the manufacture of the spool to impart surface irregularities into the channel wall. Such a surface can also be formed by forming the line receptors and thus the channel walls defined thereby, of a reinforced or filled material such as, for example, PA-6 with a 15%-30% glass fill. Such a material will provide sufficient surface irregularities in the channel wall to grip and hold an end portion of the line as the line is wound about the spool as described herein. This can be readily accomplished by molding the spool of such a material. Other types of irregularities in the channel walls could also be employed to grip and hold the line. For example, FIG.  11 F 2  illustrates a line receptor channel configuration in which a plurality, preferably four, longitudinally extending ribs  93   c ″ are provided in an otherwise round channel wall to grip the line. To prevent excessive wear on the ribs and/or line, the ribs are preferably spaced such that the line would bear equally against two of the ribs both at the inner and outer ends of the channel as seen in FIG.  11 F 2 . Other such irregularities in the side wall(s) of the receptor channel could include helically extending ridges on channels (not shown). 
   As with line receptor channels that are polygonal in cross-section, a round or constant diameter receptor channel is preferably tapered inwardly as previously described and illustrated in  FIG. 11A  to accommodate variations in line size. Further, by providing such a taper in the channel wall, it may not be necessary to provide surface irregularities in the channel wall to obtain efficient gripping force to hold the line in place during line loading. 
   Other channel configurations could also be employed without the need for roughened surfaces or other wall irregularities and/or tapering of the channel. For example, as illustrated in  FIG. 11F , a line receptor channel  93   d  having an oval-configuration wherein the minor axis of the oval lies on the longitudinal axis of the guide wall channel surface should provide adequate gripping force for the line. 
   While the above discussed line receptor channel configurations have been described and illustrated as extending the full length of the channel, and indeed such configurations are preferred, it should be noted that the gripping characteristics of the channel, need not always extend the length of the channel. Acceptable gripping of the line generally may be obtained by providing the line gripping cross-sectional configuration only at the outer end portions of the channels. By way of example, the outer end portion of the channel could be hexagonally or diamond-shaped in cross-section, while the remainder of the channel could be round and formed of a material such as a nylon 6 copolymer. As the line is pulled laterally from the channel and against the adjacent guide surface  94   a  and then inwardly against surface  94   b , the line would be retained in the receptor channel by the converging walls in the outer end portion of the channel. The outer portion of the channel in such configurations should be at least about 0.150 in. in length. However, when the gripping surface is defined by a roughened round channel wall of constant diameter (non-tapered) the roughened surface should preferably extend substantially the length of the channel to enhance the gripping force on the line. This is particularly so if the roughened surface is defined by a roughened material as opposed to forming more substantial surface irregularities in the channel wall such as the ribs  93   c ″ illustrated in FIG.  11 F 2 . Similarly, when utilizing a tapered line receptor channel to accommodate multiple line sizes, only the inner portion of the line, needs to be tapered. Preferably, at least about fifty percent of the axial length of the channel (exclusive of flared portion  93 ′) should be tapered in such channel configurations. 
   In addition to retaining the end portions of the cutting line by configuring the cross-sections of at least the outer portions of the line receptor channels so as to grip the line as above-described, the channels could be configured to cooperate with a particular line configuration to effect securement of the line by a mating or keying effect as the line is wrapped about the spool. For example, a flexible noise attenuating trimmer line marketed by Proulx Manufacturing, Inc. of Rancho Cucamonga, Calif., under the name Ultra Quiet, is formed by extruding two non-filament polymer strands in close disposition and twisting the two strands together about a longitudinal axis in a cooling bath. Upon curing, the formed line defines two overlapping cylindrical strands joined together in two opposed substantially V-shaped troughs that extend helically along and about the line. Such a line configuration has been found to provide substantial noise attenuation as compared to comparably sized conventional line rotating at the same speed and is the subject of a U.S. Pat. No. 6,910,277, issued Jun. 28, 2005. An example of such noise attenuating trimmer line  517  is illustrated herein in  FIG. 11H  and its cross-sectional configuration is illustrated in  FIG. 11J . By configuring the line receptor channel  593  (see  FIG. 11J ) so as to have a corresponding cross-section helically extending along at least the outer portion of the channel, the channel wall will mate with the line as the line is inserted into the channel through the aligned line outlet opening in the housing skirt and rotated, effectively threadably engaging the line in the channel and securing the end portion of line to the spool. 
   Another example of a keyed line and receptor channel is illustrated in  FIGS. 11K and 11L . As seen therein, a length of the cutting line  617  is provided with protruding locking feature  617   a  proximate one end of the line. Feature  617   a  could be of any convenient configuration. At least the end portion of the line receptor channel  693  (see  FIG. 11L ) is correspondingly configured to receive the line with its protruding feature and an offset channel area is provided within the channel to allow the line to be rotated such that the protruding feature is received in the offset area. Thus, upon aligning the feature  617   a  with the outer end of the receptor channel  693 , inserting and twisting the line, the length of line is secured to the spool by the trapped locking feature, whereupon the line can be wrapped about the spool body as previously described. In all such embodiments the circular holes in the eyelets  78  in the side of the trimmer housing are sufficiently larger than the diameter of the cutting line, that the locking feature will not interfere with the extension of the line through the eyelets. 
     FIG. 14C  illustrates yet another modified line receptor which employs a single, inwardly inclined guide wall surface  94   c  disposed adjacent to the outlet end of the receptor channel. The single inwardly inclined surface  94   c , like the inwardly inclined channel  93  illustrated in  FIG. 14B , creates an acute angle between the central axis of the receptor channel and the guide surface adjacent to the channel outlet. This single guide surface  94   a  is preferred for use in smaller heads as it directs the line inwardly toward the center of the spool more quickly than the previously described guide surface comprised of laterally extending portion  94   a  and inclined portion  94   b  and the smaller diameter spools tend to reciprocate upwardly and downwardly more quickly than the larger spools. As the smaller spools are not generally designed to accommodate the larger diameter line, the acute bend created by the guide surface  94   c  is generally not an issue. 
   With each of the above-discussed variations in the line receptors, the line winding process is essentially the same. To wind the cutting line on the spool  16 , the line receptor channels  93  in the spool are first aligned with the eyelets  78  in the side of the housing  14 . Printed indicia such as an arrow  85  are preferably provided on the lower surface of the spool to facilitate alignment as shown in  FIG. 15 . The inner end portions  17 ″ of two separate lengths of cutting line  17  are then inserted through the opposed eyelets  78  in the housing and pushed securely into the aligned receptor channels  93  in the spool flange  70 . With the line and channel configurations illustrated in  FIGS. 11J-11L , the line must also be twisted as above-described. The lengths of line are then bent at acute angles and pulled toward the spool body portion  74  against lateral guide walls  94 . The spool is then manually rotated in a counterclockwise direction using the bumper  81  as a handle while maintaining the housing in a stationary disposition. The preferably tapered and angularly disposed walls defining the receptor channels will tightly grip the inner ends of the cutting line, preventing their withdrawal from the channel. As rotation of the spool in a counterclockwise direction continues, the two lengths of cutting line will be wound about the spools. 
   Manual rotation of the spool in a counterclockwise direction with respect to the housing  14  also will cause corresponding rotation of the cam follower  20  with respect to the cam member  18 , bringing the inclined slide surfaces  56   b  on abutment members  56  into abutment with the oppositely inclined slide surfaces  46   b  on the lower cam  46  (see  FIG. 8A ). Because surfaces  56   b  and  46   b  are inclined in opposite directions, continued counterclockwise rotation of the spool while maintaining the housing stationary will cause the abutment members  56  on the cam follower to ride upwardly on and over the slide surfaces  46   b  on the lower cam  46 . As the cam follower  20  moves upwardly with respect to the cutting head housing  14  so does the spool  16 . This movement is illustrated in  FIG. 8B . When the cam follower  20  is rotated to the point that the trailing corners of the lower cam  46  become aligned with relief areas  60  in the cam follower, the cam follower and thus spool  16  will snap downwardly under the force of coil spring  22  to their original elevations with respect to the housing wherein the cam surfaces  46   a  on the cam member are aligned with the cam abutment surfaces  56   a  on the cam follower. Thus, continual manual rotation of the spool with respect to the housing in the counterclockwise direction will effect continual vertical ratcheting or reciprocation of the spool within the housing as the two lengths of cutting line are pulled inwardly through eyelets  78  and wound about the spool. 
   This reciprocating movement of the rotating spool, while not necessary to effect loading of the cutting line onto the spool, provides for an even distribution of the cutting line about the spool, even though the vertical distance traveled by the spool relative to the housing is less than the distance between the upper and lower spool flanges  70  and  72  as the two lengths of line enter the spool area from opposed sides of the spool and are separately directed toward the center of the spool by the outlet ends of the line receptors. As a result, the lengths of line tend to roll over themselves and fill the spool without becoming entangled on the spool. 
   The above description of the trimmer head  10  and its components is based on using the head on a conventional rotary trimmer in which the gear box (not shown) typically imparts a counterclockwise rotation to the drive shaft  12  and thus to the trimmer head. If the head were used on a trimmer without a gear box or with one that imparted a clockwise rotation to the head, the leading and trailing surfaces on the cams and cam follower abutment members would simply be reversed. Accordingly, it would simply be necessary to reverse the orientation of the cam and slide surfaces on the lower cam  46  and on the abutment members  56  on the cam follower  20 . The cam surfaces  46   a  on the lower cam would then still be on the leading surfaces  46 ′ of cam  46  and the slide surfaces  46   b  on the trailing sides. Similarly, the cam abutment surfaces  56   a  would then still be on the trailing side of each abutment member and the slide surfaces  56   b  would still be on the leading sides. 
   While the spool  16  has been described and illustrated comprising two diametrically opposed line receptors  91 , one such receptor could be employed if a single line head was desired or, alternatively, multiple equally spaced receptors could be utilized. In addition, two pair of opposed receptors of different sizes could be employed to provide additional versatility for the cutting head. For example, in addition to the receptors shown in the drawings and described above, a second pair of line receptors slightly larger in cross sectional dimension could be employed with each pair of opposed receptors being perpendicular to the other pair to balance the head. Through such a configuration, one pair of opposed receptors could be sized to accommodate, for example, small diameter cutting line such as 0.065 in., 0.080 in. and 0.095 in. line, while the second pair of receptors could accommodate larger diameter line such as 0.095 in., 0.105 in. and 0.130 in. For such applications, a second pair of indicia would be imprinted on the upper surface of the spool to assist in the alignment of the second pair of line receptors with the line outlet eyelets and indicate which pair of receptors accommodated the larger and smaller line sizes. For example, a pair of smaller or narrower arrows  85 ′ could be perpendicularly disposed with respect to an opposed pair of layer arrows  85 ″ as shown in  FIG. 16  to identify the channel size and align the lengths of cutting line. 
   Fully assembled, and loaded with cutting line, the cam member  18  is located within the chamber  54  in the cam follower  20  with its hexagonally-shaped head portion  42  disposed within the correspondingly configured portion  40  of channel  34  defined by the housing tubular extension  30 . The coil spring  22  is disposed between and bears against the shoulder  32  formed by the housing extension  30  and the upper surface of the cam follower  20  defined by cylindrical wall  52  and projections  56 , urging the cam follower  20  downwardly about the cam member  18  such that the undersides of abutment members  56  on the cam follower about the upper surface of the skirt portion  48  of the cam member. A 5/16-inch or other suitably sized push-type retainer or pal nut  25  (also referred to as a push nut or bolt retainer) is slid onto the cylindrical lower end of the shaft portion  24   c  of the drive bolt  24  snugly against the underside of skirt  48  on the cam member  18 . The shaft portion  24   c  of the drive bolt can be threaded or smooth and push-type retainers, such as those shown and described in the 2003 edition of the  McMaster - Carr Catalog  at page 2982, are available for threaded as well as unthreaded bolts. By providing the shaft portion  24   c  of the drive bolt with threads, a conventional threaded hex nut could be used for repairs in the field, if necessary, and if a push-type retainer were not available. The use of a push-type retainer, however, allows for simple and totally automated assembly of trimmer head  10  which is an object of the present invention. 
   The spool  16  is disposed within the interior of housing  14  with two of the lugs  62  thereon being disposed in the offset portion of locking channels  82  projecting through apertures  92  and the remaining two lugs being disposed at the bottom of the two guide channels  88 . The bumper  81  on the bottom of spool  16  projects downwardly from the lower end of the housing  14  as seen in  FIG. 1  and the extended ends of the cutting line  17  project through the opposed eyelets  78  in the housing skirt  28 . 
   The eyelets  78  preferably employed with the present invention are constructed of aircraft grade aluminum and each define annular retention flanges  100  at their inner ends and radially extending channels  102  for the passage of the cutting line therethrough and into receptors  91 . As seen in  FIG. 13 , the inner and outer end portions  104  and  106  of channels  102  are radiused to eliminate any sharp corners and accommodate bending of the line about the eyelets without crimping or overly stressing the line. This eyelet configuration allows the eyelets  78  to be attached to the head  10  in an automated process and be held in place by flange  100  and the centrifugal force generated thereon during use. 
   In operation, the rotating drive shaft  12  on the trimmer effects corresponding rotation of the housing  14  and the cam member  18  due to the fitment between the drive bolt  24 , drive shaft  12  and the tubular extension  30  of housing  14 . The cam follower  20  is pressed downwardly about the cam member  18  such that the undersides of projections  56  on the cam follower abut the skirt portion  48  of the cam member  18  and the cam surfaces  46   a  on the lower cam  46  are aligned with and bear against the abutment surfaces  56   a  defined by the abutment members  56  on the cam follower  20  to effect corresponding counterclockwise rotation of the cam follower and the spool carried thereby as seen from above in  FIG. 6 . By providing the skirt portion  48  of the cam member  18  with a vertical length of about 0.5 inches, as opposed to using a thinner disc configuration, any wobble of the cam member within the cam follower during use is minimized. 
   Upon pressing the rotating bumper  81  on the bottom of the spool  16  against the ground or other rigid surface, the trimmer housing  14  and the cam member  18  which is secured thereto by drive bolt  24  and retainer  25  are forced downwardly, compressing coil spring  22  and disengaging the lower cam  46  from the abutment surfaces  56   a  on the cam follower. As the cam member  18  moves downwardly until the lower end of  30 ′ of the tubular extension  30  abuts the upper surface of the upper cam  44 , the lower cam passes out of the path of engagement with the cam abutment surfaces on the cam follower and the cam surfaces  44   a  on the upper cam  44  are brought into the path of cam abutment surfaces  56   a . This causes a slowing of the rotation of the cam follower  20  relative to the cam member  18  and thus of the spool  16  relative to the cam member  18  and housing  14 . When the upper cam surfaces  44   a  strike the abutment surfaces  56   a , corresponding rotation of the cam and cam follower resumes (see  FIG. 7 ). However, during the interim the cam member and housing rotate 45° relative to the cam follower and spool. 
   Once the force of the bump is dissipated, the coil spring  22  forces the spool and housing back to their initial positions, releasing the engagement of cam surfaces  44   a  on the upper cam  44  from the cam follower abutment surfaces  56   a , re-engaging cam surfaces  46   a  and allowing another 45° of relative rotation of the cam member and cam follower and thus of the spool and the housing for a total of 90° of rotation during the bump, regardless of the time duration of the bump. During these periods relative rotation in which the spool lags behind the housing, centrifugal force causes a predetermined amount of fresh cutting line to be paid out through the opposed eyelets  78  in the trimmer housing. The worn line is then severed by a conventional cutting blade (not shown) carried by a protective cover (not shown) mounted on the trimmer above and radially spaced from the rotating head  10 . 
   It should be noted that the cam follower  20  includes relief areas  60  between projections  56  so that the cams  44  and  46  can slide vertically with respect to the cam follower  20  when the cams  44  and  46  are in the line feeding positions relative to the cam follower shown in  FIGS. 6 and 7 , and to allow spool reciprocation during line loading but at no other times. In the position illustrated in  FIG. 7 , the cams  44  and  46  are free to slide upwardly to disengage the cam surfaces  44   a  and in  FIG. 6 , free to slide downwardly to disengage the cam surfaces  46   a . Cams having three or more or differently configured cam surfaces are also possible, with four-sided cams  44  and  46  being a practical comprise between the surface area contact, ease of manufacture, and the desired line feed out. Also, in lieu of square cams defining the cam and slide surfaces adjacent the corners thereof, the angularly offset upper and lower cams could each have four recessed side walls and define four equally-spaced radial projections or tangs at the four corners. The leading and trailing edges of the tangs would then define the cam and sliding surfaces. Such a cam member would be operable without the need to modify the cam follower  18 . 
   In the preferred embodiment of cutting head housing  14 , a recessed area  99  is provided in the housing skirt  28  to define a “window” for a label. As the surface  99 ′ on which the label would be affixed is offset from the remainder of the housing skirt, the label is protected during use. 
   Alternate embodiments of the housing and drive bolt usable in the present invention are illustrated in  FIG. 12 . These embodiments differ from the prior embodiments in that the drive bolt  124  is pushed upwardly through the lower hexagonally-shaped portion  140  of the interior housing extension  130  for assembly. The tubular extension  130  of the modified housing  114  defines a cylindrical upper portion  136  having a raised annular ridge  137  extending about the interior side wall thereof and an extended hexagonally-shaped lower portion  140 . The drive bolt  124  defines a cylindrical upper portion  124   a  having an annular groove  124   e  formed therein, a hexagonally-shaped mid-portion  124   b  and a reduced diameter cylindrical shaft portion  124   c , which, as with the shaft portion  24   c  of drive bolt  24  can be threaded or smooth. Upon inserting drive bolt  124  into tubular extension  130 , the ridge  137  in the upper portion of the bolt provide an interference fit to retain the bolt within the housing. If the bolt is pushed into place just after the housing has been formed, the nylon material will shrink about the bolt as it cools, enhancing the securement. However, even if the bolt is inserted into the housing extension long after the housing is formed and cooling, the snap fitment between the bolt and housing extension will retain the bolt in place. 
   The cylindrical upper portion  124   a  of drive bolt  124  has a threaded cylindrical bore  124   d  extending axially therethrough and into the hexagonal portion  124   b  for threaded engagement with the drive shaft  12  of the trimmer, similar to the prior embodiment. However, if desired, the bolt  124  could be provided with a threaded extension (not shown) adapted to engage a trimmer drive shaft having a threaded female end. This same change could, of course, be employed with drive bolt  24 . The hexagonally-shaped portion  124   b  of the drive bolt is received within an upper portion of the hexagonally-shaped portion  140  of the housing extension  130  and, upon securement of the cam member  18  and cam follower  20  is disposed immediately adjacent the hexagonally-shaped head portion  42  of the cam member. As in the prior embodiment, the shaft portion  124   c  of drive bolt  124  projects downwardly beyond the end of the housing extension  130  and through the cam member  18  for engagement with a push retainer  25 . The remainder of the elements also are identical to the corresponding elements of the prior embodiment. As with the prior embodiment, this embodiment can be assembled in a totally automated process with a minimal number of parts and without the need for chemical bonding elements which are susceptible to heat and/or prevent part replacement. 
   A second embodiment of the present invention is illustrated in  FIGS. 20-31  wherein the line loading mechanism is employed in a manual trimmer head  100 . Head  100  is also mounted on the extended end of a rotatable drive shaft on a gasoline or electric powered rotary trimmer. The trimmer head  100  generally comprises a housing  114 , a spool  116  for carrying one or more lengths of coiled monofilament nylon cutting line  17 , a coil spring  122 , drive bolt  124  and a wing nut  125  for securing the spool  116  to the trimmer head housing  114 . 
   The trimmer housing and spool are preferably formed of the same material as the corresponding components of the prior embodiment. The housing  114  defines an upper circular wall  126 , a cylindrical skirt  128  depending therefrom and a centrally disposed tubular extension  130 . Extension  130  is axially aligned with the central axis of rotation “Y” of the head and includes a depending portion  130   a  and an upwardly projecting portion  130   b . The tubular extension  130  is configured to receive the drive bolt  124  with the upwardly projecting portion  130   b  preferably being square in cross section to mate with the square head portion  124   a  of the bolt and the depending portion  130   a  being of a reduced constant radius to receive the cylindrical body portion  124   b  of the drive bolt. The lower shaft portion  124   c  extends downwardly into and through the interior of the housing and into the spool where it is threadably engaged by the wing nut  125  as will be described (see, e.g.  FIG. 29 ). 
   The drive bolt  124  also defines an internally threaded cylindrical bore (not shown) extending axially through the head portion and a substantial part of the central portion  124   b  of the bolt for threaded engagement with the drive shaft of the trimmer as in the bump-feed head of the prior embodiment. Thus, with the drive bolt  124  disposed in the tubular extension  130  of the trimmer head housing  114  and in threaded engagement with the drive shaft, rotation of the drive shaft imparts a corresponding rotation of the drive bolt and housing (generally counterclockwise) due to the interference fit between the square head portion  124   a  of the drive bolt and the upper portion  130   b  of extension  130 . Again, the head portion of the drive bolt and the cross section of the upper portion of the tubular extension in the housing could be formed of different shapes other than square to form the desired interference fit. 
   The trimmer head housing  114  also defines a pair of opposed slots  180  in the depending cylindrical housing skirt  128 . Slots  180  are open at their lower ends and are adapted to slidably receive a pair of opposed outlet eyelets  178  in a press fitment. Alternatively, the eyelets could be press fit through apertures in the housing skirt as in the prior embodiment. Again, the portions of the housing skirt  128  adjacent the eyelets preferably are raised or ramped outwardly to protect the eyelets from foreign objects during use. A plurality of radially projecting heat dissipation ribs  115  are formed on the upper wall  126  of housing  114  that extend upwardly along the upper portion  130   b  of tubular extension  130 . The heat dissipation ribs  115  are preferably provided with sharpened surfaces  117  for severing weeds that may wrap about the drive shaft adjacent the trimmer head housing during use. A plurality of equally-spaced drive lug receiving apertures  119  extend axially through the upper wall  126  of the trimmer housing which are adapted to receive the upwardly extending projections defining drive lugs  121  on the spool  116  as will be described. 
   The trimmer head spool  116  defines an upper annular flange  170  and a lower annular flange  172  carried by a cylindrical upper body portion  174  so as to define an annular area  176  between flanges  170  and  172  for carrying coils of flexible nylon cutting line  17  wrapped about body portion  174  such that upon assembly, the end portions  17 ′ of the cutting line will extend outwardly through the outlet eyelets  178 . The spool also includes a lower body portion  175  depending from the lower flange  172 . Spool  116  further includes a depending cylindrical extension  131  which, upon assembly, is axially aligned with the tubular extension  130  on the trimmer head housing  114  as seen in  FIG. 39  such that the threaded lower shaft portion  124   c  on the drive bolt  124  extends therethrough and into the area circumscribed by the lower body portion  175  of the spool where the shaft portion is threadably engaged by the wing nut  125 . 
   A coil spring  122  extends about the depending extension  131  in the spool, bears against and extends between the underside of the upper spool flange  170  and an annular recessed surface  125 ′ in the upper portion of wing nut  125 . So secured, the spool  116  and trimmer head housing  114  are urged together by the coil spring  122 . In the secured position, the drive lugs  121  project upwardly from the upper surface of flange  170  into the drive lug receiving apertures  119  in the trimmer head housing, securing the spool to the trimmer housing such that rotation of the housing by the drive bolt is imparted to the spool. To remove the spool from the trimmer head housing it is simply necessary to threadably disengage the wing nut  125  from the threaded lower shaft portion of the drive bolt. 
   To enable the trimmer line to be wrapped about the spool  116  without having to remove the spool from the housing, the upper spool flange  170  is provided with a pair of opposed line receptors  191  for gripping the inner end portions  17 ″ of two separate lengths of cutting line  17 . Spool  116  is sized and configured such that flange  170  is in planar alignment with the line outlet eyelets  178 . Each of the line receptors  191 , including the line receptor channels  193 , is of the same configuration and functions in the same manner as the line receptors  91  in the prior embodiment. The dimensions may vary slightly depending on variations in the sizes of the respective spools and the diameter or diameters of the cutting line for which the head is designed. 
   In addition to the inclusion of the line receptors  191  on spool  116 , the interior surface  126 ′ of the upper wall  126  of the trimmer head housing  114  is provided with a plurality of arcuate inclined ramps  123 . One such ramp is adjacent and extends from each lug receiving apertures  119  to the next aperture as seen in  FIG. 26 . In the embodiment of trimmer head  100  illustrated in the drawings, ramps  123  are configured such that they each extend along an arcuate path and at a downward inclination from a position laterally adjacent and slightly below the inner surface  126 ′ of the upper housing wall  126  so as to define vertical steps  119 ′ at the trailing sides of the lug receiving apertures. The ramps  123  then smoothly transition back into the inner surface  126 ′ of the upper housing wall proximate the next in line of the lug receiving apertures  119 . Thus, upon gripping the lower body portion  174 ′ of the spool  116  and rotating the spool in a counterclockwise direction while holding the trimmer head housing stationary, the drive lugs will translate from their respective apertures  119  in the upper wall of the trimmer head housing about steps  119 ′ onto and downwardly along the ramps to the inner surface  126 ′ of the upper housing wall and then upwardly under the force of the spring  122  into the next-in-line lug receiving apertures. Thus, continual rotation of the spool relative to the housing will provide the same ratcheting or reciprocal movement of the spool within the housing as described above in discussing the first embodiment of the invention. 
   The steps  119 ′ defined by the vertical spacing between the outer surface of the housing upper wall  126  and the upper ends of ramps  123  prevent any whipping or backlash in the line during use from causing a reverse rotation of the spool and inadvertent paying-out of line. Vertical steps of about 0.015 in.-0.025 in. in height have been employed for this purpose. To enable the drive lugs  121  to smoothly negotiate steps  119 ′ under manual rotation of spool  116 , the upper surfaces of the lugs (which are substantially flush with the upper surface of housing wall  126  in the drive position) are rounded at  121 ′. A radius of about 0.030 in. for surfaces  121 ′ has been employed. While ramps  123  vertically align the upper spool flange  170  and thus the line receptors  191  therein with the eyelets  178  when the drive lugs  121  are rotated off the ramps and onto the inner housing wall surface  126 ′, it may be preferable to size the spool  116  relative to the trimmer housing  114  such that the opposed line receptors would be radially aligned with the eyelets when the drive lugs  121  are disposed within lug receiving apertures. In either case, radial alignment between the receptors and eyelets is easily achieved. 
   Thus, as with the prior embodiment, the lengths of cutting line  17  are wound about the spool by pressing the extended ends of the line into the line receptors and rotating the spool relative to the housing as above described. As the spool is rotated, the lengths of line are bent acutely toward the inner portion of the spool as the line exits the receptor channels and is pulled against the flat lateral guide walls adjacent the channel outlets. As rotation of the spool continues, the spool reciprocates vertically with respect to the housing as a result of the drive lugs repeatedly moving along the downwardly inclined ramps and snapping upwardly into the next receiving aperture. As a result, the line is caused to be wound uniformly on the spool while avoiding line tangling as in the prior embodiment. 
   Finally, as in the prior embodiment, various changes in the configuration, number and sizes of the line receptors can be employed in the manual head  100  to provide the desired gripping of the line and accommodate different line sizes and, of course, the number of cutting lines extending from the cutting head. In addition, the orientation of the drive lugs  121 , apertures  119  and ramp  123  could be altered or reversed. For example, the drive lugs could be formed on the interior of the upper housing wall and the apertures and adjacent ramps could be formed in the upper surface of the spool. 
   A third embodiment of the present invention is illustrated in  FIGS. 32-44 . The trimmer head  200  shown therein is a bump-feed type head having the drive and line feeding mechanism disclosed in U.S. Pat. No. 4,959,904 but modified to include the rapid line loading feature of the present invention. As will be seen, trimmer head  200  primarily differs from the bump-feed head  10  of the first embodiment in that the cam, cam abutment and slide surfaces defined by the axially mounted cam member  18  and cam follower  20  in head  10  are molded directly into the spool and trimmer head housing in trimmer head  200 . 
   Trimmer head  200  comprises a housing  214 , spool  216 , coil spring  222  and drive bolt  224 . The housing comprises an upper portion  214   a  and a lower portion  214   b  that are releasably secured together about the spool. The trimmer head housing and spool are again preferably formed of the same material as the corresponding elements of the prior embodiments. The upper housing  214   a  defines an upper circular wall  226 , a cylindrical skirt  228  depending therefrom and a centrally disposed tubular extension  230 . Extension  230  is axially aligned with the central axis of rotation of the head and includes a depending portion  230   a  and an upwardly projecting portion  230   b . The tubular extension  230  is again configured to receive the drive bolt  224  with the upper portion  224   a  of the bolt being cylindrical in cross section and the lower portion  224   b  being hexagonal in cross section to mate with the hexagonal lower portion  230   a  of the tubular extension. The lower portion of the drive bolt and the tubular extension in the housing could also be square or otherwise configured to provide the desired interference fit between the drive bolt and housing. The drive bolt  224  is secured within the tubular extension  230  by heat shrinking the extension  230  about the bolt. An annular groove  224   e  is provided about the drive bolt to create an interference fit between the bolt and housing upon the shrinkage of the plastic housing material, to enhance the securement of the bolt to the housing. Other means for securing the drive bolt to the housing also could be employed. The drive bolt  224  also defines an internally threaded cylindrical bore  224   f  extending axially therethrough for threaded engagement with the drive shaft of the trimmer as in the prior embodiments. A second tubular extension  211  radially spaced from the depending portion  230   a  of extension  230  extends downwardly from the inner surface of the upper housing wall  226  to define at its lower end an upper annular seat  213  for the coil spring  222 . 
   The upper portion of housing  214  also defines a pair of opposed slots  277  in the depending cylindrical housing skirt  228 . As in the prior embodiment, the slots  280  are open at their lower ends and are adapted to receive a pair of opposed metal outlet eyelets  278  in a press fitment. Alternatively, the eyelets could be press fit through apertures in the housing skirt as in the first embodiment. Again, portions of the housing skirt adjacent the eyelets are preferably raised or ramped outwardly to protect the eyelets from foreign objects during use and a plurality of radially projecting heat dissipation ribs  215  are formed on the upper wall  226  of the upper housing. A plurality of equiangularly disposed and outwardly projecting radial tabs  233  also are provided at the lower end of the skirt  228  for the securement of the lower housing portion  214   b  to the upper portion  214   a  as will be described. 
   The upper wall  226  of the trimmer head housing has a raised central portion  227  so as to define an interior recessed area  229  therein. As shown in  FIG. 38 , the perimeter wall surface  231  extending about the recessed area  229  defines four equiangularly disposed projections  244  that project radially inwardly from wall surface  231 . Each of the projections defines a pair of angularly disposed surfaces  244 ′ that offset by 135° and are parallel to the axis of rotation of the head. These projections are similar in configuration, albeit larger, to the projections  56  on the cam follower  20  of the first embodiment. Here, however, these projections will define cam surfaces as opposed to cam abutment surfaces. 
   The leading surface on each of the projections  244  defines an upper cam  244   a  (counterclockwise rotation as seen from above). The trailing surfaces each define an upper slide surface  244   b . The surface of each of the cams is again parallel to the axis of rotation of the head. The upper slide surfaces  244   b  may be downwardly inclined, preferably radiused, particularly on smaller sized heads, to facilitate line loading as will be discussed. 
   The lower housing portion  214   b  of the trimmer head  200  defines an enlarged circular opening  235  in the underside thereof, an annular horizontal surface  237  disposed about opening  235 , and a plurality of equiangularly disposed slots  239  (four being shown) adjacent the upper surface  241  of the lower housing portion  214   b  for receiving a corresponding number of locking tabs  233  on the upper housing portion  214   a . Slots  239  are provided with narrow offset portions  239 ′ as seen in  FIG. 35  and at least one of the locking tabs  233   a  is mounted on a cantilevered portion  228 ′ of the housing skirt so as to be resilient such that upon inserting the rigid locking tabs  233  into three of the slots in the lower housing portion, pressing the resilient tab  233   a  radially inwardly and into the remaining aligned slot and rotating the upper portion of the housing counterclockwise with regard to the lower portion, the locking tabs will translate into the offset portions of the slots, releasably securing together the two housing portions. 
   The lower housing portion  214   b  further defines four equiangularly disposed projections  246  on the annular surface  237  adjacent opening  235  as seen in  FIG. 40 . The angularly disposed surfaces  246 ′ on projections  246 , like the surfaces  244 ′ in the projections  244  in the upper housing portion, define angularly disposed lower cams  246   a  and lower slide surfaces  246   b . The lower cams  246   a  are on the leading surfaces of the projections, extend parallel to the axis of rotation of the cutting head and again can be angled at 135° with respect to the adjacent slide surfaces. The slide surfaces  246   b  also can be radiused upwardly in the same manner as the slide surfaces  46   b  on the lower cam  46  in the first embodiment. In a preferred embodiment, however, the slide surfaces  246   b  on the lower projections  246  are not angled at 135° with respect to the cam surfaces  246   a  but at a lesser angle as seen in  FIG. 40  to accommodate a preferred ramping configuration on the leading sides of the lower cam follower which is defined by the spool as will be described. 
   The spool  216  in trimmer head  200  defines an upper flange  270  and a lower flange  272  carried by a cylindrical upper body portion  274  so as to define an annular area  276  between flanges  270  and  272  for carrying coils of flexible nylon cutting line  17  wrapped about body portion  274  such that upon assembly, the end portions  17 ′ of the cutting line will extend outwardly through the outlet eyelets  278 . A cylindrical chamber  243  is disposed about the central axis of rotation that is open at its upper end. An annular upstanding wall  245  is disposed in the lower end of chamber  243  so as to define an annular spring receiving area  247  and lower spring seat  247 ′. The lower body portion  275  of the spool terminates in a bumper  281  and a radial flange  249  extends outwardly from the lower spool body portion to prevent debris from becoming lodged between the spool  216  and the lower housing portion  214   b  (see  FIG. 36 ). When head  200  is assembled, the coil spring  222  extends about extension  230  and bears against and extends between the upper seat  213  formed by the upper housing portion  214   a  and the lower spring seat  247 ′ in the spool  216  as seen in  FIGS. 36 and 37 . The bumper  281  on the bottom of the spool projects through the opening  235  in the bottom of the lower housing portion  214   b  such that it can be bumped against the ground to pay out additional cutting line through the opposed eyelets  278  as in the first embodiment. 
   The upper flange  270  on spool  216  defines an upper cam follower  256  on its upper surface and the lower spool flange  272  defines a lower cam follower  257  on its lower surface as seen in  FIGS. 42-44 . While other configurations could be employed, both cam followers are preferably of a square configuration, defining four perpendicular surfaces  256 ′ and  257 ′ respectively, and are offset by 45° with respect to the central axis of rotation of the trimmer head. The cam abutment surfaces  256   a  and  257   a  defined by the trailing surfaces of the upper and lower cam followers are again parallel to the axis of rotation of the head. The leading surfaces of the lower cam follower which define sliding surfaces  257   b  may be inclined upwardly proximate the corners thereon so as to provide smoother ratcheting if needed. Also, the leading surfaces of the upper cam follower may also be inclined downwardly to facilitate line feeding. Such a downward inclination of the trailing edges  256   b  is believed to be particularly necessary on the smaller heads where the length of each of the cam follower surfaces is shorter which otherwise might make the relative rotation of the spool and housing during line winding more difficult. It may also prove desirable to incline the trailing surfaces of the upper and lower cams. 
   In the preferred configuration, the sliding surfaces  257   b  on the lower cam follower are defined by inclined ramps as seen in  FIGS. 34 ,  42  and  44  to provide a smoother ratcheting of the spool during the winding of the cutting line thereon due to the more gradual incline than that which would be provided by radiused surfaces. As noted earlier, the corresponding slides surfaces  246   b  on the projections  246  defined by the lower housing portion are inclined inwardly more sharply than the corresponding surfaces on the projections  244  on the upper housing portion  214   a  to provide more space adjacent the slide surfaces on the projections  246  to accommodate these inclined ramps on projections  224  when the spool  216  translates upwardly as occurs when the trimmer head is bumped against the ground to pay out fresh line and during the manual rotation of the spool to effect the winding of the cutting line thereon. 
   The operation of the bump-feed mechanism provided by the upper and lower cams and cam followers is explained in detail in the referenced U.S. Pat. No. 4,959,904. It should be noted, however, that the cam followers carried by the upper and lower spool flanges in head  200  are identified as upper and lower cams in the referenced patent and the upper and lower cams in head  200  are referred to as cam followers in the referenced patent. As explained in the cited reference in more detail, during use, the lower cams  246   a  on the lower housing portion  214   b  are aligned with and abut the lower cam abutment surfaces on the trailing surfaces of the lower cam follower  257 . Accordingly, as the housing is rotated in a counterclockwise direction by the trimmer drive, the spool is rotated with the housing. In this drive position, the upper cams  244   a  are upwardly spaced from upper cam follower  256  so that the driving force is generated solely by the lower cams. When the bumper  281  is pressed against the ground, the spool  216  is forced upwardly within the housing disengaging the lower cam abutment surfaces  257   a  on the lower cam follower from the lower cams  246  and bringing the upper cam abutment surfaces  256   a  on the upper cam follower  256  into alignment and immediate abutment with the upper cams  244   a  whereupon the driving force is effected solely by the upper cams. When the bumper  281  is lifted from the ground, the coil spring  222  forces the spool downwardly, disengaging the upper cam follower from the upper cams and re-engaging the lower cam follower with the lower cams. Thus, as with the first embodiment of the invention, with each bump on the ground effects a relative rotation of the spool and housing of 90° results, regardless of the duration of the bump. During this relative rotation, centrifugal force causes a predetermined amount of fresh cutting line to be paid out through the opposed eyelets  278  in the trimmer head housing. 
   To provide the rapid loading of the trimmer line about spool  216 , the upper spool flange  270  is provided with a pair of opposed line receptors  291  for gripping the inner end portion  17 ″ of two separate lengths of cutting line  17 . Spool  216  is sized and configured such that the upper flange  270  thereon is in planar alignment with the eye outlets apertures  278 . Each of the line receptors  291 , including the line receptor channels  293 , comprises the same configurations and functions in the same manner as the line receptors in the prior embodiments. Again, the dimensions may vary slightly depending on the variations in the sizes of the respective spools and the diameter or diameters of cutting line for which the head is designed. The cams, cam abutment surfaces and sliding surfaces described above cooperate in essentially the same manner as the cams, abutment and sliding surfaces in the first embodiment of the bump-feed head to effect the reciprocal movement of the spool within the housing to uniformly distribute the line on the spool. When the spool  216  is gripped by the bumper  281  and rotated in a counterclockwise direction relative to the housing, the lower slide surfaces  257   b  on the lower cam follower  257  will abut the trailing surfaces  246   b  on the lower projections  246  causing the spool to translate upwardly with respect to the housing, compressing the coil spring  222 . As the manual rotation of the spool continues, the corner portions of the lower cam follower  257  will ride over and clear the projections  246  in the lower portion of the housing whereupon the spring will cause the spool to snap downwardly such that the lower projections and lower cam abutment surfaces are again in planar alignment. Because the upper slide surfaces on the upper projections  244  and the leading (slide) surfaces  256   b  on the upper cam follower  256  are in abutment to wind the cutting line thereon at the very time the coil spring  222  will snap the spool  216  downwardly, it may prove desirable to incline the trailing surfaces  244   b  of the upper projections  244  and/or the leading (slide) surfaces  256   b  of the upper cam follower  256  to provide smoother rotation of the spool with respect to the housing during the loading of the line. 
   As noted in referenced U.S. Pat. No. 4,959,904, the bump-feed mechanism provided by the cams and cam abutment surfaces need not be limited to square cam followers (or cams as they are referred to in the referenced patent). The same is true of trimmer head  200 . The upper and lower cam followers formed the upper and lower spools, for example, could be three or five sided as shown in  FIGS. 12-15  of the referenced U.S. Pat. No. 4,959,904. Three and five sided cam followers would cooperate with an equal number of cam abutment members in the upper and lower housings as shown in the referenced drawings. The function, cooperation and operation of such cams and cam followers would be otherwise essentially unchanged from that described above and in the referenced patent. 
   Various changes and modifications also may be made in carrying out the present invention without departing from the spirit and scope thereof. For example, the spools employed with the present invention could be formed with a single flange and the line would be wound about the spool body between that flange and a portion of the housing. The line receptor or receptors would continue to be provided in the single flange. Insofar as these and other changes and modifications are within the purview of the appended claims, they are to be considered as part of the present invention.