as illustrated in fig1 - 3 , the present invention provides a light weight bump - feed type cutting head assembly 10 , for use on a flexible line trimmer , which is of a uniquely simple and inexpensive construction , and may be easily and rapidly assembled and disassembled by the trimmer user without the use of tools of any sort . in a manner subsequently described , the assembly 10 is threadingly secured to an end of the drive shaft 12 ( fig2 ) of a flexible line trimmer ( not illustrated ) and is rotationally drivable at a high speed about a central drive axis 14 . high speed rotation of the assembly 10 rapidly swings an outwardly projecting end portion 16 a of flexible cutting line 16 stored within the assembly 10 through a cutting plane transverse to axis 14 to perform the usual vegetation cutting function of the trimmer . as the whirling line portion 16 a becomes wear - shortened during trimmer operation , the assembly 10 ( as later described ) may be simply tapped downwardly against the ground by the trimmer operator to incrementally feed out additional cutting line and re - lengthen the operative line portion 16 a . the mechanical simplicity of the cutting head assembly 10 is best illustrated in fig5 wherein it may be seen that the entire assembly consists of only six components -- a housing 18 defined by an upper hub portion 20 and a lower cover member 22 , a threaded arbor 24 , a coiled cylindrical compression spring 26 , a line release button member 28 , and a line storage spool 30 . the hub 20 is of a molded plastic construction and has a hollow , generally cylindrical configuration , an upper end wall 32 , a generally annular side wall 34 , and an open lower end 36 . for purposes later described , two radially thickened circumferential portions 38 of side wall 34 are provided with a latching openings 40 , four locating recesses 42 are formed in the underside of a hub bottom flange 43 in a circumferentially spaced relationship with the latching openings 40 , and a circular opening 44 , having four radially outwardly projecting slot portions 45 , is formed axially through the upper end wall 32 . at 90 ° from the latching openings 40 , a line exit opening 46 ( fig3 and 5 ) is formed radially through one of two radially enlarged portions 47 of the hub side wall 34 , the line exit opening being fitted in the usual manner with a metal line guard eyelet or grommet 48 . as best illustrated in fig2 and 3 , an elongated annular support collar 50 extends axially downwardly from a central portion of the underside of the upper hub end wall 32 and has an open lower end 52 positioned somewhat below the open lower end 36 side surface of the support collar 50 , along an upper end portion thereof , are four circumferentially spaced webs 54 between which the slots 45 downwardly extend . also extending downwardly from the interior side surface of the upper hub end wall 32 is a cylindrical collar 58 which is shorter than and outwardly circumscribes the central collar 50 . the collar 58 has an open lower end 60 which is positioned at a generally central axial location within the hub 20 . for purposes later described , four circumferentially spaced , radially extending ribs 62 extend across the annular space between the collars 50 and 58 . the upper end of the collar 58 is circumscribed by an annular raised pad 59 . referring now to fig2 and 5 , the bottom cover member 22 is of a molded plastic construction and has an annular side wall 68 which extends upwardly from the periphery of an annular lower end wall 70 that slopes upwardly and radially outward . the side wall 68 is radially dimensioned to be axially received within the open lower end 36 of the hub 20 , and has formed around its periphery four circumferentially spaced , radially outwardly projecting locating lugs 72 , configured to be received in the hub locating recesses 42 , and two axially upwardly projecting , radially inwardly deformable latching tabs 74 having enlarged upper end portions 76 adapted to be releasably snapped into the latching openings 40 in the hub side wall 34 in a manner subsequently described . the lower end wall 70 of the cover member 22 is provided with a central circular opening 78 which is bordered , along the upper side surface of the lower end wall 70 , by an upstanding annular collar 80 . to rapidly install the cover member 22 within the lower end of the hub 20 , the cover member is pushed upwardly into the lower end opening 36 of the hub to its axial position shown in fig2 to cause the locating lugs 72 to enter the locating slots 42 , and cause the latching tabs 74 to pop outwardly into the latching openings 40 , thereby releasably locking the cover member remove the cover member 22 from the hub 20 , the cover member latching tabs 74 are simply pushed inwardly to permit axial travel of the cover member to disengage the latching tabs from their associated hub openings and permit axial removal of the cover member from the hub as illustrated in fig5 . the release button member 28 is of a molded plastic construction and has a tubular side wall 88 which is closed at its lower end by a bottom end wall 90 . formed downwardly through an upper end portion of the side wall 88 are four circumferentially spaced , axially extending slots 92 which terminate at their lower ends at four rectangularly cross - sectioned tooth members 94 a , 94 b , 94 c and 94 d projecting radially outwardly from the release button side wall 88 . the exterior diameter of the release button side wall 88 below these teeth is sized to be downwardly and slidably received within the central opening 78 of the lower end wall 70 of the cover member 22 , and the inner diameter of the release button side wall is sized to slidably receive the central support collar 50 of the hub 20 . extending upwardly from a central portion of the release button end wall 90 is a spring support structure 96 defined by eight circumferentially spaced rib members 98 extending radially outwardly from the bottom end of a hollow cylindrical post member 100 having three circumferentially spaced slots 102 formed in its upper end . the spool 30 is of a molded plastic construction and has a hollow , open - ended cylindrical hub portion 104 with an interior side surface 106 . positioned axially inwardly of the upper and lower ends of the hub 104 , and projecting radially outwardly therefrom , are annular upper and lower spool flanges 108 and 110 which define with the hub 104 a cutting line storage cavity 112 within which the flexible cutting line 16 may operatively wound as best illustrated in fig2 . a circumferentially spaced series of radially extending stiffening ribs 114 are formed on the outer side surface of the spool flange 108 as illustrated in fig2 and 5 . as illustrated in fig2 a lower end portion of the spool hub 104 is provided with a radially outwardly projecting annular lip 110 which allows easy gripping when removing and installing the spool on the hub . referring now to fig2 - 4 , two circumferentially spaced series of radially inwardly directed , rectangularly crosssectioned teeth 120 a - 120 d and 122 a - 122 d are formed on the interior side surface 106 of the spool hub 104 . as will be subsequently described , these eight interior spool teeth cooperate with the four release button teeth 94 a - 94 d to form an escapement mechanism which , in response to tapping the release button 28 against the ground during trimmer operation , creates an incremental payout of cutting line 16 through line exit opening 46 to relengthen the operative outer line end portion 16 a . the lower spool teeth 120 a - 120 d are axially positioned adjacent the bottom end of the spool hub 104 and are downwardly and circumferentially offset from the upper spool teeth 122 a - 122 d . to assemble the cutting head assembly 10 from its fully disassembled state illustrated in fig5 an enlarged upper end portion 24 a of the threaded arbor 24 is press - fitted upwardly into the hub opening 44 , as illustrated in fig2 so that radially projecting ribs 24 b on the arbor portion 24 a enter the over the upper end 100 of the spring support post 100 within the interior of the release button member 28 , so that the spring 26 abuts the ribs 98 within the release button 28 . the release button 28 is then pushed upwardly onto the central hub collar 50 to cause entry of the hub ribs 62 into the axial slots 92 in the release button 28 . the release button is then firmly pushed in an upward direction to compress the spring 26 and drive its cylindrical post 100 over a radially enlarged lower end portion 24 c of arbor 24 , thereby frictionally intersecuring the release button to the arbor and causing the spring 26 to be captively retained within the release button , with the upper and lower spring ends respectively engaging the bottom of the arbor portion 24 a and the release button ribs 98 . the release button is then released to permit the spring 26 to return to its almost uncompressed state . the frictional engagement between the lower arbor end and the inner side surface of the release button releasably holds the button member 28 on the hub collar 50 , and the hub ribs 62 prevent relative rotation between the release button 28 and the hub 20 about the drive axis 14 . however , the release button slots 92 permit the release button 28 to be axially moved relative to hub 20 between the downwardly extended release button member position shown on the left side of fig2 and its upwardly retracted position shown on the right side of fig2 . the interengagement between the arbor 24 and the inner side surface of the release button , while sufficient to hold the release button on the hub collar 50 before the bottom cover than the frictional engagement between the arbor and the hub . accordingly , when it is desired to remove the release button from the hub collar 50 , the release button is simply pulled downwardly to disengage release button from the arbor , the removed release button permitting the spring to be loose . after the release button 28 is operatively positioned on the hub collar 50 and frictionally retained thereon , the release button is inserted downwardly into the interior of the spool hub 104 , and the line end portion 16 a is threaded outwardly through the line exit opening 46 in the hub 20 . the spool 30 , with its teeth 94 a - 94 d circumferentially positioned between the spool teeth sets 120 a - 12 d and 122 a - 122 d as illustrated in fig3 is then pushed upwardly into the interior of hub 20 so that the hub collar 58 is slidably received within the interior of the spool hub 104 . finally , the bottom end of the release button is inserted into the central opening 78 of the cover member 22 , the cover member side wall 68 is pushed into the interior of the hub 20 , and the cover member is pushed into the hub to lock the cover member in place as previously described . the installation of the cover member 22 pushes the release button 28 upwardly to its extended operating position and slightly compresses the spring 26 . with the cover member 22 releasably latched in place in this manner , the installed spool 30 is restrained against appreciable axial movement relative to the housing 18 by the slidable axial engagement between the hub abutment ribs 64 and the upper end of the spool hub 104 , the slidable axial engagement between the lower end 60 of the hub collar 58 and the upper spool teeth 122 a - 122 d , and the slidable axial engagement of the annular cover member collar 80 and the cover member ribs 82 with the lower spool teeth 120 a - 120 d and the lower end of the spool hub 104 as best illustrated in fig2 . with the cover member 22 in its installed position illustrated in fig2 the engagement between compresses the spring 26 , brings the release button teeth 94 a - 94 d into vertical alignment with the lower interior spool teeth 120 a - 120 d . the assembled cutting head 10 may be screwed directly onto the bottom end of the drive shaft 12 as illustrated in fig2 the drive shaft 12 extending downwardly into the upper hub opening 44 and being threadingly received within the press - fitted retaining arbor 24 . high speed rotation of the cutting head portion 16 a a centrifugal line payout force which exerts a counterclockwise rotational force on the spool 30 as indicated by the arrow 124 in fig3 . however , with the release button member 28 in its downwardly extended operatively position as shown on the side of fig2 counterclockwise rotation of the spool is prevented by the respective engagement of the release button teeth 94 a - 94 d with the lower interior spool teeth 120 a - 120 d . the spool rotation - preventing abutment between the representative release button teeth 94 a and 94 b with the lower interior spool teeth 120 a and 120 b is schematically illustrated in fig4 . during operation of the line trimmer , when the outer line end portion 16 a becomes wear - shortened , the trimmer operator simply taps the lower end of the release button member 28 against the ground to move the release button upwardly to its retracted position . upward movement of the release button to its retracted position shifts the release button teeth 94 a - 94 d upwardly out of abutting engagement with the lower interior spool teeth 120 a - 120 d . this upward shift of the release button teeth is shown in fig4 in which , during the downward portion of the release button ground tap , the representative release button teeth 94 a and 94 b are shifted upwardly to the dashed line positions thereof . disengagement of the release button teeth from the lower interior spool teeth permits the centrifugal line payout force in the outer line end portion 16 a to rotate the spool 30 in a counterclockwise direction until , as illustrated in fig4 a , the upper interior spool teeth 122 b and 122 c are brought into abutment with and stopped by the now upwardly shifted release button 1 teeth 94 a and 94 b . at this point , of course , the other two release button teeth are also engaged by and stop the other two upper interior spool teeth . when the release button is lifted from the ground , the spring 26 downwardly returns the release button to its extended position as representatively indicated by the dashed line positions of the release button teeth 94 a and 94 b in fig4 a . this downward shifting of the release button teeth permits the centrifugal line payout force in the outer line end portion 16 a to once again cause counterclockwise rotation of the spool 30 until the lower interior spool teeth 120 b and 120 c are brought into abutment with and are stopped by the now downwardly shifted release button teeth 94 a and 94 b as illustrated in fig4 b . thus , in response to a single tap and release of the button member 28 , two discrete increments of cutting line are centrifugally payed out through the line exit opening 46 , the total line payout increment resulting from a quarter turn of the spool 30 in a counterclockwise direction as viewed in fig3 . additional quarter spool turn line payout increments may be selectively achieved simply by tapping the release button on the ground an appropriate number of additional times . to replace the spool 30 , or to refill it with flexible cutting line , all that is necessary is to radially inwardly depress the cover member tabs 74 , axially remove the cover member from hub 20 , and slide the spool downwardly off the release button member 28 which remains frictionally secured to the hub 20 as previously described . simply stated , no other parts need to be removed from the cutting head assembly , and no other parts are free to fall off the hub 20 when the cover member is removed . the balance of the assembly remains in a fully assembled and operative state . all that is necessary to ready the assembly for subsequent trimming use is to reinstall the cover member and a line - filled spool . compared to the relatively complex , multi - piece constructions of conventional bump - feed type cutting head assemblies , the cutting head 10 of the present invention advantageously provides a significantly simplified construction which is much easier for the typical trimmer user to handle when it becomes necessary to replace a depleted supply of cutting line . no tools of any sort are required for even complete disassembly and reassembly of the cutting head . this simplicity , of course , also provides a variety of operational and manufacturing advantages . for example , because there are only six components in the assembly 10 its overall material cost and weight is significantly reduced , thereby permitting its manufacturing cost to be correspondingly diminished . also , due to this weight reduction the rotational inertia of the cutting head is desirably reduced so that , for a given rotational velocity of the head , less driving power is required . this rotational inertia reduction is further enhanced by the fact that the lower cover member is received within the upper hub and does not increase the overall diameter of the assembly . the mechanical simplicity of the cutting head assembly 10 also reduces its initial fabrication cost since there are only six components which may be rapidly put together at the factory without ( except for the installation of the line guard eyelet and the press - fitting of the threaded arbor into the hub ) the use of special tools of any sort . the foregoing detailed description is to be clearly understood as being given by way of illustration and example only , the spirit and scope of the present invention being limited solely by the appended claims .
a compact , light weight , structurally simplified bump - feed type cutting head for a flexible line trimmer is formed from only six components -- a hollow cylindrical hub having an open lower end ; an annular cover member releasably securable over the lower hub end ; a threaded arbor press - fitted into the hub to secure it to the trimmer drive shaft for rotation therewith ; a hollow tubular release button member slidably extended through the central cover member opening and axially movable between downwardly extended and upwardly retracted positions ; a line storage spool rotatable carried by the release button member within the hub ; and a cylindrically coiled compression spring captively retained within the release button and biasing it toward its downwardly extended position . during high speed rotation of the hub about its axis , an outer end portion of flexible line coiled on the spool and passing outwardly through a hub side aperture is whirled through a transverse cutting plane to trim adjacent vegetation . when the outer line end becomes worn away , incremental line feedout is achieved simply by tapping the release button on the ground to activate a line escapement structure defined by cooperating teeth formed on the release button and the inner side surface of the spool hub . spool removal is achieved simply by removing the cover member , the arbor functioning to hold the release button in place on the hub during and after spool removal .