Abstract:
Disclosed and taught is a novel drive mechanism for a cyclic operating tool employing an energized flywheel to provide the necessary energy to perform a working cycle. The drive mechanism disclosed is particularly useful in hand tool applications such as a hand held nailing machine. The flywheel may be energized by a corded or battery powered motor. The herein disclosed mechanism teaches a novel pair of ball ramp cam plates wherein a first pair of ball ramps cause an initial engagement of a clutch with the energized flywheel whereupon rotation of the clutch causes activation of a second pair of ball ramps which affect compression of a spring which acts to increase the pressure applied to the clutch thereby assuring a slip free engagement between the clutch and he flywheel throughout the working cycle of the drive mechanism. Upon completion of the drive mechanisms working cycle, the second pair of ball ramp cam plates further act to disengage the clutch from the flywheel whereby the flywheel may dissipate the unused kinetic energy remaining within the flywheel as the drive mechanism returns to the start position.

Description:
RELATED PATENT APPLICATIONS 
     This application claims the priority of Provisional Patent Application serial No. 60/258,022, filed on Dec. 22, 2000 and incorporates herein, by reference, the totality of the invention disclosure therein. 
     This application is related to copending U.S. patent applications titled, “Speed Control For Flywheel Operated Hand Tool” and “Control Module For Flywheel Operated Hand Tool” both filed simultaneously with the present application by Shane Adams et al. and are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The herein disclosed and taught invention generally relates to a cyclic operating tool employing an energized flywheel to provide the necessary energy to perform a working cycle. 
     More specifically the invention disclosed herein relates to, but is not necessarily limited to, a hand held electromechanical fastener driving tool, such as a fastener driving tool having an electrically powered motor energizing a flywheel which provides the necessary kinetic energy to drive a fastener into a work piece. The electrical power may be provided by either a battery or an AC electrical power source. 
     In the past, where relatively large energy impulses have been required to operate a fastener driving tool, such as an industrial nailer or stapler, it has been a common practice to power such tools pneumatically or by a corded electric motor. Such tools are capable of driving a 3″ or longer nail, or staple, into framing wood such as 2×4s, for example. 
     However, pneumatic driving tools require an on-site air compressor, and corded electric tools require an on-site source of electrical power. Further both type of tools require the user to drag a pneumatic or electrical umbilical behind them during use. Dragging such an umbilical behind becomes particularly troublesome when working in high places such as upon a roof or a ladder. 
     Electrically driven tools, such as solenoid operated fastener driving tools, are also well known. These are primarily used in lighter duty applications such as in driving one inch brad nails, for example, rather than the larger 1.25 to 2.5, 15 gauge finishing nails and/or heavier framing nails. 
     Also much effort has been expended in the prior art for providing a heavy duty, high powered, fastener driving tool employing a flywheel as a means to deliver kinetic energy sufficient to power a heavy duty fastener driver. Examples of such systems are disclosed in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,204,622, 4,298,072 and 5,511,715. However, the referenced prior art requires the use of corded electric motors to provide the energy necessary to energize the flywheels. 
     SUMMARY OF THE INVENTION 
     The present invention discloses and teaches a novel drive mechanism particularly useful in a cyclic hand tool, which has an operative work cycle followed by a reset cycle such as a powered nailing machine. More particularly the present invention is useful in a cyclic tool employing the kinetic energy of an energized flywheel to provide the necessary energy to perform the tool&#39;s operative working cycle. 
     A drive mechanism is taught whereby a first pair of rotatable caming plates, activated by an electrical solenoid, cause a clutch assembly to engage an energized flywheel. Upon engagement of the flywheel by the clutch a second pair of rotatable caming plates, activated by the flywheel, affect the compression of a spring whereby additional force is imposed upon the clutch ensuring slip free engagement during the following operative work cycle of the drive mechanism. Upon completion of the mechanism&#39;s operative work cycle, the second pair of caming plates affect a rapid disengagement of the clutch from the flywheel whereby the drive mechanism returns to its start position and the flywheel dissipates its remaining energy by free wheeling until it stops or until it is re-energized for an additional work cycle. 
     Although the following embodiment describes the present invention as used in a hand held, battery powered, nailing machine, it is to be understood that the invention may also be used in a corded electric motor embodiment. Further it is to be understood that the present invention is also suitable for applications, other than hand held tools, where a cyclic operation, similar to that of a hand held nailing machine, is desired. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 presents a left side elevational view of a hand held nailing machine, embodying the present invention, having a portion of its left side removed to show the general positioning of the driving mechanism within the tool&#39; outer shell. 
     FIG. 2 presents a top view of the fastener drive assembly removed from the main body of the hand held nailing machine as illustrated in figure. 
     FIG. 3 presents a left side elevational view of the fastener drive assembly as removed from the nailing machine illustrated in FIG.  1 . 
     FIG. 4 presents a bottom view, looking upward from the handle of the fastener drive assembly as removed from the nailing machine outer shell illustrated in FIG.  1  and having the electrical control module removed for clarity. 
     FIG. 5 presents an end elevational view of the fastener drive assembly as removed from the nailing machine illustrated in FIG.  1  and having the electrical control module removed for clarity. 
     FIG. 6 presents a pictorial view of the fastener drive assembly, having the electrical control module removed for clarity, showing the general arrangement the clutch drive assembly components. 
     FIG. 7 presents an exploded pictorial view showing the components of the fastener drive assembly illustrated in FIGS. 2 through 6. 
     FIG. 8 presents a sectional view taken along line  8 — 8  in FIG.  3 . 
     FIG. 9 presents a sectional view taken along line  9 — 9  in FIG.  4 . 
     FIG. 10 presents an enlarged view of the circled section in FIG.  8 . 
     FIG. 10A presents a first alternate embodiment of the circled section of FIG.  8 . 
     FIG. 10B presents a second alternate embodiment of the circled section of FIG.  8 . 
     FIG. 11 is a sectional view taken along line  11 — 11  in FIG.  4 . 
     FIG. 12 is a sectional view taken along line  12 — 12  in FIG.  4 . 
     FIGS. 13A through 13C present a schematical presentation of the ball/cam action between the fixed plate an the activation plate. 
     FIG. 14 presents a graph showing the distance x between the fixed plate and the actuation plate as a function of degrees of rotation of the actuation plate. 
     FIG. 15 presents an expanded pictorial view of the solenoid camming plates. 
     FIG. 16 presents an expanded pictorial view of the activation camming plates. 
     FIG. 17 is a crossectional view taken along line  17 — 17  in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although the following description of the present invention teaches a hand tool powered by a removable battery it is to be understood that the hand tool may also be powered by a corded AC electric motor in place of the battery powered DC motor described herein. 
     FIG. 1 illustrates a hand held nailing machine  10  generally comprising a main body  12  including and a gripping handle  14 . Attached to the end of handle  14  is removable, rechargeable battery  19  for providing the necessary electrical energy to operate the nailing machine power drive mechanism. Also included in handle  14  is trigger  16  for operating nailing machine  10 . A fastener supplying magazine assembly  18  is typically attached to main body  12  and handle  14 , as illustrated, for supplying a strip of fasteners to nose assembly  20 . 
     FIGS. 2,  3 ,  4 , and  5  illustrate top, left side, bottom and rear views of fastener drive assembly  40  as positioned within housing  12  of nailing machine  10  illustrated in FIG.  1 . FIGS. 2,  4 , and  5  have electrical control module  25  removed for clarity. The structural details and operation of control module  25  is completely described within the two copending patent applications identified in the “Related Patent Applications” section above and are incorporated herein by reference. 
     As illustrated in FIG. 6 the primary operational elements of fastener drive assembly  40  comprise a flywheel  45  for providing kinetic energy, for driving a fastener into a work piece, energized by an electric motor  42 . Flywheel  45  is free wheeling upon fixed shaft  32 . Upon achieving the required revolutions per minute (RPM), drive clutch assembly  30  (see FIGS. 7 and 9) causes engagement of clutch  35  and flywheel  45  thereby transferring a portion of the kinetic energy of flywheel  45  to a linearly moving driver  106  for driving a fastener into a work piece. 
     Referring now to FIGS. 2, through  9 , the elements and operation of the flywheel drive assembly  40  will be discussed. The flywheel drive assembly comprises clutch drive assembly  30  and flywheel  45  gear driven by electric motor  42 . Although a gear drive between motor  42  and flywheel  45  is primarily illustrated herein, it is understood that a belt drive may also be used between motor  42  and flywheel  45  or any other suitable drive mechanism. As an alternative to having the motor axis of rotation parallel to the axis of rotation of flywheel  45 , as illustrated herein, it may be preferable to position motor  42  such that its axis of rotation is perpendicular to the axis of rotation of flywheel  45  and shaft  32 , thereby employing a bevel gear drive between the motor output shaft and the flywheel periphery. 
     Referring particularly to FIG.  9  and additionally to FIGS. 6 through 8 the mechanical structure of flywheel  45  and clutch drive assembly  30  will be operationally described. 
     Clutch drive assembly  30  and flywheel  45  are axially aligned upon central shaft  32  as best illustrated in FIG.  9 . Central shaft  32  is threadingly affixed to end plate  52  which in turn is rigidly attached to frame  48  by an integral boss  51  extending axially from endplate  52  and received within slotted groove  47  such that end plate  52  and central shaft  32  are non-rotatable. The opposite end of central shaft  32  is received within supporting groove  49  in frame  48 . 
     Flywheel  45  is rotatingly positioned at the end of central shaft  32 , as best illustrated in FIG. 9, upon deep groove ball bearing  46 , whereby flywheel  45  freely rotates about central shaft  32  when energized by motor  42 . 
     Flywheel  45  includes a conical cavity  44  for receiving therein conical friction surface  36  of conical clutch plate  35 . Clutch plate  35  and activation plate  58 , although they are separable members, are geared to drum  34  by interlocking projections  28  and  26  respectively, whereby clutch plate  35 , activation plate  58  and drum  34  rotate freely about shaft  32  as a single unitary assembly. Roller bearings  38 A and  38 B, positioned on the inside diameter of drum  34 , are provided to assure the free rotational characteristic of activation plate  58 , drum  34  and clutch plate  35  as a unitary assembly. 
     Adjacent activation plate  58  is fixed plate  56 . Fixed plate  56  and activation plate  58  are connected to one another by three equally spaced axially expandable ball ramps  66 A,  66 B,  66 C,  66 A′,  66 B′ and  66 C′ as illustrated in FIG.  16 . The operation of the ball ramps  66  between fixed plate  56  and activation plate  58  is described in greater detail below. Fixed plate  56  is fixed to housing  48  such that fixed plate  56  is free to move axially upon central shaft  32 , but not free to rotate about shaft  32  by anti-rotation tang  53  slidably received within axially aligned slot  43  within frame  48 . See FIG.  17 . 
     Fixed plate  56  includes circular projection  61  receiving thereon freely rotatable thrust bearing  62  positioned between fixed plate  56  and retarder plate  64 . A pair of nested, parallel acting, bellville springs  72  are positioned, as illustrated in FIG. 9, between retarder plate  64  and solenoid plate  54  the function of which is described in greater detail below. Axially expandable ball ramps  68 A,  68 B,  68 C,  68 A′,  68 B′ and  68 C′, see FIG. 15, connect end plate  52  and solenoid plate  54  the function of which is also described in greater detail below. 
     Positioned upon central shaft  32 , between clutch  35  and flywheel  45  is compression spring assembly  37  comprising washers  73  and  74  having coil spring  75  therebetween the function of which is described in further detail below. 
     Upon start of the fastener work, or driving, cycle, control microprocessor  25  causes motor  42  to “spin up” flywheel  45 , in the counter clockwise direction as indicated by arrow A in FIG. 7, to a predetermined RPM. Upon flywheel  45  achieving its desired RPM, or kinetic energy state, the control microprocessor  25  activates solenoid  80  which, through a flexible wire cable  84  extending from the solenoid plunger  82  and affixed to the periphery of solenoid plate  54  causes solenoid plate  54  to rotate clockwise, as indicated by arrow B in FIG.  7 . As solenoid plate  54  rotates clockwise, solenoid plate  54  is caused to move axially away from end plate  52  by action of the corresponding ball ramps  68  in end plate  52  and solenoid plate  54 . See FIG.  15 . As end plate  52  and solenoid plate  54  axially separate, the remaining elements of clutch drive assembly  30  are thereby caused to move axially toward flywheel  45  compressing coil spring  75  whereby clutch surface  36  preliminarily engages flywheel cavity  44 . Engagement of clutch  35  with flywheel  45  causes counter clockwise rotation of clutch  35 , drum  34  and activation plate  58 , as an assembly. By action of corresponding ball ramps  66 , between fixed plate  56  and activation plate  58 , see FIG. 16, rotation of activation plate  58  causes axial separation of plates  53  and  58 . Bellville springs  72  are thus compressed against solenoid plate  54  thereby providing an opposite axial force, forcing clutch  35  into tighter engagement with flywheel  45 . Upon sensing an RPM drop of flywheel  45 , the control microprocessor  25  shuts off solenoid  80 , whereby solenoid plate  54  begins to return to its reset position by action of the axial force applied by the compressed belleville springs  72 . As solenoid plate  54  is urged to its start position the combined inertia of solenoid plate  54 , Belleville springs  72 , compressed between solenoid plate  54  and retarder plate  64 , and retarder plate  64  prevent solenoid plate  54  from bouncing as it returns to its start position and engages the end of ball tracks  68 A,  68 B, and  68 C. By the presence and action of retarder plate  64  the system is prevented from oscillating and possibly re-engaging the clutch accidentally. 
     As drum  34  rotates counter clockwise, cables  102 A and  102 B wrap about peripheral grooves  57  and  60  in drum  34  and clutch  35  respectively, thereby drawing piston assembly  111  downward, within cylinder  110 , in a power, or working, stroke whereby the attached fastener driver  106  is likewise driven downward, through guide block  108 , opening  41  within housing  48 , and into nose piece  20  thereby driving a selected fastener into a targeted workpiece. As piston assembly  111  is drawn downward through cylinder  110  a vacuum is created above piston assembly  111  which serves to draw piston assembly back to its start position upon completion of the work cycle thereby resetting the tool drive mechanism to its start position. assembly back to its start position upon completion of the work cycle thereby resetting the tool drive mechanism to its start position. 
     FIGS. 13A through 13C sequentially illustrate the action between fixed plate  56  and activation plate  58  as plate  58  rotates during the power stroke of clutch drive assembly  30 . Although ball ramps  66  of fixed plate  56  and activation plate  58  are helical as illustrated in FIG. 16, ramps  66  are illustrated as being linear in FIGS. 13A through 13C for simplicity of explanation. 
     FIG. 13A illustrates fixed plate  56  and activation plate  58  at the beginning of the tool&#39;s work cycle. As flywheel  45  drives activation plate  58  counter clockwise (to the left in FIG. 13A) balls  63 , following ramp profile  66 , cause a fast and sudden separation x, between activation plate  58  and fixed plate  56  as illustrated in FIG.  13 B. Separation x is maintained throughout the power stroke of driver  106 , as illustrated in FIG. 13B, thereby affecting the impartion of the kinetic energy, stored within flywheel  45 , to driver  106  as described above. At the end of the power stroke, as illustrated in FIG. 13C, plates  56  and  58  suddenly close together thereby causing the rapid disengagement of clutch  35  from flywheel  45 . With the solenoid plate  54  returned to its starting position and clutch  35  disengaged from flywheel  45 , activation plate  58 , drum  34  and clutch  35 , as an assembly, may be returned to their start position as described below. 
     FIG. 14 presents a representative graphical plot of the separation x between activation plate  58  and fixed plate  56  as a function of the angle of rotation of activation plate  58 . 
     A combination driver guide and resilient stop block  108  is preferably positioned at the bottom of cylinder  110  to stop piston assembly  111 , within cylinder  110 , at the end of the power stroke. 
     Upon disengagement of clutch  35  from flywheel  45 , coil spring  75  urges all elements of clutch drive assembly  30  back toward end plate  52  whereby the vacuum formed above piston assembly  111  draws piston assembly back to its start position and thereby rotating activation plate  58 , drum  35  and clutch  34   
     By constructing the clutch drive assembly  30 , as taught hereinabove, clutch  35  disengages from flywheel  45  thereby allowing flywheel  45  to continue spinning after drive assembly  30  has reached the end of its power stroke. Thus in the event it is desired to successively drive additional fasteners, the remaining kinetic energy is available for the subsequent operation thereby economizing battery power and saving the drive assembly elements and/or the frame  48  from having to absorb the impact that would otherwise occur by bringing flywheel  45  to a full stop immediately after the power stroke. This feature also permits “dry firing” of the tool. 
     The clutch drive system as taught herein also provides for automatic compensation for clutch wear in that the expansion between end plate  52  and solenoid plate  54  will continue until clutch  35  engages flywheel  45  thereby allowing solenoid plate  54  to take up the difference at the start of every power drive. 
     Referring now to FIG.  10 . Vacuum return piston assembly  111  comprises piston  112  slidably received within cylinder  110 . Spaced from the top of piston  112  is circumscribing groove  113  having positioned therein sealing O-ring  114 . Positioned toward the bottom of piston  112  are two axial stabilizing bands  115  and  116 . 
     The inside diameter D, of cylinder  110 , is flared outward to diameter D′ at the top of cylinder  110  as illustrated in FIG.  10 . Diameter D′ is slightly greater than the outside diameter of O-ring  114  thus creating an annular gap  117  between O-ring  114  and inside diameter D′. 
     As piston assembly  111  is drawn axially into cylinder  110 , during the power stroke of driver  106 , O-ring  114  slidingly engages the inside wall diameter D of cylinder  110  thereby forming a pneumatic seal between inside wall  118  of cylinder  110  and piston assembly  111 . As piston assembly  111  progresses into cylinder  110 , a vacuum is created, within the top portion of cylinder  110 , between advancing piston assembly  111  and the sealed end cap  119 . 
     Upon disengagement of friction clutch  35  from flywheel  45 , the vacuum created within the top portion of cylinder  110  draws piston assembly  111  back toward end cap  119  thereby resetting activation plate  58 , drum  34 , and clutch  35 , as an assembly, to their restart position. 
     As O-ring  114  passes from inside diameter D to diameter D′, on its return stroke, any air that may have by passed O-ring  114 , during the power stroke, is compressed and permitted to flow past O-ring  114  through annular gap  117  and to the atmosphere through cylinder  110 , thereby preventing an accumulation of entrapped air above piston assembly  111 . A resilient end stop  120  is preferably positioned within end cap to absorb any impact that may occur as piston assembly  111  returns to its start position at the top of cylinder  110 . 
     As drum  34  returns to its start position tang  33  radially extending from drum  34  engages abutment block  31  affixed to housing  48 , see FIG. 11, thereby preventing over travel of drum  34  as it returns to its start position. 
     FIG. 10A illustrates an alternate embodiment for preventing an accumulation of trapped air above piston assembly  111 . As illustrated in FIG. 10A piston  112  includes circumferential groove  132  receiving therein a generally rectangular shaped seal  134  having a V shaped groove  136  in one laterally positioned side thereof. One leg  133  of V groove  136  extends laterally outward beyond the outside diameter of piston  112  as illustrated in FIG.  10 A. Thus seal  134  acts as a check valve such that as piston  112  moves downward, during a power stroke, leg  133  sealing engages the inside wall  118  of cylinder  110  preventing the passage of air past piston  112  thereby creating the desired vacuum above piston  112 . In the event a small accumulation of air does accumulate above piston  112 , compression of that air accumulation upon return of piston  112  to its start position at the top of cylinder  110  will cause the air accumulation to flow past seal  134  thereby preventing a compressive air lock above piston  112 . 
     Although the two embodiments described immediately above are preferred embodiments to prevent the accumulation of entrapped air above piston assembly  111 , any other known suitable check valve mechanism may be used whereby entrapped air is permitted to escape to the atmosphere upon return of piston assembly  111  to its start position and wherein a vacuum is created during the power stroke of piston assembly  111 . 
     For example see FIG. 10B wherein the check valve type of annular seal  134 , of FIG. 10A, has been replaced by a typical sealing O-ring  138  and a simple flap type check valve  130  which will permit entrapped air to be exhausted from orifice  131  during return of piston  112  to its start position. 
     Since the power stroke is relatively fast acting with a rapid return of piston assembly  111  to its start position, it is possible to eliminate check valve flap  130  and size orifice  131  such that the small amount of air that enters the cylinder during the power stroke does not sufficiently affect the resulting vacuum whereby sufficient vacuum remains to return piston assembly  111  to its start position and the air that has accumulated between piston assembly  111  and end cap  119  is exhausted through orifice  131  as piston assembly  111  returns to its start position. 
     Having shown and described the preferred embodiments of the present invention, further adaptation of the method and structure taught herein may be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the present invention. Accordingly, the scope of the present invention should be considered in terms of the following claims and is understood not to be limited to the specific structures and methods described in the specification and/or shown in the attached drawings.