US 3088445 A
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Description (OCR text may contain errors)
May 7, 1963 H. R. GARDNER PORTABLE, REVERSIBLY OPERATED, POWER-DRIVEN TOOL Filed April 11, 1960 2 Sheets-Sheet 1 Harold R. Gardner INVENTOR.
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May 7, 1963 H. R. GARDNER 3,088,445
PORTABLE, REVERSIBLY OPERATED, POWER-DRIVEN TOOL Filed April 11, 1960 2 Sheets-Sheet 2 H a r'old R. Gardner IN V EN TOR.
United States Patent 3fi83i45 Patented May 7, 1953 3,088,445 PORTABLE, REVERSKBLY OPERATED, POWER-DRIVEN TQGL Harold R. Gardner, 1551 S. Toutle Road, Toutle, Wash. Filed Apr. 11, 1960, Ser. No. 21,207 6 Claims. (til. 123--41) This invention relates to portable, power-driven tools, and more particularly to power-driven tools with rotating, reversible work elements, i.e., elements that in performing work are adapted to be rotated in either of opposite directions.
A general object of this invention is to provide an improved construction for a portable, power-driven tool that comprises an internal combustion engine or motor (as a source of power) and a novel construction for the motor and its connection with a reversible work element whereby reversible operation of the work element may be obtained.
Portable power tools in many types of applications make a job considerably easier, and substantially increase a workmans output. While their advantages are obvious, certain factors have tended to restrict universal acceptance of such tools. For instance, a common form of such tool is the impact wrench, used to tighten or loosen screw connections. The usual impact wrench has an electric motor for driving it. Such a tool is light and easy to handle, but the electric motor requires that a source of electric power be available, or, if such is not available, that some form of portable electric generator be used. The latter are costly and relatively heavy pieces of equipment, and consequently potential users whose work is highly mobile have often had to rely on manually operated wrenches. Wrenches driven by an internal combustion engine are known, but such have used reversing transmissions to obtain reversible operation, and their constructions have tended to be massive and expensive.
It is another object of this invention, therefore, to provide an improved construction for a reversible, powerdriven tool which comprises an internal combustion engine for a power source, means directly and devoid of any reversing transmission connecting the shaft of the engine to the work element of the tool, and a construction for the engine wherein the running direction of the engine may be quickly and readily reversed to reverse the direct-ion of rotation of the work element. A tool constructed according to this invention is relatively inexpensive to make, is light, and may be constructed with a drive train extending in a straight line from the engine to the work element. Thus the tool is easy to manipulate, set in operating position, and run.
A related object is to provide a portable power tool with an internal combustion engine drive that employs means for running the engine in opposite directions to effect reversing of the work element, wherein such means enables efficient reverse operation automatically, i.e., reversing may be accomplished without any adjustment required in the motor parts. According to this invention, an engine may be constructed to reverse automatically on temporarily stalling the engine once it is running in one direction, relying on backlash to provide the momentum needed to start reverse running. The firing system for the engine contemplated permits the engine to be run in either of opposite directions with efiicient operation resulting regardless of the direction.
Another object is to provide a magneto firing system for a reversible engine for firing the engine, constructed in such a manner as to produce the necessary firing spark for the engine at a proper time, regardless of the direction in which the engine is run, and without any adjustment needed in the parts of the magneto.
A still further object is to provide a portable, powerdriven tool with reversible work element which also includes a novel, manually operated starting mechanism for the engine for rotating its crank or engine shaft in either of opposite directions during starting.
Other features, objects and advantages of the invention are discussed hereinbelow, in conjunction with the accompanying drawings, wherein:
FIG. 1 is a side view of a portable power tool constructed according to an embodiment of this invention, with portions of the casing or housing of the tool removed to illustrate details of construction;
FIG. 2 is a section view, slightly enlarged, along the line 2-2 in FIG. 1, showing the construction of the manually actuated mechanism provided for turning the engine crankshaft in either of opposite directions;
FIG. 3 is a section view along the line 3-3 in FIG. 2, illustrating details of a double-acting, over-running clutch in the starter mechanism; and
FIG. 4 is an illustration, in somewhat schematic form, showing the construction of the magneto firing system provided the engine of the tool.
Referring now to the drawings, and more particularly to FIG. 1, 10 indicates generally a portable, power-driven impact wrench. At the forward end of the tool, i.e., the right end in FIG. 1, is a housing or casing portion 12 enclosing the operating parts of an impact wrench mechanism proper, indicated generally at 14. Toward the rear end of the tool is an engine housing portion 16 enclosing a two-cycle, single-cylinder internal combustion engine, indicated generally at 18. At the extreme rear end of the tool, opposite casing portion 12, is manually actuated starter mechanism, indicated generally at 20. The latter is provided for turning over the crankshaft or engine shaft of engine 18, when starting up the tool.
Completing a general description of the impact wrench,
I 22 and 24 indicate handle portions used by an operator in manipulating the tool. At 25 is indicateda trigger throttle control used in regulating the fuel charge delivered to engine 18.
The impact wrench mechanism indicated at 14 is conventional, and is described only briefly. In the construction shown, the mechanism includes a work element 26 for engaging a nut, bolt, or the like. Work element 26 is rotated by means of an anvil part 28. The latter part in turn is driven by an axially shiftable hammer portion 30, having jaw portions 32 received within recess 33 of part 28, so that rotation of portion 31) turns part 28.
A compression spring 34 bears against the rear of hammer portion 30, forcing jaw portions 32 into engagement with part 28. A drive spindle for the mechanism driving hammer portion 30 is indicated at 36.
Describing the operation of Wrench mechanism 14, during such periods of operation that relatively small resistance to turning is encountered by work element 26, spring 34 urges hammer portion 30 against part 28, with the result that drive is directly from the spindle through the hammer portion to the anvil part and work element. As resistance to turning movement increases (such as when a nut is turned and the nut begins to sit), cam mechanism (not shown) operates to draw hammer portion 30 out of engagement with the anvil part 28 with compression of spring 34. When this occurs, the drive spindle rotates the hammer portion free of part 28. The hammer portion spins into engagement with part 28 on continued rotation of the hammer portion, and as it engages the anvil part imparts a rotary blow to part 28 causing a high torque to be applied thereto and to the work element. This withdrawing of the hammer portion and spinning into engagement repeats until maximum resistance to turning is encountered. Particular details of the wrench mechanism are not pertinent in understanding the invention. Suffice it to say that they ordinarily comprise a driving spindle, and mechanism intermittently for transmitting the drive from the spindle to the work element of the mechanism.
Internal combustion engine 18 is typical of singlecylinder, two-cycle engines, and comprises a cylinder portion 40 (provided with fins 42. for cooling purposes), and mounted at the top of the cylinder portion, a spark plug or spark-producing device 44. Reciprocating up and down Within cylinder portion 40 is a piston 46 (see FIG. 4), and this is connected through a piston rod 48 with an engine or crankshaft 50. The crankshaft, as can be seen in FIG. 1, is axially aligned with and extends forwardly toward drive spindle 36 of the wrench mechanism.
Drivingly connecting the forward end of the crankshaft to the rear end of drive spindle 36 is a centrifugal clutch mechanism, indicated generally at 60. The specific form of clutch used is not important, as such clutch constructions per so are well known. In the embodiment illustrated, the clutch mechanism comprises a clutch drum 62 connected to the drive spindle. Inner surface portions of the clutch drum during operation of the clutch are engaged by centrifugal clutch shoes 64. The latter are mounted on driving clutch part 66, and are pulled radially inwardly against the action of centrifugal force by springs 68. Describing the operation of the clutch, when the speed of rotation of the crankshaft 50 reaches a certain level, centrifugal force operates to throw the clutch shoes outwardly against clutch drum 62, and drive is then transmitted from the crankshaft to drive spindle 36. At idling speeds for engine 18, springs 68 draw the clutch shoes radially inwardly to interrupt any drive connection.
In the organization described, drive is directly from the crankshaft to the drive spindle through the centrifugal clutch mechanism. The drive train is linear and the organization is devoid of any reversing transmission between the engine and wrench mechanism 14. Instead of reversing the rotation of the drive spindle by means of a transmission, a firing system for engine 18 is provided which enables the engine to run with equal efficiency in either of opposite directions. Elimination of such a transmission makes possible a substantial lessening of weight in the tool, particularly at the forward end, Which is the end that must be maneuvered when the tool is placed in registry with a part to be rotated.
Considering now details of the firing system, 70 indicates generally a flywheel, provided with vanes 72 for cooling purposes. The flywheel is connected to crankshaft 50 by a bolt 74. A flywheel magneto is provided for producing intermittently sparks in spark plug 44, such system producing automatically and without any manual adjustment a spark at proper time for firing with engine 18 running in either of opposite directions.
Referring to FIGS. 1 and 4, 78 indicates a stator portion of the magneto, such stator comprising a core 80 having three legs, indicated at 80a, 80b and 800. The bottom ends of the legs are positioned closely adjacent to the peripheral surface 82 of flywheel 70. As will be described, pole pieces are mounted on the flywheel, and these, on rotation of the flywheel, are rotated past the ends of legs 80a, 80b and 800. Thus in the construction, the flywheel and pole pieces constitute the rotor portion of the magneto, and this is driven by the engine through the connection of the flywheel with crankshaft 50.
Referring to FIG. 4, a coil means indicated at 84, for the magneto, comprising a primary winding 86 and a secondary winding 88 (containing a relatively large number of turns as compared to the primary winding) is Wrapped around the center leg 8011 or core 30. One end 88a of the secondary winding is grounded, and the other end 88b is connected to one of the contacts of spark plug 44. The other contact of the spark plug is grounded at 90. Considering primary winding 86, one end 86a is grounded, and the other end 86b is connected to one of the contacts of a switch in an interrupter, or a circuit breaker, indicated at 96. Completing the description of the circuit means for the magneto, the other contact of the switch in interrupter 96 is grounded by conductor 100. Connected across this switch with one end grounded is a condenser 98. A kill switch 102, operable when closed to short circuit the switch of interrupter 96, is also included.
A magnet means for the magneto is mounted on the flywheel or rotor, and comprises two sets of pole pieces, indicated at 104 and 106, respectively. Each set includes two magnets (indicated at 104a, 104b, 106a and 1061;), one of each set having its north pole and the other of each set having its south pole facing radially outwardly on the flywheel. Thus magnet 106a and magnet 104a may have their north poles facing outwardly, and the magnets 106b and 104b may have their south poles facing outwardly.
As in a conventional two-cycle engine, a fuel charge is compressed as the piston nears the top of the cylinder. Slightly before reaching the top of the cylinder, a spark should be produced in plug 44, so that ignition, propagation, and combustion of the charge may then take place in that order. The timing of the spark is usually adjusted so that combustion occurs with the piston traveling downwardly in the cylinder.
To this end, the set of pole pieces 106 are used to produce a spark with the flywheel and shaft 50 rotated in a clockwise direction (as shown by the arrow) in FIG. 4. They are spaced on the flywheel so that, as shown in FIG. 4, at the time the pole pieces reach their maximum position (the position producing most rapid change of flux in the center leg b and the coil windings), piston 46 is nearing the top of the cylinder and the time is proper for ignition of the charge with the engine running in this clockwise direction. The set of pole pieces 104 is similarly positioned with respect to shaft 50, so that on counterclockwise rotation, this set reaches its maximum position at proper time for firing with the engine running in a counterclockwise direction.
Secured to the crankshaft and rotated therewith is a cam 110. This has a node 112 operable to actuate the switch of interrupter 96 (through spring-returned actuating rod 114) at the time the set of pole pieces 106 reaches its maximum position when the crankshaft is rotated in a clockwise direction, and at the time the set of pole pieces 104 reaches its maximum position when the crankshaft is rotated in the opposite direction.
The type of magneto described is a high-tension, shunt magneto. Explaining its principle of operation, when the flywheel rotates in a clockwise direction, as pole pieces 106 pass the first pair of legs of core 80, lines of flux are set up extending in one direction through the center leg 80b. On continued movement of the pole pieces, they start to pass from legs 80a, 80b to legs 80b, 80c, and their maximum position is reached (about the position illustrated in FIG. 4). There is a sudden collapse of the flux produced immediately prior to this, and lines of flux extending in the opposite direction through leg 80b are set up. At this maximum position the switch of the interrupter is opened, and the magneto coils are activated. A high voltage is produced in the primary winding and this is stepped up in the secondary, and transmitted to plug 44 where a spark results. When the second set of pole pieces 104 move past the core, any charge in the cylinder has already been ignited. The same type of operation results with rotation in the opposite direction, but in this instance pole pieces 104 produce the ignition spark. It should be noted that the sparks produced automatically are at proper time for firing, and that no adjustment in the firing system is necessary.
Referring now to FIGS. 1, 2 and 3, manually actuated starter mechanism 30' for turning the crankshaft comprises a starter shaft 120 rotatably mounted in housing structure 122 of the tool. Shaft 120 has a bevel gear 124 joined to one end and its other end adjacent the rear end of the crankshaft. A reversing transmission, indicated at 126, is provided for rotating starter shaft 120 in either of opposite directions.
Reversing transmission 126 comprises a pair of bevel gears 128, 130 secured to a spindle 132. Spindle 1-32 is shiftable axially to and fro in housing structure 122, to place either bevel gear 128 in meshing engagement with gear 124, or bevel gear 130 in meshing engagement with gear 124. The ends 132a, 13% of spindle 132 protrude beyond the housing, so that they may be pushed under digital pressure to place either one or the other of the gears in engagement.
A recoil starter mechanism 140, of conventional construction is provided for rotating spindle 132. The recoil starter mechanism includes the usual pull cord 142 secured to a handle 144. In operation, handle and cord 142 are pulled outwardly of the housing, causing the cord to unroll from pulley structure 145, with resulting rotation of the pulley structure turning shaft 132. A spring mechanism (not shown) rewinds the cord, and the pulley structure, when rewinding the cord, turns freely of spindle 132.
Interposed between starter shaft 121} and the flywheel of the engine is a double-acting, overrunning clutch mechanism, indicated at 150. This comprises a driving part 152 secured to the end of the starter shaft and mounted within [a recessed driven portion 154 integral with the flywheel. Driven portion 154 is provided at regular angular spacing around wall 155 that surrounds part 152 with a series of cavities, indicated at 156 through 159, extending radially outwardly from the outline of wall 155. These are of large enough size substantially completely to receive a series of balls 160'.
Driving part 152 is formed with a series of indents 162, 163, 164 and 165, each having a base 166 big enough to receive completely a ball without the same contacting wall 155. Away from the base is a portion '167 that slopes outwardly, to wedge any ball bearing against the sloping portion against wall 155 of the driven part.
The clutch construction described enables relatively slow movement of the starter shaft in either of opposite directions to be transmitted to the engine shaft for purposes of starting the engine. Once the engine catches and the engine shaft picks up speed, the engine shaft can rotate freely of starter shaft 129. Explaining the operation, and assuming with reference to FIG. 3 that the motor is to be turned in a clockwise direction, driving part 152 is rotated in a clockwise direction by shaft 120. Indents 162, 164 thence operate to confine a ball against wall 155, with wedging engagement between the parts occurring and turning of the engine shaft with the starter shaft. On movement of the engine shaft at a faster speed, relative movement of the starter shaft with respect to the engine shaft in a counterclockwise direction in FIG. 3 results. The balls 160 of indents 162, 164 fall into cavities 156, "158, and the drive connection is broken. For starting in the opposite direction, indents 163, 165 are employed.
From the above description, it will be seen that a power-driven tool has been provided, which can be driven in either of opposite directions, and this can be done without adjusting a transmission or adjusting any parts of the engine. To start the engine, it is only necessary to turn the engine over, the direction of rotation determining the rotation of the driving element. The manually actuated starter mechanism makes use of a recoil starter and a reversing transmission between the recoil starter and the starter shaft, whereby reverse rotation in the engine shaft may be produced from a unidirectionally operating recoil starter. The overrunning clutch described permits the engine shaft to turn free of the starter shaft once it reaches running speed, and this is possible in either of opposite directions of rotation.
Assuming that the engine is running in one direction, and that it is desired to change the direction of rotation of the work element, it has been found that the engine need not be completely stopped to produce reverse running. Instead, kill switch 102 may be actuated, just at the time the pole pieces that ordinarily would produce the spark for firing reach their maximum position. This short circuits the primary winding, and no spark is pro duced. If the switch 102 is then released (opened), these same pole pieces on the next revolution of the flywheel come into the vicinity of the core 80, but the momentum of the parts on this revolution is not sufficient to cause the piston to reach the end of its stroke. The spark produced starts reverse operation, and on continued reverse running, firing of the motor is done by the other set of pole pieces.
It is claimed and desired to secure as Letters Patent:
1. An internal combustion engine, and a firing system for the engine operable automatically to produce an ignition spark for the engine at proper time for firing with the engine running in either of opposite directions, said firing system comprising a spark-producing device, a magneto including a rotor portion connected to the engine to be driven thereby, a stator portion, coil means mounted on one of said portions and connected to said spark-producing device, magnet means mounted on the other of said portions, and an interrupter for activating the coil means including means actuating the interrupter connected to the engine, said means actuating the interrupter being constructed to activate said coil means at one position of the rotor portion when the engine is run in one direction and at another position of the rotor portin when the engine is run in the opposite direction, said one position of the rotor portion being proper time for firing of the engine with the engine running in said one direction and the other position of the rotor portion being proper time for firing the engine with the engine running in the opposite direction, said coil and magnet means being constructed to produce voltage peaks in said magnets at each of these positions of the rotor portion.
2. An internal combustion engine, and a firing system for the engine operable automatically to produce an ignition spark for the engine at proper time for firing with the engine running in either of opposite directions, said firing system comprising a spark-producing device. a magneto including a rotor connected to the engine to be driven thereby, a stator, coil means mounted on the stator and connected to said spark-producing device, magnet means mounted on the rotor, and an interrupter for activating the coil means including means actuating the interrupter connected to the engine, said magnet means comprising a double set of pole pieces spaced on the periphery of the rotor so as to produce at least two rapid changes of flux in the coil means on one revolunon of the rotor, said means actuating the interrupter being constructed to activate said coil means at one position of the rotor when the engine is run in one direction and at another position of the rotor when the engine is run in the opposite direction, one set of pole pieces in said one position of the rotor being in position to produce one of said rapid changes of flux, the other set of pole pieces in said other position of the rotor being in position to produce the other of said rapid changes of flux.
3. In a portable power tool, the combination of a reversible internal combustion engine for driving the tool, said engine having an engine shaft, and firing means operable to produce with the engine running in either of opposite directions an ignition spark at proper time for firing the combustible charge of the engine, and
mechanism for turning manually the engine shaft in either of opposite directions thereby to start the engine, said mechanism including a double-acting, clutch mechanism having rotatable driving and driven members and means for establishing a drive connection between the driving and driven members in either of opposite directions of rotation for the driving member with said means being overrunning in either of said opposite directions, means connecting the driven member to the engine shaft, and mechanism for turning manually the driving member in either of opposite directions.
4. 'In a portable power tool having a reversible Work element adapted to be rotated in either of opposite directions, the combination of an internal combustion engine having an engine shaft and means connecting the engine shaft with said work element, a magneto firing system for the engine constructed to produce a firing spark for the engine at proper time for firing with the engine running in either of opposite directions, and manually actuated mechanism for turning said engine shaft in either of opposite directions thereby to start the engine, said mechanism having a starter shaft, a double-acting, clutch mechanism having rotatable driving and driven members and means for establishing a drive connection between the driving and driven members in either of opposite directions of rotation for the driving member with said means being overrunning in either of said opposite directions, means connecting the starter shaft and the driving member, means connecting the engine shaft and the driven member, and manually operated means for rotating the starter shaft in either of opposite directions.
5. The tool of claim 4 wherein the manually operated means for rotating the starter shaft comprises a recoil starter having a spindle rotatable by the recoil starter in One direction only, and a reversing transmission operatively connecting the spindle and starter shaft adjustable between positions where the starter shaft is driven in either of opposite directions on rotation of said spindle in one direction.
6. In an internal combustion engine having a spark producing device, the improvement comprising means for producing an ignition spark in said device at proper time for firing the engine with the engine running in either of opposite directions, said means comprising a magneto circuit connected to said spark-producing device, a magneto rotor portion connected to said engine to be driven there by and a magneto stator portion, said magneto circuit comprising coil means mounted on one of said portions and magnet means mounted on the other of said portions including a double set of pole pieces spaced from each other so as to produce at least two rapid changes of flux in said coil means on one revolution of said rotor portion, an interrupter for activating said coil means and means for actuating said interrupter connected to said engine, said means for actuating said interrupter being constructed to activate said coil means at one position of said rotor portion when the engine is run in one direction and at another position of said rotor portion when the engine is run in the opposite direction, one set of pole pieces in, said one position of the rotor portion being in position to produce one of said rapid changes of flux, said other set of pole pieces in said other position of said rotor portion being in position to produce the other of said rapid changes of flux.
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