Abstract: There is provided a method of applying plating to an aluminum alloy material, which comprises a step of cathodic acid electrolysis as a pretreatment for the plating for removing insoluble matters from the aluminum alloy generated in a previous alkaline-etching step.

Abstract: A power transmission device is disclosed which is capable of easily, swiftly and appropriately altering the distance between the axes of a pair of transmission wheels such as pulleys, enabling an endless belt to be kept under constant and appropriate tension without necessitating a tension roller. This power transmission device comprises an endless belt wound around a pair of transmission wheels; and a cam-type adjusting mechanism which is interposed between a driving side supporting member and a driven side supporting member and configured to adjust a distance between the axes of the wheels. This cam-type adjusting mechanism comprises a supporting shaft secured to either the driving side supporting member or the driven side supporting member and disposed parallel to the rotational axes of the wheels; and a cam rotatably secured via a manipulating boss member to the supporting shaft.

Abstract: It is the object of the present invention to provide a centrifugal blower fan capable of reducing a noise in an operating rotational speed range without degradation in blàwer performance. A centrifugal blower fan comprises a base plate, and a plurality of fan blades arranged on the base plate in a radial pattern to define a plurality of air passages between the pairs of adjacent fan blades, respectively. A portion of the base plate serving as a bottom wall of each of the air passages is formed with a plurality of through-holes.

Abstract: A blower fan includes: an impeller having a predetermined number of blades; a fan casing having an air-intake port disposed to face a central portion of base of the impeller and eccentrically housing the blower fan and defining a spiral scroll passageway between an inner wall thereof and an external circumference of the impeller, the spiral scroll passageway having an inlet portion constituting a narrow nose portion and an outlet portion constituting a wide discharge port; and a driving source for rotating the impeller. In order to minimize the noise to be released from the nose portion, the blower fan further includes a sound-reflecting means which is disposed to cover a portion of the air inlet port at a location spaced away from the nose portion by a distance corresponding to ½ of wavelength of noise in an emanating direction of noise.

Abstract: A liquid quantity visual confirmation device comprises a first reservoir-forming member, and a second reservoir-forming member forming a liquid reservoir in combination with the first reservoir-forming member. The second reservoir-forming member is at least partially transparent to allow visual confirmation of the internal liquid level from an outside thereof. The second reservoir-forming member has a liquid-feeding port for feeding the liquid into the liquid reservoir. The quantity of liquid in the liquid reservoir can be confirmed by looking at the internal liquid level in the second reservoir-forming member from the outside. It is also possible to reliably feed the liquid into the liquid reservoir from the liquid-feeding port while confirming any rising of the liquid level through the transparent portion.

Abstract: A power blower includes a frame, and a blower mounted on the frame. An air intake port of the blower faces the frame. There is provided an air intake space between the blower and the frame. A debris-catching cover is constructed between the frame side and the blower side in a state in which it is mounted on both the frame and blower sides. The debris-catching cover inhibits debris from being sucked from the air intake space into the air intake port.

Abstract: A two-stroke internal combustion engine (1) is provided with one pair or plural pairs of C-shaped scavenging passageways (31, 32) of a reverse flow system where scavenging inlet ports (31a) as well as scavenging outlet ports (31b, 32b) are both opened to a cylinder bore (10a), wherein a scavenging introducing passageway (40) for introducing an air-fuel mixture (K) from a crank chamber (18) into the scavenging inlet ports (31a) is provided between the cylinder bore and the piston adapted to reciprocatively move up and down in the cylinder bore (10a), and an effective opening area of the scavenging inlet ports (31a) is gradually decreased due to the piston (20) in the course of descending stroke of the piston (20).

Abstract: A portable power working machine is disclosed, which is capable of effectively minimizing the clogging of the air cleaner, thereby dispensing with frequent maintenance. This portable power working machine comprises an air cleaner (30) having a base body case (32) provided with a clean air discharge port (33) for introducing the air cleaned into an intake port (25) of a carburetor (14), a filter (35) which is mounted on a filter mounting opening (32a) of base body case (32) so as to seal it, and a cleaner cover (37) which is attached onto the filter (35) so as to cover the filter (35) and to guide outside air toward the filter (35), while giving a predetermined directionality to the outside air.

Abstract: A catalyst-attached muffler includes an expansion chamber (25) defined by a cup-shaped fore-side outer wall panel (21) and a cup-shaped rear-side outer wall panel (22), both panels being removably attached to each other; a partition panel (23) interposed between the fore-side outer wall panel and the rear-side outer wall panel to partition the expansion chamber into a first expansion chamber (25A) and a second expansion chamber (25B).

Abstract: There is provided a portable air blowing working machine capable of obviating frequent operation for the maintenance of air cleaner and hence capable of improving working efficiency. This working machine includes an internal combustion engine having the air cleaner disposed in the air-intake system thereof, and an air blower to be rotationally driven by the engine; which is characterized in that the air cleaner is provided with a suction port for in drawing in external air, with a filter member for cleaning air drawn from the suction port to thereby permit the cleaned air to be introduced into the engine, and with a discharge port for enabling part of the air drawn from the suction port to be discharged out of the air cleaner without permitting part of the air to pass through the filter member; and that an air flow directed to flow from the suction port to the discharge port is permitted to generate inside the air cleaner by making use of the suction force of the air blower.

Abstract: There is provided a pipe joint structure wherein a proximal insert portion (20a) of an attachment pipe (20) is inserted into and secured to a base pipe (12).

Abstract: A catalyst-installed muffler includes an expansion chamber (25), and a gas-permeable exhaust gas-purifying catalyst (30), wherein exhaust gas blown out of the exhaust port (10) of an internal combustion engine is introduced into the expansion chamber (25) through the catalyst (30). The catalyst (30) may be cylindrical in configuration. An outer circumferential cross-sectional configuration of the catalyst (30) is made identical with an inner circumferential cross-sectional configuration of the outer end portion (10a) of the exhaust port (10), so that one end portion (exhaust gas introducing side 30a) of the catalyst (30) is enabled to fit in an outer end portion (10a) of the exhaust port (10). According to this muffler, it is made possible to utilize the purifying capacity of the catalyst to a maximum extent.

Abstract: A saw chain tensioning mechanism for adjusting the tension in a saw chain extending around a chain guide plate includes a threaded rod member disposed adjacent to a rear end of the chain guide plate and along the longitudinal direction of the chain guide plate, a movable member engaged with the chain guide plate and adapted to be moved along the threaded rod member by a rotation of the threaded rod member, and a driving gear integral with the threaded rod member. The tensioning mechanism includes a driving gear for rotatively driving the driving gear and an operating member for manually rotating the driving gear. Manipulating the operating member changes the longitudinal position of the chain guide plate and correspondingly causes a change in a tension of the saw chain.

Abstract: An oil pump mechanism is incorporated in a chain saw having a centrifugal clutch and a saw chain adapted to be driven through the centrifugal clutch and activated in synchronization with the centrifugal clutch to supply a lubricating oil to the saw chain. The mechanism includes a crankshaft, a clutch shoe being mounted on the centrifugal clutch and being connected in driven relation to the crankshaft, a clutch drum disposed coaxially around the crankshaft, a worm fitted on the crankshaft by insertion in a freely rotatable manner and connected in driven relation to the clutch drum to be integrally rotated with the clutch drum, a driven gear engaged with the worm, and a movable pumping element for pumping the lubricating oil. The worm has an inner portion located opposed to the crankshaft and an outer portion including a tooth region. The inner portion is made of self-lubricating resin and the outer portion is made of wear-resistant metal.

Abstract: The present invention provides an air-cooled four-stroke internal combustion engine capable of achieving a high degree of cooling. The present invention is directed to an air-cooled four-stroke internal combustion engine including a crankshaft and a fan rotor rotatably driven by the crankshaft to generate cooling air for cooling the engine. The engine comprises an oil pan disposed below the crankshaft. A space formed below the oil pan extends in the axial direction of the crankshaft along the lower surface of the oil pan and allows a cooling air to pass therethrough. An upstream portion of the lower surface is inclined upward, toward the upstream, in a vertical section taken along the axis of the crankshaft to receive the cooling air therein.

Abstract: The present invention relates to a brake band for use with a centrifugal clutch. The brake band is formed in a curved strip shape to be disposed along the outer peripheral surface of a clutch drum of the centrifugal clutch, and is adapted to be tightened around or released from the outer peripheral surface in response to the movement of at least one end of the brake band. The brake band comprises a plurality of linings provided on the inner surface thereof to be opposed the outer peripheral surface of the clutch drum. The linings are located spaced apart from each other along the longitudinal direction of the brake band.

Abstract: There is provided a method of cast molding a cylinder for an internal combustion engine by making use of an insert core, which makes it possible to rationally form the chamfered portions at the rim portion, on the cylinder bore side, of the scavenging ports, the suction port and the exhaust port with high precision and high freedom in dimension and configuration without fluctuation in size and configuration of the chamfered portion.

Abstract: A recoil starter for a backpack type power working machine, which is capable of easily performing the starting operation of an internal combustion engine with the working machine being carried on the operator's back. In this recoil starter, the recoil rope and the recoil handle are disposed so as to be pulled down obliquely forward at an angle of 100° to 150° to the horizontal plane. The recoil handle is formed into a T-shaped configuration in side view, which comprises the grip portion and a laterally extended stopper portion which is formed on a distal end of the grip portion.