Abstract: A rotary channel-selector valve is provided, which includes: a valve-seat plate covering one end of a cylindrical valve housing and provided with low and high pressure ports and two switching ports all connecting the inside and the outside of the valve; and a main valve element accommodated in the valve housing and provided with low and high pressure connecting grooves on one end surface thereof, wherein one (or the other) of the switching ports communicates with the low pressure port through the low pressure connecting groove and simultaneously the other (or one) thereof communicates with the high pressure port through the high pressure connecting groove at a first (or second) channel-switching position of the main valve element.

Abstract: A rotary channel-selector valve is provided, which includes: a valve-seat plate covering one end of a cylindrical valve housing and provided with low and high pressure ports and two switching ports all connecting the inside and the outside of the valve; and a main valve element accommodated in the valve housing and provided with low and high pressure connecting grooves on one end surface thereof, wherein one (or the other) of the switching ports communicates with the low pressure port through the low pressure connecting groove and simultaneously the other (or one) thereof communicates with the high pressure port through the high pressure connecting groove at a first (or second) channel-switching position of the main valve element.

Abstract: A rotary channel-selector valve is provided, which includes: a valve-seat plate covering one end of a cylindrical valve housing and provided with low and high pressure ports and two switching ports all connecting the inside and the outside of the valve; and a main valve element accommodated in the valve housing and provided with low and high pressure connecting grooves on one end surface thereof, wherein one (or the other) of the switching ports communicates with the low pressure port through the low pressure connecting groove and simultaneously the other (or one) thereof communicates with the high pressure port through the high pressure connecting groove at a first (or second) channel-switching position of the main valve element.

Abstract: A rotary channel-selector valve is provided, which includes: a valve-seat plate covering one end of a cylindrical valve housing and provided with low and high pressure ports and two switching ports all connecting the inside and the outside of the valve; and a main valve element accommodated in the valve housing and provided with low and high pressure connecting grooves on one end surface thereof, wherein one (or the other) of the switching ports communicates with the low pressure port through the low pressure connecting groove and simultaneously the other (or one) thereof communicates with the high pressure port through the high pressure connecting groove at a first (or second) channel-switching position of the main valve element.

Abstract: In a rotary flow-path exchanging valve, the magnetic force generated in a pair of main magnetic pole pieces (66) by energization of an electromagnetic solenoid is acted on a multi-pole magnet (71) of a main valve element accommodated within a valve housing (1) so that the main valve element (3) is rotated to exchange a flow-path. The multi-pole magnet (71) is made of a plastic magnet of plastic material mixed with magnetic powder. The main valve element (3) and multi-pole magnet (71) are integrally formed by multiple molding. A pair of main magnetic pole pieces (66) magnetically connected to one polarity of the electromagnetic solenoid (11) are arranged. A pair of auxiliary magnetic pole pieces (70) connected to the other polarity of the electromagnetic solenoid (11) are arranged at positions out of phase from the magnetic pole pieces by 90.degree..

Abstract: In a rotary flow-path exchanging valve, the magnetic force generated in a pair of main magnetic pole pieces (66) by energization of an electromagnetic solenoid is acted on a multi-pole magnet (71) of a main valve element accommodated within a valve housing (1) so that the main valve element (3) is rotated to exchange a flow-path. The multi-pole magnet (71) is made of a plastic magnet of plastic material mixed with magnetic powder. The main valve element (3) and multi-pole magnet (71) are integrally formed by multiple molding. A pair of main magnetic pole pieces (66) magnetically connected to one polarity of the electromagnetic solenoid (11) are arranged. A pair of auxiliary magnetic pole pieces (70) connected to the other polarity of the electromagnetic solenoid (11) are arranged at positions out of phase from the magnetic pole pieces by 90.degree..

Abstract: In a rotary flow-path exchanging valve, the magnetic force generated in a pair of main magnetic pole pieces 66 by energization of an electromagnetic solenoid is acted on a multi-pole magnet 71 of a main valve element accommodated within a valve housing 1 so that the main valve element 3 is rotated to exchange a flow-path. The multi-pole magnet 71 is made of a plastic magnet of plastic material mixed with magnetic powder. The main valve element 3 and multi-pole magnet 71 are integrally formed by multiple molding. A pair of main magnetic pole pieces 66 magnetically connected to one polarity of the electromagnetic solenoid 11 are arranged. A pair of auxiliary magnetic pole pieces 70 connected to the other polarity of the electromagnetic solenoid 11 are arranged at positions out of phase from the magnetic pole pieces by 90.degree..

Abstract: In a rotary flow-path exchanging valve, a high pressure side communicating groove 37 is provided to communicate a first exchanging port 23 and a second exchanging port 27 of a valve seat plate 5 with a high pressure side communicating port selectively. A part of a joint pipe 17 to be connected to the high pressure side port 19 is protruded into the high pressure side communicating groove 27. The protruding part constitutes a stopper pipe 20 for limiting the rotatable range of a valve element 1. In installing the stopper pipe 20, it is connected and secured to the high pressure side port 19 of the valve seat plate 5, and thereafter is hardened by plastic deformation processing. Thus, when the stopper pipe is heated by soldering for its securing to the valve seat 5, the necessary strength thereof can be maintained.

Abstract: A hood for enclosing a radiator and an engine has a hood grille formed in a front surface of the hood. The hood grille includes a front wall, and right and left side walls extending from opposite sides of the front wall. The front wall defines intake openings for drawing in air for the radiator. The right and left side walls include bent portions bent substantially at right angles to the front wall. Opposite end regions thereof are secured to the right and left side walls by fixing devices. Hood grille netting extends over an entire area of the intake openings and covers at least parts of the right and left side walls. The opposite end regions of the hood grille netting are bent to correspond to the bent portions. The hood grille netting is secured to the hood grille by bolts and spacers to define spaces between the hood grille netting and the right and left side walls. These spaces communicate with the intake openings.

Abstract: A speed control system for a working vehicle having a stepless transmission with a speed control shaft disposed on one side thereof and shiftable between a driving region and a neutral position. This speed control system includes a shift lever disposed on one side of a driver's section for setting a traveling speed of the tractor, while the speed control shaft of the stepless transmission is disposed on the other side of the driver's section. The shift lever is operatively connected to the speed control shaft through a link mechanism. The link mechanism includes a neutralizing mechanism in an intermediate position thereof adjacent the shift lever for returning the speed control shaft to the neutral position.

Abstract: A speed control system for a vehicle having a braking device and a stepless transmission. A change speed member for controlling the stepless transmission is shiftable between a forward drive zone and a backward drive zone across a neutral position. The change speed member is urged to the neutral position, and operatively connected to a change speed pedal and a shift lever. The shift lever is lockable to a selected shift position. Switching may be made between a connection enable state for enabling connection between a first interlocking member connected to the change speed member and a second interlocking member connected to the shift lever, and a connection prohibit state for prohibiting the connection between the first interlocking member and second interlocking member.The connection between the first interlocking member and second interlocking member is canceled with operation of the braking device.

Abstract: A four wheel drive vehicle with dirigible front wheels, comprising a main propelling drive transmission, and a front wheel drive transmission connected to the main transmission. The front wheel drive transmission is switchable between a first four wheel drive mode in which the front wheels and the rear wheels are driven at a substantially equal peripheral speed and a second four wheel drive mode in which the front wheels are driven at a higher peripheral speed than the rear wheels. The front wheel drive transmission includes a piston operable by a hydraulic control system including a control valve mechanically interlocked to a steering section of the vehicle for switching the front wheel drive transmission from the first drive mode to the second drive mode. The piston, which normally is biased toward a position for the first drive mode, is movable against the biasing force to a position for the second drive mode when the front wheels are steered to an angle exceeding a predetermined angle.

Abstract: An agricultural tractor with a driver's cabin, in which the cabin is supported by a safety frame which is in turn supported by an axle case.

Abstract: A wheel drive structure for an agricultural tractor comprising a drive case housing a differential mechanism and reduction mechanisms to transmit power from said differential mechanism to wheels. The drive case comprises first and second case portions and said first case portion is made of a structural steel pipe.

Abstract: A pattern utilized to prepare a diffraction grating, or an element of a semiconductor device, for example a silicon island, or a device isolation pattern or a semiconductor element, such as a MOS FET, is formed by the steps of forming an oxidizable region of a predetermined pattern on a substrate and oxidizing the oxidizable region for forming an oxide region pattern in at least a portion of the sidewalls of the oxidizable region. The resulting pattern, which is extremely fine and formed at a low cost, has a sufficiently large height with respect to its width. Furthermore the pattern can be formed at a relatively low temperature.

Abstract: An agricultural tractor in which two sets of pedals are mounted on the tractor body forwardly and rearwardly with the rearward pedals at a higher position than the forward pedals. A seat can be selectively fixed at a rearward position opposed to the forward pedals or a forward position opposed to the rearward pedals, the forward position of the seat being higher than the rearward position. A steering wheel can be fixed to either a forward or rearward position corresponding to the position of the seat.