Abstract: Cyclooctadiene derivative of the following formula (1): ##STR1## wherein A.sup.1, A.sup.2, A.sup.3 and A.sup.4 each independently represent COOR.sup.5 (where R.sup.5 represents a hydrogen atom, a C.sub.1 -C.sub.10 alkyl group, a phenyl group, a C.sub.7 -C.sub.12 aralkyl group or CONR.sup.6 R.sup.7 (where R.sup.6 and R.sup.7 each independently represent a hydrogen atom, a C.sub.1 -C.sub.10 alkyl group or a phenyl group), or A.sup.1 and A.sup.2, and/or A.sup.3 and A.sup.4 may be combined together to represent group(s) of: ##STR2## in which X represents an oxygen atom or NR.sup.8 {where R.sup.8 represents a hydrogen atom, a C.sub.1 -C.sub.10 alkyl group or a phenyl group),R.sup.0, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a halogen atom, a hydroxyl group and an C.sub.1 -C.sub.10 alkyl group,the symbol ------ represents a single or double bond, and when it is a double bond, then R.sup.1 and R.sup.

Abstract: A safety mechanism for a nailing machine in which a start valve for a hammering mechanism is driven by cooperative action of operating a trigger lever and moving a contact arm to an uppermost point where it is pressed against a material to be nailed. The hammering mechanism for hammering a nail is supplied to a nose section arranged at a front end portion of a housing and is actuated by the start valve.

Abstract: The operation mode of a nailing machine can be automatically and reliably switched, for its selection, from the successive nailing mode and the one-shot nailing mode and vice versa by changing the order of operating a trigger lever and a contact arm. In the selected mode, the nailing work can be performed. By releasing both the trigger lever and the contact arm, the machine is returned to its initial mode. When the contact arm is moved to the top dead center after the trigger lever is operated, a portion of a slide die comes in contact with the underside of the trigger lever. When the trigger lever is operated after the contact arm is moved to the top dead center, the portion of the slide die comes in contact with the upper side of the trigger lever, thereby preventing a further movement of the contact arm to the bottom dead center.

Abstract: A nailing machine according to the present invention comprises a nail push member for separating a nail from a nail band supplied to the nail injection hole of the nose member by the nail supply mechanism before the nail is driven by the percussion driver and for pushing the nail to the front of the nail injection hole; and a nail holding means for holding the body part of the nail pushed to the fore side of the nose member by the nail push member in a state that the pointed end of the nail is protruded. Thereby, the nailing machine can easily be positioned in a manner that the pointed end portion of a nail is protruded from the foremost end of the nose member by a predetermined length before the nailing machine drives a nail supplied to the nailing position, and the protruded end of the nail can be inserted into a through-hole of the work.

Abstract: A percussion tool of the repeatedly operating type includes a housing, a striking cylinder received in the housing for movement therealong, and a driving piston received in the striking cylinder for movement therealong. The striking cylinder cooperates with the housing to provide a switch valve means which is responsive to the movement of the striking cylinder along the housing for selectively interrupting fluid communication between the interior of the striking cylinder and a discharge port and communicating the interior of said striking cylinder with a compressed air source when the striking cylinder is at its lower position to thereby move the striking piston to cause an associated striking driver to strike a driven element and for selectively interrupting the communication between the interior of the striking cylinder and the compressed air source and communicating the interior of the striking cylinder with the discharge port as the striking cylinder is moved from its lower to upper position.

Abstract: Hydrocracking catalysts are disclosed which comprise specified amounts of selected inorganic oxides and specified amounts of selected metal components carried thereon. The carrier is essentially derived from solid-phase modification with specified amounts of a selected class of fluorine compounds. Mineral oils are selectively processable with high catalytic activity and at maximum yield.