Metering device for metering a readily combustible substance, in particular acrolein acetal, from a source or a container for the substance into a vacuum line (38) by a pump whose pump power is controllable, characterized in that the pump is driven a compressed air motor (28) operated displacement pump (26), and that between the positive displacement pump (26) and the vacuum line (38) a pressure holding and regulating valve is arranged whose dimensionless delivery height H/Ho[mWS/1 mWS] with the dimensionless delivery rate Q/Qo[m.sup.3/h/1 m.sup.3/h] according to the Formula:

{H/Ho}={C1*(Q/Qo)}.sup.0.333, where.

H=Hydraulic pressure at the inlet of the pressure holding and regulating valve
Ho=1 mWS
C1=Constant for the pressure holding and regulating valve
Q=Hydraulic flow rate
Qo=1 m.sup.3/h.

A scroll compressor is provided. The scroll compressor has a housing, a partition plate, a rack, a movable scroll plate, a stationary scroll plate and a pressure relief low-speed rotation structure. The partition plate is in the interior of the housing and divides the interior of the housing into a suction space and a discharge space, and has a first through to communicate the suction space with the discharge space. The rack is in the suction space and spaced apart from the partition plate. The movable scroll plate is movably provided on the rack. The stationary scroll plate is provided on the rack and cooperates with the movable scroll plate, and has a second through hole communicating with the discharge space. The pressure relief low-speed rotation structure is provided on the stationary scroll plate and configured to communicate the second through hole with the discharge space.

A valve seat has an inner passage and outer passages. A suction valve member has first passages and a first projection portion that guides, to the first passages, the fuel that flows from a pressure chamber at the time of valve opening. Therefore, an action force by the dynamic pressure applied to the suction valve member in the valve closing direction is reduced. An action force by the pressure of fuel that flows into pressure equalization grooves counterbalances the action force by the dynamic pressure of the suction valve member. Therefore, self-closing by the dynamic pressure can be inhibited, and the maximum output of an electromagnetic driving unit can be reduced. Fuel flows through a passage radially outside the suction valve member and the first passages. A fluid passage area is securable even when a lift amount of the suction valve member is small.

An improved air compressor includes a cylinder with a piston body and an air storage container. The air storage container can be detachably mounted to the cylinder to define a primary air chamber, and an auxiliary air chamber which can reduce the motion resistance of the piston body, so that the piston body can conduct reciprocating motion in the cylinder more smoothly. Furthermore, the cylinder has an open bottom that is divided into two halves according to a central vertical line (Y) of the cylinder, wherein one half of the open bottom is horizontal while the other half of the open bottom is slanted. When the piston body reaches the bottom dead center, the head of the piston body will be entirely within the cylinder and thus keep air-tight with the cylinder. Therefore, the performance of compressing air and the operational safety can be increased.

A valve seat has an inner passage and outer passages. A suction valve member has first passages and a first projection portion that guides, to the first passages, the fuel that flows from a pressure chamber at the time of valve opening. Therefore, an action force by the dynamic pressure applied to the suction valve member in the valve closing direction is reduced. An action force by the pressure of fuel that flows into pressure equalization grooves counterbalances the action force by the dynamic pressure of the suction valve member. Therefore, self-closing by the dynamic pressure can be inhibited, and the maximum output of an electromagnetic driving unit can be reduced. Fuel flows through a passage radially outside the suction valve member and the first passages. A fluid passage area is securable even when a lift amount of the suction valve member is small.

A valve seat has an inner passage and outer passages. A suction valve member has first passages and a first projection portion that guides, to the first passages, the fuel that flows from a pressure chamber at the time of valve opening. Therefore, an action force by the dynamic pressure applied to the suction valve member in the valve closing direction is reduced. An action force by the pressure of fuel that flows into pressure equalization grooves counterbalances the action force by the dynamic pressure of the suction valve member. Therefore, self-closing by the dynamic pressure can be inhibited, and the maximum output of an electromagnetic driving unit can be reduced. Fuel flow through a passage radially outside the suction valve member and the firs passages. A fluid passage area is securable even when a lift amount of the suction valve member is small.

A compressor may include a housing, a piston, and a cylinder head assembly. The housing defines a cylinder and a first valve seat defining a recess. The piston is movable within the cylinder to define a compression chamber. The cylinder head assembly is mounted on the housing and includes a valve plate, a suction valve, a discharge valve and a head cover. The valve plate may be mounted to the mounting surface and may include a suction plenum, a suction passage providing fluid communication between the suction plenum and the cylinder, and a discharge passage. The suction valve can seat on the first valve seat to allow fluid flow through the suction passage. The head cover may include a discharge chamber and an integrally formed guide post extending into the discharge chamber. The guide post may include a pocket that receives a discharge valve stem for reciprocation therein.

A valve seat has an inner passage and outer passages. A suction valve member has first passages and a first projection portion that guides, to the first passages, the fuel that flows from a pressure chamber at the time of valve opening. Therefore, an action force by the dynamic pressure applied to the suction valve member in the valve closing direction is reduced. An action force by the pressure of fuel that flows into pressure equalization grooves counterbalances the action force by the dynamic pressure of the suction valve member. Therefore, self-closing by the dynamic pressure can be inhibited, and the maximum output of an electromagnetic driving unit can be reduced. Fuel flow through a passage radially outside the suction valve member and the firs passages. A fluid passage area is securable even when a lift amount of the suction valve member is small.

A fluid pump may include a power end, a fluid end having a cartridge bore, and a valve cartridge configured for insertion into, and removal from, the cartridge bore as a unit. The valve cartridge may include a cartridge body having a fluid inlet and a fluid outlet, a first valve assembly configured to control fluid flow through the fluid inlet, and a second valve assembly configured to control fluid flow through the fluid outlet.

A fluid pump may include a power end, a fluid end having a cartridge bore, and a valve cartridge configured for insertion into, and removal from, the cartridge bore as a unit. The valve cartridge may include a cartridge body having a fluid inlet and a fluid outlet, a first valve assembly configured to control fluid flow through the fluid inlet, and a second valve assembly configured to control fluid flow through the fluid outlet.