Motors: expansible chamber type – Cyclically operable – Correlated throttle valve and distributor
Patent
1997-11-28
1999-07-06
Nguyen, Hoang
Motors: expansible chamber type
Cyclically operable
Correlated throttle valve and distributor
91336, 91350, F01L 1514
Patent
active
059185260
DESCRIPTION:
BRIEF SUMMARY
The object of the invention is a method in a pneumatic oscillating device for observing an obstacle within the length of the work stroke and continuing to oscillate, which oscillating device includes a double-acting cylinder, a principal control valve operating it, and a reversing valve, by means of which the principal operating valve is controlled. The invention also concerns a method for realizing the oscillating device.
Pneumatic oscillating devices are mainly used in the paper and pulp industry for moving doctor blades and jet pipes. The operating conditions are extremely difficult in terms of moisture and temperature. However, it is very important that the device is highly reliable.
Machines are known that move backwards and forwards, in which the back and forwards movement is usually accomplished by means of a pressure sensor. When the movement of the operating cylinder ends, the pressure increases on the compression side, which can be sensed and from which a signal can be transmitted to a reversing member. Another alternative is to use the pressure difference over the cylinder to indicate jamming. A third alternative is to use limit switches. A fourth alternative is based on a time limit providing a work stroke, which when exceeded gives a positive command for the return stroke. Most of the solutions are unreliable in operation and are liable to faults. None of the known solutions referred to above are able to deal in an acceptable way with a situation, in which the operating cylinder stops at a random obstacle in the middle of its work stroke. The operating cylinder is then quite simply jammed either completely in place or, even with a time limit, for a long time, which may be very detrimental to the device being operated.
The intention of this invention is to create a new type of method and oscillating device, by means of which the defects in the known devices can be corrected. According to the invention, data on the slowing or total stopping of the movement of the piston is obtained from the return side pressure, on the line of which a throttle is arranged to increase the normal pressure above the ambient pressure. By means of a simple pressure limit switch it is possible to send a signal from this pressure drop, most advantageously pneumatically, to a reversing valve, which then reverses the direction of the operating cylinder. If the obstacle is permanent, the same thing is repeated on the following stroke, when an oscillating device according to the invention then continues movement to the extent that it is possible without damaging construcions. An alarm signal is also sent to the reversing valve from this signal of the pressure limit switch.
Other advantages and embodiments of the invention are described later in connection with the example of its application.
In what follows, the invention is described by reference to the accompanying illustrations, which show the pneumatic diagram of one oscillating device according to the invention.
FIG. 1 shows the apparatus in the starting phase.
FIG. 2 shows the apparatus when operating.
The principal components of a pneumatic oscillating device according to the invention are an operating cylinder 1, a principal control valve 6, and direction valve 4, as well as pressure limit switches 7.1 and 7.2. The valves used are mainly pressure-controlled direction valves. In addition, the device includes means for soft starting, which are formed with the aid of valve 3. The spring loading of limit switches 7.1 and 7.2 is also part of the soft starting, so that in the starting phase these are in the alarm position, but change their status immediately they receive full pressure to their controller inlet on the other side. They are controlled on the other side through the pressure reduction valve 11. On one side of the soft starting valve there is spring control and on the opposite side the full pressure is controlled through throttle 3.1, when slowed operation is achieved. The pressure coming through pressure line 12 is then led to both connections 1.3 and 1.4 of
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patent: 3358563 (1967-12-01), Williams
patent: 3724331 (1973-04-01), Kobayashi
patent: 4002103 (1977-01-01), Martin
patent: 4700611 (1987-10-01), Kaneko
patent: 5490441 (1996-02-01), Hallstrom et al.
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