Motors: expansible chamber type – Cyclically operable – Working member controlled motive fluid for distributor motor
Reexamination Certificate
2001-09-28
2004-09-07
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Cyclically operable
Working member controlled motive fluid for distributor motor
C091S421000, C091S433000, C091S435000
Reexamination Certificate
active
06786129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor for cylinder control which is capable of detecting the operational state of a piston of a cylinder, for example of detecting that the piston has reached the end of its stroke, and to a cylinder device which incorporates such a sensor.
2. Description of the Related Art
Generally a large number of hydraulic cylinders are employed in machines which manufacture automobile parts and the like by metal or plastic casting using metal molding. Recently, in response to greater demands for accurate control of the forward and reverse stroke of such reciprocating cylinders used in production machinery for casting or the like, the machine operation has become more and more automated by the provision of sequence circuitry.
For example, as a prior art technique for cylinder control, as shown in
FIG. 12
, there is a control technique in which, by a limit switch device
2
which employs an analog switch or a contact switch or the like and which is fitted to a cylinder main device
1
, the position in the forward and reverse direction is detected, and a signal is despatched to a control board to stop the cylinder via a changeover valve (a solenoid valve). Furthermore, there is a control technique in which a sensor is housed within the cylinder and detects its position in the forward and reverse direction, and alters the stroke adjustment by a pulse signal, converts it into data by a detection device and again despatches the signal to the control board, and stops the cylinder via a changeover valve. Yet further, in Japanese Patent Publication Heisei 7-42965, there is proposed a technique of providing a sub-cylinder which is synchronized with said main cylinder, and of detecting and controlling the position in the forward and reverse direction by adjusting the amount of hydraulic fluid which flows into said sub-cylinder.
However, with these prior arts of cylinder control, the following problems still remain. In detail, in the case of a prior art limit switch device, the limit switch can easily suffer damage due to high temperature, large quantities of mold release agent or sludge, and it may happen that trouble with metal molds caused by this type of problem can be a great obstruction to production. Furthermore, since the tip portion is installed in the workplace, electrical leakage can easily happen even if waterproof type switches are employed because water, oil, and flash regularly impact thereon, and also there is the danger that the cables to the limit switch device may be cut. Yet further, along with the fact that it may be the case that no space is available to fit the limit switch device within the cylinder main body, also high precision adjustment of the limit switch device according to the size of the cylinder (according to its stroke) may be required. Moreover, if a plurality of cylinders are present, it is necessary to fit an individual limit switch device for each cylinder, and, along with inviting increase in the number of parts and high cost, there is the inconvenience that, if all of the cylinders are controlled using one circuit, this control becomes difficult because it becomes more complicated.
Also, if the sensors are housed internally, since pulse signals are employed, along with the requirements to adjust the drive section inside the cylinder in accordance with the cylinder stroke and to connect it to detectors, there is also a danger of erroneous operation being caused due to the magnetic field which is generated being weak.
Yet further, if control is performed according to the amount of hydraulic fluid which flows into a sub-cylinder, along with the necessity for a blocking member in the main cylinder, it is also necessary to adjust the amount of fluid which flows in. Accordingly there has been felt the desirability of providing a technique which utilizes a more simple structure and which also makes it unnecessary to adjust the amount of hydraulic fluid.
BRIEF SUMMARY OF THE INVENTION
The present invention has been conceived in consideration of the above described problems, and its objective is to provide a sensor for cylinder control and a cylinder device incorporating the same, which avoid the occurrence of erroneous operation due to the possibility of connections coming off from the cylinder, and which can make it unnecessary to perform adjustments according to the size of the cylinder, or to adjust the quantity of fluid.
The present invention uses the following structure for solving the above described problems. Namely, the sensor for cylinder control of the present invention is connected to a main cylinder having an internal cylinder chamber which is partitioned by a piston into two chambers, and which detects the operational state of said piston, and is characterized by comprising: an accumulator which is connected via a connecting conduit to one of said two chambers and whose interior is pressurized by fluid expelled from said one chamber; and a stop signal generation mechanism which generates a signal which stops the driving of said main cylinder due to pressure differential between said accumulator and said connecting conduit which is generated at the instant that the increase of pressure from said one chamber stops.
With this sensor for cylinder control, since the accumulator is incorporated which is connected via the connecting conduit to one of said two chambers so that its interior is pressurized by hydraulic fluid expelled from said one chamber, thereby the hydraulic fluid which is expelled from the chamber (said one chamber) of the main cylinder by the shifting of the piston flows into the accumulator via the connecting conduit, so that the pressure in the accumulator rises. And immediately before the piston, for example, arrives at the end of its stroke, a high surge pressure is generated, so that the pressure in the accumulator rises. Furthermore, at the instant that the piston arrives at the end of its stroke, the pressure of the hydraulic fluid in the chamber abruptly drops, so that the pressure supplied to the accumulator from the connection conduit abruptly drops. At this time, a pressure differential is caused between the accumulator which is in a high pressure state and the connecting conduit in which the pressure has abruptly dropped.
With the present invention, since there is provided a stop signal generation mechanism which generates a signal for stopping the driving of the main cylinder due to pressure differential between the accumulator and the connecting conduit which is generated at the instant that the increase of pressure from said one chamber stops, therefore the stop signal is generated due to the pressure difference which is generated at the instant that the piston arrives at the end of its stroke, and it is possible to stop the driving of the main cylinder. Accordingly, with the present invention, it is possible to stop the main cylinder reliably and also at high speed, directly before the piston arrives at the end of its stroke.
Furthermore, according to another aspect of the present invention, in this sensor for cylinder control, the technique may be employed of making the stop signal generation mechanism comprise a non-return valve provided in the connecting conduit which suppresses flow of fluid towards the one chamber, a first branch conduit of which a one end is connected to the connecting conduit between the accumulator and the non-return valve, a second branch conduit of which a one end is connected to the connecting conduit between the one chamber and the non-return valve, and a switch mechanism which is connected to the other end of the first branch conduit and to the other end of the second branch conduit and which generates the signal when the pressure in the first branch conduit becomes higher than the pressure in the second branch conduit.
With this sensor for cylinder control, due to the pressure differential which is generated at the instant when for example the piston reaches the end of its stroke, although an attempt is mad
Ando Seisakujo Co., Ltd.
Lopez F. Daniel
Nixon & Vanderhye PC
LandOfFree
Sensor for cylinder control, and cylinder device... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sensor for cylinder control, and cylinder device..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sensor for cylinder control, and cylinder device... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3271448