Land vehicles: bodies and tops – Tops – Let-down type top
Reexamination Certificate
1998-11-12
2001-07-31
Pedder, Dennis H. (Department: 3612)
Land vehicles: bodies and tops
Tops
Let-down type top
C296S107080, C092S00500L, C091S001000
Reexamination Certificate
active
06267432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hydraulic actuating system for movable parts, particularly for hinged movable covers on vehicles with at least one working cylinder that has a piston with sealing means fitted against a cylinder wall whereby a control unit is connected to one or all cylinders and with a pressure sensor in a common hydraulic circuit. The invention relates further to a vehicle convertible top and a method to adjust its position and/or identify a working cylinder in a hydraulic actuating system whereby the pressure in the hydraulic circuit is monitored by a pressure sensor and where a corresponding signal is received and analyzed by a control unit.
2. The Prior Art
A hydraulic actuating system for a vehicle top is known from patent AT-PS 402 280, whereby a pressure sensor is placed in the common hydraulic circuit of the working cylinder and whereby the pressure sensor is connected to a control unit for separate switching elements of the cylinder. The outgoing signal of the pressure sensor is used to control the end-of-stroke position of each cylinder taking into account the progression of the pressure values and a predetermined switching sequence of the individual switching elements. Without costly separate end-position switches at each cylinder or the corresponding part of a convertible top system, the control system for the entire system can be simplified; but the cylinders may only be controlled in a predetermined switching sequence and changes in the switching sequence would necessitate a new setup for the entire control program. Above all, there is no possibility of recognizing intermediate positions of the working cylinder and to allow, for example, overlapping movements of the cylinders or with external operations.
It is therefore the object of the invention to produce a hydraulic actuating system for general utilization purposes, which avoids the above-mentioned disadvantages with maximum simplicity and which makes possible in regard to production, assembly and maintenance, a cost-effective construction, a flexible programmable control system as well as a time-saving overlapping or parallel operating work cycle of the cylinder in the hydraulic actuating system. Additional objects of the invention are a vehicle convertible top system, which would also have the above mentioned characteristics and would provide a simple, inexpensive and reliable method for controlling positions and/or identification of a working cylinder in a hydraulic actuating system.
SUMMARY OF THE INVENTION
The first object is solved, according to the invention, in that means is provided to cause modulation of pressure in a cylinder. Altered output signals of a pressure sensor corresponding to the pressure modulation is transmitted to the control unit and can be used for position control and/or identification of one working cylinder out of a plurality of working cylinders or for identification of all working cylinders. Said pressure modulation is superimposed on the general operating flow in the system and can be easily identified by the control unit. According to requirements, the position of each piston can be identified through the described method during the course of a piston stroke, including also intermediate positions between the end positions. It is possible without great effort to obtain a feed-back signal for additional position sensors and subsequent action when intermediate positions have been reached by the piston. This also makes production and assembly of the hydraulic actuating system for general utilization more cost-effective, more simple and reliable since no separate position sensors and fewer components, cables and connectors have to be mounted or installed. The control unit can determine the maximum position with less input signals and safety is increased by continuous pressure monitoring. Pressure modulation can, of course, also transmit an individual signal for actuation of each single cylinder.
The above mentioned advantages are increased even more when a plurality of cylinders, which are controlled by separate switching elements, are connected with the control unit and the pressure sensor within the hydraulic circuit. In this case, subsequent operational cycles of separate cylinders can be designed more flexibly and operation of a subsequent cylinder can be started even when the previous cylinder is still in an intermediate position. Even then, the hydraulic actuating system remains cost-effective and very simple in its construction since it has only one pressure sensor and one control unit, which can be designed very simply and economically.
In addition or alternatively to the position control, in a system with a plurality cylinders wherein it is desired to identify at least one working cylinder, a cylinder can be equipped with means for pressure modulation according to a typical pattern of the pressure modulation for identifying said cylinder. An individual recognition is realized through an identifying pattern of each single cylinder or group of simultaneously operating cylinders so that overlapping or parallel control of several cylinders or group of cylinders is made possible in a very simple way. The identification of each cylinder can be accomplished by the amount and/or characteristics of the pressure change, whereby the first variant depends of course on the signals of the installed pressure sensors and whereby general pressure fluctuations can be a nuisance. It is therefore preferred to use an identification of the type of a “bar code”, whereby each cylinder or cylinder group is identified by a typical pattern of pressure fluctuation (fluctuation from the normal pressure conditions in relation to the corresponding position of the piston), independent from its absolute value, but with consideration of the prior patterns of pressure fluctuation. The control unit may be programmed more flexibly since the cylinders may be controlled in a different sequence, if so desired, and where the entire program will not have to be rewritten, but only the codes of the cylinder identification have to be changed.
According to additional invention characteristics, the means for pressure modulation have at least one portion that has a different size cross-sectional area in relation to other portions; and this divergent cross-sectional area is on at least two parts that move past one another and come into contact with one another during a piston stroke. This type of design makes it unnecessary to place additional components on the cylinder and thereby reduces expenses in construction, production, assembly and increases operational dependability based on the low number of components that can break down.
In a first embodiment of the invention there is a deviation of the cross-sectional area caused by a circumferential outwardly extending indentation which preferably extends around the entire circumference of the cylinder wall and/or the passageway through which the piston rod extends whereby the pistons have a seal fitted against the cylinder wall or a seal on the piston rod is fitted against the passageway for the piston rod. At the location of the deviation in cross-sectional area, whereby only the absolute value of the cross-sectional area is taken into consideration and not its shape, the elastic seal of the piston or the piston rod is expanded while it still retains its sealing effectiveness and this makes an easier movement of the piston in the cylinder possible. As a result of this increase in cross-sectional area, a decrease in pressure in the circuit will occur, which will cause a corresponding output signal by the pressure sensor when the piston passes the portion of deviation cross-sectional area. The temporary pressure drop results in a pressure modulation that is processed through the control unit, which also identifies passing of the piston through the portion of the cylinder with the increase in cross-sectional area or the action of the cylinder caused by this increase in cross-sectional area.
The outwardly-exte
Dykema Gossett PLLC
Hoerbiger Hydraulik GmbH
Pedder Dennis H.
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