Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
364 words
A control system for a hydraulic circuit apparatus including at least first and second hydraulic pumps of the variable displacement type, a first hydraulic actuator arranged for hydraulic connection with said first pump through first valve means to be driven thereby, and a second hydraulic actuator arranged for selective hydraulic connection with said first and second pumps through second and third valve means respectively to be driven thereby, wherein the order of priority for hydraulic connection is set beforehand in such a manner that when an operation signal for the second actuator is received while the first pump is inoperative, the first pump takes priority over the second pump for hydraulic connection with the second actuator, and when an operation signal for the first actuator is received while the first pump is in hydraulic connection with the second actuator, the first actuator takes priority over the second actuator for hydraulic connection with the first pump and the second actuator is brought into hydraulic connected with the second pump, and the displacement volume of the first pump and switching of the second valve means are controlled in such a manner that when the first pump which is in hydraulic connection with the second actuator is to be brought into hydraulic connection with the first actuator, the displacement volume of the first pump is once returned to zero before changing of the hydraulic connection, the control system comprising: first means for judging whether or not the first pump is in hydraulic connection with the second actuator when the operation signal for the first actuator is received, and generating a command for backing up reduction in the inflow of hydraulic fluid into the second actuator simultaneously when the displacement volume of the first pump begins to be returned to zero, when it is judged that the first pump is in hydraulic connection with the second actuator; second means for generating a command for switching the third valve means to an open position in accordance with the backup command from the first means; and third means for generating a command for initiating a displacement of the second pump in accordance with the backup command from the first means.
Claim 2
Dependent Claim
364 words
A control system for a hydraulic circuit apparatus including at least first and second hydraulic pumps of the variable displacement type, a first hydraulic actuator arranged for hydraulic connection with said first pump through first valve means to be driven thereby, and a second hydraulic actuator arranged for selective hydraulic connection with said first and second pumps through second and third valve means respectively to be driven thereby, wherein the order of priority for hydraulic connection is set beforehand in such a manner that when an operation signal for the second actuator is received while the first pump is inoperative, the first pump takes priority over the second pump for hydraulic connection with the second actuator, and when an operation signal for the first actuator is received while the first pump is in hydraulic connection with the second actuator, the first actuator takes priority over the second actuator for hydraulic connection with the first pump and the second actuator is brought into hydraulic connected with the second pump, and the displacement volume of the first pump and switching of the second valve means are controlled in such a manner that when the first pump which is in hydraulic connection with the second actuator is to be brought into hydraulic connection with the first actuator, the displacement volume of the first pump is once returned to zero before changing of the hydraulic connection, the control system comprising: first means for judging whether or not the first pump is in hydraulic connection with the second actuator when the operation signal for the first actuator is received, and generating a command for backing up reduction in the inflow of hydraulic fluid into the second actuator simultaneously when the displacement volume of the first pump begins to be returned to zero, when it is judged that the first pump is in hydraulic connection with the second actuator; second means for generating a command for switching the third valve means to an open position in accordance with the backup command from the first means; and third means for generating a command for initiating a displacement of the second pump in accordance with the backup command from the first means.
Claim 3
Dependent Claim
96 words
A control system as claimed in claim 1, further comprising fourth means for generating a command, in accordance with the backup command from the first means, for rendering the absolute value of a rate of change in the displacement volume of the first pump upon returning to zero and the absolute value of a rate of change of the displacement volume of the second pump after starting of its displacement substantially equal to each other and larger than maximum rates of change in the displacement volume of the first and second pumps during normal operation thereof.
Claim 4
Dependent Claim
104 words
3 . A control system as claimed in claim 1, wherein said third means includes means for deciding target displacement volumes for the first and second pumps based on the operation signal for the second actuator, means for selecting the decided target displacement volume as a target displacement volume for the first pump in the absence of the backup command from the first means, and means for selecting zero as a target displacement volume for the first pump and the decided target displacement volume as a target displacement volume for the second pump in the presence of the backup command from the first means.
Claim 5
Dependent Claim
126 words
A control system as claimed in claim 2, wherein said fourth means includes first and second means for generating preset maximum rates of change in the displacement volume of the first and second pumps during normal operation thereof, respectively, third means for generating preset rates of change in the displacement volume of the first and second pumps during backing-up operation thereof larger than the preset maximum rates of change during normal operation, means for selecting the preset rates of change generated by the third means as maximum rates of change in the displacement volume for the first and second pumps in the presence of the backup command from the first means, and means for inventing one of the selected preset rates to take a negative value.