IL41894A - Step by step controlled servomechanism - Google Patents

Claims (2)

1. Step by step controlled servomechanlsm of the cylinder-type comprising a drive element movable in a case which it divides into two chambers , . said drive element . being provided with a plurality of receiver ports, a distributor adapted to be put in communication with the high pressure and the low pressure and to supply said receiver ports, wherein said distributor is fixed and provided with a number of supply or transmitter ports at least-equal to three-but-independent of the number of receiver ports, the transmitter ports being capable of being connected by permutation, in succession and in pairs, respectively to the low pressure and to the high pressure, the dis an e between the receiver port3 and thei length, on the one hand, the distance between the transmitter ports and their length, on the other hand, being such that, by the step by step displacement in one direction of the drive element, on one hand, it is possible to bring each time at least one receiver port between the two transmitter ports of a pair in such position that it communicates neither with one nor with the other of the transmitter ports but that any displacement in one direction or the other of the drive element purs in communication at least one receiver port respectively with one or the other of the two transmitter ports and, on the other hand, one of the transmitter ports of a following pair to be supplied with fluid communicates with a receiver port.

2. Servomechanlsm according to claim 1, wherein the relative positions and dimensions of said receiver ports and said transmitter ports are such that said ports are not capable of resulting in a communication between high and low pressure , whatever be the relative position of said drive element and said distributor and whatever be the pairs of transmitter ports supplied by the distributor. 3·- Servomechanism according to claim 2, wherein said distributor comprises four identical transmitter ports which are spaced equal distances apart and are capable of being connected to the high pressure as well as to the low pressure and receiver ports which are also identical and spaced equal distances apart, the sum of the effective length of each tran mitter port and the effective length of each receiver port being equal to twice the pitch of said transmitter ports, that is to say, twice the elementary pitch or unit advance, and the pitch of said receiver ports being equal to four times said elementary pitch. 4·- Servomechanism according to claim 1 wherein the transmitter ports can be connected only either to the high pressure or to the low pressure and the relative dimensions and positions of the transmitter and receiver ports meet the following conditions : c « r + £ + kD e + r +f. y D where : c is the distance between the edges (or faces) of the transmitter ports which co-operate to the hydraulic locking of the drive element. r is the length of each receiver port. D is the pitch of the receiver ports. d is the unitary pitch, i.e. the quotient of D hy the number of pairs of transmitter ports. £ is the number of pairs of transmitter ports which are simultaneously supplied in the¾ stabilized operation. e is the cumulated length of the & transmitter ports connected simultaneously to the same source of pressure in the stabilized operation, k is the difference between the rank numbers of the . receiver ports co-operating for the hydraulic locking in a given position. 6 is the overlapping i.e. the maximum value of the short travel that the drive element may effect in the vicinity of each position of balance without opening the distribution. 5o- Servomechanism according to claim 1 wherein the transmitter ports can be connected to the high pressure as well as to the low pressure and the relative dimensions and positions of the transmitter and receiver ports meet the following conditions : where the le ing as in claim 4.