Patent Grant
10494072
The object of the present invention is a double effect, or double-acting, hydraulic actuating cylinder, particularly for hydraulic steering devices of outboard marine engines.
Outboard engines generally comprise an end for the fastening to the transom of a watercraft on which the engine is mounted so as to rotate around a substantially vertical steering axis.
The steering device comprises a closed hydraulic circuit with at least one pump actuated by steering means, such as a steering wheel, a rudder or the like, while the cylinder is slidably mounted on at least one rod coaxial thereto and sealingly protruding from at least one head of the actuating cylinder and carries a separating piston that divides the cylinder into two variable-volume chambers.
Each of the two chambers has at least one inlet/outlet for the hydraulic fluid, each connected to one of two inlet/outlet of the pump, and a sealing head for the relative sliding between cylinder and rod, the sealing head being integral with the cylinder itself.
Furthermore the rod is connected to a fastening bracket to fasten the cylinder to the engine, in a not slidable manner and in such a way as to allow the relative rotation of the engine with respect to the transom along an axis parallel to the axis of the rod.
Finally, there is a tiller arm fastened to the engine and integral with the cylinder, for steering the engine.
The above described configuration is the common configuration of the double-acting hydraulic actuators currently known and widely used.
This invention actually concerns hydraulic cylinders, regardless of their specific design, whether they are cylinders as described above, unbalanced cylinders or any other cylinder known in the state of the art.
Typical examples of such actuators are described in document EP 1488996 of the Applicant.
The various components of the known actuator cylinders are therefore widely used and tested in order to optimize the operation of the cylinders.
Although these devices perform their function satisfactorily, they have some drawbacks.
One of the most common drawbacks is the difficulty of disassembling the rod from the bracket fastening the cylinder to the engine. In fact, this fastening is usually carried out by nuts cooperating with threaded appendages obtained at the ends of the rod. The bracket has L-shaped end elements provided with corresponding through holes in which the threaded ends are inserted to be tightened by the nut.
The rod and cylinder are free to move relative to each other, so that the aforementioned fastening means are the only rotational constraint of the rod. Therefore, when disassembling the cylinder, a clamp tool must be used to allow the rod to be clamped when the bracket fastening nuts are unscrewed. On the other hand, the grip of this tool can damage the surface of the rod, resulting in a loss of seal between the cylinder and the rod.
Purpose of this invention is to implement a simple and inexpensive measure which allows the problem to be at least partially solved.
The purpose of the invention is achieved by a cylinder as described above, where the rod has at least one flattened surface to be grasped by a tool having at least one corresponding flat engagement surface to engage said flattened surface.
Preferably, the flattened surface is obtained in proximity of at least one, preferably both, the opposite ends of the rod. In this way, an ad hoc area for grasping the rod is created in at least one region not involved in the cylinder sliding, thereby facilitating the disassembly of the bracket without the risk of damaging the rod.
Since there are clamp elements with one of the two jaws having circular section, the purpose can be achieved by a single flattened surface, even though the maximum advantage is achieved when, at one or both ends of the rod, there are two diametrically opposed flattened surfaces to be grasped by means of a wrench or clamp tool having corresponding facing flat surfaces for the engagement with said flattened surfaces.
The ends of the rod may have a male thread, i.e. a threaded surface on the outer side of the rod, usually in an end zone having smaller section, for the coupling with a nut or a female thread, i.e. an axial threaded hole for the coupling with a bolt.
According to an embodiment, the flattened surface is obtained on the outer thread in proximity of the end of the rod. Advantageously, the length of the thread and the position of the flattened surface are such that, when the bracket is mounted on the rod with the nut tightened, the thread portion containing the flattened surface is not, at least partially, engaged by the nut.
This solution is functional, although not optimal. In fact, the flattened surface is obtained in an already weakened rod region, which is thus further weakened.
For this reason, the preferred solution provides that the flattened surface is obtained at a certain distance from the end of the rod, regardless of the type of thread used.
In an embodiment, the distance of the flattened surface from the end of the rod is such that, when the bracket is mounted on the rod, the flattened surface is positioned within the thickness of the end element of the bracket. This can be achieved, for example, by using an annular shoulder abutting the end of the rod. In this way, better protection against salt is provided in both the threaded region and the region weakened by the flattened surface, and greater strokes of the cylinder on the rod are allowed.
The protection can be increased even more by obtaining, on the rod in a backward position with respect to the flattened surface, an annular groove for the insertion of a sealing ring. Advantageously, the flattened surface has such a longitudinal extent to be at least partially enclosed in the thickness of the end element of the bracket in order to ensure the seal.
Further characteristics and improvements are object of the dependent claims.
The characteristics of the invention and the advantages descending therefrom will become more apparent from the following detailed description of the accompanying drawings, in which:
The figures in the present patent application show a preferred embodiment of the cylinder object of the present invention, but these figures should be considered for illustrative purposes only, to better understand concepts and advantages of the present invention.
In fact, these figures should not to be considered restrictive for the concept claimed in the Patent Application, the concept consisting of making an actuating cylinder with easily removable and replaceable fastening brackets.
Referring in particular to
The system comprises a closed hydraulic circuit 8 with at least one pump 9 operated by steering means, such as a steering wheel, a rudder or the like.
The cylinder 1 is slidingly mounted on at least one rod 2 coaxial to the cylinder 1, which sealingly protrudes from at least one head of the actuating cylinder 1 and carries a separating piston 2′ that divides the cylinder into two variable-volume chambers 2″ and 2′″.
Each of the two chambers has an inlet/outlet 111, 121 for the hydraulic fluid, each connected to one of two inlets/outlets of the pump 9, and a sealing head 3 for the relative sliding between the cylinder 1 and the rod 2, the sealing head 3 being integral with the cylinder itself.
The rod 2 is connected to a fastening bracket 4 to fasten the cylinder 1 to the engine 5, in a not slidable manner and in such a way as to allow the relative rotation of the engine 5 with respect to the transom along an axis parallel to the axis of the rod 2.
The translation of cylinder 1 along the rod 2 allows the engine 5 to rotate thanks to the arm 7, which transmits the movement of the cylinder 1 to the engine 5.
The fastening bracket 4 consists of a rod 41 positioned with its longitudinal axis parallel to the longitudinal axis of rod 2 and connected thereto through two L-shaped end elements 42 shaped as arms and defined “bull horn” in jargon due to their shape that calls to mind the horns of a bull.
The rod 2 has an end with reduced section 21 that is inserted into a through hole provided on the arm 42, which is correspondingly perforated. The end 21 is threaded and has flattened surfaces 22, i.e. diametrically opposed flat surfaces obtained, for example, by milling. The nut 43 tightens the threaded end with the interposition of a washer 44 thus fastening the rod 2 to the arm 42 in a similar way to what happens in the known devices.
The washer 44 has radial legs 44′ (
The flattened surfaces 22 are obtained on the thread close to the head 21 of the rod 2 and typically have a longitudinal extent less than the length of the threaded end. According to an improvement, advantageously the length of the thread and the position of the flattened surfaces 22 are such that, when the arm 42 is mounted on the rod 2 with the nut 43 tightened, the thread portion containing the flattened surfaces 22 is not, at least partially, engaged by the nut 43. In this way a tool, such as for example a wrench or clamp, can be used to loosen the nut 43 without the rod 2 starting to rotate. Once the nut is loosened, the tool is no longer required, so the extra stroke of the rod due to the end flattened surfaces can be limited to what is strictly necessary in order to ensure that the rod is grasped when applying the starting torque to unscrew the nut.
This solution with flattened surfaces on the threaded head is typically adopted on both ends 21 of the rod 2, even if there may be asymmetrical configurations with flattened surfaces arranged only on one end of the rod. In fact, when the nut has been completely removed, the flattened surfaces can be accessed again and can be used to loosen the nut arranged on the opposite end.
In this way the rod does not contribute to further weakening the reduced section part, thereby guaranteeing greater strength of the structure. In addition, no increase in the overall dimensions on the nut side has to be provided in order to allow the coupling with the wrench or clamp.
In both configurations shown in
This, however, has the disadvantage that in order to ensure that the head gasket of the cylinder can overlap the flattened area, the rod travel being unchanged, longer rods are required thus resulting in loss of seal.
To avoid this, a further embodiment provides that the flattened surfaces 22 are made at a distance from the end of the rod 2 such as to fall, in an assembled condition, inside the bull horn 42 by using, for example, an annular shoulder or an abutment washer 47 abutting against the end of the rod 2. This not only ensures maximum travel to cylinder 1 on rod 2, but also increases the saline protection. By providing the use of an O-ring 46 positioned in an annular groove arranged in a recessed position with respect to the flattened surfaces 22, as shown in
This embodiment with flattened surfaces arranged inside the thickness of the bull horn 42, both with and without sealing O-ring 46 or retaining ring 44, is particularly clever. In fact, as evident, if the flattened surfaces are hidden inside the bull horn, any grasping tool is completely unusable. However the inventors observed that, actually, when the rod of a cylinder should be disassembled from the bull horns provided at the ends, that is to say when a torque is applied to one or both nuts/bolts, the rod does not tend to rotate due to friction forces. Only after at least one of the nuts/bolts has been loosened, the rod begins to rotate, thus preventing the other nut/bolts from unscrewing. Hence the idea of hiding the flattened surface for grasping the rod. After one of the two nuts/bolts has been loosened, in fact, the rod can be pulled out of the corresponding bull horn thus freeing the flattened surfaces that can then be used to unscrew the other nut/bolt.
In order to achieve the maximum protection against splashes of water, another aspect of the invention involves working on the cylinder head, in particular on the fastening mechanism thereof.
In order to ensure effective protection against splashing, an aspect of the invention provides that the head 510 of the grub screw 51 is modified. Specifically, a chamfer 513 is emplaced in the conical part, thus creating a seat for housing an O-ring 61 and an abutting counter-step 514 as shown in
The head 31 can be of any type and shape and is not limited to what is depicted in the figures, for example it can be of a type consisting of two elements, one of which is a sealing element and the other a cap element.
In this case, the sealing element generates the seal, especially on gaskets, by radial action of the cylinder inner walls on the outer walls of the sealing element. On the other hand, the cap element generates a purely axial retaining action of the seal element so as to counteract the axial thrust of the fluid circulating inside the circuit.
The annular groove 313 can be obtained directly on the cap element to prevent it from being axially pulled out accidentally.
Further variations and improvements can be provided without departing from the guiding principle described above and claimed below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017000026657 | Mar 2017 | IT | national |
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| Number | Date | Country |
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| 205674060 | Nov 2016 | CN |
| 07208431 | Aug 1995 | JP |
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| Number | Date | Country | |
|---|---|---|---|
| 20180257751 A1 | Sep 2018 | US |
