Abstract:
An oil pressure operated pump for marine steering gears includes a multiple piston oil pressure operated pump controlled by a steering wheel, a valve housing mounted under the pump, a bottom cover closing the valve, the valve housing and the cover each including channels, threaded holes for reciprocal fastening thereof, non-threaded bores for oil pressure connections, a valve set lodged in the valve housing for non-return and adjustment of oil flow, the valve set including a generally parallelepiped shaped tubular shell having a generally external square shape, a central tubular through-hole, and lathe-turned ducts, a double acting oil pressure cylinder including a shaft movable in the central tubular through-hole for controlling a direction of an engine or rudder of a boat, and valves for controlling fluid flow and thereby movement of the shaft.

Description:
BACKGROUND OF THE INVENTION 
   Steering gears for boats, usually consisting of an oil pressure operated pump activated by the steering wheel are well known; this steering wheel controls, through its own valve set, all oil pressure operated double acting cylinder, axially acting by its mobile shaft on the direction of the engine or rudder of the boat. 
   SUMMARY OF THE INVENTION 
   The valve set of this oil pressure operated pump features essentially two, so-called non-return valves which also control the fluid supply and discharge in the two cylinder chambers features, two relief-valves of the maximum pressure and several channels connecting these valves to the pumping pistons, to the pump tank and to the chambers of the cylinder controlling the direction of the engine and of the rudder of the boat. 
   This invention specifically concerns the valve set which, in known steering gears, consists of one single machined metal housing in which the lodgment of these valves and the necessary channels form a geometrically complex arrangement with very close tolerances and their machining requires the utilization of numerically controlled multi-axis tooling machines involving very expensive equipments and long working hours. 
   This invention has the aim to obtain the valve set of the oil pressure operated pump for marine steering gears in a faster and much cheaper way. 
   According to this invention, the valve set consists of three separate elements which can be easily assembled by suitable junction means, for example by bolts. These three elements are:
     the valve housing mounted under the pump,   the cover closing the lower end of the valve housing,   the valve set lodged in the valve housing.   

   According to this invention, the valve housing and lower closing cover are obtained by pressure die-casting, preferably in aluminium alloy or zinc alloy or injection moulded in thermoplastic material. 
   These pressure die-casting or pressure moulded valve housings and lower cover are complete with all their necessary channels and holes for bolt-assembly. Threading of these holes through which to pass the bolts is the only one operation required. 
   The third element, i.e. the valve set, consists of a set of components lodged in a preferably parallelepiped shaped housing with square section and central through hole. This housing features necessary channels machined on a lathe with motor-driven X-Y-Z tools at a much lower cost than required for machining at the above mentioned job centers. 
   This solution according to the invention, not only permits to cut the production costs, as already explained before, but also facilitates maintenance of the non-return valves which can be easily replaced, whereas the known valve sets require cumbersome disassembly of its various components with the risk to cause damage to the valve packing. 
   Furthermore, according to this invention, the pump shaft on which the steering wheel of the boat is keyed, is provided with an easily replaceable seal kept in place on this shaft by a special shaped snug fitting cap to prevent the penetration of dust or water as normally happens with known gaskets. This shaft seal also protects the pump better from being damaged. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The oil pressure operated pump, according to this invention, is illustrated for exemplification purpose in the enclosed drawings in which: 
       FIG. 1  shows a top view of the valve housing, 
       FIG. 2  shows a view from below of the valve housing illustrated in  FIG. 1 , 
       FIG. 3  shows a section of the valve housing according to  3 — 3  in  FIG. 1 , 
       FIG. 4  shows a section of the valve housing according to  4 — 4  in  FIG. 1 , 
       FIG. 5  shows a section of the valve housing according to  5 — 5  in  FIG. 1 , 
       FIG. 6  shows a top view of the cover closing the lower end of the valve housing, 
       FIG. 7  shows a view from below of the bottom cover in  FIG. 6 , 
       FIG. 8  shows the section of the bottom cover according to  8 — 8  in  FIG. 6 , 
       FIG. 9  shows the section of the bottom cover according to  9 — 9  in  FIG. 6 , 
       FIG. 10  shows the section of the bottom cover according to  10 — 10  in  FIG. 6 , 
       FIG. 11  shows the central longitudinal section of the tubular shell of the set of non-return valves, 
       FIG. 12  shows a lateral top view of the tubular shell of the non-return valve set illustrated in  FIG. 11 , 
       FIG. 13  shows the longitudinal central section of the mobile piston axially controlling the non-return valves, 
       FIG. 14  shows the central cross section according to  14 — 14  in  FIG. 12  of the tubular shell of the non-return valve set, 
       FIG. 15  shows the central longitudinal section according to  15 — 15  in  FIG. 12  of the non-return valve set, 
       FIG. 16  shows the central vertical section of the bottom flange of the oil pressure operated pump, 
       FIG. 17  shows a top view of the, cap blocking the seal on the control shaft of the steering wheel, 
       FIG. 18  shows the central vertical section of the cap illustrated in  FIG. 17 , 
       FIG. 19  shows the central vertical section of the oil pressure pump assembly with the relevant valve set and seal on the steering wheel shaft according to this invention. 
   

   DETAILED DESCRIPTION 
   With reference to the  FIGS. 1  thru  5 ,  1  shows the valve housing obtained by pressure die-casting, preferable in aluminium alloy or zinc alloy or injection moulded with thermoplastic material. The valve housing features oil its upper surface, two small valves  2  respectively lodged in a recess  3  and each fitted with a tab  4  housing the valve spring. These small valves  2  are located rather peripherally so that they can be connected to the oil tank  5  and they are used to fill the pump with the oil before its utilization and for later topping tip of the pump. The said recesses  3  permit axial shifting of the ducts  6  communicating with the valve set  7  towards the centre of the valve housing  1 ; these ducts  6  being the suction and compression lines of the oil pump  8 , as will be explained hereinafter. Two relief valves  9  are also lodged in the valve housing  1 , which relief valves  9  are connected by small channels  10 ,  35  and branch pipes  11  to the oil pressure operated cylinder chambers as will be explained hereinafter. 
   The valve housing  1  also features a boring  12  for pressure compensation and balancing of the valve set  7 , debouching, through radial recessing  13  of the offset borings, into the pipe  14  connected to the pump tank  5 . This branch pipe  14  has also the function, together with a similar pipe  15 , if provided, to install two or more oil pressure operated pumps complete with steering wheels located in different parts of the ship. 
   The top view of the valve housing  1  shows suitably threaded holes  16  to secure the housing  1  by bolting it to the bottom of the pump  8 , while the view from below of the valve housing  1  shows threaded holes  17  for fastening the housing by bolting it to the lower cover  18  closing the valve set. 
   The upper surface of the valve housing  1  also features a dowel  19  for its centering with the lower surface of the pump  8  during assembly, while three blank holes  20 , in which to insert the centering dowels  21  for assembly of the lower cover  18 , are bored in the outer bottom surface of the valve housing. 
   A preferably rectangular shaped recess  22  is machined inside the valve housing  1  in which to lodge oiltight the valve set  7  which should also preferably be rectangular shaped. 
   Internally, the valve housing  1  also features some zones  23  to lighten the structure. 
   In the  FIGS. 11  thru  15 , the valve set  7  acts as non-return, supply and discharge valve of the two oil pressure operated cylinder chambers. This valve set  7  features a preferably parallelepiped square section shell  24  with a tubular internal shape  25  in which two ball valves  26  are lodged fitted with the relative thrust/spring and relative seat. Furthermore, a mobile plunger  27  provided with end shanks  28  resting on the balls  26  acting as valves are also mounted in the tubular shell  24 . The valves  26  and the relative plunger  27  are acting as non return valves to prevent the fluid from flowing to or from the cylinder chambers when the steering wheel is in rest position and to let the fluid flow to and from the cylinder chambers when the steering wheel is actuated, as will be explained hereinafter. 
   The delivery or return flow of the pump  8  passes through the valve housing  1  by means of surface machined recesses  3  and ducts  6  and then reaches the axially centred radial ducts  29  of the valve set  7 . The delivery or return flow passes through the ball valves  26  to reach the radial ducts  30  which are axially disaligned to save space, and then to reach the bottom cover  18 , as explained hereinafter. 
   The raceway  31  is branched off from the inside  25  of the valve set  7  and is radially disaligned with respect to the centre line of the tubular shell  24  and this raceway  31  is connected to the channel  12  of the valve housing  1 , which in turn is connected to the tank  5  of the pump  8 . 
   The above mentioned raceway  31  is also connected to the ducts  32  and circumferential channels  33  of the plunger  27  so as to permit discharging of any overpressure, generated in the valve set  7  and in the hydraulic fluid circuits, into the pump tank  5 . 
   The  FIGS. 6  thru  10  show the bottom cover  18  of the valve housing  1  featuring on its upper surface two channels  34  corresponding to the radial and offset ducts  30  of the valve set  7 . These channels  34  terminate at the lower surface of the bottom cover  18  with threaded holes  11  branched to the two chambers of the oil pressure operated cylinder. An additional duct  35  is provided adjacent to the said duct  34  inside the hole  11  connecting each cylinder. By means of a surface machined recess  36  by which the ducts are disaligned, the duct  35  is connected to the ducts  10  of the relief valve  9  discharging in the tank  5  of the pump  8 . Any overpressure generated in the cylinders and valve set is automatically discharged into the tank of the pump  8  through these relief valves  9 . 
   The bottom cover  18  also features two channels  37  connected to the ducts  14 ,  15  which in turn are connected by threaded holes  38  to one or more other oil tanks if a multiple steering gear is provided. 
   For information purposes, most of the elements previously described are assembled in  FIG. 19  in order to explain how the pump in question is operating. The part of the pump  8  to be secured to the valve set  1  is flange shaped  39 , featuring two ducts  40  matching the disaligned recesses  3  and the ducts  6  of the valve housing  1 . The ducts  40  communicate by two separate radial and opposed recesses  41  with the chambers  45  of the pump pistons  42 . 
   As is known, the steering wheel  100  ( FIG. 19 ) is mounted at the external end of the shaft  43  of this pump. By means of a cam device  44 , the said shaft  43  drives several small pistons  42  for intake or compression of the oil in their chambers  45  as illustrated by the arrows, thus filling or emptying the chambers of the oil pressure operated cylinder driving the engine or steering gear of the boat. 
   This lower end of this flange  39  closes the bottom of the oil tank  5  and features through holes  46  for the feed valves  2  of the equipment. 
   The oil taken in or compressed by the pump pistons is conveyed through the threaded fitting  11  in connection with the chambers of the flow dynamic cylinder and thus reaches the ball valve  26 . The fluid, pressurized in one of the cylinder chambers (at the left in  FIG. 19 ), pushes the ball valve  26  outwards and the plunger  27  in the opposite direction, thus pushing with its shank  28  the opposite ball valve  26  causing it to open and let the return fluid flow from the other cylinder chamber. This is achieved by turning the wheel in a given direction, whereas the inlet and return flows of the oil will be reversed when turning the wheel in the opposite direction, causing a similar reversed operation of the valve set. By the way, the ball valves  26  are at rest in closed position when the wheel is not moved, thus creating a set of non-return valves and this is particularly important to keep the engine or the rudder of the boat stopped, without any undesired movement of the engine or rudder in either direction. 
   The above described oil pressure operated pump features a valve set directly secured to the pump, but it is also possible to keep this valve set separated from the pump, but in such case, proper ducts shall be provided for connection to the pump and to the cylinder, as well as an element in which to lodge the suction valve connected to the inner part of the tank  5 . The pump is provided with a seal  47  of any type such as a Corteco or O-ring fitted between the wheel shaft  43  and the pump casing  8  to prevent dust or fluids from entering the pump. 
   According to this invention, this seal  47  is easy to install, to fix, to remove and to replace, by means of the cap  48  provided with holes  49  through which to pass the fastening screws and fitted with a metal or thermoplastic insert  50 . The outer edge  51  of this cap  48  has the shape of an inwards turned peak adherent to the wheel shaft  43 , thus creating a perfect seal between the shaft and the outer pump walls. 
   Obviously, the invention here generally described, but without limiting, may be subject to variations and adjustments; some of its parts may be replaced by others having the same aims, based upon the various circumstances and on the nature of the oil pressure operated control pump.