Abstract:
A hydraulically damped mounting device has a first anchor part in the form of a clip and a second anchor part in the form of a boss connected to the cup by a deformable wall. The deformable wall bounds a working chamber for hydraulic fluid which is connected to a compensation chamber by a passageway. A strap is provided extending around the mounting device which is fixed to either or both of the anchor parts. The fixing may be via a clip.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hydraulically damped mounting device. Such a device usually has a pair of chambers for hydraulic fluid, as a pair of chambers for hydraulic fluid, connected by suitable passageway, and damping is achieved due to the flow of fluid through that passageway. 
     2. Summary of the Prior Art 
     EP-A-0115417 and GB-A-2282430 discussed a type of hydraulically damped mounting devices for damping vibration between two parts of a piece of machinery, e.g. a car engine and a chassis, referred to as a “cup and boss” type of mounting device, in which a “boss”, forming one anchor part to which one of the pieces of machinery was connected, was itself connected via a deformable (normally resilient) wall to the mouth of a “cup”, which was attached to the other piece of machinery and formed another anchor part. The cup and the resilient wall then defined a working chamber for hydraulic fluid, which was connected to a compensation chamber by a passageway (usually elongate) which provided the damping orifice. The compensation chamber was separated from the working chamber by a rigid partition, and a flexible diaphragm was in direct contact with the liquid and, together with the partition formed a gas pocket. 
     In the hydraulically damped mounting devices disclosed in the specifications discussed above, there was a single passageway. It is also known, from other hydraulically damped mounting devices, to provide a plurality of independent passageways linking the chambers for hydraulic fluid. 
     FIG. 1 of the accompanying drawings shows one example of a “cup and boss” type of mounting device which has been disclosed in our GB-A-2282430. The mounting device is for damping vibration between two parts of a structure (not shown), and has a boss  1  connected via a fixing bolt  2  to one of the parts of the structure, and the other part of the structure is connected to a generally U-shaped cup  4 . A resilient spring  5  of e.g. rubber interconnects the boss  1  and the cup  4  and extends across the mouth of the cup  4 . Thus, a working chamber B is defined within the mount, bounded by the resilient spring  5  and the partition  7 . 
     The interior of the partition  7  defines a convoluted passageway  9  which is connected to the working chamber  8  via an opening  10  and is also connected via an opening  11  to a compensation chamber  12 . Thus, when the boss  1  vibrates relative to the cup  4  (in the vertical direction in FIG.  1 ), the volume of the working chamber  8  will change, and hydraulic fluid in that working chamber  8  will be forced through the passageway  9  into, or out of, the compensation chamber  12 . This fluid movement causes damping. The volume of the compensation chamber  12  needs to change in response to such fluid movement, and therefore the compensation chamber  12  is bounded by a flexible wall  13 . 
     In use, the force received by the mounting device is principally parallel to the fixing bolt  2 , and this direction defines an axis of the boss  1 . 
     The above structure is generally similar to that described in EP-A-0115417, and the manner of operation is similar. In EP-A-0115417, the partition supported a diaphragm which acted as a boundary between fluid in the working chamber and a gas pocket. In the arrangement shown as FIG. 1, there is an annular diaphragm  50  which is convoluted. That diaphragm  50  is held on the partition  7  by an upper snubber plate  22 , that snubber plate  22  is held in pace by a ring  40 , which is clamped to the partition  7  and to the cup  4 , by a clamping ring  41 . The resilient spring  5  is also connected to the ring  40 . The upper snubber plate  22  has openings  21  which permits fluid in the working chamber  8  to contact the diaphragm  50 . 
     In the arrangement shown in FIG. 1, the passageway  9  is in the form of a spiral, and the internal dimensions of that spiral are uniform. 
     Under normal operation, the resilient wall is sufficiently strong to resist the forces that will be applied to it due to movement of e.g. the engine relative to the chassis. However, if the vehicle is involved in a crash or in some extreme driving conditions, very large forces can be applied to the mount due to movement of the engine relative to the chassis, and it is desirable to provide additional restraint on the movement of the boss relative to the cup to prevent excessive movement of the engine. It is therefore known to provide a strap, usually of braided steel or wire, which extends around the mounting device so as to pass over the boss and under the cup to provide a restraint on the total movement of the mounting device. 
     In the known arrangement, the strap is not fixed to the rest of the mounting device, but lies in grooves where it is held by the force from the resilient wall interconnecting the cup and boss forcing the cup and boss outwardly away from each other, with that force being resisted by the strap. 
     SUMMARY OF THE INVENTION 
     In such arrangements, there is a risk that the strap may become loose from the mounting device, particularly during the assembly process of the vehicle on which the mounting device is used and therefore at its most general the present invention proposes that the strap is fixed to the cup and/or the boss. 
     Thus, the present invention may provide a hydraulically damped mounting device comprising: 
     first and second anchor parts connected by a first deformable wall; 
     a working chamber at least partially bounded by the first deformable wall; 
     a compensation chamber for the hydraulic fluid, the compensation chamber being bounded by a second deformable wall; 
     a passageway for the hydraulic fluid interconnecting the working and compensation chambers; and 
     a strap extending between the first and second anchor parts and fixed to at least one of said first and second anchor parts. 
     In such an arrangement, the first anchor part may be formed by the cup, and the second anchor part by the boss. Preferably, the strap is fixed to the corresponding anchor part by a clip fixedly secured to the strap. 
     In some embodiments of the present invention, the strap is fixed to the boss. Then, and appropriate clip may have a projecting part which is received in a bore in the upper surface of the boss to provide suitable engagement. 
     Normally, the strap forms a closed loop which extends from the clip secured to the boss around the base of the cup and back to the clip. Another possibility, however, is to provide a strap with free ends, with clips fixedly secured to the respective ends, and the clips then being secured to the boss. Such a strap may loop around the base of the cup in the same way as for a closed looped strap, but the use of two clips may make the respective ends of the straps to be fixed to different parts of the boss. 
     Furthermore, it is then desirable that the base of the cup has at least one deformable tang to define a slot into which the strap may be received and the tang deformed to hold the strap to the base. Preferably, there are multiple tangs, and preferably the slots open axially inwardly. 
     In other embodiments, the strap is fixed to the cup, again, for example, by a suitable clip. There may also be a location clip fixed to the boss which engages the strap and secures the strap to the boss. However, it is then preferable that the strap slides in such a location clip. This enables the position of the strap to be adjusted to ensure that it is symmetric about the mounting device. 
     Again, with the strap fixed to the cup, it is possible for the strap to be a closed loop, or for the strap to be formed by strap parts with free ends extending from the clip, with those free ends then being secured to the boss either by fixed or by adjustable clips. 
     Guides attached to the strap may also be provided to fit to the side of the mounting device intermediate the top of the boss and the base of the cup. The guides are preferably integral with a strap. These guides distribute the load on the mounting device from the strap, and also may assist in correct positioning of the strap. 
     Alternatively, or in addition, resilient pads may be provided between the strap and the side of the mounting device intermediate the top of the boss and the base of the cup. Such pads may, for example, be moulded onto the flange which attaches to the clamping ring which holds the partition onto the cup. The use of such pad enables the stiffness imparted to the mounting device by the strap to be adjusted to a suitable value. It also prevents damage to the sides of the mounting device. 
     It is also known to mount a heat shroud on the boss, which extends over the resilient wall to reflect away from the mount heat from surrounding heat sources, such as the vehicle engine. In a development of the present invention, the orientation clip has a projection therefrom extending away from the boss onto which the heat shroud is fitable. This is advantageous since the heat shroud cannot then be fitted until the strap itself has been fitted, to prevent erroneous assembly. The orientation clip may be the clip fixed to the strap which secures the strap to the boss. Alternatively, the orientation clip may slide on the strap, for example if the strap is fixed to the cup by another clip. 
     The strap should be substantially inelastic. Thus, the stiffness (i.e. the force needed to achieve unit elongation) should be at least 1×10 6  Nm −1 , preferably at least 2×10 6  Nm −1 . Note that a stiffness greater than 10×10 6  Nm −1  may be difficult to achieve with sufficiently light materials. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings in which: 
     FIG. 1 is a cross-sectional through a known hydraulically damped mounting device and has already been discussed; 
     FIG. 2 is a perspective view of the first embodiment of the present invention; 
     FIG. 3 shows part of the hydraulically damped mounting device of FIG. 1; 
     FIGS. 4 a  and  4   b  shows sectional views through an orientation clip used in the embodiment of FIG. 1, with the view of FIG. 4 b  being taken perpendicular to the view of  4   a.    
     FIG. 5 is a view of the embodiment of FIG. 2 with a heat shroud fitted thereto; 
     FIGS. 6 a  and  6   b  are perspective and sectional views respectively of the cup of the embodiment of FIG. 2; 
     FIG. 7 is a side view of the first embodiment of FIG. 2; 
     FIG. 8 is a perspective view of a second embodiment of a hydraulically damped mounting device according to the present invention; 
     FIG. 9 is a perspective view of a third embodiment of hydraulically damped mounting device according to the present invention; 
     FIG. 10 gives a view of a strap to be used in the third embodiment; 
     FIG. 11 is partial sectional view showing the fixing of the strap  50  in the third embodiment; 
     FIG. 12 is a perspective view of the boss of the third embodiment; 
     FIG. 13 is a sectional view through the boss of FIG. 12; 
     FIG. 14 is an orientation clip used in the third embodiment; 
     FIG. 15 is perspective view of a fourth embodiment of a hydraulically damped mounting device according to the present invention; 
     FIG. 16 is a side view of the fourth embodiment; 
     FIG. 17 illustrates the strap to be used in the fourth embodiment; and 
     FIG. 18 illustrates side view of a fifth embodiment, being a modification of the fourth embodiment. 
    
    
     DETAILED DESCRIPTION 
     FIG. 2 illustrates a first embodiment of a hydraulically damped mounting device according to the present invention. In many ways, the mounting device similar to that of FIG. 1, and the same reference numerals are used to indicate corresponding parts. In particular, there is a boss  1  which is connected to a cup  4  via a resilient spring  5  of eg rubber. The internal structure of the mounting device of FIG. 2 may be similar to that of FIG. 1, and conventional variations to that internal structure such as discussed in eg EP-A-0115417 may also be used. 
     The embodiment of FIG. 2 differs from the mount of FIG. 1 in that it has a strap  50  which extends around the mounting device and has a clip  51  thereon, by which the strap  50  is secured to the boss  1 . The strap  50  then extends over the resilient spring  5 , and around the cup  4  to pass under the base of the cup  4 . FIG. 3 shows the boss  1  in more detail. In particular, the boss has a plurality of blind boxes  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58  therein, one  58  of which is shaped to receive the orientation clip  51 . The orientation clip  51  is shown in more detail in FIGS. 4 a  and  4   b  and has a base part  60  which fits the bore  58  and a projection part  61  which in use will project upwardly from the boss  1 , and be connected to a heat shroud as will be explained in more detail later. The base and projection part  60 ,  61  are integrally moulded together around the strap  50 , as can be seen in more detail in FIG. 4 b , which illustrates that the projection part terminates in a plate  62  which overlies the strap  50  and has projections  63 ,  64  which merge with the base part  60 , The result is that the strap is wholly enclosed within the clip  51 . The projections  63 ,  64  are shaped so as to match the walls  65 ,  66  of the boss  1  adjacent the bore  58 . The clip  51  then has a snap-fit into the bore  58 , thereby securing the strap  50  to the rest of the mounting device. 
     As was mentioned above, a heat shroud may be fitted to the mount. This is illustrated in FIG. 5 which corresponds to FIG. 2, but with the heat shroud  70  in place. The heat shroud  70  covers the resilient spring  5 , and so protects it from external heat sources. The shroud  70  has a first opening  71  through which the bolt  2  passes, and a second opening  72  which fits over the projecting part  61  of the orientation clip  51 . The clip  51 , and in particular the projection part  61 , thus forms the structure for securing the heat shroud  70  to the mount. This has the advantage that, in the absence of the strap  50 , the heat shroud  70  cannot be fitted. 
     FIGS. 6 a  and  6   b  show the cup  4  to illustrate the securing of the strap  50  to the cup  4 . In particular, the base of the cup  4  has a transverse groove  80  which receives that part of the strap extending around the base of the cup, and the base of the cup  4  also has two tangs  81  projecting from a side wall of that groove  80 . The tangs  81  overlie the strap  50  when the strap  50  is in the groove  80 . The tangs may then be deformed towards the base of the cup, forcing the strap into slots  82  in the base of the cup  4  and so providing a secure fixing of the strap  50 . It can be seen that the tangs  81  project radially inwardly, as this prevents the strap  50  slipping out of the groove  80  and off the base of the cup  4 . It is less likely that the strap will slip radially inwardly, since the shape of the mounting device means that the strap would then extend around a larger circumference than it does in the position in which it fits in the groove  80 . 
     The resulting mounting device is shown in FIG.  7 . This view shows how the groove  80  is on the opposite side of the centre plain  84  of the mount to the orientation clip, the position of which is indicated by the projection part  61  which projects from the heat shroud  70 . 
     The strap  50  is preferably of a fabric material, such as woven Nylon or Kevlar. This allows the strap to be light, occupy little space, and be economical, without compromising the strength of the strap. The use of such fabric straps may thus be more beneficial than the known straps of braided steel. 
     FIG. 8 illustrates a second embodiment of the present invention. FIG. 8 is similar to FIG. 2, and the same reference numerals are used to indicate the corresponding parts. Again, the internal structure may be similar to FIG. 1, and conventional variations may also be used. 
     In FIG. 8, the strap has guides  90  integrally fitted thereto, which fit on the sides of the mounting device which the strap  50  passes. The guides  90  have the effect of distributing the loading due to the strap  50  on the mounting device around the periphery of the cup  4 , and thus reduce risk of deformation of the clamping ring  41 . Apart from the guides  90 , the mounting device of FIG. 8 may be similar to that of the first embodiment of FIG. 2, and have a heat shroud similar to that shown in FIG.  5 . 
     In the first and second embodiments described above, the clip secured to the strap engages the boss. A third embodiment will now be described in which the clip engages the cup. Components of this third embodiment which correspond to components of the first or second embodiments are indicated by the same reference numerals. Again, the internal structure may be similar to FIG. 1, and conventional variations may also be used. 
     FIG. 9 shows a general schematic view of the third embodiment, and is similar to FIG.  5 . However, in this embodiment, the strap  50  has a clip  100  fixed thereto in a position which underlies the cup  4  when the strap  5  is positioned on the mount. The strap  50  extends around the mount in a similar way to strap  50  of FIG. 5, and again engages an orientation clip, the projecting part  61  of which can be seen in FIG.  9 . However, the orientation clip of this embodiment is not fixed to the strap, as will be explained in more detail later. Instead, the strap  50  can slid in the orientation clip, to ensure that the strap is symmetrically positioned on the mount. 
     FIG. 10 illustrates the strap  50  and the clip  100  in more detail. The clip  100  has an elongate part  101  which is moulded around the strap  50 , to secure the clip  100  to the strap  50 . That elongate part  101  has projections  102  extending therefrom which projections  102  engage suitable bores in the cup  4 . That engagement can be seen more clearly in the view of FIG. 11, in which the parts of the mount other than the cup  4  and strap  50  are omitted for the sake of clarity. Thus, the engagement of the projections  102  with the corresponding bores of the cup  4  fixes the clip  100  to the cup  4 , hence fixing the strap  5  to the mount. 
     The strap  50  extends around the mount to overlie the boss  1  an orientation clip  103  is then secured to the boss  1  in a manner similar to the connection of the orientation clip  51  in the earlier embodiments. As shown in FIGS. 12 and 13, the orientation clip  103  extends in to a bore  58  in the boss  1 , to fix the orientation clip to the boss  1  in a manner similar to the fixing of the orientation clip of the first and second embodiment. However, in this embodiment, the strap is not fixed to the orientation clip  103 . Instead, the orientation clip has a slot  104  extending therethrough which lies generally parallel to the top surface of the boss  1 , when the orientation clip  103  is mounted in the boss. The strap is then inserted in to the slot  104  through a mouth  105 , that mouth having a lip  106  which holds the strap in the slot  104 . The strap is, however, free to slide in the slot  104  and thus the position of the strap  50  around the mount can be adjusted by such sliding, to ensure that there are equal amounts of strap on each side of the mount, to prevent un-equal loading of the strap. 
     Note that FIG. 14 also shows that the orientation clip  103  has a downwardly projecting tang  107  which engages the bore  58 . The structure of the mount, the heat shield  70 , etc of this third embodiment may otherwise be similar to the first and second embodiment, and therefore will not be described in further detail. 
     In all the embodiments described above, the strap  50  extends wholly around the mount. This is not essential and a fourth embodiment will now be described in which the strap is discontinuous. This embodiment will be described with reference to FIGS. 15 to  17 . The parts which correspond to parts of one of the earlier embodiments are indicated by the same reference numerals. Again, the internal structure may be similar to FIG. 1, and conventional variations may also be used. 
     In this fourth embodiment, a clip  110  is fixed to the cup  4 , and has two strap elements  111 ,  112 ;  113 ,  114  extending therefrom. Two strap elements  111 ,  112  extend around one side of the mount to an orientation clip  115  fixes to the boss  1 , and the other strap elements  113 ,  114  extend from the clip  110  to a second orientation clip  116  fixed to the boss  1 . There is thus a gap in the strap between the orientation clip  115  and  116 . 
     The side view of FIG. 16 shows that the strap elements  111 ,  112  form a V-shape with the base of the V being at the orientation clip  115  and the top thereof being at the clip  110 . Thus, the forces on the mount due to the strap elements  111 ,  112  are symmetric. The same in true of the strap elements  113 ,  114 . 
     The clip  110  has projections  117  extending therefrom which engage the cup  4  in a way similar to the projections  102  of the third embodiment. Thus, the clip  110  is fixed to the cup  4 . The orientation clips  115 ,  116  may also be fixed the their respective strap elements, or alternatively may act as a clamp on those strap elements, to enable to position of the strap elements to be adjusted. FIG. 17 also shows that each orientation clip  115 ,  116  has a corresponding projection  118 ,  119  which extend in to the boss  1  and fix the orientation clips  115 ,  116  to the boss, in a manner similar to that illustrated in FIG.  13 . 
     FIG. 18 illustrates an embodiment which is a modification of the fourth embodiment, with a similar strap arrangement. Components in FIG. 18 which correspond to those in FIGS. 15-17 are indicated by the same reference numerals and will not be described in further detail. 
     In the fifth embodiment of FIG. 18, resilient pads  120 ,  121  are provided on the sides of the mounting device. They may, for example, be moulded onto the clamping ring  41  in FIG.  1 . Note that, although not visible in FIG. 18, the pads  120 ,  121  will contact the strap elements  112 ,  114  as well as the strap elements  111 ,  113 . 
     Since the pads  120 ,  121  are resilient, e.g. because they are made of rubber, they will deform under pressure of the strap elements when the boss  1  moves upwardly relative to the cup. They will thus impart a resilience to the mount structure. They enable the effective resistance to movements by the strap elements to be adjusted to an appropriate value. The stiffness of the strap depends on the material to which it is made, and thus the arrangement of FIG. 18 enables the use of a substantially inelastic material (e.g. Kevlar or similar material) to be used and yet to have some resilience in the effect caused by the strap on the mounting device.