Abstract:
An apparatus having in a mutually rotatable configuration, a first fluid shear member connectable to a first moveable body part of a handheld device and a second fluid shear member connectable to a second moveable body part of the handheld device. The first and second fluid shear members are configured to experience mutual rotation when the first and second moveable body parts are connected respectively to the first and second fluid shear members and when the moveable body parts are moved in relation to one another. The first and second fluid shear members are matched and there is fluid between the first and second fluid shear members so as to invoke viscous dampening when the first and second fluid shear members rotate in relation to one another.

Description:
TECHNICAL FIELD 
   The present invention generally relates to handheld apparatus. The invention relates in particular, though not exclusively, to a portable apparatus with moveable parts and a motion dampener configured to absorb kinetic energy when moving the moveable parts in relation to each other. 
   BACKGROUND 
   Various portable devices are provided with two or more parts that are moveable in relation to each other. Depending on the size of the device, the length of a movement and the mass of moving parts, substantial strain may be applied to the mechanism that keeps the parts movably together. There are various technical solutions such as using snug fitting or friction hinging hinged parts, moving a clamp along an axle, rotating a fan with a geared-up speed and squeezing viscous or hydraulic fluid through tight gaps so as to absorb kinetic energy into heat that is dissipated out of the device. However, portable devices such as clam shell formed mobile telephones present a particularly difficult environment in which the known techniques suffer from a number of drawbacks. The dampening mechanisms in such devices are typically inadequately dampening, noisy, fragile, heavy, bulky, complex i.e. difficult to manufacture and prone to malfunction. Hence, reasonably small mechanisms tend to be either expensive or to have too short a life time to endure the harsh operating environment. Namely, mobile phones are often exposed to dropping on a floor in cold and hot environments, squeezing in pocket, use as stress toys and so on. While the manufacturers of mobile phones can guide how to properly use mobile phones and protect them from damage by careful operation and storage, the users often take shortcuts or simply do not bother to avoid malfunction. Yet, when problems arise, the manufacturers are usually asked to repair any faults on their account. 
   SUMMARY 
   According to a first example aspect of the invention there is provided an apparatus comprising:
         in a mutually rotatable configuration, a first fluid shear member connectable to a first moveable body part of a handheld device and a second fluid shear member connectable to a second moveable body part of the handheld device, the first and second fluid shear members being configured to experience mutual rotation when the first and second moveable body parts are connected respectively to the first and second fluid shear members and when the moveable body parts are moved in relation to one another;   the first and second fluid shear members being matched; and   fluid between the first and second fluid shear members.       

   The first and second fluid shear members may be matched so that they have keyed forms. 
   The first fluid shear member may comprise a first cylindrical element. 
   The second fluid shear member may comprise a second cylindrical element. 
   The first fluid shear member may further comprise a third cylindrical element coaxially with and inside the first cylindrical element. The third cylindrical element may comprise protruding parts that extend over a first length in the radial direction and over a second length in the axial direction. 
   The first and third cylindrical elements may be configured to sandwich the second cylindrical element. 
   The first fluid shear member may comprise a first end in the axial direction and an opposite end. The opposite end may be open to receive the second cylindrical element between the first and third cylindrical elements. The first end may be configured to fix the first and third cylindrical elements together. 
   The third cylindrical element may define a first axial passage for receiving an axle. The first axial passage may be configured to lock the axle to the third cylindrical element such that the rotation of the axle causes the third cylindrical element to rotate to a particular extent. The particular extent may refer to substantially identical angular motion. Alternatively, the particular extent may refer to a particular angular range. 
   The second fluid shear member may define a second axial passage to receive and pass through the axle. 
   The second fluid shear member may comprise a form locking part and the case may comprise a form locking counterpart configured rotationally lock the second fluid shear member to the case. The second fluid shear member may comprise, in axial direction of the axle, the form locking part and the second cylindrical element as a sequence. 
   The apparatus may further comprise a case configured to surround the first and second fluid shear members. The case may comprise a first end configured to cover the first cylindrical element while allowing the first cylindrical element rotate within the case. The case may be configured to form at the first end an inner surface that matches with an external surface of the first cylindrical element over a contact length in the axial direction. The contact length may correspond to the second length. 
   The first and second fluid shear members may provide three different mutually contacting cylinder surface interfaces configured to form shear force in the fluid. Moreover, the axle may also form with the second passage a fourth cylinder surface interface configured to form shear force in the fluid. 
   The apparatus may further comprise a follower configured to close the casing in an end opposite to the first end. The follower may be configured to lock to the axle such that rotational movement of the follower causes rotational movement of the axle to a given extent. The given extent may refer to substantially identical angular motion. Alternatively, the given extent may refer to a given angular range. 
   The apparatus may further comprise a spring configured to cause an angular resilient biasing force to resist rotational movement between the first and second fluid shear members. The spring may be connected between the follower and the second fluid shear member. 
   The apparatus may further comprise a biased cam configured to cause a rotational force between the first and second fluid shear members towards at least one predetermined angle between the first and second fluid shear members. 
   The cam may be biased by a resilient member. The resilient member may comprise a compression spring. 
   The apparatus may be a handheld apparatus. The handheld apparatus may comprise the first and second moveable body parts. The first and second moveable body parts may be rotatable in relation to one another. Alternatively, or additionally, the first and second moveable body parts may be moveable in relation to each other along a track that is selected from the following: linear track and curved track. The handheld apparatus may comprise a gear configured to translate mutual motion of the moveable body parts into mutually rotational motion of the first and second fluid shear members. 
   The handheld apparatus may be a mobile telephone. 
   According to a second exemplary aspect there is provided method comprising:
         receiving force from mutual movement between two mutually moveable body parts of a handheld device and correspondingly causing mutual rotational movement between a first fluid shear member and a second fluid shear member;   shearing viscous fluid between the first fluid shear member and the second fluid shear member in a plurality of coaxial layers, the layers being axially overlapping.       

   According to a third exemplary aspect there is provided an apparatus comprising:
         in a mutually rotatable configuration, first fluid shear means connectable to first moveable body part means of a handheld device and second fluid shear means connectable to second moveable body part means of a handheld device, the first and second fluid shear means being configured to experience mutual rotation when the first and second moveable body part means are connected respectively to the first and second fluid shear means and when the moveable body part means are moved in relation to one another;   the first and second fluid shear means being matched; and   fluid means between the first and second fluid shear means.       

   Different non-binding exemplary aspects and embodiments of the present invention have been illustrated in the foregoing. Some embodiments may be presented only with reference to certain exemplary aspects of the invention. It should be appreciated that corresponding embodiments may apply to other exemplary aspects as well. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  presents three-dimensional illustration of a dampening device of an example embodiment of the invention; 
       FIG. 2  presents another three-dimensional illustration of the dampening device of  FIG. 1 ; 
       FIG. 3  presents a three dimensional assembly illustration of a dampening device according to an example embodiment of the invention; 
       FIG. 4  presents a three dimensional assembly illustration of a dampening device according to another embodiment of the invention; 
       FIG. 5  presents a cross-section of a detail of a dampening device of  FIGS. 3 and 4 , when assembled; 
       FIG. 6  presents a schematic drawing of a hand-held device according to an embodiment of the invention, seen as a section from a side; 
       FIG. 7  presents a schematic drawing of one body part of the hand-held device of  FIG. 6 , seen from top; and 
       FIG. 8  presents a flow chart of a method according to an example embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   In the following description, like numbers denote like elements. 
     FIGS. 1 and 2  present three-dimensional illustrations of a dampening device  100  of an example embodiment of the invention. The dampening device may be constructed as a compact unit with main dimensions of just 5.5×20 mm in one embodiment. However, it is appreciated that the dimensions may be adapted according to particular construction and intended use of the dampening device. The dampening device  100  may be particularly suitable for use in handheld devices such as mobile phones, especially like Nokia® N97 to dampen movement of moveable body parts so as to avoid inadvertent dropping of the handheld device. 
   The dampening device  100  comprises the following externally visible parts:
         a case  100  with a fixing section  112  and with a cylinder section  114 ;   a shaft  120  that extends through the dampening device  100 ;   a follower  130  with an attaching part  132  (such as a form-locking shape; screwing plate; rivet attachment plate; gluing plate; or magnet).       

   It may help to understand the following description to presume that any space between adjacent cylindrical surfaces is filled with viscous dampening fluid such as grease so as to form a viscous force to absorb kinetic energy. The dampening fluid may be, for instance, special damping grease such as those provided by damping greases manufactured by Shin-etsu Chemical Industries, Ltd. of Japan. 
     FIG. 3  presents a three dimensional assembly illustration of a dampening device according to an example embodiment of the invention.  FIG. 3  particularly illustrates interrelations of different parts of the dampening device  100 . The shaft  120  has an endplate  121  and following the endplate, in succession a round sealing ring section  122  for receiving a sealing ring  310 , a first rotation-inhibition section  123 , a round axle section  124 , a second rotation-inhibition section  125  and a head  126 .  FIG. 3  further shows the sealing ring  310  (e.g. a washer), the case  110  with the cylinder section  114  adjacent to the sealing ring  310 , a first fluid shear member  320 , a second fluid shear member  330 , a torsion spring  340  and the follower  130 . 
   The first and second fluid shear members  320  and  330  comprise a set of sandwiching cylinder sections which when assembled form a number of adhering pairs of surfaces out of which one is configured to be locked to the case and the other is configured to rotate along with the shaft  120 . 
   The first fluid shear member  320  may enter into the cylinder section  114  of the case and lock with the shaft by the first rotation-inhibition section  123 . In  FIG. 3 , the first rotation-inhibition section has a square profile and the first fluid shear member  320  has correspondingly channel  324 . Thus, the first fluid shear member  320  is configured to rotate along with the shaft  120 . The first fluid shear member has an outer surface  322  that is configured to adhere to the inner surface of the cylinder section  114  of the case  110 . 
   Alternatively, the first rotation-inhibition section  123  may be configured to wedge with the channel  324  so as to inhibit or prevent undesired rotation of the shaft with relation to the channel  324 . 
   The second fluid shear member  330  may comprise a cylinder  332  configured to enter into the first fluid shear member such that two closely adhering pairs of surfaces are formed with the first fluid shear member  320 . The second fluid shear member further comprises a lock part  334  that is formed to form lock with the fixing section  112  of the case  110 . The lock part  334  and the cylinder  332  together define an axel hole  338  for the axel section  124  coaxially with the first fluid shear member  320  and with the cylinder section  114 . The lock part may further comprise a lock for the torsion spring  340  in order to support the torsion spring  340  to the case  110 . Alternatively, the torsion spring  340  itself may be configured to abut to a suitably shaped part of the fixing section  112 . 
   Next, there is drawn a helical spring as the torsion spring  340 . It is appreciated, however, that the torsion spring may alternatively or additionally comprise a rotatable piece of flexible hose, of flexible grid, or any other type of resilient element suited to create a torsion bias. The torsion spring  340  is also an optional element that may be useful to allow automated motion in one direction (e.g. stiletto type opening of a clam shell type phone). 
   The follower  130  also defines a passage  134  for the shaft  120 . The passage is formed to inhibit rotation of the second rotation-inhibition section of the shaft  120  from rotating within the passage  134 . In  FIG. 3 , the second rotation-inhibition section is also of square profile. The aperture  134  may be of corresponding shape or made to conform to such a shape such that in normal use, the shaft  120  does not slip rotationally with relation to the passage. 
   The head  316  of the shaft is axially locked to the follower  130  when the dampening device  100  is assembled. This may be done in many ways, for instance by expanding the head e.g. by riveting as is shown in the head  316  of  FIG. 3 . It is appreciated that before assembly, the head  316  should pass through the apertures dimensioned for the following sections of the shaft  310 . In one example, the shaft  310  is hollow at least at the end  316  such that after assembly, the end of the shaft is expanded in well-known techniques to prevent the assembly from opening unintentionally. It may also be useful to close the assembly so that it is not easy to dissemble, at least without leaving trace, because the operation of the dampening device may largely depend on the quality of the fluid inside the dampening device. 
     FIG. 4  presents a three dimensional assembly illustration of a dampening device according to another embodiment of the invention. In comparison to  FIG. 3 ,  FIG. 4  differs mainly in that  FIG. 4  further shows a compression spring  440 , an upper cam  430  rotationally locked to a shaft  410  and a lower cam  422  attached to the second fluid shear member, here denoted with reference sign  420 . Also the shaft has a shorter axle section  414  than that ( 314 ) in  FIG. 3  and a longer second rotation-inhibition section  415  than that ( 315 ) in  FIG. 3 , but otherwise the structures are similar. 
   The cam structure of  FIG. 4  may provide a desired snap-effect. It is understood that the cam may comprise only one noose and desired number of recesses at predetermined angular positions to attract the shaft to assume corresponding angular positions. The cam may also be used to keep movable body parts closed together for transport as well as to keep the movable body parts in desired extended configuration (possibly in one of many alternatives). 
     FIG. 5  presents a cross-section of a detail of the dampening device  100  of  FIGS. 3 and 4 , when assembled.  FIG. 5  shows particularly how the first and second fluid shear members are keyed or matched to closely follow one another so that a number of adjacent, very close pairs of rotating and fixed cylindrical surfaces are formed. When looking into the structure, layer-by-layer, there is the inner surface of the cylinder section  114  against the outer surface of the first fluid shear element, then the inner surface of that same cylindrical part against outer surface of the second fluid shear member and so forth. 
     FIG. 5  also clearly illustrates that viscous fluid is exposed to shear forces over a significant surface area (between each cylindrical surface pair and between the innermost cylinder surface and round axel section). Hence, the dampening device may provide relatively high extent of dampening in comparison to the size and weight of the dampening device. 
     FIG. 5  also presents that there may be minute spaces left on the bottom of the cylinder section in order to reserve some extra fluid. In some embodiments, the cylindrical elements may be produced so that their thickness varies angularly such that the inducing viscous dampening varies as a function of the angular relationship between the first and second dampening members. Moreover, there are various other ways to adapt the structure to particular needs with differing design of the fluid shear members&#39; geometry, not to mention other parameters. For instance, instead of continuous cylindrical surfaces, there may be a set of teeth in one fluid shear member positioned to pass very near teeth or cylindrical surfaces of another fluid shear member; cylinders may have voids in the walls; there may be radial, axial or helical borings to increase the amount of viscous fluid that is exposed to shear. 
     FIG. 6  presents a schematic drawing of a hand-held device  600  according to an embodiment of the invention, seen as a section from a side. The hand-held device may be, for instance, a mobile phone, navigator, game device, personal digital assistant, electronic book. The hand-held device  600  comprises a first body part  610 , a second body part  620 , a hinge system  630  configured to rotatably connect the first and second body parts together, a microphone  640 , a set of keys  650 , a display  660  and a speaker  670 . 
     FIG. 7  presents a schematic drawing of the first body part of the hand-held device of  FIG. 6 , seen from top.  FIG. 7  particularly demonstrates an example of the hinge structure with two hinges and the dampening device  100  in connection with one of the hinges.  FIG. 7  shows hinge axels  730  rotatably connecting hinge parts  710  and  720  of the first and second body part, respectively. The second hinge part  720  has also a matching recess for receiving the attaching part  132  of the follower  130  of the dampening device  100 . 
   It is appreciated that it is also possible to construe the hinge structure such that a single hinge is surrounded by two dampening devices  100  or that a number of hinges may be provided with a dampening device. Moreover, the dampening device and the hinge may be further integrated e.g. such that a common axel provides the hinge axle and acts as a part of the shaft of the dampening device. 
     FIG. 8  presents a flow chart of a method according to an example embodiment of the invention for assembling a dampening device  100 ′. It is appreciated that the process represents but one working solution, while others do also exist. 
   The assembly process comprises the following steps: 
     810 . Add a washer into the shaft. 
     820 . Add the shaft into the case. 
     830 . Add lower damper or first fluid shear member (with damping grease) into the shaft 
     840 . Add upper damper or the second fluid shear member into the shaft. Side caulk the upper damper with the case to make the upper damper stationary 
     850 . Add upper cam into the shaft 
     860 . Add compression spring into the shaft 
     870 . Add torsion spring into the shaft and upper damper 
     880 . Add follower into the shaft and torsion spring. Rivet the shaft head that follower is permanently connected to the shaft 
   It is appreciated that the side caulking of the upper damper with the case may be very cost efficient in mass production, but it is also possible to form the upper damper such that it will not penetrate too deep into the case. 
   The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments of the invention a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented above, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention. 
   Furthermore, some of the features of the above-disclosed embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the scope and spirit of the appended patent claims.