Abstract:
An ergonomic lightweight hand pressure sensor-warning device for use with hand held objects like sport devices, steering devices, writing devices or computer devices, as well as the method for its assembly. This new hand pressure sensor warning device is designed as a relatively thin plaster/band-aid to attach the device onto the outside surface of the handgrips of hand held devices like a golf club, making the attachment to and detachment from the hand held device very simple and user-friendly. The device contains an electrical membrane switch, an electrical indicator with an alarm device and a streamlined oblong housing element which contains the principal components in a compact unit. Due to its low manufacturing costs, the warning device is also highly attractive as a commercial advertising product and as a corporate gift or premium product. The unintended and unexpected detachment of the device during a golf swing is practically impossible.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This patent application claims priority from Netherlands Application No. 1021045 filed Jul. 10, 2002, Netherlands Application No. 1022654 filed Feb. 12, 2003, and PCT Application No. EP20/03007481 filed Jul. 10, 2003. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an ergonomic lightweight hand pressure sensor-warning device, for use with handheld objects like sport devices, steering devices, writing devices or computer devices, as well as the method for its assembly. 
   The invention also relates to an assembly method of a hand pressure sensor warning device. The invention also relates to a membrane switch for use in a hand pressure sensor warning device. 
   2. Background Art 
   The warning device is used to correct handgrip forces applied to handgrips of handheld objects or equipment, in particular for use with sports devices including but not limited to tennis, squash, badminton, table tennis, baseball, cricket, hockey, fencing, billiards, pool, shooting sports, rowing, skiing, etc. and also for use by drivers of vehicles, boats and ships, for use by machine operators, medical personnel and other applications to correct grip pressure exerted on the handheld object or equipment and to improve performance or to prevent muscle stress or the risk of injury. The invention can also be used to correct hand- and finger forces on handheld writing tools, such as pens and pencils during writing or on hand operated computer interface devices such as a computer mouse. The ergonomic lightweight hand pressure sensor warning device also serves to correct hand pressure forces on the steering wheel of a vehicle or helm of a vessel or the control handle of aircraft, helicopters, and other industrial machines. 
   To perform a correct hit or hand movement, for example, with tennis, squash, badminton, table tennis, baseball, softball, cricket, hockey, fencing, billiard, shooting sports, rowing, in which different equipment is held in one or both hands, is difficult to learn, especially when precision and grip strength is important for the level of performance. Inadequate grip strength or too much grip strength deteriorates performance and can result in injuries, caused by incorrect handgrip or handgrip forces. In certain cases, excessive handgrip forces can cause muscle or joint injuries in the fingers, hands, wrist, elbows, arms, shoulders and back. 
   Known devices are described in U.S. Pat. No. 5,377,541 and WO 95/311258, which in the golf world are known as the “Smartgrip”. Both devices are mainly constructed from sensor elements with accompanying electronics, power supply and sound device, all attached to the handgrip of a golf club by means of a spirally wrapped band with “C” clips (or internally attached) according to U.S. Pat. No. 5,377,541 or by means of a cylindrical flexible hose according to WO 95/311258. 
   Another known device according to WO 99/27853 encloses a capacitive sensor constructed from different pressure sensitive conductive plates with isolating layers in between and integrated in a handgrip area of a racquet, bat, club or other equipment. Simple installation on a racquet, bat, club or other equipment by an end-user is not possible. Further this very sensitive hardware can not be removed for repair or maintenance without the help of an expert. The capacitive pressure sensors are very sensitive to temperature changes and moisture. This prevents a long-life guarantee. Such capacitive sensors with an adequate power supply and miscellaneous electronic components are rather expensive, which results in substantially higher production costs for a racquet, bat or other equipment using such technology. 
   Another disadvantage of this and of all other known warning devices is the large physical mass required. This substantially influences the appropriate moment of inertia of the golf club, racquet, bat or other equipment. Hits and movements learned with such a warning device need to be learned again without the use of these training aids, or with conventional racquets, bats and other equipment. Due to the high cost price, these types of warning device are not suitable for premium and or promotional give-away products. The known warning devices are too big, too heavy, too complicated and too expensive to be used with small handheld devices like pens or computer mouse&#39;s. 
   SUMMARY OF THE INVENTION 
   By using the present invention, the abovementioned drawbacks are eliminated and new features are added. 
   The hand pressure sensor-warning device according to the invention comprises the following elements:
     1. An electrical membrane switch comprising a first and a second membrane layer, each membrane layer having contact areas comprising electric conducting material with the membrane switch being electrically interconnected to the electrical indicator;   2. An electrical indicator mainly containing a circuit board provided with power supply, the indicator being electrically interconnected to the integrated alarm signal device;   3. An integrated alarm signal device for generating an alarm signal, like an audio or light signal or a vibrating or buzzing signal;   4. A housing element covering the primary components, 1.1-to-1.3 in a compact unit; a part of the housing element being closely in contact with the membrane switch,
 
whereby the alarm signal device generates an alarm signal when the membrane switch is closed by hand or finger pressure practiced on that part of the housing element which is in contact with the membrane switch.
   

   This new hand pressure sensor warning device is designed as a relatively thin band-aid or sticking plaster to attach the warning device onto the outside surface of the handgrips of handheld devices, making the attachment to and detachment from the handheld device very simple and user-friendly. Secondly, the minimal dimensions and mass of the new device have a negligible influence on the appropriate moment of inertia of the hand held device. The unintended coming loose of the warning device from a handheld object during its use is not possible while the hand or finger presses the warning device against the object. Due to its low manufacturing costs, the warning device is also highly attractive as a commercial advertising product and as a corporate gift or premium product. 
   The related dimensions and masses of said elements are small, and two thin flat membrane layers correspond in dimensions with the grip area of the hand or fingers on the handgrip of the hand held devices like sport devices, steering devices, writing devices or computer devices. 
   The device is designed such that the exercise of pressure from the user&#39;s hands and/or fingers on the grips of the racquet, bat, club, stick, bow, ski, cue, rifle, pistol, wheel, handle, equipment control, knobs, pen, knife, computer mouse etc. is optimally transferred to the ergonomic lightweight hand pressure sensor-warning device, whereby, in order to indicate the correct application of single or double hand- and/or finger pressure, the membrane switch is calibrated on a hand pressure upper threshold and/or hand pressure lower threshold, or both, such that when the hand pressure upper threshold is reached or exceeded by the application of excessive hand pressure, the user is audibly, visually or physically warned; which hand pressure sensor-warning device can be attached to and detached from the equipment in use without disturbing its functionality. The extreme low mass of the hand pressure sensor-warning device is realized by using flexible electronic print foils or membrane layers and specially designed and placed membrane switches assembled from membrane layers as explained below. 
   The dimensions of the indicator, preferably attached on the first membrane layer, comprising the circuit board with power supply and also to the indicator attached integrated alarm device, allows placement of the thumbs of a user player during the use of the sports etc. device with the warning device. 
   The attachment of the warning device to the sport etc. device is preferably done by means of the double sided, adhesive tape, thereby eliminating the use of a band-system with “C” clips or the use of velcron tape. Unwanted coming loose of the warning device from the sports etc. device is very unlikely because the warning device is fully covered at least one hand during it use. 
   Method for assembling a hand pressure sensor warning device comprising the following steps:
     1. placing the housing element up side down in a holder comprising vertical pins by pushing the housing element with the assembly openings over the corresponding pins,   2. attaching the membrane switch with indicator and optional an adhesive layer by means an attachment layer on the housing element and positioning the switch by pushing it over the vertical pins of the holder extending from the housing element,   3. optional attaching an adhesive layer on the membrane switch,   4. removing the assembled hand pressure sensor warning device from the holder by pulling it from the two pins.   

   Another important aspect of the invention is that the first and the second membrane layers of the membrane switch are mutually positioned and fixed at a distance by means of a perforated isolating layer between the two membrane layers. This perforated isolating layer can be a glue layer with regular openings, whereby the openings correspond to the contact areas of at least one membrane layer. In this way a simple, accurate hand pressure switch can be constructed, which can easily be adapted to its desired application by varying the contact areas and/or the perforated glue layer leading to a in this way adjustable threshold hand pressure value of the membrane switch to close. The isolating layer can have a constant thickness, but the thickness can also change e.g. linear over the length of the membrane layer when a difference in pressure sensitivity dependent of the position on the surface of the membrane switch is needed. 
   In this membrane switch according to the invention the first membrane layer preferably comprises two contact areas which areas are electrically interconnected to the indicator thus forming an open electrical circuit while the second membrane layer comprises contact areas which will close the electrical circuit on the first membrane layer when hand or finger pressure is exerted on the membrane switch. 
   Preferably whereby the first contact area of the first membrane layer consists of:
         a first connecting strip extending longitudinally from the electrical indicator to the end edge of the membrane layer, said strip extending closely and being parallel to the first longitudinal edge of the membrane layer and   at least two, with the first connecting strip connected, parallel running side strips which extend widthwise in the direction of the second longitudinal edge perpendicular or at an angle relative to the first connecting strip,
 
whereby the second contact area consists of
   a second connecting strip extending longitudinally from the electrical indicator to the end edge of the membrane layer, said strip extending closely and being parallel to the second longitudinal edge of the membrane layer and of   at least two with the second connecting strip connected parallel running side strips which extend widthwise in the direction of the first longitudinal edge,
 
in such a way that a side strip of the first contact area is always positioned adjacent and running parallel to a side strip of the second area.
       

   In this way a long switch surface can be created with over its total surface a constant or varying pressure threshold value. Thus independent of where on the warning device the grip pressure of the user is exceeded the membrane switch will close and the alarm signal will be given. The contact areas of the second membrane can be parallel strips or can be areas placed inside domes formed in the second membrane layer. 
   To increase the flexibility of the membrane switch the second membrane layer can comprise cuts or grooves extending lengthwise thereby facilitating bending widthwise of the membrane switch perpendicular to its longitudinal axis for easy fit on a sport etc. device with a circular cross-section. 
   Preferably the domes formed in the second membrane layer are provided with cuts for lowering the hand or finger threshold value of the membrane switch. Preferably the electrical indicator is attached to the first membrane layer and connected to the contact areas of the first membrane layer, whereby the integrated alarm device is attached to the electrical indicator and where on top of the second membrane layer the housing element is attached covering the membrane layers of the membrane switch and covering in a bulge the electrical indicator with attached integrated alarm device. The hand pressure warning device can in this way be constructed at low cost and with dimensions which will fit most handgrips of sport etc. devices. 
   All individual components of the device can be mass-manufactured, as well as their assembly, allowing low final product lost. This makes it possible to use the device as a commercial advertising product, corporate gift or premium product. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described according to the drawings: 
       FIG. 1  shows a front view of a prior art golf club hand pressure sensor; 
       FIG. 2  shows a front view of another prior art golf club hand pressure sensor; 
       FIG. 3  shows an open, perspective view of a known hand pressure-device according to WO 99/27853; 
       FIG. 4  shows perspective view of the ergonomic lightweight hand pressure sensor-warning device according to the invention (ergonomic lightweight hand pressure sensor-warning device); 
       FIG. 5  shows an open, perspective view of the ergonomic lightweight hand pressure sensor warning device according to the invention; 
       FIG. 6  shows an exploded, perspective view of an alternative embodiment of the hand pressure sensor device according to the invention; 
       FIG. 7  shows a perspective view of the hand pressure sensor device according to the invention, installed on a golf club; 
       FIG. 8  shows an enlarged detail of an alternative embodiment of the membrane switch according to the invention; 
       FIG. 9  shows a cross-sectional view of the membrane switch with the second membrane layer with domes; 
       FIG. 10  shows a detail of an alternative embodiment of the second membrane layer; 
       FIG. 11  shows an enlarged detail of an alternative embodiment of the membrane switch with cuts in the domes of the second membrane layer; 
       FIG. 12  shows a cross-sectional view of the assembling of the hand pressure sensor device by using a holder and a press means; 
       FIG. 13  shows a view of the ergonomic lightweight hand pressure sensor-warning device according to the invention during use; 
       FIG. 14  shows a view of another embodiment of the ergonomic lightweight hand pressure sensor-warning device according to the invention; 
       FIG. 15  shows an open, perspective view of an alternative embodiment of the ergonomic lightweight hand pressure sensor-warning device, as shown in  FIG. 14 ; 
       FIG. 16  shows a view of an alternative embodiment, as shown in  FIG. 14  and  FIG. 15 , of the ergonomic lightweight hand pressure sensor-warning device according to the invention during use; 
       FIG. 17  shows a view of an alternative embodiment of the ergonomic lightweight hand pressure sensor-warning device according to the invention during use; 
       FIG. 18  shows schematically an alternative embodiment of the ergonomic lightweight hand pressure sensor-warning device according to the invention; 
       FIG. 19  shows a perspective view of an alternative embodiment of the ergonomic lightweight hand pressure sensor-warning device according to the invention and; 
       FIG. 20  shows a perspective view of a similar ergonomic lightweight hand pressure sensor-warning device according to the invention as shown in  FIG. 19 . 
       FIG. 21  shows another embodiment of the hand pressure sensor warning device attached to a pencil; 
       FIG. 22  shows another embodiment of the hand pressure warning device attached to a control handle of an industrial machine; 
       FIG. 23  schematically shows another embodiment of the invention as an alarming device together with an assembly holder in its open position; 
       FIG. 24  shows the alarming device of  FIG. 23  in the closed position within the assembly holder; 
       FIG. 25  shows the same alarming device and another design of the assembly holder in its open position; 
       FIG. 26  shows the alarming device of  FIG. 25  in the closed position within the assembly holder; 
       FIG. 27  is a detailed view of the alarming device and the sound hole in the buzzer cover. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows the well known device for golf club handgrip training  1  according to U.S. Pat. No. 5,374,541. It contains a pressure sensor  3 , which uses a spirally shaped band  8 , fixed to the handgrip area of golf club  2 . Pressure sensor  3  is connected by means of an electrical wire  6  with electrical indicator  4 . Electrical indicator  4  is, together with connected alarm device  5  contained into the cylindrical housing element  9 , which is fixed to the golf club  2  by means of “C” clips. 
     FIG. 2  shows the well known device for golf club handgrip training  11  according to WO 95/311258, which consists of oblong pressure sensor strips  10   a ,  10   b  and  10   c , having pressure sensor elements (not shown), being positioned on golf club  2  by means of holder  12 , and under-collar  13 . The indicator (not shown) as well as the electronics (not shown) also are located in holder  12 , and alarm device  14  and on/off switch  15  are located on its topside. Device  11  is fixed to golf club  2  by means of a cylindrical flexible hose  16 , which is being pulled down from the top edge of holder  12  towards under-collar  13 . 
   As shown in  FIG. 3 , a known hand pressure-device according to WO 99/27853 encloses a capacitive sensor  41 , mainly consisting of three pressure-sensitive, conductive plates  44  with two dielectric (isolating) layers  45  between them. At the upper side of said plates  44  and  45  is a protective upper layer  42 , and at the under side a protective under layer  43 . All layers are oblong and need to be integrated in the handgrip of racquets, clubs, bats etc. (not shown). According to the design, as more hand pressure is exercised on layers  42 - 45 , the electrical capacity of layers  44  will change to new values, due to the decreased dielectric (isolation) value of the dielectrical layer  45 . When the new capacity value is lower than a preset threshold, the user will be warned by an audible or visual signal, which is generated by other electronic components of the device (not shown here). 
   The new ergonomic lightweight hand pressure sensor-warning device  17  according to invention is in a compact version, according to  FIG. 4 , mounted to a tennis racquet  47  at the location of the racquets&#39; grip surface  48 . Due to small dimensions of the hand pressure sensor-warning device  17  it is possible to put a hand pressure sensor-warning device  17  on all four sides, in a square cross-section, on the grip surface  48  of tennis racquet  47 . 
   The new hand pressure sensor warning device  17  according to  FIG. 5 , with dimensions approximately 20×140 mm, or ¾″×5⅗″, comprises a membrane switch  18 , being constructed from two flat membrane layers; a first layer  18   a  and a second layer  18   b  on top of the first layer; an electrical indicator  19 , consisting of a circuit board  20  with power supply  21  and an integrated alarm device  22 . An oblong housing element  26  covers all mentioned components into a compact unit, 
   The first membrane layer  18   a  is provided with a first contact area  14   a  and a second contact area  14   b . The first contact area  14   a  consists of interconnected strips  30   a ,  30   b ; second contact area  14   b  consists of interconnected strips  31   a  and  31   b . The contact areas  14   a/b  are manufactured from an electric conducting material like copper, special metal products or carbon-conductive material or a combination thereof. Membrane layers  18   a  and  18   b  are mutually positioned and fixed at parallel distance by means of a perforated isolating layer  25  having openings  29 . This isolating layer  25  can be made of a thin sheet of foil, or it can be formed out of a glue layer. The openings  29  can have all sorts of shapes, but preferably the shape of openings correspond to the shape of the sides strips  30   b  and  31   b  of the contacts areas  14   a  and  14   b  of the first membrane layer  18   a . The second membrane layer  18   b  has V-shaped contact areas  32  in this embodiment, but these areas can have all sorts of regular shapes. The electrical indicator  19  and the on the indicator attached alarm device  22  are attached to the first membrane layer  18   a  and interconnected to the first and second connecting strips  30   a  and  30   b  Both connecting strips  30   a  and  31   a  run parallel to the longitudinal edges  33  and  34  in the direction of the end edge  35  of the first membrane layer  18   a . The connecting strips  30   a  respectively  31   a  both have parallel running side strips  30   b  respectively  31   b  which extend widthwise from a connecting strip  30   a  respectively  30   b  in the direction of the opposite longitudinal edges  34  respectively  33 . The two contact areas  14   a  and  14   b  do not connect on the membrane layer  18   a  thus creating an open electrical circuit. When a finger presses against the housing element  26  first membrane layer  18   b  is pressed against isolating layer  25  and when the finger or hand pressure exceeds the threshold value contact area  32  is pressed through the isolating layer  25  and its openings  29  onto contact areas  14   a  and  14   b  thus closing the electrical circuit and activating the alarm device  22 . 
   According to  FIG. 6 , the membrane switch  18  in an alternative embodiment comprises first membrane layer  18   a , second membrane layer  18   b  and isolating layer  25 . Electrical indicator  19  is attached in the middle of the first membrane layer  18   a . The contact areas  14   a  and  14   b  are situated on both ends of the first membrane layer  18   a . The first connecting strip  30   a  runs parallel to the first longitudinal edge  33 , the second connecting strip  31   a  runs parallel to the second longitudinal edge  34 . The parallel running side strips  30   b  and  31   b  are interrupted at the location where the electrical indicator  19  is attached. 
   Perforated isolating layer  25  is not formed out of one sheet or glue layer. On one side the isolating layer is constructed as a perforated glue-layer  25   a  with a lot of small openings  29 ; on the other side the isolating layer is constructed as a glue-layer  25   b , consisting of parallel or non-parallel glue tracks. In this construction, the pressure sensitivity and the pressure threshold value of the membrane switches  18  are determined by the thickness of the side strips  30   b  and  31   b ; the mutual distance between the side strips  31   b  and  31   b ; the size and shape of the openings  29  of the isolating layer  25  and the mutual distance between the openings  29 ; the thickness and elasticity of the isolating layer  25  and the size and the shape and mutual distance of the contact areas  32  of the second membrane layer. The isolating layer  25  can have a constant thickness and material composition, but the thickness and the material composition can also change e.g. linear over the length or width or both of the membrane layer when a difference in elasticity of the isolating layer and/or in pressure sensitivity of the membrane switch is needed dependent on the position on the surface where the finger or hand pressure is exerted. Hereby, first membrane layer  18   a  has on its underside an adhesive strip (not shown) in order to attach the device to the outside of the grip of a e.g. a sports device as can be seen in  FIG. 7 . Membrane layers  18   a ,  18   b , electrical indicator  19  with power supply (not shown) and integrated alarm device  22  are covered by the oblong and streamlined housing element  26  into a compact unity. The housing element  26  has a bulge  23 , extending outward of a size big enough to receive and cover the indicator  19  and attached alarm device  22 . In this embodiment the housing element  26  is bend widthwise perpendicular to its longitudinal axis as can be seen in  FIG. 6 . to fit easily on a sport etc. device with a circular cross-section as e.g. a rounded handgrip of a golf club as can be seen in  FIG. 7 . 
   According to  FIG. 7 , the new hand pressure sensor-warning device  17  of  FIG. 6  is attached on a golf club. Thumbs  27 ,  28  of the golf player are positioned on that part of the housing element which is in close contact with the thin membrane layers of membrane switch, whereby indicator with power supply (not shown) and integrated sound device (not shown) is located between the thumbs  27 ,  28  in a bulge  23  formed in the housing cover  26 . When the finger pressure on the golf club exceeds the threshold value the membrane switch closes and a alarm signal will be given to the golf player. 
   In another embodiment which can be seen in FIGS.  8 , 9  and  10 , the oblong thin second membrane layer  18   b  of membrane switch  18  is of a different construction with plastic or metal domes  24  in such a manner that the hand pressure sensitivity as well as the hand pressure threshold value, is defined by the number, size and rigidity of said domes. The first membrane layer  18   a  also includes an adhesive strip in order to attach the warning device on the outside of a golf club&#39;s grip. In  FIG. 8  can be seen that the membrane switch  18  comprises a first membrane layer  18   a  with contacting areas  14   a  and  14   b  consisting of connecting strips  30   a ,  30   b ,  31   a ,  31   b , and a second membrane layer  18   b  which is provided with a pattern of domes  24  formed from the membrane layer with on the inside of the domes contact areas  36 . As can be seen in  FIG. 8  the domes  24  are positioned in such a way that parallel running side strips  30   b  and  31   b  can be connected by contact areas  36  when hand or finger pressure is exerted on the domes  24 . The hand pressure sensitivity as well as hand pressure threshold value is defined by the number, size and rigidity of said domes  24 . The side strips  30   b  and  31   b  are separated by openings  57 , creating regular mutual distance between two adjacent side strips. A contact between the conductive adjacent side strips  30   b  and  31   b  is realized when at least one of the domes  24  with its contact area  36  is sufficiently deformed to make a simultaneous contact with the conductive side strips  30   b  and  31   b , by hand pressure forces, exercised by the fingers (not shown here) of a user, driver etc. In  FIG. 9  shows a cross-section of the membrane switch  18  with first membrane layer  18   a  comprising the side strips  30   b  and  31   b  of both contact areas at mutual distance  57 . The isolating layer  25  is positioned between the first  18   a  and the second  18   b  membrane layer and preferably has a perforation pattern corresponding to the dome pattern on the second membrane layer  18   b . The second membrane layer  18   b  has an outward extending dome  24  with contact area  36  on its inner surface. When the dome  24  is deformed by hand or finger pressure the contact area  36  will make a contact between two or more side strips  30   b  and  31   b ; thus closing the electrical circuit so the indicator  19  will generate an alarm signal. 
   In  FIG. 10  an alternative embodiment of second membrane layer  18   a  is shown. The second membrane layer  18   b  is provided with domes  24  comprising conductive contact areas  36  on the inner surfaces. The second membrane layer  18   b  further comprises cuts or grooves  37  which extend longitudinally over the membrane layer  18   b  thereby facilitating bending widthwise of the membrane switch  18  perpendicular to its longitudinal axis for easy fit on a sport device  2  with a circular cross-section, as can be seen in  FIG. 7 . In  FIG. 11  an alternative embodiment of the membrane switch  18  of  FIG. 8  is shown. The domes  24  are provided with cut patterns or other incisions  38  to increase flexibility of the domes  24 , making these domes easier to deform and thus increasing the pressure sensibility and lowering the pressure threshold value. 
   The second membrane layer  18   b  and the domes can have a constant thickness and material composition, but the thickness and the material composition can also change e.g. linear over the length of the membrane layer and/or over the domes when a difference in elasticity of the second membrane layer and of the domes, and/or in pressure sensitivity of the membrane switch, is needed dependent on the position on the surface where the finger or hand pressure is exerted. In  FIG. 12  is shown how the hand pressure sensor warning device is assembled. 
   During assembling of the warning device a holder is used to make the assembling easier and cheaper. The hand pressure sensor warning device is assembled with the aid of a assembly holder  60  provided with pins  62 . The holder  60  has a recess  63  of the same shape as the housing element  26 . First the housing element  26  is placed and positioned in the holder upside down by pushing the housing element with the two assembly openings  65  over the pins  62 . The assembly openings  65  can be seen in second membrane layer  18   b  in  FIG. 10 . The housing element  26  and the first membrane layer  18   a  are also provided with corresponding assembly openings for easy positioning (not shown). Then an attachment layer  61  is added for attachment of the already assembled membrane switch  18  with indicator  19  and adhesive strip  64 . The membrane switch with indicator and adhesive strip is pressed into the housing element with circular cross-section by pushing the assembly openings  65  over the pins  62  of the holder  60  with press means  66 . For easy bending of the membrane switch the second membrane layer  18   b  can be provided with cuts or grooves  37  as shown in  FIG. 10 . The assembled warning device is removed from the holder  60  first by removing the press means  66 , secondly by pulling the assembled warning device from the pins  62 . 
   According to  FIG. 13  the new hand pressure sensor-warning device  17  is mounted to the handgrip part of a tennis racquet  47  and is enclosed by the fingers  51  of hand  50  of a tennis player. When the handgrip forces, exercised by fingers  51  on grip surface  48  of tennis racquet  47  exceed the hand pressure sensor-warning device  17  preset upper threshold, an audible warning is emitted by the electrical indicator  19  enclosed in the bulge  23  formed in the streamlined housing element  26 . 
   An alternative embodiment of the compact ergonomic lightweight hand pressure sensor-warning device  17  is according to  FIG. 14 ,  15 ,  16  mounted to the grip surface  48  of a baseball bat  49 . Since a baseball player has a specific way of gripping the baseball bat, (‘round and round’), the membrane switch  18  of this hand pressure sensor-warning device  17  has two parts. These are a first part  18 ′ and a second part  18 ″ which are interconnected. An electronic indicator  19  is enclosed in a bulge  23  of the streamlined housing element  26 , being located close to the free (lower) ends of the grip surface  48  of baseball bat  49 . 
   In more detail the hand pressure sensor-warning device  17  is, as is shown in  FIG. 15 , constructed from membrane switch  18 , electronic indicator  19  and the streamlined housing element  26 . Membrane switch  18  consists of an first part  18 ′, which consists of a first membrane layer  18   a ′ and a second membrane layer  18   b ′ and in between isolating layer  25 ′, and a second part  18 ″, which consists of a first membrane layer  18   a ″ and a second membrane layer  18   b ″ and in between with isolating layer  25 ″. First and second membrane layers  18   a ′,  18   a ″,  18   b ′,  18   b ″ are provided with contact areas, manufactured from copper, special metal products or carbon-conductive material or a combination thereof. The isolating layers,  25 ′ and  25 ″ respectively, have oblong openings  29 . In this embodiment the first membrane layers  18   a ′ and  18   a ″ are in direct contact with housing element  26  and the second membrane layers  18   b ′ and  18   b ″ are positioned on the inside of the warning device which is attached to the baseball bat  49 . Membrane switch  18  is constructed out of 2 parts, but can also be constructed from one or more parts. 
   According to  FIG. 16  the new hand pressure sensor warning device  17  is mounted to the handgrip area  48  of a baseball bat  49 . During use the warning device is more or less enclosed by fingers  51   a  (not visible) respectively  51   b  from the right hand  50   a  respectively left hand  50   b  of a baseball player. When the handgrip forces, exercised by fingers  51   a  (not visible) from the upper right hand  20   a  and/or the fingers  51   b  from the lower left hand  50   b  (or vice-versa) on the grip surface  48  of a baseball bat  49  exceed the hand pressure sensor warning device  17  preset upper threshold, an alarm signal is generated by the electrical indicator  19  which is enclosed in a bulge  23  formed in the streamlined housing element  26 . 
   Another version of the compact ergonomic lightweight hand pressure sensor-warning device  17  is according to  FIG. 17  mounted on a steering wheel  46  of a vehicle. When the handgrip forces, exercised by fingers  51  on grip surface  48  of a vehicle steering wheel  46 , exceed the hand pressure sensor-warning device  17  preset upper or lower threshold, or zero pressure, an audible or visible alarm signal will be generated by the electrical indicator  19  to warn the vehicle driver. 
   As shown in  FIG. 18 , another embodiment of a hand pressure sensor warning device  106  for use by vehicle operators comprises a rounded membrane switch  116 , a signal processing unit  113  with an integrated calibration unit  115  and an indicator  114 . The relatively thin rounded membrane switch  116  is attached to, or integrated within, the steering wheel  46  and interconnected to the signal processing unit  113  by means of wired connectors (shown as striped lines), through the steering column. The signal processing unit may be located within the dashboard of the vehicle. The adjustment of the right upper hand pressure threshold, depending on, for instance, the height of the driver, is realized by processing unit  113 . The functional principles of such calibration units is well known and is not further elaborated here. When the handgrip forces exercised by the drivers hand or fingers (not shown here) on grip surface  108  of a vehicle steering wheel  46 , exceed a preset upper or lower threshold of the calibration unit  115 , or register zero pressure, an audible or visible alarm will be emitted to the vehicle driver by the electrical indicator  114 . This alarm signal may be a combination of a visual alarm signal by means of a signal lamp or a LED  115  in the dashboard of the vehicle and an audible alarm. 
   According to  FIG. 19 , another embodiment of the new hand pressure sensor-warning device  17  is mounted to hand grip  48  of, for example, a tennis racquet. This hand pressure sensor-warning device  17  consists of 4 membrane switch parts or units  18 ′,  18 ″,  18 ′″, and  18 ″″, and an indicator  19 , with an integrated circuit board  20 , power supply  21  and an alarm signal device  22 . A similar design version of the new hand pressure sensor-warning device  17  is shown in  FIG. 20 , without the specific hand grip (of a tennis racquet etc.). Each membrane switch can be connected to the same indicator, but each membrane switch can also be connected to its own indicator or any combination of switches and indicators can be applied when necessary. 
   Another embodiment of the compact ergonomic lightweight hand pressure sensor-warning device  17  is according to  FIG. 21  attached to a writing pen or pencil  52  with writing tip  53 . When the finger grip forces, exercised by fingers  51  on grip surface of the membrane switch  18 ′ of a writing pen or pencil  52 , exceed the hand pressure sensor warning device  17  preset upper threshold, an audible or visible alarm will be generated by the electrical indicator  19  warning the writer. The electrical indicator is enclosed in the bulge  23  formed in the streamlined housing element  26 , and connected to membrane switch  18 ′ by integrated connector  54 . 
   Another embodiment of the compact ergonomic lightweight hand pressure sensor-warning device  17  is according to  FIG. 22  mounted to a control handle of an industrial machine, a helicopter or an aircraft  55  with grip handle  56 . When the finger grip forces, exercised by fingers  51  on the sensitive membrane switch grip surface  18 ′ attached to the control handle of an industrial machine, a helicopter or an aircraft  55 , exceed the hand pressure sensor warning device  17 ′ preset upper threshold, an audible or visible warning will be generated by the electrical indicator  19  to the vehicle driver. The electrical indicator  19  is enclosed in the bulge  23  formed in the streamlined housing element  26 , and connected to sensitive membrane switch  18 ′. 
   The housing element  26  or a part of it can have a constant thickness and material composition, but the thickness and the material composition can also change e.g. linear or non linear over the length or width or both of the membrane layer when a difference in elasticity or stiffness of a housing element part and/or in pressure sensitivity of the warning device is needed dependent on the position on the surface. The housing element or a part of it can have weak spots for e.g. bending of the warning device on a handheld device created e.g. by grooves or cuts or changes in material thickness or composition. 
   It is noted that the embodiments of the hand pressure sensor warning device regarding described herein in detail for exemplary purposes is of course subject to many different variations in structure. Because many variations may be made within the scope of the inventive warning device, it is to be understood that the details herein are to interpret al illustrative and not in a limiting sense. 
   Another important aspect of the invention is that the alarming device ( 22 ) consists of a standard piezo buzzer component ( 22 ′), in combination with a buzzer cover  22 ″. The piezo buzzer is available in the market in a thin version (0.2 mm), and high output. A disadvantage of these thin piezo buzzers is their great vulnerability. Therefore, mostly thicker (0.6 mm), low output versions of piezo buzzers are used. 
   The outward extending bulge  23 , which could be provided with bulge openings  22 ′″ for increasing the sound output volume, on the oblong housing element  26 , has a size big enough to receive and cover the indicator  19  and attached alarm device  22 , but should be minimalized in dimensions in order to prevent infringement of the user&#39;s natural grip. Consequence is that only extremely small buzzers can be used which produce minimal sound levels. 
   In order to gain enough audible sound from the buzzer, buzzer covers are used to increase sound level from standard buzzers. The buzzer covers create a small ‘loudspeaker’ housing around the piezo buzzer and have physical holes to let soundwaves come outside. These buzzer covers exist in a great variety of existing standard components, made from plastics or metal. Normally, the metal covers produce more output with clearer and higher pitch. 
   To assemble metal buzzer cover  22 ″ to the buzzer  22 , normally an assembly holder ( 70 ) in  FIG. 23  is used to fit and position the metal buzzer cover  22 ″, while buzzer  22 ′ is positioned in the metal buzzer cover  22 ″. 
   Press means ( 72 ) will deform the edges around buzzer  22 ′ into position  29  in  FIG. 24 . After that, press means ( 71 ) in  FIG. 25  will further deform the edges of buzzer cover  22 ′ into position  29 ′ in  FIG. 26 . This method of assembly is only suitable for thick, low output piezo buzzers, since thin, high output buzzers will break during the process. 
   The invention claims to have a safe and consistent method of using the thin, high output, piezo buzzers in combination with a method buzzer cover without breaking the piezo buzzer, to get a higher output in soundvolume and to eliminate steps in the production process. 
   By using the very small and thin buzzers, sound output can be even increased significantly by using the right assembly method to create alarming device  22 . The invention claims that, after deformation to position  29 , no further deformation is added to buzzer cover  22 ′″, therefore having the advantage of less breaking of very vulnerable piezo buzzer  22 ′, higher sound output from alarming device  22 , and less production activities to create the alarming device  22 , from the two main components  22 ′ and  22 ″. Due to less fixture between buzzer cover  22 ″ and buzzer ‘, the resonance of the buzzer  22 ’ can create more soundvolume, therefore resulting in an extremely small, low cost, high output, alarming device  22 . 
   Furthermore, the optimal dimension for the sound hole  22 ″″ in buzzer cover  22 ″, in comparison to the diameter of the buzzer  22 ′ and metal buzzer cover  22 ″ is around 1.5 mm, instead of the larger sound holes normally used in buzzer cover in  FIG. 27 .