Abstract:
A hand-held massager capable of self-excited, impedance-matched vibration for optimal massaging of each particular body part of each particular individual. The massager includes a hollow, open-ended contact piece to which is coupled a vibrator and which is to be held against a desired body part. A pressure sensor is mounted to the contact piece for sensing pressure variations in the cavity in the contact piece while the open end thereof is held against the body part, in order to ascertain the mechanical impedance of that body part. A closed-loop, electropneumatic vibration control system makes it possible for the mechanical impedance to be fed back to the vibrator, causing the latter to make self-induced vibration. Thus the desired body part is optimally massaged at its resonance frequency.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to massagers in general and, in particular, to those of self-excited vibration variety. More particularly, the invention pertains to a hand-held massager featuring a closed-loop electropneumatic vibration control system for positive feedback of the mechanical impedance of the object of massaging (usually, some body part) to a vibrator. This vibrator is therefore self-excited to vibrate at a resonance frequency of the object and hence to massage the same at the frequency optimal to that particular object.  
         [0002]     Vibrating massagers, having a mechanically vibrating part or parts to be held against desired body parts, are well-known. In designing a massager, one can ascertain the resonance frequency of the mechanical impedance of a particular body part, and massage the object at that frequency. See Japanese Unexamined Patent Publication No. 58-138455, which discusses attaching both acceleration and pressure sensors to the part that is to be held against the body. The mechanical impedance of the desired body part is obtained by sweeping the frequency of vibration, and the vibrator is driven at the resonance frequency of the mechanical impedance that has been computed and memorized after the measurement.  
         [0003]     In Japanese Unexamined Patent Publication No. 2001-252325, a sensor rather than a vibrator is held against the desired object for impedance measurement. The mechanical impedance of the object is positively fed back from the sensor to the vibrator thereby causing the latter to vibrate at the desired resonance frequency.  
         [0004]     Japanese Unexamined Patent Publication No. 6-327639 discusses how to measure the elasticity or like parameter of a human skin surface using a hollow vibrator.  
         [0005]     The first cited patent application, teaching to sweep through an expected range of vibration frequencies for determining the resonance frequency of the desired object seems undesirable because the resonance frequency is susceptible to substantive variation depending upon how the vibrator contacts the body surface. The one being massaged is thoroughly restrained during measurement, and not allowed to move. In event he or she does move, moreover, the resonance frequency must be recalibrated.  
         [0006]     An additional objection arises from the necessity of mounting the sensors in close proximity of that part of the massager which makes direct contact with the human body. Being most exposed and most often held against the human body, this part is most susceptible to impairment or damage, both physically and chemically. The sensors positioned close to such a vulnerable part are easy to suffer impairment or total destruction, demanding much time and cost for upkeep.  
         [0007]     In Japanese Unexamined Patent Publication No. 2001-252325, in which the resonance frequency is automatically renewed by positive feedback, the sensor is not united with the massager. However, one must fasten the sensor to the desired body part either with heavy-duty double-sided adhesive tape or with a belt. Use of such tape or belt is not only troublesome and time-consuming but may cause skin irritation. Certain limitations are imposed, moreover, upon the posture of the user. Furthermore, the sensor carries live current, and therefore poses an additional risk to the user.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention seeks to overcome all such drawbacks and inconveniences of prior devices and provide an improved vibrating massager incorporating a closed-loop vibration control system such that the mechanical impedance of a desired body part is positively fed back to the vibrator thereby causing the latter to vibrate and massage the object at the resonance frequency of that particular object.  
         [0009]     Briefly, the invention may be summarized as a self-excited, impedance-matched vibration massager. It includes a hollow contact piece driven by a vibrator for massaging a desired object by being held against the same. A pressure sensor is mounted to the contact piece, either directly or indirectly, by via a flexible air conduit, for sensing pressure variations in the hollow or cavity in the contact piece while the latter is held against the object, in order to ascertain the mechanical impedance of the object. An electric circuit is connected between the pressure sensor and the vibrator for positively feeding back the mechanical impedance of the object to the vibrator. The vibrator is therefore self-excited into vibration at a resonance frequency of the object, causing the contact piece to massage the object at that frequency.  
         [0010]     Preferably, the contact piece takes the form of a cup with an open end. The pressure sensor may be mounted either internally or externally of the contact piece and, when mounted externally, communicated with the interior of the contact piece via a flexible conduit. There is no need for attaching the pressure sensor to the object or even positioning the sensor close to the object, the sensor being required to sense air pressure inside the contact piece. Even when mounted internally of the contact piece, the pressure sensor may be positioned most spaced from its open end to avoid direct contact with the object and resulting contingencies.  
         [0011]     The user may simply manually hold the contact piece against the desired part of his or her body. The vibrator, which may be of one-piece construction with the contact piece, will then be self-excited into vibration at a resonant frequency of the desired body part.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The foregoing objects, features and advantages of the present invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiments of the invention, in which:  
         [0013]      FIG. 1  is a block diagram of the closed-loop, electropneumatic vibration control system which is set up in use of the massager embodying the present invention;  
         [0014]      FIG. 2  is an axial section through a preferred embodiment of self-excited vibration massager according to the invention;  
         [0015]      FIG. 3  illustrates another preferred embodiment of the massager according to the invention; and  
         [0016]      FIG. 4  is a slightly enlarged, fragmentary axial section through a modification of the massager of  FIG. 1 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The massager according to the invention is built upon the self-excited, positive-feedback, mechanical-impedance-matched vibration control system diagrammed in  FIG. 1 . Indicated at  1  in this diagram is the object of massaging which usually is some part of the human body. A pressure sensor  2  is installed at or adjacent a hollow, open-ended contact piece, not shown in  FIG. 1 , of the massager which is to be held against the object  1 . In practice the pressure sensor  2  may take the form of any such known devices as the omnidirectional microphone, piezoelectric converter, or semiconductor device capable of translating pneumatic pressure variations into an electric signal. Chosen from among any such conventional contrivances, the pressure sensor  2  is herein used to sense variations in the pneumatic pressure of the cavity defined by the contact piece as the latter is held against the object  1 , as will be subsequently detailed with reference to  FIG. 2 .  
         [0018]     The pressure sensor  2  has its output connected through a preamplifier  3  to a low-pass filter (LPF) and automatic grain control (AGC) circuit  4 . As the name implies, the LPF/AGC circuit  4  passes the predefined low-frequency component of the preamplifier output and holds its output signal level constant.  
         [0019]     Connected to the output of the LPF/AGC circuit  4 , an intensity adjustment circuit  5  permits the user to adjust the intensity of vibration. The intensity-adjusted vibration signal is delivered via a power amplifier  6  to a vibrator  7  causing the same to vibrate at the required frequency and desired intensity for massaging the object  1 .  
         [0020]     The vibrator  7  has the electromechanical construction depicted in  FIG. 2 .  
         [0021]     Thus the electropneumatic vibration control system of  FIG. 1  forms a positive feedback loop for self-excited and impedance-matched vibration. Massaged by the vibrator  7 , the object  1  has its vibration detected by the pressure sensor  2 . The output from this pressure sensor  2  is amplified by the preamplifier  3 , then processed as aforesaid by the LPF/AGC circuit  4 , and then directed into the intensity adjustment circuit  5  which adjusts its output level to the preset intensity of vibration to be applied. The output from the intensity adjustment circuit  5  is amplified by the power amplifier  6 , and the output from this amplifier applied to the vibrator  7 .  
         [0022]     The signal indicative of the vibration of the desired part of the user&#39;s body is positively fed back as above to the vibrator  7  for self-induced vibration. The vibrator  7  vibrates with the intensity that has been determined by the intensity adjustment circuit  5  for massaging the object  1 , and with a frequency that is the resonance frequency of the object.  
         [0023]     The resonance frequency depends upon the body part to be massaged. Generally speaking, it is of the order of several hertz for the abdomen (and chest as well in the case of women), ten-odd hertz for limbs, and several tens of hertz for the shoulder. Although the self-excited positive-feedback vibration control system of  FIG. 1  was explained in terms of analog circuits, a person of ordinary skill could digitize at least part of the system, as by connecting the output of the preamplifier to an analog-to-digital converter.  
         [0024]     Reference may be had to  FIG. 2  for an understanding of the electromechanical configuration of the vibrator  7 .  FIG. 2  omits the casing, palm grip and other appendages which are all deemed unnecessary for the understanding of the instant invention.  
         [0025]     A yoke  21  of high permeability magnetic material in the shape of a hollow cylinder, closed at one end and open at the other. The yoke  21  has a pole  22  of the same material mounted coaxially therein with clearance  24 , and against the closed end of the yoke  21  by a permanent magnet  23 . Loosely and concentrically received in the clearance  24  is a hollow coil bobbin  25 , which is supported by the yoke  21  by pliant bobbin carriers  26  for axial displacement or vibratory motion without touching the yoke  21  or pole  22 . The coil  27  wound around the bobbin  25  has leads  28  for electrical connection to the power amplifier  6 , see  FIG. 1 .  
         [0026]     The aforesaid cup-shaped contact piece  29  is mounted to one end of the hollow coil bobbin  25  projecting from within the yoke  21 . The contact piece  29  defines a cavity or hollow  30  which is open to the atmosphere via an open end  29   a  of the contact piece  29  to be held against any desired part of the body. Mounted in the hollow  30  of the contact piece  29 , and in a position perhaps most distanced from the open end  29   a , is the pressure sensor  2  forming a part of the electropneumatic vibration control system shown in  FIG. 1 . The pressure sensor  2  is electrically connected to the preamplifier  3 ,  FIG. 1 , by conductors  32  extending outwardly of the contact piece  29 .  
         [0027]     In use, the user may press the open end  29   a  of the cup-shaped contact piece  29   a  against any desired part of his or her body. Thereupon the skin will bulge out into the cup cavity  30  thereby hermetically closing the same. Pressure variations in the cup cavity  30  can now be translated into an electric signal by the pressure sensor  2 ; that is, the mechanical impedance of the body part in question is now detectable. The positive-feedback vibration control system of  FIG. 1  will operate to cause the desired body part to be massaged at the maximum displacement frequency of the skin part confined in the cup cavity  30 .  
         [0028]     There may be prepared a set of cup-shaped contact pieces of different sizes, particularly of the cavity ends  29   a  of different diameters. A contact piece with a cavity end as small as 15 millimeters in diameter, for instance, will make the resonance frequency of the confined skin area very high. The open end of the contact piece will make maximum displacement with a low resonance frequency of 20 hertz or so. Such a contact piece will suit the massaging of relatively large areas such as the thighs or abdomen.  
         [0029]     Another example of contact piece, with a cavity end as great as 50 millimeters, will cause vibration with a frequency of several tens of hertz, such that the body part bulging into the cup cavity will undergo a maximum change in radius of curvature. Such a contact piece will be good for massaging relatively small areas such as those of the face. It can, moreover, treat such parts purely pneumatically.  
         [0030]      FIG. 3  is an illustration of another preferred form of vibrator  7 ′ which differs from its  FIG. 2  counterpart in having a tubular contact piece  29 ′ coaxially mounted to the yoke  21  in end-to-end abutment. The other end  29   a ′ of the contact piece  29 ′ is open. Whereas the contact piece  29 ′ is thus itself restrained from displacement relative to the yoke  21 , the coil bobbin  25  is free to travel relative to the yoke and the contact piece. Partly received with clearance in the contact piece  29 ′, the coil bobbin  25  is hermetically closed at one end by a diaphragm  33 . The pliant bobbin carriers  26  are also of airtight construction in this embodiment in order to discommunicate the contact piece cavity  30 ′ from the interior of the yoke  21 . All the other details of construction are as previously set forth with reference to  FIG. 2 .  
         [0031]     The cavity  30 ′ of the contact piece  29 ′ will be hermetically closed as its open end  29   a ′ is pressed against the skin of the desired body part. Then, as the vibration control system of  FIG. 1  is set into operation, the diaphragm  33  on the coil bobbin  25  will vibrate to create variations in the air pressure in the contact piece cavity  30 ′. Such pressure variations will be uniformly applied only to that part of the skin which is confined in the contact piece cavity  30 ′. The mechanical impedance obtained in this case is therefore representative of only the skin part confined in the contact piece cavity  30 ′, so that this embodiment is best adapted for massaging localized parts of the body.  
         [0032]     The massagers built according to the present invention may also be used to massage parts of the body through the clothes in order to avoid baring the user&#39;s skin in public. Cavities  30  and  30 ′ of the contact pieces  29  and  29 ′ in  FIGS. 2 and 3  would not be hermetically closed should their open ends  29   a  and  29   a ′ be held against a part of the body covered with clothing. The mechanical impedance of the desired body part might not be correctly ascertained then.  
         [0033]     A remedy to this problem is to close the open ends  29   a  or  29   a ′ of the contact pieces  29  and  29 ′ with an airtight, or semi-airtight, cap or film or sheet. The mechanical impedance obtained in this case, however, will be not only of the desired body part but of the combination of the body part, the clothes and the cap or the like. Use of thin, pliant and lightweight caps or the like is therefore recommended in order to minimize their effect upon measurement of the mechanical impedance.  
         [0034]      FIG. 4  shows an alternative method of mounting the pressure sensor  2  to the contact piece  29  which is shown in  FIG. 2 . As shown in  FIG. 4 , the pressure sensor  2  is installed externally of the contact piece  29 . This contact piece has projecting therefrom a short tube  34  in open communication with the cavity  30 ′. A flexible conduit  35  is airtightly coupled at one end to the tube  34  and has the pressure sensor  2  airtightly attached to the other end thereof. The pressure sensor  2  is electrically connected to the preamplifier  3 . See  FIG. 1 , by the conductors  32  as in the foregoing embodiments.  
         [0035]     Thus, mounted outside the contact piece  29  and communicated with its interior via the flexible conduit  35 , the pressure sensor  2  is totally free from the mechanical vibration of the contact piece. It can nevertheless remotely sense the internal pressure variations of the contact piece.  
         [0036]     Although the present invention has been hereinbefore described in terms of some exemplary embodiments thereof, the invention permits a variety of modifications on the basis of this disclosure. For example, the contact piece may be modified into elongated, tapered or other shapes to adapt itself to the body parts of various positions and shapes to be massaged. Also, an assortment of contact pieces, or contact piece tips, of different shapes and sizes may be prepared for interchangeable use, thereby adapting a single vibrator for use on body parts of widely different surface areas, positions and contours.  
         [0037]     It is recognized, moreover, that the massager of this invention lends itself to uses other than massaging. Such additional or ancillary uses include the detection of the resonance frequencies and viscosity resistances of objects such as sponge, rubber and meat products, which all have surfaces just as smooth, pliant and flexible as the human skin. Important parameters of these products, the resonance frequencies and viscosity resistances are measurable by holding the vibrator against their surfaces.  
         [0038]     Therefore, it should be understood that various modifications may be made without departing from the spirit of the invention, and that its scope be determined by the following claims.