Patent Abstract:
A tension-adjusting mechanism for the elongated earpieces of a stethoscope comprises a neckpiece and, for each earpiece, a pivot mechanism portion between the proximal end of the earpiece and the neckpiece, a spring mechanism portion between the proximal end of the earpiece and the neckpiece, and a tension-adjusting mechanism portion between the spring member and the neckpiece. For each earpiece, the pivot mechanism portion defines a pivot axis about which the earpiece pivots, and the spring mechanism portion comprises a resilient blade deforming upon spreading apart of the earpieces. This deformation produces a tension on the earpieces opposing to further spreading apart thereof. The tension-adjusting mechanism portion defines a plurality of interchangeable point of contacts with the resilient blades, which contact points having different positions relative to the neckpiece.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tension-adjustable mechanism for the earpieces of a stethoscope. The present invention also relates to a stethoscope headset comprising this mechanism. 
     2. Brief Description of the Prior Art 
     A tension-adjustable mechanism for the earpieces of a stethoscope has been proposed in the following prior art patent: 
     U.S. Pat. No. 5,561,275 (Savage et al.) Oct. 1, 1996 
     According to this prior art mechanism, the two earpieces comprise respective weakened proximal end portions inserted side by side in a longitudinally movable sleeve. Longitudinal movement of the sleeve on the weakened end portions of the earpieces change the amplitude of the tension on the earpieces when these earpieces are spread apart from each other. 
     Although this prior art tension-adjusting mechanism is efficient, further adjustment capability is often required to meet with the requirements, needs and/or preferences of a wide range of users. 
     Therefore, need exists for a more versatile tension-adjusting mechanism capable of fulfilling the requirements, needs and/or preferences of a wide range of users. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a tension-adjusting mechanism for an elongated stethoscope earpiece having a proximal end. This tension-adjusting mechanism comprises a stethoscope neckpiece, a pivot mechanism portion, a spring mechanism portion, and a tension-adjusting mechanism portion. The pivot mechanism portion is interposed between the proximal end of the earpiece and the neckpiece, and defines a pivot axis about which the earpiece pivots relative to the neckpiece. The spring mechanism portion is interposed between the proximal end of the earpiece and the neckpiece, and comprises a spring member which deforms upon pivoting of the earpiece about the neckpiece in an outward direction. Deformation of the spring member produces a tension on the earpiece opposing to further pivoting of the earpiece in the outward direction. Regarding the tension-adjusting mechanism portion, it is interposed between the spring member and the neckpiece and defines a plurality of interchangeable point of contacts with the spring member. These points of contacts with the spring member have different positions relative to the neckpiece. 
     The above mentioned pivot mechanism portion, spring mechanism portion, and tension-adjusting mechanism portion provide for the level of versatility required to fulfill the requirements, needs and/or preferences of a wide range of users. 
     Preferably, the pivot mechanism portion comprises abutment surfaces restricting, by abutment, free pivotal movement of the earpiece about the neckpiece within given limits. 
     According to other preferred embodiments of the tension-adjusting mechanism: 
     the pivot mechanism portion comprises a pivot pin pivotally mounted on the neckpiece, and a pivot tube pivotally mounted on the pivot pin and connected to the proximal end of the earpiece; 
     the spring member comprises a resilient blade having one end formed with the pivot pin; 
     the pivot tube has an open, axial slot through which the resilient blade extends when the pivot pin is inserted in that pivot tube, the resilient blade has a thickness, and the slot has a width larger than the thickness of the blade to allow limited pivotal movement of the pivot tube about the pivot pin; and 
     the pivot tube has an annular end face provided with a lug, the neckpiece has a pair of abutment surfaces situated on opposite sides of the lug, and the lug abuts on either abutment surface to restrict pivotal movement of the pivot tube about the neckpiece within predetermined limits. 
     The present invention further relates to a headset for electronic stethoscope, comprising first and second elongated stethoscope earpieces each having a proximal end, and the above described tension-adjusting mechanism for each elongated stethoscope earpiece. 
     Preferably, the stethoscope neckpiece is common to both the first and second elongated stethoscope earpieces, the neckpiece comprises a hollow shell formed with openings for the proximal ends of the earpieces, and the hollow shell comprises a front shell portion and a rear shell portion assembled together to form that hollow shell. 
     In accordance with a preferred embodiment: 
     the resilient blade associated to the first earpiece has a first distal end section opposite to the pivot pin; 
     the resilient blade associated to the second earpiece has a second distal end section opposite to the pivot pin; 
     the tension-adjusting mechanism portion associated to both the first and second earpieces comprises a tension-adjusting cam having a geometrical axis, rotatable about this geometrical axis and lockable in either first, second and third angular positions; 
     the tension-adjusting cam comprises an axial member having an outer tubular surface and two first points of contact with the first and second distal end sections, respectively, formed by two points of this outer tubular surface, respectively, when the tension-adjusting cam is locked in the first angular position; 
     the axial member of the tension-adjusting cam comprises, on its outer tubular surface, first and second diametrically opposite, axial and radial fins of intermediate height having respective first and second free axial edge surfaces, and two second points of contact with the first and second distal end sections, respectively, formed by these first and second free axial edge surfaces of the first fin, respectively, when the tension-adjusting cam is locked in the second angular position; 
     the axial member of the tension-adjusting cam comprises, on its outer tubular surface, third and fourth geometically opposite, axial and radial fins of larger height with third and fourth free axial edge surfaces, respectively, and two third points of contact with the first and second distal end sections, respectively, formed by these third and fourth free axial edge surfaces of the second fin, respectively, when the tension-adjusting cam is locked in the third angular position; 
     the neckpiece comprises a hole with peripheral notches, and the tension-adjusting cam comprises lugs engaging the peripheral notches of the hole in the neckpiece to lock the tension-adjusting cam in either the first, second and third angular positions; and 
     the tension-adjusting mechanism associated to both the first and second earpieces comprises a spring element interposed between the neckpiece and the tension-adjusting cam and spring biasing the lugs of this tension-adjusting cam in the notches of the hole in the neckpiece, whereby, to be rotated, the tension-adjusting cam is moved against the spring-biasing force produced by the spring element to disengage the lugs from the notches and is rotated and then released to engage the lugs with other notches. 
     The foregoing and other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of a preferred embodiment thereof, given for the purpose of illustration only with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the appended drawings: 
     FIG. 1 is an exploded view of a headset for electronic stethoscope in accordance with the present invention; 
     FIG. 2 is a first inner elevation view of a rear shell portion of a neckpiece of the headset of FIG. 1, showing a tension-adjusting cam in a first angular position; 
     FIG. 3 is an inner elevation view of a front shell portion of the neckpiece of the headset of FIG. 1; 
     FIG. 4 is a second inner elevation view of the rear shell portion of the neckpiece of the headset of FIG. 1, showing the tension-adjusting cam in a second angular position; and 
     FIG. 5 is a third inner elevation view of the rear shell portion of the neckpiece of the headset of FIG. 1, showing the tension-adjusting cam in a third angular position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of the tension-adjustable mechanism for an elongated stethoscope earpiece and headset for electronic stethoscope according to the present invention will now be described with reference to the appended drawings. Just a word to mention that the present invention equally apply to non electronic stethoscopes. 
     In the appended drawings, the tension-adjustable headset for electronic stethoscope is generally identified by the reference  10 . 
     The headset  10  comprises two earpieces  11   a  and  11   b . Since these two earpieces  11   a  and  11   b  and the associated mechanisms are identical but symmetrical, they will be described concurrently. In the appended figures, the references related to the earpiece  11   a  bear the indicia “a” while the references related to the earpiece  11   b  bear the indicia “b”. 
     The earpiece  11   a , 11   b  is constituted by an elongated, arched member advantageously made of slightly flexible plastic material. 
     The earpiece  11   a , 11   b  comprises a distal cup-shaped end  12   a , 12   b  to receive an earphone assembly  13   a , 13   b . The earphone assembly  13   a , 13   b  comprises a speaker  14   a , 14   b , a speaker housing  15   a , 15   b  and an eartip  16   a , 16   b.    
     The distal cup-shaped end  12   a , 12   b  comprises an inner shouldered rim  17   a , 17   b . In the same manner, the speaker housing  15   a , 15   b  comprises a proximal cup-shaped portion  21   a , 21   b  with an outer shouldered rim  18   a , 18   b . The shouldered rims  17   a , 17   b  and  18   a , 18   b  are configured to mate each other. The speaker housing  15   a , 15   b  finally comprises an axial, distal tube  19   a , 19   b  with a distal, externally protruding rim  20   a , 20   b.    
     To assemble the earphone assembly  13   a , 13   b , the speaker  14   a , 14   b  is first placed in the cup-shaped end  12   a , 12   b  of the earpiece  11   a , 11   b . The shouldered rim  18   a , 18   b  of the speaker housing  15   a , 15   b  is then glued or otherwise secured to the shouldered rim  17   a , 17   b  of the cup-shaped end  12   a , 12   b . The cup-shaped end  12   a , 12   b  and portion  21   a , 21   b  then define a cavity in which the speaker  14   a , 14   b  snugly fits. Finally, the eartip  16   a , 16   b  is placed on the tube  19   a , 19   b . Of course, the eartip  16   a , 16   b  is tubular and has an inner configuration adapted to fit on the tube  19   a , 19   b . Those of ordinary skill in the art will appreciate that the distal, externally protruding rim  20   a , 20   b  will hold the eartip  16   a , 16   b  on the tube  19   a , 19   b.    
     Just a word to mention that the eartip  16   a , 16   b  is made of soft, resilient material such as foam, for ensuring comfort of the user&#39;s ear. 
     The earpiece  11   a , 11   b  has a longitudinal channel  22   a ,  22   b  on the inner face of that earpiece  11   a , 11   b . Also, the shouldered rims  17   a , 17   b  and  18   a , 18   b  are structured to form an opening (see  23   a , 23   b ) through which the channel  22   a , 22   b  communicates with the cavity defined by the cup-shaped end  12   a , 12   b  and portion  21   a , 21   b  when secured to each other. This opening  23   a , 23   b  and the channel  22   a , 22   b  define a passage for electrical wires connected to the speaker  14   a , 14   b  along the earpiece  11   a , 11   b.    
     Pivot Mechanism Portion 
     The proximal end of the earpiece  11   a , 11   b  is provided with an integral, transversally extending pivot tube  24   a , 24   b . Therefore, the earpiece  11   a , 11   b  and the pivot tube  24   a , 24   b  are made of a single piece of plastic material. On a first side, the pivot tube  24   a , 24   b  includes an annular flat face  25   a , 25   b  with a semicircular lug  26   a , 26   b . On the second side, the pivot tube  24   a , 24   b  has also an annular face  27   a , 27   b  from which an open, axial slot  28   a , 28   b  extends. In the preferred embodiment, the position and width of the slot  28   a , 28   b  corresponds to the position and length of the semicircular lug  26   a , 26   b . A relatively thin wall  29   a , 29   b  is left between the inner end of the slot  28   a , 28   b  and the annular face  25   a , 25   b.    
     A spring blade  30   a , 30   b  will now be described. This spring blade  30   a , 30   b  is made of molded and resilient plastic material and has at the proximal end thereof an integral, proximal and transversally extending cylindrical pivot pin  31   a , 31   b . Accordingly, the spring blade  30   a , 30   b  and the pivot pin  31   a , 31   b  are made of a single piece of plastic material. The spring blade  30   a , 30   b  has a constant width but a thickness which gradually thins from the pivot pin  31   a , 31   b  to the distal end of that blade. The blade  30   a , 30   b  further comprises a lateral extension  32   a , 32   b  adjacent to the pivot pin  31   a , 31   b . Finally, the pivot pin  31   a , 31   b  has a semicircular groove  33   a , 33   b.    
     The pivot pin  31   a , 31   b  is inserted in the pivot tube  24   a , 24   b , with the blade  30   a , 30   b  including the lateral extension  32   a , 32   b  extending through the slot  28   a , 28   b . As can be seen in FIG. 2, the width of the blade  30   a , 30   b  and lateral extension  32   a , 32   b  is equal to the length of the slot  28   a , 28   b . Also, the width of the slot  28   a , 28   b  is larger that the thickness of the blade  30   a , 30   b  whereby free pivotal movement of the pivot tube  24   a , 24   b  about the pivot pin  31   a , 31   b  is allowed within predetermined limits. 
     The electrical wires connected the speaker  14   a , 14   b  and running through the channel  22   a , 22   b  leave the channel  22   a , 22   b  at the proximal end of the earpiece  11   a , 11   b  through a first hole  37   a , 37   b  in the pivot tube  24   a , 24   b , the semicircular groove  33   a , 33   b  in the pivot pin  31   a , 31   b,  and a hole  38   a , 38   b  in the pivot tube  24   a , 24   b  to thereby reach the inside of a shell  35 , 36  of a neckpiece  34 , common to the two earpieces  11   a  and  11   b.    
     The headset  10  comprises the stethoscope neckpiece  34  of which the shell  35 , 36  comprises a rear triangular shell portion  35  and a front triangular shell portion  36 . When assembled together, the triangular shell portions  35  and  36  define an opening  39   a , 39   b  at an upper corner thereof and through which the proximal end of the earpiece  11   a , 11   b  and the pivot tube  24   a , 24   b  extend. In the proximity of the opening  39   a , 39   b , the shell portion  36  comprises an inner cylindrical blind hole  40   a , 40   b  to receive a first end of the pivot pin  31   a , 31   b . In the same manner, the shell portion  35  comprises an inner cylindrical blind hole  41   a , 41   b  (FIG. 3) coaxial with blind hole  40   a , 40   b  and receiving the second end of pivot pin  31   a , 31   b.  Accordingly, when shell portion  35  is assembled to shell portion  36 , the pivot pin  31   a , 31   b  is free to pivot in the blind holes  40   a , 40   b  and  41   a , 41   b . Pivotal movement of the pivot pin  31   a , 31   b  in the coaxial blind holes  40   a , 40   b  and  41   a , 41   b  is restricted within a given angle, that is within predetermined limits by the semicircular lug  26   a , 26   b  which abuts on faces  42   a , 42   b  and  43   a , 43   b  situated on opposite sides of the lug  26   a , 26   b.    
     It should be pointed out here that the pivot pin  31   a , 31   b , the pivot tube  24   a , 24   b , and the cylindrical blind holes  40   a , 40   b  and  41   a , 41   b  define a pivot axis about which the earpiece  11   a , 11   b  pivots relative to the neckpiece  34 . 
     Tension-Adjusting Mechanism Portion 
     The shell portion  36  further comprises a lower cylindrical hole  44  defining an inwardly extending cylindrical wall  45  having an inner annular edge formed with three 60° spaced apart pairs of diametrically opposite notches such as  46 . 
     A tension-adjusting cam  47  is disposed in the cylindrical hole  44  and is rotatable about its geometrical axis. Cam  47  comprises a circular flat wall  48  and an outer cylindrical wall  89  inwardly extending from the periphery of the circular flat wall  48  and having an annular edge surface formed with a pair of diametrically opposite and outwardly radially extending lugs  49 . Cam  47  finally comprises a central inner tube  50  coaxial with the cylindrical wall  89  and inwardly extending from the flat wall  48 . 
     When the diametrically opposite lugs  49  are disposed in a first pair of diametrically opposite notches  46  as shown in FIG. 2, the cam is locked in a first angular position. The point of contact with the distal end section of the blade  30   a , 30   b  is therefore a point of the outer tubular surface of the tube  50  when the tension-adjusting cam  47  is locked in the first angular position. This corresponds to the larger extent of spreading apart of the earpieces  11   a  and  11   b  before the blades  30   a , 30   b  deform and produce a spring action on these earpieces  11   a  and  11   b.    
     When the diametrically opposite lugs  49  are disposed in a second pair of diametrically opposite notches  46  as illustrated in FIG. 4, the cam is locked in a second angular position. The blades  30   a  and  30   b  then rest on respective, diametrically opposite, axial and radial fins  51  of intermediate height formed on the outer tubular surface of the tube  50 . The points of contact with the distal end sections of the blade  30   a  and  30   b  are therefore the free axial edge surfaces of the fins  51  when the tension-adjusting cam  47  is locked in the second angular position. This corresponds to an intermediate extent of spreading apart of the earpieces  11   a  and  11   b  before the blades  30   a  and  30   b  deform and produce a spring action on the earpieces  11   a  and  11   b.    
     When the diametrically opposite lugs  49  are disposed in a third pair of diametrically opposite notches  46  as illustrated in FIG. 5, the cam  47  is locked in a third angular position. The blades  30   a  and  30   b  then rest on respective, diametrically opposite, axial and radial fins  52  of larger height formed on the outer tubular surface of the tube  50 . The points of contact with the distal end sections of the blade  30   a  and  30   b  are therefore the free axial edge surfaces of the fins  52  when the tension-adjusting cam  47  is locked in the second angular position. This corresponds to an intermediate extent of spreading apart of the earpieces  11   a  and  11   b  before the blades  30   a  and  30   b  deform and produce a spring action on the earpieces  11   a  and  11   b.    
     The shell portion  36  further comprises pegs  54  to receive a printed circuit board  53 . Of course, the printed circuit board  53  comprises corresponding notches and/or holes such as  55  to receive the pegs  54 . The electric wires from hole  38   a  and  38   b  can be connected to this printed circuit board  53 . 
     The shell portion  35  comprises holes  62  and  63  for receiving push-buttons  64  and  65 , respectively. Push-buttons  62  and  63  operate corresponding switches such as  66  mounted on the printed circuit board. 
     The headset  10  further comprises a T-shaped anchor  56  formed of a transversal section  57  and a vertical tube  58  perpendicular to section  57 . The tube  58  fits in a bottom opening of the shell  35 , 36 . This bottom opening is formed by semi-cylindrical opening portion  60  (FIG. 3) of shell portion  35  and semi-cylindrical opening portion  61  (FIGS. 1 and 4) of shell portion  36 . Regarding the section  57 , it is shaped to fit inside the shell portions  35  and  36  just above the bottom opening  60 , 61 . Finally, wires from the printed circuit board  53  can run toward the exterior through a hole  59  in the transversal section  57  and then through the tube  58 . Just a word to mention that the outer surface of the tube  58  is structured to connect to a biological or other sound sensor (not shown). 
     Referring to FIG. 1, the shell portion  35  comprises four holes  67  for receiving four screws  68 . Referring to FIG. 3, the shell portion  35  comprises four threaded holes  69  in which the four screws  68  are screwed upon assembling the shell portions  35  and  36  together. 
     Finally, the shell portion  35  comprises, as shown in FIG. 3, an inwardly extending tube  70  in which a coil spring  71  is installed. When the shell portions  35  and  36  are assembled together, the tube  70  is inserted in tube  50  through a circular hole  73  in the printed circuit board  53 , whereby the coil spring extends in both tubes  50  and  70  to push and hold (spring bias) the lugs  49  in one pair of notches  46  and therefore the cam  47  in position in the cylindrical hole  44 . To rotate the cam  47  and displace the diametrically opposite lugs  49  from one pair of diametrically opposite notches  46  to the other, one has only to push from the outside the cam  47  until the lugs  49  are withdrawn form the notches  46  and, then, rotate cam  47  clockwise or counterclockwise about its axis until the pair or diametrically opposite lugs  49  can be released to engage the desired pair of diametrically opposite notches  46 . The outside face of the circular flat wall  48  can be grooved along a diameter in the same manner as the head of a screw. A coin can then be used in cooperation with this groove (not shown) to facilitate this operation. 
     To assemble the neckpiece  34 , the following operations are performed: 
     Cam  47  is positioned in cylindrical hole  44  from the inside of the shell half  36  with the pair of diametrically opposite lugs  49  inserted in one of the pair of diametrically opposite notches  46 ; 
     The pivot pin  31   a  is disposed in pivot tube  24   a , with the blade  30   a  and lateral extension  32   a  in the slot  28   a  and with the blade  30   a  lying on the same side of the tube  50  as blind hole  40   a;    
     The corresponding end of pivot pin  31   a  is positioned in blind hole  40   a;    
     The pivot pin  31   b  is disposed in pivot tube  24   b , with the blade  30   b  and lateral extension  32   b  in the slot  28   b  and with the blade  30   a  lying on the same side of tube  50  as blind hole  40   b;    
     The corresponding end of pivot pin  31   b  is positioned in blind hole  40   b;    
     The tube  58  of anchor  56  is placed in semicircular opening portion  61  with one end of the transversal section  57  fitted inside the shell portion  36  above this opening portion  61 ; 
     The notches and/or holes  55  of the printed circuit board  53  are engaged with the pegs  54  of the shell portion  36  to thereby mount this printed circuit board  53  in the shell portion  36 ; 
     The push-buttons  64  and  65  are placed in the holes  62  and  63 , respectively; 
     One end of the spring  71  is placed in the tube  70 ; 
     The shell portion  35  is placed on the shell portion  36  with: 
     The free end of the coil spring  71  and the tube  70  of the shell portion  35  inserted in tube  50  of the cam  47 ; 
     The corresponding end of pivot pin  31   a  positioned in blind hole  41   a;    
     The corresponding end of pivot pin  31   b  positioned in blind hole  41   b;    
     The tube  58  of anchor  56  placed in semicircular opening portion  60 , and the corresponding end of the transversal section  57  fitted inside the shell portion  35  above this opening portion  60 ; 
     The push-buttons  64  and  65  above the switches  66 ; and 
     Finally, the four (4) screws  68  are placed in the four (4) respective holes  67  and, then, screwed in the four (4) respective threaded holes  69 . 
     In operation, restricted free pivotal movement of the pivot tube  24   a  about the pivot pin  31   a , and restricted free pivotal movement of the pivot tube  24   a  about the pivot pin  31   b , restricted pivotal movement of the pivot tube  24   a  about the neckpiece  34  due to the abutment action of the semicircular lug  26   a  and surface  42   a , restricted pivotal movement of the pivot tube  24   b  about the neckpiece  34  due to the abutment action of the semicircular lug  26   b  and surface  42   b  allow the earpieces  11   a  and  11   b  to freely move about the neckpiece  34  about a given, relatively small angle. 
     Spring Mechanism Portion 
     When the diametrically opposite lugs  49  of the cam  47  are disposed in the first pair of diametrically opposite notches  46  as shown in FIG. 2, spreading apart of the earpieces  11   a  and  11   b  will cause the distal end sections of the resilient blades  30   a  and  30   b  to rest on the outer face of the tube  50 . The earpieces are then separated by a larger angular spacing. From this larger angular spacing, further spreading apart of the earpieces  11   a  and  11   b  will bend the blades  30   a  and  30   b  to produce a tension on these earpieces  11   a  and  11   b.    
     When the diametrically opposite lugs  49  of the cam  47  are disposed in the second pair of diametrically opposite notches  46  as shown in FIG. 4, spreading apart of the earpieces  11   a  and  11   b  will cause the distal end sections of the blades  30   a  and  30   b  to rest on the free axial edge surface of the respective, diametrically opposite, axial and radial radial fins  51  of intermediate height. The earpieces  11   a  and  11   b  are then separated by an intermediate angular spacing. From this intermediate angular spacing, further spreading apart of the earpieces  11   a  and  11   b  will bend the blades  30   a  and  30   b  to produce a tension on these earpieces  11   a  and  11   b.    
     When the diametrically opposite lugs  49  of the cam  47  are disposed in the third pair of diametrically opposite notches  46  as shown in FIG. 5, spreading apart of the earpieces  11   a  and  11   b  will cause the distal end sections of the blades  30   a  and  30   b  to rest on the free axial edge surfaces of the respective, diametrically opposite, axial and radial fins  52  of larger height. The earpieces  11   a  and  11   b  are then separated by a smaller angular spacing. From this smaller angular spacing, further spreading apart of the earpieces  11   a  and  11   b  will bend the blades  30   a  and  30   b  and will produce a tension on these earpieces  11   a  and  11   b.    
     Accordingly, rotation of the cam  47  about its axis to displace the diametrically opposite lugs  49  from one pair of diametrically opposite notches  46  to the other, will change the angular spacing between the earpieces  11   a  and  11   b  allowed prior tension is applied to these earpieces. The user can thereby adjust the angular position of the button  47  in accordance with his requirements, needs and/or preferences. 
     Although the present invention has been described hereinabove by way of a preferred embodiment thereof, this embodiment can be modified at will, within the scope of the appended claims, without departing from the spirit and nature of the subject invention.

Technology Classification (CPC): 0