Abstract:
A disk device includes a disk unit housing a disk-shaped storage medium, a case holding the disk unit, a bracket holding the case, and a guide member guiding sliding movement of the case in and out from the bracket. The disk device also includes spring members on one of the bracket and the case, distributed in the direction of the relative movement. Each of the spring members extends longitudinally in the direction of the movement. Distal ends of the spring members face and press against the other of the bracket and the case. Base portions of the spring members are integral with the one of the bracket and the case. The spring members inhibit lateral vibration of the case by pressing against small projections on the case. Other spring members inhibit vertical vibration of the case by pressing against sliding support rails of the case. A face plate of the case absorbs vibration in the longitudinal direction.

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2007-233996 filed on Sep. 10, 2007, including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a disk device that incorporates an information storage medium and, more particularly, relates to a structure that prevents or minimizes vibration of a disk unit housed therein. 
     2. Description of the Related Art 
     Japanese Patent Application Publication No. JP-A-2005-135564 discloses a disk unit that is inserted into a receiving slot of an electronic device. The disk unit includes a hard disk, a drive motor, a read/write head, and a head actuator. The disk unit is inserted into a bottom cover of the electronic device. A control circuit board is mounted on top of the disk unit, and a top cover is placed over the disk unit and joined to the bottom cover. Windows are provided in the top cover, through which connector terminals on the control circuit board are exposed. Connector conductors in the electronic device make contact with the connector terminals on the control circuit board through the windows. 
     In Japanese Patent Application Publication No. JP-A-2007-141388, a hard disk drive (HDD) device is described in which a vibration absorbing cushion made of a rubber material is inserted between a support bracket and a support plate to which an HDD unit is fastened. A hook on the support plate is inserted into and engaged with a latch hole in the support bracket to fasten the HDD unit to the support bracket. 
     Japanese Patent 3122943 discloses a floppy disk device in which a loading mechanism, that includes a cassette holder and a slide member, is held by a bottom case that has threaded holes, for mounting, in a bottom face and in two side faces. Strain propagation is inhibited by mounting a head positioning mechanism and a disk drive mechanism as separate pieces on a substrate. The bottom case is described as preventing noise and penetration of dust into the disk device. 
     A HDD, used in a car navigation system in a vehicle, is required to have a structure that allows the HDD to be removed for maintenance. Accordingly, an HDD device has been proposed that provides the removability function wherein the HDD unit is mounted in a case to which it is secured by a threaded fastener, which case, in turn, is slidably inserted into a bracket on a slide structure. The slide structure holds the case (the HDD unit) such that connectors of the HDD unit are connected to and disconnected from joined to and separated from) connectors on the bracket upon insertion and removal of the case, respectively. However, in this proposed device, in order to facilitate attachment and removal of the HDD holding case to and from the bracket, a tiny gap is provided between the bracket and the case. Therefore, the HDD holding case is shaken by the vibration of the bracket that results from the vibration of the vehicle. Sympathetic vibration, in particular, produces a strong G-force (acceleration) in the HDD holding case which may cause instability in the writing and reading operations of the HDD. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to inhibit the propagation (transfer) of vibration to the disk unit. 
     To achieve the foregoing object, the present invention provides a disk device which includes a disk unit, a case, a bracket, and a guide member. The disk unit houses a disk-shaped information storage medium and the disk unit, in turn, is fixed (housed) within the case. The guide member guides relative sliding movement between the case and a bracket to allow for inserting the case into and removing the case from the bracket. 
     The disk device also includes a plurality of spring members having base portions fixed to one of the brackets and the case and distributed in the direction of the relative movement. Each of the spring members extends in the direction of the relative movement. Distal ends of the spring members face and press against the other of the bracket and the case, and base portions of the spring members are fixed to the one of the bracket and the case. 
     Because the base portions of the spring members are fixed to the one of the bracket and the case, and the tips (the free distal ends) of the spring members extend in the direction of the relative movement, even if the one of the bracket and the case vibrates, the vibration is absorbed by the spring members, and propagation (transfer) of the vibration to the other of the bracket and the case is inhibited. Only the distal ends of the spring members make contact with the other of the bracket and the case, so there is little frictional resistance to the relative movement, and the relative movement is smooth. 
     In a preferred embodiment of the present invention, the plurality of the spring members includes a first group, in which the distal ends of the spring members face a side panel of the other of the bracket and the case, and a second group, in which the distal ends of the spring members face a bottom or top planar surface of the other of the bracket and the case that is orthogonal to the side panels of the other of the bracket and the case. 
     In the above-described configuration, propagation of vibration from the bracket to the case, in the lateral direction, for example, is inhibited by the first group of the spring members. That is, a lateral vibration inhibition effect is achieved. Furthermore, propagation of vertical vibration from the bracket to the case, for example, is inhibited by the second group of the spring members. In other words, a vertical vibration inhibiting effect (feature) is also provided. 
     The first group of spring members, referred to above, may include a plurality that faces a first side panel of the other of the bracket and the case and a plurality that faces a second side panel opposite the first side panel. In this configuration, the spring members of the first group press against the two opposing side panels of the case in opposite directions. This further increases the lateral vibration inhibition effect. 
     The disk device may also include at least one small projection on each of the first side panel and the second side panel that is continuous with and is a part of (integral with) the side panel. The small projections protrude toward the spring members and are pressed against by the spring members to make reliable contact when the case is mounted in the bracket. Frictional resistance to the relative movement is also minimized, so that the relative movement is smooth. 
     The above-described spring members that face the first side panel, the spring members that face the second side panel, and the spring members of the second group that face the planar top or bottom panel may press against the other of the bracket and the case at a position where a plane that is orthogonal to the direction of the relative movement intersects the other of the bracket and the case. In this configuration, the spring members of the first group and the second group exert spring forces against the other of the bracket and the case at the same position in the direction of the relative movement. This makes it possible to effectively inhibit sympathetic vibration in the sheet metal from which the case is fabricated. 
     The disk unit may be fastened to the case at a plurality of points in a straight line that is orthogonal to the direction of the relative movement and that lies within the above-mentioned plane that is orthogonal to the direction of the relative movement. In this configuration, the spring members of the first group and the second group exert spring forces against the other of the bracket and the case at the points where the disk unit is fastened to the case. This makes it possible to effectively inhibit sympathetic vibration in the case, which is combined into a single unit with the disk unit. 
     In one embodiment, the guide member is on the bracket, supports the case from below and guides the relative movement. In such an embodiment, the planar surface, described above as orthogonal to the side panel of the case, may be folded rails that extend inwardly from the side panels and longitudinally in the direction of the relative movement. In this configuration, the spring members press against the rails, inhibiting vertical vibration of the case relative to the bracket. There is little resistance to the sliding by the spring members, so that the sliding is smooth. 
     The spring members may be blade springs that are bent such that they protrude toward the other of the bracket and the case. In this configuration, the tips (the free distal ends) of the spring members will not catch on, but will instead slide smoothly over, the small projections on the other of the bracket and the case when the case is inserted into and removed from the bracket. Thus, the case can be inserted into and removed from the bracket more smoothly. 
     The bracket may be formed by press punching of a metal sheet, and the spring members may be formed by press punching, leaving their base portions connected. Manufacturing the bracket by press punching is easy, and because each of the spring members is integral with the bracket, the manufacturing of the spring members is also easy. Moreover, because the bracket is made of metal, it can easily provide electrical grounding. 
     Forming the case by press punching of a metal sheet not only makes the manufacturing of the case easy, it also makes it possible for the case and the bracket to be electrically connected through the spring members. If the bracket is then at ground potential, the case automatically also becomes grounded. Electrically connecting a device grounding conductor of the disk unit to the case makes it possible for the disk unit to also be at the ground potential of the bracket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view of a hard disk drive (HDD) device (apparatus) that is one embodiment of the present invention; 
         FIG. 1B  is a left side view that shows the HDD device of  FIG. 1A ; 
         FIG. 1C  is a right side view of the embodiment of  FIG. 1A ; 
         FIG. 2  is an oblique exploded view of the HDD device shown in  FIG. 1A ; 
         FIG. 3  is an enlarged oblique view of a portion SIL of a bracket  4  shown in  FIG. 2 ; 
         FIG. 4  is an oblique view that shows a rear edge of the bracket  4  shown in  FIG. 2 ; and 
         FIG. 5  is an enlarged oblique view that corresponds to  FIG. 3  and shows a modification of the HDD device of  FIGS. 1A-4  as another embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described with reference to the drawings. 
     Embodiment 1 
       FIGS. 1A-1C  show a hard disk drive (HDD) device as one embodiment of the present invention. The HDD device is installed in a vehicle and provides map information, road information, and the like to a navigation system. 
     An HDD unit  1  shown in  FIG. 2  is a disk unit which contains a hard disk, a drive motor, a read-write head, a head actuator, and a control circuit board, as in a conventional HDD unit. A male connector (not shown in the drawings) includes a plurality of connector pins which extend in a case insertion direction F ( FIG. 2 ) toward the rear edge of the control circuit board. When the male connector is pushed into the case in direction F, the male connector connects to a female connector  51  in a printed wiring panel  5  that is mounted on the bracket  4 . A metal bottom plate (not shown in the drawings), that is electrically connected to grounding conductor of the control circuit board, is provided on the bottom face of the HDD unit  1 . Four female threaded holes are provided in the bottom plate. 
     A case  2  is slidable relative to the bracket  4  in the insertion direction F (y) and a removal direction B, as shown in  FIG. 2 . The bracket  4  is positioned on and secured by a threaded fastener to a metal (electrically conductive) mounting substrate (not shown in the drawings) on the vehicle body. The bracket  4  includes a guide rail  41  which serves as a guide member for guiding the sliding movement and for supporting the case  2  from below. The bracket  4  includes another guide rail opposite the guide rail  41  in the x direction but is hidden in the perspective view of  FIG. 2 . The bracket  4  and the case  2  are formed from sheet metal by press punching and press bending. 
     The case  2  includes first and second side panels  21   a ,  21   b  that extend at right angles (upward and vertical in use) from a bottom panel  24 . Upper edges of the first and second side face panels  21   a ,  21   b  are bent inward toward the interior of the case  2 , forming rails  22   a ,  22   b  extending in direction F (y). A first group of five roughly conical small projections  23   a ,  23   c  and a second group of five roughly conical small projections  23   b ,  23   d  that project outwardly from the case  2  are respectively formed in the first and second side panels  21   a ,  21   b  by pressing. The first group of the small projections, which includes small projections  23   a ,  23   c , and the second group of the small projections, which includes  23   b ,  23   d  are each five in number, and in each of the groups, the five projections are aligned in the insertion direction F. Four protrusions that project upward in the z direction are formed in the bottom panel  24  of the case  2  by pressing and a threaded through-hole  25   d  is provided in each of the protrusions. A face plate  27  extends at a right angle upwardly from the bottom panel  24  of the case  2 , and a threaded through-hole  28  is provided in the face plate  27 . The small projections  23   a  to  23   d  are not necessarily cones and, alternatively, may be, for example, four-sided pyramids, three-sided pyramids, hemispheres, cut-out quarter-spheres, press-punched tongues with one edge attached or any other shape, so long as each projection has an inclined surface which, when the case  2  is pulled outwardly from the bracket  4 , makes contact with a distal end of one of four blade springs  42   a ,  42   b ,  42   c ,  42   d  in the bracket  4  (described later) such that it pushes the distal end upward. 
     The HDD unit  1  is inserted into the case  2  from above through the space between the rails  22   a ,  22   b . The HDD unit is then secured within the case  2  by four screws  3   a  to  3   d  which are inserted from below, through the four respective threaded through-holes  25   d  in the bottom panel  24  and into four female threaded holes provided in the metal bottom plate on the bottom face of the HDD unit  1 . A male connector (not shown in the drawings) of the HDD unit  1  is located on the rear face of the HDD unit  1  that is opposite the front face of the HDD unit  1  where the face plate  27  is located. When the case  2  is inserted into the bracket  4 , the male connector becomes connected to the female connector  51  in the printed wiring panel  5  that is mounted on the rear of the bracket  4 , extending at a right angle to the top panel of the bracket  4 . 
     The bracket  4  has first and second side panels that respectively face the first and second side panels  21   a ,  21   b  of the case  2  from the outside. The blade springs  42   a ,  42   c  on the first side panel are formed by press punching such that a U-shaped outline is punched out leaving one end of each of the blade springs continuous with the sheet material of the bracket  4 . The blade springs  42   b ,  42   d  on the second side face panel are formed in the same manner ( FIG. 1B ). The blade springs  42   a ,  42   c  and  42   b ,  42   d  are slightly bent toward the interior of the bracket  4  in order to strengthen the spring forces that press on the case  2 . Each of the blade springs  42   a ,  42   c  and  42   b ,  42   d  extends in the insertion direction F, and the distal ends of the springs are positioned to engage the small projections  23   a ,  23   c  and  23   b ,  23   d  of the case  2  when mounted within the bracket  4  ( FIGS. 1B ,  1 C). 
     The bottom edges of the first and second side panels of the bracket  4  are bent inward, toward the interior of the bracket  4 , to form the guide rail  41  and another guide rail that is opposite the guide rail  41  in the x direction. Blade springs  43   a ,  43   c  and  43   b ,  43   d  of the same type as blade springs  42   a ,  42   c  and  42   b ,  42   d  are formed in the x-y planar top panel of the bracket  4 , and positioned to press against the rails  22   a ,  22   b  of the case  2 . As shown in  FIG. 4 , a pair of printed wiring panel support pieces with threaded screw holes  44   a ,  44   b  and an opening  45 , that receives a stop projection  57  on the printed wiring panel  5 , are provided at the rear edge of the bracket  4 . A stop piece  47  with a threaded screw hole  46  is provided at the front edge of the bracket  4 , rising from the top panel at a position where the screw hole  46  aligns with the threaded through-hole  28  in the face plate  27  of the case  2  ( FIGS. 2 and 4 ). 
     The front and rear faces of the printed wiring panel  5  are each provided with a grounding conductor (the reference numeral  52  denotes the device grounding conductor on the front face), and the female connector  51  is fastened to the printed wiring panel  5 . An electrical cable (a flat cable) is connected to the female connector  51  on the rear face of the printed wiring panel  5 , but is omitted from the drawings. In the female connector  51 , a connector terminal that accepts a device grounding pin of the male connector of the HDD unit  1  is connected to a device grounding wire of the electrical cable and is also connected to the device grounding conductor  52  which is in the form of at least one face (for example, on the front face) of the printed wiring panel  5 . The printed wiring panel  5  is joined to form a single unit with the bracket  4  and secured by inserting the projection  57  of the printed wiring panel  5  into the slot opening  45  of the bracket  4 , bringing the device grounding conductor  52 , i.e. the front face of the printed wiring panel  5 , into contact with the printed wiring panel support pieces of the bracket  4  ( FIG. 4 ), and then inserting screws  55 ,  56  through threaded through-holes  53 ,  54  in the printed wiring panel  5 , and into the screw holes  44   a ,  44   b  ( FIG. 4 ) in the printed wiring panel support pieces of the bracket  4 . With the printed wiring panel  5  thus mounted on the bracket  4 , the device grounding conductor  52  (front face of the printed wiring panel  5 ) is in direct contact with (electrically connected to) the bracket  4 , and the rear face of the printed wiring panel  5  is electrically connected to the bracket  4  through the screws  55 ,  56 . 
     The HDD device is assembled as shown in  FIGS. 1A ,  1 B and  1 C by mounting the printed wiring panel  5  on the printed wiring panel support pieces on the rear edge of the bracket  4 , pushing the case  2 , in which the HDD unit  1  is mounted, in the insertion direction F, to insert the case  2  into the opening at the front of the bracket  4  on the guide rails  41  and to connect the male connector of the HDD unit  1  to the female connector  51  of the printed wiring panel  5 . A screw  29  ( FIGS. 1A ,  1 B and  1 C) is then inserted through the threaded through-hole  28  in the face plate  27  and then into the screw hole  46  in the bracket  4 . 
     The electrical cable that is connected to the female connector  51  of the printed wiring panel  5  is omitted from  FIGS. 1A ,  1 B and  1 C. As seen in  FIG. 2 , in the bracket  4 , the portion of the stop piece  47  below the screw hole  46  extends below the top panel of the bracket  4 , so that it serves as a stopper. Therefore, during the assembly of the HDD device, if the case  2  is inverted (such that the top of the HDD unit  1  is facing downward), the case  2  cannot be inserted into the bracket  4 , because the rear edge of the bottom panel  24  will catch on the lower stopper portion of the threaded stop piece  47 . Thus, the stop piece  47  has a stopper function that prevents the case  2  from being mounted in the bracket  4  in an incorrect orientation (upside down). 
     In the HDD device shown in  FIGS. 1A ,  1 B and  1 C, the case  2  ( FIG. 2 ), in which the HDD unit  1  ( FIG. 2 ) is mounted, is supported from below by the guide rail  41  ( FIG. 2 ) of the bracket  4 . The tips (the free distal ends) of the blade springs  43   a  to  43   d  of the bracket  4  press downward with a spring force on the rails  22   a ,  22   b  of the case  2  and thereby press the case  2  against the guide rails of the bracket  4  (one of which is shown as  41 ). Thus the blade springs  43   a  to  43   d  absorb vibration that would otherwise be propagated (transferred) from the bracket  4  to the case  2  in the vertical direction z. That is, the propagation of vibration from the bracket  4  to the case  2  in the vertical direction z is inhibited. 
     Further, the distal ends of the blade springs  42   a  to  42   d  of the bracket  4 , shown in  FIGS. 1B and 1C , press with a spring force against the small projections  23   a  to  23   d  on the side panels  21   a ,  21   b  ( FIG. 2 ) of the case  2 . Thus, spring forces hold the case  2  from both the left and the right. In this manner, blade springs  42   a  to  42   d  absorb vibration that would otherwise be propagated (transferred) from the bracket  4  to the case  2  in the left-right direction x. That is, propagation of vibration in the left-right direction x is inhibited. Note that the three small (inboard) projections of the same type between the small projections  23   a  and  23   c  on the first side panel  21   a  ( FIG. 2 ), as well as the corresponding three small projections of the same type on the second side panel  21   b , limit the amplitude of the relative vibration between the bracket  4  and the case  2  in the left-right direction x and also prevent bumping of the case  2  laterally (in direction x) against the bracket  4  when the case  2  is slid in the directions F, B during insertion and removal, respectively. 
     The face plate  27  ( FIGS. 1A ,  1 B  1 C and  2 ) of the case  2  is separable from the side panels  21   a ,  21   b . The face plate  27  extends vertically (at a right angle) from the bottom panel  24  and is connected by the screw  29  ( FIGS. 1A ,  1 B and  1 C) at a fairly high position, to the stop piece  47 , which extends vertically upward from the bracket  4 . The face plate  27  therefore readily vibrates in the insertion and removal directions F, B relative to the bottom panel  24 . That is, the face plate  27  absorbs vibration that would otherwise be propagated (transferred) from the bracket  4  to the case  2  in the insertion and removal directions F, B. In other words, the propagation of vibration in the longitudinal direction y is inhibited. Furthermore, pin receiving conductors in the female connector  51  of the printed wiring panel  5  press with a spring force against the connector pins of the male connector of the HDD unit  1  that is mounted in the case  2 . Thus, the vibration that would otherwise be propagated (transferred) from the bracket  4  to the case  2  in the insertion and removal directions F, B is also absorbed where the male and female connectors are connected. That is, the propagation of vibration in the longitudinal direction y is further inhibited. 
     Referring to  FIGS. 1A ,  1 B,  1 C and  2 , near the opening at the front edge of the bracket  4 , the blade spring  42   a  that faces the first side panel  21   a , the blade spring  42   b  that faces the second side panel  21   b , as well as the blade springs  43   a ,  43   b  that respectively face the rails  22   a ,  22   b , press on the case  2  at positions where a plane PL (an x-z plane), that is orthogonal to the insertion direction F (y), intersects the case  2 . Thus, the blade springs  42   a ,  43   a ,  43   b ,  42   b  exert spring forces against the case  2  at positions that are the same in relation to the insertion direction F (y), inhibiting sympathetic vibration near the front edge of the sheet metal of the case  2 . 
     Near the rear edge of the bracket  4 , the blade spring  42   c  that faces the first side panel  21   a , the blade spring  42   d  that faces the second side panel  21   b , as well as the blade springs  43   c ,  43   d  that respectively face the rails  22   a ,  22   b , press on the case  2  at positions where an x-z plane, that is orthogonal to the insertion direction F (y), intersects the case  2 . Thus the blade springs  42   c ,  43   c ,  43   d ,  42   d  exert spring forces against the case  2  at positions that are the same in relation to the insertion direction F (y), inhibiting sympathetic vibration near the rear edge of the sheet metal of the case  2 . 
     Because the blade springs  42   a ,  43   a ,  43   b ,  42   b  press against the case  2  near the front edge, at the position where the straight lateral line, defined by the alignment of the screws  3   a ,  3   b  that secure the HDD unit  1  to the case  2 , and where the plane PL intersects the case  2 , the effect of inhibiting the sympathetic vibration in the case  2 , which is combined into a single unit with the HDD unit  1 , is particularly strong at that location. 
     When the HDD device shown in  FIGS. 1A-1C  is installed in a vehicle and connected to a navigation system, the device grounding conductor of the control circuit board inside the HDD unit  1 , that is mounted in the case  2 , is electrically connected, through the device grounding pin of the male connector of the HDD unit  1  and the terminal that accepts the pin in the female connector  51 , to the grounding wire of the electrical cable that is connected to the female connector  51 . Through that grounding wire, the device grounding conductor is electrically connected to a common grounding conductor of the vehicle. The terminal that accepts the device grounding pin in the female connector  51  is also connected to the device grounding conductors on the front and rear faces of the printed wiring panel  5  (the front face  52  serves as a device grounding conductor). The device grounding conductors are electrically connected to the bracket  4  and a portion of the device grounding conductors is electrically connected to the bracket  4  through the screws  55 ,  56 . The bracket  4  is also electrically connected to the common ground of the vehicle through threaded fasteners in a metal plate, not shown in the drawings, that is at the common ground potential of the vehicle. The device grounding conductor of the control circuit board inside the HDD unit  1  is also electrically connected to the metal bottom plate of the HDD unit  1 . The (bottom panel  24  of the) case  2  is electrically connected to the bottom plate through the screws  3   a  to  3   d . By the contact between the small projections  23   a  to  23   d  of the case  2  and the blade springs  42   a  to  42   d , by the contact of the case  2  with the guide rail  41  of the bracket  4 , by the contact of the blade springs  43   a  to  43   d  with the rails  22   a ,  22   b  of the case  2 , and by the electrical connection between the face plate  27  and the threaded stop piece  47  by the screw  29 , the case  2  is electrically connected to the common grounding conductor of the vehicle through the bracket  4 . 
     Because of the large number of electrical grounding routes from the HDD unit  1  to the common grounding conductor of the vehicle, the resistance of the contact between the device grounding conductor of the HDD unit  1  and the common grounding conductor of the vehicle is low, the electromagnetic interference (EMI) from the HDD unit  1  is reduced. Because of the high reliability and high stability of the spring-loaded mechanical contacts (electrical connections) between the blade springs  42   a  to  42   d  and the small projections  23   a  to  23   d , and between the blade springs  43   a  to  43   d  and the rails  22   a ,  22   b , the EMI that is generated by the HDD unit  1  is absorbed and reduced. Reliable and stable electrical noise reduction is thereby provided. 
     The blade springs  42   a  to  42   d  and  43   a  to  43   d , as shown in  FIG. 5 , for example, are bent to protrude toward the case  2 . Alternatively, the blade springs may be bent into V shapes or curved shapes such that the apexes of the V shapes or the curved shapes protrude toward the case  2 . If the blade springs are thus bent, the tips (the free distal ends) of the blade springs will not catch on, but will instead slide smoothly over, the small projections  23   a  to  23   d  of the case  2  when the case  2  is inserted into the bracket  4  in the insertion direction F and when the case  2  is removed from the bracket  4  in the removal direction B. Thus, the case  2  can be smoothly inserted into and removed from the bracket  4 . 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.