Patent Publication Number: US-7901334-B2

Title: Exercise apparatus with adjustable resistance assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Invention Patent Application No. 097125989, filed on Jul. 8, 2008. 
     BACKGROUND 
     1. Field of the Invention 
     This invention relates to an exercise apparatus, more particularly to an exercise apparatus with an adjustable resistance assembly. 
     2. Description of the Related Art 
       FIG. 7  illustrates a prior stationary bicycle  80 . The stationary bicycle  80  comprises a frame  81 , a seat  82 , a pedal mechanism  83  and a rotating member  84 . A user can sit on the seat  82  and drive the pedal mechanism  83  to rotate the rotating member  84  for exercising with basic intensity. Besides, the user can operate an adjustable resistance assembly  90  which is configured on the frame  81  over the rotating member  84  to increase or decrease friction resistance which is exerted on the rotating member  84 . The adjustable resistance assembly  90  can also be operated to immediately exert large friction resistance on the rotating member  84  to stop the rotating member  84  at short time. 
     Pleases refer to  FIG. 8 , the adjustable resistance assembly  90  comprises a guiding tube  86  approximately vertically mounted on the frame  81 . From top to bottom, there are a screw rod  91 , a medium spring  92  and a pushing lever  93  inside the guiding tube  86 . The top end of the screw rod  91  is higher than the guiding tube  86  and outside of the guiding tube  86 . A knob  94  is mounted on the top end of the screw rod  91 . Inside the guiding tube  86 , the screw rod  91  is threaded into a sliding unit  95 . The sliding unit  95  can be moved in a limiting range but can not rotate. There is a recovering spring  96  inside the lower portion of the guiding tube  86 . The pushing lever  93  runs through the recovering spring  96 . The top end of the recovering spring  96  contacts the pushing lever  93  and the bottom end thereof contacts the frame  81 . The bottom end of the pushing lever  93  is outside of the guiding tube  86  and connected to a front end of a lever unit  97 . The rear end of the lever unit  97  is pivotally connected to the frame  81 . There is a resistance member  98  pivotally connected to the central portion of the lever unit  97 . The resistance member  98  has an arc friction surface  99  for contacting the rotating member  84 . 
     According to the components relationship of the adjustable resistance assembly  90 , the pushing lever  93  bears upthrust force from the recovering spring  96  all the time. And the screw rod  91  also bears the upthrust force from the medium spring  92  all the time. Therefore, the sliding unit  95  is maintained at the top position in general. When the user rotates the knob  94 , the screw rod  91  is rotated relative to the sliding unit  95  and moved linearly downward or upward. By a buffer effect of the medium spring  92 , the pushing lever  93  is moved with the screw rod  91  in a slower rate. Thus, the front end of the lever unit  97  is gradually lifted or lowered and drives the resistance member  98  decreases or increases the friction resistance relative to the rotating member  84 . If the user wants to quickly stop the rotating member  84  as exercising, he can directly press the knob  94  to make the screw rod  91  move downward with the sliding unit  95 . And then the screw rod  91  and the medium spring  92  makes the pushing lever  93  press the front end of the lever unit  97  to make the friction surface  99  of the resistance member  98  contacts the rotating member  84  closely. Thus, he can stop the rotating member  84  at short time. 
     Another prior embodiment of the adjustable resistance assembly takes a torsion spring (not shown in  FIG. 8 ) to replace the recovering spring  96  as mentioned above. The torsion spring is interconnected to the rear end of the lever unit  97  and the frame  81 . A recovery elasticity of the torsion spring makes the front end of the lever unit  97  tends to rotate upward. Therefore, when the user rotates the knob  94  to move the pushing lever  93  upward or looses the pressing force, the lever unit  97  can push the pushing lever  93  upward and make the resistance member  98  leave the rotating member  84 . The torsion spring works as the recovering spring  96 . 
     This kind of adjustable resistance assembly is not only applied to stationary bicycles, but also applied to exercise apparatus which can be arranged a rotating member to produce exercise resistance such as cross trainer, stepper or skiing apparatus. 
     Although the functions of prior adjustable resistance assemblies are not inappropriate. However, the structure relationship and components of prior adjustable assemblies are still complicated and can be simplified to reduce manufacture cost. 
     SUMMARY 
     An adjustable resistance assembly of an exercise apparatus in accordance with present invention includes a control mechanism, an elastic member and a resistance member. The control mechanism is operable connected to a frame of the exercise apparatus. There is a screw portion of the control mechanism near a rotating member of the exercise apparatus. One portion of the screw portion which is near the rotating member is coupled to a pushing portion. Another portion of the screw portion which is far away the rotating member is connected to an operating portion which allows a user to rotate the screw portion to move toward or outward the rotating member. The elastic member has a first portion, a second portion and a third portion which are located at different positions of the elastic member. The first portion of the elastic member is connected to the frame. The second portion of the elastic member can be pushed by the pushing portion to move near the rotating member therefore causes deformation of the elastic member and storages recovering elasticity. The third portion of the elastic member is connected to the resistance member. With the elastic member being deformed, the resistance member comes closer to the rotating member and presses the rotating member with a friction surface. 
     In the invention, the elastic member has the functions similar to the medium spring, recovering spring and the lever unit in the prior art. Therefore, the structural relationship and components of present invention is simpler than the prior art. Clearly for the forgoing reasons, there is still a need for an adjustable resistance assembly of an exercise apparatus which can be manufactured with lower cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an adjustable resistance assembly according to a preferred embodiment applied to a stationary bicycle; 
         FIG. 2  is an exploded view of the adjustable resistance assembly of  FIG. 1 ; 
         FIG. 3  is a side cutaway view of the adjustable resistance assembly showing the operation status as the user rotates the adjustable resistance assembly; 
         FIG. 4  is a cutaway view about the IV-IV axis of  FIG. 3 ; 
         FIG. 5  is a cutaway view which is similar to  FIG. 4  showing the operation status as the user operates the adjustable resistance assembly to increase friction resistance suddenly; 
         FIG. 6  is a side cutaway view of an adjustable resistance assembly according to another embodiment; 
         FIG. 7  is a prior art showing a stationary bicycle having an adjustable resistance assembly; and 
         FIG. 8  is side cutaway view of the adjustable resistance assembly of  FIG. 7 . 
     
    
    
     DETAIL DESCRIPTION 
     Referring now specifically to the figures, in which identical or similar parts are designated by the same reference numerals throughout, a detailed description of the present invention is given. It should be understood that the following detailed description relates to the best presently known embodiment of the invention. However, the present invention can assume numerous other embodiments, as will become apparent to those skilled in the art, without departing from the appended claims. 
     Please refer to  FIG. 1 , a preferred embodiment of the present invention applied to an exercise apparatus  10  is depicted. The preferred embodiment is an adjustable resistance assembly  30  applied to a stationary bicycle. However, the present invention can also be applied to other indoor exercise apparatus, such as a cross-training exercise apparatus, a stepping exercise apparatus, or a skating exercise apparatus. 
     The exercise apparatus  10  comprises a frame  11  adapted to rest on a floor surface and to provide a foundation for other mechanisms to couple thereto, two exercising members  14  operatively connected to the frame  11  for a user to exercise. In this embodiment, the exercising members  14  are left and right pedals  15  connected to the frame  11  via left and right cranks  17 . The left and right pedals  15  allow the user to exercise as riding an outdoor bicycle. It can be appreciated by people skilled in the art that although the exercising members  14  of the preferred embodiment are left and right pedals  15  for imitating riding bicycle, other kinds of exercising members can be used depending on what kind of the exercising types are adapted, such as exercising members for running, stepping, or skating exercise. 
     Besides, there is a rotating member  16  pivotally connected to the frame  11 . The rotating member  16  can be driven to rotate as the user using the exercising members  14 . As shown in  FIG. 1 , the rotating member  16  is a fly wheel as people skilled in the art has already known. And, there are two pulleys (not shown) respectively coaxially coupled to the rotating member  16  and the left and right cranks  17 . There is a belt or chain (not shown) wound around the pulleys. Therefore, when the user exercises, the left and right pedals  15  are capable to drive the rotating member  16  by the belt. Furthermore, in this embodiment, whatever the user rotates the left and right pedals  15  clockwise or counterclockwise, the rotating member  16  rotates in the same direction according to the left and right pedals  15  simultaneously. However, in other embodiments, the exercising members  14  may drive the rotating member  16  to rotate only in a specific direction. If the user does not rotate the exercising members  14  in the specific direction or keeps the exercising members  14  idle, he does not need to burden with the weight and the rotational inertia of the rotating member  16 . 
     The adjustable resistance assembly  30  of the preferred embodiment is arranged higher than the rotating member  16  and behind a handgrip  13 . The user can operates the adjustable resistance assembly  30  by a single hand during exercise. Please refer to  FIG. 2  and  FIG. 3 , the adjustable resistance assembly  30  comprises a control mechanism  40  which is approximately vertically positioned, an elastic member  60  which is transversely interconnected between the frame  11  and bottom of the control mechanism  40 , and a resistance member  70  connected to the elastic member  60 . Top portion of the control mechanism  40  is higher than the frame  11  and allows the user to rotate or press. Bottom of the resistance member  70  is capable to press the rotating member  16  for exerting friction resistance thereon. 
     As shown in  FIG. 2  and  FIG. 3 , there is a metallic guiding tube  21  welded on the frame  11  above the rotating member  16 . Inside the guiding tube  21 , there is a guiding ring  22  mounted on the lower portion of the guiding tube  21  to decrease the inner diameter of the guiding tube  21 . 
     Now referring to the embodiment in  FIG. 3 , the control mechanism  40  may comprise a sliding unit  41 , a screw portion  44 , an operating portion  45 , and a pushing portion  51  additionally having a pushing lever  49  extended upward. The sliding unit  41  is a cylinder and the diameter thereof is slightly smaller than the inner diameter of the guiding tube  21 . The sliding unit  41  is coaxially accommodated in the upper portion of the guiding tube  21 . Referring to  FIG. 2 , the sliding unit  41  has a screw hole  42  which runs through the axis of the sliding unit  41 . And, the sliding unit  41  has a groove  43  on the outside surface. The length of the groove  43  is shorter than the sliding unit  41 . There is a pin hole  23  on the guiding tube  21  for screwing a screw-pin  24 . One distal end of the screw-pin  24  protrudes into the groove  43  of the sliding unit  41 , thereby the sliding unit  41  can be moved linearly along the guiding tube  21  without rotation. 
     The screw portion  44  is threaded through the screw hole  42  of the sliding unit  41 . Therefore, the lower portion of the screw portion  44  is inside the guiding tube  21 . Relatively, the upper portion of the screw portion  44  is outside the guiding tube  21 . The operating portion  45  is mounted on the top end of the screw portion  44 . Because the sliding unit  41  can not rotate, the operating portion  45  can directly rotate the screw portion  44  relative to the screw hole  42  of the sliding unit  41  as the user rotating the operating portion  45 . In the embodiment, there is an upper-limited nut  47  and a lower-limited nut  48  respectively disposed under and over the sliding unit  41 , and respectively screwed on the lower and upper portion of the screw portion  44  for limiting the moving range of the sliding unit  41 . In addition, there is a sleeve  46  clipped by the lower-limited nut  48  and the operating portion  45 . The inner diameter of the sleeve  46  is larger than the outer diameter of the guiding tube  21 . The sleeve  46  is configured to cover the top portion of the guiding tube  21  thereby covers part of the upper portion of the screw portion  44  outside of the guiding tube  21 . 
     Referring to  FIG. 3  again, the pushing portion  51  optionally has a lateral groove  52  opened downward. The pushing lever  49  extended from the pushing portion  51  is substantially inside the guiding tube  21 . The outer diameter of the pushing lever  49  is slightly smaller than the inner diameter of the guiding ring  22  which is mounted on the lower portion of the guiding tube  21 . The pushing lever  49  can be operated to move substantially upward and downward along the axis of the guiding tube  21 . The top end of the pushing lever  49  is movable engaged with the bottom end of the screw portion  44 , and the bottom end of the pushing lever  49  is outside the guiding tube  21 . 
     The elastic member  60  has a first portion  62  connected to the frame, a second portion  63  coupled to the pushing portion  51 , and a third portion  61 . In the embodiment of  FIG. 3 , the elastic member  60  is a torsion spring which is made of a single steel wire. The torsion spring has a coil portion between two ends. Accordingly, the third portion  61  of the elastic member  60  is the coil portion. The first and second portions  62 ,  63  of the elastic member  60  are oriented in opposite directions. Therefore, the first, second, and third portions  62 ,  63 ,  61  are located in different positions of the elastic member  60 . As illustrated in  FIG. 2 , the axis of the third portion  61  of the elastic member  60  is substantially corresponding to left-right direction. The third portion  61  is composed by two sets of coils which are apart from each other. And there are two parallel steel strips respectively extend from the coil portion. One portion of the two parallel steel strips which extend rearward forms as the first portion  62  of the elastic member  60 , and the other portion extending forward forms as the second portion  63  of the elastic member  60 . The distal ends of the second portion  63  are linked together which form as an engaging portion  65 . Each of the distal ends of the first portion  62  is formed as a U-shaped hook  64 . As depicted in  FIG. 2 , the length of the first portion  62  is obviously longer than the second portion  63 . Because the first portion  62  of the elastic member  60  is longer, it is easier to cause elastic deformation of the first portion  62  than the second portion  63  of the elastic member  60 . 
     The first portion  62  of the elastic member  60  is fixedly mounted on the frame  11 , and the second portion  63  of the elastic member  60  is coupled to the control mechanism  40 . Furthermore, in the embodiment of  FIG. 3 , the second portion  63  of the elastic member  60  is engaged with the groove  52  of the pushing portion  51  of the control mechanism  40  by the engaging portion  65 . The first portion  62  of the elastic member  60  is screwed on two lugs  25  which are collaterally mounted on the frame  11 . As shown in  FIG. 2 , the lugs  25  are two parallel panels. Each of the panels has a hole  26 . The U-shaped hooks  64  of the first portion  62  of the elastic member  60  are arranged between the parallel panels. And there is a separated ring  66  arranged between the U-shaped hooks  64 . A first screw  27  is threaded through the hole  26  of the panels, the U-shaped hooks  64 , and the separated ring  66 . And a first nut  28  is fastened up the end of the first screw  27  thereby fixes the first portion  62  of the elastic member  60  on the frame  11 . Because the first portion  62  of the elastic member  60  is fixedly mounted on the frame  11 , the first portion  62  of the elastic member  60  produces deformation when the pushing portion  51  initially pushes the second portion  63  of the elastic member  60  downward. The deformation of the first portion  62  of the elastic member  60  accumulates some energy. The accumulated energy moves the second portion  63  of the elastic member  60  upward when the pushing force from the pushing portion  51  is relieved. 
     Because the components are arranged as mentioned above, the elastic member  60  produces upward force to push the control mechanism  40 . Furthermore, even the screw portion  44  is at the top location, the elasticity of the elastic member  60  is not exhausted. In other words, even though the upper-limited nut  47  contacts the bottom of the sliding unit  41  and the user can not keep moving the screw portion  44  up, the engaging portion  65  of the second portion  63  of the elastic member  60  is still engaged with the pushing portion  51 . Therefore, the top end of the pushing lever  49  is maintained to movably contact to the bottom end of the screw portion  44  and keeps the sliding unit  41  at the top position within the moving range as shown in  FIG. 3  and  FIG. 4 . 
     In the embodiment of  FIG. 2  and  FIG. 3 , the resistance member  70  may comprises a metallic panel which includes a bottom panel  71  and left and right perpendicular panels  72 , and a friction unit  74  which has a friction surface  75 . There are two holes  73  respectively on the left and right perpendicular panels  72 . In the embodiment, the friction unit  74  is made of fiber, such as woolens. In other embodiments, the friction unit  74  can also be made of rubber, plastic, or other materials. The friction unit  74  is fixedly mounted on the bottom of the bottom panel  71 . The friction surface  75  is at bottom of the friction unit  74  and presented as an arc shape to match the surface of the rotating member  16 . In some embodiment, the friction unit  74  of the resistance member  70  is optional. For example, the bottom panel  71  and perpendicular panels  72  are made of plastic. The bottom surface of the bottom panel  71  can directly press the surface of the rotating member  16  and provide sufficient friction force. 
     The third portion  61  of the elastic member  60  is inserted into a tube  67 . There is a space between the outer diameter of the tube  67  and the third portion  61  of the elastic member  60 . The length of the tube  67  is longer than the third portion  61  of the elastic member  60 . The left and right perpendicular panels  72  of the resistance member  70  are respectively disposed at left end and right end of the tube  67 . A second screw  76  is threaded into the hole  73  of the left and right perpendicular panels  72  and the tube  67 . A second nut  77  is fastened up the end of the second screw  76  for pivotally connecting the resistance member  70  to the third portion  61  of the elastic member  60 . As depicted in  FIG. 3 , the friction surface  75  of the resistance member  70  is closely near the rotating member  16 . 
     Please refer to  FIG. 3  and  FIG. 4 , in general, the sliding unit  41  of the control mechanism  40  is located at the top position because the elastic member  60  contiguously exerting force to push up the control mechanism  40 . If the user rotates the operating portion  45  to drive the screw portion  44  to rotate, the screw portion  44  is capable to resist the force which is produced by the elastic member  60 . The sliding unit  41  is still approximately located at the top position because the sliding unit  41  still indirectly bears the force produced by the elastic member  60 . The sliding unit  41  can not rotate as described above. In the embodiment, when the user rotates the operating portion  45  clockwise, the screw portion  44  moves downward and toward the rotating member  16 . On the other hand, when the user rotates the operating portion  45  counterclockwise, the screw portion  44  moves upward and outward the rotating member  16 . 
     When the screw portion  44  moves downward, the pushing lever  49  is pushed by the screw portion  44  and moves downward a distance simultaneously. The engaging portion  65  of the elastic member  60  is also pushed to move downward substantially the same distance. Because the elastic member  60  has elasticity and the resistance member  70  is pressed to the rotating member  16 , the third portion  61  of the elastic member  60  does not move the same distance as the engaging portion  65  of the elastic member  60  does. In other words, when the second portion  63  of the elastic member  60  moves a first distance D 1  toward the rotating member  16 , the third portion  61  simultaneously moves a second distance D 2 . After the friction surface  75  pressing the rotating member  16 , the second distance D 2  increased is substantially zero. The first distance D 1  increased will cause deformation of the elastic member  60  and produce normal force to the rotating member  16  via the resistance member  70 . Because of the deformation of the elastic member  60 , the ratio the first distance D 1  to the second distance D 2  is not proportion or equal to another ratio of a third linear distance D 3  from the distal end of the second portion to the distal end of the first portion to a fourth linear distance D 4  from the center of the third portion to the distal end of the first portion ( FIG.3 ). Therefore, the current invention has a significant feature which the prior art of  FIG. 8  does not have. Because of this characteristic of the elastic member  60 , the ratio relationship of the first distance D 1  to the second distance D 2  is non-linear during the process of adjusting the adjustable resistance assembly  30 . More specifically, the ratio of the first distance D 1  to the second distance D 2  may change after the friction surface  75  pressing the rotating member  16 . With continuously increasing the first distance D 1 , the second distance D 2  becomes harder to increase. For example, if the screw portion  44  is at the top position, the friction surface  75  of the resistance member  70  is not contacting to the rotating member  16 . During the process of the screw portion  44  being rotated downward, the second portion  63  of the elastic member  60  is pushed to cause elastic deformation of the elastic member  60  and progressively inclines downward. As the phantom line shown in  FIG. 3 , when the screw,portion  44  continues to be rotated downward and makes the friction surface  75  of the resistance member  70  contacted the rotating member  16 , the second portion  63  and the third portion  61  of the elastic member  60  starts to occur elastic deformation to absorb the pushing force. At this time, the third portion  61  of the elastic member  60  rotates clockwise and the second portion  63  of the elastic member  60  moves in a direction consistent with the rotating direction of the third portion  61  of the elastic member  60 . Therefore, downward moving rate of the third portion  61  of the elastic member  60  is lower than another downward moving rate of the engaging portion  65  of the elastic member  60 . 
     In other words, if the pitch of the screw portion  44  is 1 mm and the user rotates the screw portion  44  ten rounds, the pushing portion  51  can push the engaging portion  65  of the elastic member  60  to move downward about 10 mm. However, as described above, the resistance member  70  and the third portion  61  of the elastic member  60  may probably move downward about 2 mm. The resistance member  70  gradually stops moving toward the rotating member  16  because of the counterforce force from the rotating member  16 . Instead, the first distance D 1  downward is gradually transferred to some normal force against the rotating member  16 . And the friction unit  74  of the resistance member  70  presses the rotating member  16  at this slower moving rate to gradually increase the friction resistance. 
     When the user rotates the operating portion  45  counterclockwise to move the screw portion  44  upward, the elastic member  60  can gradually recover from the elastic deformation and pushes the pushing lever  49  upward by recovering elastic force to make the top end of the pushing lever  49  keep contact with the bottom end of the screw portion  44 . At the same time, the recovering process of the elastic member  60  as described above also takes the resistance member  70  to leave the rotating member  16  at a moving rate lower than another rate of the screw portion  44  being moved upward. Therefore, the friction resistance gradually decreases. 
     Besides, if the user wants to make the rotating member  16  stop immediately, he can directly push the operating portion  45  downward to make the screw portion  44 , the sliding unit  41 , the pushing lever  49  and the second portion  63  of the elastic member  60  directly move downward quickly. As depicted in  FIG. 5 , the resistance member  70  is suddenly moved downward significantly, pressing the rotating member  16  with huge friction resistance and thereby stopping the rotating member  16  immediately. 
     The length of the first portion  62  of the elastic member  60  is longer than the length of the second portion  63  of the elastic member  60 . Because the length of the first portion  62  is longer, the first portion  62  is easier to be deformed than the second portion  63  of the elastic member  60 . In contrast, the second portion  63  is harder to be deformed. Therefore, there are generally two kinds of deformations of the elastic member  60 . Before the friction surface  75  contacting the rotating member  16 , the main deformation of the elastic member  60  is from the first portion  62 . After the friction surface  75  pressing the rotating member  16 , the deformation of the elastic member  60  is mainly from the rotating deformation of the third portion  61 . Such structural relationship makes the embodiment has better efficiency. 
     In  FIG. 3 , if the first portion  62  of the elastic member  60  is pivoted to the frame  11  instead of fixing thereto, the functions of adjusting the friction resistance and quickly stopping the rotating member  16  are still achievable. However, as the user rotating the operating portion  45  to move the screw portion  44  to the top position and thus to make the elastic member  60  recover to its natural status. There is no recovering elastic force to push the control mechanism  40  and the resistance member  70  upward. The elastic member  60  still burdens with the weight of the control mechanism  40  and the resistance member  70  presses on the rotating member  16  with its weight. So that, such method can not utilize the elastic member  60  to lift the resistance member  70  upward. 
     Referring to  FIG. 3  and  FIG. 8 , the elastic member  60  of the adjustable resistance assembly  30  replaces the medium spring  92 , recovering spring  96  and the lever unit  97 . Comparing to the elastic member  60 , the lever unit  97  of  FIG. 8  is relatively rigid. Therefore, the structural relationship of the invention is simpler than the prior art but still has the same functions. 
       FIG. 6  illustrates a second embodiment of present invention. Some difference is the second embodiment does not have the function of quickly stopping the rotating member  16 . Another difference is the second embodiment has fewer parts. The second embodiment uses a screw-hole unit  29  to replace the sliding unit  41  of  FIG. 3 . A screw portion  44 ′ of a control mechanism  40 ′ is engaged with the screw-hole unit  29 . The screw portion  44 ′ of the control mechanism  40 ′ still can be operated to rotate to move downward or upward, but can only be axially moved by rotating. Besides, the pushing portion  51 ′ is directly extended from the lower end of the screw portion  44 ′. In other words, the pushing lever  49 , the pushing portion  51  and the screw portion  44  of the first embodiment are combined to a single component in the second embodiment. And, an engaging portion  65 ′ of the elastic member  60 ′ supports the pushing portion  51 ′ of the control mechanism  40 ′ directly without any groove to constrain. Other structural relationship is the same with first embodiment. When the user rotates an operating portion  45 ′ of the control mechanism  40 ′, the whole control mechanism  40 ′ rotates together and moves downward or upward simultaneously. A resistance member  70 ′ which is connected to the elastic member  60 ′ simultaneously moving close to or far away the rotating member  16  as mentioned in the first embodiment. 
     The present invention does not require that all the advantageous features and all the advantages need to be incorporated into every embodiment thereof. Although the present invention has been described in considerable detail with reference to certain preferred embodiment thereof, other embodiments are possible. In the invention, if the screw portion of the control mechanism can not be directly moved without rotating, such as depicted in  FIG. 6 , the operating portion of the control mechanism is not limited to fixedly mounted on the screw portion. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained herein.