Abstract:
Disclosed is unit brake, which is equipped with a cylinder apparatus in which a clutch mechanism that switches between transmitting or cutting off a biasing force of a spring brake part is disposed, is capable of preventing a braking force due to the spring brake part from unintentionally decreasing due to a meshing section of the clutch mechanism disengaging, and is of a size that can replace an existing unit brake, and maintains the performance of bearings in the clutch mechanism even with long-term use. The clutch mechanism of the unit brake includes: a nut member that rotatably screws on a spindle that is positioned in an area that communicates with the atmosphere, and is movably supported in a direction opposite to braking; a clutch that is disposed in a direction opposite to braking with respect to the nut member, and faces the nut member in the vicinity of the spindle; a clutch box that is formed in a cylinder shape, and houses the nut member and clutch on the inside; and bearings that rotatably support the nut member on the inside of the clutch box.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/JP2012/004271 filed Jul. 2, 2012, and claims priority to Japanese Patent Application No. 2011-163325 filed Jul. 26, 2011, the disclosures of which are hereby incorporated in their entirety by reference. 
     TECHNOLOGY FIELD 
     This Invention relates to a unit brake with a regular brake part and a spring brake part. 
     BACKGROUND TECHNOLOGY 
     A cylinder device and a brake body attached to this cylinder device are equipped as a unit brake for vehicle braking, to activate the cylinder device, and bring a brake shoe retaining relative displaceability versus the brake body into contact with the vehicle wheel, to brake the rotation of the vehicle wheel. For the cylinder device in this type of unit brake, for example, in brake devices for rail vehicles, cylinder devices are known that can be activated with both a regular brake part activated with compressed air (compressed fluid) used in normal operations, and a spring brake part activated by a spring force even without use of compressed air, used for stopping the vehicle over a long time (see Patent Citation 1). In the cylinder device disclosed in Patent Citation 1, the regular brake part has a rod protruding and has installed a first piston used in opposition to a first pressure chamber and first spring, and the spring brake part has a rod penetrating and has installed a second piston used in opposition to a second pressure chamber and second spring. In addition, compressed air is supplied to the first pressure chamber, to move the first piston in the brake direction, in resistance to the first spring added force, and furthermore, compressed air is exhausted from the second pressure chamber, to move the second piston in the brake direction, using the second spring added force. 
     In addition, in the above-mentioned cylinder device, a clutch function is installed that links the rod and second piston are linked, and releases that link, switching between transmitting or blocking the spring brake part added force. In this clutch mechanism, rotatability is supported versus the second piston, and a nut member screwed into the rod is installed. Moreover, this clutch mechanism is configured so as to move from a state where compressed air is supplied to the second pressure chamber to an exhaust state, and the nut member moves together with the second piston versus the rod, by the second spring added force, so that the rod and second piston are linked to form a linked state. By contrast, in the state where compressed air is supplied to the second pressure chamber, this clutch mechanism is configured so that the link between the rod and second piston is released, to form a non-linked state. In this cylinder device, the clutch mechanism moves to the above-mentioned link state, and is designed so that the convex-concave teeth in the nut member in the clutch mechanism, and in the sleeve member that is the opposite-side member, are linked by mutual gripping, and the brake force is maintained in the spring brake part. 
     ADVANCED TECHNOLOGY CITATION 
     Patent Citation 
     Patent Citation 1: Laid Open No. 2008-101766 Publication 
     Patent Citation 2: Laid Open No. 2010-164193 Publication 
     SUMMARY OF INVENTION 
     Issues that Invention Attempts to Solve 
     In the above-mentioned clutch mechanism in the cylinder device disclosed in Patent Citation 1 (Laid Open No. 2008-101766 Publication), when the nut member moves together with the second piston, the forward tip parts of the convex-concave teeth in the nut member and sleeve member come into contact with each other first. At this time, contact resistance with the sleeve member that obstructed displacement of the rotation direction easily causes the nut rotation to be stopped. As a result, there are cases where the convex-concave teeth in the nut member and sleeve member do not fully grip all the way to the back, and the rod and second piston remain linked with only the forward tip parts gripped together. If left standing in this kind of linked state, the compressed air in the first pressure chamber of the regular brake part is steadily outgassed, and activation of the first pressure chamber causes the added force of the first piston to weaken, then the brake shoe or the carriage structural member formed from composite materials that is deflected by this added force, overlaps with the force from the spring element installed on the carriage compressed or expanded by this added force, leading to a reaction force from the brake shoe side, and this reaction from the brake shoe side causes the first piston to be pushed back slightly in a direction opposite to the brake direction, and at the same time, the rod formed as a unit with the first piston is also pushed back slightly in a direction opposite to the brake direction, so that the clutch mechanism gripped part, which had only been gripped at the forward tips only, comes completely loose, and the brake force for the spring brake part used as the parking brake, etc., is unintentionally relaxed. In particular, this tendency becomes much more notable when the first piston added force is large while parked because the reaction force from the brake shoe side also grows larger. 
     In addition, while use of the unit brake listed in Patent Citation 2 (Laid Open No. 2010-164193 Publication) solves the above-mentioned issue, there is a problem in that it cannot be exchanged as is for existing vehicles where the Patent Citation 1 (Laid Open No. 2008-101766 Publication) unit brake is used, because of an installation space problem. Furthermore, since the bearing used in the clutch mechanism of the unit brake listed in Patent Citation 2 (Laid Open No. 2010-164193 Publication) is used inside a compressed air atmosphere generated by a compressor, there is a problem of adverse effects due to humidity, etc. In particular, the said problem appears quite notably in cases of vehicles used overseas where dehumidification devices are not installed. 
     In a unit brake equipped with a cylinder device with a clutch mechanism installed for switching between transmission and blocking the added force of the spring brake part, this Invention takes the above-mentioned situation into consideration to set an objective to provide a unit brake that can prevent unintentional relaxation of the brake force by the spring brake part due to disengagement of the clutch mechanism gripping part, that is a size enabling replacement of existing items, and that can maintain the clutch mechanism bearing performance even during long-term use. 
     Method for Resolving the Issue 
     (1) The unit brake related to this Invention is a unit brake equipped with a cylinder device with a spindle positioned in a region in communication with the atmosphere, a brake lever capable of swinging around a support axis through movement in the spindle axial direction, and a brake shoe receptacle linked to and driven by the brake lever, and the cylinder device has a first piston operating by opposing a first pressure chamber to a first spring positioned in a region in communication with the atmosphere and, with compressed fluid supplied to the first pressure chamber, has a regular brake part moving in the brake direction of the brake force generated by the first piston in resistance to the first spring added force, and a second piston operating by opposing a circular second pressure chamber installed opposing the first pressure chamber to a second spring installed concentrically on the outside of the first pressure chamber, and where a spindle has a specified gap for penetrating the central part, and has a spring brake part that moves from a state of supplying compressed fluid to the second pressure chamber to an exhausting state where the second piston moves in the brake direction by the second spring added force, a nut member rotatably screwed in versus the spindle, and with clutch part installed on the anti-brake direction in the opposite direction from the brake direction, a clutch engaged in the nut member clutch area on the side opposing the said nut member in the area around the spindle that was positioned in the anti-brake direction in a direction opposite to the brake direction versus the nut member, a clutch box forming a cylinder and housing the nut member and clutch on its inside, and a supporting bearing that can rotate the nut member versus the clutch box on the inside of the clutch box, and furthermore, the clutch is equipped with a clutch mechanism where displacement of the brake direction and anti-brake direction versus the clutch box is enabled, and the rotation direction displacement is regulated, and the clutch mechanism is positioned in a region where the first spring is positioned, on the inside of the circular ring of the second pressure chamber, and further in the brake direction than the second piston, with compressed fluid also exhausted from the second pressure chamber, so that the clutch is moved by the second spring added force, together with the second piston, in relation to the clutch box, to engage the clutch part of the nut member, and to enter a linked state where the spindle and second piston are linked and the nut member is non-rotatable, and compressed fluid is supplied to the second pressure chamber, resulting in the clutch becoming separated from the nut member, to become a non-linked state where the link between the spindle and second piston is released. 
     According to the above-mentioned configuration, the clutch opposing the nut member in the area around the spindle that was positioned in a region in communication with the atmosphere is positioned in the anti-brake direction versus the nut member, and when the clutch mechanism is moved in a linked state, the clutch moves together with the second piston to grip the clutch part of the nut member. In addition, the nut member screwed into the spindle and rotatably supported is supported to enable moving in the anti-brake direction. For this reason, if the compressed fluid in the first pressure chamber of the regular brake part is slowly outgassed, the first piston added force is weakened due to action of the first pressure chamber, and the first piston is pushed in the anti-brake direction by the spring-back reaction force from the brake shoe side, the nut member will be pushed in deeply gripping direction toward the clutch. With this action, even if the compressed fluid in the first pressure chamber is outgassed and the spring-back reaction force from the brake shoe side is activated, the disengagement of the gripping part with the nut member and clutch in the clutch mechanism is prevented. As a result, unintentional relaxation of the brake force in the spring brake part that is used as a parking brake, etc., is prevented. 
     In addition, with the above-mentioned configuration, the loosening of the mutual gripping part in the clutch mechanism, and the unintentional relaxation of braking force due to the spring brake part can be prevented. Furthermore, since a protruding part as seen in Patent Citation 2 is not generated in the cylinder back part, the installation space problem can also be solved. 
     In addition, with the above-mentioned configuration, since the first pressure chamber in the anti-brake direction of the clutch box holding the bearing is installed, exposure of the bearing to the compressed fluid can be prevented. In addition, in the same way, since the second pressure chamber on the outer side of the clutch box holding the bearing on the inner side is installed, exposure of the bearing to the compressed fluid can be prevented. Furthermore, since air surrounding the bearing flows smoothly, even if the atmosphere becomes humid, if the atmosphere afterward becomes drier, the atmosphere around the bearing also dries out. As a result, since grease applied to the bearing can be prevented from deterioration due to oil or water incorporated in the compressed fluid, it can maintain performance even through long-term use. 
     (2) In the above-mentioned unit brake, the spindle has a specified gap for penetrating the central part of the clutch, the clutch disengagement spring that applies force to the clutch in the anti-brake direction versus the clutch box is positioned concentrically on the outer side of the nut member, and the bearing is installed so that it faces the region where the clutch disengagement spring is positioned. 
     With the above-mentioned configuration, the air in the atmosphere passes through a specified gap formed between the spindle and clutch, and transits between the clutch and nut member to adequately supply the region where the clutch disengagement spring is positioned. It follows that, even if the atmosphere becomes humid, if the atmosphere afterward becomes drier, the air in the region where the clutch disengagement spring is positioned also dries out. As a result, grease applied to the bearing can more surely prevent deterioration due to a humid atmosphere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  Cross-section illustration showing the general configuration of the unit brake applied to the first Embodiment of the Invention. 
         FIG. 2  Partial expanded illustration of the region shown at  FIG. 1A . 
         FIG. 3  Illustration showing the state when the regular brake of the unit brake in  FIG. 1  is activated. 
         FIG. 4  Illustration showing the state when the spring brake of the unit brake in  FIG. 1  is activated. 
         FIG. 5  Cross-section illustration showing unit brake in other examples. 
         FIG. 6  Cross-section illustration at the D-D line arrow position in  FIG. 5 . 
     
    
    
     EXPLANATION OF KEY CODE 
     
         
         
           
               100 ,  100   a  Unit brake 
               10  Cylinder device 
               20  Brake lever 
               30  Brake shoe receptacle 
               50 ,  50   a  Spindle 
               60  Regular brake part 
               61  first piston 
               64  first pressure chamber 
               66  Return spring member (first spring) 
               70  Spring brake part 
               71  second piston 
               71   b  Side wall 
               74  second spring chamber 
               75  Spring member (second spring) 
               81  Nut member 
               82  Clutch box 
               83  Bearing 
               84  Clutch 
             S 1  Gap 
             S 2  Gap 
           
         
       
    
     DESCRIPTION OF THE INVENTION 
     Here follows a description of the unit brake related to the Embodiment of this Invention, with reference to the illustrations. 
     &lt;General Configuration of Unit Brake  100 &gt; 
     The unit brake  100  related to the Embodiment of this Invention is configured as a railroad car brake device. This unit brake  100  is equipped mainly with a cylinder device  10  for generating force, a brake lever  20  enabling swivel motion versus the movement of the cylinder device  10 , a brake shoe receptacle  30  that can be moved forward and back by the swivel motion of the brake lever  20 , and on which is mounted a brake shoe not shown in the illustration, a casing  40  that is formed in a hollow shape, and with an interior that enables communication with the atmosphere. In this casing  40 , a connection hole  41  is formed, and a bolt not shown in the illustration inserted into this connection hole  41  is set so that the casing  40  can be fixed to a vehicle carriage. 
     &lt;Brake Lever  20 &gt; 
     The brake lever  20  is housed in the casing  40 . This brake lever  20  is supported by a rotatable spindle  21  mounted inside the casting  40 . Also, the brake lever  20  is distributed in a stance that extends in the up and down directions. 
     The spindle  21  is installed in the intermediate area of the brake lever  20 . Also, the brake lever  20  is formed as an arm part  22  on the side higher than the spindle  21 , and a bearing hole  24  is installed on the side lower than the spindle  21 . 
     A spherical bearing  26  is fitted into the bearing hole  24 , and a sheathed rod  28  is fixed into the inner ring of this spherical bearing  26 . The sheathed rod  28  is formed in a cylindrical shape, with a female screw cut on the inner surface. Also, a spindle  29  is screwed into the sheathed rod  28  female screw. With this action, the spindle  29  can have the protrusion volume adjusted in relation to the sheathed rod  28 . 
     &lt;Casing  40 &gt; 
     An upper side first opening  42 , upper side second opening  43 , and lower side opening  44 , are formed in the casing  40 . The upper side first opening  42  is formed in the upper part of the casing  40  vehicle wheel side sidewall  45  (side wall on the left side of  FIG. 1 ), and a cylinder device  10  is attached to plug up this upper side first opening  42 . 
     The lower side opening  44  is formed in the lower part of the vehicle wheel side sidewall  45 . The spindle  29  passes through the lower side opening  44  to protrude toward the vehicle wheel side, and a brake shoe receptacle  30  is installed at the tip part. 
     A ventilation cylinder  40   a  is installed in the lower part of the casing  40 , and there is communication between the outside atmosphere and the interior of the casing  40 . 
     &lt;Cylinder Device  10 &gt; 
     The cylinder device  10  is equipped with a spindle  50  with a multiple thread screw on the side surface, and this spindle  50  is moved along the axial direction to swivel the brake lever  20 . 
     This cylinder device  10  is mainly equipped with the above-mentioned spindle  50 , a regular brake part  60  used for decelerating or stopping a running vehicle, a spring brake part  70  used for vehicle parking, etc., and a clutch mechanism. The regular brake part  60  and spring brake part  70  are configured so as to be operated by the shared spindle  50 . 
     &lt;Regular Brake Part  60 &gt; 
     The regular brake part  60  operates through compressed and other fluid pressure force. This regular brake part  60  is equipped with a first piston  61  connected to the base end part of the spindle  50 , a return spring member  66  positioned in a region providing the casing  40  air (equal to atmospheric pressure) from grooves in the multiple thread screw of the spindle  50  installed so as to penetrate the second spindle  71  described below, or gaps in each member, or in other words, a region communicating with the atmosphere, and a cylindrical first cylinder body  62  with bottom that can swivel-handle the first piston  61 . 
     A first port  63  for supplying and exhausting compressed fluid is installed in the first cylinder body  62 , and inside the first cylinder body  62 , a first pressure chamber  64  is formed in communication with this first port  63 . In the first pressure chamber  64 , compressed air and other compressed fluids are supplied or exhausted in response to the specified brake operation, and the first piston  61  moves in resistance to the added force of the return spring member  66 . Also, the first pressure chamber  64  is formed from the first piston  61  and the first cylinder body  62 . This first pressure chamber  64  is partitioned in the anti-brake direction by a clutch box  82  that is described below. 
     &lt;Spring Brake Part  70 &gt; 
     The spring brake part  70  activates with a spring elastic force due to a spring member  75 , described below. This spring brake part  70  is penetrated by the spindle  50 , and equipped with a second piston  71  movable in the axial direction (arrow X direction) of the spindle  50 , and a second cylinder body  72  that can swivelably house the second piston  71 . The second cylinder body  72  has a trunk part  73  installed on the outward circumference side of the trunk part  65  of the first cylinder body  62 . In addition, the second piston  71  is configured to be contactable to the tip area of the trunk part  65  of the first cylinder body  62 . The second cylinder body  72  is fixed in the casing  40 . Between the second piston  71  and the casing  40  vehicle wheel side sidewall  45  is formed a second pressure chamber  74  that supplies compressed air and other compressed fluids by way of a second port (omitted from the illustration). This second pressure chamber  74  is formed from the second piston  71 , the casing  40 , and the second cylinder body  72 . In addition, the second pressure chamber  74  is formed from a cylindrical shape installed facing the first pressure chamber  64 . Also, the second pressure chamber  74  is partitioned in the outer side of the clutch box  82 , described below. In addition, the spindle  50  is installed maintaining and penetrating a specified gap in the central part of the second piston  71 . 
     Also, a spring member  75  is installed on the side opposite the second pressure chamber  74  versus the second piston  71 . This spring member  75  is positioned between the trunk part  65  of the first cylinder body  62  positioned on the inner side, and the trunk part  73  of the second cylinder body  72  positioned on the outer side, and also positioned concentrically on the outer side of the first pressure chamber  64 , and is compressed by reception of fluid pressure inside the second pressure chamber  74 . While a normal compressed fluid is introduced into the second pressure chamber  74 , compressing the spring member  75 , performance of a specified brake operation exhaust the compressed fluid inside the second pressure chamber  74 , and the spindle  50  is moved in the brake direction (arrow X1 direction) based on the spring force of the spring member  75 . 
     The second piston  71  of this Embodiment has a clutch housing part  71   a  where the central part of the spindle  50  side forms a bump on the first piston  61  side, and the clutch mechanism described below is housed on the inner side of this clutch housing part  71   a . Also, in this Embodiment, in the tip area of the spindle  50  side of the second piston  71 , a sidewall  71   b  is formed stretching along the axial direction (arrow X direction) of the spindle  50 . A thrust bearing  85 , described below, is held in this sidewall  71   b . Also, in this Embodiment, a gap S 1  where air can pass is formed between the sidewall  71   b  and the spindle  50 . 
     Meanwhile, the return spring member  66  is positioned between the first piston  61  and the second piston  71 . This return spring member  66  pressures the first piston  61  in the compression direction (anti-brake direction (arrow X2 direction) of the first pressure chamber  64 , and when a compressed fluid is introduced to the first pressure chamber  64 , it is compressed by this fluid pressure. Since normally there is no compressed fluid introduced inside the first pressure chamber  64 , the spindle  50  moves in the anti-brake direction (arrow X2 direction) based on the spring force of the return spring member  66 . Also, compressed fluid is introduced to the first pressure chamber  64  by the specified break force, and the spindle  50  moves in the brake direction (arrow X1 direction). Moreover, when the compressed fluid inside the first pressure chamber  64  is exhausted by the specified brake release operation, the spindle  50  is returned to the initial state by the spring force of the return spring member  66 . 
     &lt;Clutch Mechanism&gt; 
     The clutch mechanism switches the nut member  81  rotation and fixed. Specifically, the clutch mechanism allows rotation of the nut member  81  versus the spindle  50  when the regular brake part  60  is driven, and fixes the nut member  81  versus the spindle  50  when the spring brake part  70  is driven. The clutch mechanism in the Embodiment, as is described below, is positioned in a region that does not interfere with the first pressure chamber  64  and second pressure chamber  74 . 
     The clutch mechanism, not shown in the illustration, mainly has the nut member  81 , the clutch box  82  housing the nut member  81  in its inner side, a bearing  83  rotatably supporting the nut member  81  versus the clutch box  82 , a clutch  84  positioned opposing the nut member  81 , a thrust bearing  85  rotatably supporting the clutch box  82  versus the second piston  71 , a clutch box stay spring  86 , and a clutch spring  87 . This clutch mechanism is normally locked to disable rotation by a lock lever  88 , described below. 
     The nut member  81  is rotatably screwed versus the spindle  50 . In addition, the nut member  81  is rotatably supported by way of the bearing  83  versus the clutch box  82 . With this action, the nut member  81  is rotated by relative motion of the spindle  50  and the clutch box  82 . In addition, the nut member  81  is rotatably supported together with the clutch box  82  toward the anti-brake direction (arrow X2 direction) which is the reverse direction. Also, in the part facing the clutch  84  of the nut member  81 , a mutually gripping (connecting) external gear  81   a  is formed in the external gear  84   a  of the said clutch  84 . 
     In addition, when the clutch external gears  81   a ,  84   a  are connected, motion toward the brake direction and anti-brake direction is allowed versus the clutch box  82 , but rotation direction displacement toward the spindle  50  axis area is restricted. 
     The clutch box  82  is formed as a cylindrical member positioned on the inner side of the nut member  81  and the clutch  84 . A key  82   a  linking the said clutch box  82  and clutch  84  is fixed within this clutch box  82 . This key  82   a  is positioned in a groove  84   b  formed in the clutch  84 . With this action, the clutch  84  is in a state versus the clutch box  82  where rotation direction displacement centering on the spindle  50  axial direction is restricted, and it slides in parallel along the axial line direction (arrow X direction). In other words, the clutch box  82  slidably supports the clutch  84  along the second piston  71  movement direction. 
     In addition, in the clutch box  82  is installed a clutch disengagement spring  82   b  that adds force in a direction moving away from the nut member  81 . This clutch disengagement spring  82   b  is installed on the inner side of the clutch box  82  (spindle  50  side), and concentrically on the outer side of the nut member  81  and clutch  84 . In addition, the clutch box stay spring  86  is installed between the clutch box  82  and the second piston  71 . 
     The clutch  84  is formed as a cylindrical member, and is positioned in the anti-brake direction (arrow X2 direction) versus the nut member  81 . Also, in this Embodiment, a gap S 2  where fluid can pass is formed between the clutch  84  and the spindle  50 . Moreover, this clutch  84  is installed around the spindle  50  so as to face the nut member  81 . The clutch  84  is rotatably supported by the second piston  71 , by way of the thrust bearing  85 , at the tip area of the anti-brake direction (arrow X2 direction). With this action, when the second piston  71  moves along the brake direction (arrow X1 direction) versus the spindle  50 , based on the added force of the spring member  75 , the clutch  84  also moves together with the second piston  71  in the brake direction (arrow X1 direction) versus the spindle  50 , by way of the second piston  71  and the thrust bearing  85 . 
     The above-mentioned clutch mechanism is a region where the return spring member  66  is positioned, and is positioned on the inner side of the second pressure chamber  74  ring. In addition, the position of the said clutch mechanism is positioned more in the brake direction (arrow X1 direction) than is the second piston. 
     The clutch mechanism transitions from a state where compressed air is supplied to the second pressure chamber  74 , to a state where it is exhausted, and the clutch  84  is moved together with the second piston  71  in the brake direction (arrow X1 direction) versus the spindle  50 , by the added force of the spring member  75 , to set a linked state mutually gripped with the nut member  81  (mutually gripping the external gear  81   a  of the nut member  81  and the external gear  84   a  of the clutch  84 ), and linking the spindle  50  and the second piston  71 . 
     Meanwhile, in the state where compressed air is supplied to the second pressure chamber  74 , the clutch  84  becomes separated from the nut member  81  (the external gear  81   a  and external gear  84   a  are not mutually gripping), and the nut member  81  enters a freely rotating state. For this reason, when in the state where compressed air is supplied to the second pressure chamber  84 , the clutch mechanism is set to a non-linked state where the link of the spindle  50  and the second piston  71  is released. 
     In the cylinder device  10 , the lock lever  88  is installed to enable switching between the clutch mechanism locked state and unlocked state. A latch gear  82   c  is installed on the outer circumferential surface of the clutch box  82  brake direction (arrow X1 direction), and a lock gear  88   a  that is configured to enable connection with the said latch gear  82   c  is installed in the inner tip area of the lock lever  88 . The lock lever  88  uses and added force member  89  to add force in the direction connecting the lock gear  88   a  to the latch gear  82   c , and lifting up the lock lever  88  releases the connection between the latch gear  82   c  and lock gear  88   a , which action puts the clutch box  82  in a rotatable state. This configuration enabling release of the clutch box  82  lock state is to enable manual release of the spring brake part  70  when a situation arises where for some reason the compressed fluid in the second pressure chamber  74  is exhausted, putting the spring member  75  of the spring brake part  70  in extended state (the spring brake part  70  is in an operations state). 
     &lt;Spindle  50 &gt; 
     The spindle  50  has a screwing part formed by multiple screws on the outward circumference side, and an extension part extending in the axial direction (arrow X1 direction) from the tip of this screwing part. Also, the nut member  81  of the clutch mechanism is screwed into this screwing part. With this action, the nut member  81  is enabled to move in the arrow X direction versus the spindle  50 . 
     The spindle  50  is inserted into the upper side first opening  42 . In the extension part, a partially cut-off area is formed on the outer circumferential surface, with a specified length in the axial direction. In the said area, a pair of wall parts are formed facing the axial direction of the spindle  50 . 
     One of the wall parts (first wall part)  54  has a contact surface contacting the brake lever  20  when the spindle  50  is advancing, and the other wall part (second wall part)  55  has a contact surface contacting the brake lever  20  when the spindle  50  is retreating. Between the two wall parts a gap is formed where a force point part  23  can be inserted. 
     In the connection part, a pair of flat surfaces are formed as side surfaces. These flat surfaces are positioned symmetrically versus the spindle  50  axis, and form flat, almost vertical surfaces to the axis. The above-mentioned perforation hole is opened in this connection part. In other words, since the interval between both surfaces of the connection part (width of connection part) is smaller than the diameter of the perforation hole, the perforation hole is opened on the side surface of the connection part so that each flat surface is divided into top and bottom. 
     An expanded diameter area is installed in this perforation hole, and a wear ring  57  is fitted into this expanded diameter area. 
     The brake lever  20  has the force point part  23  installed in the upper tip part (front tip part), or in other words, the upper tip part (front tip part) of the arm part  22 . This force point part  23  is an area that accompanies the spindle  50  drive, and receives force from the said spindle  50 , and is inserted into the space between the spindle  50  wall parts. 
     A guide rod is inserted into the perforation hole of the spindle  50 . The base end part of the guide rod is fixed to the vehicle wheel in the casing  50  and to the sidewall  46  on the opposite side, and it is positioned in the same axial shape as the spindle  50 . 
     A pair of flat surfaces are formed in the guide rod. When the guide rod is inserted into the spindle  50  perforation hole, these flat surfaces form a surface shape together with the flat surface of the spindle connection part. 
     Next is a description of the unit brake  100  operation. 
       FIG. 1  is a cross-section illustration of the cylinder device  10  when neither the regular brake part  60  nor the spring brake part  70  are in operation. For example, when the brake operation is not being performed while a rail vehicle is in operation, it becomes the state shown in  FIG. 1 . In this state, a regular brake control device (not shown in the figure) controls so that the supply of compressed air from an air supply source (not shown in the figure) by way of the first port  63  to the first pressure chamber  64  is not performed. Also, compressed air within the first pressure chamber  64  is naturally exhausted by way of the first port  63 . For this purpose, the first piston  61  uses the return spring member  66  to add force in the anti-brake direction (arrow X2 direction), and the first piston  61  enters a state of contact with bottom part of the first cylinder body  62 . 
     Meanwhile, in the state shown in  FIG. 1 , compressed air is supplied to the second pressure chamber  74  by way of the second port (not shown in the figure) from an air supply source (not shown in the figure), based on the control of a spring brake control valve (not shown in the figure). For this purpose, added force based on the operation of compressed air supplied to the second pressure chamber  74  puts the second piston  71  in a state of moving in the anti-brake direction (arrow X2 direction) in opposition to the added force of the spring member  75 . In this state, the external gear  81   a  of the nut member  81 , and the external gear  84   a  of the clutch  84  are not mutually gripping, and a state forming a gap is entered. 
       FIG. 3  is a cross-section illustration of the cylinder device  10  showing a state where the regular brake part  60  has been activated. Based on control of the regular brake control device, compressed air is supplied to the first pressure chamber  64  by way of the first port  63 , to activate the regular brake part  60 . At this time, the added force by use of compressed air supplied to the first pressure chamber  64  moves the first piston  61  in the brake direction (arrow X1 direction) in opposition to the added force of the return spring member  66 . With this action, the spindle  50  moves in the brake direction together with the first piston  61 , pushing the brake shoe against the tread surface of the vehicle wheel, to generate braking force. However, when the spindle  50  moves in the brake direction together with the first piston  61 , since the nut member  81  is freely supported by the bearing  83  versus the clutch box  82 , together with the spindle  50  move in the brake direction, the nut member  81  rotates while being supported by the clutch box  82 . With this action, only the spindle  50  will move in the brake direction. 
       FIG. 4  is a cross-section illustration of the cylinder device  10  showing a state where the spring brake part  70  has been activated. When activating the spring brake  70 , for example, in a state where the regular brake part  60  is activated (see  FIG. 3 ) when the rail vehicle has been completely stopped, the spring brake part  70  becomes activated for use as a parking brake, etc. Based on control of the spring brake control device (not shown in the figure), compressed air is exhausted from the second pressure chamber  74  for activation. 
     When compressed air that has been supplied to the second pressure chamber  74  is exhausted, the added force of the spring member  75  starts the second piston  71  moving in the brake direction (arrow X1 direction). At this time, the clutch  84  that freely rotates to the thrust bearing  85  supported by the second piston  71  begins to move together with the second piston  71  in the brake direction versus the spindle  50 . Note that, at this time, the clutch  84  moves in the brake direction by a sliding operation with the groove  84   b  and key  82   a  versus the clutch box  82 . Also, when the second piston  71  begins in this way to move together with the clutch  84  versus the spindle  50 , the clutch  84  comes into contact with the nut member  81 . In other words, the external gear  81   a  of the nut member  81 , and the external gear  84   a  of the clutch  84 , are mutually gripping, and the nut member  81  rotation stops. 
     As described above, the nut member  81  and clutch  84  are mutually gripping, so that the clutch mechanism moves from a non-linked state to a linked state. Also, since the nut member  81  rotation can be stopped in this linked state, force is added to the spindle  50  by way of the clutch  84  and nut member  81  when the second piston  71  is moving in the brake direction based on the added force of the spring member  75 , and the spindle  50  is maintained in the state where the first piston  61  and spindle  50  are moving in the brake direction. In other words, it is maintained in the state where the spring brake part  70  is activated and the spring brake force is used. 
     &lt;Characteristics of Unit Brake  100  in this Embodiment&gt; 
     As described above, in the Embodiment, the clutch  84  facing the nut member  81  around the spindle  50  is positioned in an anti-brake direction versus the nut member  81 , and when the clutch mechanism is moving in a linked state, the clutch  84  moves together with the second piston  71  to mutually grip with the nut member  81 . Also, the nut member  81  that is screwed in to the spindle  50  and rotatably supported is supported to enable movement in the anti-brake direction. For this reason, the first pressure chamber  64  compressed fluid in the regular brake part  60  is slowly outgassed, causing the added force of the first piston  61  based on activation of the first pressure chamber  64  to weaken, and when the first piston  61  is pushed in the anti-brake direction by spring-back reaction force from the brake shoe side, the nut member  81  is pushed deeply in the mutually gripping direction toward the clutch  84 . With this action, even if the first pressure chamber  64  compressed fluid is outgassed and the spring-back reaction force from the brake shoe side is activated, disengagement of the nut member  81  and clutch  84  mutually gripping pat in the clutch mechanism is prevented. For this reason, unintentional relaxation of the brake force in the spring brake part  70  used as a parking brake, etc., is prevented. 
     Furthermore, in the Embodiment, since the clutch mechanism is positioned in a region that does not interfere with the first pressure chamber  64  and second pressure chamber  74 , it can prevent the size of the cylinder device  10  from growing larger. Particularly since it does not generate a protruding part like that in the unit brake listed in Patent Citation 2, it can prevent the outward form of the cylinder device from growing larger. As a result, an existing unit brake can be replaced with the unit brake  100  where the spring brake is not unintentionally relaxed, without needing to make any changes to the configuration on the rail vehicle side. 
     And again furthermore, in the Embodiment, since the first pressure chamber is installed in the anti-brake direction of the clutch  84  box holding the bearing  83 , the bearing  83  is not exposed to compressed fluid, and in the same way, since the second pressure chamber  74  is installed on the outer side of the clutch  84  box holding the bearing  83  on its inner side, the bearing  83  is not exposed to the compressed fluid. In other words, since the bearing  83  surroundings are filled with air from outside, and since the grease coating the bearing will not deteriorate due to oil or water incorporated in the compressed fluid, performance can be maintained even over long-term use. 
     In addition, in the Embodiment, since a gap traversable by fluid is formed between the sidewall and the spindle  50 , and between the clutch  84  and spindle  50 , air from the outside is fully supplied by way of this gap to inside the space contained in the return spring member  66 . It follows that, even when the atmosphere is temporarily humid, if the atmosphere afterward becomes drier, the atmosphere around the bearing also dries out. As a result, prevention of deterioration of the grease coating the bearing  83  due to a humid atmosphere can be more certainly suppressed. 
     Other Example 
     Here follows descriptions of another example. For this other example, the description will be mainly of points that differ from the above-mentioned Embodiment. 
     As shown in  FIG. 5 , the unit brake  100   a  is equipped with a spindle  50   a  in place of the spindle  50 . The spindle  50   a  is equipped with a holding case  57   a .  FIG. 6( a ), ( b )  is an illustration showing a cross-section of the holding case  57   a , and as shown in  FIG. 6( a ) , the spindle  50   a  uses a rotation added force spring  57   d  to add force in a reverse rotation direction (arrow E direction in the figure) to the rotation direction where the nut member  81  is deeply screwed into the spindle  50   a  by way of a pin member  50   c.    
     For this reason, in a state where the tip parts of the external bearing  81   a  and external bearing  84   a  are in contact with each other, as shown in  FIG. 6( a ) , the spindle  50   a  maintains its position with the pin member  50   c  in a state of engagement with the stepped part of the inner wall of the holding case  57   a.    
     Here, if in a state where the spring brake method is fully activated, utilization in the spindle  50   a  of the rotation force in the rotation direction shown at arrow D in  FIG. 6( a )  puts the spindle  50   a  in a state enabling rotation in that rotation direction. Also, the spindle  50   a  comes to rotate in the rotation direction (rotation direction at arrow D in  FIG. 6( a ) ) where the nut member  81  is deeply screwed into the spindle  50   a  in opposition to the spring force of a rotation added force spring  57   d  activated in the pin member  50   c . With this action, the nut member  81  moves slightly in the same direction as the brake direction, and is slightly rotated, to enable deep screwing into the spindle  50   a . Also, the contact position of the external bearing  81   a  and external bearing  84   a  is moved slightly from the position where the tip parts are in contact with each other, so that the external bearing  81   a  and external bearing  84   a  are adjusted to a deeper mutually gripping position. 
     In addition, the spindle  50   a  is rotatable in a direction shown by the arrow in  FIG. 3  until both tips of the pin member  50   c  contact a protrusion wall part  57   b  in the inner wall of the holding case  57   a . In other words, the pin member  50   c  becomes capable of swiveling in the angle range shown at both tips arrow J in  FIG. 6( b ) , and the rotatable angle of the spindle  50   a  is regulated. 
     Also, if the external bearing  81   a  and external bearing  84   a  are deeply mutually gripping, and the clutch  84  is in a mutually gripping state, a latch bearing  82   c  of the nut member  81 , and a lock bearing  88   a  of the lock lever  88  are in a state of engagement, so that linked rotation to rotation accompanying the movement of the nut member  81  in the brake direction is stopped. For this reason, rotation of the nut member  81  can be eventually stopped. 
     Note that if the clutch  84  is in a mutually gripping state, the nut member  81  moves together with the second piston  71  slightly in the brake direction in opposition to the added force of the rotation added force spring  57   d , and the engagement of the latch bearing  82   c  of the nut member  81 , and the lock bearing  88   a  of the lock lever  88 , deepens in the axial direction so that the second piston  71 , the nut member  81 , and the clutch  84 , become stopped. 
     As described above, the external bearing  81   a  and external bearing  84   a  are mutually gripping, and the nut member  81  and clutch  84  move from a non-linked state to a linked state. Also, in the linked state, since the nut member  81  rotation is stopped, the second piston  71  uses the added force of the spring member  75  to add force to the spindle  50   a  by way of the clutch  84  when in a state moving in the brake direction, and a state where the spindle  50   a  and the first piston  61  remain moved in the brake direction is maintained as is. In other words, the spring brake force is maintained in an activated state. 
     Note that the reaction from the brake shoe receptacle  30  pushed against the tread surface of the vehicle wheel is activated in the anti-brake direction versus the first piston  61  and the spindle  50   a , so that even when the nut member  81  and the clutch  84  are about to be disengaged, there is no disengagement because the mutual gripping is so deep, and the first piston  61  and spindle  50   a  are maintained in the brake state position. 
     For example, in cases where wanting to use a tractor vehicle to slightly move the parking position of a rail vehicle without going so far as to activate the air compression function, cases where power is not supplied to the rail vehicle so that a tractor vehicle is used to move the rail vehicle, or other such where wanting to release the spring brake force, the lock lever  88  can be operated to manually release the spring brake force. In this case, if manual operation is used to pull up the lock lever  88  from the state where the sub brake is activated, toward the outer side of the first cylinder body  62 , the lock bearing  88   a  of the lock lever  88  is disengaged from the latch bearing  82   c  of the nut member  81 . Also, it becomes rotatable with the external bearing  81   a  and external bearing  84   a  remaining in a state of mutual gripping, and the clutch  84  becoming empty spinning. 
     With this action, both the first piston  61  and the second piston  71  can use the added force of the return spring member  66  and the spring member  75  to mutually move to the stroke end, and the spindle  50   a  and the first piston  61  come to move in the anti-brake direction. In this way, the lock lever  88  can be operated to manually release the spring brake force and move the rail vehicle, etc. 
     In the other example above, the effectiveness of the Embodiment was successfully obtained, and the following effectiveness was also successful. In the other example, grease was coated even within the holding case  57   a , but since use occurred in the atmosphere, there was no exposure within compressed air. Therefore, deterioration of the grease (lubricating material, etc.) due to oil or water incorporated in the compressed fluid can be suppressed. As a result, performance can be maintained even over long-term use. 
     While the above was a description based on the illustrations regarding the Embodiment of this Invention, it is important to remember that the specific configuration is not limited to these Embodiments. The scope of this Invention is shown not only through the description of the above-mentioned Embodiments, but also through the scope of the Patent Claims, and all changes are incorporated within the scope of the Patent Claims and the scope of equivalent meanings. 
     (Correspondence Relationship of Each Configuration Elements the Claims, to Each Part in the Above-Mentioned Embodiments) 
     In the above-mentioned Embodiments, the unit brakes  100 ,  100   a  correspond to “unit brake”, the spindles  50 ,  50   a  correspond to “spindle”, the cylinder device  10  corresponds to “cylinder device”, the brake lever  20  corresponds to “brake lever”, the brake shoe receptacle  30  corresponds to “brake shoe receptacle”, the first pressure chamber  64  corresponds to “first pressure chamber”, the return spring member  66  corresponds to “first spring”, the first piston  6  corresponds to “first piston”, the regular brake part  60  corresponds to “regular brake part”, the second pressure chamber  74  corresponds to “second pressure chamber”, the spring member  75  corresponds to “second spring”, the second piston  71  corresponds to “second piston”, the spring brake part  70  corresponds to “spring brake part”, the nut member  81  corresponds to “nut member”, the clutch  84  corresponds to “clutch”, the clutch box  82  corresponds to “clutch box”, the bearing  83  corresponds to “bearing”, and the clutch mechanism corresponds to “clutch mechanism”.