Patent Publication Number: US-7721544-B2

Title: Actuator

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2006-351435 filed in Japan on 27 Dec. 2006, and 35 U.S.C. §119(e) on U.S. Provisional Application No. 60/884,560 filed on 11 Jan. 2007, which are incorporated by reference. 

   BACKGROUND OF INVENTION 
   1. Field of Invention 
   The present invention relates to an actuator used in an  3  airbag type restraining device or the like. 
   2. Description of Related Art 
   As an occupant restraining device or a pedestrian protection device of a vehicle, there are, in addition to an airbag type restraining device, a device for lifting up the hood of a vehicle in order to protect a pedestrian and a device for retracting the steering wheel (shaft/column), and a pyrotechnic actuator is used in such devices. 
   There is a known actuator in which a pin (piston) is pushed out or retracted upon activation, and, in either case, it is necessary to fix the piston before activation so that it does not move. 
   In an actuator combined with the above-mentioned restraining device, even after driving the piston, the piston needs to be prevented from returning to its initial position, thus it is preferred, in terms of size and weight reduction of the entire device, that the structure for inhibiting the movement of the piston before and after the activation be simple. 
   US-B1 No. 6,675,692 relates to a pyrotechnic actuator. As shown in FIG. 1, there is disclosed an actuator in which a piston 2 is slidably disposed within a housing 1 and is driven by a detonator 3. An oblong cavity 2b is formed on the piston 2, and a projection 9 is caused to pass therethrough. A lock (locking element) 8 is disposed so as to surround the projection 9. When a free end 8a abuts on the projection 9 before activation, the piston is inhibited from moving. In FIG. 2, an object corresponding to the lock 8 shown in FIG. 1 is formed in plurality. 
   In FIG. 7, two studs 2z that are attached to the piston 2 are bent inward by at least a certain amount of force and pass through the piston 2 with respect to the projection. There is disclosed in the 11th through 17th lines of Column 5 that the piston 2 is fixed by the studs 2z before and after activation. 
   In the actuator of EP-B1 No. 1162333, a piston is disposed within a cylinder and a piston fixing member 13 locks a piston 2 prior to activation (upper left of the drawing). The fixing member 13 is in the form of a washer, and by fitting an inner peripheral portion thereof into an annular groove 12 formed on the piston 2, the piston is inhibited from moving before activation. 
   SUMMARY OF INVENTION 
   The present invention provides an actuator including: 
   a cylinder connected to an ignition device; 
   a piston slidably accommodated inside the cylinder, the piston having, in a desired section in the length direction, an enlarged diameter portion in which an outer diameter is enlarged; 
   a cylindrical stopper attached to an inner peripheral surface of the cylinder, the stopper including,
         a main body portion which is fixed to the inner peripheral surface of the cylinder, and   a nail portion which inwardly projects from the main body portion and is formed of an elastic material, wherein   before activation of the ignition device, the piston is inhibited from moving in an axial direction by causing the nail portion to contact a part of the enlarged diameter portion,   after activation of the ignition device, the piston is inhibited from moving in a backward direction by causing the nail portion to contact another part of the enlarged diameter portion.       

   The invention also provides an actuator including: 
   a cylinder connected to an ignition device; 
   a piston slidably accommodated inside the cylinder; 
   a cylindrical stopper attached to an outer peripheral surface of the piston, the stopper including,
         a main body portion which is fixed to the outer peripheral surface of the piston, and   a nail portion which outwardly projects from the main body portion and is formed of an elastic material, wherein   before the activation of the ignition device, the piston is inhibited from moving in an axial direction by causing the nail portion to contact a peripheral edge of an opening portion of the cylinder,   after the activation of the ignition device, the piston is inhibited from moving in a backward direction by the nail portion which has popped out of the cylinder and spreads wider than a diameter of the opening portion of the cylinder.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: 
       FIG. 1  shows a longitudinal sectional view of the actuator of the present invention in a state before activation; 
       FIG. 2  shows a longitudinal sectional view of the actuator of the present invention in a state after activation; 
       FIG. 3  shows a perspective view of a stopper of an embodiment different from that shown in  FIG. 1 ; 
       FIG. 4  shows a longitudinal sectional view of the actuator of another embodiment of the present invention in a state before activation; 
       FIG. 5  shows a longitudinal sectional view of the actuator of another embodiment of the present invention in a state after activation; and 
       FIG. 6  shows a perspective view of the stopper of an embodiment different from that shown in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF INVENTION 
   In FIG. 1 of U.S. Pat. No. 6,675,692, the projection 9 deforms the free end 8a of the lock 8 at the time of activation and moves from a 2b′ space to a 2b″ space, but it is difficult to completely fix the piston after activation because of the wide 2b″ space. Also, in FIG. 2, it is possible to fix the piston after activation, but the structure is complicated since a plurality of the locks 8 are used. 
   In FIG. 7 of U.S. Pat. No. 6,675,692, on the other hand, there is disclosed that the piston can be fixed before and after activation, but the movement of the piston is not locked in the drawing, particularly before activation, thus it is assumed that the locking function is not exercised sufficiently. 
   In the actuator of EP-B1 No. 1162333, when the piston moves upon activation of an igniter 5, the fixing member 13 is deformed (upper right of the drawing) and the piston is pushed out, but since the fixing member functions to inhibit the backward movement of the piston, the piston is inhibited from returning its initial position after the activation. However, in this structure, fixation of the fixing member itself is complicated, and in the embodiment, the fixing member is fixed between the actuator and a container A accommodating therein the entire actuator. 
   The present invention provides an actuator that is capable of fixing a piston by means of one component before and after activation, and has a simple structure. 
   By using the stopper having the nail portion made of an elastic member, the nail portion operates, similarly to a blade spring, to inhibit the movement of the piston before the ignition device is activated, and to inhibit backward movement of the piston after the ignition device is activated. 
   At least the nail portion of the stopper may be formed of an elastic member, but the entirety of the stopper may be formed from an elastic thin metal sheet. If the entirety of the stopper is formed from an elastic thin metal sheet, a predetermined section of the main body portion may be cut out into, for example, a rectangular, square, trapezoidal, or triangular shape (however, one side of the predetermined section is left uncut and the remaining sides are cut out) and one remaining side may be bent to form the nail portion. 
   By using the stopper having the nail portion made of an elastic member, the nail portion operates, similarly to a blade spring, to inhibit the movement of the piston before the ignition device is activated, and to inhibit backward movement of the piston after the ignition device is activated. 
   At least the nail portion of the stopper may be formed of an elastic member, but the entirety of the stopper may be formed from an elastic thin metal sheet. If the entirety of the stopper is formed from an elastic thin metal sheet, a predetermined section of the main body portion may be cut out into, for example, a rectangular, square, trapezoidal, or triangular shape (however, one side of the predetermined section is left uncut and the remaining sides are cut out) and one remaining side may be bent to form the nail portion. 
   According to the actuator of the present invention, the movement of the piston before activation and the backward movement of the piston after activation are inhibited by one component attached to the cylinder or piston. 
   EMBODIMENTS OF INVENTION 
   (1) Actuator Shown in  FIG. 1 ,  FIG. 2   
     FIG. 1  and  FIG. 2  each are a longitudinal sectional view of an actuator,  FIG. 1  showing a state before activation and  FIG. 2  showing a state after activation. 
   An outer shell of an actuator  10  is formed by integrating an igniter collar  20  and a cylinder  30 . The igniter collar  20  has a main body portion  21  in contact with an igniter  23  and a collar tubular joining portion  22  extended from the main body portion  21 . The cylinder  30  has a tubular piston accommodating portion  31  and a cylinder tubular joining portion  32  protruding from a peripheral surface of the piston accommodating portion  31 . The igniter  23  is fixed to the cylinder tubular joining portion  32  by the igniter collar  20  and thereby connected to the cylinder  30 . 
   The igniter collar  20  and the cylinder  30  are joined to each other in a state in which the cylinder tubular joining portion  32  is inserted into the collar tubular joining portion  22 . There is no particular restriction on the joining method, but in the present embodiment, as shown in the drawings, the cylinder tubular joining portion  32 , which is provided with a step (groove  32   a ) on the outer surface in advance, is covered by the collar tubular joining portion  22 . The collar tubular portion  22  has originally no groove, however, when it covers the cylinder tubular joining portion, it is deformed to match the outer shape of the cylinder tubular joining portion  32 , so that a groove  22   a  having the same shape as a groove  32   a  may be formed, thereby joining both tubular joining portions. It should be noted that the igniter  23  may be fixed to the cylinder tubular joining portion  32  without using the igniter collar  20 . 
   The igniter  23  (the one used in a known actuator or gas generator for an airbag can be used) is fixed within an igniter accommodating space  25  surrounded by the igniter collar  20 , the cylinder main body portion  21  and the cylinder tubular joining portion  32 . 
   The cylinder  30  has at both ends thereof a first opening portion  33  and a second opening portion  34 , and has on a side surface side thereof a communication hole  36  communicated with the igniter accommodating space  25 . 
   In the cylinder main body portion  31 , a step is formed on an inner peripheral surface between the first opening portion  33  and the second opening portion  34 , and an annular surface  37  facing the first opening portion  33  is provided in the step portion. 
   A tubular stopper  40  is attached between the first opening portion  33  of the cylinder main body portion  31  and the annular surface  37 . 
   The tubular stopper  40  has a stopper main body portion  41  that is in contact with the cylinder main body portion  31 , and a nail portion  42  that is obtained by cutting out a desired section of the stopper main body portion  41  into a rectangular shape (however, the three sides are cut out and the one narrow side is left uncut) and bending a leading end portion of the rectangle inward (inside a second piston accommodating space  47 ). It should be noted that the nail portion  42  may be formed by firmly fixing a plate-like object to the main body portion  41 . It is preferred that the nail portion  42  be formed in plurality (two through eight, for example) at regular intervals in a peripheral direction. 
   The stopper  40  or the nail portion  42  is made of an elastic material such as a thin metal sheet of a stainless steel, iron or aluminum or the like. The nail portion  42  performs a predetermined stopper function, similarly to a blade spring, by being deformed when external force is applied thereto and by being restored immediately to its initial shape or a shape similar to the initial shape when the external force is removed. 
   A piston  50  accommodated in the cylinder  30  has, in a desired section in the length direction, a disk-like enlarged diameter portion  51  in which an outer diameter is enlarged. The disk-like enlarged diameter portion  51  has an annular second surface  53  facing the first opening portion  33  and an annular first surface  52  facing the second opening portion  34  side. A peripheral surface  54  of the disk-like enlarged diameter portion  51  abuts on the stopper main body portion  41 , and a part of the annular first surface  52  abuts on the annular surface  37 . The inside of the cylinder  30  is divided into a first piston accommodating space  46  and a second piston accommodating space  47  by the disk-like enlarged diameter portion  51 . 
   Before activation, one end surface  50   a  of the piston  50  faces the first opening portion  33  but does not protrude from the first opening portion  33 . The other end surface  50   b  of the piston  50  protrudes from the second opening portion  34  to the outside. 
   The stopper  40  is fixed by causing one end side opening portion thereof to abut on a stopper fixing member  45  attached to the first opening portion  33  side, an outer peripheral surface of the same to abut on the cylinder main body portion  31 , and a part of an inner peripheral surface of the same to abut on the peripheral surface  54  of the disk-like enlarged diameter portion  51 . The stopper fixing member  45  may have an annular shape and elasticity, and is fixed by bending a peripheral edge  30   a  of the first opening portion  33  inward. 
   The tubular stopper  40  is not required to have a complete tubular shape, and may have a slit  43  passing through vertically (or a slit  43  that does not pass through), as shown in  Fig. 3 . When using the stopper  40  having such a slit  43 , the entirety of the stopper  40  is formed from an elastic member. Then, when such stopper  40  is inserted into the cylinder  30 , the stopper  40  is inserted by pushing it so that the slit  43  is closed, and, when the force of pushing is released after the insertion, the slit  43  is restored to its original state so as to be opened, thus the insertion and fixation to the cylinder  30  can be performed easily. 
   Next, an operation of the actuator of the present invention is described using  FIG. 1  and  FIG. 2 . It should be noted that, before the igniter  23  is activated, a boundary section between the annular second surface  53  and the peripheral surface  54  of the disk-like enlarged portion  51  is pressed by an inner side surface of the nail portion  42 , thus the piston  50  is inhibited from moving in the axial direction. 
   By the activation of the igniter  23 , a combustion product (flame, high-temperature gas, shockwave, or the like) is generated from an ignition portion  24 . The generated combustion product flows into the first piston accommodating space  46  through the igniter accommodating space  25  facing the ignition portion  24  and the communication hole  36 . Then, the annular first surface  52  of the disk-like enlarged diameter portion  51  is pressed by the combustion product, whereby the piston  50  moves in the axial direction. At this moment, the nail portion  42  is pressed toward the main body portion  41  and deformed, thus the movement of the piston  50  is not inhibited. 
   As shown in  FIG. 2 , when the piston  50  protrudes from the first opening portion  33  by a predetermined length, the piston  50  collides with the stopper fixing member  45  and thereby stops, and, at this moment, the nail portion  42  that is deformed in the direction of the main body portion  41  by the movement of the piston  50  returns to its initial shape, and then the leading end portion of the nail portion  42  is caused to abut on the annular first surface  52  and interposed between the annular surface  37  and the annular first surface  52 , whereby the piston  50  is inhibited from being retracted into the cylinder  30 . Moreover, the piston  50  is in a state in which the enlarged diameter portion  51  is sandwiched from both sides thereof by the stopper fixing member  45  and the nail portion  42 , thus the piston  50  does not become shaky, maintaining the state shown in  FIG. 2 . 
   (2) Actuator Shown in  FIG. 4  and  FIG. 5   
     FIG. 4  and  FIG. 5  each are a longitudinal sectional view of an actuator of another embodiment,  FIG. 4  showing a state before activation and  FIG. 5  showing a state after activation. The basic structure of an actuator  100  shown in  FIG. 4  and  FIG. 5  is the same as that of the actuator  10  shown in  FIG. 1  and  FIG. 2 , and the same reference numerals indicate the same components. 
   As shown in  FIG. 4 , a part of the end surface  50   a  side and a part of the end surface  50   b  side of the piston  50  protrude to the outside of the cylinder  30 . 
   A tubular stopper  140  is attached to an outer peripheral surface between the disk-like enlarged diameter portion  51  and the end surface  50   a  of the piston  50 . 
   The tubular stopper  140  has a stopper main body  141  that is in contact with the piston  50 , and a nail portion  142  that is obtained by cutting out a desired section of the stopper main body portion  141  into a rectangular shape (however, the three sides are cut out and the one narrow side is left uncut) and bending a leading end portion of the rectangle outward (inside the second cylinder accommodating space  47 ). It should be noted that the nail portion  142  may be formed by firmly fixing a plate like object to the main body portion  141 . 
   The stopper  140  or the nail portion  142  is made of an elastic material such as a thin metal sheet of a stainless steel, iron or aluminum. The nail portion  142  is deformed, similarly to a blade spring, when external force is applied thereto, and is restored immediately to its initial shape by removing the external force. 
   An annular groove (or a plurality of concave portions)  55  is formed on an outer peripheral surface of the piston  50  between the disk-like enlarged diameter portion  51  and the stopper  140 , and a stopper fixing member  150  for fixing the stopper  140  to the piston  50  is formed at a position on the stopper  140  that faces the annular groove  55 . 
   The stopper main body portion  141  protrudes, along with the piston  50 , from the first opening portion  33  of the cylinder  30  to the outside, and the nail portion  142  is positioned inside the first opening portion  33 . The nail portion  142  spreads wider than the diameter of the first opening portion  33 , and an outer surface of the nail portion  142  abuts on and presses an inner surface of the first opening portion  33 , thus, before the igniter  23  is activated, the piston  50  is inhibited from moving in the axial direction. 
   The stopper fixing member  150  is integrated with the tubular stopper  140 , and has a main body portion  151  of the stopper fixing member, and a nail portion  152  that is obtained by cutting out a desired section of the stopper fixing member main body portion  151  into a rectangular shape (however, the three sides are cut out and the one narrow side is left uncut) and bending a leading end portion of the rectangle toward the inside of the annular groove  55 . The nail portion  152  is tightly fitted in the annular groove  55 , and the tubular stopper  140  is fixed to the piston  50  by means of this nail portion  152 . It should be noted that the tubular stopper  140  may be fixed to the piston  50  by deforming (denting) the tubular stopper  140  to have the same shape as the annular groove  55 , without using the stopper fixing member  150 . 
   The tubular stopper  140  may not have a complete tubular shape, and may have a slit  143  passing through vertically (or a slit  143  that does not pass through), as shown in  FIG. 6 . When using the stopper  140  having such a slit  143 , the entirety of the stopper  140  is formed from an elastic member. Then, when such stopper  140  is inserted into the cylinder  30 , the stopper  140  is inserted by pushing it so that the slit  143  is closed, and, when the force of pushing is released after the insertion, the slit  143  is restored to its original state so as to be opened, thus the insertion and fixation to the cylinder  30  can be performed easily. 
   Next, an operation of the actuator of the present invention is described using  FIG. 4  and  FIG. 5 . It should be noted that, before the igniter  23  is activated, the nail portion  142  spreads wider than the diameter of the first opening portion  33 , thus the piston  50  is inhibited from moving in the axial direction. 
   By the activation of the igniter  23 , a combustion product (flame, high-temperature gas, shockwave, or the like) is generated from the ignition portion  24 . The generated combustion product flows into the first piston accommodating space  46  through the igniter accommodating space  25  facing the ignition portion  24  and the communication hole  36 . Then, the annular first surface  52  of the disk-like enlarged diameter portion  51  is pressed by the combustion product, whereby the piston  50  moves in the axial direction. At this moment, the nail portion  142  is pressed toward the main body portion  141  and deformed, thus the movement of the piston  50  is not inhibited. 
   As shown in  FIG. 5 , when the piston  50  protrudes from the first opening portion  33  by a predetermined length, the nail portion  142 , that is once pressed toward the main body portion  141  and deformed, is restored into its initial shape or a shape similar to the initial shape, thus the nail portion  142  spreads wider than the diameter of the first opening portion  33 . Therefore, the nail portion  142  abuts on an outer side surface  30   a  of the first opening portion  33 , and the piston  50  is inhibited from being retracted into the cylinder  30 . Moreover, even when a force that retracts the piston  50  into the cylinder  30  is applied, the operation of the stopper fixing member  150  prevents the stopper  140  from being dropped from the piston  50 , thus the operation of the stopper  140  for inhibiting the movement of the piston  50  remains unaffected. 
   The invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.