Patent Publication Number: US-11391306-B2

Title: Linear actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-035823 filed on Mar. 3, 2020, the contents all of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a linear actuator that reciprocates a slide table along the axial direction of a cylinder body. 
     Description of the Related Art 
     Conventionally, as a means for transporting a workpiece or the like, for example, a linear actuator, such as a fluid pressure cylinder, has been used under the action of supplying a pressure fluid. The present applicant has proposed, as disclosed in Japanese Patent No. 3795968, a linear actuator that can transport a workpiece placed on a slide table by reciprocating the slide table linearly along a cylinder body. 
     SUMMARY OF THE INVENTION 
     The general object of the present invention is to provide a linear actuator capable of smooth operation by preventing accumulation of dust and dirt in an environment where dust and dirt such as powder dust are scattered. 
     An aspect of the invention resides in a linear actuator including: a cylinder body containing therein a cylinder chamber to which a pressure fluid is supplied; a slide table configured to be movable along the longitudinal direction of the cylinder body; a cylinder mechanism having a piston arranged in the cylinder chamber and configured to be movable along the cylinder chamber; and a guide mechanism attached to the cylinder body and configured to guide the slide table along the longitudinal direction of the cylinder body under the rolling action of a plurality of rolling elements circulating a passage, the linear actuator being configured to reciprocate the slide table relative to the cylinder body under the moving action of the piston, wherein: the slide table includes a main body extending in the longitudinal direction of the cylinder body, and an end part arranged substantially orthogonal to the main body so as to face an end portion of the cylinder body in the longitudinal direction; and the end part is configured to have a storage portion that is opened on an end surface, of the end part, that faces the cylinder body, the storage portion extending in the longitudinal direction, the storage portion being configured to store dust and dirt therein. 
     According to the present invention, the slide table of the linear actuator is configured of the main body extending along the longitudinal direction of the cylinder body and the end part arranged substantially orthogonally to the main body so as to face the longitudinal end of the cylinder body. The end part has the storage portion that is opened on an end surface, of the end part, that faces the cylinder body on which the slide table is movably provided, the storage portion extending in the longitudinal direction and being configured to store dust and dirt therein. 
     Accordingly, even when the linear actuator is used in an environment where powder dust and the like is scattered and, for example, dust (solidified matter) of a mixture of powder dust and a lubricant for lubricating the rolling elements forming the guide mechanism is produced around the longitudinal end of the guide mechanism facing the end part, the produced dust can be suitably collected in the storage chamber when the end part of the slide table is moved to the cylinder body side. 
     As a result, even when the linear actuator is used in an environment where powder dust and the like is scattered and solidified dust including powder dust and the like builds up, the dust is stored in the storage portion that is opened on the end face of the end part, whereby it is possible to prevent the end part from coming into contact with the accumulated dust when the slide table is being moved, hence the slide table can operate smoothly in the longitudinal direction even under the above environment. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external perspective view of a linear actuator according to the first embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the linear actuator shown in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of a guide mechanism in the linear actuator shown in  FIG. 1 ; 
         FIG. 4  is an overall plan view of the linear actuator shown in  FIG. 1 ; 
         FIG. 5  is a sectional view taken along a V-V line in  FIG. 4 ; 
         FIG. 6  is a sectional view taken along a VI-VI line of  FIG. 5 ; 
         FIG. 7  is a front view of the linear actuator shown in  FIG. 1  as viewed from the end plate side; 
         FIG. 8  is a partial sectional plan view taken along a line VIII-VIII in  FIG. 7 ; 
         FIG. 9  is a plan view of a linear actuator according to a second embodiment of the present invention; 
         FIG. 10  is a front view of the linear actuator shown in  FIG. 9  as viewed from the end plate side; 
         FIG. 11  is a partial sectional plan view taken along a XI-XI line in  FIG. 10 ; 
         FIG. 12  is an external perspective view of a linear actuator according to a third embodiment of the present invention; 
         FIG. 13  is a front view of the linear actuator shown in  FIG. 12  as viewed from the end plate side; 
         FIG. 14  is a partial sectional plan view taken along a XIV-XIV line in  FIG. 13 ; 
         FIG. 15  is an external perspective view showing the case where a cover member is attached to the end plate of the linear actuator of  FIG. 12 ; 
         FIG. 16  is a front view of the linear actuator shown in  FIG. 15  as viewed from the end plate side; 
         FIG. 17  is a partial sectional plan view taken along a line XVII-XVII of  FIG. 16 ; 
         FIG. 18  is an external perspective view of a linear actuator according to a fourth embodiment of the present invention; 
         FIG. 19  is an overall plan view of the linear actuator shown in  FIG. 18 ; 
         FIG. 20  is a front view of the linear actuator shown in  FIG. 18  as viewed from the end plate side; 
         FIG. 21  is a partial sectional plan view taken along a XXI-XXI line of  FIG. 20 ; 
         FIG. 22  is an external perspective view showing the case where a cover member is attached to the end plate of the linear actuator of  FIG. 18 ; and 
         FIG. 23A  is a front view of the linear actuator shown in  FIG. 22  as viewed from the end plate side, and  FIG. 23B  is an enlarged side view of the linear actuator of  FIG. 23A  as viewed from the side. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 1 to 6 , a linear actuator  10  includes a cylinder body  12 , a slide table  14  that reciprocates linearly in the longitudinal direction (indicated by arrows A 1  and A 2 ) of the cylinder body  12 , and a guide mechanism  18  arranged between the cylinder body  12  and the slide table  14  and held by the cylinder body  12  via a pair of pins  16 . 
     A depressed portion  20  extending in the longitudinal direction (indicated by arrows A 1  and A 2 ) is formed on the top face of the cylinder body  12 , and a pair of pin insertion holes  22  into which the pins  16  are inserted are formed in the depressed portion  20  so as to be spaced a predetermined distance from each other in the longitudinal direction. Further, the depressed portion  20  includes a pair of attachment holes  24  for attaching the guide mechanism  18  to the cylinder body  12 , and the holes  24  are formed so as to penetrate through the depressed portion  20  at positions close to the pin insertion holes  22  (see  FIGS. 2 and 3 ). 
     The cylinder body  12  includes, on one side surface thereof, two sensor mounting grooves  26  extending along the longitudinal direction (indicated by arrows A 1  and A 2 ), and unillustrated sensors are mounted to the mounting grooves  26 . Additionally, the cylinder body  12  further includes a stroke adjustor  28 , which is provided on the other side surface thereof, which is opposite to the one side surface, and the stroke adjustor  28  limits movement of the slide table  14  by abutment of a stopper block  92 , which will be described later. 
     As shown in  FIGS. 1, 2 and 4 , the stroke adjustor  28  includes a block body  30 , a stud bolt  34  screwed into the holes of the block body  30  and fixed to the block body  30  via a nut  32 , and a damper member  36  mounted at one longitudinal end of the stud bolt  34 . Then, in the stroke adjustor  28 , the stud bolt  34  is turned with respect to the block body  30  to advance or retreat in the longitudinal direction (in the direction of arrow A 1  or A 2 ), so as to adjust the amount of movement of the slide table  14  in the longitudinal direction. 
     Also, inside the cylinder body  12 , as shown in  FIGS. 2 ,  3 ,  5  and  6 , a pair of through holes  38  extending in the longitudinal direction (indicated by arrows A 1  and A 2 ) are formed. The through holes  38  have a circular cross section with substantially the same diameter. The through holes  38  are spaced from each other in the width direction (indicated by arrow B direction) that is orthogonal to the longitudinal direction, so as to extend in parallel with each other. 
     As shown in  FIG. 6 , each through hole  38  contains thereinside a piston  44  having a piston packing  40  and a magnetic body  42  mounted on the outer peripheral surface thereof and a piston rod  46  connected to the piston  44 . A floating bush  50  is coupled to the opposite longitudinal end of the piston rod  46  by a screw member  48 . 
     Further, each through hole  38  is closed at one longitudinal end (which will be referred to as the first longitudinal end) by an end cap  52  that is inserted into the hole and locked by a snap ring  54 . Also, a ring body  56  and a collar member  58  are inserted into the through hole  38  at the other longitudinal end (which will be referred to as the second longitudinal end) and locked by the snap ring  54  in the longitudinal direction, so as to close the through hole  38 . 
     An O-ring  60  is mounted into an annular groove of the outer peripheral surface of the collar member  58  so as to abut against the inner peripheral surface of the through hole  38  while a rod hole  62   a  penetrates through the center of the collar member  58  so as to allow the piston rod  46  to be inserted along the longitudinal direction. A rod packing  64  is mounted into an annular groove of the inner peripheral surface of the collar member. This rod packing  64  is made of an elastic material, and is in sliding contact with the outer peripheral surface of the piston rod  46  to thereby establish sealing. 
     On the other hand, the ring body  56  is provided on the second longitudinal end side (on the arrow A 2  side) of the collar member  58 . The ring body  56  includes therein a rod hole  62   b  penetrating therethrough in the longitudinal direction, and the piston rod  46  is inserted into the rod hole  62   b . A lubrication ring  66  and a dustproof ring  68  are provided in respective annular grooves of the inner peripheral surface of the rod hole  62   b . The dustproof ring  68  is arranged so as to be on the second longitudinal end side (the arrow A 2  side) of the through hole  38 , whereas the lubrication ring  66  is arranged on the first longitudinal end side (the arrow A 1  side) of the dustproof ring  68 . 
     The lubrication ring  66  is formed in an annular shape and made of a flexible and compressible material impregnated with a lubricant such as grease. The lubrication ring  66  is put in sliding contact with the outer peripheral surface of the piston rod  46 . Similarly to the lubrication ring  66 , the dustproof ring  68  is formed in an annular shape and made of a flexible and compressible material. The dustproof ring  68  is not impregnated with a lubricant and is used in a dry state. 
     Further, by closing the first and second ends of each through hole  38  with the end cap  52  and the collar member  58 , respectively, a pair of cylinder chambers  70  accommodating the piston  44  and the piston rod  46  are configured. One cylinder chamber  70  and the other cylinder chamber  70  are connected to (i.e., communicate with) each other via a pair of communication passages  72  extending in the width direction (in the direction of arrow B). 
     Further, a pair of first and second fluid ports  74 ,  76  are formed on the second end side surface of the cylinder body  12 , and the first and second fluid ports  74 ,  76  are each connected to communicate with one of the cylinder chambers  70 . The first fluid port  74  is arranged on the first longitudinal end side of the cylinder body  12  (on the arrow A 1  side), and the second fluid port  76  is arranged on the second longitudinal end side of the cylinder body  12  (on the arrow A 2  side). 
     That is, the piston  44  and the piston rod  46  described above function as a cylinder mechanism that can be moved in the longitudinal direction by the supplying action of the pressure fluid to the cylinder chamber  70 . 
     As shown in  FIGS. 1 to 8 , the slide table  14  is formed of a table body (main body)  78  extending in the longitudinal direction (indicated by arrows A 1  and A 2 ) and an end plate (end part)  80  fixed to the second longitudinal end of the table body  78  so as to be orthogonal to the longitudinal direction of the table body. The table body  78  and the end plate  80  are fastened to each other using a pair of bolts  82  in such a state that they are orthogonal to each other forming a substantially L-shaped cross section. That is, the end plate  80  is formed so as to extend in the vertical direction with respect to the table body  78  extending in the horizontal direction. 
     The table body  78  is formed in a substantially U-shaped cross section, having a pair of guide portions  86  protruding toward the cylinder body  12  (downward) from both ends in the width direction thereof. The guide portions  86  are formed to extend in the longitudinal direction (in the direction of arrows A 1  and A 2 ), and have respective ball rolling grooves  88  extending in the longitudinal direction on the respective inner wall surfaces of the guide portions  86  facing each other (see  FIGS. 5 and 6 ). Further, four workpiece holding holes  90  are formed in the top surface of the table body  78 . Here, the number of workpiece holding holes  90  is not limited to four, and is appropriately set according to the stroke amount of the slide table  14 , for example. 
     Further, a stopper block  92  is fixed to one side surface of the table body  78  so as to project in the width direction of the table body, so that the stopper block  92  moves integrally with the slide table  14  and faces toward the stroke adjustor  28  provided on the cylinder body  12 . When the slide table  14  including the table body  78  moves in the longitudinal direction relative to the cylinder body  12 , the stopper block  92  comes into contact with the damper member  36  of the stroke adjustor  28 , so that the movement of the slide table  14  in the longitudinal direction is restricted. 
     The end plate  80  is a plate member having a rectangular cross section elongated in the width direction of the slide table (in the direction of arrow B) and a constant thickness in the longitudinal direction of the slide table. Floating bushes  50  are held by substantially semicircular holes  84  formed in the lower part of the end plate. Further, as shown in  FIGS. 6 and 8 , the end plate  80  includes a storage chamber (storage portion)  94  having a predetermined volume, which is formed in an surface (one end surface in the longitudinal direction)  80   a  of the end plate  80  that faces toward the table body  78  (the arrow A 1  direction). 
     This storage chamber  94  is formed with a hollow having a predetermined depth, formed by recessing the end surface  80   a  of the end plate  80  in the direction away from the table body  78  (in the direction of arrow A 2 ), and the storage chamber  94  is formed in a position facing the guide mechanism  18 . That is, the storage chamber  94  is at least formed such that its width (the length in the direction of arrow B) is equal to or greater than the width of the guide block  96  while its height is equal to or greater than the height of the guide block  96 . 
     The width and height of the storage chamber  94  are not limited to the cases corresponding to the width and height of the guide block  96  of the guide mechanism  18  as described above, and may have any sizes as long as the storage chamber  94  is formed in a larger shape than the sectional shape of the guide block  96  when viewed from the longitudinal direction. 
     As shown in  FIGS. 2, 3, 5, and 6 , the guide mechanism  18  includes a guide block  96  which is flattened in the width direction (the direction of arrow B), a set of ball return members  98 , cover blocks  100  and scrapers  102 , which are arranged on both longitudinal ends of the guide block  96 , and a pair of pins  16  for positioning and holding the guide block  96  with respect to the cylinder body  12 . The cover block  100  is formed with semicircular ball return grooves  106  that each circulate bearing balls (rolling elements of a ball bearing)  104  in cooperation with the ball return members  98 . 
     Further, a first dustproof plate  108  is held between the cover block  100  and the scraper  102 . The first dustproof plate  108  is formed into a plate shape and made of, for example, a flexible and compressible material. The first dustproof plate  108  is provided such that its upper surface is in sliding contact with the inner surface of the table body  78  of the slide table  14  and its both ends in the width direction (the direction of arrow B) is in sliding contact with the guide portions  86  of the slide table  14 . Further, the scraper  102  is arranged so as to have a slight clearance with respect to the ball rolling grooves  88  or so as to be in sliding contact with the ball rolling grooves  88 , so that powder dust and the like are prevented from entering the guide mechanism  18 . 
     Additionally, a pair of ball rolling grooves  110  extending in the longitudinal direction (the direction of arrows A 1  and A 2 ) are formed on both sides of the guide block  96  in the width direction while a pair of ball circulating holes  112  that penetrate through the guide block  96  in the longitudinal direction are formed on an inner side, in the width direction, than the respective ball rolling grooves  110  so as to be spaced a predetermined interval from each other. Thus, the ball rolling groove  88  of the guide portion  86  in the slide table  14 , the ball rolling groove  110  in the guide block  96 , the ball circulating hole  112 , and the ball return groove  106  of the cover block  100  constitute a ball circulation passage that enables circulation of bearing balls  104 . 
     Further, on each of both side surfaces of the guide block  96 , a pair of second dustproof plates  114   a ,  114   b  are provided respectively at top and bottom of the ball rolling groove  110 . The second dustproof plates  114   a ,  114   b  are formed of, for example, a flexible and compressible material elongated in a in the longitudinal direction of the guide block. The second dustproof plates  114   a ,  114   b  are fixed to each of both side surfaces of the guide block  96  so as to be sliding contact with the guide portions  86  of the slide table  14 . 
     In the thus configured guide mechanism  18 , the multiple bearing balls  104  roll along the ball circulation passage, so that the slide table  14  provided so as to cover the guide mechanism  18  is supported so as to reciprocate in the longitudinal direction (the direction of arrows A 1  and A 2 ) relative to the guide block  96 . Further, since the second dustproof plates  114   a  and  114   b  are in sliding contact with the guide portion  86  of the slide table  14 , the dust and dirt that have entered in between the guide portion  86  and the guide block  96  are prevented from entering the ball rolling grooves  88  and  110 . 
     Further, the guide block  96  has, formed on a bottom surface thereof, pin insertion holes (not shown) for receiving a pair of pins  16 , the pin insertion holes being arranged at a predetermined interval. The guide block  96  also has a pair of threaded fixing bolt holes  118  formed at portions close to the pin insertion holes, and the bolt holes  118  penetrate through the guide block  96  (see  FIG. 5 ). In this arrangement, as shown in  FIG. 5 , fixing bolts  120  are inserted from below into the attachment holes  24  of the cylinder body  12 , and screw-engaged into the fixing bolt holes  118  of the guide block  96 , whereby the guide mechanism  18  including the guide block  96  is fixed to the top surface (depressed portion  20 ) of the cylinder body  12 . 
     The linear actuator  10  according to the first embodiment of the present invention is essentially configured as described above, and its operation, action and effect will be described next. Herein, a state in which the piston  44  shown in  FIG. 6  is located on the first longitudinal end side (on the arrow A 1  side) will be referred to as the initial position. 
     First, the pressure fluid is supplied to the first fluid port  74  from an unillustrated fluid pressure supply source while the second fluid port  76  is opened to the atmosphere by a switching operation of an unillustrated switching device. 
     Since the pressure fluid from the first fluid port  74  is also supplied from one cylinder chamber  70  to the other cylinder chamber  70  through the communication passages  72 , the paired pistons  44  are pushed toward the second longitudinal end (in the direction of arrow A 2 ), and the pistons  44  together with the piston rods  46  move to the second longitudinal end side. The floating bushes  50  coupled with the piston rods  46  press the end plate  80  to the second longitudinal end side (in the direction of arrow A 2 ). As a result, the slide table  14  including the end plate  80  moves to the second longitudinal end side (in the direction of arrow A 2 ) relative to the guide mechanism  18  under the rolling action of the bearing balls  104  circulating along the ball circulation passage. 
     In the process of moving the slide table  14 , the stopper block  92  comes into contact with the damper member  36  of the stroke adjustor  28 , so that further movement in the longitudinal direction is restricted and the movement ends at that point (i.e., end position). 
     On the other hand, when the slide table  14  is moved to the first longitudinal end side (in the direction of arrow A 1 ) opposite to the above, the pressure fluid is supplied to the second fluid port  76  while the first fluid port  74  is opened to the atmosphere. In this state, the pistons  44  are pressed and moved to the first longitudinal end side (in the direction of arrow A 1 ) by the pressure fluid supplied to the cylinder chamber  70 . With the movement of the pistons  44 , the end plate  80  and the slide table  14  move to the first longitudinal end side (in the direction of arrow A 1 ), and the end plate  80  comes into contact with the second longitudinal end of the slide table  14 , and returns to the initial position shown in  FIG. 1 . 
     Next, description will be given concerning a case where the above-described linear actuator  10  is used in an environment where powder dust and the like is scattered in the atmosphere. 
     In this environment, when powder dust and the like scattered in the atmosphere adhere to the surfaces of the cylinder body  12  and the slide table  14  of the linear actuator  10  while the linear actuator  10  is driven, the powder dust and the like also adhere to the surface of the piston rods  46  exposed to the outside from the through holes  38  of the cylinder body  12 . 
     The powder dust and the like thus adhering to the piston rods  46  are suitably scraped off by the dustproof rings  68  arranged on the outermost side during the pulling operation of the piston rods  46  into the cylinder body  12 , so that entry of the dust and the like into the cylinder chamber  70  can be reliably prevented. 
     Further, lubricant is supplied to the outer peripheral surface of the piston rod  46  by the lubrication ring  66  provided on an inner side than the dustproof ring  68  (on the arrow A 1  side), and as a result, the piston rod  46  can be smoothly moved along the longitudinal direction. In addition, the dustproof ring  68  suitably prevents leakage of the lubricant applied to the piston rod  46  to the outside (to the arrow A 2  side). 
     Further, the first dustproof plate  108  provided on the guide mechanism  18  is in sliding contact with the inner surface of each of the guide portions  86  in the slide table  14 , so that it is possible to prevent the powder dust and the like entering in between the second longitudinal end of the guide block  96  and the end plate  80  of the slide table  14 , from entering the ball return groove  106  and the ball rolling grooves  88 ,  110 . Additionally, the upper surface of the first dustproof plate  108  is in sliding contact with the undersurface of the table body  78 , so that it is possible to prevent the powder dust and the like adhering to the undersurface from entering the guide mechanism  18 . Further, the scraper  102  is provided such that a slight gap is formed between the scraper  102  and the ball rolling groove  88 , or such that the scraper  102  is in sliding contact with the ball rolling groove  88 , so that it is possible to prevent powder dust and the like from entering the guide mechanism  18 . 
     Furthermore, the second dustproof plates  114   a  and  114   b  provided on respective both side surfaces of the guide mechanism  18  prevent powder dust and the like from entering the ball rolling grooves  88  and  110  from the first end and the second end in the longitudinal direction of the guide portion  86 . At the same time, powder dust and the like are prevented from invading the ball rolling grooves  88  and  110  from the slide table  14  side and the lower side of the cylinder body  12 . Therefore, adhesion of powder dust and the like to the bearing balls  104  is reliably prevented. 
     Moreover, in the ball circulation passage formed by the guide mechanism  18  and the slide table  14 , multiple bearing balls  104  circulate in a state of being lubricated with a lubricant such as grease, and the lubricant and powder dust and the like, for example, mingle together and may solidify into a solidified matter of dust. Detailedly, the solidified matter may be produced around the widthwise ends of the guide block  96  that hold the bearing balls  104  in a circulatory manner and face the guide portions  86 . 
     Since the end plate  80  has the storage chamber  94  that is opened on the end surface  80   a , of the end plate  80 , on the first longitudinal end side and faces the second longitudinal end of the guide block  96 , when the slide table  14  is moved to the first longitudinal end side (to the arrow A 1  side) relative to the cylinder body  12  in the case where the solidified matter has arisen in the above way, the solidified matter generated around the second longitudinal end can be appropriately pushed into the storage chamber  94 . Therefore, when the slide table  14  is moved to the first longitudinal end side (in the direction of arrow A 1 ), the solidified matter adhering to and accumulated on the guide block  96  is prevented from coming into contact with the end surface  80   a  on the first longitudinal end side of the end plate  80 , and hence it is possible to prevent longitudinal movement of the slide table  14  from being hindered. 
     That is, even when the linear actuator  10  is used in an environment where powder dust and the like are scattered, solidified matter, for example, generated near the second longitudinal end of the guide mechanism  18  can be stored in the storage chamber  94 . 
     As described above, in the first embodiment, the slide table  14  of the linear actuator  10  includes the table body  78  provided above and parallel to the cylinder body  12 , and the end plate  80  joined to the second longitudinal end of the table body  78  so as to be orthogonal to the longitudinal direction of the table body  78 . The end plate  80  has the storage chamber  94  that is opened so as to face the guide mechanism  18  fixed to the cylinder body  12  and is depressed in the direction (in the direction of arrow A 2 ) away from the guide mechanism  18 . 
     Therefore, even if the linear actuator  10  is used in an environment where powder dust and the like are scattered, and for example, the lubricant for lubricating the bearing balls  104  in the guide mechanism  18  is mingled with the powder dust and the like to thereby generate a solidified matter, it is possible to aptly store, in the storage chamber  94 , the solidified matter adhering to and accumulated around the guide mechanism  18  when the end plate  80  of slide table  14  moves to the guide mechanism  18  side (in the direction of arrow A 1 ). 
     As a result, even when the linear actuator  10  is used in an environment where powder dust and the like are scattered and resultantly a solidified matter is generated, the solidified matter adhering to the vicinity of the second longitudinal end of the guide mechanism  18  is stored inside the storage chamber  94 , whereby it is possible to avoid a situation where the end plate  80  comes into contact with the solidified matter to consequently hinder operation of the end plate  80  under the moving action of the slide table  14 . Thus, even in the above environment, the slide table  14  constituting the linear actuator  10  can be smoothly operated along the longitudinal direction. 
     Further, since the storage chamber  94  is formed to have substantially the same cross-sectional shape as, or a cross-sectional shape larger than, that of the guide mechanism  18  when viewed from the longitudinal direction of the linear actuator  10 , the solidified matter generated near the second longitudinal end of the guide mechanism  18  can be reliably stored inside the storage chamber  94 . 
     Further, by appropriately setting the depth of the storage chamber  94  along the longitudinal direction, it is possible to adjust the volume for the solidified matter to be stored, as desired. 
     Furthermore, since the first dustproof plate  108  is provided in the second longitudinal end of the guide mechanism  18 , it is possible to prevent the powder dust and the like that has entered in between the guide block  96  and the end plate  80  of the slide table  14 , from entering the ball return grooves  106  and the ball rolling grooves  88  and  110 . Also, sliding contact of the first dustproof plate  108  with the undersurface of the table body  78  can prevent powder dust and the like adhering to the undersurface from invading the guide mechanism  18  side. 
     Further, in the guide mechanism  18 , a pair of second dustproof plates  114   a  and  114   b  are provided on each of the side surfaces in the width direction. Therefore, the second dustproof plates  114   a  and  114   b  prevent powder dust and the like from entering the ball rolling grooves  88  and  110  from the first and second longitudinal ends of the guide block  96 , and also from the slide table  14  side and the lower side of the cylinder body  12 . As a result, it is possible to reliably prevent powder dust and the like from entering in between the slide table  14  and the guide mechanism  18  and adhering to the bearing balls  104 , thus preventing operation failures of the linear actuator  10  due to invasion of powder dust and the like. 
     Further, in the cylinder body  12 , provision of the annular dustproof ring  68  in the rod hole  62   b  of the ring body  56  makes it possible to reliably scrape off the powder dust and the like adhering to the outer peripheral surface of the piston rod  46  exposed to the outside of the cylinder body  12  when the piston rod  46  is pulled in, and hence prevent entry of the dust and the like into the cylinder chamber  70 . 
     Next, a linear actuator  150  according to the second embodiment is shown in  FIGS. 9 to 11 . The same components as those of the linear actuator  10  according to the first embodiment described above are allotted with the same reference numerals, and detailed description thereof will be omitted. 
     The linear actuator  150  according to the second embodiment is different from the linear actuator  10  according to the first embodiment in that a pair of work holes  156   a  and  156   b  opened upward of an end plate  154  in the slide table  152  are provided. 
     As shown in  FIGS. 9 to 11 , the linear actuator  150  is formed with a pair of work holes  156   a  and  156   b  formed in the end plate  154  of the slide table  152  so as to extend in the height direction (in the direction of arrow C). 
     The work holes  156   a  and  156   b  are formed in the end plate  154  connected to the table body  78 , for example, on an end surface  154   a  facing the second longitudinal end, and the work holes are spaced a predetermined interval from each other in the width direction (the direction of arrow B). Each of the work holes  156   a  and  156   b  is formed so as to have a rectangular cross section and penetrate in a straight line from the upper surface of the end plate  154  to the storage chamber  94  formed inside. That is, in the slide table  152 , the storage chamber  94  communicates with the outside through a pair of work holes  156   a  and  156   b . The numbers, positions, etc. of the work holes  156   a  and  156   b  are not limited to the above-described configuration, and may be appropriately adapted as necessary. 
     When the linear actuator  150  described above is used in an environment where powder dust and the like is scattered, and for example, a solidified matter formed of a mixture of the powder dust and the like and the lubricant for lubricating the bearing balls  104  in the guide mechanism  18  is stored in the storage chamber  94 , an unillustrated operator jets compressed air into the interior through the pair of work holes  156   a  and  156   b . Thus, the interior of the storage chamber  94  is pressurized under the supplying action of the compressed air, so that the accumulated solidified matter can be discharged to the outside from the opening of the storage chamber  94  on the end surface  154   a  facing the second longitudinal end. Instead of using compressed air, it is also possible to insert a rod-shaped member into the work holes  156   a  and  156   b  to push out the solidified matter accumulated in the storage chamber  94 . 
     Therefore, the solidified matter stored in the storage chamber  94  can be readily and reliably discharged to the outside through the work holes  156   a  and  156   b  without removing or moving the slide table  152 , thereby improving the maintainability. 
     Next, a linear actuator  160  according to the third embodiment is shown in  FIGS. 12 to 17 . The same components as those of the linear actuator  10  according to the first embodiment described above are allotted with the same reference numerals, and detailed description thereof will be omitted. 
     The linear actuator  160  according to the third embodiment is different from the linear actuator  10  according to the first embodiment in that a storage chamber (storage portion)  166  formed in an end plate  164  of a slide table  162  is formed to penetrate through the end plate in the thickness direction (lengthwise direction, the direction of arrows A 1  and A 2 ). 
     As shown in  FIGS. 12 to 14 , the linear actuator  160  includes the storage chamber  166  in the end plate  164  constituting the slide table  162 . The storage chamber  166 , which has, for example, a constant cross-sectional shape, is formed so as to penetrate through the end plate  164  in the thickness direction of the end plate, i.e., in the longitudinal direction of the slide table  162  (the direction of arrows A 1  and A 2 ). That is, the storage chamber  166  is opened on the end surface  164   a  of the end plate  164  at the second longitudinal end side. 
     In this configuration, when the linear actuator  160  described above is used in an environment where powder dust and the like is scattered, and a solidified matter formed of a mixture of the powder dust and the like and the lubricant is stored in the storage chamber  166 , for example, an unillustrated operator can readily and surely take out the solidified matter from the opened portion (opening), designated at  168 , of the storage chamber  166 , which is open toward the second longitudinal end side (the direction of arrow A 2 ). Accordingly, it is no longer necessary to remove or move the slide table  162 , thus making it possible to improve the maintainability. 
     Further, since the storage chamber  166  is opened on the end surface  164   a  of the end plate  164  at the second longitudinal end side, the solidified matter is gradually pushed toward the storage chamber  166  from the guide mechanism  18  side and accumulated therein, and then the solidified matter is pushed out from the opened portion  168  and discharged from the end plate  164 . That is, since work for removing the solidified matter in the storage chamber  166  is not required, the maintainability can be further improved. 
     Further, as shown in  FIGS. 15 to 17 , a cover member  170  for covering the opened portion  168  of the storage chamber  166  may be provided on the end surface  164   a  on the second longitudinal end side of the end plate  164 . The cover member  170  is formed into a plate shape larger than the cross-sectional area of the opening of the storage chamber  166 , for example, and is fastened, at four corners thereof, to the end surface  164   a  on the second longitudinal end side with cover fixing bolts  172 , to cover the opened portion  168  of the storage chamber  166 . That is, the cover member  170  is detachably attached to the end plate  164 . 
     In the thus configured linear actuator  160 , by setting the cover member  170  to the end plate  164  in a normal use state, it is possible to prevent powder dust and the like from entering the inside through the opened portion  168  of the storage chamber  166 . On the other hand, when the solidified matter accumulated in the storage chamber  166  is removed, the cover fixing bolts  172  are unfastened so as to detach the cover member  170  from the end plate  164  and remove the solidified matter from the opened storage chamber  166 . After completion of the work, the cover member  170  is attached again to cover the opened portion. 
     Finally,  FIGS. 18 to 21  show a linear actuator  180  according to the fourth embodiment. The same components as those of the linear actuator  160  according to the third embodiment described above are allotted with the same reference numerals, and detailed description thereof will be omitted. 
     The linear actuator  180  according to the fourth embodiment differs from the linear actuator  160  according to the third embodiment in that, in the slide table  102 , a storage chamber (storage portion)  184  penetrating in the thickness direction (the direction of arrows A 1  and A 2 ) is provided, and an end plate  186  has a pair of work holes  188   a  and  188   b.    
     As shown in  FIGS. 18 to 21 , the linear actuator  180  includes the storage chamber  184  formed in the end plate  186  of the slide table  182 . The storage chamber  184  penetrates through the end plate  186  in the thickness direction of the end plate, i.e., in the longitudinal direction of the slide table  182  (the direction of arrows A 1  and A 2 ) so as to have a constant cross section. Further, the end plate  186  is formed with a pair of work holes  188   a  and  188   b  extending in the height direction (in the direction of arrow C) from the upper surface thereof toward the storage chamber  184  to communicate with the storage chamber  184 . 
     When the thus configured linear actuator  180  is used in an environment in which powder dust and the like are scattered, and a solidified matter generated by mixing the powder dust and the like with lubricant is stored in the storage chamber  184 , for example, an unillustrated operator can easily and surely take out the solidified matter from an opened portion  190  of the storage chamber  184  which is opened toward the second longitudinal end side (to the direction of arrow A 2 ). Further, by supplying a compressed air to the storage chamber  184  through the work holes  188   a  and  188   b , the solidified matter accumulated inside the storage chamber  184  can be more smoothly discharged from the front to the outside. 
     As a result, the solidified matter in the storage chamber  184  can be removed through the opened portion  190 , and also by using a compressed air supplied from the work holes  188   a  and  188   b , the maintainability for removing the solidified matter can be greatly improved. 
     Further, as shown in  FIGS. 22 to 23B , a cover member  192  for covering the opened portion  190  of the storage chamber  184  and the work holes  188   a ,  188   b  all together may be provided on the end plate  186 . 
     The cover member  192  is, for example, formed of a first lid portion  194  that covers the opened portion  190  of the storage chamber  184  and a second lid portion  196  extending from the upper end of the first lid portion  194  perpendicularly to the first lid portion  194 , so as to form an L-shaped cross section as a whole. The cover member  192  is attached to the end plate  186  by fastening the four corners of the first lid portion  194  to an end surface  186   a  of the end plate  186  on the second longitudinal end side with cover fixing bolts  198 , whereby the first lid portion  194  covers the opened portion  190  of the storage chamber  184  while the second lid portion  196  abuts the top surface of the end plate  186  to cover the paired work holes  188   a  and  188   b.    
     Thus, in this linear actuator  180 , by setting the cover member  192  to the end plate  186  in a normal use state, it is possible to prevent powder dust and the like from entering the inside through the opened portion  190  of the storage chamber  184 , as well as through the work holes  188   a  and  188   b.    
     On the other hand, when the solidified matter accumulated in the storage chamber  184  is removed, the cover fixing bolts  198  are unfastened to thereby detach the cover member  192  and the solidified matter is then removed through the opened portion  190  of the storage chamber  184 . After completion of the work, the cover member  192  is set again to cover them, so that it is possible to suitably prevent powder dust and the like from entering the linear actuator through the opened portion  190  of the storage chamber  184  and the work holes  188   a  and  188   b.    
     It should be noted that the linear actuator according to the present invention is not limited to the above-described embodiments, and of course, various configurations can be adopted without departing from the gist of the present invention.