Abstract:
A ball screw with an oil-storage unit, the oil-storage unit includes an oil tank and a connector. The connector has one end formed in the form of a convex or concave structure, and the connecting end of the oil tank is also in the form of a concave or convex structure for engaging with the connector, so as to achieve quick assembling of the connector onto the oil tank through the engagement of the convex and concave structures. Since the oil-storage unit can be quickly replaced after the oil is used up, which provides an automatic and continuous self-lubricating function to the ball screw, and consequently extending the service life of the ball screw.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The instant patent application is a continuation in part of U.S. patent application Ser. No. 12/214,817, filed on Jun. 23, 2008, abandoned on Sept. 27, 2012, and which is a continuation of U.S. patent application Ser. No. 11/091,802, filed on Mar. 28, 2005, and abandoned on Sept. 30, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a ball screw with an oil-storage unit, and more particularly to an oil storage unit which can be quickly assembled onto the ball screw to provide an automatic and continuous self-lubricating function to the ball screw. 
     2. Description of the Prior Art 
     Ball screw is used for motion transmission by taking use of the relative motion between its nut and screw shaft, the movement of the nut is realized by the rolling motion of the rolling elements between the nut and the screw shaft, so that the ball screw has a high efficiency of mechanical transmission. However, if the ball screw has not been lubricated enough for a long period of time, it may result in an increase in friction between the nut and the screw shaft, thus accelerating the abrasion of the ball screw. Hence, self lubricating function of a linear guideway has become more and more important. So far, the self-lubricating methods are generally divided into two types: the first method is to fix the lubricating system at both ends of the nut, lubricating oil is stored in the lubricating system, and then an oil absorbing material is used to smear the lubricating oil to the surface of the screw shaft. Another method is to fix an oil-absorbing material made wiper at either side of the nut, lubricating oil is stored in the oil absorbing material, and the oil absorbing material keeps contacting the surface of the screw shaft, so as to lubricate the teeth of the screw shaft, so that the rolling elements can be lubricated indirectly when rolling through the teeth of the screw shaft. 
     Both of these two methods are to lubricate the teeth of the screw shaft, and then the rolling elements only can be lubricated indirectly by the lubricating oil left on the screw shaft when rolling through the teeth of the screw shaft, therefore, the rolling elements may not be evenly lubricated, and it will cause waste of lubricating oil. In addition, both of the above-mentioned oil absorbing material and the oil-storage unit only can store a small amount of oil, so the lubrication effect will not last for a long time. However, the service life of the linear guideway is 5-10 years or above, as a result, the rail of the linear guideway will be spoiled ahead of its service life time, due to lack of lubrication. On the other hand, it will be time-consuming and difficult when the oil absorbing material and the oil-storage unit are assembled to or disassembled from the sliding block since they are fixed by screwing method. 
       FIG. 14  shows another conventional ball screw  2  with an oil-storage unit  1 , wherein the oil-storage unit  1  is formed with an oil feeding hole  11  in communication with an oil-storage space  12 . A connector  3  formed with an oil feeding hole  301  has one end connected to the nut  201  and another end connected to the oil feeding hole  11  of the oil-storage unit  1 , so that lubricant oil can be transported to the nut  201  by the connector  3 . However, the connector  3  cannot be positioned by itself and needs to be fixed by using a spring  4  to push the end of the connector  3 , and then a screw  5  is used to fix the spring  4 , rendering this oil-storage unit  1  relatively inconvenient to assemble and disassemble. 
       FIG. 15  shows another conventional ball screw shaft  90  on which is movably disposed a reciprocating platform  91 , a motor  93  controlled by a numerical control device  92  rotates the screw shaft  90  so as to cause reciprocating motion of the reciprocating platform  91  with respect to the screw shaft  90 . The method for lubricating the screw shaft  90  is such that the lubricant oil is pumped by a pump  94  from an oil-storage unit  96  to an oil feeding hole  951  of a connecting pipe  95 , and then the lubricant oil drops to an oil receiving hole  901  of the screw shaft  90  to lubricate the screw shaft  90 . The oil-storage unit  96  and the connecting pipe  95  are independent structures from the screw shaft  90  and therefore are inconvenient to assemble and space consuming. Furthermore, the lubricant oil is likely to leak out and cause environmental contamination if the oil-storage unit  96  and the connecting pipe  95  are not well designed and assembled. 
     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a quick-replaceable oil-storage unit for a ball screw, so as to provide an automatic and continuous self-lubricating function to the ball screw. 
     In order to considerably increase the oil storage capacity, making the self-lubricating last longer, and in order to enable the oil-storage unit to be easily assembled on the nut, firstly, the oil tank is designed to have an oil-storage space and a penetrating hole in communication with the oil-storage space. Secondly, the present invention is provided with a connector including a first end, a second end and an oil feeding hole running through the first and second ends. The first end is inserted in the axial direction and into the fixing hole of the nut, the second end is connected to the connecting end of the oil-storage unit, and the oil feeding hole has two ends in communication with the oil-storage space and the fixing hole respectively. The second end of the connector is in the form of a convex structure or a concave structure for engaging with the connecting end of the oil tank, so as to make the oil tank fixed to the connector. 
     Furthermore, in order to enable the oil-storage unit to be easily assembled on the nut, the oil tank is provided with two hooks extending in the axial direction, and the nut is formed on an outer surface thereof with two locking cavities for engaging with the two hooks, so as to achieve quick assembling of the connector onto the oil tank through the engagement of the convex and concave structures. Since the oil-storage unit can be quickly replaced after the oil is used up, which provides an automatic and continuous self-lubricating function to the ball screw, and consequently extending the service life of the ball screw. 
     In considering the independent replaceability of the oil-storage unit, the oil-storage space of the oil tank is designed to be a sealed space in such a manner that the connecting end of the oil tank is sealed with a film, a ball or a spring plug, and the connector is designed to have a convex structure. When the connector is assembled to the oil tank, the film, spring plug, ball can be pierced through or pushed away by the convex structure to let the oil-storage space of the oil tank communicate with the fixing hole of the nut. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a part of a ball screw with an oil-storage unit in accordance with the present invention; 
         FIG. 2  is an exploded view of an oil tank and a connector in accordance with the present invention; 
         FIG. 3  is an illustrative view of a connector in accordance with the present invention; 
         FIG. 3A  is a cross sectional view showing that the connector is connected to the oil tank; 
         FIG. 4A  is an exploded cross sectional view of the connector and the oil tank of the present invention; 
         FIG. 4B  is a cross sectional view showing that the connector and the oil tank of the present invention are assembled together; 
         FIG. 5A  is an exploded cross sectional view of the connector and an oil thank sealed with a film in accordance with the present invention; 
         FIG. 5B  is an assembly cross sectional view showing that the connector is assembled to the oil thank of the present invention; 
         FIG. 6  shows a connector in accordance with a second embodiment of the present invention; 
         FIG. 6A  is a cross sectional view showing that the connector is assembled to the oil tank; 
         FIG. 7  shows a connector in accordance with a third embodiment of the present invention; 
         FIG. 8  shows a connector in accordance with a fourth embodiment of the present invention; 
         FIG. 9A  is an exploded cross sectional view in accordance with the present invention showing a connector and an oil tank which is provided with a spring plug; 
         FIG. 9B  shows that the connector is assembled to the oil tank which is provided with the spring plug; 
         FIG. 10A  is an exploded cross sectional view in accordance with the present invention showing a connector and an oil tank which is provided with a ball; 
         FIG. 10B  shows that the connector is assembled to the oil tank which is provided with the ball; 
         FIG. 11  is an exploded view of an assembled oil tank of the present invention; 
         FIG. 12  shows an integrally formed oil tank of the present invention; 
         FIG. 13  is an assembly view of the present invention showing that two oil tanks are assembled at both ends of the nut; 
         FIG. 14  shows a conventional ball screw with an oil-storage unit; and 
         FIG. 15  shows another conventional ball screw with an oil-storage unit. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be clearer from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 
       FIG. 1  is an exploded view of a part of a ball screw with an oil-storage unit in accordance with the present invention, and  FIG. 2  is an exploded view of an oil tank and a connector in accordance with the present invention. The ball screw with an oil-storage unit in accordance with the present invention comprises a screw shaft  10  and a nut  20 . The screw shaft  10  extends in a direction to form an elongated structure, and the direction in which the screw shaft  10  extends is defined as an axial direction S. The screw shaft is formed on an outer surface thereof with an outer helical groove. The nut  20  is formed with a threaded hole  203  for enabling the nut  20  to be screwed on the screw shaft  10 , and a L-shaped fixing hole  202  (as shown by the dotted line) which is formed at an end surface of the nut  20  and extends in the axial direction S is in communication with the threaded hole  203 . The nut  20  is provided with an oil-storage unit  30  which comprises an oil tank  31  and a connector  32 . The oil tank  31  includes a mounting hole  311 , a gap  312 , a connecting end  313  and an oil-storage space  314  (as shown in  FIGS. 4A ,  4 B). The mounting hole  311  extends in the axial direction S to penetrate the oil tank  31 , and a direction normal to the axial direction S is defined as a radial direction (as indicated by the arrow R). The gap  312  is formed by removing a radial part of the oil tank  31  and is in communication with the mounting hole  311 . The gap  312  has a width larger than an outer diameter of the screw shaft  10 . The connecting end  313  is in the form of a concave structure or a convex structure disposed at an end surface of the oil tank  31  (the connecting end  313  in this embodiment is a concave structure) and formed in the axial direction with a penetrating hole  315  in communication with the oil-storage space  314 . The connector  32  includes a first end  321 , a second end  322  and an oil feeding hole  323  running through the first and second ends  321 ,  322 . The first end  321  is inserted in the axial direction and into the fixing hole  202  of the nut  20 , and the second end  322  is connected to the connecting end  313  of the oil-storage unit  30 . The oil feeding hole  323  has two ends in communication with the oil-storage space  314  and the fixing hole  202 , respectively. By such arrangements, oil can from the oil tank  31  of the oil-storage unit  30  can flow to and lubricate the nut  20  automatically. The oil tank  31  is provided with two first positioning portions  316  extending in the axial direction (the first positioning portions  316  are in the form of a hook in this embodiment). The nut  20  is also formed on the outer surface thereof with two second positioning portions  22  (which are locking cavities in this embodiment, for example) for engaging with the first positioning portions  316 . 
       FIG. 3  is an illustrative view of a connector in accordance with the present invention.  FIG. 3A  is a cross sectional view showing that the connector is connected to the oil tank. The second end  322  of the connector  32  is in the form of a convex structure or a concave structure (in this embodiment, the second end  322  is a convex structure) for engaging with the connecting end  313  of the oil tank  31  (in this embodiment, the connecting end  313  is a concave structure), so as to make the oil tank  31  fixed on the connector  32 . Moreover, the first end  321  of the connector  32  and the fixing hole  202  of the nut  20  can also be in the form of convex and concave structures for engaging with each other (the first end  321  of the connector  32  in this embodiment is a convex structure, for example), so as to fix the connector  32  to the nut  20 . It is to be noted that the connector  32  in this embodiment is made of metal, and the oil tank  31  is made of plastic. Between the first and second ends  321 ,  322  of the connector  32  is formed a flange  324 , and around the first and second ends  321 ,  322  is formed an annular groove  325 ,  326 , respectively. The annular groove  325 ,  326  divides the first and second ends  321 ,  322  into a first part  327  and a second part  328 , respectively, and the first part  327  which is located adjacent to the flange  324  has an outer diameter smaller than that of the second part  328  which is located further away from the flange  324  than the first part  327 . Hence, when the first parts  327  of the first and second ends  321 ,  322  of the connector  32  are inserted in the fixing hole  202  of the nut  20  and the penetrating hole  315  of the oil-storage space  314 , respectively, the second parts  328  of the first and second ends  321 ,  322  can prevent the disengagement of the first parts  327  from the fixing hole  202  of the nut  20  and the penetrating hole  315  of the oil-storage space  314 . 
       FIG. 11  is an exploded view of an assembled oil tank of the present invention, and  FIG. 12  shows an integrally formed oil tank of the present invention. The oil tank  31  of the present invention can be a unitary structure or can be formed by several parts which are bonded together to form the oil tank  31  by ultrasonic bonding, friction bonding, hot melt or glue. 
       FIG. 4A  is an exploded cross sectional view of the connector and the oil tank of the present invention, and  FIG. 4B  is a cross sectional view showing that the connector and the oil tank of the present invention are assembled together. The second part  328  of the second end  322  of the connector  32  which is made of metal and relatively hard can be inserted through the penetrating hole  315  of the relatively soft oil tank  31  which is made of plastic and then locked against the edge of the penetrating hole  315 , so as to fix the connector  32  to the oil tank  31 . 
       FIG. 5A  is an exploded cross sectional view of the connector and an oil thank sealed with a film in accordance with the present invention, and  FIG. 5B  is an assembly cross sectional view showing that the connector is assembled to the oil thank of the present invention. The penetrating hole  315  of the oil tank  31  of the oil-storage unit  30  is sealed with the film  40 . The second end  322  of the connector  32  will pierce through the film  40  when it is inserted in the connecting end  313  of the oil tank  31 , so that the oil feeding hole  323  of the connector  32  is in communication with the oil-storage space  314  of the oil tank  31 . 
       FIG. 6  shows a connector in accordance with a second embodiment of the present invention, and  FIG. 6A  is a cross sectional view showing that the connector is assembled to the oil tank. The second end  322 ′ of the connector  32 ′ is an annular concave structure for mating with the connecting end  313 ′ of the oil tank  31  which is an annular convex structure, so as to fix the oil tank  31  to the connector  32 ′. Or, the second end  322 ′ of the connector  32 ′ can an annular convex structure, while the connecting end  313 ′ of the oil tank  31  can be an annular concave structure. 
       FIG. 7  shows a connector in accordance with a third embodiment of the present invention, wherein the second end  322  of the connector  32  is same as in  FIG. 3  and also in the form of a convex structure for engaging with the connecting end  313  of the oil tank  31  which is in the form of a concave structure. However, the difference is that the first end  321 ′ of the connector  32  in this embodiment is formed with outer threads for mating with inner threads formed in the fixing hole  202  of the nut  20 . By such arrangements, the connector  32  can be fixed to the nut  20 . 
       FIG. 8  shows a connector in accordance with a fourth embodiment of the present invention, wherein the first end  329  of the connector  32  is formed with outer threads for mating with inner threads of the fixing hole  202  of the nut  20 , so as to fix the connector  32  to the nut  20 . The second end  330  of the connector  32  of this embodiment is a tubular convex structure formed with a flange  331 , and around the periphery of the second end  330  is formed a plurality of notches  332  (there are two notches  332  in this embodiment) for allowing oil to flow out. The first end  329  of the connector  32  can be screwed with the nut  20 , and the second end  330  in the form of a tubular convex structure can be inserted in the penetrating hole  315  of the connecting end  313  of the oil tank  31 , so as to provide quick connection through the engagement of the convex and concave structures. 
       FIG. 9A  is an exploded cross sectional view in accordance with the present invention showing a connector and an oil tank which is provided with a spring plug and  FIG. 9B  shows that the connector is assembled to the oil tank which is provided with the spring plug. The penetrating hole  315  of the oil tank  31  of the oil-storage unit  30  is sealed with the spring plug  41 . When the second end  330  of the connector  32  is inserted in the connecting end  313  of the oil tank  31 , it will push the spring plug  41  away, so that the oil feeding hole  323  (as shown in  FIG. 8 ) of the connector  32  is in communication with the oil-storage space  314  of the oil tank  31 . 
       FIG. 10A  is an exploded cross sectional view in accordance with the present invention showing a connector and an oil tank which is provided with a ball and  FIG. 10B  shows that the connector is assembled to the oil tank which is provided with the ball. The penetrating hole  315  of the oil tank  31  of the oil-storage unit  30  is sealed with the ball  42 . When the connector  32  is assembled to the oil tank  31 , the second end  322  of the connector  32  will push the ball  42  away, so that the penetrating hole  315  of the oil tank  31  will be in communication with the oil feeding hole  323  of the connector  32 . 
       FIG. 13  is an assembly view of the present invention showing that two oil tanks are assembled at both ends of the nut, wherein the screw shaft  10  is formed with outer threads, and the nut  20  is screwed on the screw shaft  10 . The nut  20  is provided with two oil-storage units  30  which are assembled at both ends of the nut  20 . The nut  20  is provided with a plurality of hooks  21  arranged in annular fashion, or the nut  20  can be provided with two opposite hooks  21 . 
     For easy observation, the oil tank  31  of the oil-storage unit  30  can be made of transparent or semi-transparent material, so that the oil level in the oil tank  31  is visible and it can also be observed whether the film  40 , spring plug  41 , ball  42  have been pierced through or pushed away to let the oil-storage space  314  of the oil tank  31  communicate with the fixing hole  202  of the nut  20 . 
     It is to be noted that, as shown in  FIG. 1 , in addition to the fact that the fixing of the connector  32  to the oil tank  31  is achieved by the concave and convex engagement of the second end  322  of the connector  32  with the connecting end  313  of the oil tank  31 , the two first positioning portions  316  on the oil tank  31  can also be engaged with two second positioning portions  22  of the nut  20  to enhance the reliability of the fixing between the connector  32  and the oil tank  31 . Moreover, the oil tank  31  can be easily removed from the nut  20  by disengaging the first positioning portions  316  from the second positioning portions  22 . 
     While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.