Abstract:
A worktable for an apparatus for grinding recesses, having on a frame ( 3 ) a pair of pulleys carrying a grinding belt ( 2 ), is provided with a sole control member ( 19 ) to approach and move apart said workpiece vice ( 20 ) with respect to said shaping pulley ( 1 ) of said pair of pulleys.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a worktable for an apparatus for grinding recesses. 
   The apparatus for grinding recesses, which reference is made to in the following description, is a hand operated machine, also called notching machine, that is adapted for recessing, by grinding, in ends of tubular workpieces. This apparatus has a pair of pulleys carrying a grinding belt: one of the pulleys is a driving pulley for the grinding belt, and the other pulley is a shaping pulley co-operating with the grinding belt to shape recesses. A vice for clamping a pipe to be worked is located near the shaping pulley and is movable according to a movement towards and away from the shaping pulley, to allow a pipe, that is clamped by the vice, to be ground. 
   In order to achieve such a movement in prior art apparatuses for grinding recesses, the vice for clamping pipe is mounted rotatable on a worktable in such a position with respect to the shaping pulley that the axis of the shaping pulley and the axis of the pipe to be worked form a desired angle in a generally horizontal plane that is defined by the same axes. Usually, said angle can be changed between 90 and 30 degrees. The worktable, that is generally constituted by a pair of slides sliding on mutually orthogonal axes, has a feeding movement with respect to the shaping pulley that is obtained through two orthogonal movements and is controlled by generally manual feed means along such orthogonal axes, one of which is parallel to the axis of the shaping pulley. 
   These feed means comprise prismatic guides, that are usually made by a pair of parallel cylindrical sections co-operating with correspondent through holes that are made in the slides of the worktable, and parts in mutually orthogonal movement are each operated by wheels, worm screws or rack-and-pinion gears, or other, that are controlled through handwheels or lever-operated links. 
   In any case, the operation along one direction of the one slide in the worktable is independent of the operation of the other slide in the other direction, at right angles to the first direction. Therefore, it happens that an operator performs a recess in a tubolar workpiece by simply approaching the tubolar workpiece to the grinding belt, usually in a central position thereof widthwise. Of course, the grinding belt will be worn unevenly and its life will be reduced consequently. 
   Now, an operator careful to prolong the life of a grinding belt must act cunningly so that the grinding of a recess is performed throughout the width of the belt, while the belt runs endless on the two pulleys of the apparatus. This should require a great diligence of the operator. 
   The present invention aims at overcoming the above mentioned drawbacks. 
   SUMMARY OF THE INVENTION 
   In particular, an object of the present invention is to permit each workpiece to be worked automatically throughout the width of a grinding belt so that the wear of all its surface is uniform, which can prolong the life of the grinding belt. 
   Another object of the invention is to reduce the labour of an operator at the grinding apparatus, the operator having to act on a sole control means to perform a notching. 
   This object is achieved by the present invention through a worktable for an apparatus for grinding recesses having on a frame a pair of pulleys carrying a grinding belt moving endless along a lengthwise axis of said frame, the worktable supporting a workpiece vice that is pivoted around an orthogonal pivoting axis on its first slide and can be set in its angular position with respect to a shaping pulley of said pair of pulleys, characterized in that the worktable is provided with a sole control member to approach and move apart said workpiece vice with respect to said shaping pulley. 
   As a result of the sole operating control, a recess is ground in a tubolar workpiece end using the entire width of the grinding belt. The distribution of the heat produced when the workpiece is worked is extended to all the surface of the grinding belt, and this feature, together with the uniform use of the grinding belt, brings about an increase of its life. 
   Advantageously, such a working performed on the end of a tubolar workpiece, by virtue of the combined movement of lengthwise feeding toward the grinding belt and transversal traverse with respect to the same grinding belt, permits a high finishing degree to be obtained on the workpiece, as the burr produced during the working is greatly reduced, also for the better distribution of the heat on the grinding belt than before. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described below with reference to two embodiments thereof with connection to the enclosed drawings, in which: 
       FIG. 1  is a perspective view of a first embodiment of a worktable according to the present invention as applied to an apparatus for grinding recesses that is shown only partially; 
       FIG. 2  is a top view of the first embodiment of a worktable as shown in  FIG. 1 ; 
       FIG. 3  is a front view of the first embodiment of a worktable as shown in  FIG. 1 ; 
       FIG. 4  is a perspective view of a second embodiment of a worktable according to the present invention as applied to an apparatus for grinding recesses that is shown only partially; 
       FIG. 5  is a top view of the second embodiment of a worktable; 
       FIG. 6  is a front view in reduced scale of the second embodiment of a worktable as shown in  FIG. 5 ; 
       FIG. 7  is a right hand side view in reduced scale of the second embodiment of a worktable as shown in  FIG. 5 ; 
       FIG. 8  is a perspective view of a modified second embodiment of a worktable; 
       FIG. 9  is a top view of the worktable in  FIG. 8 ; and 
       FIG. 10  is a fragmentary bottom view of the longitudinal slide of the worktable in FIG.  8 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First with reference to  FIGS. 1  to  3 , an apparatus for grinding recesses is shown therein only with respect to its shaping pulley  1  having an axis x and on which a grinding belt  2  runs, and to a portion of frame  3  thereof, which is supported by a pedestal  4  (FIG.  3 ). A worktable according to a first embodiment of the present invention, that is designed in general as  6 , is sustained by a depressed portion  5  of the frame  3 . 
   Pivoted to the depressed portion  5  of the frame  3  by means of a pin  7  is a platform  8 , that is bent into a U shape in opposite vertical walls  9 ,  10 . The platform  8 , that is revolving around the pin  7 , can be set in its angular position through its axis y at right angles to the vertical walls  9 ,  10  with respect to the lengthwise direction of movement of the grinding belt  2 , that is indicated by the arrow N in  FIG. 2 , i.e. with respect to the axis x of the shaping pulley  1 . The platform  8  can be set by introducing a check pin  11  into through holes, that are made in the revolving platform  8  and are designated generally as  12 , and into through holes  13  that are made in the frame  3 . The purpose of setting the platform  8  will be described below. 
   Two cylindrical sliding guides  15  for a slide  16  are connected to the vertical walls  9 ,  10  of the platform  8  by means of screws  14 . As it is usual, the slide  16  has correspondent through holes  17  engaging the cylindrical guides  15 . Also a shaft  18 , provided with a handwheel  19 , is disposed on the vertical walls  9 ,  10  of the platform  8 . The handwheel  19  is the manual control member of movement of the slide  16  on the cylindrical guides  15 . The connection between the shaft  18  and the slide  16  is not explained below, as it is conventional. 
   A vice  20  for a workpiece is mounted revolving on the slide  16 . Conventionally, the workpiece vice  20  has a base  21 , which is provided with a slot  22  in the form of a circle arch and a securing screw  23  adapt to be fixed to the slide  16 , for setting the angular position of the workpiece vice  20  with respect to the direction N of movement of the grinding belt  2 . 
   From foregoing one can understand that, differently from the prior art, the manual control is performed through a sole control member, i.e. the handwheel  19 . The angle α is the angle between the axis y along which the slide  16  slides, at right angles to the walls  9 ,  10  of the platform  8 , and the axis x of the shaping pulley  1  (FIG.  2 ). According to the present invention this angle α is selected on the grounds of the depth of the recess to be performed on the end of the tubolar workpiece, considering that, in order to obtain a uniform wear of the grinding belt  2 , the grinding operation must be performed throughout the width L of the same grinding belt  2 . Of course, the depth of the recess in turn depends on a diameter D of a tubolar workpiece (not shown) and on an inclination of the last one with respect to the grinding belt. 
   It should be understood easily that, for a recess throughout the entire diameter D of a tubolar workpiece, e.g. a recess having its axis that is at right angles to the axis of the tubolar workpiece, the size of the angle α must be selected so that the cathetus opposite to the angle α in a right-angle triangle, having as other cathetus the width L of the grinding belt  2 , is of size D/2. Such an angle α must be set by means of the check pin  11  introduced concentrically into a hole  12  of the platform  8  and the suitable hole  13  of the frame  3 . 
   In the above mentioned example of a recess having its axis at right angles to the axis of the tubolar workpiece, the workpiece vice  20  must be retained with such an inclination that the axis of the tubolar workpiece coincides with the direction of the arrow N of movement of the grinding belt  2 , i. e. it is at right angles to the axis x of the shaping pulley  1 . On the contrary, when one wants perform a recess having its axis inclined by a set angle to the axis of the tubolar workpiece, he must incline the workpiece vice  20  by the same set angle by means of the slot  22  and the securing screw  23 . 
   Now, with reference to  FIG. 4 , in which same or similar numerals are used to designate the same parts or similar to those described with reference to  FIGS. 1  to  3 , an apparatus for grinding recesses is shown therein only with respect to its shaping pulley  1  having an axis x, shaping pulley on which a grinding belt  2  runs, and to a portion of frame  3  thereof. A worktable  60  according to a second embodiment of the present invention is sustained by a depressed portion  5  of the frame  3 . 
   The worktable  60  is depicted, as detached from the apparatus in the  FIGS. 5  to  7 , that are a top view and vertical side views respectively, of the same. 
   The worktable  60  comprises a platform  80  that is fixed to the depressed portion  5  of the frame  3  by means of screws  81  (FIG.  4 ). The fixed platform  80  has opposite vertical walls  90 ,  100 . Two cylindrical sliding guides  150  for a transverse slide  160 , moving forward parallel to the axis x of the shaping pulley  1 , are connected to the opposite vertical walls  90 ,  100  by screws  140 . Under the fixed platform  80 , an operation device of known lever type, that is indicated in general as  190 , is located that constitutes the manual control member of movement of the transverse slide  160  on the cylindrical guides  150 . 
   A movable platform  181  is connected to the transverse slide  160 . On the movable platform  181  there are cylindrical sliding guides  151  for a lengthwise slide  161 , having an approaching stroke and a moving away stroke with respect to a shaping pulley  1  along a lengthwise direction N of movement of the grinding belt  2 . A workpiece vice  20  is mounted revolving on the lengthwise slide  161 . As in the first embodiment, the workpiece vice  20  has a base  21 , which is provided with a slot  22  in the form of a circle arch and a securing screw  23  to the lengthwise slide  161 , for setting the angular position of the workpiece vice  20  with respect to the direction N of movement of the grinding belt  2 . 
   Further, the lengthwise slide  161  is constrained to a straight linear cam  30  that can swing in its angle, coplanar to the parallel sliding planes of the transverse and lengthwise slides  160 ,  161 . 
   The swinging straight linear cam  30  is formed by a channel  31  that is pivoted at right angles on the fixed platform  80  of the worktable  60  by means of a rotation pin  32  (FIG.  4 ). As shown in  FIG. 5 , the channel  31  has off-centre a setting pin  33  that is received into a circle arch-shaped slot  34  of the fixed platform  80  to be locked in the desired position by a locking lever  39 . 
   As shown in  FIG. 4 , the cam follower of the linear cam  30  is a sliding roller  35  in the channel  31 . The sliding roller  35  is connected to the lengthwise slide  161  by means of a screw  36  and an arm  37 . The arm  37  is preferably lightened by a through slot  38 , in order to permit the roller  35  to be fixed in such a way that the linear cam  30  can be set without any obstacle throughout the slot  34 . 
   The operation of the second embodiment of worktable is similar to that of the first embodiment described with reference to  FIGS. 1  to  3 . 
   In this second embodiment, the angle α is the angle between the sliding axis y in the linear cam  30  and the axis x of the shaping pulley  1 . The angle α is selected analogously to the first embodiment. 
   In grinding a recess in a tubolar workpiece, once the linear cam  30  has been adjusted according to the desired angle relevant to the diameter to be worked, it is enough to operate the sole lever control member  190 , to displace the transverse slide  160  throughout the width of the grinding belt  2 . In the same time, the lengthwise slide  161 , by virtue of the linear cam  30 , will move forward against the shaping pulley  1  to perform the desired grinding. 
   With reference to  FIGS. 8  to  10 , there is shown a modified second embodiment of the worktable according to the present invention. This modified embodiment is particularly developed to work workpieces of large diameter, in which the amount of lengthwise feeding of the workpiece vice is great, since this amount can reach the measure of the radius of the same workpieces. 
   In  FIGS. 8  to  10  same or similar numeral references are used to designate same parts or similar to those in  FIGS. 4  to  7 . 
   As a result of the great lengthwise feeding of the worktable, a swinging straight linear cam  300  must be set on a platform  800  so that an angle β of inclination between the axis of this linear cam  300  and the direction of lengthwise feeding. For this purpose a second circle arch-shaped slot designed as  134  is used. This slot  134  works like the slot  34  of the fixed platform  80  and then is described no longer. 
   In this modified second embodiment, the lever operation device to manually control the forward movement of the transverse slide  160  on the cylindrical guides  150 , that is located under the platform  80 , either is not comfortably usable or cannot be used because of great counteracting forces produced by the sliding on the cam that is substantially orthogonal to the operation of the transverse slide. 
   For this reason it is suitable to perform the control for feeding the workpiece vice directly on its slide provided with lengthwise traverse, i.e. by acting substantially directly in the same direction of the sliding roller  35  in the channel  31  of the linear cam  30 . The sliding roller  35  is connected to the lengthwise slide  161  by means of a screw  36  and an arm  370 . The arm  370  is preferably provided with an open slot  380  so that the roller  35  is fixed easier. 
   In this modified second embodiment it is the lengthwise slide  161  to be directly operated by an auxiliary lever  191  as shown in  FIG. 10 , that is a bottom view taken from the movable platform  181  of the lengthwise slide  161 . The auxiliary lever  191  is pivoted removably near a front corner  182  of the movable platform  181  opposite to the operation side of the lengthwise slide  161 . Suitably, the lengthwise slide  161  is provided at the bottom with a pin  183  designed to engage an open shaped slot  184  that is made intermediately in the auxiliary lever  191 . 
   In operation, once the lever  190  has been disconnected, when the auxiliary lever  191  is operated through its handle  185  according to a double-pointed arrow F until it is moved to its position  191 ′ (shown by a dotted line), the lengthwise slide  161  is moved forward to  161 ′ being displaced also transversally on the transverse slide  160  by virtue of the engagement with the linear cam  300 , and the vice  20  is brought to  20 ′. 
   The invention can be modified without departing from its scope. For example, in the described embodiments, the operation control has been described as a handwheel or a lever. Of course, these manual controls can be servocontrolled or powered as conventionally, for example through a pneumatic circuit.