Abstract:
A pitting knife assembly including a pitting knife mount and a pulley drive assembly coupled and configured to move the knife mount around a circular or substantially circular path, and a fruit pitting apparatus including such an assembly. During operation of the pitting knife assembly with at least one pitting knife mounted to the knife mount and a fruit conveying assembly positioned to convey fruit to the pitting knife assembly, the pitting knife can produce pitted fruit by moving into engagement with fruit conveyed by the conveying assembly (to pit the fruit) as the knife mount moves through a first portion of the path, and the pitting knife can then move out of engagement with (and away from) the pitted fruit as the knife mount moves through a second portion of the path.

Description:
FIELD OF THE INVENTION 
     The invention pertains to an apparatus for removing pits from prunes or other fruit (e.g., dates). In some embodiments, the inventive apparatus is configured to translate prunes (or other fruit) seated in holders to a set of pitting knives, and includes a pulley assembly configured to drive the knives around a circular (or other) closed path into (and then out of) engagement with fruit in the holders. 
     BACKGROUND OF THE INVENTION 
     Herein, the expression that an object (e.g., a pitting knife or pitting knife assembly) moves or is moved “around” a closed path (e.g., a circular or substantially circular path) denotes that the object&#39;s center of gravity moves or is moved around the closed path. When the object is rigid, and the object moves or is moved “around” a closed path, each element of the object (e.g., the tip of each pitting knife of a rigid pitting knife assembly) moves or is moved around the closed path. 
     Throughout this disclosure, including in the claims, the expression “pulley” is used in a broad sense to denote a wheel for transmitting power and/or changing the direction of motion. Thus, a wheel having a rim (e.g., a grooved, flat, or slightly convex rim) configured to translate a belt as the wheel rotates, is one type of pulley. Examples of pulleys of this type are depicted in several of the figures (e.g,  FIG. 14  which shows pulleys  304  and  315 ). Another example of a “pulley” as used herein is a gear (having teeth around its rim) of a knife drive assembly, where the gear is coupled and configured to translate a pitting knife mount around a closed path (e.g., an at least substantially circular path) as the gear rotates, or to cause a subassembly of the knife drive assembly (said subassembly including a pitting knife mount and typically also other pulleys) to translate a pitting knife mount around a closed path as the gear rotates. 
     Throughout this disclosure, including in the claims, the expression “pulley drive assembly” is used in a broad sense to denote a drive assembly including at least one pulley (e.g., pulleys which translate belts, or pulleys which are gears). 
     The term “box cam” is used throughout the specification to denote a cam that includes at least one cam track capable of causing a cam follower engaged therewith to execute reciprocating motion as the box cam rotates. The term “reciprocating motion” denotes cyclical motion including motion in a first direction (at one moment of the cycle) and motion in the direction opposite the first direction (at another moment of the cycle). Thus, an open cam (mounted on a shaft) is not a box cam if the open cam can drive a cam follower downward but not upward during a complete rotation of the open cam about the axis of the shaft (typically, an externally supplied spring force is required to drive the cam follower upward). 
     In some systems for pitting prunes (or other fruit), a pitting knife drive assembly drives pitting knives (sometimes referred to as “punches” or “pushers”) in reciprocating fashion along a linear (vertical) path, and fruit conveying assembly moves the fruit to be pitted into the knives&#39; path and moves the pitted fruit out of engagement with the knives. Typically, in each cycle of operation of such an knife drive assembly, a mechanism moves the knives vertically upward and compresses a spring, and then (when fruit to be pitted has been positioned below the knives) the mechanism releases the knives to allow the spring to drive them vertically downward into engagement with the fruit. U.S. Pat. No. 3,618,648 (issued Nov. 9, 1971) for example, describes such a system. 
     U.S. Pat. No. 4,485,732 (issued Dec. 4, 1984) also discloses a pitting knife drive assembly which drives pitting knives in reciprocating fashion along a linear (vertical) path. In each cycle of operation of this assembly, a mechanism translates the knives vertically upward, and then (when fruit to be pitted has been positioned below the knives) the mechanism forces the knives vertically downward into engagement with the fruit. 
     It has also been proposed to include an open cam or box cam in a pitting knife drive assembly to move pitting knives around a two-dimensional, closed loop path into and out of engagement with fruit to be pitted. For example, U.S. Pat. No. 5,870,949 (issued Feb. 16, 1999 and assigned to the assignee of the present invention) describes such use of an open cam in a pitting knife drive assembly, and both U.S. Pat. No. 5,619,912 (issued Apr. 15, 1997 and assigned to the assignee of the present invention) and U.S. Pat. No. 5,870,949 describe such use of a box cam in a pitting knife drive assembly. 
     However, conventional use of a box cam (or open cam) mechanism in a pitting knife drive assembly to move pitting knives around a two-dimensional, closed loop path into and out of engagement with fruit to be pitted has several limitations and disadvantages, including the following: 
     there is a gap between each roller (each of the cam followers of the rocker arm assembly coupled to the knife assembly) and the box cam, which increases with wear and is amplified by the stroke arm distance to the pitting knives. This gap can cause a violent bang during the down stroke direction change and abnormal wear in the cam followers and box cam; 
     the cam followers roll and slide on a non lubricated box cam surface, and thus add friction load to the system; 
     the plunger shafts (to which the pitting knives are attached) have linear bearings that add sliding friction to the load and additional gap distance with wear, and also have linear bushings which add to the sliding friction load; 
     the reciprocating eccentric motion of the knife drive assembly requires use of many (e.g., ten) rotating bushings thus adding to the sliding friction load; 
     the speed of the box (or open) cam is limited due to the banging of the cam action; 
     the box (or open) cam system is very loud during operation; 
     the box (or open) cam assembly has lubricated parts, and particulates from its wearing parts may fall directly into the final product; and 
     due to the shock and vibration of the box (or open) cam assembly, many parts thereof have a short life. 
     U.S. Pat. No. 5,870,949 describes a fruit pitting apparatus including a fruit conveying assembly suitable for use in typical embodiments of the inventive apparatus. We next describe this fruit conveying assembly with reference to  FIGS. 1 ,  2 ,  2 A, and  3 - 7 . 
     A conventional knife drive assembly (including a box cam) of the type described in U.S. Pat. No. 5,870,949 will be described with reference to FIGS.  4  and  8 - 10 . This conventional knife drive assembly can be mounted within pitting head housing  22  of  FIGS. 1-7  or in another fruit pitting apparatus. In accordance with the present invention, an embodiment of the inventive knife drive assembly would replace the conventional knife drive assembly in a fruit pitting apparatus (e.g., as shown in  FIG. 15 ). 
       FIG. 1  is a simplified side elevational view (partially cut away) of a conventional prune pitting apparatus.  FIG. 2  is a cross-sectional view of the  FIG. 1  apparatus taken along line  2 - 2  of  FIG. 1 . The pitting apparatus of  FIG. 1  includes a frame (with sideplates  12  and  12 A, legs  17 , and pitting head housing  22 ), pulley  32 B, sprockets  32 C, sprocket assembly  32 D, disks  34 , and two conveyor chains  35  looped around sprocket assemblies  32 C and  32 D and disks  34 . Each of elements  32 B,  32 C and  32 D is rotatably mounted to the frame. The drive mechanism comprises motor  24 , speed reducer  26 , pulley  23 ′ (attached to a first shaft mounted for rotation relative to housing  22 ), pulleys  21 B and  11 B and sprocket  59  (attached to a second shaft mounted for rotation relative to housing  22 ), drive belt  28  looped around pulleys  23 ′ and  11 B, and drive belt  30  looped around pulley  21 B and pulley  32 B. In operation, motor  24  and speed reducer  26  cause pulley  23 ′ to rotate clockwise (in  FIG. 1 ), causing belt  28  to rotate pulleys  21 B and  11 B clockwise and causing belt  30  to rotate pulley  32 B clockwise. Rotating pulley  32 B and sprockets  32 C drive each of the conveyor chains  35  clockwise around a loop defined by sprocket assemblies  32 C and  32 D and disks  34 . One of the chain loops is in the plane of  FIG. 1 , and the other chain loop is in a vertical plane parallel to the plane of  FIG. 1 . More specifically, as shown in  FIG. 4 , pulley  32 B and sprockets  32 C are connected to shaft  32 A. As belt  30  rotates pulley  32 B, pulley  32 B in turn rotates shaft  32 A and sprockets  32 C together as a unit, thereby driving chains  35  (each chain  35  being looped around one of sprockets  32 C). 
     Fruit holders  36  (shown in  FIG. 2 ) are connected between conveyor chains  35 , so that the fruit holders  36  are conveyed around the loop as chains  35  are driven. A roller carrier  54  is attached at one end of each holder  36 , and a roller carrier  56  is attached at the holder&#39;s other end. A roller  66  is attached to each carrier  54 , and a roller  68  is attached to each carrier  56 . Each fruit holder includes four pocket members  58  and four pocket members  60 , which define four adjustable pockets (each pocket being dimensioned to hold firmly one of the prunes or other articles to be pitted when the pocket is in a closed configuration). Variable-length rods  50  extend between carriers  54  and  56 , and a spring  62  is provided between holder  36  and each of carriers  54  and  56  to spring-load the rods into their maximum-length configuration (in which members  58  and  60  are oriented so as to hold the pockets in an open configuration). Members  58  and  60  are pivotably mounted to rods  50  so that when rods  50  are compressed by action of cams  84  (mounted along sideplates  12  and  12 A) on rollers  66  and  68 , the members  58  and  60  pivot to decrease the size of (i.e., close) the pockets. When cams  80  allow springs  62  to move rods  50  to their elongated configuration, members  58  and  60  pivot in the opposite direction to increase the size of (i.e., open) the pockets. 
       FIG. 3  is a cross-sectional view of the  FIG. 2  apparatus (with roller  68  omitted for clarity), taken along line  3 - 3  of  FIG. 2 , showing one of paddle wheels  38  sweeping across the pockets of a fruit holder  36 . As shown in  FIGS. 2 and 3 , cams  80  are separated by a relative large distance, so that the pockets defined by fruit holders  36  are open when holders  36  translate past cams  80 . Cams  84  are separated by a smaller distance so that the pockets defined by holders  36  are closed when holders  36  translate past cams  84 . A third pair of cams (cams  85  and  85 A, shown in  FIGS. 4 and 5  but not in  FIG. 1  or  2 ) is also mounted to sideplates  12  and  12 A in pitting head housing  22  to perform pocket opening and closing functions within housing  22 . A fourth pair of cams (cam bars  111 , one of which is shown in  FIG. 1 ) is also mounted to side plates  12  and  12 A between paddle wheels  38  and pitting head housing  22  to perform pocket opening and closing functions (to be described below). Cams  80  are mounted in positions in which they cause the pockets to open when holders  36  translate past hopper  14  (to allow the pockets to receive prunes or other articles). Cams  84  are mounted in positions in which they cause the pockets to close when holders  36  translate past paddle wheels  38 . Cams  85  and  85 A are mounted in positions in which they cause the pockets to close as holders  36  approach pitting knives within housing  22 , and then to open briefly immediately after the pit removal operation (while the pitting knives remain engaged with the fruit in holders  36 ), and then to close again as holders  36  continue to move through housing  22  after the pit removal operation. 
     Cams  85  and  85 A are preferably notched cam tracks, each having an input end  89  and a notch  85 B as shown in  FIG. 7 . Such notched implementations of cam tracks  85  and  85 A are mounted so that each holder  36  translates between input ends  89  before the pitting step, and then translates between notches  85 B after the pitting step. Since there are two rows of pitting knives  102  which simultaneously pit fruit in two holders  36 , one holder of each such pair of holders translates between the notches  85 B immediately after the pitting step, and the second holder of each pair translates between notches  85 B only after the first holder has done so. Typically, roller  66  at one end of each holder  36  is offset (in the direction in which holder  36  translates) from roller  68  at the other end of the holder  36 . 
       FIG. 7  shows cam track  85 A and half of each of several holders  36  (it should be understood that cam track  85  is symmetrically mounted on the other side of center line L of  FIG. 7 , and that each holder  36  has four adjustable pockets, each adjustable pocket defined by a pair of spring-loaded pocket members  58  and  60 ). When a holder  36  enters pitting head housing  22 , it initially translates past the aligned input ends  89  of cam tracks  85  and  85 A (as is the top holder  36  in  FIG. 7 ). Since the distance between tracks  85  and  85 A at input ends  89  is relatively large, each spring  62 , mounted between the main body of holder  36  and carrier  54  (or  56 ) at the end of holder  36  to spring-load the pockets into their open configuration, is relaxed in its elongated configuration (and rods  50  extending between carriers  54  and  56  are elongated) when the holder translates past the input ends  89 . Thus, the holder&#39;s pockets are in their open configuration (as are the pockets of the top holder  36  in  FIG. 7 ). 
     Then, when each holder  36  advances between cam tracks  85  and  85 A past the input ends  89 , the separation between the cam tracks decreases, and so the action of the cam tracks on carriers  54  and  56  shortens rods  50  (and compresses springs  62 ) to move the pockets into their closed configuration (as are the pockets of the second holder  36  from the bottom of  FIG. 7 ). In this state, the pitting knives engage the fruit gripped in the pockets to eject the pits from the fruit. 
     Then, when each holder  36  advances between the notched portions  85 B of cam tracks  85  and  85 A, the separation between the cam tracks increases, and springs  62  relax into their elongated state, thus lengthening the rods  50  and moving the pockets into their open configuration (as are the pockets of the bottom holder  36  shown in  FIG. 7 ). The notched portions  85 A are sized and positioned so that the pockets open briefly after the pit removal operation (while the pitting knives remain engaged with the fruit in the pockets) to improve the efficiency with which the knives are withdrawn from the fruit and the pitted fruit flesh is separated from the pockets, and the pockets then close as holders  36  continue to move along tracks  85  and  85 A past notches  85 B. When multiple rows of pitting knives simultaneously pit fruit in two or more holders  36 , these holders sequentially translate past notches  85 B but all do so while the pitting knives remain engaged with the pitted fruit carried by them (to improve the efficiency with which the pitted fruit flesh is separated from each of the holders carrying said flesh). 
     With reference again to  FIG. 4 , cams  80  are typically attached to the frame by adjustable mounts  82  so that the distance between cams  80  can be adjusted when desired (e.g., between processing of a batch of prunes of one average size and processing of another batch of prunes of a different average size). Similarly, cams  84  are attached to the frame by adjustable mounts  86 , and cams  85  and  85 A are attached to the frame by adjustable mounts  37  (shown in  FIG. 4 ). 
     Hopper  14  (having sideplates  16  and endwall  10 ) of  FIG. 1  is positioned so that the prunes, dates, or similar soft fruit to be pitted (e.g., prunes P shown in  FIGS. 1 and 2 ) drop onto holders  36  as the holders pass under hopper  14 . The  FIG. 1  apparatus also includes hood  20  (which is supported above the upper end of hopper  14  and typically houses a water spray system for spraying water on the fruit translating past it) and paddle wheels  38 . Paddle wheels  38  are rotatably mounted within hood  20 , and are typically driven (by means not shown) to rotate sufficiently rapidly about their central axes (which are perpendicular to the plane of  FIG. 1 ) so that the paddles of each wheel  38  sweep several times across each holder  36  as the holders  36  translate past the wheels  38 . As indicated in  FIG. 3 , each time one of the paddles of wheel  38  sweeps across the pockets of a holder  36 , protruding portions  78  of the paddle sweep through corresponding recesses  76  of the holder  36 . Thus, paddle wheels  38  sweep out of the pockets any prunes (or other articles) that are not firmly seated (typically in a vertical orientation) between a pair of pocket members  58  and  60 . 
     Each holder  36  has a lower plate  46  in which a pitting cup  70  is mounted at the location of each pocket (holder  36  shown in  FIG. 3  has four cups  70 , one at the location of each pocket). Pitting cups  70  are sometimes referred to as pitting rubbers, since they are typically made of rubber. Each cup  70  has a pit ejection opening  72  extending through it. Each holder  36  also has an upper plate  44  with a funnel-shaped opening  74  at the location of each pocket (for guiding an article into the pocket so as to rest on cup  70  between members  58  and  60 ). As shown in  FIG. 3 , one of conveyor chains  35  is attached to one side of plate  46  of each holder  36 , and the other of chains  35  is attached to the other side of such plate  46 . 
     In operation, prunes P (or dates or other articles to be pitted) fall from hopper  14  onto cups  70 , as the conveyor translates holders  36  past the hopper, so that a prune (or other article) is loaded into each of at least some of the pockets defined by holders  36 . The prunes (within holders  36 ) then translate past paddle wheels  38 , and then through cam assembly  111  (shown schematically in  FIG. 1 ). Assembly  111  comprises a pair of cam tracks  111 A and  111 B (also referred to herein as shaker bars), best shown in  FIG. 2A . 
     Shaker bars  111 A and  111 B are cam tracks similar to above-described cam tracks  84 , but each of bars  111 A and  111 B has periodically varying width and thus defines a scalloped (or other periodically varying) cam surface, whereas each cam  84  has uniform width (away from its ends) and thus defines a straight cam surface. Shaker bars  111 A and  111 B are mounted to sideplates  12  and  12 A in positions in which they cause the pockets of each holder  36  to open and close rapidly and periodically as holders  36  translate past the shaker bars (i.e., as roller  66  of each holder  36  follows the cam surface of bar  111 A and roller  68  of each holder  36  follows the cam surface of bar  111 B). This periodic opening and closing of the pockets causes the articles to be pitted to settle completely into the pockets. 
     Assembly  111  also includes means for adjustably attaching shaker bars  111 A and  111 B to sideplates  12  and  12 A of the frame. For example, adjustable mounts  186  (shown in  FIG. 2A ) can be provided, so that the distance between bars  111 A and  111 B can be adjusted when desired (e.g., in the same circumstances, described above, in which mounts  82  are adjusted to vary the spacing of cams  80 ). Alternatively, each of bars  111 A and  111 B is mounted to a plate (or angled bracket), and each plate (or bracket) has slots for receiving bolts for mounting the bar to the plate (bracket) and the plate (bracket) to the frame. When the bolts are loosened, each plate (bracket) can be repositioned relative to the frame (so that the slots translate relative to the bolts) and then fixed in the new position by re-tightening the bolts. 
     With reference again to  FIG. 1 , after holders  36  (and the prunes or other articles carried in their pockets) have translated past shaker bars  111  and into housing  22 , a pitting knife assembly in housing  22  engages the translating prunes (or other fruit) to push out the pit from within each fruit. 
     The pits either fall directly into chute  83  (shown in  FIG. 4 ), or they are brushed away from the holders by a rotating brush assembly (to be described with reference to  FIG. 4 ) and then fall into chute  83 . The rotating brush assembly comprises rotatably mounted pit brush  61  (having paddles tipped with rubber), brush drive sprocket  59 , brush drive shaft  63  (to which brush  61  is attached), and brush drive chain  64  looped around sprocket  59  and shaft  63 . Sprocket  59  and above-described pulleys  21 B and  11 B are mounted to the same rotatable shaft. In response to rotation of sprocket  59  (with pulleys  21 B and  11 B) by motor  24 , chain  64  rotates shaft  63 , thereby actively rotating brush  61  relative to each of holders  36  translating away from the pitting knives so that the paddles of brush  61  sweep away any pits that may cling to the holders (so that the pits fall into pit chute  83 ). 
     Alternatively, a fixed, pit wiper assembly is used in place of actively driven, rotatably mounted pit brush  61  (and shaft  63 , drive sprocket  59 , and brush drive chain  64 ). Such a wiper assembly may comprise two mounting bars, a mounting rod connected between the bars, and a wiping blade mounted to the rod, and may be fixedly mounted in a position above pit discharge chute  83  and just below the bottom surfaces of fruit holders  36 , to wipe any clinging pits from each passing holder  36  as the holder translates above bin  83  following the operations of pitting and post-pitting disengagement of the pitting knives from the holder. 
     Following pitting, as the holders exit the pitting head, the pockets defined by each holder are opened by cam assembly  116  (comprising a pair of pocket-opening cam tracks similar to above-described cam tracks  80 ) shown schematically in  FIG. 1 , and the pockets are then shaken by passing through shaker bar assembly  113  (comprising shaker bars similar to above-described bars  111 A and  111 B), to cause the pitted prunes fall out of the pockets. 
     A pitting knife assembly mounted between plates  12  and  12 A of housing  22  typically includes multiple rows of pitting knives (one row of knives for pitting fruit in each of two or more holders  36 ). Each row of pitting knives includes one knife for each pocket defined by one of the holders (e.g., one knife for each of the four pockets defined by holder  36 ). For example, in the apparatus of  FIGS. 4 ,  8 , and  15  there are two rows of pitting knives, each row comprising four knives  102 . The pitting knives in one row pit the prunes in one holder  36  while the pitting knives in the other row simultaneously pits the prunes in another holder  36 . A conventional implementation of such a knife assembly will next be described with reference to FIGS.  4  and  8 - 10 , and an embodiment of the inventive knife assembly will later be described with reference to  FIGS. 11-15 . 
     The conventional pitting knife assembly of  FIGS. 4 ,  8 , and  9  includes two shafts  4  (one of which is shown in  FIG. 4  and both of which are shown in  FIG. 8 ) fixedly mounted between vertically oriented plates  12  and  12 A of housing  22 . A portion of the knife assembly hangs from shafts  4  in a manner to be explained below. The knife assembly also includes rotatably mounted drive shaft  21  which is rotated about its axis by belt  28 , which is in turn driven by motor  24 . 
       FIG. 8  is a cross-sectional view (in a vertical plane) of a portion of a conventional pitting knife assembly.  FIG. 9  is a cross-sectional view (along line  9 - 9  of  FIG. 8 ) of the  FIG. 8  assembly (with several elements omitted for clarity). The assembly of  FIGS. 8 and 9  employs box cam  109  to move a rocker arm assembly reciprocally (both up and down). Rather than a box cam, other conventional pitting knife assemblies employ an open cam (to move a rocker assembly down during part of its cycle) and springs (to move the rocker assembly up during the remaining part of its cycle). 
     Member  114  is fixedly attached to a carriage comprising upper carriage plate  7 , lower carriage plate  132 , and tie bar  30 . The carriage hangs from a pair of rotatably mounted swing arms  2 ′. The upper end of each arm  2 ′ is rotatably attached to one of parallel shafts  4 . A pin  119  protrudes from the lower end of each arm  2 ′ into a tube  120 . Both tubes  120  are fixedly attached to lower carriage plate  132 . Thus, as the carriage rocks back and forth (in response to rotation of eccentric  42 ′), the carriage imparts this rocking motion to tubes  120  and pins  119 , thus causing arms  2 ′ to swing back and forth on fixed shafts  4 . More specifically, as the carriage rocks, pins  119  translate reciprocally as a unit with tubes  120 . During the reciprocal translation of pins  119  together with tubes  120 , each pin  119  rotates relative to the tube  120  which surrounds it (about the common axis of the pin and the surrounding tube). 
     Two parallel plunger shafts  15  extend through upper carriage plate  7  and lower carriage plate  132 , each with freedom to translate in the direction of its longitudinal axis relative to the plates  7  and  132 . A pitting knife assembly (including two rows of pitting knives  102 ) is fixedly attached to the lower ends of shafts  15 . Thus (assuming for the moment that shafts  15  are held fixed relative to the carriage), as the carriage (including plates  7  and  132 ) rocks back and forth, shafts  15  translate reciprocally as follows: the center of gravity of each shaft  15  translates back and forth along an arc of a circle in the plane of  FIG. 8 , but neither shaft  15  rotates (about its center of gravity) in the plane of  FIG. 8 . 
     However, the actual motion of shafts  15  (and the knives  102  fixedly attached thereto) is more complicated, because a mechanism (including cam  109  and rocker arm unit  133 ) is provided to reciprocate shafts  15  longitudinally relative to the carriage as the carriage rocks back and forth. Unit  133  includes top rocker arms  43  and  43 A, rocker spacers  40 , and bottom rocker arms  45 , to be described below). The longitudinal motion of shafts  15  is timed relative to the swinging motion thereof (by the orientation of cam  109  relative to that of eccentric  42 ′), so that the knives  102  undergo the following motion: knives  102  move longitudinally downward (into engagement with the prunes to be pitted) while the carriage swings in the direction of motion of the prunes (which corresponds to “toward the right” in  FIG. 8 ), knives  102  then move longitudinally upward (until they are out of engagement with the prunes) while the carriage continues to swing in the direction of motion of the prunes, knives  102  then continue to move longitudinally upward while the carriage begins to swing in opposite direction (toward the left in  FIG. 8 ), and finally knives  102  begin to move longitudinally downward (toward a new set of prunes to be pitted) while the carriage continues to swing in the direction opposite the direction of motion of the prunes. 
     Each knife  102  preferably has a groove  102 A (a small diameter portion) near its tip as shown in  FIG. 8 . Each groove  102 A defines shoulders which engage the fruit flesh when the knife is being withdrawn after pitting (to assist in separating the pitted fruit from the holder). 
     As shown in  FIG. 8 , box cam  109  is fixedly mounted to shaft  21  (at a different location along the axis of shaft  21  than the location at which eccentric  42 ′ is fixedly mounted) using set screw  176 , key  177  and split clamp  115  (clamp  115  has two portions which can be tightened together) shown in  FIG. 8 . To mount cam  109  to shaft  21 , key  177  is inserted in shaft  21 . Then set screw  176  is inserted through a channel in cam  109  into a tapped hole in cam  109 , and both the first and second portions of split clamp  115  are inserted in another channel in cam  109 . Cam  109  is then positioned with respect to shaft  21  so that a hole in cam  109  is aligned with key  177 . Then, set screw  176  is advanced through the hole into engagement with key  177 . To lock box cam  109  onto shaft  21 , screw  176  is tightened against key  177  in shaft  21  and box cam  109 , and the second portion of clamp  115  is tightened against shaft  21  and the first portion of clamp  115 . 
     Box cam  109  has a groove (a recessed portion) in each of its side faces. Each groove defines an outer cam surface  9 A and an inner cam surface  9 C opposed to the outer cam surface. Cam surfaces  9 A and  9 C of one side face of cam  109  define an oblong, closed first cam track (as shown in  FIG. 8 ). Cam surfaces  9 A and  9 C of the other face of cam  109  define an oblong, closed second cam track which is a mirror image of the first cam track. 
     One cam follower  140  attached to upper arm  43  of rocker arm unit  133  between the fixed end of unit  133  (the end attached to pin  112 ) and the free end of unit  133  rides between cam surfaces  9 A and  9 C of the first cam track. Another cam follower  140  attached to upper arm  43 A of rocker arm unit  133  between the fixed end of unit  133  (the end attached to pin  112 ) and the free end of unit  133  rides between cam surfaces  9 A and  9 C of the second cam track. The first and second cam tracks are aligned, so that one cam follower  140  is always directly below (into the plane of  FIG. 8 ) the other cam follower  140  when the knife assembly is viewed from the viewpoint of  FIG. 8 . 
     Box cam  109  has a removable insert portion which defines part of outer cam surfaces  9 A when the box cam  109  is initially installed. The insert portion is removed from the rest of cam  109  to allow assembly of rocker arm unit  133  with box cam  109  (so that cam followers  140  ride properly between cam surfaces  9 A and  9 C of each cam track of cam  109 ). After cam  109  and unit  133  have been assembled together, the insert is reinstalled back to its original position. 
     A cam follower  23  protrudes from each of shafts  15  into engagement with unit  133  (near unit  133 &#39;s free end) as shown in  FIGS. 8 and 9 . 
     Since each cam follower  140  always rides between an upper and a lower cam surface of cam  109  (regardless of the rotational orientation of shaft  21  and cam  109 ), cam  109  exerts an upward force on cam followers  140  (and thus on unit  133 ) during some portions of the rotational cycle of cam  109  and cam  109  exerts a downward force on cam followers  140  (and thus on unit  133 ) during the other portions of cam  109 &#39;s rotational cycle. In particular, when the large radius portion of the aligned cam tracks (the cam track portion along which inner cam surfaces  9 C are radially farthest from the central longitudinal axis of shaft  21 ) engages cam followers  140 , cam  109  pushes followers  140  down, thus pivoting arm unit  133  counterclockwise about pin  112  (in the plane of  FIG. 8 ), which causes arm unit  133  to force cam followers  23  downward, which in turn translates shafts  15  longitudinally downward relative to the carriage. Then, when continuing rotation of shaft  21  rotates the small radius portion of the aligned cam tracks (the cam track portion along which inner cam surfaces  9 C are radially nearest to the central longitudinal axis of shaft  21 ) engages cam followers  140 , cam  109  pushes followers  140  up, thus pivoting arm unit  133  clockwise about pin  112  (in the plane of  FIG. 8 ), which causes arm unit  133  to force cam followers  23  upward, which in turn translates shafts  15  longitudinally upward relative to the carriage. 
     When installed, rocker arm unit  133  has freedom to pivot relative to pin  112  about the axis of pin  112 . Stroke adjusting support bar  11 ′ is fixedly attached to frame plate  12 A. Before operating the apparatus, stroke adjustment bearing screw  110 ′ can be repositioned relative to bar  11 ′ in order to change the position of pin  112  and unit  133  (and thus shafts  15  engaged with unit  133 ) relative to frame plate  12 A (and the entire frame of the apparatus) during operation. 
     Unit  133  includes upper arms  43  and  43 A and lower arms  45  (there are two arms  45 , only one of which is shown in  FIG. 8 ). One end of each of upper arms  43  and  43 A and lower arms  45  is fixedly attached to body member  149 , and spacer  150  is connected between arms  43  and  43 A. Tie bar  49  and spacers  40  are connected between the other ends (the “free” ends) of arms  43 ,  43 A, and  45 , with bar  49  connected between the free ends of arms  43  and  43 A (as best shown in  FIG. 9 ), one spacer  40  connected between the free ends of arm  43  and the arm  45  below arm  43 , and the other spacer  40  connected between the free ends of arm  43 A and the arm  45  below arm  43 A. 
     Preferably, the cam follower  140  rotatably attached to each of arms  43  and  43 A (as best shown in  FIG. 22 ) includes a roller (for engaging cam tracks of box cam  109 ) rotatably mounted to a threaded shaft. To mount the cam follower to arm  43  or  43 A, the shaft is inserted through a hole in the arm and a nut is threaded onto the shaft to retain the cam follower in place. Preferably, a grease fitting  152  is provided at the location of each cam follower  140 , to enable lubrication of the cam followers. 
     In operation of the knife assembly, cam followers  140  ride in the cam tracks of box cam  109 , thus forcing unit  133  to pivot relative to fixed pin  112  and screw  110 ′. As unit  133  pivots (clockwise or counterclockwise with respect to the central axis of pin  112 ), unit  133  drives shafts  15  longitudinally up or down, as follows. A cam follower  23  protrudes from one shaft  15  into the space between arm  43  and arm  45  below arm  43 , and another cam follower  23  protrudes from the other shaft  15  into the space between arm  43 A and arm  45  below arm  43 A. Thus, cam followers  23  engage arms  43 ,  43 A, and  45 , and these arms force cam followers  23  up and down as they pivot with the rest of unit  133 . 
     As unit  133  undergoes reciprocating pivoting motion in response to rotating box cam  109 , the entire carriage assembly (including shafts  30 ,  15 , and  114  and carriage plates  7  and  132 ) undergoes rocking motion in response to rotating eccentric  42 ′. More specifically, eccentric  42 ′ is attached (at a bearing) to shaft member  114 , with eccentric  42 ′ having freedom to rotate relative to member  114 . Cam  109  and eccentric  42 ′ are fixedly mounted to shaft  21  (at different locations along the axis of shaft  21 ). As eccentric  42 ′ rotates with shaft  21 , eccentric  42 ′ exerts force on member  114  which causes member  114  to undergo reciprocating motion as follows: the center of gravity of member  114  translates back and forth along an arc of a circle in the plane of  FIG. 8 , but member  114  does not rotate (about its center of gravity) in the plane of  FIG. 8 . This rocking motion of the carriage imparts a rocking component to the motion of shafts  15  (perpendicular to the longitudinal axes of shafts  15 ), which enables shafts  15  to translate knives  102  so as to follow translating specimens of fruit during periods when cam  109  is forcing shafts  15  (and thus knives  102 ) longitudinally downward into engagement with the fruit. 
       FIG. 10  is a graph representing the vertical position of the tip of one of the pitting knives  102  of the  FIG. 8  assembly, as a function of time.  FIG. 10  shows that the vertical position of the knife tip is cyclical, with pitting occurring at times t 1  and t 2 . As is apparent from inspection of  FIG. 10 , the knife tip moves (vertically) very rapidly downward toward its lowest position (at each of pitting times t 1  and t 2 ), and very rapidly upward from its lowest position. 
     Next, we describe the pitting operation in more detail (in an implementation in which motor  24  continuously translates holders  36  around the loop defined by sprocket assemblies  32 C,  32 D, and  34 ).  FIG. 5  shows a holder  36  and one row of four knives  102  in their lowest position (extending all the way through pitting rubbers  70  of the four pockets defined by the holder), in the position the knives would occupy immediately after pushing pits downward (through rubbers  70 ) from within four articles of fruit seated in the pockets.  FIG. 6  shows one knife  102  of each of the two rows of knives  102 , also in the lowest knife position. For clarity, portions of some of the holders  36  mounted on chains  35  are not shown in  FIG. 6  (only the pitting rubbers  70  of the partially-shown holders  36  are visible in  FIG. 6 ). 
     As shown in  FIGS. 5 and 6 , fruit stripping grill  94  is mounted (by brackets  94 A) between plates  12  and  12 A. After the pitting operation, knives  102  retract upward and to the right (when viewed as in  FIG. 6 ) from vertically fixed holders  36  through holes in the fixedly mounted grill  94 . Typically, most (or all) of the pitted fruit flesh falls from the knives  102  before the knives  102  reach grill  94 . The grill  94  strips any pitted fruit flesh which clings to the retracting knives  102 . The pitting knives  102  then move back to the left (when viewed as in  FIG. 6 ) away from grill  94 . The holders (with pitted fruit) then translate to cam assembly  116  (which opens the spring-biased pockets of each holder) and then to cam assembly  113  (which shakes the pitted fruit from the pockets) so that the pitted fruit fall from the holders into a product bin or conveyor (not shown). Optionally, water is sprayed on the pitted fruit and on grill  94  (e.g., from spray pipe  37  and spray nozzle  48  shown in  FIG. 4 ). 
     Following pitting, as holders  36  exit the pitting head, the pockets defined by each holder are opened by cam assembly  116  (comprising a pair of pocket-opening cam tracks) and the pockets are then shaken by passing through shaker bar assembly  113  (comprising a pair of cam tracks known as shaker bars) to cause the pitted prunes fall out of the pockets. 
     With reference to  FIG. 5 , cam tracks  85  and  85 A (each mounted to one of plates  12 A of housing  22  as shown in  FIG. 5 ) are separated in the plane of  FIG. 5  by a relative small distance, so that the pockets defined by holders  36  are closed to grip tightly the fruit being pitted. After the pitting step, each holder  36  of  FIGS. 5 and 6  continues to translate (out of the plane of  FIG. 5 ; toward the right in  FIG. 6 ) until the holder (e.g., the holder  36  shown in  FIG. 5 ) encounters aligned notches  85 B in cam tracks  85  and  85 A (notch  82 B in cam track  85 A is shown in  FIG. 7 ). While each holder  36  translates between notches  85 B, the holder&#39;s springs (springs  62 , described with reference to  FIG. 3 ) briefly relax and are then re-compressed (thereby briefly opening the pockets). Knives  102  (which extend through the fruit in each pocket of the holder at the end of the pitting step) begin to translate upward while the pockets are briefly open. The brief opening of each pocket (in response to relaxation of the springs) releases pressure on the pitted fruit in each pocket, thereby allowing upward-translating knives  102  to strip the fruit from pitting rubbers  70  of the pockets before the pockets return to their closed configuration. This action improves the efficiency of separation of the pitted fruit from the holders (by assemblies  116  and  113 ) following pitting. 
     Some conventional variations on the above-described pitting apparatus employ an intermittent fruit holder conveyor drive mechanism. In such variations, the fruit holders are translated into position for pitting, then remain stationary during pitting, and are then translated away from the pitting position. For example, sprockets  32 C of the  FIG. 1  system could implement a cam indexing mechanism to drive fruit holder conveyer chains  35  in such an intermittent manner while motor  24  drives the pitting knives continuously. 
     It had not been known until the present invention how to design an apparatus for pitting prunes or dates (or similar soft fruit) in a manner overcoming the disadvantages and limitations of conventional pitting systems (including those including open cam or box cams in their pitting knife drive assemblies). 
     SUMMARY OF THE INVENTION 
     In a class of embodiments, the invention is a pitting knife assembly including: a pitting knife mount; and a pulley drive assembly coupled to the pitting knife mount and configured to move the knife mount around a circular (or substantially circular) path. During operation of the pitting knife assembly with at least one pitting knife (e.g., a set of pitting knives) mounted to the pitting knife mount and a fruit conveying assembly positioned and configured to convey fruit to the pitting knife assembly, the pitting knife can produce pitted fruit by moving into engagement with fruit conveyed by the conveying assembly (to pit the fruit) as the pitting knife mount moves through a first portion of the path, and the pitting knife can then move out of engagement with (and away from) the pitted fruit as the pitting knife mount moves through a second portion of the path. Typically, the pitting knife assembly includes a frame, a drive shaft assembly (which may include a drive shaft and at least one drive pulley coupled to the drive shaft) rotatably mounted to the frame, at least one pair of pulleys coupled to and drivable by the drive shaft assembly, and a connector (typically a connector rod) rotatably connected between the pulleys of each said pair so as to remain oriented at least substantially parallel to a line through the centers of the pulleys of the pair while the pulleys are driven by the drive shaft assembly, and the pitting knife mount is coupled to the connector such that said connector moves the pitting knife mount around the at least substantially circular path when each said pair of pulleys is driven by the drive shaft assembly. 
     In a second class of embodiments, the invention is a fruit pitting apparatus including a pitting knife assembly and a conveying assembly positioned and configured to convey fruit to the pitting knife assembly. The pitting knife assembly includes at least one pitting knife, and a pulley drive assembly coupled and configured to move the pitting knife around an at least substantially circular path. In operation, the pitting knife assembly can produce pitted fruit by moving the pitting knife into engagement with fruit conveyed by the conveying assembly (to pit the fruit) as the pitting knife moves through a first portion of the path, and the pitting knife can then move out of engagement with (and away from) the pitted fruit as the pitting knife moves through a second portion of the path. Typically, the fruit pitting apparatus is configured to remove pits from prunes (or similar soft fruit such as dates) and the conveying assembly is configured to seat the fruit in holders and translate the fruit and holders (typically intermittently, but continuously in some alternative embodiments) past the pitting knife assembly. 
     Typically, the conveying assembly includes fruit holders and is configured to move the fruit holders intermittently relative to the pitting knife assembly (e.g., sprockets  32 C of the conveying assembly of  FIG. 15 , or an assembly associated therewith, includes a cam driven indexer that is configured to move fruit holders  36  intermittently relative to the pitting knife assembly). Preferably, the conveying assembly includes a cam driven indexer for timing motion of fruit holders relative to the pitting knife assembly, and the cam driven indexer is configured to move the fruit holders at a forward speed that matches the forward speed of each pitting knife of the pitting knife assembly (while the pitting knife moves into engagement with fruit in one of the holders and pits the fruit), and then to stop each said fruit holder after pitting to allow the pitting knife assembly to rotate the pitting knife up, around and back down for another pitting index. 
     Typically, the pitting knife assembly (in the second class of embodiments of the inventive apparatus) includes a frame, and a knife mount to which each said pitting knife is mounted, and the pulley drive assembly includes a drive shaft assembly (which may include a drive shaft and at least one drive pulley coupled to the drive shaft) rotatably mounted to the frame, at least one pair of pulleys coupled to and drivable by the drive shaft assembly, and a connector (e.g., a connector rod) rotatably connected between the pulleys of each said pair to remain oriented at least substantially parallel to a line through the centers of the pulleys of the pair while the pulleys are driven by the drive shaft assembly, and the pitting knife mount is coupled to the connector such that said connector moves the pitting knife mount around the at least substantially circular path when each said pair of pulleys is driven by the drive shaft assembly. 
     In some embodiments, the invention is a pitting knife drive system including pitting knives. The pitting knife drive system is configured to be mounted in a fruit pitting apparatus including fruit holders and a conveyor system for translating the fruit holders. The pitting knife drive system is configured to drive the pitting knives relative to the holders, the conveyor system is configured to drive the holders intermittently, and the pitting knife drive system and the conveyor system are configured to translate the knives with the holders during pitting and to keep the holders stationary when the pitting knife drive system lifts the pitting knives out of the holders after pitting. The pitting knife drive system typically includes a knife mount (to which the pitting knives are mounted) and a set of timing pulleys on each side of the knife mount. Each said set of timing pulleys is synchronized by a connecting rod and a timing belt which drives the timing pulleys together. Each said connecting rod is held in a fixed orientation (e.g., a vertical orientation) by the synchronized rotation of the timing pulleys, where this orientation is at least substantially perpendicular to the path of advancing fruit being conveyed in the holders. As the pulleys rotate the connecting rod, the attached knife mount will raise and then lower into the holders to push the pits out of fruit therein. The timing belts are typically driven by a common drive shaft which drives two additional timing pulleys, one for each set of synchronized timing pulleys, so as to rotate the two sets of pulleys together and to keep the knife mount aligned with the path of the fruit holders. The conveyer system is preferably driven by an indexer to synchronize the movement of the holders with the pitting knives. 
     In some embodiments, the invention is an apparatus for removing pits from prunes (or similar soft fruit such as dates), including a pitting knife drive assembly, a knife set (including one or more pitting knives) driven by the drive assembly, and a conveyor assembly for seating the fruit in holders and translating the fruit and holders (continuously or intermittently) past the knife set. The pitting knife drive assembly includes: a pair of pulleys (typically identical disks) positioned vertically with respect to each other. A bearing shaft (or other cam follower) extends out from each of the pulleys (e.g., from a hole in each of the pulleys) in a position located away from the center of said each of the pulleys. With the cam followers aligned at the same azimuthal angle (about the centers of the pulleys from which they extend), a connector (e.g., a connector rod) is attached to the cam followers. Then, as the pulleys of each pair are driven together, the connector moves around a circular path while remaining in a parallel alignment with respect to a line between the pulleys&#39; centers. With such a connector attached to each side of the knife set, the knife set is moved in a circular path which is timed with the continuous or intermittent motion of the conveyer assembly translating the fruit past the knife set. In preferred embodiments, the holders are driven (by a cam indexer drive unit) intermittently through a pitting area, and the knife driving assembly has a single, driven, drive shaft which drives two attached timing pulleys, one on each side of the knife set. These timing pulleys drive timing belts which in turn drives two pairs of additional timing pulleys (which are sometimes referred to as disks, and are typically larger than the timing pulleys attached to the drive shaft). The disks in each pair are aligned with one vertically below the other, and their centers form a perpendicular line to the holders&#39; translating direction. A cam follower is mounted to each disk (e.g., each disk has a hole in which a cam follower is mounted), and these cam followers are aligned with timing pulley teeth so that when assembled with a connector rod between the cam followers and a timing belt driving the disks, the connector rod&#39;s orientation is fixed parallel to a line between the disks&#39; centers and perpendicular to the holders&#39; translating direction. One set of these timing belt drive assemblies is on each side of the knife set, for driving the pitting knives in a smooth circular motion. 
     Typical embodiments of the inventive knife drive mechanism have the following advantages over conventional box cam (or open cam) knife drive mechanisms: 
     they drive the pitting knives such that their motion profile (along an axis perpendicular to the translating direction of the fruit holders) is a smooth sinusoidal motion (in contrast with the convention motion profile which includes a steep acceleration, a sudden direction change, and typically bouncing in or on the cam); and 
     the total part count is reduced (e.g., from 71 to 52 parts, representing a 25% decrease in parts) and the number of different parts is reduced (e.g., from 32 to 11 parts, representing a reduction of 65%), resulting in cost savings for parts and assembly and maintenance labor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view (partially cut away) of a conventional prune pitting apparatus. 
         FIG. 2  is a cross-sectional view of a portion of the prune pitting apparatus of  FIG. 1 , taken along line  2 - 2  of  FIG. 1 . 
         FIG. 2A  is a cross-sectional view of a portion of the prune pitting apparatus of  FIG. 1 , taken along line  9 - 9  of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the apparatus of  FIG. 2  (with roller  68  omitted for clarity), taken along line  3 - 3  of  FIG. 2 , showing one of paddle wheels  38  sweeping across the pockets of one fruit holder  36 . 
         FIG. 4  is an end elevational view of the  FIG. 1  apparatus (with pitting knives  102  in a lowered position). 
         FIG. 5  is an enlarged view of a portion of the  FIG. 4  assembly. 
         FIG. 6  is a cross-sectional view of a portion of the  FIG. 4  assembly (in a vertical plane perpendicular to the plane of  FIG. 4 ). 
         FIG. 7  is a top elevational view of a portion of an implementation of the  FIG. 1  apparatus which shows notched implementations of cam tracks  85  and  85 A. 
         FIG. 8  is a cross-sectional view (in a vertical plane) of a portion of a conventional pitting knife assembly which can be mounted in pitting head knife assembly  22  of  FIGS. 1 and 4 ). 
         FIG. 9  is a cross-sectional view (along line  9 - 9  of  FIG. 8 ) of the  FIG. 8  assembly (with several elements omitted for clarity). 
         FIG. 10  is a graph representing the path of the tip of one of the pitting knives of the  FIG. 8  assembly. 
         FIG. 11  is a perspective view of an embodiment of the inventive pitting knife assembly. 
         FIG. 12  is a front view of a portion of the  FIG. 11  assembly. 
         FIG. 13  is a top view of the  FIG. 11  assembly. 
         FIG. 14  is a cross-sectional view (in a vertical plane) of a portion of the  FIG. 11  assembly. 
         FIG. 15  is an end elevational view of a prune pitting apparatus whose pitting knife assembly is identical to the  FIG. 12  assembly.  FIG. 15  is an exploded view of the apparatus in the sense that its pitting knife assembly is shown enlarged relative to, and separated from, the rest of the apparatus. When the apparatus is fully assembled, pitting knife mount  301  can position pitting knives  102  in a lowered position (shown in phantom view) relative to fruit holders  36 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the inventive pitting knife assembly will be described with reference to  FIGS. 11-15 . The prune pitting apparatus of  FIG. 15  includes the knife drive assembly of  FIGS. 11-14 . 
     All elements of the apparatus of  FIGS. 11-15  which are identical to corresponding elements of the apparatus of  FIGS. 1-7  are identically numbered in  FIGS. 1-7  and  11 - 15  and the foregoing description thereof will not be repeated with reference to  FIGS. 11-15 . 
     The pitting knife assembly of  FIGS. 11-14  includes a frame having side portions  308  and  308 A. The pitting knife assembly is designed to be mounted to a conveyor assembly of a prune pitting apparatus. For example, it can be mounted to the conveyor assembly of the prune pitting apparatus of  FIGS. 1-7  (which is identical to the conveyor assembly of the  FIG. 15  apparatus), with side frame portion  308  aligned with and attached to side plate  12  of the conveyor assembly and side frame portion  308 A aligned with and attached to side plate  12 A of the conveyor assembly as indicated in  FIG. 15 . 
     We next describe one side of the pitting knife assembly of  FIGS. 11-14 ; the other side is a mirror image of it (since the assembly is symmetric about a vertical plane through its center). Two shafts  302 , one directly above the other, are attached to side frame portion  308  (and two identical shafts  302  are attached to side frame portion  308 A) with roller bearings  303  which allow shafts  302  to rotate freely relative to the frame. Pulleys  304  are slid onto shafts  302  (one pulley  304  on each shaft  302 ) and fastened with set screws to prevent sliding. When the apparatus is assembled, pulleys  304  are free to rotate with shafts  302 . Each pulley  304  has a precisely drilled hole for receiving a cam follower  307 . With a cam follower  307  pressed into each pulley  304 , the vertically aligned pulleys  304  are rotated to align cam followers  307  at the same azimuthal angle about the center of the pulley  304  to which it is mounted (as shown in  FIG. 11 ). Connecting rod  313  is then slid onto the aligned cam followers  307  and secured with a nut on the end of each cam follower  307 . Cam followers  307  are rotatable relative to rod  313 , so that rod  313  remains vertically oriented while timing belt  325  (to be described below) rotates pulleys  304  about their centers. The described assembly steps are repeated to assemble the corresponding elements on the other side of the apparatus. 
     Alternatively, a cam follower (e.g., cam follower  307 ) is mounted to each pulley  304  (sometimes referred to herein as a disk or timing pulley) in another manner, but so the cam follower extends out from the timing pulley (in a direction parallel to drive shaft  21  when the apparatus is assembled). During assembly, the cam followers of each pair of timing pulleys (on each side of the apparatus) are aligned with teeth of the timing pulleys so that when assembled with a connector rod between the aligned cam followers and a timing belt driving the timing pulleys, the connector rod&#39;s orientation is fixed parallel to a line between the timing pulleys&#39; centers and perpendicular to the translating direction of fruit holders with which the pitting knife assembly is employed. 
     Then, two drive pulleys  315  are slid onto drive shaft  21 , and fastened to shaft  21  with set screws. A timing belt  325  is looped around the pair of timing pulleys  304  and one drive pulley  315  on one side of the apparatus, and another timing belt  325  is looped around the other pair of timing pulleys  304  and the other drive pulley  115  on the other side of the apparatus. Drive shaft  21  is mounted to frame side portions  308  and  308 A using drive bearings so that shaft  21  is free to rotate relative to the frame. A timing belt adjustment element  316  is mounted to each side of the frame for adjusting (tensioning) each timing belt  325 . Pulley  11 B is fixedly attached to an end of shaft  21 , so that rotation of pulley  11 B causes shaft  21  to rotate about its axis relative to the frame. Typically also, sprocket  59  is fixedly attached to pulley  11 B and  21 B. Elements  59  and  21 B are omitted from  FIG. 11  for clarity but shown in  FIG. 15 . 
     Knife mount  301  is fastened between connector rods  313 , and pitting knives  102  (typically, two rows of four knives  102 ) are mounted to knife mount  301 . 
     Motor  11  is mounted to the frame. Drive pulley  11 A is rotatably mounted to the frame by a bearing and fixedly attached to a rotatable motor shaft (which extends out from motor  11 ). Drive belt  11 C (shown in  FIGS. 11 and 13  but not in  FIG. 12  for clarity) is looped around pulleys  11 A and  11 B. Pulley  21 B and sprocket  59  are fixedly attached to pulley  11 B. Thus, in response to rotation of pulley  11 A by motor  11 , drive belt  11 C rotates pulleys  11 B and  21 B and sprocket  59  together as a unit relative to the frame. 
     As drive shaft  21  is driven by rotating pulley  11 B, the drive pulleys  315  drive the timing belts  325  on both sides of the apparatus, which in turn rotates pulleys  304 . This rotation of pulleys  304  moves both connector rods  313  in a circular pattern, and such movement of rods  313  moves knife mount  301  (and each pitting knife  102  mounted thereto) around a circular path. When a fruit holder conveyor assembly is positioned below the knife mount  301 , and the conveyor assembly operates to advance fruit holders (e.g., holders  36  of  FIG. 15 ), and fruit within the holders, perpendicular to the plane of  FIG. 15  (or  FIG. 12 ), movement of knife mount  301  around this circular path plunges each pitting knife  102  (mounted to the mount  301 ) through one of the holders (and into any article of fruit within the holder, thereby removing the pit from the fruit), and then raises the knife mount  301  (and each pitting knife  102 ) away from the fruit leaving the pitted fruit in the holder. 
     In variations on the described apparatus, the inventive pulley drive mechanism (including a pair of connector elements corresponding to rods  313 ) moves a pitting knife mount (and each pitting knife mounted thereto) around a closed path that is substantially circular but not circular. Movement of the knife mount around this closed path (while a conveyor assembly operates to advance fruit holders relative to the pitting knife assembly) can also plunge each pitting knife (mounted to the mount) through one of the holders (and into any article of fruit within the holder, thereby removing the pit from the fruit), and then raises the knife mount (and each pitting knife) away from the fruit leaving the pitted fruit in the holder. 
     As noted,  FIG. 15  is an end elevational view of a prune pitting apparatus whose pitting knife assembly is identical to the  FIG. 12  assembly. When the apparatus is fully assembled, the pitting knife assembly can position pitting knife mount  301  and thus pitting knives  102  in a lowered position (shown in phantom view in  FIG. 15 ) relative to fruit holders  36 . As the holders  36  advance in a direction perpendicular to the plane of  FIG. 15  and the pitting knife assembly moves knife mount  301  around a circular path, the pitting knife assembly is configured to move mount  301  into a fully lowered position (not shown) in which knives  102  extend into the holders  36 , and then into a raised position in which the knives  102  are disengaged from (and above) the holders  36 . The circular path is in a plane perpendicular to the plane of  FIG. 15 . 
     In a class of embodiments, the pitting apparatus of the invention employs an intermittent fruit holder conveyor drive mechanism to accomplish pitting of prunes, dates, or similar soft fruit. In these embodiments, the holder conveyor drive mechanism translates the fruit holders (e.g., holders  36 ) into position for pitting, then keeps the holders stationary after pitting (while the pitting knives are repositioned for a subsequent pitting operation), and then translates the holders away from the pitting position and translates a new set of holders into position for pitting (so that each holder undergoes intermittent motion). For example, in operation of preferred implementations of the  FIG. 15  apparatus, the holders  36  translate intermittently around the loop defined by chains  35 . For example, sprockets  32 C of the conveying assembly of  FIG. 15  (or an assembly associated with sprockets  32 C) include a cam driven indexer that is configured to move fruit holders  36  intermittently relative to the pitting knife assembly. The cam driven indexer times the motion of holders  36  relative to the pitting knife assembly, and the cam driven indexer is preferably configured to move the fruit holders  36  at a forward speed that matches the forward speed of each pitting knife  102  of the pitting knife assembly (while the pitting knife moves into engagement with fruit in one of the holders and pits the fruit), and then to stop each fruit holder  36  after pitting to allow the pitting knife assembly to rotate the pitting knife up  102 , around and back down for another pitting index. 
     In some alternative embodiments, variations on the  FIG. 15  apparatus translate holders  36  continuously around the loop defined by chains  35  (even during pitting). In such embodiments, the apparatus would typically include notched cam tracks  85  and  85 A of the same type as described above with reference to  FIG. 7 . 
     In other embodiments, the invention is an apparatus for pitting fruit (e.g., prunes) of any of the types described above, but with one or more of its conveyors implemented as elastomeric timing belts rather than as metal chains (such as chain  35  looped around sprockets  32  and  34 ). Use of such timing belts eliminates problems which can result due to chain stretch and eliminates the need to lubricate metal conveyor chains. 
     The foregoing is merely illustrative and explanatory of preferred embodiments of the inventive apparatus. Various changes in the component sizes and shapes, and other details of the embodiments described herein may be within the scope of the appended claims.