Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/986,865 filed Nov. 9, 2007, the contents of which are incorporated herein by reference thereto. 
    
    
     BACKGROUND 
     Various embodiments of the present invention relate to a pneumatically powered pole saw. 
     Manually operated pole saws require an operator to manually push and pull a long pole back and forth in order to move a saw blade attached to the end of the pole, thereby cutting tree limbs with the attached saw blade. These pole saws rely entirely upon the operator force the necessary forces to be applied to the cutting blade or saw blade of the pole saw. Accordingly, and as the operator tires the efficiency of the cutting operation is reduced. 
     Accordingly, it is desirable to provide a powered pole saw having a means for efficiently converting stored energy into kinetic energy wherein the saw blade of the pole saw is actuated. 
     SUMMARY OF THE INVENTION 
     A pneumatically powered pole saw and method of operating is provided. Exemplary embodiments are directed to a pneumatically powered pole saw, comprising: an extendable pole; a head member secured to the extendable pole; a cutting blade movably mounted to the head member; a piston linked to the cutting blade, the piston being slidably received within a piston chamber of the head member; a reciprocating valve disposed in the head member, the reciprocating valve being configured for movement between a first position and a second position wherein the reciprocating valve releases a portion of a source of compressed gas into the piston chamber on one side of the piston when the reciprocating valve is in the first position causing the cutting blade to move in a first cutting direction towards a limit of travel in the first cutting direction and a first check valve provides fluid communication to the piston chamber on another side of the piston causing the reciprocating valve to move from the first position towards the second position, when the cutting blade reaches the limit of travel in the first direction, the reciprocating valve releases another portion of the source of compressed gas into the piston chamber on the another side of the piston when the reciprocating valve is in the second position causing the cutting blade to move in a second cutting direction opposite to the first cutting direction and towards a limit of travel in the second cutting direction and a second check valve provides fluid communication to the piston chamber on the one side of the piston, the reciprocating valve moving from the second position towards the first position when the cutting blade reaches a limit of travel in the second direction. 
     The above-described and other features are appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a pneumatically powered pole saw constructed in accordance with an exemplary embodiment of the present invention; 
         FIG. 1A  is a perspective view of a pneumatically powered pole saw constructed in accordance with an alternative exemplary embodiment of the present invention; 
         FIGS. 1B-D  illustrate saw blades for use in various exemplary embodiments of the present invention; 
         FIG. 2  is a side view of a pneumatically powered pole saw constructed in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  is a view along lines  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view along lines  4 - 4  of  FIG. 3 ; 
         FIGS. 5A-5D  are schematic illustrations of exemplary embodiments of the present invention; 
         FIG. 6  is a view illustrating one exemplary embodiment of the present invention; 
         FIG. 7  is a view illustrating another exemplary embodiment of the present invention; 
         FIG. 8  is a view illustrating an exemplary embodiment of the present invention; 
         FIGS. 9A-9B  are schematic illustrations of alternative embodiments of the present invention; 
         FIGS. 10A-10B  are enlarged views of a reciprocating valve shown in  FIGS. 9A-9B ; and 
         FIGS. 11A-11B  are enlarged views showing operational positions of the check valves shown in  FIGS. 9A-9B . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In accordance with exemplary embodiments of the present invention, a pneumatically powered pole saw and method for operating the pole saw is disclosed. In an exemplary embodiment the pneumatically powered pole saw will comprise a source of compressed gas for use in driving the blade of the pole saw. 
     Referring now to  FIGS. 1-5 , a pneumatically powered pole saw  10  constructed in accordance with an exemplary embodiment of the present invention is illustrated. Pneumatically powered pole saw  10  has a cutting blade  12  movably mounted to a head member  14  of the pneumatically powered pole saw. Head member  14  further comprises a cylinder  16  configured to sildably receive a piston  18  therein. In accordance with an exemplary embodiment of the present invention piston  18  has at least one O-ring or sealing member that allows the piston to slide within the cylinder while also preventing or limiting fluid communication therethrough (e.g., maintaining or preventing fluids or gases on one side of the piston from passing around the piston to another side of the piston). Piston  18  is secured to a rod  20  that is secured to cutting blade  12  via a mount  22 . Rod  20  passes through a sealed end of the housing wherein the rod is allowed to slide in and out without the release of the gases in the chamber through the opening the rod slides in. Mount  22  is configured to removably secure the cutting blade to the mount thus allowing removal and replacement of the cutting blade as it becomes worn, damaged or dulled. In one exemplary embodiment, the mount  22  has a pair of rollers  24  slidably received within a pair of complimentary channels or slots  26  disposed in a frame portion  28  of the head member. Rollers  24  allow the mount and the cutting blade to slide within a range of movement on the head member. 
     In one non-limiting exemplary embodiment, the head member further comprises a roller  30  rotatably mounted to the frame portion of the head member, the roller having a groove  32  configured to receive a non-toothed portion  34  of the cutting blade within the groove of the roller. Accordingly, roller  30  provides a means for supporting the cutting blade as it reciprocates within a range of motion on the head member. 
     In order to cause the cutting blade to traverse back and forth between a first position (e.g., cutting blade fully extended away from a distal end of the head member) and a second position (e.g., cutting blade fully retracted into the distal end of the head member) a source of compressed gas  36  is in selective fluid communication with a chamber ( 38 ,  40 ) at either side of the piston to cause movement of the piston in the chamber, wherein movement of the piston causes movement oft he cutting blade by moving the rod and the mount. It being understood that size of chambers  38  and  40  vary accordingly with the movement of the piston  18 . In one non-limiting exemplary embodiment, the source of compressed gas is self-contained reservoir of carbon dioxide. Of course, other suitable types of compressed gas are considered to be within the scope of exemplary embodiments oft he present invention. In another exemplary embodiment, the source of compressed gas is provided by a reservoir fluidly coupled to a compressor  29 , which may be a stand alone device or a wearable unit. 
     In order to provide fluid communication between the source of compressed gas and chamber  38  a first valve  42  is provided to allow selective fluid communication between the source of compress gas and chamber  38  via a conduit  44 . First valve  42  is configured to allow fluid communication between the source of compressed gas and chamber  38  when the first valve is in an open position. Alternatively, and when the first valve is in a closed position chamber  38  is in fluid communication with atmosphere so that the gas in chamber  38  may be released to allow the cutting blade to travel to the first position. This is also provided by first valve  42  and conduit  44 . Accordingly, and when the first valve is closed, chamber  38  via conduit  44  and first valve  42  allow the fluid in chamber  38  to be released into the atmosphere. 
     In order to provide fluid communication between the source of compressed gas and chamber  40  a second valve  46  is provided to allow selective fluid communication between the source of compress gas and chamber  40  via a conduit  48 . Second valve  46  is configured to allow fluid communication between the source of compressed gas and chamber  40  when the second valve is in an open position. Alternatively, and when the second valve is in a closed position chamber  40  is in fluid communication with atmosphere so that the gas in chamber  40  may be released to allow the cutting blade to travel to the second position. This is also provided by second valve  46  and conduit  48 . Accordingly, and when the second valve is closed, chamber  40  via conduit  48  and second valve  46  allow the fluid in chamber  40  to be released into the atmosphere. 
     In accordance with an exemplary embodiment of the present invention and in order to move the cutting blade to the first position the first valve is closed (e.g., gas vented from chamber  38 ) and the second valve is open (e.g., gas supplied from source to chamber  40 ). Similarly and in order to move the cutting blade to the second position the first valve is open (e.g., gas supplied from source to chamber  38 ) and the second valve is closed (e.g., gas vented from chamber  40 ). 
     In order to provide the opening and closing of valves  42  and  46  a slider  50  is movably received within head member  14  wherein movement of the slider causes the first valve and the second valve to open and close. In order to effect the movement of slider  50  a rod portion  52  of the slider has a pair of stops  54  and  56  wherein a portion  58  of the mount  22  is slidably received upon the rod portion  52 . As the cutting blade traverses towards the first position the portion  58  will contact stop  54  and cause first valve  42  to open and second valve  46  to close thus, the cutting blade will then traverse towards the second position wherein the portion  58  will contact stop  56  and cause first valve  42  to close and second valve  46  to open thus, the cutting blade will then traverse towards the first position. This reciprocal movement of the cutting blade will continue until the source of gas is no longer fluidly coupled to the first valve and the second valve. 
     As illustrated in  FIG. 4 , the slider is slidably mounted above a cover plate  60  that is configured to allow slider  50  to open and close the first and second valves. Moreover, cover plate  60  is configured to prevent excessive wear from being caused by the reciprocal movement of the slider. In an alternative exemplary embodiment, the pneumatically powered pole saw is constructed without a cover plate (See  FIGS. 5A-5D ). 
     In order to provide fluid communication between the source of inlet or compressed gas  36  and the first valve and the second valve a control valve  62  is configured to provide fluid communication between the source of inlet or compressed gas  36  and the first valve and the second valve via conduits  64  between valve  42  and valve  46  and a conduit  68  between source of compressed gas  36  and control valve  62 . In accordance with an exemplary embodiment of the present invention control valve  62  is in or proximate to head member  14  while conduit  68  extends to the source of compressed gas, which is disposed at an opposite end of a pole the head member is secured to. 
     Referring now to  FIGS. 5A-5D  operation of an exemplary embodiment of the present invention is illustrated.  FIG. 5A  illustrates the saw blade traveling in the direction of arrow  51 . During this mode of operation and in the illustrated configuration of  FIG. 5A  valve  46  is open and compressed gas is being released into chamber  40  while the gas of chamber  38  is being released into the atmosphere from a vent of valve  42  thus piston  18  and the saw blade travel in the direction of arrow  51 . It being understood that in order to effect movement in the direction of arrow  51  valve  42  is closed to conduit  64  while valve  46  is open to conduit  64  since a first feature  53  of the slider is positioned to receive a spring biased member  55  of valve  42  thus, causing conduit  64  to be closed to chamber  38  while chamber  38  is open to atmosphere via a vent  57  of valve  42 . 
     In accordance with an exemplary embodiment of the present invention member  55  is biased generally into the direction of slider  50  such that when member  55  is received into feature  53  of slider  50  conduit  64  is closed to chamber  38  and vent  57  is open releasing the gas of chamber  38  while the saw blade travels in the direction of arrow  51 . 
     Movement of the saw blade in the direction of arrow  51  continues until portion  58  contacts stop  54  ( FIG. 5B ) causing the slider  50  to translate into the position of  FIG. 5B  wherein the feature  53  is no longer aligned with member  55  and the same is depressed into valve  42  causing conduit  64  to be in fluid communication with chamber  38  via valve  42  and conduit  44 . At this position, the vent  57  of valve  42  is closed and the piston and saw blade will begin to travel in a direction opposite to arrow  51 . Moreover, and at this position valve  46  is closed and the gas of chamber  40  is being released into the atmosphere from a vent of valve  46 . It being understood that valve  46  is closed to conduit  64  while valve  42  is open to conduit  64  since a second feature  59  of the slider is no longer positioned to receive a spring biased member  61  of valve  46  thus, causing conduit  64  to be closed to chamber  40  while chamber  40  is open to atmosphere via a vent  63  of valve  46 . 
     In accordance with an exemplary embodiment of the present invention member  61  is biased generally into the direction of slider  50  such that when member  61  is received into feature  59  of slider  50  conduit  64  is closed to chamber  40  and vent  63  is open releasing the gas of chamber  40  while the saw blade travels in the direction opposite of arrow  51 . Conversely, and when member  61  is not received into feature  59  of slider  50  ( FIG. 5A ) conduit  64  is open to chamber  40  and vent  63  is closed and the saw blade and piston travel in the direction of arrow  51 . 
     Movement of the saw blade in the direction opposite of arrow  51  continues ( FIG. 5C ) until portion  58  now contacts stop  56  ( FIG. 5D ) causing the slider  50  to translate back into the position of  FIG. 5A  wherein feature  53  is aligned with member  55  and feature  59  is not aligned with member  61  causing conduit  64  to be in fluid communication with chamber  40  via valve  46  and conduit  48 . At this position, the vent  57  of valve  42  is open and the piston and saw blade will begin to travel in the direction of arrow  51 . It being understood that valve  46  is open to conduit  64  while valve  42  is closed to conduit  64  since the second feature  59  of the slider is no longer positioned to receive spring biased member  61  of valve  46  thus, causing conduit  64  to be open to chamber  40  while chamber  38  is open to atmosphere via vent  57  of valve  42 . 
     In accordance with an exemplary embodiment of the present invention, this reciprocal movement of saw blade  12 , piston  18  and slider  50  will continue until the source of compressed gas released into conduit  64  by valve  62  ceases. 
     In accordance with an exemplary embodiment and by having the control valve at or proximate to the head member conservation of the gas supply is provided as conduit  68  will traverse through the pole which can be 20 feet or longer thus, and if the pole saw was required to fill or energize conduit  68  with gas each time the pneumatically powered pole saw was activated the source of compressed gas will be depleted quicker. Of course, the pole may be of any length (e.g., 10 feet or shorter, 8 feet or shorter, 6 feet or shorter, etc.). A non-limiting range for the length of the pole may be 5-25 feet. In accordance with an exemplary embodiment conduit  68  is filled with the gas and control valve  62  turns the saw on and off by limiting the amount of gas supplied via source of gas  36 . 
     In one non-limiting exemplary embodiment, control valve  62  is an electro mechanical valve activated by a switch  70  disposed at an end of the pneumatically powered pole saw opposite from the cutting blade. In another non-limiting exemplary embodiment, control valve  62  is a pneumatically activated valve wherein a fluid conduit  72  provides fluid communication with the source of compressed gas and switch  70  allows fluid communication between valve  62  and source of compressed gas  36  wherein the compressed gas will open valve  62  and gas will be supplied to valves  42  and  46 . In this embodiment, and in order to conserve the fluid supply of compressed gas  36  conduit  72  is much smaller than conduit  68  and thus only a small amount of gas is wasted each time valve  62  is opened. Furthermore, switch or valve  70  can be operated at a much lower pressure than the pressure passing through conduit  68  and is necessary to manipulate the movement of the piston within the cylinder. 
     Referring now to  FIG. 6  a pneumatically powered pole saw  10  constructed in accordance with an exemplary embodiment of the present invention is illustrated here a source of compressed gas  36  is a bottle secured to an end of a pole  78 . In this embodiment, conduit  68  and/or conduit  72  traverse the length of pole  78  until they reach control valve  62 , which disposed in or proximate to head portion  14 . Thus, a user  80  activates the pneumatically powered pole saw by manipulating switch  70  and the saw is activated to cut a limb  82  of a tree  84 . Once the desired task is completed, switch  70  is moved to an off position and the remaining gas is eventually released from the head member. 
       FIG. 7  illustrates an alternative exemplary embodiment, wherein the source of compressed gas  36  is secured to a wearable belt or harness  86  thus, the individual wears the compressed gas and the same is secured to the conduit  68  of the pole via a flexible conduit  88 . Here the weight of the compressed gas is not on the end of the pole making the same easy to manipulate and use. 
     Referring now to  FIG. 1A  an alternative exemplary embodiment of the present invention is illustrated. Here frame portion  28  further comprises a stop member  120 . In an exemplary embodiment, stop member  120  has a pair of arms  122  and a cross member  124  that define a stop for limb that is being cut by the pole saw. For example, and as the blade is drawn towards the stop the teeth of the blade will engage the limb and apply a downward force to the limb which in turn may cause the head member to be drawn upward or in an opposite direction to the force being applied to the limb as the blade travels down towards the stop member. Accordingly, and in order to impart the cutting force to the limb in a downward stroke of the blade the stop member provides a surface to receive a portion of the limb on as the blade travels downward towards the stop member. Alternatively, and as illustrated by the dashed lines in  FIG. 1A , the frame portion  28  is configured to extend past roller  30  and enclose the same within a portion of the frame portion so that limbs being cut or not being cut do not interfere with the movement of roller  32 . 
     Referring now to  FIGS. 1B-1D  alternative configurations of the saw blade are illustrated.  FIG. 1B  illustrates a straight saw blade wherein a width  130  of the blade from the non-toothed portion  34  and a toothed portion of the blade is essentially the same thickness along an edge  132  that is received within groove  32  of roller  30 . Accordingly, and in this embodiment, the teeth of the blade generally act upon a cutting surface in a linear fashion. 
     Alternatively, and referring now to  FIG. 1C , the width  130  of the blade from the non-toothed portion  34  and a toothed portion of the blade is not the same thickness along an edge  132  that is received within groove  32  of roller  30 . Accordingly, and in this embodiment, the teeth of the blade generally act upon a cutting surface in a non-linear or curved fashion as the toothed surface also has a curved configuration. 
     In yet another alternative, and referring now to  FIG. 1D , the width  130  of the blade from the non-toothed portion  34  and a toothed portion of the blade is not the same thickness along an edge  132  that is received within groove  32  of roller  30 . Accordingly, and in this embodiment, the teeth of the blade generally act upon a cutting surface in a non-linear fashion as the saw blade is reciprocated within a range of motion and the teeth are acting upon a cutting surface. 
     In addition, and in accordance with one non-limiting exemplary embodiment of the present invention the stroke of the saw blade is approximately 4 inches which has been found to be suitable for tree limb cutting operations. Of course, strokes greater or less than 4 inches are considered to be within the scope of exemplary embodiments of the present invention. 
     In an alternative exemplary embodiment, the piston may be spring biased into one of the positions illustrated in  FIGS. 5A-5D  such that one of the valves  42  or  46  is open at an initial starting point and movement to the next position will be caused by the piston overcoming the spring force as well as the gas pressure on one side of the piston. In another exemplary embodiment, a spring biasing member may be positioned on either side of the piston wherein one spring biasing force is greater than the other to maintain one of the positions illustrated in  FIGS. 5A-5D  such that one of the valves  42  or  46  is open at an initial starting point. 
     Referring now to  FIGS. 9A-11B , a pneumatically powered pole saw  10  constructed in accordance with an alternative embodiment of the present invention is illustrated. Here, referring to  FIGS. 9B and 10B  and in order to provide fluid communication between the source of compressed gas and chamber  40  a reciprocating valve  132  is provided to allow selective fluid communication between the source of compressed gas and chamber  40  via a conduit  134 . In one non-limiting exemplary embodiment the reciprocating valve is a Humphrey Products TAC Valve (See  FIGS. 10A and 10B ). One non-limiting description of a Humphrey Valve is found in U.S. Pat. No. 6,488,050 the contents of which are incorporated herein by reference thereto. When the reciprocating valve is in a first position (See  FIGS. 9B and 10B ), a first outlet  136  of reciprocating valve is in fluid communication with a fluid inlet  138  of reciprocating valve which is in fluid communication with an inlet conduit  139  which is in fluid communication with the source of compressed gas to allow fluid communication between the source of compressed gas and chamber  40 . 
     Alternatively, and as illustrated by the dashed lines in  FIG. 9A  as well as in  FIGS. 10A and 11A , when the reciprocating valve is in a second position, the first outlet  136  restricts fluid communication between the source of compressed gas and chamber  40  and chamber  40  is in fluid communication with the atmosphere so that the gas in chamber  40  may be released via opening a first check valve  140  disposed on conduit  134  to allow the cutting blade to travel to the second position. In still another embodiment, the first check valve is disposed proximate to chamber  40 . Accordingly, and when the reciprocating valve is in the second position, chamber  40  via first check valve  140  allows the fluid in chamber  40  to be released to the atmosphere. 
     Referring back to  FIGS. 9A and 10A  and in order to provide fluid communication between the source of compressed gas and chamber  38  a reciprocating valve  132  is provided to allow selective fluid communication between the source of compressed gas and chamber  38  via a conduit  142 . When the reciprocating valve is in a second position (See  FIGS. 9A and 10A ), a second outlet  144  of reciprocating valve is in fluid communication with the fluid inlet  138  of reciprocating valve which is in fluid communication with the inlet conduit  139  which is in fluid communication with the source of compressed gas to allow fluid communication between the source of compressed gas and chamber  38 . 
     Alternatively, and as illustrated by the dashed lines in  FIG. 9B  as well as in  FIGS. 10B and 11B , when the reciprocating valve is in a first position, the second outlet  144  restricts fluid communication between the source of compressed gas and chamber  38  and chamber  38  is in fluid communication with the atmosphere so that the gas in chamber  38  may be released via opening a second check valve  146  disposed on conduit  142  to allow the cutting blade to travel to the first position. In one non-limiting exemplary embodiment, the second check valve is disposed proximate to chamber  38 . Accordingly, and when the reciprocating valve is in the first position, chamber  38  via second check valve  146  allows the fluid in chamber  38  to be released to the atmosphere. 
     In accordance with an alternative embodiment of the present invention and in order to move the cutting blade in the first cutting direction, the reciprocating valve  132  is in the first position (e.g. gas supplied from source to chamber  40 ) and the second check valve  146  is opened (e.g. gas vented from chamber  38 ). Similarly, and in order to move the cutting blade to the second cutting direction the reciprocating valve  132  is in the second position (e.g. gas supplied from source to chamber  40 ) and the first check valve  140  is opened (gas vented from chamber  40 ). 
     In order to provide the movement between the first and second positions of the reciprocating valve  132  an actuator  148  is disposed within the reciprocating valve wherein movement oft he actuator  148  causes the reciprocating valve to move between the first and second positions (See  FIGS. 9A-10B ). In order to effect the movement of the actuator an assembly  150  is slidably mounted in the head member. The assembly also has a pair of fixedly secured stops  152  and  154  wherein a portion  156  of the cutting blade is slidably received upon the assembly. As the cutting blade traverses in the first cutting direction the portion  156  of the cutting blade will contact stop  152  and cause the assembly  150  to move and contact the actuator causing movement of the reciprocating valve to the second position causing first check valve  140  to open thus, the cutting blade will then traverse in the second cutting direction wherein portion  156  will contact stop  154  and cause the assembly to move and contact the actuator causing movement oft he reciprocating valve to the first position causing second check valve to open thus, the cutting blade will then traverse to the first cutting position. This reciprocal movement of the cutting blade will continue until the source of gas is no longer fluidly coupled to the inlet  132  of the reciprocating valve. 
     As illustrated in  FIGS. 9A and 9B , the assembly further comprises a main rod member  158  for slidably receiving the portion  156  of the cutting blade and a pair of contact members  160  and  162  each fixedly secured to the main rod member  158 . Moreover, the actuator comprises a pair of contact sides  164  and  166  (See  10 A and  10 B) associated with the pair of contact members  160  and  162  wherein contact member  160  contacts contact side  164  when the portion  156  of cutting blade makes contact with stop  154  causing assembly to move in the second cutting direction, and similarly, contact member  162  contacts contact side  166  when the portion  156  of cutting blade makes contact with stop  152  causing assembly to move in the first cutting direction. It being understood that the pair of contact members  160  and  162  are not fixedly secured to the contact sides  164  and  166  oft he actuator such that when contact member  160  is in contact with contact side  164  a spaced relationship or gap exists between contact member  162  and contact side  166 . Similarly, when contact member  162  is in contact with contact side  166  a spaced relationship or gap exists between contact member  160  and contact side  164 . 
     In one non-limiting alternative embodiment of the present invention a pair of biasing members  153  and  155  disposed proximate to stops  152  and  154  provides portion  156  to be biased in the opposite direction when portion  156  makes contact with stop  152  or  154 . It being understood that biasing members  153  and  155  are disposed on the side opposite to contact surface between portion  156  of and respective stop  152  or  154 . Referring to  FIG. 9A , when portion  156  makes contact with stop  152  assembly moves to the first cutting direction and portion  156  is subsequently biased to the second cutting direction due to the force provided by biasing member  153 . Similarly, referring to  FIG. 9B , when portion  156  makes contact with stop  154  assembly moves to the second cutting direction and portion  156  is subsequently biased to the first cutting direction due to the force provided by biasing member  155 . 
     Referring to  FIGS. 9A-11B  operation of an alternative embodiment of the present invention is illustrated. It being understood that  FIGS. 11A and 11B  illustrate check valves  140  and  146  in a venting position ( FIG. 11B ) wherein the gas from the piston chambers  38 ,  40  moves the diaphragm  178  and in a supply position ( FIG. 11A ) wherein compressed gas is supplied via inlet  176  and the same moves the diaphragm  178  to cover the valve seat  180  and prevent fluid communication to outlet  184 . In other words the configurations of valve  140  and  146  are similar thus, two figures are used to show the two positions of the two valves each being in selective fluid communication with either side of the piston chamber. It being further understood that outlets  184  of valves  140  and  146  are open to atmosphere to allow for unimpeded movement of the saw blade by the alternating supply of the compressed gas to the piston chambers at either side oft he movable piston. In accordance with an exemplary embodiment, the diaphragm  178  is constructed out of a resilient pliable material such as rubber or equivalents thereof such that the same can be moved by the gas from chambers  38  and  40  or the supply inlet  176 .  FIG. 9A  illustrates the saw blade moved in the first cutting direction  157 . During the traverse from the second cutting direction (opposite to arrow  157 ) to the first cutting direction reciprocating valve  132  is in the first position (See  FIG. 10B ) wherein second check valve  146  is open ( FIG. 11B ) thereby venting gas from chamber  38  to the atmosphere while first outlet  136  is in fluid communication with inlet  138  allowing fluid communication between the source of compressed gas and chamber  40  via check valve  140  ( FIG. 11A ) thus piston  19  and the saw blade travel in the first cutting direction. It being understood that in order to effect movement towards the first cutting direction the second outlet  144  is closed to conduit  142  and the first outlet is in fluid communication with conduit  134  since a first seal  168  is seated within a first seat  170  thereby opening first outlet  136  thus, causing conduit  134  to be in fluid communication with chamber  40 . Similarly, a second seal  172  is unseated from a second seat  174  thereby sealing second outlet  144  thus, causing conduit  146  to be closed to chamber  38  while chamber  38  is open to atmosphere via second check valve  146  (FIG. 
     Referring now to  FIGS. 9B and 11B , second check valve  146  is in an un-actuated position ( FIG. 11B ) configured to release gas from chamber  38  to the atmosphere when compressed gas is not entering through a conduit inlet  176  thereby causing a diaphragm  178  to not close against a valve seat  180  so that compressed gas from chamber  38  via piston passage  182  may vent directly to the atmosphere through an atmosphere outlet  184  instead of venting through the entire length of conduit  142 . Moreover, the pressure caused by the piston travelling in the direction of arrow  157  from the position in  FIG. 9B  to the position in  FIG. 9A  causes the diaphragm  178  in valve  146  to move up to the position illustrated in  FIG. 11B . This is particularly advantageous because allowing the compressed gas to vent from chamber  38  more quickly allows less back-pressure to retard the movement of the piston  18 . Similarly, referring to  FIGS. 9B and 11A  and as the blade travels in a direction opposite to arrow  157 , first check valve  140  is in an actuated position ( FIG. 11A ) configured to supply compressed gas to chamber  40  through the conduit inlet  176  thereby causing diaphragm  178  to close against valve seat  180  and diaphragm  178  has a peripheral configuration so that compressed gas may be supplied to chamber  40  via piston passage  182  and as illustrated by the arrows in  FIG. 11A  since the compressed gas forces the diaphragm against valve seat  180 . 
     In one non-limiting alternative embodiment of the present invention first and second check valves  140 ,  146 , are disposed proximate to chambers  40 ,  38 , respectively, in order maintain the least amount of back pressure as possible between supplying and venting the compressed gas to chambers  38  and  40 . 
     Referring now to  FIGS. 9B and 10A  movement of the saw blade in the second cutting direction opposite to arrow  157  is illustrated. During the traverse from the first cutting direction to the second cutting direction reciprocating valve  132  is in the second position (See  FIG. 10A ) wherein first check valve  140  is open ( FIG. 11B  e.g., no gas provided to inlet  176 ) thereby venting gas from chamber  40  to the atmosphere while second outlet  144  is in fluid communication with inlet  138  allowing fluid communication between the source of compressed gas and chamber  38  via valve  146  in the position illustrated in  FIG. 11A  thus piston  18  and the saw blade travel in the second cutting direction. It being understood that in order to effect movement towards the second cutting direction the first outlet  136  is closed to conduit  134  and the second outlet  144  is in fluid communication with conduit  142  since the second seal  172  is seated within the second seat  174  thereby opening second outlet  144  thus, causing conduit  142  to be in fluid communication with chamber  38 . Similarly, the first seal  168  is unseated from the first seat  170  thereby sealing first outlet  136  thus, causing conduit  134  to be closed to chamber  40  while chamber  48  is open to atmosphere via first check valve  140 . 
     Referring now to  FIGS. 9A and 11B , and as the blade moves in the second cutting direction, first check valve  140  is in an un-actuated position configured to release gas from chamber  40  to the atmosphere when compressed gas is not entering through the conduit inlet  176  thereby causing the diaphragm  178  to not close against the valve seat  180  so that compressed gas from chamber  40  via piston passage  182  may vent directly to the atmosphere through an atmosphere outlet  184  instead of venting through the entire length of conduit  134 . This is particularly advantageous because allowing the compressed gas to vent from chamber  40  more quickly allows less back-pressure to retard the movement of the piston  18 . Similarly, referring to  FIGS. 9A and 11A , second check valve  146  is in an actuated position configured to supply compressed gas to chamber  38  through the conduit inlet  176  thereby causing diaphragm  178  to close against valve seat  180  so that compressed gas may be supplied to chamber  38  via piston passage  182 . 
     In accordance with an alternative embodiment of the present invention, this reciprocal movement of cutting blade  12 , piston  18 , reciprocating valve  132  and assembly  150  will continue until the source of compressed gas released into the inlet conduit  139  in fluid communication with inlet  138  of reciprocating valve ceases. 
     Referring now to  FIGS. 9A and 9B  an alternative embodiment of the present invention is illustrated. Here a frame portion  186  comprises a stop member  188  secured to the end of the frame and extending outward toward the end of the cutting blade  12 . Stop member  188  defines a stop for a limb that is being cut by the pole saw. For example, and as the blade is drawn towards the stop the teeth of the blade will engage the limb and apply a downward force to the limb which in turn may cause the head member to be drawn upward or in an opposite direction to the force being applied to the limb as the blade travels down towards the stop member. Accordingly, and in order to impart the cutting force to the limb in a downward stroke of the blade the stop member provides a surface to receive a portion of the limb on as the blade travels downward towards the stop member. 
     While the invention has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Technology Category: b