referring now to fig1 there is shown a horizontal band saw machine which is generally designated by the numeral 1 and comprises a box - like base 3 and a saw head assembly 5 which is conventionally movable toward and away from the base 3 . the saw head assembly 5 includes a driving wheel 7 and a driven wheel 9 having shafts 11 and 13 , respectively , around which an endless band saw blade 15 is trained so that it may be driven to make a cutting action when the driving wheel 7 is power driven . the band saw blade 15 is slidably held or guided with its cutting edge faced downwardly by a pair of guide assemblies 17 and 19 which are fixed to guide arms 21 and 23 , respectively , and are adjustably held by a beam member 25 which is fixed at the upper portion of the saw head assembly 5 . a work - table 27 is mounted on the base 3 so that a material m to be cut may be placed thereon . a vise assembly 29 having a fixed jaw 29f and a movable jaw 29m is also mounted on the base 3 to hold the material m to be cut . also , the saw head assembly 5 is pivotally connected to the base 3 by means of a hinge pin 31 and arranged to be raised and lowered relative to the base 3 by a hydraulic motor 33 of a cylinder type having a piston and rod 35 . however , the saw head assembly 5 is so arranged as to be vertically raised away from and lowered toward the base 3 along a vertical guide post or posts by a hydraulic motor or other means , as will be disclosed hereinafter . in the above described arrangements , when the saw head assembly 5 is lowered from its raised position shown by the imaginary lines in fig1 the band saw blade 15 which is rotating around the driving and driven wheels 7 and 9 in the saw head assembly 5 , will be fed into the material m . the material m is held by the vise assembly 29 on the work - table 27 . also , the material m to be cut , which is shown as a round bar in fig1 is horizontally fed on the work - table 27 into the cutting position . material m is fed usually forwardly from the backside of the horizontal band saw machine 1 after the band saw blade 15 has been raised by the saw head assembly 5 to its upper limit on completion of each cutting cycle . referring to fig2 a and 2b , in order to theoretically illustrate the cutting action in the horizontal band saw machine 1 , there is shown a tooth of the band saw blade 15 running in the x direction and being fed in the y direction , to cut the material m . as shown fig2 a , it will be understood that the cutting resistance r of the band saw blade 15 can be taken as a vector r which is resolved into a transversal component rt in the running direction of the band saw blade 15 and a normal component rn in the feeding direction of the blade . as to any type of horizontal band saw machine , the cutting rate η is expressed as follows : where s is cross - sectional cut area of the material m to be cut , t is time , l is cross - sectional cut length of the material m , vf is feeding amount of the band saw blade 15 into the material m and vt is feeding speed of the blade . where a is a constant of proportion , w is an amount of wear or abrasion of the band saw blade 15 and b ( w ) is a function of the amount of wear or abrasion of the blade . thus , by substituting the equation ( 1 ) for the equation ( 2 ), the following equation is obtained : furthermore , since the cutting resistance r of the band saw blade 15 in cutting the material m can be resolved into the transversal component rt and the normal component rn as shown in fig2 a , the following equation is obtained : ## equ1 ## from the above description , it will be understood that the cutting resistance r can be obtained by detecting the transversal component rt and the normal component rn of the cutting resistance . also , the feeding of the band saw blade 15 into the material m to be cut can be controlled according to the obtained cutting resistance r . however , in order to more simply control the feeding of the band saw blade 15 according to only either of the transversal component rt or the normal component rn of the cutting resistance η , the equation ( 3 ) can be changed as follows : where at and an are constants of proportion which are experimentally obtained previously and bt ( w ) and bn ( w ) are functions of amounts of wear or abrasion which are also experimentally obtained . as is now understood from the above description , the band saw blade 15 can be fed into the material m being cut at a desired cutting rate η &# 39 ; when the transversal component rt or the normal component rn of the cutting resistance r satisfies the equation ( 5 ) or ( 6 ) in which the cutting rate η is substituted for such a desired cutting rate η &# 39 ; for the material m . thus , the band saw blade 15 can be fed at the desired cutting rate η &# 39 ; even when the cutting resistance r is increased because of the wear of the band saw blade 15 if the transversal component rt or the normal component rn is increased in proportion to the increase of the function bt ( w ) or bn ( w ) because of the wear of the band saw blade 15 so as to satisfy the equation ( 5 ) or ( 6 ). in this connection , of course the desired cutting rate η &# 39 ; can be experimentally obtained for various materials to be cut for the purpose of controlling the feeding of the band saw blade 15 . referring particularly to fig2 b , the cutting of the band saw blade 15 will be described with regard to the cutting resistance r and the wear or abrasion w during a cutting operation . in fig2 b , the cutting resistance r of the band saw blade 15 at the beginning of cutting is shown as a vector r 0 which is resolved into a transversal component rt 0 in the running direction of the band saw blade 15 and a normal component rn 0 in the feeding direction of the blade and has a direction of an angle θ 0 to the transversal component rt 0 . also , the cutting resistance r of the band saw blade 15 after having been more or less worn is shown as another vector r which is resolved into a transversal component rt and a normal component rn and has a direction of an angle θ to the transversal component rt . as is now understood , the vector r 0 at the beginning of cutting is increased to change to the vector r and the angle θ 0 showing the direction of the vector r 0 is changed to the angle θ showing the direction of the vector r . thus , the angle θ of the vector r can be obtained by detecting the transversal component rt and the normal component rn and based upon the following equation : also , if the magnitude and the direction shown by the angle θ of the vector of the cutting resistance r is previously experimentally obtained , the function b ( w ) of the equation ( 3 ) can be expressed as follows : where c ( θ ) is a function of the angle θ showing the increase of the cutting resistance r because of the wear w of the band saw blade 15 . thus , the equation ( 3 ) can be transformed as follows : from the above description , it will be understood that the band saw blade 15 can be fed into the material m to be cut at a desired cutting rate η &# 39 ; when the cutting resistance r satisfies the equation ( 9 ) in which the cutting rate η is substituted for such a desired cutting rate η &# 39 ; for the material m . thus , the band saw blade 15 can be fed at the desired cutting rate η &# 39 ; even when the cutting resistance r is increased because of the wear of the band saw blade 15 if the cutting resistance r is increased in proportion to the increase of the function c ( θ ) because of the wear of the band saw blade 15 so as to satisfy the equation ( 9 ). as has been described hereinbefore , the desired cutting rate η &# 39 ; can be experimentally obtained for various materials to be cut for the purpose of controlling the feeding of the band saw blade 15 . referring now to fig3 there is shown a first embodiment of the present invention for feeding the band saw blade 15 . it will be seen that the saw head assembly 5 carrying the band saw blade 15 is raised and lowered by the piston and rod 35 of the hydraulic motor 33 around a hinge pin or along a guide post or posts . the hydraulic motor for raising and lowering the saw head assembly 5 is provided with an upper chamber 33u and a lower chamber 33l divided from each other by the piston and rod 35 . the lower chamber 33l of the hydraulic motor 33 is connected to a hydraulic source 37 by a passage 39 which is connected to a relief valve 43 through a passage 41 . relief valve 43 is connected to the hydraulic tank t and is so arranged as to control the hydraulic pressure p 1 of the lower chamber 33l . the upper chamber 33u of the hydraulic motor 33 is also connected to the hydraulic source 37 by a passage 45 which is connected to an electric relief valve 49 through a passage 47 . the electric relief valve 49 is connected to the hydraulic tank t and is so arranged as to be driven by a motor 51 to control the hydraulic pressure p 2 of the upper chamber 33u . thus , the hydraulic pressure p 1 of the lower chamber 33l and the hydraulic pressure p 2 of the upper chamber 33u of the hydraulic motor 33 can be controlled by the electric relief valve 43 and the relief valve 49 , respectively , to control the motion of the saw head assembly 5 and therefore the feeding of the band saw blade 15 . also , it will be understood that the weight or gravity of the saw head blade assembly 5 will act as a feeding force for urging the saw head assembly 5 to feed the band saw blade 15 into the material m to be cut , but the feeding force will be determined by the pressures p 1 and p 2 of the lower and upper chambers 33l and 33u , respectively , of the hydraulic motor 33 . the action of the hydraulic motor 33 controlling the motion of the saw head assembly 5 and the feeding of the band saw blade 15 will be theoretically described with the area of the piston and rod 35 to be pressurized and the weight of the saw head assembly 5 expressed as ar and we , respectively . firstly , the pressure p 1 of the lower chamber 33l of the hydraulic motor 33 is expressed as follows : thus , when the relief valve 49 is set to the pressure p 1 , and the pressure p 2 of the upper chamber 33u of the hydraulic motor 33 is zero , the weight we of the saw head assembly 5 and the pressure p 1 of the lower chamber 33l of the hydraulic motor 33 are balanced with each other and therefore the saw head assembly 5 will not be lowered to feed the band saw blade 15 into the material m to be cut . in order to feed the band saw blade 15 into the material m to be cut with a desired cutting resistance r &# 39 ;, the electric relief valve 49 has to be controlled to keep the hydraulic pressure p 2 of the upper chamber 33u as follows : thus , the feeding force f for feeding the band saw blade 15 into the material m to be cut is expressed as follows : by substituting the equations ( 10 ) and ( 11 ) for the equation ( 12 ), the following equation can be obtained : as will be now understood from the above description , cutting resistance r &# 39 ; will satisfy the equation ( 9 ) to feed the band saw blade 15 into the material m being cut at the desired cutting rate η &# 39 ;. in order to detect the normal component rn of the cutting resistance r described hereinbefore with reference to fig2 a and 2b , load detecting means 53 such as pressure elements are disposed at the guide assemblies 17 and 19 in such a manner as to detect the cutting resistance or reaction urged to the back of the band saw blade 15 during cutting operation . the load detecting means 53 is so arranged as to transmit the detected normal component rn of the cutting resistance r to a computing processing unit 55 which is connected to a pressure controlling means 57 for controlling the motor 51 for the electric relief valve 49 . also , in order to detect the transversal component rt of the cutting resistance r , a torque detecting means 59 is provided between the shaft 11 of the driving wheel 7 which drives the band saw blade 15 and the motor 61 which drives the driving wheel 7 . the torque detecting means 59 is so arranged as to transmit the detected transversal component rt of the cutting resistance r to the computing processing unit 55 . the computing processing unit 55 is programmed with the computations based upon the equations ( 4 ), ( 7 ) and ( 9 ), and it is stored with the desired cutting rate η &# 39 ; which is predetermined according to the nature of the material m to be cut and the constant of proportion a and the function c ( θ ) of the equation ( 9 ) which are experimentally predetermined . the computing processing unit 55 is so arranged as to obtain the actual cutting resistance r and the angle θ showing the direction of the vector of the cutting resistance r based upon the equations ( 4 ) and ( 7 ), respectively , and according to the transversal and normal components rt and rn of the cutting resistance r . as has been described hereinbefore , the transversal and normal components rn and rt of the cutting resistance are detected and transmitted to the computing processing unit 55 by the load detecting means 53 and the torque detecting means 59 , respectively . the computing processing unit 55 is also so arranged as to obtain the desired cutting resistance r &# 39 ; based upon the equation ( 9 ) and according to the obtained angle θ showing the direction of the vector of the cutting resistance r and the function c ( θ ) and the constant of proportion a which are both previously stored . furthermore , the computing processing unit 55 is so arranged as to compare the obtained cutting resistance r and the obtained desired cutting resistance r &# 39 ; and then direct the pressure controlling means 57 to keep the cutting resistance r and the desired cutting resistance r &# 39 ; equal to each other . the pressure controlling means 57 is so arranged as to control the electric relief valve 49 by means of the motor 51 according to the directional signals given by the computing processing unit 55 so as to keep the pressure of the upper chamber 33u of the hydraulic motor 33 at p 2 = r &# 39 ;/ ar , expressed as the equation ( 11 ). in other words , the pressure controlling means 57 is so arranged as to control the hydraulic motor 33 by means of the electric relief valve 49 to lower the saw head assembly 5 to feed the band saw blade 15 in the material m to be cut with the upper chamber 33u of the hydraulic motor 33 kept at the pressure p 2 = r &# 39 ;/ ar . as has been described , the band saw blade 15 is fed into the material m to be cut by the hydraulic motor 33 by means of the saw head assembly 5 with the hydraulic pressure of the upper chamber 33u of the hydraulic motor 33 kept at p 2 = r &# 39 ;/ ar expressed as the equation ( 11 ) according to the present invention . when the hydraulic pressure of the upper chamber 33u of the hydraulic motor 33 is kept at p 2 = r &# 39 ;/ ar , the band saw blade 15 is fed into the material with a feeding force which is equal to the desired cutting resistance r &# 39 ; as is expressed by the equation ( 13 ). as will be now understood , when the feeding force is equal to the desired cutting resistance r &# 39 ;, the bandsaw blade 15 is fed into the material m to be cut at the desired cutting rate η &# 39 ; with the equation ( 9 ) satisfied . referring to fig4 there is shown a second embodiment of the present invention which is more or less similar to the first embodiment shown in fig3 . for the purpose of simplification , elements common to the first and second embodiments will be given the same reference numerals and will not be described in detail . in the second embodiment , the saw head assembly 5 is so arranged as to be raised by the hydraulic motor 33 when the hydraulic fluid is supplied into the lower chamber 33l of the hydraulic motor 33 and be lowered by its own weight or gravity when the hydraulic fluid is exhausted from the lower chamber 33l . the lower chamber 33l of the hydraulic motor 33 is connected for drainage to the hydraulic tank t by means of an adjustable flow control valve 63 such as a metering valve which is controlled by a motor 51 &# 39 ; which , in turn is controlled by a flow controlling means 57 &# 39 ;. thus , the feeding speed of the band saw blade 15 cutting into the material m to be cut is controlled by the hydraulic fluid drained from the lower chamber 33l of the hydraulic motor 33 through the adjustable flow control valve 63 which is controlled by the flow controlling means 57 &# 39 ; through the motor 51 &# 39 ;. in the above described arrangement , the hydraulic pressure p 1 of the lower chamber 33l of the hydraulic motor 33 is expressed as follows : where we , ar and rn are the weight of the saw head assembly 5 , the area of the piston and rod 35 to be pressurized and the normal component of the cutting resistance r , respectively , as expressed hereinbefore . by transforming the equation ( 14 ), the following equation is obtained : thus , it will be understood that the normal component rn of the cutting resistance r can be obtained by detecting the hydraulic pressure p 1 of the lower chamber 33l of the hydraulic motor 33 . a pressure detecting means 65 is connected to the lower chamber 33l of the hydraulic motor 33 for detecting the hydraulic pressure p 1 and obtaining the normal component rn of the cutting resistance r . also , in order to transmit the hydraulic pressure p 1 of the lower chamber 33l of the hydraulic motor 33 , the pressure detecting means 65 is connected to the computing processing unit 55 which functions in more or less the same manner as in the first embodiment shown in fig3 . the computing processing unit 55 is connected to the flow controlling means 57 &# 39 ; to give directional signals thereto as will be described hereinafter , and it is connected to the torque detecting means 59 which operates in the same manner as in the first embodiment . as has been described with regard to the first embodiment , the torque detecting means 59 is provided between the shaft 11 of the driving wheel 7 and the motor 61 in order to detect and transmit to the computing processing unit 55 the transversal component rt of the cutting resistance r . the computing processing unit 55 in this embodiment is programmed with the computations based upon the equations ( 4 ), ( 7 ), ( 9 ) and ( 15 ), and stored therein are the desired cutting rate η &# 39 ; and the constant a of proportion and the function c ( θ ) of the equation ( 9 ) in all the same manner as the first embodiment shown in fig3 . the computing processing unit 55 is so arranged as to firstly obtain the normal component rn of the cutting resistance r based upon the equation ( 15 ) and according to the hydraulic pressure p 1 of the hydraulic motor 33 and then obtain the actual cutting resistance r based upon the equation ( 4 ) and according to the obtained normal component rn and the transversal component rt . as has been described hereinbefore , the hydraulic pressure p 1 of the lower chamber 33l of the hydraulic motor 33 and the transversal component rt of the cutting resistance r are detected and transmitted to the computing processing unit 55 by the pressure detecting means 65 and the torque detecting means 59 , respectively . the computing processing unit 55 is also so arranged as to obtain the angle θ showing the direction of the vector of the cutting resistance r based upon the equation ( 7 ) and according to the obtained normal component rn and the given transversal component rt of the cutting resistance r . furthermore , the computing processing unit 55 is so arranged as to obtain the desired cutting resistance r &# 39 ; and then compare the obtained cutting resistance r and the obtained desired cutting resistance r &# 39 ; with each other so as to give directional signals to the flow controlling means 57 &# 39 ; in the same manner as described in the first embodiment . the flow controlling means 57 &# 39 ; is arranged to control the adjustable flow control valve 63 by means of the motor 51 &# 39 ; according to the directional signals given by the computing processing unit 55 . the flow controlling means 57 &# 39 ; is equivalent to the pressure controlling means 57 in the first embodiment , but it is designed to control the flow of the hydraulic fluid draining out of the lower chamber 33l of the hydraulic motor 33 by means of the adjustable flow control valve 65 in order to control the feeding speed of the band saw blade 15 expressed in the equation ( 2 ). in the above described arrangement , it will be understood that the cutting resistance r of the equation ( 2 ) is controlled correspondingly when the feeding speed vt of the band saw blade 15 of the same equation is controlled by the flow controlling means 57 &# 39 ; by means of the flow control valve 63 . also , the flow controlling means 57 &# 39 ; will control the feeding speed vt of the band saw blade 15 to keep the cutting resistance r equal to the desired cutting resistance r &# 39 ; according to the directional signals given by the computing processing unit 55 which directs the flow controlling means 57 &# 39 ; in the same manner as described in the first embodiment . thus , it will be understood that the cutting rate η is kept uniform or constant when the cutting resistance r is kept equal to the desired cutting resistance r &# 39 ; by the flow controlling means 57 &# 39 ;, since the equation ( 9 ) is satisfied . referring to fig5 there is shown a third embodiment of the present invention which is very similar to the first embodiment shown in fig3 and is also more or less similar to the second embodiment shown in fig4 . for the purpose of simplification , elements common to the first and second embodiments will be given the same reference numerals in the third embodiment and will not be described in detail . this third embodiment is different structurally from the first embodiment only in that a wear detecting means 67 is employed instead of the torque detecting means 59 so as to detect the wear or abrasion of the bandsaw blade 15 . the wear detecting means 67 is connected to the computing processing unit 55 , which is more or less the same as the first and second embodiments so as to transmit the detected wear of the band saw blade 15 to the the computing processing unit . elements other than the wear detecting means 67 of the third embodiment are the same as those of the first embodiment , although the computing processing unit 55 is arranged in a more or less different manner . to be brief , the third embodiment is different from the first embodiment in that the hydraulic pressure p 2 of the upper chamber 33u of the hydraulic motor 33 is controlled according to the wear w of the band saw blade 15 detected by the wear detecting means 67 and based upon the equation ( 6 ). the wear detecting means 67 will be easily designed to the purpose by those skilled in the art so as to detect the wear w of the band saw blade 15 during a cutting operation . for instance , the wear detecting means 67 may be , as shown in fig6 a magnetic detecting means constructed of a coil 69 and a core 71 which may be connected with an average circuit 73 , and it can be provided on the upper stretch of the band saw blade 15 between the driving and driven wheels 7 and 9 . in the third embodiment , the computing processing unit 55 is programmed with the computation of only the equation ( 6 ), and stored therein are the desired cutting rate η &# 39 ; and the constant of proportion an and the function bn ( w ) of the equation ( 6 ). the desired cutting rate η &# 39 ; is predetermined for various materials to be cut in the same manner as the first and second embodiments , and the of proportion an and the function bn ( w ) are experimentally predetermined . the computing processing unit 55 is designed to obtain the desired normal component rn &# 39 ; of the cutting resistance r based upon the equation ( 6 ) and according to the wear w of the band saw blade 15 given by the wear detecting means 67 and the desired cutting rate θ &# 39 ; and the constant of proportion an and the function bn ( w ) which are previously stored . the computing processing unit 55 is also arranged to compare the desired normal component rn &# 39 ; of the cutting resistance r obtained in the above described manner and the normal component rn which is given by the load detecting means 53 in the same manner as described in the first embodiment . furthermore , the computing processing unit 55 is so arranged in the same manner as described in the first embodiment to direct the pressure controlling means 57 to keep the normal component rn and the desired normal component rn &# 39 ; of the cutting resistance r equal to each other . the pressure controlling means 57 is arranged to control the electric relief value 49 by means of the motor 51 according to the directional signals given by the computing processing unit 55 so as to keep the pressure of the upper chamber 33u of the hydraulic motor 33 at p 2 = rn &# 39 ;/ ar in the same manner as described in the first embodiment . thus , the pressure controlling means 57 will control the hydraulic motor 33 by means of the electric relief valve 49 to feed the band saw blade 15 into the material m to be cut with the upper chamber 33u of the hydraulic motor 33 kept at the pressure p 2 = rn &# 39 ;/ ar . as is readily apparent , the band saw blade 15 is fed into the material m with a feeding force which is equal to the desired normal component rn &# 39 ; of the cutting resistance r when the hydraulic pressure of the upper chamber 33u of the hydraulic motor 33 is kept at p 2 = rn &# 39 ;/ ar . thus , it will be understood that the band saw blade 15 is fed into the material m to be cut at the desired cutting rate η &# 39 ; with the equation ( 6 ) satisfied when the feeding force is equal to the desired normal component rn &# 39 ; of the cutting resistance r . referring to fig7 there is shown a fourth embodiment of the present invention which is very similar to the second embodiment shown in fig4 and is also more or less similar to the first and the third embodiments shown in fig3 and 5 , respectively . for the purpose of simplification , elements of this fourth embodiment will be given the same reference numerals as the preceding embodiments and will not be described in detail , since all the elements are common to the preceding embodiments . the fourth embodiment is different structurally from the second embodiment only in that the wear detecting means 67 of the third embodiment is used instead of the torque detecting means 59 of the second embodiment . the wear detecting means 67 is connected to the computing processing unit 55 , which is more or less the same as the preceding embodiments , and transmits the detected wear of the band saw blade 15 to the computing process unit in the same manner as described in the third embodiment . elements other than the wear detecting means 67 of the fourth embodiment are all the same as in the second embodiment , although the computing processing unit 55 is arranged in a more or less different manner . briefly stated , the fourth embodiment is different from the second embodiment in that the feeding speed vt of the band saw blade 15 is controlled according to the wear w of the band saw blade 15 detected by the wear detecting means 67 and based upon the equation ( 6 ). in the fourth embodiment , the computing processing unit 55 is programmed with the equations ( 6 ) and ( 15 ), and stored therein are the desired cutting rate η &# 39 ; and the constant of proportion an and the function bn ( w ) of the equation ( 6 ). the desired cutting rate η &# 39 ; is predetermined for various materials to be cut and the constant of proportion an and the function bn ( w ) are experimentally predetermined in the same manner as described in the preceding embodiments . the computing processing unit 55 is arranged to firstly obtain the normal component rn of the cutting resistance r based upon the equation ( 15 ) and according to the hydraulic pressure p 1 of the hydraulic motor 33 in the same manner as described in the second embodiment . also , the computing processing unit 55 is arranged to obtain the desired normal component rn &# 39 ; of the cutting resistance r based upon the equation ( 6 ) and according to the wear w of the band saw blade 15 given by the wear detecting means 67 and the desired cutting rate η &# 39 ; and the constant of proportion an and the function bw ( w ) in the same manner as described in the third embodiment . furthermore , the computing processing unit 55 is arranged to compare the obtained normal component rn and the desired normal component rn &# 39 ; of the cutting resistance r with each other so as to give directional signals to the flow controlling means 57 &# 39 ; in the same manner as described in the second embodiment . the flow controlling means 57 &# 39 ; is arranged in the same manner as the second embodiment to control the flow of the hydraulic fluid draining out of the lower chamber 33l of the hydraulic motor 33 by means of the adjustable flow control valve 65 to control the feeding speed of the band saw blade 15 expressed in the equation ( 2 ). from the above description , it will be understood that the flow controlling means 57 &# 39 ; will control the feeding speed vt of the band saw blade 15 to keep the normal component rn and the desired normal component rn &# 39 ; of the cutting resistance r equal to each other according to the directional signals given by computing processing unit 55 in the same manner as described in the second embodiment . thus , the band saw blade 15 will be fed into the material m to be cut at the desired constant cutting rate η &# 39 ; since the normal component rn and the desired normal component rn &# 39 ; are kept equal to each other with the equation ( 6 ) satisfied . as has been far described in the above , the cutting resistance r of the band saw blade 15 is kept equal to the desired cutting resistance r &# 39 ; by controlling the feeding force or the feeding speed of the band saw blade 15 to keep the cutting rate η constant and equal to the desired cutting rate η &# 39 ; experimentally predetermined according to the present invention . thus , it will be understood the various objects described earlier hereinbefore can be accomplished according to the present invention . although a preferred form of the present invention has been illustrated and described , it should be understood that the device is capable of modification by one skilled in the art without departing from the principles of the invention herein involved . accordingly , the scope of the invention is to be limited only by the claims appended hereto .