US 2934009 A
Description (OCR text may contain errors)
April 26, 1960 J. w. BACH ETAL SHEET FEEDING AND TREATING 6 Sheets-Sheet 1 Filed Oct. 22, 1956 mm\ 'L April 9 J. w. BACH ET AL 2,934,009
SHEET FEEDING AND TREATING Filed Oct. 22, 1956 6 Sheets-Sheet 2 wciA A TTOENEY April 1960 J. w. BACH ET AL 2,934,009
SHEET FEEDING AND TREATING- Filed Oct. 22, 1956 6 Sheets-Sheet 3 Way. 3
I x .91 1 14 w 111 105 107 7.9
INVENTORS ATTORNEY April 26, 1960 J. w. BACH ETAL 2,934,009
SHEET FEEDING AND TREATING Filed Oct. 22, 1956 6 Sheets-Sheet 5 NTO .75/2/7 M/ in? B ck A TTOQNEY April 26, 1960 J. w. BACH ETAL SHEET FEEDING AND TREATING 6 Sheets-Sheet 6 Filed Oct. 22, 1956 A TTOE VEY United States Patent SHEET FEEDING AND TREATING John William Bach, Stamford, and Frederick L. Ford,
Darien, Conn., assignors to Pitney-Bowes, Inc., Stamford, Conn., a corporation of Delaware Application October 22, 1956, Serial No. 617,629
4 Claims. (Cl. 101-235) This invention relates to drive mechanisms for intermittently operating automatic rotary treating machinery for sheet-form workpieces and especially to an improved drive mechanism for postage printers.
Heretofore, in the printing of accurately placed data such as postage on each of a large number of workpieces, it has been the practice to feed the workpieces serially through a rotary printing couple including a printing drum and impression roller where each is simultaneously printed and fed forward automatically. In order that the printing or other treatment shall be properly positioned with respect to each workpiece, and especially where random size workpieces are to be provided for, the drive mechanism for the printing drum and impression roller has conveniently included clutch and declutching means for making and breaking the connection with the primary power source at appropriate times, together with arresting means for the printing drum for stopping the same in a desired home position after each printing operation ready for the next succeeding one, and a trip mechanism for initiating each printing operation of the printing drum as each new workpiece is presented at the proper location. The operation of the impression roller and printing drum are accordingly intermittent, and due to their mass, especially the mass of the latter, a
distinct shock is experienced by the mechanism at each workpieces, which device has the treating parts stopped in a home position to elfect proper registry of the treatment with each incoming workpiece, wherein the stopping and starting of such parts is effected in a smooth, gradual manner with little or no shock so that much quieter operation is achieved without reduction of the output rate.
It is a feature of the present invention that the foregoing object is effected by including in the drive train a mutilated gear meshing with another gear for driving the parts through the treating and feeding portion of each cycle, and cooperating cam and follower means for controlling the rotation of the parts during the ungeared accelerating and decelerating portions of each cycle.
In the operation of feeding and treating devices of the type previously described, and especially in connection with high speed postage printers, it has been found most convenient and effective, from the standpoints of speedy action, reliability, minimum maintenance, etc., to employ helical spring clutch means for making and breaking the drive connection for each cycle of operation. However, with the introduction of the improved drive mechanism mentioned above, the change in relative clutch hub speeds at certain times is so gradual in character that the releasing action of the clutch is somewhat less positive and instantaneous than under ordinary circumstances. Accordingly, some chatter with accompanying unnecessary wear tends to be introduced into the mechanism at this point.
In certain of its aspects, therefore, the present invention includes as an object the provision of novel release booster mechanism for cyclically operating helical spring clutch mechanisms to insure their full release at the proper instant even though departure from equality of the relative clutch hub speed would otherwise be exceedingly gradual.
Still another object of the invention is the provision of a novel improved trip mechanism for rendering the mechanism rapidly and positively responsive to tripping forces which, due to the nature of the workpieces sometimes handled, such as air mail letters, may be very light.
A further object of the invention is the provision of a trip mechanism whose operative connection with the mechanism is broken automatically when operation starts so as to avoid interference with a resetting operation even though the primary tripping element remains in tripped position.
Additional objects, features and advantages will appear as the description proceeds.
In the drawings:
Fig. 1 is a front elevation of a portion of a postage printer according to the present invention, a portion of the base casing and mechanism being broken away to illustrate the tripping and resetting mechanism, the parts of the latter being shown in solid lines in the stopped and locked position, and in dot-dash lines in the tripped posi tion;
Fig. 2 is a top plan of the base portion of the postage printer shown in Fig. 2, with the casing removed and showing in detail the drive mechanism according to the present invention; 1
Fig. 3 is an elevation of the right-hand portion of the device of Fig. 2 taken substantially on line 3--3 thereof;
Fig. 4 is a section taken substantially on line 44 of Fig. 2;
Fig. 5 is a detail section taken substantially on line 55 of Fig. 4;
Fig. 6 is a detail perspective illustrating the trip-reset mechanism and showing the parts in tripped position;
Figs. 7 to 10 are diagrammatic elevations illustrating the novel drive mechanisms of the present invention and showing the relative positions of the parts at various points in the progress of a workpiece through a printing and feeding cycle; and
Fig. 11 is a detail section taken substantially on line 1111 of Fig. 2.
Reference to the drawings, the present invention is illustrated in connection with a postage printer 21 having a base 23 and a removable meter portion 25 housed in respective casings 27 and 29. The meter portion 25 carries a cyclically operating rotary printing drum 31 which feeds forward and prints on the surface of a workpiece such as envelope E during a portion of each cycle and rotates idly during the balance. As presently shown the operating arc represents about 240 of travel and the idle rotation about 60 at either end of the operating arc. The printing drum is connected to a drive gear 32 concentric therewith (Figs. 3, 4 and 5). Mounted on the base 23 in position for cooperation with the printing drum is an impression roller 33 which is drivingly associated with the shaft 35.
Drive mechanism Improved drive means for imparting motion to shaft 35 and gear 32 are provided according to the present in- Vention and include a frame 37 having upstanding end walls 39 and 41 inwhich is journaled a main drive shaft 43. An electric motor 45 (Fig. 2) serves as the prime mover and is drivingly connected with main drive shaft 743 through an appropriate .mechanical reducing train,
here shown as toothed belt and pulley arrangement 47 providing a speed reduction of an appropriate amount 7 (shown as about 1 of the motor shaft speed).
, and is of a sizeto snugly embrace the hubs 49 and 53.
The spring 57 also has a projecting operating end portion 61 secured to a collar 63which is freely rockable on the driving hub 49 and has a stop surface 65 (Pig. The stop surface 65 is preferably adjustable and for this reason is carried on a sector member 67 which is circurnferentially adjustable about collar 63 by means of a screw 69 against which it is held by spring 71. The direction of wind of clutch spring 57 is such as to cause frictional gripping of the driving hub 49 when it is turned in the motor driven direction, i.e. clockwise when looking from the right in Figs. 2 to 4, and such as to cause release thereof when the driven hub 53 tends to move clockwise relative to the driving hub. The stop surface 65 cooperates with tripping mechanism for starting and stopping the drive to the printing drum 3-1 in a manner to be hereinafter described.
Novel intermittent drive means 73, to be more fully described hereinafter, connects the hollow shaft 55 with a hollow splined countershaft 75 and drives the latter through a predetermined program of speed ratios in a manner to be hereinafter explained, the hollow shaft 55 being rotated substantially at a uniform speed during its intermittent periods of operation and being accelerated and decelerated almost instantaneously without deleterious eifect because of its relatively modest mass. The shaft 75 is connected at one end to a gear 77 which meshes with the gear 32 on the printing drum 31 to drive the latter at speeds determined by the action of said intermittent drive means. 7
Pinned to the main shaft 43 is a gear 79 which meshes with a gear 81 on a shaft 83 rotatably supported within the hollow shaft 75. The shaft 33 drives the shaft 35 of the impression roller 33 via a connecting shaft 85 connected with the shafts 83 and 35 by means of universal joints 87 and 89 (Fig. 2) which permit the impression roller to be floatingly mounted, as well as conveniently offset from the axis of shafts 75 and 83. The ratio of gearing 79, 81 is selected to drive the impression roller at a surface speed conforming substantially to the maximum or printing surface speed of the printing drum 31 as determined by said intermittent drive means 73.
The intermittent drive means or gearing 73 includes a mutilated gear 91 on shaft 55 meshing intermittently with a gear 93 on shaft 75. Cam means arealso provided for accelerating and decelerating the shaft 75 while the mutilated gear 91 and gear 93 are out of mesh, and for holding the shaft 75 against rotation duringa fraction of the non-meshing rotation of shaft 55. Thus a cam 95 rotatable with gear 91 and engageable with a roller 97 projecting in one direction axiallj from gear 93 accelerates the gear 93 from zero to maximum speed during about 30 of travel of shaft 55 and positions the parts for proper meshing of the gears 91 and 93. At the end of the constant speed geared operation of about 210 of rotation of shaft 55, another cam 99 rotatable with gear 91 engages with a roller 101 projecting in the other direction from gear 93 to decelerate the gear 93 gradually to zero through about 30 of rotation of shaft 55.
There after concentric dwell portions 95a and 99a of cams 95 and 99 cooperate with the rollers 97 and 101 respectively to hold the gear 93 stationary for about of lrotation of shaft 55 until the beginning of another cyc e.
Each of the cams and 99 also has a guard portion, ndicated as 951; and 99b respectively, which serves durng the active period of the opposite cam to react with its own corresponding roller and, acting through the body of the gear 93, to' keep the active follower roller in close proximity to the other or active cam surface for as long as necessary to assure a smooth transition from cam to gear operation or gear to earn operation.
Trip mechanism In order that the printing mechanism shall not operate unless a workpiece such as envelope E is in exact position ready for printing, .the machine is arranged so that a printing cycle cannot initiate until tripped by a workpiece in printing position. This insures prevention of printings with the workpiece absent so that ink will not accumulate on the impression roller to offset later on the backs of subsequently printed workpieces, proper positioning of the imprint on the workpiece, and in the case of a postage printer that postage value will not be wasted inadvertently. According to the .present invention a novel trip mechanism is provided for controlling the clutch 51 and arranged to automatically disengage the same at a suitable point in every cycle of operation, namely during the period when the dwell portions 95a and 99a are holding gear 93 stationary. The arrangement is such that the clutch then remains disengaged until tripped by the next incoming workpiece E. The improved tripping mechanism is unusually light and can be positively actuated by lightweight workpieces which would normally deform easily, such as air mail letters.
Figs. 1, 2, 4, 5 and 6 particularly illustrate the trip mechanism which includes a rockable trip finger 103 arranged in the path of an incoming workpiece E, and a stop lever 105. The stop lever 105 is pivoted to the frame 37 at 107 and includes several integrally connected portions, foremost of which is the stop finger 1G9 arranged normally to lie in the path of stop surface 65 on collar 63 to interrupt motion of the stop surface 55 whereby to disconnect the clutch and bring the drive to a halt at a predetermined angular position after each rotation of shaft 55. A spring 110 is arranged to rock the stop lever 105 to the left in Fig. 4 and thus bring it into position to render the stop finger 109 operative as described. Also forming parts of the stop lever 105 are a latch arm 111, a reset arm 113 carrying a roller 114, and an actuating arm 115 for controlling the operations of portions (not shown) of the meter 25, and which form no part of the present invention.
The trip finger 103 has three positions, the first being the solid line position in Fig. 1 or unactuated position, the second being the dot-dash line position in Fig. 1 or tripped, workpiece arresting position, and the third being the noninterfering or printing position in which the finger releases the workpiece for feeding and printing and underlies the same during this operation.
The trip finger 103 is connected to a rock shaft 117, Fig. 2, which has at its opposite end a transfer lever 119 which strikes against and thereby transmits its movement to a similar lever 121 on a short rock shaft 123 mounted in the Wall 41. The other end of the rock shaft 123 carries a cranck 125 connected to a link 127 which rests against the upper surface of a control Wheel 129 on shaft 55, and which is normally urged to the right (Fig. 1) together with its crank 125 by a'spring 131. The spring 131 also serves to urge the link 127 downwarly towards the control wheel surface. The control wheel is relieved in one portion of its periphery to provide a recess indicated by reference numeral 133 for cooperation with a hook 135 of the link 127. This recess is so positioned that when the shaft 55 is in the stopped, home position seen in Fig. 1, the hook 135 will drop into the same during motion of the link to the left in Fig. 1 and under the influence of crank 125, thus placing the link at an operative tripping level. It will be noted, however, that the recess 133 is so shaped that as soon as the shaft 55 begins to rotate (counterclockwise in Fig. 1) it will immediately cam the hook 135 back to its original non-tripping level where it will be held by the control wheel periphery until the beginning of another cycle.
The lower edge of link 127 includes a tooth 137 which, when the link is drawn to the left (Fig. l) by crank 125 and lowered into tripping position, comes into contact with the operating arm 139 of a trigger element 141. The latter is pivoted on the wall 41 and has a dog 143 normally underlying the latch arm 111 of the stop lever 105, but is movable counterclockwise by action of the tooth 137 to release the latch arm 111, thereby allowing the stop lever 105 to rock under the influence of spring 110 so as to move the stop finger 109 out of the path of stop surface 65, whereby the clutch 51 may engage. It will be noted that the length of arm 111 is such that the contact point of dog 143 with arm 111 is spaced from the pivot 107 a distance several times that of the point of connection of spring 110, so that frictional resistance to withdrawal of dog 143 may be held to a minimum. A spring 145 urges the trigger element 143 towards latching position so that the dog 143 is retained in a position underlying the arm 111, or, after release, is urged against the side of arm 111 for immediate return to latching position as soon as arm 111 may be raised.
The crank 125 also carries a laterally projecting pin 147 which engages against a stop projection 149 when the crank is swung to the left in Fig. 1. This stops the movement of the trip finger 103 at the dot-dash position in Fig. 1 and arrests the workpiece E in a ready position so that the printing, when applied by drum 31, will be properly spaced relative to the leading edge. The stop projection, however, is carried on the end of a trip finger stop lever 151 which is pivoted on the wall 41 at 153. The other end of the lever 151 carries a roller 155 which is urged against a cam 157 on shaft 55 by a spring 159, thecam 157 having a short recess 161 correlated with the printing drum position and into which the roller 155 may be urged for a short period just prior to, including and subsequent to, the stopped home position of shaft 55. Thus while the shaft is stopped the stop projection 149 holds the trip finger against movement beyond the dot-dash position in Fig. 1, and after starting continues to hold until the shaft 55 has had a chance to start and turn through a small angle sufiicient to bring the printing drum 31 around to operative position. Thereupon the roller 155 is lifted to the circular periphery of the cam 157, rocking lever 151 counterclockwise to lower the stop projection 149 and permit further movement of crank 125 and hence of trip finger 103 whereby the latter may drop to clear the path of the incoming workpiece E and permit the same to move with the printing drum 31. As each cycle terminates the roller 155 again drops into the recess 161 to place the stop projection 149 in readiness for another workpiece positioning operation.
Trip reset mechanism In order that the trip mechanism may be reestablished in a condition ready for tripping the drive means for a subsequent workpiece after the completion of a printing operation, means is provided for returning certain of the parts to their set positions as an incident to the termination of each cycle. This action is brought about through the previously described reset arm 113 of stop lever 105, the former carrying roller 114 which acts as a follower for cooperating with a rest cam. This cam is designated 163 and consists of a tapered block attached to a face of cam 95 to act as an end cam. In Fig. 6 the parts are shown in tripped position with shaft 55 rotating. It will be seen that as the parts approach the stopping position, the end cam 163 will come into contact with roller 114 moving it to the right and thus rocking the stop lever clockwise against the force of spring and lifting the latch arm 111. When the latter has lifted sufficiently, dog 143 is moved thereunder to latch the same by means of spring 145 acting on trigger element 141, and the parts remain thus positioned ready for the next cycle even after the cam 163 shall have moved beyond roller 114. Return movement of the trigger element 141 is effected without interference between the operating arm 139 and the tooth 137 since, as previously explained, the initial rotative movement of shaft 55 and control wheel 129 cams the link 127 upwardly to put the tooth 137 in an inactive position at once as soon as the tripping operation is accomplished.
Full clutch release mechanism Experience has shown that when the printing drum 31 is decelerated smoothly to a stopped position, the speed ratio in the driving train is such that the overrun torque which acts on the clutch spring 57 through collar 59, normally assisting in the disengagement of the clutch when the operating end 61 is arrested, is exceedingly small and sometimes fails to achieve a complete disengagement. This may result at times in a certain amount of chatter due, no doubt, to an intermittent drive and release tendency experienced by one or more of the turns of the spring 57 which are in contact with the constantly rotating driving hub 49. To prevent this occurrence, there has been provided, according to the present invention, a booster arrangement for supplementing the overrun; torque at the release position. The means employed to this end is shown as including a clutch release roller 165 extending from one face of the collar 59, seen especially in Figs. 2, 5 and 11. Cooperating with this roller is a booster element 167 pivoted on the frame at 169 to swing towards and away from the shaft 43 in the plane of motion of the roller 165. A spring 171 urges the booster element 167 towards the roller 165, at least as far as permitted by an arm 173 of the booster which strikes against a stop 175 to prevent excessive swinging in this direction. The booster element 167 has a first sloping surface 177 which is encountered by the roller 165 as the driven hub 53 approaches home position while being driven by the driving hub 49 by means of clutch spring 57. The roller 165, by virtue of this surface 177, cams the booster element 167 to one side, i.e. to the left as seen in Fig. 11, thus stressing the spring 171 to provide a driving force for the booster element. Thereafter, as stopping is about to take place, the roller 165 passes over into contact with an oppositely sloped surface 179 of the booster element. This surface, under the driving force of spring 171, cams the roller 165 somewhat further in its direction of progression until stop surface 65 is fully engaged with stop finger 109, and then urges the roller 167 and the collar 59 to which it is firmly connected through a small additional increment of rotation just sufiicient to insure adequate expansions of clutch spring 57 and its complete functional release from driving hub 49, the parts finally being found in stopped position approximately as shown in broken lines in Fig. 11, awaiting the initiation of another cycle.
Operation A cycle is commenced with the parts arranged as shown in solid lines in Fig. 1 and broken lines in Fig. 7. An approaching workpiece E, normally fed by means not shown in the drawings, approaches the trip finger 103 and moves the same to the solid line position in Fig. 7. The finger 103 is stopped in this position by the striking of pin 147, carried by crank 125, against the stop projection 149, thus arresting the workpiece in ready position. This motion of the finger 103 also acts via tooth 137 on linkj 127,1 1: triggerelement 141, to release'the latch am 111 of'stop lever 105, whereby spring 110 rocks the -cert with the continuously rotating driving hub 49 and 'main driving shaft 43. The initial rotation of hub 53 causes gradual acceleration of the gear 93 and shaft 75 'via'cam 95 and roller 97 until'the shaft 75 reachesoper- -ating speed and gear 91 meshes with gear 93 to commence the feeding and printing operation, the printing drum meantime, via gearing 77, 32, being rotated until it reaches the workpiece-engaging position shown in Fig. 8. Also, in Fig. 8 the trip finger 103 has been'shown in lowered position where it no longer interferes with the progress of the workpiece E. This position of the trip finger is reached inasmuch as the cam 157 has now progressed far enough to actuate lever 151 and thereby lower stop projection 149 which permits the workpiece E to push the finger 103 out of itsway.
Fig. 9 shows the parts as the printing continues at constant speed due to the drive of gears 91, 93. 7 Either sometime towards the end of this phase the printing drum 31 feeds the workpiece E out to a point-such that its trailing edge clears the finger 103, or else, in the case of longer workpieces, the printing drum 31 comes to the end of its feeding operation, as seen in Fig. 10, and momentum or subsequent feeding means, not shown, carry the workpiece past the finger 103 whereby the latter is released to swing back to its initial untripped position under the influence of spring 131 acting on link 127 and crank 125.
As seen in Fig. the return of finger 103 as just described has been accomplished. The feeding operation of the printing drum 31 has been completed and the gears 91 and 93 are about to unmesh. At this moment 'the cam 99 comes into play, starting to resist the forward motion of roller 101, and thereafter gradually decelerating the motion of gear 93 and consequently of the printing drum 31 until the same reaches home position ready to stop. As home position is approached the resetting action of cam 163 acting against reset roller 114 takes place, moving the lever 105 to its stopping position wherei nstop finger 109 blocks the path of stop surface 65 disabling clutch 51 and bringing the parts to rest in the home position shown in Fig. 7, ready for the approach of another workpiece. The booster element 167 also comes into play and acts against roller 165 to insure a full and positive release of clutch 51 until such time as it is intended to be active again.
The dog 143 of trigger element 141, meanwhile, has been allowed to return to its latching position because of the raising of latch arm 111 of stop lever 105 due to the action of rest cam 163. This unlocks the dog and permits the spring 145 to act, returning the parts to ready position. At about the same time the control wheel 129 approaches its home position restoring a state of affairs wherein the locus of travel of tooth 137 on link 127 will be such as to make contact with the operating arm 139 of the trigger element 141 whenever the trip finger 103' is actuated by another workpiece.
The described cycle of events is similarly repeated,
therefore, each time a workpiece is presented to the machine.
Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.
What is claimed is:
1. In an automatic rotary feeding and treating mechanism for sheet-form workpieces, drive means including a part intermittently rotatable and stopped once each rotation at a predetermined home position; trip means for initiating each cycle including a trip member actuated by an incoming workpiece; a link connected to saidtrip member and carrying projecting means which, when imoved in anoperative path, makes connection withtlie other parts of the trip mechanism; and a control wheel rotating with said rotating part, said link being urged 'ragainst said control wheel, and sa d control wheel and link having cooperating configurations such that said projecting means is prevented from moving in an opera- 'tive path except when the rotating part is in said home position.
V 2. Intermittent rotary drive means comprising a first 'or driving rotating part and a second or driven rotating part rotated once for each rotation of said driving part; a mutilated gear on said first part meshing with a driven gear on said second part during amajor portion of the rotation of said first part; a cam contacting member .extending axially from each face of said driven gear; an [acclerating cam on one side of and rotatable with said mutilated gear and in position to coact with one of said cam contacting members for accelerating said second part and its gear gradually and smoothly to a tooth speed common with that of said mutilated gear just prior'to meshing of said gears; and a decelerating cam on .the other side of and rotatable with said mutilated gear and positioned to coact with the other of said tcam contacting members for decelerating said second part and its gear gradually and smoothly to a standstill just subsequent to the unmeshing of said gears.
3. Intermittent rotary drive means comprising a first or driving rotating part and a second or driven rotating part rotated once for each rotation of said driving part; a mutilated gear on said first part meshing with a driven gear on said second part during a major portion of the rotation of said first part; a cam contacting member extending axially from each face of said driven gear; an accelerating cam on one side of and rotatable withsaidmutilated gear and in position to coact with one of said cam contacting members for accelerating said second part and its gear gradually and smoothly to a tooth speed common with that of said mutilated gears just piror to meshing of said gears; a decelerating cam on the other side of and rotatable with said mutilated gear and positioned to coact with the other of said cam contacting members for decelerating said second part and its gear. gradually and smoothly to a standstill just subsequent to the unmeshing of said gears; and guard portions formed on each of said cams for coacting each with its respective cam contacting member for insuring close coaction betweenthe other cam and its'cam contacting member during the period when the other cam is primarily active.
v4. In a rotary printer, a constantly rotating impression roller; an intermittently operating printing drurn having a periphery shaped to cooperate in a feeding manner with the impression roller only over a portion of the drum periphery, and having a stationary home position with a nonfeeding peripheral portion directed towards the impression roller; a continuously rotating power source; means to drive said impression roller from said power source at an appropriate determinate surface speed; means including a clutch for connecting the power source to the printing'drurn and for disconnecting it therefrom; trip mechanism actuated by an approaching workpiece for causing clutch engagement in response to arrival of a workpiece at printing position; means for gradually and smoothly accelerating the printing drum'to a surface speed substantially equal to that of the impression roller as the feeding portion of the periphery approaches feeding relation with the impression roller; means for rotating the printing drum at a substantially constant surface speed substantially equal to the surface speed'of said impression roller While the peripheries of the drum and roller are in feeding relation; means for gradually and smoothly decelerating the printing drum to zero after the surface of the printing drum departs frem feeding relationship with said impression roller; and means for effectingclutch disengagement as the printing drum comes to a standstill at home position.
References Cited in the file of this patent UNITED STATES PATENTS 10 Ogden Sept. 20, 1938 Harrold et a1 Max-.12, 1940 Kaddeland Mar. 12, 1940 Thatcher Mar. 11, 1941 Overbury July 6, 1943 Knauer Sept. 19, 1944 Dohl et a1 Aug. 22, 1950 Stanley Aug. 23, 1955 Wood May 22, 1956