US2244776A - Loom dobby - Google Patents

Description

June '10, 1941.

E. R. HOLMES Loom `BOBBY Filed Jan. 9, 1940 2 Sheets-Sheet 1 i Attorney,

Jun 10, 1941. E. R. HoLMEs LooM DBBY Filed Jan. 9, 1940 2 Sheets-Sheet 2 At tor may Patented June 10, 1941 LOOM BOBBY Elbridge Holmes, Worcester, Mass., assignor to Crompton & Knowles Loom Works, Worcester, Mass., a corporation of Massachusetts Application January 9, 1949, Serial No. 313,089

(ICI. (139-71) :1o claims.

This invention relates to improvements in shedding mechanism for looms and it is the general object of the invention to provide means for insuring uniformity in the shedding operation to cause the harnesses to reach their midpositions at the same point in successive beats of the loom. i

In the usual dobby harness operating mechanism two oppositely reciprocating knives are driven by a connector attached to a crank arm on one or the other of the main shafts of the loom. The `connector swings to a diagonal position during a revolution of the crank arm and for this reason its lower end must be moved through slightly more than one-quarter of a turn of the crank in order to move the upper end, which drives the knives, to its midposition. At a later time in the revolution of the crank the knives reach their midposition before the lower end of the connector has been moved onequarter turn from its top position. There results an unevenness in the timing of the shed with respect to the beat-up of the lay the effect of which is to produce rough cloth.

The usual dobby includes in its construction a three-arm rocking lever, two arms of which are connected to the knives and the third arm of which is attached to the connector rod. It is an important object of my present invention to provide a movable connection between the connector rod and this third arm of the lever, the connection to be moved toward and from the axis of the lever to vary the angular rate of motion of the lever. In this way arrival of the knives at their midposition is delayed when the crank connector is descending and is advanced when the connector is rising. The amount of delay and advancement compensates for the uneven timing of the connector due to the crank and as a result the knives reach their midpositions at the same point in two successive loom cycles.

It is a further object of my present invention to provide a sliding connection between` the driven arm of the lever and the crank connector rod, and control the sliding connection by a link moving about a center which is eccentric with respect to the axis of the lever. The pivot of the link is so placed as to provide the compensation in angular movement of the lever already described.

With these and other objects in view which will appear as the description proceeds, my

invention resides in the combination and arrangement of parts hereinafter described and set forth. j

In the accompanying drawings, wherein a convenient embodiment of my invention is set forth- Fig. 1 is an end elevation of a loom having a dobby provided with my present invention,

Fig. 2 is a rear elevation taken in the direction of arrow 2, Fig. 1,

Fig. 3 is a diagrammatic View showing certain parts of Fig. 2 on an enlarged scale and setting forth the effect which the eccentrically mounted link has in modifying the motion of the driving lever,

Fig. 4 is an end elevation taken in the direction of arrow 4, Fig. 3, and

Fig. 5 is a detail vertical section on line 5-5 of Fig. 3, parts being shown in rear elevation.

Referring to Figs. 1 and 2, I have shown a loom frame I 0 having a lay II mounted on swords I2 which swing about rocker shaft I3. The lay is driven by connectors I4 attached at their forward ends to the lay at I5 and driven -at their rear ends by cranks I6 on the top or crank shaft I'I. A gear I8 on the top shaft Il meshes with a second gear I 9 of twice the diameter mounted on the bottom shaft 20. Certain mechanisms not shown, such as the picking, are

loperated by the bottom shaft and due to the ratio of gears I8 and I9 the bottom shaft will make one-half a revolution for each complete forward beat of the lay.

Mounted on the upper part of the loom frame is a dobby D having a frame 25 in which is journaled a rocking shaft 26. This shaft has front and back levers 21 and 2B, respectively, the upper arms 29 and 30, respectively, of the levers being attached by connectors 3| to a top knife 32 slidable in a slot 33 horizontally disposed `in the top part of the dobby frame. The lower arms 34 and 35, of levers 2l and 28, respectively, are similarly attached by connectors 36 to a bottom knife 3l slidable in a slot 38 below rslot 33. The rear lever 28 has a substantially horizontal driven arm 4D which receives driving power from an upright connector 4I through connections to be described hereinafter and forming part of my present invention. The lower end of the connector is attached adjustably as at 42 to a crank arm 43 secured to the bottom shaft 20. By the connections described the levers 21 and 28, both of which are secured to the rocker shaft 2t, rock in a left hand direction as viewed in Fig. 2 while the cr-ank arm 43 is rotating in a clockwise direction as viewed in Fig. 1 from its low to its high position, and the levers have an opposite or right hand oscillation when the crank moves from its high to low position during continued rotation thereof.

The harness frames are designated at H and are attached by harness cords 45 trained over pulleys 43 to harness jacks 41 pivoted to the dobby frame at 43. Each dobby jack is provided with a dobby back lever i) pivoted thereto at 5l, and each lever 5l) is provided with top and bottom hooks 52 and 53, respectively, controlled by pattern mechanism not shown for cooperation With the knives 32 and 3l, respectively.

The matter thus far described is of usual construction and operates to cause reciprocation of the knives 32 and 37 in opposite directions when the levers 21 and 23 are oscillated. The sequence in which the harness frames are raised is determined by the order in which the dobby hooks are engaged by their respective knives, movement of any hook to the right as viewed in Fig. 2 corresponding to a lifting motion of the associated harness frames, and the latter being in down position when each of the hooks associated therewith is held out of the path of the knives. by pattern mechanism. It is apparent therefore that the character of motion of the harness frames` is dependent upon the motion of the levers which drive the knives.

As heretofore constructed the dobby knives reach their mid-position when the crank arm 43 is to the left of and slightly above the axis of shaft 20 during one beat of the loom, while the knives reach their mid-position on the next beat of the loom before the crank 43, in its continued rotation, reaches a position horizontally opposite shaft 20. The lay of the loom receives a regular motion from the crank shaft and reaches a given position in its forward beat when the crank 43 is in the same angular position with respect to shaft 2l) on successive beats of the lay, the two positions for the crank being exactly 180 apart. The lay is therefore in time with the crank 43 on all beats of the loom, but is not in the same time relation with the knives of the dobby on any two successive beats of the loom.

My present invention aims to correct the defective time relation just described by modifying the motion of the oscillating levers. I use the ordinary crank 43 having its inherent defects with respect to dobby time, but correct these defects by means of a driving attachment'between the connector rod 4l and arm 4i! of the rear lever 28. As shown in the drawings I provide thearm 40 with an elongated slot 6B extending radially from the rocking shaft 2B and mount in said slot a pair of blocks 6i and 52 carried by a pin 63 extending through a yoked rod head 64 pivotally connected as at E5 to the upper end of rod 4l. The blocks have flat surfaces G6 which slide along the. top and bottom edges 6l and 68, respectively, of the slot Eil.

The head 64 is provided with an extended bearing 10 which provides a pivotal connection between the head and the outer or right hand end of a link 1I, as viewed in Figs. 2 and 3. The inner or other end of link ll rocks about a stud l2 held adjustably in a slot 'i3 formed in a bracket 'f4 secured in adjusted vertical position on the dobby frame by bolts '15. 'l2 is eccentric with respect to the axis of the rocking shaft 26 sov that the driven arm 4i) rocks about one center while the driving connection Y between the connector rod'4l and arm 4i! rocks about a different center. In Fig. 3 the arc b The axis of thestud F CTI suggests the path traversed by a given part of lever 40 and the path which stud t3 would traverse if bolted securely to arm 4i), while the arc c represents a path actually traversed by the stud 63 due to the fact that it has a sliding connection with respect to arm 40 and rocks about stud 'l2 eccentrically with respect to shaft 26.

In order to understand the operation of my invention I have shown the customary crank drive for the dobby, which I retain, and also illustrate the reason Why a drive of this type gives an uneven time to the dobby. The circle d represents the path traversed by pivot 4Z, and the vertical line e cuts this circle at f above shaft 2i) and at g below the shaft, while the axis of shaft is represented at h. The proper condition for an evenly timed dobby would exist if the pivot 42 moved through a distance equal to g--h during one-quarter of a revolution of the bottom shaft, and through the distance 71,-1 during the next quarter of revolution of the shaft. Due to the fact that rod 4| is a connector` of finite length the pivot 65 `does not rise a distance equal to g-h when stud 42 has moved from g to a position horizontally opposite the axis h, represented at 7' in Fig. 4. The inclined position of rod tl enters into this discrepancy which is characteristic of crank motions. The axis G5 will as a matter of fact move through a distance equal to g-k while stud 42 is lifting through a distance g-h, the point 7c being the intersection of vertical line e and an arc struck from the center of stud when the parts are in the position shown in Fig.

f' 4. The stud 42 must be lifted above horizontal line m-m by the distance h-lc before stud 65 will reach its mid position. From this relation it is apparent that crank arm 43 must move through a distance in excess of 90 from the point g before the harnesses can reach their mid position, a condition which means that stud G5 rises at a slower rate than does stud 42. As crank 43 continues to turn it passes through less than 90 in order to place stud 42 at point f. From this relation it will be seen that stud $5 rises at a faster rate when approaching point f than does the stud 42, due to movement of the connector rod from an inclined to a vertical position.

Recognizing these differences between `|the rates of travel of studs 42 and 65 I have provided the previously described mechanism and have placed the center 'I2 in such a position as to increase the rate of rise o-f stud 65 in that part of its travel corresponding to the movement of stud 42 from position y to a position y' and to decrease the rate of rise of .stud 65 for the remainder of the up motion of stud 42 to position f. The reason for 'this change of rate will be apparent from the upper part of Fig. 3. Arc c has the stud 12 as a center, while arc b has the axis of the rocker shaft 26 as its center. Since the length of the link 'H remains constant it is apparent that when arm is inthe low dot and dash position of Fig. 3 stud 63 will be relatively near the rocker shaft 26 so that the effective working arm of the driven arm 4f) will be -short with a consequent increase in the rate of motion on the part of lever 28. As arm 411 approaches the upper or dotted line position of Fig. 3 stud 63 moves along arc c toward its farthest position from the axis of shaft 2f, thereby lengthening the effective length of arm 40 with a resultant retarded rate of motion. The rates at which stud would rise if fastened to arm 4l] are therefore modified, the stud 65 rising relatively fast when moving from its low to mid-position to reach the latter position when stud 42 is. on line m-n, and rising relatively slowly during the upper part of its motion. These opposed rates neutralize' each other-and result in giving a substantially uniform crank motion to the rise and fall of the stud 65. The latter therefore reaches its mid-position when stud 42 has reached its mid-position, both studs being assumed from this statement to be rising.

'I'he same condition exists but in the reverse order when stud 42 ismoving downward from its high -point f to point g.

From the lower part of Fig. 4 i't will be apparent that the distance h-k will increase with increased distance between stud 42 and shaft 2'9 and there will lbe a corresponding change in theamount of angular motion on the part offcrank 43 before the upper end of connector 4l will have completed one-half of its rising motion. Under this assumed change, however, the conditions already described can be duplicated by altering the position of stud 12 until the neutralization of opposing rates already mentioned gives the desired motion as a net result of their mutual cancellation.

From the foregoing it will be seen that I have' provided a' simple means for correcting the unequal rates of motion of the dobby rocking lever inherent in the usual form of crank drive, this correction being effected by a sliding connection between the driven arm 40 and the connector 4I. The slidingconnection moves toward shaft 26 at a time in the cycle of loom operations when crank 43 is raising stud 65 at a relatively low rate of speed, and moves the sliding :connection away from shaft 26 during the next period in the rotation of the bottom shaft when the crank arm 43 is acting to raise stud 65 at a relatively fast rate. It will also be seen that provision is made for changing the location of stud 'l2 so as 'to compensate for changes in the position of stud 42 relatively to the bottom shaft. While I have described the invention in connection with a crank arm 43 in the fbottomu shaft, I do not wish necessarily to be limited' to this particular form of drive, inasmuch as the eccentricallyv mounted link TI is not limited in its use to a drive derived from the bottom shaft.

Having thus described my invention it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and I do not wish to be limited to the details herein disclosed, but what1 I claim is:

1. In a loom having harness frames and an oscillating actuator to move the harness frames' by angular motion of the alctuator, the loom having a driver for the actuator having a working stroke the rate of motion of which is relatively slow at the start of the stroke and relatively fast near the end of the stroke, that improvement comprising a driving connection between the driver and actuator movable progressively with respect to the axis of the actuator throughout the working stroke of the actuator, and means to locate the driving connection at a point relatively near the axis of the actuator when said driver is moving relatively slow at the start of its working stroke and locate said driving connection at a point relatively remote from the axis of the actuator when the driver is moving relatively fast near the end of the working stroke.

2. In a loom having harness frames and an oscillating actuator to move the harness frames by angular motion of the actuator, the loom having a driver for the actuator having a working stroke the rate o-f motion of which is relatively slow at 'the start of the stroke and relatively fast near the end of the stroke, that improvement comprising a sliding connection between the driver and the actuator, and mean-s cooperating with the actuator throughout the working stroke of the latter to move the sliding connection from a point relatively close to the axis of the actuator when the driver is moving relatively slow at the start of a working stroke thereof to a point relatively remote from the axis of the actuator when the driver is moving relatively fast near the end of the working stroke.

3. In a loom having harness frames and an oscillating actuator to move 'the harness frames by angular motion of the actuator, the loom having a driver for the actuator having a working stroke the rate of motion of which is relatively slow a't. the start of the stroke and relatively fast near the end of the stroke, that improvement comprising a sliding connection lbetween the actuator and the driver, a link connected to the sliding connection, and a pivot for 'the link eccentric with respect to the axis of the actuator, the pivot of the link so located with respect to the axis of the actuator as to position the sliding connection relatively close to 'the axis of the actuator when the driver is moving relatively slow and position the sliding connection relatively remote from the axis of the actuator when the driver is moving relatively fast.

4. In a loom having a rotating shaft carrying a crank attached to a crank connector and having an oscillating lever connected to lifter knives for actuation of harness frames, the lifter knives reciprocating in opposite directions and cooperating with hooks attached to harness lifting jacks, that improvement comprising a link mounted for pivotal movement about a center eccentric with respect to the axis of the lever, and

a vsliding connection between the lever and the connector rod and attached to the link to be moved by the latter relatively to the lever as the lever moves angularly.

5. In a loom having a rotating shaft carrying a crank attached to a crank connected to one end of a connector rod and having an oscillating lever connected to lifter knives for actuation of harness frames, the lifter knives reciprocating in opposite directions and cooperating with hooks attached to harness lifting jacks, that improvement comprising a link movable about a pivot eccentric with respect to the axis of the lever and jointed to the other end of the connector rod, and a sliding connection between the connector rod and the lever, said sliding connection movable toward and from the axis of the lever during motion of the connector rod due to the eccentric relation of the axis of the lever and the pivot of the link.

6. In a loom having a rotating shaft carrying a crank attached to a crank connector rod and having an oscillating lever connected to lifter knives and rocking about an axis for actuation of harness frames, the lifter knives reciprocating in opposite directions and cooperating with hooks attached to harness lifting jacks, the connector rod when moving in a given direction on a working stroke thereof travelling at a relatively low rate of speed at the start of its working stroke and at a higher rate of speed near the end of its working stroke, that improvement comprising a movable driving connection between the connector rod and the lever, and means to cause a progressive increase in the distance between the driving connector and the axis of the lever to cause the rod to move the lever during the Working stroke oi the connector rod at a relatively high angular rate during the rst part of' said working stroke of the connector rod and move the lever at a relatively low angular rate during the latter part of the working stroke of said connec-tor rod.

7. In a loom having a rotating shaft carrying a crank attached to a crank connector rod and having an oscillating lever connected to lifter knives for actuation of harness frames, the` lifter knives reciprocating in opposite directions and cooperating with hooks attached to harness liftmg jacks, the rod when moving from one extreme of a working stroke thereof to the other extreme travelling at a relatively low rate of speed at the start of its motion when adjacent to said one extreme and at a higher rate of speed near the end of its motion adjacent to the said other extreme, that improvement comprising a sliding connection between the connector rod and the lever movable in a direction toward and from the axis of the lever, and means to position the sliding connection relatively near the axis of the lever u during said first part of the motion of the connector rod and position said sliding connection relatively far from the axis of the lever during the latter part of saidv motion of the connectory lifting jacks, the other end of the connector rodv travelling at a relatively low rate of speed at the start of a working stroke of the connector rod and at a higher rate of speed near the end of the working stroke, that improvement comprising al sliding connection between said other end of the connector rod and the lever movable in a directiontoward and from the axis of the lever, a link connected to the sliding connection, and a pivot for the link eccentric with respect to the axis of the lever, the two axes being so located as to position the sliding connection relatively close to the axis of the lever during the rst part of said working stroke of the connector rod and positioning said sliding connection relatively remote from the axis of said lever during the latter part of said working stroke of the connector rod.

9. In a loom having harness frames and an actuator oscillating about an axis to move the frames, the loom having a uniformly rotating crank arm attached to a connector rod, a driving connection between the connector rod and the actuator, movement of the crank arm through a half turn moving the driving connec-A tion at a rate which is relatively slow during the rst part of said half turn of the crank and relatively fast during the latter part of said half turn of the crank, and means to locate the driving connection at progressively increasing distances from said axis during said half' turn of the crank arm, said driving connection being relatively close to the axis of the actuator when the driving connection is moving relatively slow and relatively far from the axis of the actuator when said driving connection is moving relatively fast.

l0. In a loom having harness frames and an actuator oscillating about an axis to move the harness frames lby angular motion of the actuator, the loom having a driver for the actuator having a working stroke which starts at a given rate of motion and ends with a different rate of motion, that improvement comprising a driving connection between the driver and actuator movable progressively with respect to the axis of the actuator throughout the working stroke of the actuator, and means to locate the driving connection at a point relatively near the axis ofthe actuator when the driver is moving at the slower of said rates of motion at one end ofV a working stroke and locate said driving connection at a point relatively remote from the axis of the actuator when the driver is moving at the faster of said rates of motion.

ELBRIDGE R. HOLMES.

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