Knitting cam and cam apparatus

Abstract

 A knitting cam (12a) which engages with butts (6, 7) for controlling forward and backward movements of needles having different projecting amounts in order to form a small stitch and a large stitch in the same course is provided with a common lowering cam face (21) for lowering the butts of both a needle for the formation of a small stitch and a needle for the formation of a large stitch, a stitch size determining cam face (23) for a small stitch contiguous to the common lowering cam face (21), and a stitch size determining cam face (25) for a large stitch located rearwardly of the stitch size determining cam face (23) for a small stitch and having a lesser thickness than the common lowering cam face (21) for acting upon a butt which projects by a greater amount. The cam (12a) is further provided with lowering movement restricting means (24a, 24b) for restricting the maximum lowered position at least of the needle for the formation of a small stitch. By this means the jumping of needles at high speeds of movement of the needles and carriage is prevented.

Description

[0001] This invention relates to a knitting cam and a cam apparatus for forming stitches of different sizes in the same course of knitting.

[0002] In one known flat knitting machine, stitches can be transferred between at least a pair of needle beds provided at the front and at the rear and can also be transferred transversely by shifting the positions of the front and rear needle beds leftwardly and rightwardly. An arbitrary knitted texture can be knitted by making use of those functions. Furthermore, fully-fashioned knitting to knit a fabric of an arbitrary shape can be performed by transferring formed stitches between front and rear needles to suitably change the knitting width in accordance with the shape of a fabric to be knitted. With fully-fashioned knitting, a knitted fabric need not be cut after being knitted. Consequently the cutting step can be omitted and the knitting yarn used in that portion which is conventionally discarded at the cutting step after the completion of the knitting of the knitted fabric can be saved. Consequently, the production costs can be reduced.

[0003] However, when stitches are transferred to the needles of an opposing needle bed or when the front and rear needle beds are shifted leftwardly and rightwardly relative to each other while stitches are held on needles of the opposing needle beds, a burden is imposed on the stitches, and this sometimes means that the stitches are elongated or that the yarn is broken.

[0004] As a countermeasure against the problem described above, a method is employed wherein stitches on which such a burden may possibly be imposed are formed of a larger size than ordinary stitches in advance, so that they do not become elongated or broken upon stitch transfer.

[0005] One conventional method of forming stitches of different sizes, large and small, is shown in FIGS. 10A and 10B. FIG. 10A shows a conventional knitting cam and FIG. 10B is a sectional view taken along line G-G of FIG. 10A. A common lowering cam face 102 having a great thickness for engaging both a needle for the formation of a small stitch and a needle for the formation of a large stitch, and a stitch size determining cam face 103 for a large stitch contiguous with the common lowering cam face 102 and having a small thickness are provided on a knitting cam 101. The stitch size determining cam face 103 for a large stitch is formed with such a thickness that it is engaged only by a butt which is projected to its upper limit by a respective presser. Each of the butts of a needle for the formation of a small stitch and of a needle for the formation of a large stitch is first raised, upon movement of a carriage, to its most raised position by a needle raising cam passing the same locus, and then, during a lowering movement thereof, a knitting yarn is supplied to the hook of the needle. Then, each of the butts of the two needles is engaged by and lowered by a knitting cam. In this instance, the butt of the needle for the formation of a small stitch is put, by a known presser mechanism, into a condition sunk in a respective needle groove to a height at which the butt is not engaged with the stitch size determining cam face 103 for a large stitch having a small thickness, so that, of the needle for the formation of a small stitch and the needle for the formation of a large stitch having been lowered by the knitting cam 101 till then, only the needle for the formation of a large stitch is continued to be lowered by the stitch size determining cam face 103 for a large stitch, while the needle for the formation of a small stitch is not engaged by the stitch size determining cam face 103 for a large stitch and thus moves in a horizontal direction relative to and along a lower edge of the common lowering cam face 102.

[0006] Since the needle for the formation of a large stitch is lowered further than the needle for the formation of a small stitch by an amount corresponding to the stitch size determining cam face 103 for a large stitch formed at the lower end portion of the knitting cam 101 and having a small thickness, stitches of different sizes, large and small, are formed.

[0007] According to the prior art described above, after a needle for the formation of a small stitch and a needle for the formation of a large stitch are lowered by the common lowering cam face 102 of the knitting cam 101, the movement of the needle for the formation of a small stitch which has been lowered downwardly till then changes, at the location of a terminal end 104 of the common lowering cam face 102, from the previous downward movement to a horizontal movement relative to the knitting cam 101, while only the needle for the formation of a large stitch is lowered further downwards.

[0008] However, in a flat knitting machine, when a carriage is moved at high speed, the needles are lowered at high speed, whereupon inertia acts upon the needles and sometimes gives rise to a phenomenon called "jumping" in which the needles are moved excessively. In order to prevent the jumping phenomenon, a receiving cam for restricting excessive movement of a needle is conventionally provided at a position corresponding to the terminal end of a lowering face for moving the butt of a needle. However, in the prior art described above, since the stitch size determining cam face 103 for a large stitch is formed on the same line as the common lowering cam face 102 for lowering both of a needle for the formation of a small stitch and a needle for the formation of a large stitch, a receiving cam for restricting downward movement of a needle for the formation of a small stitch cannot be provided, and a receiving cam 105 is provided only for the needle for the formation of a large stitch which is lowered by the stitch size determining cam face 103.

[0009] Accordingly, if the carriage is moved at high speed, then although the knitting cam is constructed so that the movement of the butt of a needle for the formation of a small stitch changes from a downward movement to a movement in a horizontal direction relative to the knitting cam at the location of the terminal end 104 of the common lowering cam face, since no receiving cam is provided, the butt of the needle may possibly be moved further downwards than the terminal end 104 of the common lowering cam face by inertia acting upon the needle. If the needle for the formation of a small stitch is moved downwards further than the terminal end 104 of the common lowering cam face in this manner, a small stitch is formed with a similar size to that of a large stitch, resulting in the problem that such small and large stitches cannot be distinguished from each other.

[0010] It is an object of the present invention to provide a knitting cam and a cam apparatus by which at least a needle for the formation of a small stitch is not lowered excessively by inertia acting upon the needle as described above, and accordingly a small stitch is prevented from being formed with a size similar to that of a large stitch.

[0011] According to the present invention there is provided a knitting cam for engaging with butts for controlling forward and backward movements of needles projecting by different amounts in order to form a small stitch and a large stitch in the same course, characterised in that the knitting cam is provided with a common lowering cam face for lowering the butts of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, a stitch size determining cam face for a small stitch contiguous to said common lowering cam face, and a stitch size determining cam face for a large stitch located rearwardly of said stitch size determining cam face for a small stitch and having a smaller thickness than said common lowering cam face for acting upon a butt which projects to a greater extent, and in that the cam is further provided with lowering movement restricting means for restricting the maximum lowered position at least of the needle for the formation of the small stitch.

[0012] According to a preferred embodiment of the present invention, the knitting cam is further characterised in that it is provided with lowering movement restricting means for restricting the maximum lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch.

[0013] The lowering movement restricting means may comprise a receiving cam face provided at an upper end portion of said knitting cam.

[0014] Alternatively, the lowering movement restricting means may comprise a pair of receiving cams provided at opposing positions at a lower end portion of said knitting cam with a passageway for a butt interposed therebetween.

[0015] Also according to the present invention there is provided a cam apparatus for forming a small stitch and a large stitch in the same course of knitting, characterised in that the apparatus comprises a knitting cam for engaging with butts for controlling forward and backward movements of needles projecting by different amounts, said knitting cam being provided with a common lowering cam face for lowering the butts of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, a stitch size determining cam face for a small stitch contiguous to said common lowering cam face, and a stitch size determining cam face for a large stitch located rearwardly of said stitch size determining cam face for a small stitch and having a smaller thickness than said common lowering cam face for acting upon a butt which projects to a greater extent, said knitting cam being further provided with lowering movement restricting means for restricting the maximum lowered position at least of the needle for the formation of a small stitch, and pressing means for pressing down the butts of the needle for the formation of a small stitch to a level at which the butt is not engaged by said stitch size determining cam face for a large stitch.

[0016] Preferably, the knitting cam is provided with lowering movement restricting means for restricting the maximum lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch.

[0017] By a movement of the carriage, both the needle for the formation of a small stitch and the needle for the formation of a large stitch are lowered on the same locus by the common lowering cam face of the knitting cam positioned on the trailing side in the direction of advance of the carriage. At the terminal end of the common lowering cam face, both the needle for the formation of a small stitch and the needle for the formation of a large stitch are prevented from being further lowered by the lowering movement restricting means and thus move in a horizontal direction relative to the knitting cam along the stitch size determining cam face for a small stitch. As the carriage is moved further, both the needle for the formation of a large stitch and the needle for the formation of a small stitch arrive at the stitch size determining cam face for a large stitch having a small thickness, and there, since the butt of the needle for the formation of a small stitch is sunk slightly into its needle groove, it moves in the horizontal direction relative to the knitting cam without engaging with the stitch size determining cam face for a large stitch. On the other hand, the needle for the formation of a large stitch is lowered further downwards by the stitch size determining cam face for a large stitch.

[0018] A number of embodiments of a knitting cam and of a cam apparatus of the present invention will now be described with reference to the drawings.

[0019] In the drawings:

[0020] FIG. 1 is a plan view showing a first embodiment of cam unit in accordance with the present invention.

[0021] FIG. 2 is a side elevational view showing the construction of a needle employed in the first embodiment of the present invention.

[0022] FIG. 3A is a plan view showing a knitting cam of the first embodiment; FIG. 3B is a view showing the knitting cam of FIG. 3A as viewed from below; and

[0023] FIG.3C is a partial enlarged view of FIG. 3A.

[0024] FIG. 4 is a plan view illustrating one condition of the knitting cam and butts in the first embodiment of the present invention.

[0025] FIG. 5A is a sectional view taken along line C-C of FIG. 4 illustrating a condition of butts of a needle for the formation of a small stitch and the knitting cam; and FIG. 5B is a sectional view taken along line C-C illustrating a condition of a needle for the formation of a large stitch and the knitting cam.

[0026] FIG. 6A is a sectional view taken along line D-D of FIG. 4 illustrating a condition of the butts of the needle for the formation of a small stitch and the knitting cam; and FIG. 6B is a sectional view taken along line D-D illustrating a condition of the needle for the formation of a large stitch and the knitting cam.

[0027] FIG. 7 is a plan view illustrating a condition of the knitting cam and butts in accordance with the present invention.

[0028] FIG. 8A is a sectional view taken along line E-E in FIG.7 and illustrating a condition of butts of a needle for the formation of a small stitch and the knitting cam; and FIG. 8B is a sectional view taken along line E-E and illustrating a condition of butts of a needle for the formation of a large stitch.

[0029] FIG. 9A is a sectional view taken along line F-F in FIG. 7 and illustrating a condition of the butts of the needle for the formation of a small stitch and the knitting cam; and FIG. 9B is a sectional view taken along line F-F and illustrating a condition of the butts of the needle for the formation of a large stitch.

[0030] FIG. 10A is a plan view showing a knitting cam according to the prior art; and FIG. 10B is a sectional view taken along line G-G of FIG. 10A.

[0031] FIG. 1 shows a cam lock 1 of a carriage in accordance with the present invention as viewed from below, and FIG. 2 is a side elevational view showing an arrangement of a needle 2, a jack 3, a select jack 4 and a selector 5 controlled by the cam lock 1.

[0032] The needle 2 employed in the cam apparatus of the present invention is connected at a tail portion thereof to the jack 3 which has an upper butt 6 and a lower butt 7 disposed at upper and lower locations thereof spaced by a predetermined distance from each other. When the jack 3 is moved by way of the upper butt 6 or the lower butt 7, the needle 2 is also moved integrally with the jack 3. The jack 3 is formed from a resilient member and is curved at a rear portion thereof so as normally to bias the jack 3 and the select jack 4, which is disposed in an overlapping condition with a tail portion of the jack 3, so that the upper butt 6 and the lower butt 7 as well as a butt 8 of the select jack 4 may project outwardly of an associated needle groove. An upper limit position thereof is limited by a wire (not shown) mounted in a longitudinal direction of a needle bed. When the butt 8 provided at a head portion of the select jack 4 is pressed in a direction in which it is sunk into the needle groove, the butts 6 and 7 of the jack 3 disposed in an overlapping condition below the select jack 4 are sunk a little into the needle groove. In this instance, the butts 6 and 7 are not sunk fully in the needle groove, but are sunk to a height at which they are not engaged by a stitch size determining cam face for a large stitch which will be described hereinafter. The selector 5 is disposed rearwardly of the select jack 4, and can select the butt 8 of the select jack 4 to any of a plurality of positions in a needle sliding direction by known needle selecting means and select jack controlling means (not shown).

[0033] The cam lock 1 of the present invention has a left and right symmetrical configuration and includes a pair of left and right needle raising cams lla and llb provided on the opposite sides of a transfer receiving cam 10 provided at the centre of the cam lock 1 for guiding a needle which is to receive a stitch upon stitch transfer. Further, a pair of knitting cams 12a and 12b are provided in an opposing relationship to the needle raising cams 11a and 11b respectively, with a path for a butt defined therebetween. An upper cam 13 for guiding a needle to a knit position is provided at an upper portion of the transfer receiving cam 10. The knitting cams 12a and 12b are both provided on a base plate 14 for sliding movement parallel to inclined faces of the needle raising cams lla and llb respectively, by mechanisms which are not shown. A guide cam 15 is provided above the upper cam 13 with the path for a butt defined therebetween, and a retractable transfer raising cam 16 for guiding a needle which is to transfer a stitch upon stitch transfer is provided above the guide cam 15. A guide cam 17 is provided above the transfer raising cam 16 with a path for a butt defined therebetween. Reference characters 18a, 18b and 19a, 19b in FIG. 1 each denote a guide cam used to guide a butt. A pair of known presser mechanisms 20a and 20b are each constructed for rocking motion between two positions, namely a position in which it is engaged with and presses the butt 8 of a select jack 4 selected to a position indicated by line A-A in FIG. 1 and another position in which it is not engaged with the butt 8. This is effected by known selecting means (not shown) provided below the needle raising cams 11a and 11b.

[0034] The knitting cams 12a and 12b will now be described. Since the knitting cams are formed in a left and right symmetrical relationship, only the knitting cam 12a will be described. Fig. 3A shows the knitting cam 12a while FIG. 3B shows the knitting cam 12a of FIG. 3A as viewed from below. The knitting cam 12a is mounted for sliding movement relative to the base plate 14 in a condition in which the lower side thereof in FIG. 3B makes contact with the base plate 14 of the carriage 1. FIG. 3C is an enlarged view of a portion defined by a circle of FIG. 3A. The knitting cam 12a includes a common lowering cam face 21 opposed to and extending parallel to the needle raising cam 11a and having a great thickness, a stitch size determining cam face 23 for a small stitch provided contiguously to a terminal end 22 of the common lowering cam face 21 for causing the movement of the lower butt 7 to change from a movement in the downward direction to a movement in a horizontal direction relative to the knitting cam 12a, and a receiving cam face 24 provided at an upper portion of the knitting cam 12a provided at an upper portion of the knitting cam 12a for engaging with a lower edge of the upper butt 6 to restrict a downward movement of the needle.

[0035] The stitch size determining cam face 23 for a small stitch also has a stitch size determining cam face 25 for a large stitch having a greater thickness than the common lowering cam face 21 and formed at a position thereof displaced rearwardly in phase in the advancing direction of the carriage 1 from the common lowering cam face 21, at which the movement of the butt 7 changes from a downward movement to a movement in a horizontal direction.

[0036] The stitch size determining cam face 25 for a large stitch is provided at a height at which it is not engaged with the lower butt 7 of a jack 3 mounted in the same needle groove as a select jack 4 whose butt 8 is sunk in the needle groove by the presser mechanism described above.

[0037] The distance W from the terminal end 22 of the common lowering cam face 21 to a lowermost end of the stitch size determining cam face 25 for a large stitch is appropriately set equal to the distance of one or two needles and preferably is set equal to the distance of 1.5 needles.

[0038] The receiving cam face 24 for engaging with the lower end of the upper butt 6 of a jack 3 is formed with a shape corresponding to a lower edge of the knitting cam 12a, and includes a receiving cam face 24a for a small stitch which is engaged with the upper butts 6 of jacks 3 for both a needle for the formation of a small stitch and a needle for the formation of a large stitch, and a receiving cam face 24b for a large stitch which is engaged only with the butt of a jack 3 for a needle for the formation of a large stitch. The distance between the receiving cam face 24 and the stitch size determining cam face 25 for a large stitch is equal to the distance between the upper butt 6 and the lower butt 7.

[0039] The mode of operation will now be described. Here, for convenience of description, the butt of a jack 3 connected to a needle 2 for the formation of a small stitch is represented as the butt of a needle for the formation of a small stitch, and likewise, for a needle for the formation of a large stitch, the butt is represented as the butt of a needle for the formation of a large stitch. Similar representations are used also for select jacks.

[0040] Now, it is assumed that the carriage 1 is advancing in the direction of the arrow L in FIG. 1 to perform knitting. By the known selecting means (not shown) the butt 8 of a needle for the formation of a small stitch is selected to a position A-A in FIG. 1 while the butt 8 of another needle for the formation of a large stitch is selected to another position B-B. In this instance, the lower butt 7 of the needle for the formation of a small stitch and the lower butt 7 of the needle for the formation of a large stitch are both in a condition where they are projected upwardly to their upper limits from the respective needle grooves and thus both move along a locus indicated by the arrow X in FIG. 1. Each of the needles 2 is raised as the lower butt 7 thereof is engaged by an inclined face of the needle raising cam llb, and after it is raised to the top of the upper cam 13 it starts a lowering movement there due to the guide cam 15. Then, after a knitting yarn is supplied into the hook of the needle 2 from a yarn feeder (not shown), the lower butt 7 of the jack 3 is engaged by the common lowering cam face 21 of the knitting cam 12a positioned on the trailing side in the direction of advance of the carriage 1. In this instance, since the butt 8 of the select jack 4 for the needle for the formation of a small loop is selected to the position A-A, substantially one half of the butt 8 is sunk in the needle groove by the presser 20a and also the lower butt 7 of the jack 3 whose tail portion is disposed below the select jack 4 is sunk a little into the needle groove.

[0041] At a position at which the lower butt 7 is engaged by the common lowering cam face 21 of the knitting cam 12a, the lower butt 7 of the needle for the formation of a small stitch is in a condition where it is sunk a little into the needle groove by the presser 20a, whereas the lower butt 7 of the needle for the formation of a large stitch is in a condition projected to its upper limit outwardly from the needle groove. However, since the common lowering cam face 21 is formed with a thickness sufficient to engage both the needle for the formation of a small stitch and the needle for the formation of a large stitch sunk in the needle grooves, both needles are lowered by the common lowering cam face 21.

[0042] As the carriage moves further in the direction of the arrow L until both the needle for the formation of a small stitch and the needle for the formation of a large stitch come to the terminal end 22 of the common lowering cam face 21 of the knitting cam 12a, the upper butt 6 and the lower butt 7 of both the needle for the formation of a small stitch and the needle for the formation of a large stitch come to a position indicated by line C-C in FIG. 4. At this position, while the lower butt 7 of the jack 3 for the needle for the formation of a small stitch is in a condition sunk a little in the needle groove by the presser 20a as shown in FIG. 5A, since the common lowering cam face 21 is formed with a thickness sufficient to allow the common lowering cam face 21 to engage with all butts projecting outwardly from the needle grooves, the lower butt 7 is in a condition engaged by the common lowering cam face 21, and since the lower edge of the upper butt 6 is engaged by the receiving cam face 24a for a small stitch, the jack 3 is prevented from being moved downwards any more. In the meantime, the lower butt 7 of the select jack 4 for the needle for the formation of a large stitch is not pressed by the presser 20a and thus keeps its condition projected to its upper limit outwardly of the needle groove, and the lower butt 7 is in a condition engaged by the common lowering cam face 21. Thus, the upper butt 6 is engaged by the receiving cam face 24a for a small stitch so that it is prevented from being moved downwardly any more, just as described above. Consequently, the movements of both the needle for the formation of a small stitch and the needle for the formation of a large stitch change from their previous downward movements to movements in a horizontal direction relative to the carriage 1.

[0043] As the carriage moves further in the direction of the arrow L, both the needle for the formation of a small stitch and the needle for the formation of a large stitch come to the position indicated by line D-D in FIG. 4 after they have moved horizontally relative to the carriage 1. In this position, the lower butt 7 of the jack 3 for the needle for the formation of a small stitch is in a condition a little sunk by the presser mechanism as shown in FIG. 6A. Accordingly, the lower butt 7 of the jack 3 for the needle for the formation of a small stitch is not engaged by the stitch size determining cam face 25 for a large stitch which is formed with a thickness smaller than that of the common lowering cam face 21, and thus continues to move in the horizontal direction relative to the carriage 1 as indicated by the arrow Y in FIG. 3. In this position, while the receiving cam face 24b for a large stitch is formed at an upper portion of the knitting cam 12a corresponding to the stitch size determining cam face 25 for a large stitch, since the receiving cam face 24b for a large stitch is provided at a position lower than the receiving cam face 24a for a small stitch, the upper butt 6 of the needle for the formation of a small stitch is not engaged by the receiving cam face 24b for a large stitch.

[0044] The butt 8 of the select jack 4 for the needle for the formation of a large stitch is at the position B-B in FIG. 1. The butt 8 of the select jack 4 is not pressed by the presser 20a and also the butt 7 of the jack 3 keeps its condition projected to its upper limit outwardly of the needle groove. Accordingly, as shown in FIG. 6B, the butt 7 of the jack 3 for the needle for the formation of a large stitch is engaged by the stitch size determining cam face 25 for a large stitch and is lowered by the stitch size determining cam face 25 for a large stitch as indicated by the arrow Z in FIG. 3, whereafter the needle for the formation of a large stitch is prevented from moving downwardly any more since the lower edge of the upper butt 6 is engaged by the receiving cam face 24b for a large stitch formed at the upper portion of the knitting cam.

[0045] In this manner, the needle for the formation of a large stitch is lowered by a greater amount than the needle for the formation of a small stitch by a distance corresponding to the height of the stitch size determining cam face 25 for a large stitch, so that stitches of different sizes, large and small, are formed. Since only the needle for the formation of a large stitch is lowered further after each needle is prevented from further downward movement by the receiving cam face 24a for a small stitch at the terminal end 22 of the common lowering cam face 21 which provides a maximum lowered position for a needle for the formation of a small stitch, the receiving cam can act upon both the needle for the formation of a small stitch and the needle for the formation of a large stitch, and the needle lowering amount can be fixed for both needles.

[0046] A second embodiment of the present invention will now be described. The second embodiment is different from the first embodiment in the construction of the receiving cam. In the first embodiment, the receiving cam face 24 is formed at the upper portion of the knitting cam 12a so that the lower edge of the upper butt 6 of a needle provided with a pair of upper and lower butts is engaged by the receiving cam face 24 to prevent an excessive lowering movement of the needle. In contrast, in the second embodiment, a receiving cam 31 is provided integrally with a knitting cam 30 at a lower end portion of the knitting cam 30 as shown in FIG. 7. The knitting cam 30 has provided thereon a common lowering cam face 32 which is engaged by both a needle for the formation of a small stitch and another needle for the formation of a large stitch in order to lower the needle for the formation of a small stitch to a most lowered position of the needle. The cam 30 also has a stitch size determining cam face 33 for a small stitch which is provided contiguously to the common lowering cam face. Further, at a location rearwardly of the stitch size determining cam face 33 for a small stitch in the direction of advance of a carriage, a stitch size determining cam face 34 for a large stitch is formed with a thickness smaller than that of the common lower face and is engaged by a butt having a greater projecting amount in order to lower it to a most lowered position of a needle for the formation of a large stitch.

[0047] The function of the knitting cam 30 in the second embodiment will be described with reference to FIG. 8A which illustrates a condition of the jack 3 for a needle for the formation of a small stitch and the knitting cam 30 at the position of line E-E in FIG. 7, and FIG. 8B which illustrates a condition of a jack 3 for a needle for the formation of a large stitch and the knitting cam 30. At the location of line E-E in FIG. 7, a lower edge of each of the lower butt 7 of the jack 3 for the needle for the formation of a small stitch and the lower butt 7 of the jack 3 for the needle for the formation of a large stitch is engaged with a receiving cam face 31a for a small stitch, so that both are prevented from being lowered any more and the needles thereafter move in a horizontal direction relative to the carriage. Then, at the position of line F-F in FIG. 7, the needle for the formation of a small stitch continues its movement in the horizontal direction relative to the carriage without being engaged by the stitch size determining cam face 34 for a large stitch as shown in FIG. 9A. However, the lower butt 7 of the jack 3 for the needle for the formation of a large stitch is engaged by and is further lowered by the stitch size determining cam face 34 for a large stitch, and thereafter, the lower edge of the lower butt 7 is engaged by a receiving cam face 31b for a large stitch. Consequently, the needle for the formation of a large stitch is then not lowered any more.

[0048] It is to be noted that while, in the embodiments described above, the receiving cam which is a lowering movement restricting means for limiting the maximum lowered position of a needle is provided for both the needle for the formation of a small stitch and the needle for the formation of a large stitch, the lowering movement restricting means may in general terms be provided so as to restrict at least the maximum lowered position of the needle for the formation of a small stitch.

[0049] It is to be noted that, where the receiving cam 31 is provided downwardly of the knitting cam 30 as shown in the second embodiment, the present invention can be utilised only with the lower butt 7.

[0050] Furthermore, while the receiving cam 31 in the second embodiment is provided integrally with the knitting cam, it can alternatively be provided as a separate body.

[0051] As described above, the knitting cam of the present invention is constructed such that, when a small stitch and a large stitch are to be formed in the same course, a needle for the formation of a small stitch and a needle for the formation of a large stitch are lowered by a common lowering cam face and then are restricted from further lowering movement by the receiving cam, and only the needle for the formation of a large stitch is thereafter lowered further. Even when the carriage is moved at a high speed to perform knitting, the lowering movement restricting means for restricting the most lowered position can act upon the needle for the formation of a small stitch, and consequently the needle for the formation of a small stitch does not suffer from a jumping phenomenon. Accordingly, a small stitch is not formed with a size similar to that of a large stitch, and a knitted fabric in which small stitches and large stitches can definitely be distinguished can be knitted.

[0052] Where the knitting cam is provided with lowering movement restricting means for restricting the most lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, since the lowering movement restricting means for restricting the most lowered positions of the needles can act upon both of the needles, neither the needles for the formation of a small stitch nor the needles for the formation of a large stitch suffer from a jumping phenomenon. Accordingly, a splendid knitted fabric wherein small stitches and large stitches have respective uniform regular sizes can be knitted.

[0053] Where the lowering movement restricting means if formed as a receiving cam face provided at an upper end portion of the knitting cam, there is no necessity to provide a receiving cam separately, and consequently the construction can be simplified.

[0054] Where the restricting means is formed as a pair of receiving cams disposed at opposing positions at a lower end portion of the knitting cam with a passageway for a butt interposed therebetween, a needle can be controlled with a single butt and the cam for controlling a butt can be formed with a reduced size in the direction of its height. Consequently, the cam apparatus can be reduced in size.

[0055] According to the cam apparatus of the present invention, since the butt of an arbitrary needle is sunk in an associated needle groove to a depth at which it is not engaged by the stitch size determining cam face for a large stitch by the pressing means, the arbitrary needle can be used to knit a small stitch or a large stitch, and a knitted fabric in which small stitches and large stitches can be distinguished can be knitted.

[0056] Where the knitting cam of the cam apparatus of the present invention is provided with lowering movement restricting means for restricting the most lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, an arbitrary needle can be used to knit a small stitch or a large stitch, and a splendid knitted fabric wherein small stitches and large stitches have respective uniform regular sizes can be knitted.

Claims

1. A knitting cam for engaging with butts for controlling forward and backward movements of needles projecting by different amounts in order to form a small stitch and a large stitch in the same course, characterised in that the knitting cam is provided with a common lowering cam face for lowering the butts of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, a stitch size determining cam face for a small stitch contiguous to said common lowering cam face, and a stitch size determining cam face for a large stitch located rearwardly of said stitch size determining cam face for a small stitch and having a smaller thickness than said common lowering cam face for acting upon a butt which projects to a greater extent, and in that the cam is further provided with lowering movement restricting means for restricting the maximum lowered position at least of the needle for the formation of the small stitch.

2. A knitting cam as claimed in claim 1, characterised in that it is provided with lowering movement restricting means for restricting the maximum lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch.

3. A knitting cam as claimed in claim 1 or 2, characterised in that said lowering movement restricting means comprises a receiving cam face provided at an upper end portion of said knitting cam.

4. A knitting cam as claimed in claim 1 or 2, characterised in that said lowering movement restricting means comprises a pair of receiving cams provided at opposing positions at a lower end portion of said knitting cam with a passageway for a butt interposed therebetween.

5. A cam apparatus for forming a small stitch and a large stitch in the same course of knitting, characterised in that the apparatus comprises a knitting cam for engaging with butts for controlling forward and backward movements of needles projecting by different amounts, said knitting cam being provided with a common lowering cam face for lowering the butts of both the needle for the formation of a small stitch and the needle for the formation of a large stitch, a stitch size determining cam face for a small stitch contiguous to said common lowering cam face, and a stitch size determining cam face for a large stitch located rearwardly of said stitch size determining cam face for a small stitch and having a smaller thickness than said common lowering cam face for acting upon a butt which projects to a greater extent, said knitting cam being further provided with lowering movement restricting means for restricting the maximum lowered position at least of the needle for the formation of a small stitch, and pressing means for pressing down the butts of the the needle for the formation of a small stitch to a level at which the butt is not engaged by said stitch size determining cam face for a large stitch.

6. A cam apparatus as claimed in claim 5, characterised in that said knitting cam is provided with lowering movement restricting means for restricting the maximum lowered positions of both the needle for the formation of a small stitch and the needle for the formation of a large stitch.

Drawing