Double-cylinder circular knitting machine for manufacturing socks, stockings and the like with device for tensioning the knitted fabric

Abstract

 The double-cylinder circular knitting machine (1) has a device for tensioning the knitted fabric (11,12). The device has an element (11) for retaining the fabric proximate to the knitting forming region (10) and a tensioning cylinder (12), which is hollow and open at its axial ends. The tensioning cylinder (12) is accommodated in the upper needle cylinder (3), and is controllably movable along the axis (4) of the needle cylinders (2,3). The tensioning cylinder (12) has a lower end which is engageable, upon sliding along the needle cylinder axis (4), with the knitted fabric being formed. The retention element (11) has a size that allows the movement of the tensioning cylinder (12) about the retention element (11). The tensioning device comprises an actuation mechanism (30-33) for moving the tensioning cylinder (12) along the needle cylinder axis (4) and an adjustment mechanism (40-48) for adjusting the intensity of the force applied by the actuation mechanism (30-33) to the tensioning cylinder (12) in a direction that is substantially parallel to the needle cylinder axis (4), at least during the tensioning of the knitted fabric being formed.

Description

[0001] The present invention relates to a double-cylinder circular knitting machine for manufacturing socks, stockings and the like with a device for tensioning the knitted fabric.

[0002] Double-cylinder circular machines are known which have a device for tensioning the knitted fabric that comprises an element for retaining the initial portion of the fabric, which is arranged inside the lower needle cylinder proximate to the region where the knitting is formed, and a fluid-actuated piston provided with a hollow stem that is open at its ends and is slideable inside a cylindrical chamber formed coaxially in the upper needle cylinder.

[0003] The retention element faces the lower end of the stem of the piston, and its dimensions are such as to allow the descent of the stem into the lower needle cylinder by passing around said retention element, so as to apply tension to the fabric that stretches from the retention element to the knitting-forming region of the machine.

[0004] The upper end of the stem can be connected to a suction device that sucks the fabric at the end of its processing and also causes it to turn inside out.

[0005] The descent of the piston to achieve tensioning of the fabric being formed is achieved by gravity, by providing appropriate piston weighting elements, whereas the piston is usually raised by pressurized fluid fed into the cylindrical chamber.

[0006] These known types of double-cylinder machines with fabric tensioning device have some drawbacks.

[0007] In particular, in double-cylinder machines with a fabric tensioning device, if one wishes to change the tensioning force, it is necessary to proceed by increasing or decreasing the number of piston weighting elements.

[0008] This operation is scarcely practical, since it requires partial disassembly of the machine and only allows an approximate adjustment of the force to which the sock or stocking is subjected during tensioning.

[0009] Moreover, in some kinds of knitting it is desirable to be able to vary the tension during formation of the knitted fabric. This operation is practically impossible with currently commercially available fabric tensioning devices, since it is impossible to vary the number of weighting elements during operation of the machine.

[0010] The aim of the present invention is to solve the problems described above by providing a double-cylinder circular knitting machine for manufacturing socks, stockings and the like with a knitted fabric tensioning device that allows to very simply and easily vary, according to requirements, the tensioning force to which the knitted fabric is subjected.

[0011] Within the scope of this aim, an object of the invention is to provide a machine with a tensioning device that allows to vary the tensioning force to which the fabric is subjected even during the formation of the knitted fabric.

[0012] Another object of the invention is to provide a machine with a tensioning device that allows to control, at all times, the tensioning force applied to the knitted fabric being formed.

[0013] Another object of the invention is to provide a machine with a fabric tensioning device, wherein the tensioning force to which the fabric is subjected, can vary according to a preset program as a function of the type of knitting, the type of yarn, and other parameters of the knitting being formed.

[0014] This aim, these objects, and others which will become apparent hereinafter are achieved by a double-cylinder circular knitting machine for manufacturing socks, stockings and the like with a device for tensioning the knitted fabric, which comprises a lower needle cylinder and an upper needle cylinder which are mutually coaxial and can be rotationally actuated about their substantially vertical common axis, said needle cylinders internally accommodating a tensioning device for the knitted fabric being formed, which comprises: retention means for retaining the fabric proximate to a knitting forming region, and a tensioning cylinder, which is hollow and open at its axial ends, said tensioning cylinder being accommodated in said upper needle cylinder, and controllably movable along said axis, a lower end of said tensioning cylinder being engageable, by sliding along said axis, with the knitted fabric being formed, said retention means having a size that allows the movement of said tensioning cylinder about said retention means; characterized in that it comprises actuation means that act on said tensioning cylinder to move it along said axis and adjustment means for adjusting the intensity of the force applied by said actuation means to said tensioning cylinder in a direction that is substantially parallel to said axis, at least during tensioning of the knitted fabric being formed.

[0015] Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the machine according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

figure 1 is a schematic axial sectional view of the machine with the tensioning device according to the invention, with the tensioning cylinder in the inactive position;

figure 2 is a schematic sectional view, similar to figure 1, of the machine according to the invention, with the tensioning cylinder in the position for engaging the knitted fabric being formed;

figure 3 is a sectional view, similar to the preceding ones, of the machine according to the invention, with the tensioning cylinder shown during the tensioning of the knitting being formed;

figure 4 is an enlarged and partially sectional top plan view of the machine, illustrating only some of the elements of the machine for greater clarity;

figure 5 is a schematic sectional view, similar to the preceding figures, of the machine according to the invention, illustrating a different embodiment of the means for adjusting the intensity of the force applied by the tensioning cylinder to the knitted fabric being formed, with the tensioning cylinder shown in the inactive position.

[0016] With reference to the above figures, the machine according to the invention, generally designated by the reference numeral 1, comprises a lower needle cylinder 2 and an upper needle cylinder 3 that are mutually coaxial and can be rotationally actuated about their common axis 4, which is arranged vertically.

[0017] In particular, the upper needle cylinder 3 is supported, so that it can rotate about the axis 4, by a supporting structure 5 by means of a main bearing 6. The rotary actuation of the upper needle cylinder 3 is achieved, in a known manner, by means of a motor, not shown for the sake of simplicity, that is connected to a gear 7 which is fixed coaxially to the upper needle cylinder 3.

[0018] A hollow suction cylinder 8 is arranged inside the upper needle cylinder 3 and coaxially thereto, rotates rigidly with the upper needle cylinder 3 about the axis 4, and is connected, at its upper open end, to a duct 9 that can be connected on command to a suction device. The lower end of the hollow suction cylinder 8, which is likewise open, faces the lower needle cylinder 2 and is located proximate to the knitting forming region 10.

[0019] The machine according to the invention is provided with a fabric tensioning device that comprises fabric retention means, which are conveniently constituted by a plug-like element 11 that is slideable, in a known manner, inside the lower needle cylinder 2 along the axis 4 to engage inside the lower end of the hollow suction cylinder 8 so as to lock the initial end of the fabric, which is sucked along the hollow suction cylinder 8.

[0020] The fabric tensioning device also comprises a tensioning cylinder 12 that is hollow and is open at its axial ends. The tensioning cylinder 12 is arranged internally and coaxially in the upper needle cylinder 3, around the hollow suction cylinder 8.

[0021] The tensioning cylinder 12 can move on command along the axis 4, and its lower end can engage, by virtue of its sliding along the axis 4, the knitted fabric 13 being formed. The retention means, constituted by the plug-like element 11, have dimensions that allow the movement of the tensioning cylinder 12 around the retention means; i.e., the diameter of the plug-like element 11 is smaller than the inside diameter of the tensioning cylinder 12, so that said cylinder can slide freely downward despite the presence of the plug-like element 11.

[0022] The fabric tensioning device also comprises actuation means that act on the tensioning cylinder 12 to cause its movement along the axis 4 and means for adjusting the intensity of the force applied by the actuation means to the tensioning cylinder 12 in a direction that is substantially parallel to the axis 4, at least during the tensioning of the knitted fabric being formed, so as to allow adjustment, according to the requirements, of the tensioning force to which the knitting is subjected during tensioning.

[0023] More particularly, inside the upper needle cylinder 3 and coaxially thereto there is a flanged tubular body 14 that is rigidly coupled to the upper needle cylinder 3 for example by means of a tab 15 that is provided at the gear 7.

[0024] The flanged tubular body 14 has, at its upper end, teeth 16 that engage axially inside axial slots 17 formed in the skirt of a tubular supporting body 18 mounted coaxially on the flanged tubular body 14.

[0025] A chamber 19 is formed between the tubular supporting body 18 and the hollow suction cylinder 8, and the tensioning cylinder 12 is accommodated inside it.

[0026] The tubular supporting body 18 is supported, so that it can rotate about the axis 4, through two bearings 20 and 21, by a casing 22 that surrounds the upper part of the upper needle cylinder 3 and is rigidly coupled to the supporting structure 5 of the machine.

[0027] Because of the connection provided between the teeth 16 and the slots 17, the tubular supporting body 18 rotates about the axis 4 rigidly with the flanged tubular body 14 and thus with the upper needle cylinder 3.

[0028] The tensioning cylinder 12 has, at its upper end, a flange 23 that is provided with a radially protruding tooth 24 for each one of the axial slots 17 of the tubular supporting body 18. The teeth of the flange 23 slidingly pass through the axial slots 17 and support a bearing 25 arranged coaxially to the tensioning cylinder 12. The bearing 25 connects the tensioning cylinder 12 to a slider 26 which is slideable inside vertical guides 27 formed in a block that is fixed laterally with respect to the casing 22.

[0029] The slider 26 is coupled to the guides 27 by means of pairs of bearings 28.

[0030] In this manner, the tensioning cylinder 12 rotates rigidly with the upper needle cylinder 3 about the axis 4 and is also connected to the slider 26. The slider 26 however can only move parallel to the axis 4.

[0031] The means for the actuation of the tensioning cylinder 12 along the axis 4 are advantageously constituted by a double-action fluid-actuated cylinder 30 that is supported by the casing 22, or by the supporting structure of the machine, and is arranged so that its axis is parallel to the axis 4.

[0032] The stem 31a of the piston 31 of the fluid-actuated cylinder 30 is connected to the slider 26, so that by feeding one of the feed ports 32 and 33 of the fluid-actuated cylinder 30 with a pressurized fluid, and by connecting the other feed port to the discharge, the slider 26 performs a translatory motion along the guides 27, i.e, the tensioning cylinder 12 performs a translatory motion along the axis 4.

[0033] The means for adjusting the intensity of the force applied to the tensioning cylinder 12 in a direction that is parallel to the axis 4 are conveniently constituted by a valve 40 for adjusting the feed pressure of the fluid-actuated cylinder 30; said valve is located along the feed duct 41 that is connected to the port 32, i.e., to the port 32 which, when fed with pressurized fluid, causes the lowering of the tensioning cylinder 12.

[0034] The port 33 is connected to another duct 42, and a slide valve 43 is arranged on the ducts 41 and 42 and selectively connects the duct 41 to a pressurized fluid line 44 while the duct 42 is connected to a discharge, or vice versa, so as to cause the downward or upward movement of the tensioning cylinder 12.

[0035] The adjustment means also comprise an auxiliary feed duct 45 that is connected, by means of a selector valve 46, to the feed duct 41 downstream of the adjustment valve 40 along the direction of the fluid that enters the fluid-actuated cylinder 30. The selector valve 46 connects the auxiliary feed duct 45 to the feed duct 41 when the pressure along the auxiliary feed duct 45 exceeds the pressure along the duct 41 upstream of the selector valve 46. The auxiliary feed duct 45 is connected to a line for feeding a pressurized fluid 47 through a slide valve 48 that can be actuated to connect the auxiliary feed duct 45 to the line 47 or to interrupt this connection.

[0036] Pressure sensing means are provided along the duct 41, downstream of the selector valve 46 and of the adjustment valve 40 along the direction of the fluid that enters the fluid-actuated cylinder 30; said means can be constituted for example by a pressure transducer 49.

[0037] The tensioning device also comprises means for sensing the movement of the tensioning cylinder 12 along the axis 4.

[0038] Said sensing means are conveniently constituted by two pulleys 51 and 52 that are arranged so that their axes are horizontal and aligned along a vertical plane. The two pulleys 51 and 52 are mutually connected by a toothed belt 53 that is fixed laterally to the slider 26, so that the sliding of the tensioning cylinder 12 causes a translatory motion of the toothed belt 53. The casing 54 that contains the belt 53 can be conveniently made of transparent material, and it is possible to place on the belt 53 an indicator 55 that abuts against a series of notches 56 provided on the casing, so as to allow the operator to visually check the movement of the tensioning cylinder 12.

[0039] The means for sensing the movement of the tensioning cylinder 12 may also be of the electronic type, i.e., constituted by an encoder 57 whose shaft is connected to the axis of one of the pulleys 51 or 52; in the illustrated case, to the pulley 52.

[0040] Means for sensing the upper and lower stroke limit position of the tensioning cylinder 12 are also arranged on the casing 22 and are conveniently constituted by two proximity sensors, designated by the reference numerals 71 and 72 respectively.

[0041] The force applied by the tensioning cylinder 12 to the fabric being formed can be adjusted manually by providing, for example, a device for visualizing the preset required force and a device for visualizing the force actually applied by the tensioning cylinder 12 to the fabric, which can be connected to the transducer 49 which, by sensing the feed pressure of the fluid-actuated cylinder 30, during the descent of the tensioning cylinder 12, also senses the force that is actually discharged onto the knitted fabric being formed.

[0042] The operator can act manually on the adjustment valve 40, so as to increase or decrease the feed pressure of the fluid-actuated cylinder 30 while said cylinder actuates the descent of the tensioning cylinder 12, so that the force actually applied by the tensioning cylinder 12 corresponds to the preset force.

[0043] The adjustment of the fabric tensioning force can also be fully automated, by providing an electronic monitoring and control element 60, constituted for example by a programmable microprocessor, whose input is connected to the pressure transducer 49, to the encoder 57, and to the proximity sensors 71 and 72. Said monitoring and control element 60 actuates the slide valve 43 and the slide valve 48 according to a preset program.

[0044] If fully automated adjustment of the tensioning force is provided, it is possible to adopt a feed layout such as the one shown in figure 5 for the fluid-actuated cylinder 30. As shown by this layout, a proportional valve 80 is placed on the feed duct of the port 32 of the fluid-actuated cylinder 30 and is controlled by the monitoring and control element 60; by means of said proportional valve, the monitoring and control element 60 is capable of varying the feed pressure of the cylinder 30 while said cylinder actuates the descent of the tensioning cylinder 12, according to a preset program.

[0045] With the layout shown in figure 5, no manual intervention on the part of the operator is required, since the monitoring and control element 60 is capable of independently handling the actuation of the fluid-actuated cylinder 30, increasing the tensioning force during the formation of the knitted fabric, as well as connecting, if required, the feed duct 41 directly to the pressurized fluid duct 47.

[0046] The operation of the machine with the knitted fabric tensioning device according to the invention is as follows.

[0047] In inactive conditions, as shown in particular in figure 1, the tensioning cylinder 12 is in the maximum lifting position, and this position is sensed by the proximity sensor 71 that faces the bearing 24. The tensioning cylinder 12 is kept in the lifted position by feeding pressurized fluid to its port 33, while the port 32 is connected to a discharge, as shown by the position of the slide valve 43 shown in figure 1.

[0048] Directly after the beginning of the formation of the knitted fabric, the initial flap of the knitted fabric is sucked inside the hollow suction cylinder 8 and the plug-like element 11 is raised, so as to clamp the initial end of the knitted fabric being formed, in cooperation with the lower end of the hollow suction cylinder 8. At this point, the monitoring and control element 60, which also handles the operation of the entire machine, switches the position of the slide valve 43, connecting the port 33 to the discharge and connecting the port 32 to the line 44, as shown in particular in figure 2.

[0049] In this manner, the tensioning cylinder 12 is actuated downward by the fluid-actuated cylinder 30 with a force that depends on the adjustment performed on the adjustment valve 40.

[0050] Furthermore, during the tensioning of the fabric, the descent of the tensioning cylinder 12 and therefore the length of the formed fabric is detected visually or by means of the encoder 55, as already described.

[0051] At any time, the tensioning force can be increased further, if required, by connecting the line 47 to the port 32, either by means of a manual action, with the embodiment of the device shown in figures 1 to 4, or in a fully automatic way, handled by the monitoring and control element 60, by means of the proportional valve 80.

[0052] It should be noted that the fabric tensioning device according to the invention, in addition to varying the tensioning force, according to the requirements, also allows to control the actual length of the formed knitted product. Accordingly, it is possible to provide for a connection of the monitoring and control element 60 to a device for adjusting the tightness of the knitting, in a per se known manner which is not illustrated for the sake of simplicity, so that the tightness of the knitting can be changed if the length of the product varies with respect to a preset length.

[0053] At the end of the treatment of the product, the plug-like element 11 is disengaged from the lower end of the hollow suction cylinder 8 so that the product is sucked upward inside the hollow suction cylinder 8 and moved away from the machine, while the feed of the fluid-actuated cylinder 30 is again reversed so as to cause the lifting of the tensioning cylinder 12 to return it to the inactive position. After the proximity sensor 71 has sensed that the inactive position has been reached by the tensioning cylinder 12, the cycle resumes as already described.

[0054] It should be noted that the proximity sensor 72 may also not be reached by the bearing 24 because the feed of the fluid-actuated cylinder 30 can be reversed before the tensioning cylinder 12 reaches its maximum downward position, due to a direct intervention of the monitoring and control element 60.

[0055] In practice it has been observed that the machine with the knitted fabric tensioning device according to the invention fully achieves the intended aim, since it allows to vary, in an extremely simple and quick manner and with high precision, the tensioning force to which the fabric is subjected during knitting.

[0056] Another advantage of the machine with the tensioning device according to the invention is that it is possible to increase the tensioning force during the formation of the knitted fabric.

[0057] Another advantage of the invention is that of allowing control of the actual length of the formed product.

[0058] The machine thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements.

[0059] In practice, the materials employed, as well as the dimensions, may be any according to the requirements and the state of the art.

[0060] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. Double-cylinder circular knitting machine for manufacturing socks, stockings and the like with a device for tensioning the knitted fabric, which comprises a lower needle cylinder and an upper needle cylinder which are mutually coaxial and can be rotationally actuated about their substantially vertical common axis, said needle cylinders internally accommodating a tensioning device for the knitted fabric being formed, which comprises: retention means for retaining the fabric proximate to a knitting forming region, and a tensioning cylinder, which is hollow and open at its axial ends, said tensioning cylinder being accommodated in said upper needle cylinder, and controllably movable along said axis, a lower end of said tensioning cylinder being engageable, by sliding along said axis, with the knitted fabric being formed, said retention means having a size that allows the movement of said tensioning cylinder about said retention means; characterized in that it comprises actuation means that act on said tensioning cylinder to move it along said axis and adjustment means for adjusting the intensity of the force applied by said actuation means to said tensioning cylinder in a direction that is substantially parallel to said axis, at least during tensioning of the knitted fabric being formed.

2. Machine according to claim 1, characterized in that said actuation means comprise a fluid-actuated cylinder, said adjustment means comprising means for adjusting the feed pressure of said fluid-actuated cylinder.

3. Machine according to claim 1, characterized in that a hollow suction cylinder is fixed coaxially inside said upper needle cylinder, said hollow suction cylinder having an open lower end facing proximate to the knitting forming region, and an open upper end connectable to suction means.

4. Machine according to one or more of the preceding claims, characterized in that said tensioning cylinder is arranged coaxially around said hollow suction cylinder and rotates about said axis rigidly with said upper needle cylinder.

5. Machine according to one or more of the preceding claims, characterized in that it comprises a tubular supporting body fixed internally and coaxially with respect to said upper needle cylinder and having a skirt provided with at least one axial slot, said tensioning cylinder having, proximate to said upper end thereof, a flange provided with at least one tooth that slidingly passes through said slot and is connected to a slider that is supported, so that it can slide parallel to said axis, by the supporting structure of the machine, said fluid-actuated cylinder being mounted on said supporting structure and acting on said slider with the stem of its piston.

6. Machine according to one or more of the preceding claims, characterized in that said flange is provided with a plurality of teeth, each of which passes slidingly through an axial slot formed in the skirt of said tubular supporting body, said teeth being distributed around the axis of said tensioning cylinder and connected to said slider with the interposition of a bearing arranged coaxially to said tensioning cylinder.

7. Machine according to one or more of the preceding claims, characterized in that it comprises means for sensing when said tensioning cylinder reaches an upper stroke limit position and a lower stroke limit position during motion along said axis.

8. Machine according to one or more of the preceding claims, characterized in that it comprises means for sensing movement of said tensioning cylinder along said axis.

9. Machine according to one or more of the preceding claims, characterized in that said means for sensing movement of said tensioning cylinder comprise: two pulleys having axes arranged horizontal and lying on a vertical plane, said two pulleys being supported so as to be rotatable about said axes by the supporting structure of the machine; a belt that mutually connects said two pulleys; and an encoder, which is connected to one of said two pulleys by means of its shaft.

10. Machine according to one or more of the preceding claims, characterized in that said adjustment means comprise a valve for adjusting the feed pressure of said fluid-actuated cylinder, said valve being located on a feed duct of said fluid-actuated cylinder that actuates the descent of said tensioning cylinder.

11. Machine according to one or more of the preceding claims, characterized in that said adjustment means comprise an auxiliary feed duct that is fed with a fluid at a pressure that is higher than the pressure to which said adjustment valve is set, said auxiliary feed duct being controllably connectable to said feed duct downstream of said adjustment valve to increase tensioning of the knitted fabric being formed.

12. Machine according to one or more of the preceding claims, characterized in that it comprises means for sensing the pressure of the fluid fed to said fluid-actuated cylinder during descent of said tensioning cylinder.

13. Machine according to one or more of the preceding claims, characterized in that it comprises a monitoring and control element for the electronic monitoring and control of said actuation means.

14. Machine according to one or more of the preceding claims, characterized in that said monitoring and control element is constituted by an electronic microprocessor.

15. Machine according to one or more of the preceding claims, characterized in that said means for sensing the movement of said tensioning cylinder are connected in input to said monitoring and control element.

16. Machine according to one or more of the preceding claims, characterized in that said monitoring and control element is connected to means for sensing the stroke limit position of said tensioning cylinder.

17. Machine according to one or more of the preceding claims, characterized in that said monitoring and control element has an input connected to said means for sensing the pressure of the fluid that is fed to said fluid-actuated cylinder.

18. Machine according to one or more of the preceding claims, characterized in that it comprises a monitoring and control element connected to a valve for connecting said auxiliary feed duct to said feed duct of said fluid-actuated cylinder.

19. Machine according to one or more of the preceding claims, characterized in that said monitoring and control element is connected to a device for adjusting the tightness of the knitted fabric being formed, whereby to vary the adjustment of the tightness of the knitted fabric being formed as a function of the sensed descent stroke of said tensioning cylinder that corresponds to the total length of the product.

20. Machine according to one or more of the preceding claims, characterized in that said adjustment means comprise a proportional pressure adjustment valve arranged along a feed duct of said fluid-actuated cylinder that actuates the descent of said tensioning cylinder, said proportional valve being actuated by said monitoring and control element.

Drawing