Apparatus and method for forming a screw flight

Abstract

This invention relates to an apparatus for forming a helical screw flight from a flight blank. The apparatus includes a base and an engaging means. The engaging means is movably mounted to the base and is configured to formingly engage the blank so as to form a twist in at least a portion of the flight blank corresponding to a predetermined pitch of the flight.

Claims

1. An apparatus for forming a helical screw flight from an open ended annulus shaped blank, the apparatus including: a base; a fixed mounting frame arranged on the base; a pair of selectively interchangeable fixed side plates releasably mounted to the fixed mounting frame so as to be angled relative to one another, wherein the angle between the fixed side plates is less than 90 degrees, and wherein each fixed side plate has an engaging portion for engaging a first side of the annulus shaped blank along a line normal to a mean radius line of the annulus shaped blank; a movable mounting frame arranged on the base, the movable mounting frame being selectively movable relative to the fixed mounting frame; and a pair of selectively interchangeable movable side plates releasably mounted to the movable mounting frame so as to be angled relative to one another, wherein the angle between the movable side plates is such that the movable side plates are aligned with the corresponding fixed side plates, and wherein each movable side plate has an engaging portion for engaging an opposed second side of the annulus shaped blank along a line normal to a mean radius line of the annulus shaped blank; wherein, the fixed and movable plates are adapted to formingly engage the blank upon movement of the movable mounting frame towards the fixed mounting frame, thereby forming a twist in at least a portion of the flight blank between the side plates.

2. An apparatus according to claim 1, including a secondary engaging element for engaging the blank at at least one position between the respective pairs of side plates.

3. An apparatus according to claim 2, wherein the secondary engaging element engages the blank at a mid-point between the respective pairs of side plates.

4. An apparatus according to claim 3, wherein the secondary engaging element includes a pair of mid-plates.

5. An apparatus according to claim 4, wherein the mid-plates include a fixed mid-plate releasably mounted to the fixed mounting frame and a movable mid-plate releasably mounted to the movable mounting frame, whereby the movable mid-plate is movable relative to the fixed mid-plate.

6. An apparatus according to claim 5, wherein the fixed and movable mid-plates are respectively adapted to engage the first and second sides of the annulus shaped blank along a line normal to the mean radius line of the blank.

7. An apparatus according to claim 1, wherein the angle between the fixed side plates is 60 degrees.

8. An apparatus according to claim 1, wherein the angle between the fixed side plates is 30 degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 is a perspective view of an apparatus for forming a helical screw flight according to the invention;

(3) FIG. 2 is a plan view of the flight forming apparatus of FIG. 1;

(4) FIG. 3 is a left side view of the apparatus;

(5) FIG. 4 is a front elevation of the apparatus;

(6) FIG. 5 is a plan view of the apparatus with the sheet metal panel cover removed;

(7) FIG. 6 shows an annulus shaped flight blank;

(8) FIG. 7 is a side view of a formed helical screw flight;

(9) FIG. 8 is a view of the formed flight of FIG. 7 from another side;

(10) FIG. 9 shows the fixed mounting frame of the apparatus with the mid-plate fixed in position, and a set-up rule assembly mounted to the mid-plate;

(11) FIG. 10 is an enlarged view of the mid-plate of FIG. 9, showing the alignment with the rule-assembly;

(12) FIG. 11 shows the base offset between each fixed side plate and the mid-plate, and the support offset for a support bracket mounted to a side plate;

(13) FIG. 12 is an enlarged view of a rule guide used with rule-assembly for setting the base offset;

(14) FIG. 13 is a perspective view of the rule guide of FIG. 12;

(15) FIG. 14 is schematic view showing setup of the fixed side plates;

(16) FIG. 15 is an enlarged side view of FIG. 14;

(17) FIG. 16 is a perspective view showing setup of the a support bracket;

(18) FIG. 17 is an enlarged view of the support bracket setup of FIG. 16;

(19) FIG. 18 is a side view of the engaging means showing the primary and secondary engaging plates in forming engagement with the blank;

(20) FIG. 19 is a side view of the engaging means with the hydraulic cylinder in a partially extended position such that a roll gap exists between the fixed and movable plates to enable manipulation of the blank;

(21) FIG. 20 is a side view of the engaging means with the hydraulic cylinder in its retracted position to enable insertion of a blank and extraction of a formed flight;'and

(22) FIG. 21 is a side view of a side engaging plate.

PREFERRED EMBODIMENTS OF THE INVENTION

(23) Referring to the drawings, the invention provides an apparatus 1 for forming a helical screw flight 2 from an open ended annulus shaped flight blank 3. As most clearly shown in FIG. 6, the annulus shaped blank 3 has an inner diameter and an outer diameter.

(24) The size of the blank 3 is calculated from the values of the desired properties of the helical flight 2 including the inner and outer diameters of the flight 2, the pitch of the flight (FIG. 7) and the thickness of the material used to form the blank/flight (FIG. 8). It will be appreciated by those skilled in the art that the inner and outer diameters of the blank 3 are necessarily greater than those of the formed flight 2.

(25) The flight forming apparatus 1 has a base 4 for resting the apparatus 1 on a supporting surface such as a workshop floor (not shown).

(26) The apparatus 1 includes a mounting means in the form of a mounting frame 5 fixedly connected to the base 4. The fixed mounting frame 5 is configured for mounting a fixed engaging means in the form of two spaced apart side plates 6 and a central or fixed mid-plate 7. As will be described in further detail below, the fixed side plates 6 and the fixed mid-plate 7 are arranged to engage respective spaced apart positions on a first side surface 8 of the flight blank 3.

(27) The fixed mounting frame 5 includes a mounting plate 9 having a receiving formation in the form of three channels 10 for selectively and releasably receiving each fixed plate (6, 7). The channels 10 include a pair of spaced apart side channels for receiving the fixed side plates 6 and a central channel for receiving the fixed mid-plate 7.

(28) As most clearly shown in FIG. 9, the side channels 10 are symmetrically arranged on either side of the central channel and extend radially at an angle of approximately 60 degrees relative to each other. The side plates 6 and mid-plate 7 can be inserted into and slid along the respective channels 10 to a desired position so as to suit a particular size flight blank 3 and desired pitch of the flight 2.

(29) To engage the opposite second side 11 of the blank 3, the apparatus 1 further includes movable engaging means mounted to a movable frame or carriage 12. The carriage 12 is adapted for relative linear sliding movement with respect to the fixed frame 5.

(30) The carriage 12 has a mounting plate 13 with a receiving formation in the form of three channels 14 for selectively and releasably receiving the movable engaging means.

(31) The movable engaging means is in the form of two movable side plates 15 and a movable mid-plate 16. The channels 14 of the movable mounting plate 13 are arranged to correspond with (or mirror) the channels 10 of the fixed mounting plate 5.

(32) The two pairs of side plates (6, 15) together for a primary engaging means and the pair of mid-plates (7, 16) form a secondary engaging means of the apparatus.

(33) The side and mid-engaging plates (fixed and movable) are preferably die formed components having an engaging edge 17 for engaging the respective surfaces of the blank 3. Each engaging plate is configured so that when it is inserted into its associated channel the engaging edge 17 extends radially, relative to the flight blank 3, so as to be substantially normal to the mean radius line of the blank 3.

(34) As most clearly shown in FIG. 21, each side plate (fixed and movable) is generally trapezoidal in shape and has a mounting formation in the form of a stepped or tongue-shaped edge 18 which can be received in the relevant side channel (10, 14) of the fixed or movable mounting plate (5, 13). The engaging edge 17 is tapered relative to the mounting formation so as to extend at a predetermined die plate angle relative to the mounting edge 18. The die plate angle is calculated to suit the desired pitch of the flight 2. Accordingly, it will be appreciated that sets of engaging plates with various die plate angles can advantageously be manufactured and used, interchangeably, as required to manufacture helical flights 2 of various pitches.

(35) In order to achieve the desired rotation (twist) of the blank 3 at the points held between the side plates, one pair of side plates are arranged such that the tapered edges 17 of the fixed and movable plates in this pair are substantially parallel and extend at a negative angle. Similarly, the second pair of side plates is arranged such that the tapered edges 17 of the fixed and movable plates in this pair are substantially parallel and extend at a positive angle.

(36) It will therefore be appreciated that, due to the tapered engaging edges 17 of the side plates, the relative linear movement between the fixed and movable side plates results in a rotation of the part of the blank between the side plates about the mean radius line to produce the desired twist in the blank. In the figures, the front pair of side plates extend at a negative angle and are therefore configure to rotate that portion of the blank in a counter-clockwise direction. The rear pair of side plates extend at a positive angle and are therefore configure to rotate that portion of the blank in a clockwise direction. It will of course be appreciated by those skilled in the art that the plates can be readily interchanged so the front and rear pairs of side plates extend at opposite angles to produce a flight of different hand (e.g. a left or right hand flight).

(37) To secure the mid-plates (7, 16) in position, a locking means in the form of a lock-bolt 31 (FIG. 9) is provided for locking the mid-plates relative to the respective mounting plates (9, 13).

(38) With reference to FIGS. 9 to 17, once the mid-plates (7, 16) are securely locked in position, a set up device having a mounting bracket 19 and a pair of oppositely directed rulers 20 is mounted on the mid-plate (7, 16). The set up device is used to determine the correct positioning of the side plates (6, 15) in their respective side channels, relative to the mid-plate. As best seen in FIG. 11, the engaging edge 17 of the side plates are positioned at a predetermined base offset distance from the mid-plate. As the side plates (6, 15) are oppositely tapered, the side plate on the right of FIG. 11 is slid downwardly along its channel (10, 14) until its engaging edge 17 meets the ruler 20 at the base offset distance. Due to the opposite taper, the side plate on the left of FIG. 11 is slid upwardly along its channel (10, 14) until its engaging edge 17 meets the ruler 20 at the base offset distance.

(39) The side plates (6, 15) are secured in position in the respective channels (10, 14) by securing means in the form of a plurality of locking screws 21. The locking screws 21 pass through holes 22 in the side wall 23 of the channel and securingly engage the mounting tongue 18 of the associated side plate (6, 15). In the illustrated embodiment, as best seen in FIG. 11, seven locking screws 21 are used to secure each side plate (6, 15).

(40) Referring again to FIG. 11, a support means in the form of a pair of support brackets 24 is provided for supporting the flight blank 3, in use. One support bracket 24 is attached to the fixed side plate of the first pair of primary engaging plates and a second support bracket is attached the movable side plate of the second pair of primary engaging plates. The support brackets 24 are selectively adjustably positionable relative to the associated side plate and secured thereto by a suitable locking means in the form of locking bolts 25. In the illustrated embodiment, three locking bolts 25 are used to secure the support bracket 24 to the associated side plate (6, 15). As most clearly shown in FIG. 21, the side plates (6, 15) have three apertures 26 through which the locking bolts 25 pass to hold the support bracket 24 relative to the side plate (6, 15).

(41) The apparatus 1 further includes an actuating means in the form of a hydraulically driven cylinder 27 having a cylinder rod 28 coupled to the carriage 12. The coupling arrangement is such that movement of the cylinder rod 28 causes a corresponding linear movement of the carriage 12. The movement of the cylinder rod 28 is selectively controllable between an extended position and a retracted position so as to control the relative spacing between the fixed and movable plates of the primary and secondary engaging means.

(42) To facilitate the forward and backwards linear movement of the movable frame 12 and, in particular, to enhance the accuracy of this movement, front and rear guide bars 29 are fitted to and extend from the carriage 12. The front and rear guide bars 29 are arranged to slidably pass through guide sleeves 30 fixed on or relative to the base 4.

(43) In use, the apparatus 1 is initially started with the cylinder rod 28 in its retracted position to enable a new flight blank 3 to be placed between the fixed and movable engaging plates (6, 7, 15, 16). The cylinder rod 28 is then extended to move the carriage 12 to an intermediate position between the fully retracted and extended positions. In the intermediate position, the blank 3 can be supported on the support brackets 24.

(44) The cylinder rod 28 is then actuated to extended at a predetermined forming speed to bring the side and mid-plates into forming engagement with the respective surfaces (8, 11) of the blank 3. The plates are configured such that the front pair of side plates rotate the portion of the blank between that pair of side plates and the mid-plates in a counter-clockwise direction, and the rear pair of side plates is configured to rotate the portion of the blank between that pair of side plates and the mid-plates in a clockwise direction.

(45) As the engaging plates extend substantially normal to the mean radius line of the annulus, the rotation induced by the engaging plates forms a twist in the engaged portion of the annulus about the mean radius line of the annulus. It will be appreciated by those skilled in the art that, by twisting the blank about its mean radius line, undesirable rounding, coning or rolling across the cross-section of the blank is substantially avoided.

(46) Once the form twisting process has been done, the cylinder rod 28 is retracted to its intermediate position and the blank 3 is rolled on the support brackets 24 to bring the next section of blank into position and the forming process is repeated. These steps are repeated until the entire blank 3 has been twisted and the helical flight 2 is complete.

(47) Accordingly, the present invention in various embodiments thus overcomes a number of problems and provides a number of advantages. Preferred embodiments of the invention provide an efficient apparatus for forming a helical screw flight which, due to the use of interchangeable engaging plates, enables flights of various sizes, pitches and hands to be readily formed in a cost effective manner. The interchangeable plates also provide advantages in terms reduced tooling costs as sets of plates can be produced and used as desired. Set-up times are also reduced with further associated cost saving advantages through the reduction in the manual labour input required. By engaging the blank in a radial manner, the apparatus advantageously forms the desired twist in the blank around the mean radius line without plastically working the blank. The radial engagement also advantageously inhibits undesirable rolling, rounding or coning of the edges which can adversely affect material transfer and flow rates. Preferred forms of the apparatus are easy to install, set up and use and provide improvements in accuracy to design requirements. In these and other respects, the invention in its preferred embodiments, represents a practical and commercially significant improvement over the prior art.

(48) Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.