Secondary guidance system for linear induction motor

Abstract: A motor secondary (18) in a linear induction motor used for opening and closing doors in an elevator system includes a secondary guide system having first and second secondary guides (72). The first secondary guide is disposed on a bottom longitudinal edge (62) of the motor secondary and the second secondary guide is disposed on a top longitudinal edge (60) thereof. The guides space the motor secondary apart from the motor primary and establish small and constant running clearances therebetween.

Description: The present invention relates to elevator systems and, more particularly, to high performance linear induction motors driving elevator car doors. In conventional elevator systems, elevator car doors are selectively opened and closed by a rotary electric motor driving a mechanical assembly, which typically includes a plurality of moving parts such as gear boxes, a set of drive arms, and linkages. The major drawback of existing elevator car door systems is their susceptibility to misalignments which require frequent adjustments, resulting in high maintenance costs. Also, the misalignments degrade the performance of the system such that the door opening and closing functions are not consistently smooth and not always quiet. Linear motors potentially can provide an alternative to conventional door operating systems by eliminating the mechanical linkages and problems associated therewith. However, despite the fact that the use of linear motors on door systems has been disclosed in various patents, including U.S. Patent No. 1,881,014 to Ayers and U.S. Patent No. 5,172,518 to Yoshino, none of the prior art provides a practical door operating system for the elevator industry. Typically, linear motors include a motor primary and a motor secondary that cooperate to generate thrust forces to selectively open and close elevator car doors. One problem hindering the successful use of linear motors on elevator car doors is that of maintaining proper running clearances between the motor primary and the motor secondary of the linear motor. For efficient and high performance of linear motors, running clearances must remain constant and small during various modes of door operation. Fluctuations in the running clearance during operation of the door system will cause a change in the thrust of the motor and potentially can result in erratic motion of the doors. It is even more difficult to maintain constant and small running clearances between parts of the linear motor when the elevator car doors become misaligned or impacted. However, it is imperative to maintain small and constant running clearances between the motor primary and the motor secondary, even when elevator car doors deviate from their intended path. The majority of the existing prior art disclosing use of linear motors on elevator car doors relies primarily on guidance systems between parts of the motor, that include rollers. Although use of rollers in guidance systems is common, roller type guidance systems introduce many undesirable side effects and have many limitations. The undesirable side effects include generation of noise, high point concentration of loads caused by attracting forces, and transmission of vibrations from the motor. One of the primary limitations of roller type guidance systems is that during any type of misalignment or relative motion between the motor primary and the motor secondary, the rollers do not allow deviant movement and may skid. U.S. Patent No. 1,881,016 to Rose shows a motor secondary provided with a pair of shoes on the upper and lower edges thereof. The shoes are rigidly constrained within a guideway. Although the Rose patent eliminates many problems of the roller guidance systems, it still does not allow for any door misalignment in the vertical direction and would result in a jam when a door is misaligned or twisted. Therefore, it is desirable to provide a guidance system between a motor primary and a motor secondary that will compensate for door misalignment and that will still maintain a small, constant running clearance between the motor primary and the motor secondary. Viewed from one aspect the present invention provides an elevator system including an elevator car having a car door and a linear motor for opening and closing said elevator car door, said elevator car door being suspended from a door hanger, said door hanger being movably secured to a header fixedly attaching to said elevator car, said linear motor comprising: a motor primary secured to said door hanger and having a backiron and a primary winding spaced apart by a plurality of spacers; a motor secondary attaching to said header and fitting between said backiron and said primary winding of said motor primary, said motor secondary having a top longitudinal edge and a bottom longitudinal edge extending the length of said motor secondary, said motor secondary having a first vertical end and a second vertical end; a top secondary guide extending the length of said motor secondary and fitting over said top longitudinal edge; and a bottom secondary guide extending the length of said motor secondary and fitting over said bottom longitudinal edge, said first and second secondary guides allowing vertical movement of said motor primary relative to said motor secondary. The secondary guides establish small running clearances between the motor secondary and the motor primary, which are maintained throughout all operational modes of the elevator car doors. The secondary guides also allow vertical movement of the motor secondary relative to the motor primary, thereby allowing and compensating for possible elevator car door misalignment and twisting. Another advantage of the invention, at least in its preferred forms, is that the repelling force is distributed along the entire surface of each guide and thus provides a greater wearing surface which is not subject to extensive wear. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- FIG. 1 is a partially cut-away schematic perspective view of an elevator door system driven by a linear induction motor including a motor primary and motor secondary fitted with secondary guides, according to the present invention; FIG. 2 is a partially cut-away schematic cross-sectional view of the linear induction motor of FIG. 1 taken along the line 2-2; and FIG. 3 is an enlarged exploded fragmentary perspective view of the motor secondary fitted with the secondary guides of FIG. 2. Referring to FIG. 1, an elevator car door operating system 10 for opening and closing a pair of elevator car doors 12 that are suspended from a pair of door hangers 14 includes a pair of motor primaries 16 fixedly attached to the pair of door hangers and a motor secondary 18 attached to a header bracket 20 secured to a car facia 22 of an elevator car (not shown). Referring to FIG. 2, each of the motor primaries 16 includes a primary winding 28 and a backiron 30 spaced apart from each other by a plurality of motor spacers 32. The primary winding 28 includes a primary iron unit 34 with windings 36 wrapped around it and a primary surface 38 facing the backiron 30. The backiron 30 includes an iron plate 40 having a backiron surface 42 facing the primary winding 28. A magnetic air gap is defined between the primary surface 38 and the backiron surface 42. Each spacer 32 includes a spacer bar 48 framed by a spacer head 50 on each end thereof. Each spacer head 50 fixes the spacing between the primary winding 28 and the backiron 30. The spacer bar 48 includes a spacer surface 51 and is adapted to clamp the primary winding 28 against the door hanger 14. Each motor primary 16 is fixedly attached to its associated door hanger 14 by means of a plurality of bolts 52 passing through the backiron 30 and the motor spacer heads 50. The motor secondary 18 extends the length of the car door travel and fits between the backiron 30 and the primary winding 28 as the motor primaries 16 travel across, opening and closing the elevator car doors 12, as best seen in FIG. 1. The motor secondary 18 comprises a substantially flat plate having first and second faces 56,58 bounded by top and bottom longitudinal edges 60,62 extending the length of the motor secondary, and by first and second vertical ends 64,66. Both longitudinal edges 60,62 are bent over to form a lip 70 along the length of the second face 58 of the motor secondary 18, as best seen in FIGS. 2 and 3. Referring to FIG. 3, a secondary guide 72 is placed over each longitudinal edge 60,62 of the motor secondary 18. The secondary guide 72 has an elongated U-shaped body, the internal width of which is equal to the width of the doubled over edge 60,62 of the motor secondary. The U-shaped body includes a first leg 74 and a second leg 76 with the second leg 76 having vertical height substantially equal to the height of the bent over lip 70. The second leg also includes a tab 78 integrally formed at the end thereof. The secondary guide 72 is snapped onto each edge 60,62 of the motor secondary 18 with the tab 78 fitting over the bent over lip 70 and securing the secondary guide 72 onto the motor secondary 18. Referring to FIG. 2, the outside surface of the first leg 74 of the secondary guide 72 comes in contact with the backiron surface 42. The outside surface of the second leg 76 of the secondary guide 72 comes in contact with the spacer surface 51 of the spacer bars 32. Each spacer is dimensioned so that a running clearance is defined between the second face 58 of the motor secondary 18 and the primary surface 38. The spacer surface 51 of the spacer bar 32 is indented from the plane of the primary surface 38 of the motor primary 16 to compensate for the thickness of the lip 70 of the motor secondary 18. Therefore, the running clearances between the backiron surface 42 and the first face 56 of the motor secondary and between the primary surface 38 and the second face 58 of the motor secondary equal the thickness of the first and second legs 74,76 of the secondary guide, respectively. The motor secondary 18 is movably attached to the header bracket 20 at two ends 64,66 thereof, as best seen in FIG. 1. The motor secondary 18 is mounted to the header bracket 20 by means of a joint 82 functioning as a standoff to allow the backiron to travel between the header bracket and the motor secondary. The joint 82 also includes a swivel allowing the motor secondary to move in and out of plane and to rotate about the joint 82. In operation, as the motor primaries 16 move across the motor secondary 18, opening and closing elevator car doors 12, the running clearances between the backiron 30 and the motor secondary 18 and between the motor secondary 18 and the primary winding 28 are maintained constant and small. The secondary guides 72 establish a predetermined spacing by holding the flat surface 42 of the backiron and the primary surface 38 of the primary winding 28 away from the motor secondary 18. As the motor primaries 16 move across the motor secondary 18, the secondary guides 72 come in contact with the backiron surface 42 on one side and with the spacer surface 51 on the other side. Thus, the secondary guides 72 space apart the first and second motor secondary surfaces 56,58 from the backiron surface 42 and primary surface 38, respectively. The contact between the secondary guides 72 and the backiron surface 42 and the spacer surface 51 remains steady throughout all modes of operation because the distance between the backiron surface and the spacer surface has been fixed by the spacer heads. It is critical to maintain running clearances between the motor secondary 18 and the motor primary 16 to avoid friction therebetween. However, it is imperative to keep these running clearances to a minimum so that the magnetic air gap remains small. Larger magnetic air gaps reduce motor efficiency. A major advantage of the secondary guides 72 over the prior art is an ability to allow and compensate for vertical movement of the motor primary 16 relative to motor secondary 18. In circumstances where the elevator car doors 12 are either impacted or misaligned and the door hangers 14 with the motor primaries 16 thereon are thereby displaced vertically, the running clearances are not changed and the performance of the motor and consequently of the doors is not affected. This goal is achieved by providing the specific configuration shown herein and by dimensioning the motor secondary 18 to have additional vertical space to move in. Since the backiron surface 42 and the spacer bar surfaces 51 are substantially flat, when the motor primary 16 moves vertically relative to motor secondary 18, the secondary guides 72 still maintain constant running clearances, regardless of the vertical position of the motor secondary 18 to the motor primary 16. One benefit of the present embodiment is that the secondary guides 72 are snapped on the motor secondary 18 and do not require time consuming and complicated assembly. Also, the secondary guides do not require subsequent readjustment. Another benefit of the secondary guides is that only minimal wear is experienced. An additional benefit of the present embodiment is that it does not generate noise. The secondary guides are made of a high density polymer. Although a variety of high density polymers are acceptable, such as Acetron, UHMW and Nylatron, lengthy research and testing has proved Nylatron to be the best. The thickness of each leg 74, 76 of the secondary guide 72 is approximately 1mm. However, the thickness of the guide 72 can vary depending on the size of the desired running clearance. While the present invention has been illustrated and described with respect to a particular embodiment thereof, various modifications may be made. For example, although the illustrated embodiment has a single secondary guide for each longitudinal edge, a plurality of shorter secondary guides may be placed on each longitudinal edge adjacent to each other.

Claims: An elevator system including an elevator car having a car door (12) and a linear motor for opening and closing said elevator car door (12), said elevator car door being suspended from a door hanger (14), said door hanger being movably secured to a header (20) fixedly attaching to said elevator car, said linear motor comprising: a motor primary (16) secured to said door hanger and having a backiron (30) and a primary winding (28) spaced apart by a plurality of spacers (50); a motor secondary (18) attaching to said header (20) and fitting between said backiron and said primary winding of said motor primary, said motor secondary (18) having a top longitudinal edge (60) and a bottom longitudinal edge (62) extending the length of said motor secondary, said motor secondary (18) having a first vertical end (64) and a second vertical end (66); a top secondary guide (72) extending the length of said motor secondary (18) and fitting over said top longitudinal edge; and a bottom secondary guide (72) extending the length of said motor secondary (18) and fitting over said bottom longitudinal edge, said first and second secondary guides (72) allowing vertical movement of said motor primary (16) relative to said motor secondary (18). A system according to claim 1, wherein each said secondary guide (72) has a U-shaped body. A system according to claim 2, wherein: said motor secondary (18) includes a first face (56) and a second face (58), with top and bottom lips (70) bent over onto said second face thereof, said lips (70) extending the length of said motor secondary (18); and said U-shaped body of each said secondary guide (72) having a first leg (74) and a second leg (76), said second leg (76) extending the height of said lips (70) and having a tab (78) integrally formed on the end thereof so that said secondary guide (72) can be snapped onto a said longitudinal edge of said motor secondary. A system according to any of claims 1 to 3, wherein said secondary guides (72) are made of Nylatron. An elevator car door operating system for opening and closing an elevator car door (12), said system including a linear motor, said linear motor including a motor primary (16) and a motor secondary (18) cooperatingly movable past each other to generate thrust to open and close said elevator car door, said system further comprising: a secondary guide system having first and second secondary guides (72), and characterised in that : said secondary guides (12) establish a running clearance between said motor primary (16) and said motor secondary (18) and allow vertical movement therebetween. A system according to claim 5, wherein said first and secondary guides (72) are made of Nylatron. A linear motor for driving an elevator car door in an elevator system and comprising a secondary guide system spacing apart a motor secondary (18) from a motor primary (16), said secondary guide system comprising: a plurality of secondary guides (72) extending the length of said motor secondary (18) and placed on top and bottom longitudinal edges (60,62) of said motor secondary (18), and characterised in that : said secondary guides (72) space said motor secondary (18) from said motor primary (16) and allow vertical movement of said motor primary relative to said motor secondary. A linear motor according to claim 7 wherein said motor primary (16) includes a backiron (30) and a primary winding (28) spaced apart by a plurality of spacers (50) and wherein said motor secondary (18) is provided fitting between said backiron and said primary winding (28) of said motor primary. A linear motor according to claim 7 or 8 wherein each said secondary guide (72) has a U-shaped body. A linear motor according to claim 9, wherein said motor secondary (18) includes a first face (56) and a second face (58), with top and bottom lips (70) bent over onto said second face thereof, said lips extending the length of said motor secondary (18) and said U-shaped body of each said secondary guide (72) having a first leg (74) and a second leg (76), said second leg (76) extending the height of said lip and having a tab (78) integrally formed on the end thereof so that said secondary guide can be snapped onto a said longitudinal edge of said motor secondary.

Inventors: RIVERA JAMES A, TRACEY MICHAEL J, RIVERA, JAMES A., TRACEY, MICHAEL J.
Applicants: OTIS ELEVATOR CO, OTIS ELEVATOR COMPANY
Application year: 1997
Main classification: B66B13
IPC codes: E05F15, B66B13, H02K41