Patent Application
20110139548
1. Field of the Invention
The present invention relates generally to belt-driven transportation systems, and particularly to such systems configured as lift assemblies and conveyor assemblies.
2. Description of the Related Art
Transportation systems such as lift assemblies are well known for moving items or people between two vertically differing locations. Transportation systems such as conveyor assemblies are well known for moving items or people between two horizontally differing locations. It is also known to move the platform or carriage of these systems through a belt-driven apparatus.
One well-known and useful type of lift assembly is the scissor-type, which moves between a lowered or contracted state, and an elevated or extended state as its load-supporting platform is moved between differing vertical locations. Such lift assemblies are commonly driven through hydraulic cylinders, screw-drive mechanisms or expandable pneumatic bladder arrangements, and some prior types of scissor lift assemblies are belt-driven. These prior lift assemblies, however, often require a substantial amount of power, particularly when moving from their lowermost contracted states, or are difficult to reliably, precisely control.
Further, some prior belt-driven transportation systems can be problematic to install or repair, and sometimes to operate, due to the belt being moved out of its guided position along its designed path over pulleys that it engages. Another problem with some types of belt-driven transportation systems is that they rely on traction between the belt and the pulleys to operate, which can lead to slippage under heavy loading and result in unintentional lift collapse. Additionally, some transportation systems of the types described above, particularly lift assemblies, undesirably require operating space that cannot be easily accommodated or interferes with carrying out the operation to which the system is applied. For example, some prior lift assemblies have platform heights in their fully contracted states that require the load to first be lifted a substantial vertical distance from the level of a floor, on which the base is positioned, to place it on the platform. Thus, it would be preferable to minimize the height of the platform in its fully contracted or lowered state.
A transportation system configured as a lift assembly or conveyor assembly that addresses at least one of the above-mentioned problems is desirable.
The present invention provides a scissors-type lift assembly including a base and a platform, the lift assembly having elevated and lowered states in which the platform and base are distant and proximate, respectively. The lift assembly further includes a pair of first and second scissor arms each having upper and lower ends respectively coupled to the platform and the base, the pair of scissor arms pivotably connected to each other intermediate their respective upper and lower ends about a central pivot axis. Also provided are a first pulley arrangement that includes at least one first pulley disposed about a first pulley axis, and a second pulley arrangement that includes at least one second pulley disposed about a second pulley axis, the first and second pulley axes disposed in a pulley plane and having lateral movement relative to each other as the lift assembly is moved between its elevated and lowered states, the pulley plane fixed relative to the base. A spool is rotatable about an axis fixed to the base, and a unitary belt is guided through a path defined by the first and second pulleys. The belt has opposed first and second ends, the belt first end engaged with the spool onto which the belt is wound and from which the belt is unwound. The first and second pulley axes have a first lateral distance therebetween in the lift assembly elevated state and a second lateral distance therebetween greater than the first distance in the lift assembly lowered state, and the first and second pulley axes pulled laterally together by the belt as it is wound onto the spool.
The invention further provides a scissors-type lift assembly including a base and a platform, the lift assembly having extended and contracted states with the platform at a relatively greater distance from the base in the extended state than in the contracted state. The lift assembly further includes a pair of first and second elongate arms each having opposite ends and extending between the base and the platform. The first and second arms are pivotably connected together and cross each other substantially at a first angle in the extended state and substantially at a second angle in the contracted state. Also included are a first pulley arrangement including at least one first pulley rotatably disposed about a first pulley axis, and a second pulley arrangement including at least one second pulley rotatably disposed about a second pulley axis, the first and second pulley axes defining a stationary plane in which the first and second pulley axes have relative lateral movement. One of the first and second pulley arrangements is affixed to one of the first and second elongate arms, and the arms are moved between the first and second angles with relative lateral movement of the pulley axes. A spool is rotatable about an axis of rotation fixed relative to the base, and a unitary belt is guided through a path defined by the first and second pulleys, the belt having opposed first and second ends. The belt first end is engaged with the spool onto which the belt is wound and from which the belt is unwound, and the first and second pulley axes are moved laterally in opposite directions relative to each other as the belt is respectively wound onto and unwound from the spool.
The present invention further provides a lift assembly including a base, a platform, and a pair of first and second elongate scissor arms each having a first end coupled to the base and a second end coupled to the platform, the first and second scissor arms pivotably connected to each other at a location between their respective first and second ends. The lift assembly further has a belt and pulley apparatus that includes a unitary belt having opposite first and second ends, a belt spool rotatably attached to the base and having reversible rotation about a spool axis. The belt first end is secured to the spool, and the belt second end is secured to the base. The belt is respectively wound onto and unwound from the spool with reversing rotation of the spool. Also included are a first pulley arrangement having a plurality of first pulleys disposed about a first axis, and a second pulley arrangement having at least one second pulley disposed about a second axis fixed relative to the base. The first and second axes are substantially parallel with each other and laterally movable relative to each other in a stationary plane, with the first axis fixed to one of the first and second scissor arms.
The present invention further includes a belt-driven transportation system including a first set of pulleys rotatably attached to a first member and a second set of pulleys rotatably attached to a second member. The first and second members have relative movement to each other. The system further includes a unitary belt that is guided through a path defined by the first and second sets of pulleys with the path substantially lying in a stationary plane, and a plurality of retention rollers. A retention roller is disposed adjacent each pulley, with the belt extending about the pulley and between the pulley and the retention roller. The positioning of the belt substantially on the path is maintained by the plurality of retention rollers, and the first and second members are moved relative to each other with changes in the length of the path.
There has thus been outlined, rather broadly, certain features of embodiments of the invention in order that the detailed descriptions thereof may be better understood, and in order that the present contribution to the art may be better appreciated. Additional or alternative features of embodiments of the invention are described in further detail below.
In this respect, before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
To accomplish the above and related objects, the invention may be embodied in the forms illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific constructions illustrated. Moreover, it is to be noted that the accompanying drawings are not necessarily drawn to scale or to the same scale. In particular, the scale of some of the elements of the drawings may be exaggerated to emphasize characteristics of the elements.
Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
Referring
Disposed between and operatively connected to base 22 and platform 24 is scissor arm assembly 30 which includes first pair of scissor arms 32 and second pair of scissor arms 34. Between the first and second pair of scissor arms is brace 36, which extends between first arm 38 of each of the first and second pairs of scissor arms 32, 34. The first and second pairs of scissor arms 32 and 34 each further includes second arm 40. Arms 38, 40 may be made of steel. Upper end 42 of each first and second arm 38, 40 engages platform 24, and lower end 44 of each first and second arm 38, 40 engages base 22. Respective to each pair of scissor arms 32, 34, first and second arms 38, 40 are pivotably connected to each other through a bolted connection 46 about pivot axis 48 of scissor arm assembly 30.
Each first arm 38 has a bolted connection 50 to platform 24, which defines pivot axis 51, and each second arm 40 has a bolted connection 52 to base 22, which defines pivot axis 53. Base 22 includes guide tracks 54 in which lower ends 44 of the first arms 38 are slidably engaged, and platform 24 includes guide tracks 56 in which upper ends 42 of second arms 40 are slidably engaged.
Lift assembly 20 further includes first pulley arrangement 58 which is connected to brace 36 with bolts 60. First pulley arrangement 58 includes a plurality of pulleys 62. Five pulleys 62, identified as pulleys 62a through 62e in
Adjacent pulleys 62 may have therebetween a bushing or other friction reducing member (not shown) to facilitate their independent rotation relative to each other about shaft 64. Each of pulleys 62 has opposing flanges 70 between which is defined a belt engaging circumferential pulley surface 330 discussed further below in connection with
First pulley arrangement 58 further includes shaft 72 that is parallel with shaft 64, and about which are disposed independently rotatable retainer rollers 74, one for each of pulleys 62. Shaft 72 also extends between and is fixed to laterally spaced blocks or support members 66 and 68. Thus, pulleys 62 and retainer rollers 74 are respectively rotatable about parallel axes of rotation 76 and 78 respectively defined by shafts 64 and 72. It is thus understood that first pulley arrangement 58 moves relative to base 22 with first scissor arms 38 as lift assembly 20 is moved between its elevated and lowered states 26, 28.
Base 22 includes laterally extending cross braces 80, 82, and 84 which extend between and are fixed to its opposite rails 85, 86. Attached to cross brace 82 is second pulley arrangement 88, which is fixed to base 22 by means of bolts 90. Second pulley arrangement 88 includes a plurality of pulleys 92. Four pulleys 92, identified as pulleys 92a through 92d in
Adjacent pulleys 92 may have therebetween a bushing or other friction reducing member (not shown) to facilitate their independent rotation relative to each other about shaft 94. Each of pulleys 92 has opposing flanges 100 between which is defined a belt engaging circumferential pulley surface 330 discussed further below in connection with
Second pulley arrangement 88 further includes shaft 102 that is parallel with shaft 94, and about which are disposed independently rotatable retainer rollers 104, one for each of pulleys 92. Shaft 102 also extends between and is fixed to laterally spaced blocks or support members 96 and 98. Thus, pulleys 92 and retainer rollers 104 are respectively rotatable about parallel axes of rotation 106 and 108 respectively defined by shafts 94 and 102.
Lift assembly 20 further includes motor drive assembly 112, which includes reversible servo or stepper motor 114, which is in driving, co-axial engagement with spool or pulley 116, which has opposed flanges 118 between which is defined a belt engaging portion. Unitary belt 120 having opposite first and second ends 121, 122 is guided along a path defined by pulleys 62 and 92, and first end 121 of belt 120 is connected to spool 116 such that rotation of the spool about its axis of rotation 124 will either wind belt 120 onto the spool or unwind belt 120 from the spool. Spool axis of rotation 124 is substantially parallel with pulley axes 76 and 106.
A plane 126 is defined by pulley axes 76 and 106, and maintains a substantially horizontal orientation, parallel with platform surfaces 25. As best seen in
Referring now to
Referring to
One of ordinary skill in the art will recognize that first pulley arrangement 58, which is attached by its blocks 66 and 68 to scissor arm assembly 30, is biased rightwardly as shown in
As belt 120 is wound onto spool 116, the length of the path along which belt 120 is guided about pulley 62 and 92 becomes shortened, and axes 106 and 76 are moved laterally within plane 126 towards one another as the lower ends 44 of first arms 38 are moved leftwardly towards lower ends 44 of second arms 44, thereby changing the angle at which the elongate first and second arms 38, 40 are crossed, and platform 24 is moved upwardly towards its elevated state 26.
Conversely, as belt 120 is unwound from about spool 116, the weight of scissor arm assembly 30, platform 24, and any load it bears, urges scissor arm assembly 30 towards a collapsed state, in which the angle at which the elongate first and second scissor arms 38, 40 are crossed changes such that first pulley arrangement 58 is moved rightwardly away from second pulley arrangement 88, and lift assembly 20 is moved towards its lowered state 28.
Referring now to
Scissor lift assembly 20A includes a motor drive assembly 112 in which reversible servo or stepper motor 114 is oriented along a drive axis 134 that is substantially perpendicular to spool drive axis 124, the output shaft of motor 114 extending into a gear drive unit in which the spool driving output shaft that defines axis 124 extends laterally in opposite directions from the gear drive housing. Each laterally extending end of the output shaft has a spool 116 affixed thereto. As best shown in
In second embodiment scissor lift assembly 20A, the first and second pulley arrangements 58, 88 are disposed between the first and second scissor arms 38, 40 of the first and second pairs of scissor arms 32, 34. First pulley arrangement 58 includes a pulley arrangement 58a associated with first drive belt 120a and another pulley arrangement 58b associated with second drive belt 120b. The pulleys 62 of each first pulley arrangement 58a and 58b are independently rotatably disposed on a common shaft 64 extending between and fixed to laterally spaced blocks or support members 66 and 68. Shaft 64 defines axis 76 about which pulleys 62 rotate. At each of the opposite ends of shaft 64, between the laterally outermost pulleys 62 and the adjacent block 66, 68, there is provided a cam follower or roller rotatable about axis 96. Cam followers 140 and 142 respectively engage the rightwardly-facing edges of the first and second pairs of scissor arms 32 and 34, as shown in
Similarly, second pulley arrangement 88 includes a pulley arrangement 88a associated with first drive belt 120a and another pulley arrangement 88b associated with second drive belt 120b. The pulleys 92 of each second pulley arrangement 88a and 88b are independently rotatably disposed on a common shaft 94 extending between and fixed to laterally spaced blocks or support members 96 and 98. Shaft 94 defines axis 106 about which pulleys 92 rotate. At each of the opposite ends of shaft 94, between the laterally outermost pulleys 92 and the adjacent block 96, 98, there is provided a cam follower or roller rotatable about axis 106. Cam followers 144 and 146 respectively engage the leftwardly-facing edges of the first and second pairs of scissor arms 32 and 34, as shown in
In each of cam followers 140, 142, 144, 146, roller element 156 is located laterally inboard of roller element 158 and is in rolling contact with an edge of a second scissor arm 40, and laterally outboard roller element 158 is in rolling contact with an edge of a first scissor arm 38. Thus, the roller elements 156, 158 of each cam follower 140, 142, 144, 146 rotate in opposite directions as they roll along their respective scissor arm edges.
Each inboard roller element 156 of a cam follower 140, 142, 144, 146 engages a cam surface 150 defined on an edge of a second scissor arm 40 of the first and second pairs of scissor arms 32, 34. Similarly, each outboard roller element 158 of a cam follower 140, 142, 144, 146 engages a cam surface 148 defined on an edge of a first scissor arm 38 of the first and second pairs of scissor arms 32, 34.
As perhaps best shown in
The tension on belts 120a and 120b maintain cam followers 140, 142 and 144, 146 of the first and second pulley arrangements 58 and 88 in engagement with surfaces 150 and 148 of first and second arms 38 and 40 of the first and second pairs of scissor arms 32, 34. Cam surfaces 148, 150 are designed to easily facilitate an initial movement of lift assembly 20A from its lowered state 28 to minimize additional loading on motor 114 than would otherwise be required in the absence of the cam surfaces being so designed. As shown, the cam surfaces 148, 150 establish, in the lowered state 28, a gradual slope along which roller elements 56, 58 are forced to roll in response to belts 120a, 120b being wound onto their respective spools 116. The slope increases somewhat as lift assembly 20A is moved out of its lowered state 28 and axes 96, 106 are pulled laterally toward each other in plane 126. Once the lift assembly 20A has been moved from its initial, lowered state 28, the cam surfaces 148, 150 engaged by followers 140, 142, 144, 146 change their slopes such that the load on motor 114 is maintained at an approximately constant level, and an increased rate of change in height of platform 24 results.
The motor load is derived as a function of the tension force in the segment of belt 120 extending from about spool 116.
Clearly, it would be desirable to avoid the initial, comparatively much higher motor loading in moving from the lift assembly lowered state as the second embodiment lift assembly allows, for the substantially greater initial loading comes with attendant increases in energy use and stresses on the belt and other lift assembly components. However, it is contemplated that a second embodiment scissor lift assembly will likely have greater cost than a comparable first embodiment scissor lift assembly. On the other hand, the relatively flatter motor load curve of the second embodiment scissor lift assembly will likely reduce the need for an expensive motor control system.
Those of ordinary skill in the art will recognize that, in either of the first and second embodiment scissor lift assemblies, motor loading can be reduced by correspondingly increasing the number of first and second pulleys 62, 92 of the first and second pulley arrangements 58, 88 over which belt 120 is wrapped, with belt 120 being correspondingly lengthened to accommodate its increased path. This reduction in motor loading/belt tension would, however, result in comparatively slower travel between the lift assembly contracted and elevated states.
Returning to
First and second pulley arrangements 58 and 88 of second embodiment lift assembly 20A respectively further include shafts 72, 102, that are fixed to and extend in parallel with shafts 64, 94 between laterally spaced blocks or support members 66, 68 and 96, 98. Blocks 66, 68, 96, 98 are preferably structured and interconnected to maintain a consistent orientation of axes 78 and 108 relative to plane 126. They may, for example, both lie in plane 126 as shown. Between the first and second pulley arrangements 58, 88, a pair of blocks (e.g. 66 and 96, or 68 and 98) may be linked together laterally outside the adjacent pair of scissor arms 32 or 34, for example.
Referring now to
Carriage 230, to which platform 224 may be attached, is disposed between a pair of longitudinally extending rails 232 and 234. Carriage 230 is provided with bearing elements 236 that are received in and supported by guide tracks 238, 240 of rails 232, 234. Bearing elements 236 support the load placed on surface 225 of platform 224 when assembly 220 is in a substantially horizontal orientation, or otherwise constrain the movement of carriage 230 away from base 222. Base 222, platform 224, and rails 232, 234 may be made of steel.
In
Respectively disposed about shafts 243 and 245 are like-numbered pluralities of independently rotatable carriage pulleys 252 and 254 which may be identical to above-discussed pulleys 62, 92. Disposed about shaft 247 (or about shafts 247a and 247b) are a plurality of retention rollers 256 which may be identical to above-discussed retention rollers 74, 104. In
Assembly 220 further includes first pulley arrangement 258, shown on the right side of
Referring to the left side of
Extending between first pulley arrangement 258 and carriage 230 is first drive belt 120a, which is guided over a path defined by pulleys 62 and 252. As shown, there are four pulleys 62 in first pulley arrangement 258, identified as 62a-d, and five carriage pulleys 252, identified as carriage pulleys 252a-e. Elongate unitary belt 120a extends from about spool 116a leftwardly to carriage 230 where it is wrapped about carriage pulley 252a, and from pulley 252a belt 120a reverses course and at a slight return angle returns toward first pulley arrangement 258 where it is then wrapped about pulley 62a. From pulley 62a belt 120a reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 252b. From pulley 252b belt 120a reverses course and at a slight return angle returns toward first pulley arrangement 258 where it is wrapped about pulley 62b. From pulley 62b belt 120a reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 252c. From pulley 252c belt 120a reverses course and at a slight return angle returns toward first pulley arrangement 258 where it is wrapped about pulley 62c. From pulley 62c belt 120a reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 252d. From pulley 252d belt 120a reverses course and at a slight return angle returns toward first pulley arrangement 258 where it is wrapped about pulley 62d. From pulley 62d belt 120a returns in a direction toward carriage 230 and wraps about pulley 252e, and reverses course returning toward first pulley arrangement 258 and its second end 122 is affixed to base 222. The return angle along which belt 120a extends between the carriage 230 and the first pulley arrangement 258 is relative to their parallel pulley axes 242, 276 and will vary slightly as carriage 230 moves longitudinally in the directions indicated by arrow 228, the return angle being at a maximum when carriage 230 is rightmost and being at a minimum when carriage 230 is leftmost, as viewed in
Extending between second pulley arrangement 288 and carriage 230 is second drive belt 120b, which is guided over a path defined by pulleys 92 and 254. As shown, there are four pulleys 92 in second pulley arrangement 288, identified as 92a-d, and five carriage pulleys 254, identified as carriage pulleys 254a-e. Elongate unitary belt 120b extends from about spool 116b rightwardly to carriage 230 where it is wrapped about carriage pulley 254a, and from pulley 254a belt 120b reverses course and at a slight return angle returns toward second pulley arrangement 288 where it is then wrapped about pulley 92a. From pulley 92a belt 120b reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 254b. From pulley 254b belt 120b reverses course and at a slight return angle returns toward second pulley arrangement 288 where it is wrapped about pulley 92b. From pulley 92b belt 120b reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 254c. From pulley 254c belt 120b reverses course and at a slight return angle returns toward second pulley arrangement 288 where it is wrapped about pulley 92c. From pulley 92c belt 120b reverses course and at a slight return angle returns toward carriage 230 where it is wrapped about pulley 254d. From pulley 254d belt 120b reverses course and at a slight return angle returns toward second pulley arrangement 288 where it is wrapped about pulley 92d. From pulley 92d belt 120b returns in a direction toward carriage 230 and wraps about pulley 254e, and reverses course returning toward second pulley arrangement 288 and its second end 122 is affixed to base 222. The return angle along which belt 120b extends between the carriage 230 and the second pulley arrangement 288 is relative to their parallel pulley axes 244, 306 and will vary slightly as carriage 230 moves longitudinally in the directions indicated by arrow 228, the return angle being at a maximum when carriage 230 is leftmost and being at a minimum when carriage 230 is rightmost, as viewed in
As described above, first end 121 of each belt 120 is attached to its respective spool 116 and is wound onto or unwound from the spool 116, which changes the length of the path over which the belt 120 extends, the path being defined by the respective pulleys over which it is wrapped. The second end 122 of each belt 120 is affixed to base 222 adjacent the respective first or second pulley arrangement.
Assembly 220 includes a first motor drive assembly 312a which is arranged for pulling belt 120a rightward through rotation of its motor 314a which may be rotatable in only a single direction. As shown, the direction of rotation of motor 314a of motor drive assembly 312a when pulling carriage 230 rightwardly as belt 120a is wound onto spool 116a, is clockwise. In motor drive assembly 312a, the output shaft of motor 314a may extend through a clutch housing 318a that includes a one way clutch which allows belt 120a to be unwound from spool 116a as carriage 230 is pulled leftwardly by second motor drive assembly 312b when motor 314a is de-energized.
Similarly, second motor drive 312b of assembly 220 is arranged for pulling belt 120b leftwardly through rotation of its motor 314b which may be rotatable in only a single direction. As shown, the direction of rotation of motor 314b of motor drive assembly 312b when pulling carriage 230 leftwardly as belt 120b is wound onto spool 116b, is counterclockwise. In motor drive assembly 312b, the output shaft of motor 314b may extend through a clutch housing 318b that includes a one way clutch which allows belt 120b to be unwound from spool 116b as carriage 230 is pulled rightwardly by first motor drive assembly 312a when motor 314b is de-energized.
One of ordinary skill in the art will recognize that motor drive assemblies 312a and 312b are individually and exclusively energized to move a load supported by carriage 230 in one of the two directions indicated by arrow 228. Movement of carriage 230 rightward as shown in
Referring now to
As to a further discussion of the manner of usage and operation of the present invention, the same should be apparent from the above description. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
