LINEAR MOTION APPARATUS

Abstract: A linear motion apparatus, which may include transfer means, for providing accurate linear motion in machinery and other devices. The apparatus includes a base member (11) which has pivoted members (12, 13) mounted at one end of each member to a base member (11) by pivots (15, 16). The free end of the pivoted members (12, 13) are connected by a joining member (14) by pivot points (17, 18). The transfer means includes, a reference member (22) which is pivotally connected at its mid point to the mid point (19) of the joining member (14), a linear member (23) parallel to the reference member (22), and a pair of parallel link members (24, 25) pivotally connecting the reference (22) and linear (23) members at pivots (28, 29, 30, 31) to form a parallelogram. The transfer means also includes stay members (26, 27) and a support means (21), the stay members (26, 27) being connected to the support means (21) at pivot points (32, 33) and to the link members (24, 25).

Description: This invention relates to apparatus for providing accurate linear motion and in particular apparatus for providing accurate linear motion in machinery and other apparatus. In many machines and apparatus it is necessary to provide accurate linear movement of parts. This has proven to be most difficult and expensive. For example known linear bearings which must have low friction qualities and provide substantial accuracy add greatly to the cost of machines such as lathes and the like. The object of the present invention is to provide apparatus that is relatively inexpensive and of simple construction in providing for accurate linear motion. According to one aspect, the invention provides a linear motion apparatus for providing linear motion comprising: a base member having a pair of spaced pivot points providing left and right pivot points respectively; a left rotating member pivotably connected to the left base pivot point, said left rotating member having a left member pivot point at the end thereof opposite to its connect¬ ion to the base member; a right rotating member pivotably connected to the right pivot point of the base member, said right rotating member having a right member pivot point at the end thereof opposite to its connection to the base member; a joining member pivotably connected at its opposite ends to both the left rotating member at the left member pivot point and to the right rotating member at the right member pivot point whereby when the left rotating member rotates about the left base pivot point in a clockwise direction the right rotating member rotates about the right base pivot point in an anticlockwise direction and a point on the joining member midway between the left member pivot point and the right member pivot point describes a substantially straight line locus. According to another aspect the invention provides a linear motion machine having two linear motion apparatus arranged in mirror image including coupling means to couple the midway points of the joining members together whereby both apparatus rotate in sympathy and are prevented from independently of each other. The invention will now be described by way of example with reference to the accompanying drawings in which: Figures.la, 2a and 3a illustrate one fo • * rm of linear motion apparatus according to an embodiment of the invention; Figures lb, 2b and 3b illustrate one form of transfer means according to an embodiment of the invention; Figure 4 shows a linear motion machine having two linear motion apparatus and one embodiment of coupling means according to the invention; and ; Figure 5 shows a similar linear motion machine to that shown in Figure 4 but having a coupling means according to another embodiment of the invention. Like numerals are used for like parts with the like parts in Figures 4 and 5 of the apparatus on the left of the Figures having primed reference numerals for further distinction- The apparatus of the present invention includes a base means preferably in the form of a base member 11, such as a base bar. The base member 11 may form part of the machine in respect of which linear motion is desired and which will be explained more particularly below. The base member 11 includes a pair of spaced apart base pivot points. For a clearer understanding of the present invention the spaced apart base pivot points will be referred to as a left base pivot point 15 and a right base pivot point 16 respectively. It will be appreciated, of course, that the geographical location of the pivot points is not material to the- present invention. The apparatus of the present invention includes a left rotating member 12 pivotably connected to the left base pivot point_15. The left rotating member 12 may be of any suitable configuration and is preferably in the fom of a bar. The left rotating member 12 has a left member pivot 17 at the end opposite to its connection to the base member 11. The apparatus includes a right rotating member 13 pivotally connected to the right pivot point 16 of the base member 11. Preferably the right rotating member 13 is in the form of a bar. The right rotating member 13 includes a right member pivot point 17 at its end opposite to its point of . Preferably the distance between the left base pivot point 15 and the left member pivot point 18 is substantially equal to the distance between the right member pivot point 17 5 and the right base pivot point 16. The apparatus includes a joining member 14 pivotally connected at its opposite ends to both the left rotating member 12 at the left member pivot point 18 and to the right rotating member 13 at the right member pivot point 17 and so arranged 10 that when the left rotating member 12 rotates on its left base pivot point 15 in a clockwise direction the right rotating member 13 will rotate on its right base pivot point 16 in an anticlockwise direction. That is to say when one member rotates anticlockwise the other will rotate clockwise and 15 vice versa. It has been found that a reference point 19 on the joining member 14 midway between the left member pivot point 18 and the right member pivot point 17, during rotation of the rotating members will move along an accurate linear line 20 20. At the exact midpoint the accuracy of that line is close to perfect. . For increased accuracy over a greater length the apparatus above described may be duplicated, one such apparatus being provided in a substantially mirror image of 25 the other and positioned so that the lines of linear- movement of the respective reference points are spaced apart and preferably in parallel. Embodiments of a linear motion machine having two apparatus in mirror image are shown in Figures 4 and 5. 30" In this arrangement the respective reference points 19 and 19' in Figures 4 and 5 may each be provided as a " * reference pivot point. Coupling means are provided so that the respective apparatus are coupled together whereby both apparatus rotate in sympathy and are prevented from moving 35 independently of the other. Any suitable, coupling means may be provided for this purpose. To this end in one alternative the coupling means may comprise a connection between the apparatus which ensures that they must move together and are not capable of any free independent movement. In another 40 alternative (not shown), the coupling means may include a connection which may enable movement of one apparatus to move the other and includes drive means to ensure that independent movement does not occur. The drive means may include gearing, belting systems or any other suitable means. In the first alternative illustrated in Figure 5 a pair of reference arms may be provided each pivotably mounted to a respective reference pivot point. For convenience the arm associated with a first one of the apparatus or the left apparatus of Figure 5 will be termed the first or left reference arm 36 and the other ' the second or right reference arm 37. To ensure that the reference arms move together their free ends may be pivotably coupled to a connecting member 38. A support member may be pivotably mounted to each reference arm. Preferably each support member 39, 40 is coupled to the midpoint of the respective reference arm as shown in Figure 5. The free end of each support member 39, 40 is held or mounted against movement. It has been found that as the reference points 19 and 19' move further from the midpoint above referred to any deviation from the accurate linear movement * of one ' reference point will be compensated by a complementary ' . ■ "" deviation from the- accurate linear movement of the other reference point. This accuracy in linear movement at a point midway of the connecting member is exceptionally high and is maintained over•a substantial distance of movement. In the second alternative shown in Figure 4 a pair of reference arms 34, 34' may be provided each pivotably mounted to a respective reference pivot point 19, 19' and joined together at a common linear point 35 so that they extend at an angle to each other.. Preferably the angle between the reference arms is about 90 . As the reference points move further from the midpoint above re erred to any deviation from the accurate linear movement of one reference point will be compensated by a complementary deviation from the accurate linear movement of the other reference point. Thus accuracy in linear movement at the linear point 35 is exceptionally high and is maintained over a substantial distance of movement. It will be appreciated that whilst in the preferred arrangement the two sections of the apparatus but in mirror image the construction of parts desired and satisfactory results obtained. Similarly it is not essential that the lines of linear movement of the respective reference points be in substantial parallel. Satisfactory results can be obtained where those lines are disposed at an angle. In this event the line of movement of the linear point will accurately bisect the angle between the lines of movement of the respective reference points and compensate for any deviation from the accurate linear movement thereof in view of the complementary nature of the apparatus. Those skilled in the art will appreciate that the bars that make up e various components of the apparatus may be of any suitable shape and form. For example the bars may be made of any material such as aluminium or other metal. Any suitable pivot points may be provided but in the preferred arrangement these are provided by bearings or bushes of plastics or other material. It will be appreciated that by having a pair of apparatus arranged in mirror image linear movement of a point in one direction is possible. Should it be necessary to provide for linear movement in two or three perpendicular ' directions or planes two or three pairs of apparatus arranged in mirror image, one for each direction or plane, may be provided. It will be appreciated, that there is a need to translate the linear motion created at the reference point to a location not encumbered by the various parts of the apparatus. For this purpose transfer means may be provided. Although not limited thereto the present invention provides a novel transfer means shown in Figures lb, 2b and 3b. The transfer means of the present invention includes a reference member 22 pivotally connected to the reference point 19 on the joining member or where a duplicated apparatus is provided the reference member is connected to the linear point 35. Preferably the reference member is connected substantially at a point midway of its length to the reference point 19, 19' or linear point 35. The transfer means also includes a linear member 23 mounted in parallel with the reference member 22 by means of a..pair of parallel link members 24, 25. One link member 24 is • -pivotally connected at one of its ends to an end of the--- reference member 22 and at its other end to the linear member 23. The other link member 25 is pivotally connected at one of its ends to the other en ' of the reference member 22 and at its other end -to the linear member 23. Thus there is provided a four bar linkage comprised by the reference member 22, the linear member 23 and the pair of parallel link members 24, 25. These members provide a parallelogram. The transfer means includes support means. Prefer¬ ably the support means is in the form of a support member 21 or in the form of a part of the machine or the like in relation to which the apparatus is employed. In any event the support means is 'fixed in relation to the base means. The support means may include a pair of spaced apart support pivot points 32, 33 hereinafter referred to as a left support pivot point 32 and a right support pivot point 33. Again the references to left and right should not be taken as restricting on the present invention. The transfer means may include a pair of parallel stay members, a left stay member 26 and a right stay member 27. The left stay member 26 is pivotally connected at one end to the left support pivot point 32 and at its other to one of the link members 25, preferably at a point midway along the length of the link member although this is by no means essential. In similar manner the right stay member 27 is pivotally connected to the right support pivot point 33 and to the other link member 24. The action of the linkage arrangement of the present invention ensures that controlled linear movement of the reference point is transferred to ' a controlled and accurate linear movement of the linear member 23. Those-.skilled in the art will appreciate that this linear movement can be translated to a point remote from the apparatus itself, where controlled and accurate linear movement is required. Additionally the preferred linkage arrangement in translating the motion as it goes through an angle, in the preferred form 90 , reduces substantially any error in pure linear motion by the factor of cosine. It will be appreciated that the apparatus of the present invention has a wide number of uses where the provision of an accurate linear motion is required. For example the apparatus has application in connection with lathes, with grinding machines, with radial arm saws, with milling machines, with planers, with metal'working machines, in general, with cranes, with earth moving equipment, with hacksaws, and with various types of optical equipment. Of course many other applications are envisaged. " It should be appreciated that more than one apparatus according to the invention may be applied to any particular use. For example where additional rigidity is called for one or more sets of apparatus may be located along the length of the intended line of linear motion. A particular advantage of the present invention is that the apparatus provides great accuracy at low cost and in a simple manner. The known linear bearings can be dispensed with. A particular advantage is that there are no exposed surfaces where abrasion can occur and contaminants collect. It should be appreciated that the shape and configuration and mechanical nature of the various parts and components of the present invention as ^ above described are not material to the inventive concept. What is material is the relative location of the various described pivot points in space. Therefore the invention should not be taken as restricted to linearly aligned members but only to the relative location of those various pivot points disclosed as essential. Further those skilled in the art would appreciate that many variations and modifications may be made to the above described arrangement and construction of parts without departing from the scope of the invention defined in the appended claims. ■ - m

Claims: CLA VIS 1. Linear motion apparatus for providing linear motion comprising: a base member having a pair of spaced pivot points providing left and right pivot points respectively; 5 a left rotating member pivotably connected to the left base pivot points, said left rotating member having a left member pivot point at the end thereof opposite to its connection to the base member; a right rotating member pivotably connected to the 1Q right pivot point of the base member, said right rotating member having a right member pivot point at the end thereof opposite to its connection to the base member; a joining member pivotably connected at its opposite ends to both the left rotating member at the left 15 member pivot point and to the right rotating member at the right member pivot point whereby when the left rotating member rotates about the left base pivot point in a clockwise direction the right rotating member rotates about the right base pivot point in an anticlockwise direction and a point on 20 the joining member midway between the left member pivot point and the right member pivot point describes a substantially straight line locus. 2. Linear motion apparatus according to claim 1 including transfer means having: 25 a reference member pivotably connected to said midway point; a linear member mounted parallel to the reference member; a pair of parallel link members, one link member 30 being pivotably connected at one of its ends to an end. of the reference member and at its other end to the linear member, '* . : the other said link member being pivotably connected, at one of its ends to the other end of the reference member and at its other end to the linear member; and, 35. support means fixed relative to the base member. 3. Linear motion apparatus according to claim 2, wherein said support means includes: left and right spaced apart support pivot points; Λ a left stay member pivotably connected at one end ^ the link members; a right stay member pivotably connected at one end to the right support pivot point and at its other end to the other of the link members. 4. Linear motion apparatus as claimed in claim 3, wherein the left and right stay members are connected to a point midway along the length of a respective said link member. 5. Linear motion apparatus according to claim 2, 3 or 4, wherein the midpoint of the reference member is connected to the midway point of the joining member. 6. Linear motion apparatus as claimed in any one of . claims 1 to 5, wherein the distance between the left base pivot point and the left member pivot point is substantially equal to the distance between the right member pivot point and the right base pivot point. 7. Linear motion machine including two linear motion apparatus according to claim 1 arranged in mirror image and including coupling means to couple the respective midway points on the joining members to ensure that both said apparatus rotate in sympathy and are prevented from moving independently of each other. 8. - Linear motion machine according to claim 7, wherein . said coupling means includes a left reference arm associated with one said apparatus and a right reference arm associated with the other said apparatus, one end of said left reference arm being pivotably connected- to said midway point of the joining member of said one apparatus and said xight reference arm being pivotably connected to said midway point of the joining member of said other apparatus, a connecting member pivotably connecting the free ends of said reference arms, a left support member pivotably connected by one end thereof to the left reference arm and the other end being pivotably fixed against movement other than pivotable movement and a right support member pivotably connected by one end thereof to the right reference arm and the other end being pivotably fixed against movement other than pivotable movemen - 9. . Linear motion machine as claimed in claim 8, wherein said left support member is pivotably connected to the midpoint of the left reference arm and said right support member is pivotably connected to the midpoint of the right reference 10. Linear motion machine as claimed in claim 7, wherein said coupling means includes a left reference coupling arm and a right reference coupling arm, one end of said left reference coupling arm being pivotably connected to the midway point of the joining member of one said apparatus and one end of said right reference coupling arm being pivotably .connected to the midway point of the joining member of other said apparatus, the-free ends of said left and right reference coupling arms being pivotably connected together. 11. Linear motion machine as claimed in claim 7, 8 or 9, including transfer means having: a reference member pivotably connected to said midway point of one of said joining members; a linear member mounted parallel to the reference member; a pair of parallel link members, one link member being pivotably connected at one of its ends to an end of the reference member and at its other end to the linear member, the other said link member being pivotably connected at one of its ends to the other end of the reference member and at its other end to the linear member; and, support means fixed relative to the base member. 12. Linear motion machine as claimed in claim U, wherein said support means includes: left and right spaced apart support pivot points; a left stay member pivotably connected at one end to the left support pivot point and at its other end to one of the link members; a right;stay member pivotably connected at one end to the right support pivot point and at- its other end to the other of the link members. 13. * Linear motion machine as claimed in claim 12, wherein the left and right stay members are connected to a point midway along the length of a respective said link member. 14. Linear motion machine according to claim 11, 12 or 13, wherein the midway* point of the ref rence member is connected to the midway point of the joining member. 15. Linear motion machine as claimed in claim 7 or 10 including transfer means having: a reference member ivotabl connected to said ends of said left and right reference coupling arms; a linear member mounted parallel to the reference member; a pair of parallel link members, one link member being pivotably connected at one of its ends to an end of the reference member and at its other end to the linear member, the other said link member being pivotably connected at one of its ends to the other end of the reference member and at its other end to the linear member; and, support means fixed relative to the base member. 16. Linear motion machine according to claim 15, wherein said support means includes: left and righ ' -.spaced apart support pivot points; a left stay member pivotably connected at one end to the left support pivot point and at its other end to one of the link members; a right stay member pivotably connected t one end to the right support pivot point and at its other end to the other of the link members. 17. Linear ' motion machine as claimed in claim 16, wherein, the left and right stay members are connected to a point midway along the length of a respective said.link membe . 18. Linear motion machine as claimed in claim 15, 16 or 17, wherein the midpoint of the reference member is connected to the midway point of the joining member. 19. Linear motion machine or apparatus as claimed in any one of claims 1 to 18, wherein said pivot points and said pivotable connections are provided by bearings or bushes. 20. Linear motion apparatus substantially as herein¬ before described with reference to the accompanying drawings. 21. Linear motion machine as claimed in claim 7, substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: GARWOLI WOLFGANG N
Applicants: GARWOLI ELIZABETH M, GARWOLI WOLFGANG N
Application year: 1981
Main classification: F16H21
IPC codes: F16H21