GB2055638A

GB2055638A - Drill stand work table feed

Info

Publication number: GB2055638A
Application number: GB8023443A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-08-06
Filing date: 1980-07-17
Publication date: 1981-03-11
Also published as: BR8004801A; CA1138687A; DE3029797A1; IT8049432A0; AU6020280A; FR2462956A1; FR2462956B3; GB2055638B

Abstract

An elevator for a drill stand table (16) comprises a sprocket chain (24) suspended at the top of the drill column (14) to extend vertically downwardly along the column, and a companion sprocket wheel (36) mounted on the table for rotation about a substantially horizontal axis. A friction brake mechanism (54, 56) restrains angular movement of the sprocket wheel and holds the table in the vertical position thereby determined. A crank (62) connected to the sprocket wheel (36) rotates the sprocket wheel up or down the chain (24) correspondingly to position the table (16). Optionally, a ratchet mechanism (70, 74) allows the crank to override the brake in the up direction of the sprocket to relieve required effort. Angular chain positioning is allowed by a bearing (32) supporting the chain bracket (34) running in a groove (30) in a column collar (28). <IMAGE>

Description

SPECIFICATION Drill press This invention relates to a drill press, and particularly, to a mechanism for elevating and lowering a drill press table.

Drill presses ordinarily utilize a simple split collar and draw bolt mechanism for clamping the work table to the drill press column.

Adjustment of work table height is crude and tedious. Refined mechanisms for achieving adjustment have been suggested. U.S. Patent No 2,122,966 typifies the present state of that art and discloses a gear mechanism including a gear rack supported at the side of the drill press column. A worm, a worm wheel and pinion are all supported beneath the work table in a bearing block cast integrally with the work table. The worm and worm wheel arrangement prevents gravity from driving the gear mechanism in reverse whereby the table maintains its adjusted position even if the column clamp is open. The gear mechanism is a bit complex and, consequently, expensive.

One difficulty with such a mechanism is that the lifting and lowering of the table is necessarily slow due to the inherent high gear ratio between the worm and worm wheel. A practical problem is that lightweight drill presses cannot be inexpensively priced if provided with such a table elevating mechanism.

No practical way has heretofore existed for adding a table elevator to a drill press, whether of the heavy duty or lightweight class.

An object of the invention is to provide a simple mechanism for elevating a drill press table, free of the foregoing disadvantages.

More particularly, the invention provides an inexpensive mechanism that allows rapid and definitive adjustment of the table height.

Another object of the invention is to provide a mechanism so simple that it may be attached to an existing drill press without modification of the drill press table or its parts.

According to this invention a sprocket chain is suspended at its top by a simple circular track and roller arrangement. To the table collar or to another part of the table, there is clamped a reversible crank mechanism that includes a horizontal crank shaft mounting a crank arm and a sprocket wheel held in engagement with the sprocket chain. The crank arm is frictionally restrained against rotation.

Movement of the crank arm directly drives the sprocket, thereby causing the sprocket rapidly to move upwardly or downwardly along the chain, corrspondingly to elevate or lower the table. In a preferred embodiment, a one-way drive or ratchet mechanism is interposed between the crank arm and the friction brake so that the friction of the brake need not be overcome when the table is elevated, but only when the table is lowered. When the table is elevated, a pawl overrides the ratchet which serves as a backstop. The friction brake is at all times operative to prevent runaway movement.

The invention will now be described by way of example, with reference to the drawings, in which :- Figure 1 is a pictorial view of a drill press to which is attached an elevator mechanism incorporating the present invention; Figure 2 is an enlarged horizontal sectional view through the drill press and attachment, showing the crank mechanism, the view being taken along a plane corresponding to line 2-2 of Fig. 1; Figure 3 is a segmented vertical sectional view taken along the offset plane corresponding to line 3-3 of Fig. 2; Figure 4 is an elevational view, partly in section, showing the chain and sprocket structure and taken along the plane indicated by line 4-4 of Fig. 3; Figure 5 is a horizontal sectional view, similar to Fig. 2, but showing a modified bracket structure;; Figure 6 is an axial sectional view through the crank mechanism, and taken along a plane corresponding to line 6-6 of Fig. 5; Figure 7 is a side elevational view of the chain and sprocket structure, and taken along a plane corresponding to line 7-7 of Fig. 6; Figure 8 is a sectional view of the attachment bracket and taken along a plane corresponding to line 8-8 of Fig. 5; Figure 9 is an axial sectional view similar to Fig. 6, but showing a modified crank mechanism in which the crank arm is directly connected to a brake plate.

The following detailed description is of the best presntly contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for purposes of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Structural and operational characteristics attributed to forms of the invention first described, shall also be attributed to forms later described, unless such characteristics are obviously inapplicable or unless specific exception is made.

A conventional drill press 10 shown in Fig.

1 has a table 12 clamped to the drill press column 14 by the aid of the usual split collar 16 and draw bolt 18. The table 12 is made as a casting, there being bracket arms 20 (Fig. 2) joining the collar to the work part 22 of the table 12. As used hereinafter, the word "table" refers to the entire part supported on the drill press column.

The table 12 is guided for vertical movement by the fitted relationship of the collar 16 and the column 14. The table 12 rides up and down along a sprocket chain 24. The sprocket chain 24 is suspended from a two part bracket 26 (Fig. 3) clamped to the top of the drill press column 14. Companion parts of the bracket 26 provide a plate 28 in which a circular raceway or channel 30 is formed. A roller bearing 32 rides in the channel 30. The upper end of the chain 24 is attached to the roller bearing 32 by the aid of a C-shaped bracket 34 that encompasses the edge of the plate 28. The bracket 34 locates the chain 24 in alignment with the bearing 32 to maintain a proper tracking relationship. The chain 24 extends vertically in spaced relationship to the drill press column 14.

The table 12 is connected to the sprocket chain 24 by a sprocket wheel 36. The sprocket wheel is rotatably mounted on one side of a supporting block or bracket 38 attached to the table. The sprocket wheel 36 has a hub 40 secured to one end of a shaft 42 centrally supported in a horizontal bearing aperture of the block 38. The other end of the shaft cooperates with mechanisms to be described hereinafter. The block or bracket 38 is affixed to the table 12 by the aid of upper and lower jaws or arms 46 and 47. These jaws extend above and below the sprocket wheel 36 on one side of the block 38. The jaws project beyond the sprocket wheel 36 and respectively overlie the upper and lower end surfaces of the mounting collar 16. Set screws 48 and 49 secure the jaws to the collar.The jaws 46 and 47 are sized and proportioned so that the axis of the sprocket wheel 36 is skew to the chain, and so that the sprocket wheel 36 is spaced from the column 14 to engage the sprocket chain 24. The chain 24 passes through aligned apertures 50 and 51 in the upper and lower attachment jaws 46 and 47.

Normally, the draw bolt 18 secures the table to the column 14. If adjustment of the table height is desired, the draw bolt is released. The weight of the table is transmitted through the collar 16 and shaft 42, and tends to cause the sprocket wheel 36 to rotate downwardly on the chain 24. However, such movement is resisted by a friction brake structure. The brake structure includes a friction plate 54, a brake plate 56, a brake spring 58 and a stop nut 60. The stop nut 60 is threadedly mounted on the end of a hub 62 formed on the outside of the block or bracket 38 remote from the sprocket wheel 36. The friction plate 54 surrounds the hub and is adhered by cement, rivets or other means to the outer face of the bracket 38. The brake plate similarly surrounds the hub 62 and is slideable thereon.A brake spring 58 also surrounds the hub and is interposed between the brake plate 56 and the stop nut 60 thus to move the brake plate 56 into firm engagement with the friction plate 54. The brake plate 56 is accordingly restrained from rotation.

The shaft 42 is connected to the brake plate 56 so that the shaft 42 and sprocket 40 are likewise restrained from rotation. For this purpose, a crank body 62 is attached, as by a set screw 64, to the outer end of the shaft 42. The crank body has an outboard block 66 extending over the stop nut 60. The block provides an elongated aperture 68 paralleling the shaft 42. Guided in the aperture 68 is a hollow pawl 70 urged, in turn, by a compression spring 72 to engage ratchet teeth 74 that crown the brake plate 56. A key and pin or other means (not shown) maintain the pawl 70 in suitable orientation for engagement with the ratchet teeth 74. Torque tending to rotate the sprocket wheel 36 downwardly on the chain 24 tends to rotate the crank body 62 and pawl 70 in a direction to lock against the ratchet teeth 74.

In order to move the shaft 42 to cause the sprocket 40 to climb up or descend down the chain 24, correspondingly to move the table, the crank body 62 is rotated by hand. For this purpose, a handle 78 (see also Fig. 2) is provided. The handle 78 and crank body 62 together form a crank arm for the shaft 42.

The handle 78 extends through an aperture 80 in the crank body 62 and is secured by a set screw 82. Movement of the handle 78 and crank body 62 in one direction causes the sprocket wheel 36 to climb up the sprocket chain as the pawl 70 ratchets over the restrained brake plate 56. Movement of the handle 78 and crank body 62 in the opposite direction forces the brake plate 56 to move along the friction plate 54. The brake plate 56 is, at all times, yieldingly restrained.

Movement of the crank handle 78 achieves very rapid adjustment of the table, since the drive between the sprocket wheel 36 and the crank is direct and unencumbered with any additional stage of gearing. An exact position of the table can readily be obtained, since if the discrete ratcheting movement overshoots a desired position, it is merely necessary to force the ratchet teeth in the reverse direction.

The angular orientation of the table about the column 14 can be adjusted without requiring any special operations. Thus, as the table is rotated, the chain follows along its overhead channel 30.

To ensure continuous engagement of the chain with the sprocket wheel, a chain guide 84 is provided (Fig. 4) that is attached to an embossment on the inside of the block or bracket 38. The guide 84 defines with the sprocket wheel 36, a narrow channel for the chain so that it at all times engages the sprocket wheel 36. A weight 86 (Fig. 1) is attached to the lower end of the chain which stabilizes it and prevents it from whipping about.

After the table is adjusted, the draw bolt 18 preferrably is retightened so that undue stress need not be absorbed by the chain during work operations.

No part of the drill press need be modified or discarded for purposes of installation of the drill press table elevator. Installation of the elevator is relatively simple, requiring the placement of the upper chain suspension bracket 26 and the main bracket 38.

In the form of the invention shown in Figs.

5 through 8, a bracket 100 rotatably mounts a sprocket wheel 102 as well as a guide 104 (Fig. 7) for the sprocket chain 106. As in the previous form, the bracket 100 carries a friction plate 108 and a ratchet crowned brake plate 110.

The bracket 100 in the present form is attached not to the collar 11 2 of the drill press table, but instead to one of the ribs or arms 114 radiating therefrom. For this purpose, a clamp 116 is attached to the rib 114 (Fig. 8) as by providing a channel 118 for receiving the rib. Set screws 120 secure the clamp 116. The clamp 116 is connected to the sprocket bearing bracket 100 by the aid of a bar 122. Slots 130 and 132 (Fig. 5) in the bar allow passage of attachment bolts 126 and 128 that respectively engage the clamp 116 and the bracket 100 from below (see also Fig. 6). The bar adequately offsets the elevator assembly from beneath the drill press table. The slots 130 and 132 in the bar allow the sprocket wheel bracket 100 to be moved angularly and linearly to align the sprocket wheel 102 with the suspended sprocket chain.

Although the alternative embodiment includes parts identical to those of the preferred embodiment, various changes of components can be made. For example, the brake plate, instead of having ratchet teeth formed as a crown, could be formed at the edge for a less compact arrangement. Furthermore, one way drive mechanisms other than ratchet mechanisms could be used.

In the form of the invention shown in Fig.

9, a bracket 150 similar to the bracket 100 of the previous form is attached to the drill press table by suitable means. The bracket 150 rotatably supports a crank shaft 152. A sprocket wheel 154 is mounted on one end of the crank shaft 152 for engagement with the sprocket chain 156 as before. The other end of the crank shaft is angled to form a crank arm 158 and handle 160.

Angular movement of the crank mechanism is restrained by a friction brake structure that includes a friction plate 162, a brake plate 164, a brake spring 166 and a stop nut 168, all similar to the brake structure of the previous forms. In the present instance, however, the crank arm 158 is directly, rather than indirectly, coupled to the brake plate 164. For this purpose, the crank arm 158 carries a drive pin 170 that enters a peripheral slot or recess 172 in the brake plate 164.

Downward adjustment of the table is accomplished by moving the crank mechanism in one direction. As in the previous forms, gravity assists in overcoming the friction force of the brake structure. Upward adjustment of the table is accomplished by moving the crank mechanism in the other direction. In the present instance, no one way drive mechanism is provided; hence, both gravity and the friction force must be overcome. To compensate for the increased effort required for upward movement of the table, the crank arm 158 may be lengthened. The structure, however, retains major advantages of the forms previously described by allowing rapid adjustment of table height.

Claims

1. A drill press comprising: a column; a table mounted for vertical movement on the column; a sprocket chain suspended from the drill press and extending vertically along the side of the column; a bearing block or bracket; a shaft mounted by the bearing block for rotation about its axis; means connecting the bearing block to the drill press table to orient the shaft axis substantially horizontally; a sprocket wheel rotatably mounted by the block and in engagement with the sprocket chain so that angular movement of the sprocket wheel is accompanied by corresponding vertical movement of the drill press table; a yieldable friction brake continuously restraining angular movement of the sprocket wheel; and manual drive means for rotating the sprocket wheel whereby the table can be quickly elevated and lowered.

2. A drill press according to claim 1 wherein said manual drive means includes a ratchet mechanism causing the friction brake to yield upon movement of the sprocket wheel in a down direction, and causing said friction brake to maintain position upon movement of the sprocket wheel in an up direction.

3. A drill press according to claim 1 or claim 2 wherein sprocket chain is suspended by a circular track coaxial with the column and by a bearing or wheel freely movable along the track whereby angular movement of the table about the column causes corresponding movement of the sprocket chain.

4. A drill press according to claim 1 wherein said manual drive means is directly connected to said friction brake so that said brake is caused to yield during both upward and downward adjustment of the drill press table.

5. A drill press according to claim 1 wherein said manual drive means is indirectly connected to said friction brake by the aid of a one way drive mechanism so that said brake need not yield during upward adjustment of the drill press table; the force of gravity exerted on said brake mechanism assisting said manual drive means in overcoming the friction force of said brake during downward adjustment of the drill press table.

6. A drill press comprising: a column; a table having a collar mounted on the column; a sprocket chain suspended to extend vertically along the side of the column; a bearing block or bracket; a shaft mounted by the bearing block for rotation about its axis; mean connecting the bearing block to the drill press table to orient the shaft axis substantially horizontally; a sprocket wheel carried by the shaft and in engagement with the sprocket chain so that angular movement of the sprocket wheel is accompanied by corresponding vertical movement of the drill press table; yieldable friction brake means continuously restraining angular movement of the sprocket wheel; and manual drive means for rotating the sprocket wheel shaft whereby the table can be quickly elevated and lowered.

7. A drill press according to claim 6 wherein said connecting means comprises a pair of jaws or arms extending from said block or bracket and releasably clamped to opposite end surfaces of said table collar.

8. A drill press according to claim 7 wherein said jaws or arms respectively project above and below said sprocket wheel, said jaws or arms having clearance openings through which said sprocket chain passes.

9. A drill press according to claim 6 wherein said connecting means comprises a clamp attached to part of the table and a slotted bar attached both to the clamp and said bearing block or bracket, said slotted bar allowing longitudinal and angular movement of the bearing block to align said sprocket wheel to the chain.

10. An attachment for a drill press having a column, a table including a collar mounted on the column for vertical movement thereon, the attachment comprising: a sprocket chain assembly including a sprocket chain and means supporting the chain adjacent the top of the column so that the chain extends vertically downwardly along the column; a sprocket wheel in continuous engagement with the sprocket chain; bracket means detachably connected to said table and mounting said sprocket wheel for angular movement about a substantially horizontal axis; yielding brake means continuously restraining movement of said sprocket wheel; and manual drive means for rotating the sprocket wheel.

11. An attachment for a drill press having a column and a table including a collar mounted on the column for vertical movement thereon, the attachement comprising: a sprocket chain assembly including a sprocket chain and means supporting the chain adjacent the top of the column so that the chain extends vertically downwardly along the column; a sprocket wheel in continuous engagement with the sprocket chain; bracket means detachably connected to said table and mounting said sprocket wheel for angular movement about a substantially horizontal axis; a crank directly coupled to the sprocket wheel; a friction brake assembly, including a brake plate, a friction plate and a spring for urging the brake plate to engage the friction plate; and means forming a ratchet connection between the crank and the brake plate for override ratchet movement therebetween upon movement of the crank in a direction to rotate the sprocket wheel upwardly of the chain and for driving relationship therebetween against the force of said friction brake assembly upon movement of the crank in a direction to rotate the sprocket wheel downwardly of the chain.

12. An attachment for a drill press having a column and a table including a collar mounted on the column for vertical movement thereon, the attachment comprising: a sprocket chain assembly including a sprocket chain and means supporting the chain adjacent the top of the column so that the chain extends vertically downwardly along the column; a bearing block or bracket; a shaft mounted by the block or bracket for rotation about its axis; means attaching the bearing block or bracket to the table so that said sprocket wheel extends substantially horizontally with its axis skew to the chain; a sprocket wheel mounted on the shaft and continuously engaging said sprocket chain; a crank connected to the shaft for rotating the sprocket wheel to cause upward and downward movement of the table; a relatively nonrotary friction member surrounding the shaft; a brake plate rotatably mounted on the bearing block and having a face engageable with the friction member; a spring urging the brake plate to engage the friction member; said brake plate having a circular array of ratchet teeth thereon; a ratchet pawl connected to the crank and engageable with said ratchet teeth; said ratchet teeth being oriented to allow override ratchet movement of the pawl upon movement of the crank in a direction to raise the sprocket wheel, and to cause engagement and yielding movement of the brake plate upon movement of the crank in a direction to lower the sprocket wheel whereby said table is rapidly elevated and lowered.

13. An attachment according to claim 12 wherein said sprocket chain assembly includes means forming a circular track, a rolling member supported in the track and connected to the upper end of the chain whereby the chain moves angularly about the axis of the column upon angular movement of the drill press table.

14. A drill press constructed and arranged substantially as herein described with reference to the accompanying drawings.

15. An attachment for a drill press, the attachment being constructed and arranged substantially as herein described with reference to the accompanying drawings.