US2488992A - Dashpot for portable tools - Google Patents

Description

I-NVEN'TOP ATTOPFJEY Jon L. 727

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Application May 2l, 1947, Serial No. 749,567

2 Claims.

This invention relates to a feed mechanism for 'I'he primary object of the'present invention is to provide in a feed mechanism of the character stated means of a simple and eilectual character for maintaining under pressure the oil or other liquid in the entire space on. opposite sides of the piston and in the by-pass so as to insure that such space shall be completely filled with oil Vor other liquid.

A further object is to facilitate the filling of the dashpot spaces with oil or other` liquid.

A portable power operated drilling 'apparatus is described and claimed in an application led in the name of John L. Taylor on March 15, 1946, under Serial No. 654,533, and entitled Pneumatic drill guide. By way of example, the control mechanism of the invention is shown and de-L scribed in connection with this' apparatus in the accompanying drawings and specication. This showing will now be described in detail, illustrat` ing the general principles of the invention; but

work 4, together with a coupling means generally designated 9 for restraining Athe guide 6 against movement due to the reaction of the motor I during the drilling operation. This coupling means constitutes the subject matter of my co-pending application Serial No. 602,592. Briefly, it comprises a member Il) secured to the guide 6 and a member II secured to the jig 1, 1

is provided for detachably connecting the guide 5 to the jig 1. Appropriate angular and lateral movement between the members I0 and II causes inter-engaging surfaces formed on the members to lock the members togethenopposite movement releasing the members.

The guide 6 Iis provided with a hand grip I2 and a control member I3 for manipulating and controlling the operation of the drill. The member I3 is so arranged that, with the member in one position, the motor I is lde-energized, and airy under pressure is admittedto the annular chamber I4 between the. internal .ange G-a on the` guide and the externaliiange 5-2 on-the carriage. This urges thedrill to the retracted position shown.

,Movement-of the member I3 to the left by the operator will cause energization of the motor I and admission of air under pressure to the space I5 between the internal flange B--a and the exl it is to be understood that this description is notv i to be taken in a limiting sense, since the mechan-- Fig. 2 is an end elevation, as seen from the left in Fig. 1; v f f Fig. .3.is a detail section showing the control valves;

Fig. 4 .is a detail sectionshowing a modiied valve arrangement; and

ILbeing vented. Thus the drill y3, or other tool,

such as areameror a tap,;will be rotated by the motor I, and advanced by axial movement of the carriage 5. When the tool 3 has advanced to the desired depth, the member I3 is permitted to return to its original position de-energizing vthe motor I, readmitting air pressure to the chamber Il, and venting-chamber I5, kcausing the carriage Fig. 5 is a detail section showing a'further modiilcation.

Referring to Fig. 1, al conventional motor for 5 to move to the Vleft and retract the Ycutter I. This mechanism is described in detail in the said prior application.

generally indicated by the numeral 2S), and comprises a member 2I having an exteriorly threaded end portion 22 cooperating with a threaded .pory tion 23, formed on the guide 5, to secure the mechanism 20 to the guide.

operating a drill, or the like, is generally indicated by the numeral I, and is shown as havinga chuck 2 mounting a twist drill 3. The work to be drilled is indicated at 4. The motor VI is secured in a carriage 5 movable axially in the cylindrical guide or housing 6. A drill jig 1 is provided for locating the drill 3 withrespect tothe The `member 2I provides a cylinder25'c1osed` l y at oneend by-an integral wall 26 having an elon- I gated boss 21 thereon, `and at the opposite end A pistonll is provided in the cylinder ,25, be-

ing sealed against the cylinder wall, asby a conventional 0. ring packing` 3l. Thepiston 30 is.

tlxed on a piston rod 32 which extends in opposite directions through the closures 25 and 28 of the cylinder 25 in a fluid-tight manner, 0 ring packings 33 and 34 being provided about the rod 32 in the closures 25 and 28 respectively. The rod 32 is secured to the carriage 5, as by a threaded extension 35, thus connecting the piston 30 for movement with the carriage 5.

The opposite end of the rod 32 also has a reduced threaded extension 35 carrying a pair of knurled nuts 31 and 38. The nut 31 serves, by contacting the end of the boss 21 to limit the movement to the right of the piston rod 32 and connected parts, thus serving to restrict the advance or penetration of the drill or other tool 3 to a desired depth. The nut 38 serves to lock the nut 31 in adjusted position.

The cylinder 25 is lled with a suitable liquid 33, such, for example, as that commonly used with hydraulic brakes on automotive vehicles. A by-pass port 40 serves to connect the cylinder space on opposite sides of the piston 30-to permit liquid flow therebetween in response to movement of the piston.

A needle valve structure 4I is provided for controlling the rate of such flow. Thus, the port 40 (Fig. 3) is provided with an enlarged openended extension 42, the outer-end portion of which is threaded for accommodating the valve member 43 which has a correspondingly threaded intermediate body portion 43-a. The valve member 43 has a knurled head 43-b and a cylindrical body extension 43-c which closely fits the unthreaded portion of the port extension 42, and is shown as provided with a resilient packing ring 44 to prevent escape of the liquid 33. The valve member 43 also has a reduced body extension 43-d with a tapered end 43e engageable with a correspondingly tapered seat 45 provided in port 40. A light compression spring 45, conned under the head 43-b, serves to retain the valve member 43 in adjusted position.

It will be apparent that force urging the piston 30 to move axially in cylinder 25 will create a pressure on the liquid 33 ahead of the piston 30, and that movement of the piston will depend on the amount of liquid permitted to pass through the port 40 to the space behind the piston. Accordingly, adjustment of the needle valve 4| serves to control the rate of movement oi the piston 30, the carriage 5, and the drill 3 carried thereby.

In general it is the rate of feed or advance of the drill 3, or other cutting tool which must be closely controlled in accordance with the size and function of the cutting tool, as well as with the character of the material being worked; the retraction or-withdrawal of the tool can be accomplished at a much faster rate which may be substantially constant. Accordingly, an auxiliary by-pass port 43 (see Fig. 3) is provided through the piston 30 controlled so as to pass liquid only when the piston 33 moves in a direction to withdraw the drill 3.

Referring to Fig. 3, the port 43 has a reduced portion forming a shoulder 43-a, the opposite end portion being threaded for receiving a seat member 49. This member has a port 43-a adapted to be closed by a closure member 50, such as a steel ball, which is urged to seat by a small spring 5I confined between the ball 53 and the shoulder 43-a.

When the piston 30 is urged to the right, as by air pressure acting in chamber l5, the speed oi advance of the piston 3D, the carriage 5, and

4 the drill 3 is controlled by the rate of liquid ilow past the valve 4I, the pressure of the liquid maintaining the valve member 50 seated and the port 48 closed. When the piston 30 is urged to the left by air pressure acting on the carriage 5 in chamber I4 to retract the tool 3, the liquid pressure on the left side of the piston 30 unseats the valve member 50 so that port 48 supplements the port 40. Thus, the return movement is much faster.

In case the tool 3 is a thread-forming tool, such, for example, as a tap, it is preferable that the retraction occur at substantially the same rate as the advance. Furthermore, the motor i must be of a type capable of operation in either direction at the same speed, so as to back the tool from the work after forming the threads.

For this purpose the auxiliary by-pass 48 is optionally rendered inoperative. This may be done conveniently by replacing the ported Seat member 49 with a solid plug 52 (see Fig. 4.) In this way, the movement of the piston 35 in either direction is controlled by the setting of the needle valve 4I.

The needle valve 4I is shown in fully closed position in Figs. 1 and 2. It is to be understood, however, that the valve may be opened to any dgsired extent by adjustment of valve member It is desirable to maintain spaces through which fluid 39 circulates completely full at all times. One manner in which this is assured is illustrated in Fig. 5.

'I'he needle valve, as before. is formed between seat 45 and the tapered end 53 of a screw member 54 threaded into the end wall 25 of cylinder 25. The member 54 is hollow, having a port 55 that establishes communication between the space to the left of piston 30, and the space 55 within screw 54. This space serves as a reservoir forliquid. which is automatically adjusted by a piston 51 slidable in space 55.

To facilitate illling the cylinder spaces with liquid after the screw 54 is installed, a ball check valve 53 cooperating with a port 50 through piston 51, is utilized. This ball is urged toward seated position by a compression spring 5|, the left-hand end of which is conned by a headless screw 82 that is vented at 53 and threaded into the head of screw 54. An 0 packing ring 34 may be provided for the piston 51.

Spring 4i is quite stil! and keeps the ball 53 normally seated. and also keeps piston 51 in a position to maintain all of the liquid spaces filled.

To iill the device, the screw 54 is rst turned in part way, leaving the needle valve entirely open. The ball 53 and spring 5l are not yet in place, nor is set screw 62. Now the device is lled, through port 55, with oil or other liquid until all spaces are filled. Then ball 53 and spring 5I are dropped in place, and the headless screw 62 is installed. Then screw 54 is turned in to the desired position. The piston 51 moves enough in screw 54 to equal the reduction in volume due to the turning in of the screw 54. Loss of liquid in the system is taken up by movement of piston 51; and expansion of the liquid is also compensated by movement of the piston in the other direction.

The inventor claims:

1. In a device of the character described: means forming a chamber; a movable wall in the chamber; means forming a port connecting the spaces on opposite sides of the wall; and an ad- :mesma Justable valve in said port to control the rate of liquid iiow from one side of the wall to the other; and means in said valve forming an adjustable space in communication with said port, and including a plunger mounted for movement in said space, means forming an abutment at the end oi the space, anda spring interposed between said plunger and said abutment means and urging said plunger in a direction to reduce laid adjustable space.

2. In a device of the character described: means forming achamber: a movable wall in the chamber; means forming a port connecting the spaces on opposite sides of the wall; means forming a valve seat in the port; a. screw having an end cooperating with the seat to control the port opening; said screw being hollow and having a passage communicating with the interior oi' the screw and the port; and a movable wall in the screw and resiliently urged in a direction to reduce the volume oi' the space.

JOHN L. TAYLOR.

REFERENCES CITED The following references are of record in the me of uns patent:

Smith Aug. 1, 1944

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