US3667126A

US3667126A - Device for locking a rotatable drawing head

Info

Publication number: US3667126A
Application number: US880686A
Authority: US
Inventors: Otto Wackerfuss
Original assignee: Franz Kuhlmann KG
Current assignee: Franz Kuhlmann Praezisionsmechanik und Maschinenbau GmbH and Co KG; Franz Kuhlmann KG
Priority date: 1968-11-29
Filing date: 1969-11-28
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06
Also published as: DE1811805B1; CH493341A; FR2024510B1; FR2024510A1

Abstract

A single operating lever control for locking and unlocking a rotatable head on a drafting machine wherein a lock pawl is released from engagement with the teeth of a ratchet disc. A thumb operated lever extends along the side of the conventional hand knob and may be operated in one of two ways. Upon direct inward movement, the pawl is released only so long as the thumb lever is held. In the other mode of operation, the thumb lever is locked so that the lock pawl is retained out of ratchet disc engagement.

Description

United States Patent Wackerfuss DEVICE FOR LOCKING A ROTATABLE DRAWING HEAD Inventor: Otto Wackerfuss, Wilhelmshaven, Germany Assignee: Franz Kuhlmann KG, Prazisionsmechanik und Maschinenbau, Wilhelmshaven, Germany Filed: Nov. 28, 1969 Appl. No.: 880,686

Foreign Application Priority Data NOV. 29, 1968 Germany ..P 18 ll 805.3

U.S. Cl. ....33/79 R Int. Cl ..B43l 13/08 Field of Search ..33/79 R, 79 A, 79 B, 79 C,

all:

June 6, 1972 References Cited UNITED STATES PATENTS 1,877,340 9/1932 Kuhlmann ..33/79A FOREIGN PATENTS OR APPLICATIONS 944,298 7/1949 Germany ..33/79 R 1,060,287 6/1959 Germany. ..33/79 R 509,935 1/1955 Italy 33/79 R Primary ExaminerI-Iarry N. Haroian Attorney-Dennison, Dennison, Townshend & Meserole [57] ABSTRACT A single operating lever control for locking and unlocking a rotatable head on a drafting machine wherein a lock pawl is released from engagement with the teeth of a ratchet disc. A

-thumb operated lever extends along the side of the conven- 8 Claims, 7 Drawing Figures PATEHTEUJUH 6 I972 3.667. 126

SHEET 2 or v3 hire/liar GT7- 0 wn mzn ss DEVICE FOR LOCKING A ROTATABLE DRAWING HEAD This invention concems'drawing instruments and more particularly a device for locking a rotatable drawing head. In this device shifting members are operated with one single operating thumb member which is movable toward the middle of a hand knob, and which acts through a spring-loaded push rod on a rotatable pawl which engages a ratchet disc. This disc in turn is securely attached to a supporting structure to which are connected the arms of a conventional drafting machine. The pawl is on the underside of a base having a vemier scale which is attached to pivot on the supporting structure, and which supports on its top side the knob and the operating member and the push rod, which is coupled with the pawl by means of a transmission member which engages the pawl through the base.

In one prior art locking device of this general sort, the operating member is securely coupled directly with the push rod, so that the pressure of the operating member toward the middle of the knob causes a direct swinging over of the pawl, out of contact with the ratchet disc. In this case, the elastic trip release of the lock adjustment device occurs in a simple operation, however a permanent release of the lock adjustment device is possible only through an additional turn of the operating member around the drawing head. Such an operation of the hand grip with the thumb placed on the periphery thereof requires movement of the thumb along the periphery of the drawing head which requires either a contortion of the hand in relation to the hand grip or one more segment in the thumb. The aforementioned movements of the thumb therefore necessitate a more or less disadvantageous loosening of the hand from the hand grip of the drawing head. Hence, the feeling of a secure hold on the drawing head in the particular position is more or less lost to the operator. Such a manipulation of the locking device is unsatisfactory.

In another prior art device, the movement of the thumb along the periphery of the drawing head is not necessary. There is even provided for the permanent release of the locking device a second element which is directly below the member used for operation of the locking device and which secures the first elementin the inwardly depressed position. In this model, one operating member must connect with the other.

The object of this invention is the construction of a locking device that is operable with one single operating member without grasping by the thumb and without additional peripheral manipulation.

This problem is solved by a locking device of the sort illustrated herein, in which the push rod is pivoted to a rotatably positioned intermediate link on the base and the operating member is formed as an angle lever, of which one arm serves as a thumb lever. The other arm which lies within the knob is rotatably coupled with the intermediate member and rotates, relative to this, only toward the middle of the knob. The operating member is locked in one position after a horizontal swing and also relative to the intermediate member, in which position the pawl comes out of contact with the ratchet plate. With this construction it is also possible, with one single lever attached to the knob, to achieve a temporary and also permanent pawl release of the ratchet device, without necessitating a change of .position of the thumb with relation to the operating member. The thumb lever thereby accomplishes a purely swiveling movement for the temporary release, while for the permanent tripping a swiveling movement directed toward the middle of the knob is coupled with an inwardly directed displacement. This is possible without change of the thumb position relative to the periphery of the knob, whereby the knob remains securely and stably locked by the left hand, which is advantageous for the accurate operation of the drawing head.

According to a preferred embodiment of the invention, the arm within the knob is shorter than the thumb lever, is linked at its free end to the intermediate member and has a stop with which it abuts the intermediate member when activated by a spring. The arm lying within the knob comes into contact with a head on the intermediate member, whereby the pivoting motion is limited to one direction. The structure of the inner arm being shorter than the thumb lever and consequently the position of the link connection being lower than the upper end of the thumb lever gives a secure and efficient pivot for the resilient tripping of the locking device so that less strength is required for operation.

In a further feature of the invention, the inner arm is forked and the intermediate member is a double layer, whereby the push rods are set between the levers of the intermediate member and this within the forked end of the inner arm. This feature provides for the uniform application of force and consequently the satisfactory operation of the operating member.

According to a further feature of the invention, the intermediate member is pivoted on a bearing support which is secured onto the base, and the operating member is hollow and engages the bearing support. This embodiment allows a compact structure.

A singular simplification of the structure is given in that a further feature of the invention shows that the bearing support has a catch for the spring which activates the pawl and a recess for the spring which biases the operating member, and which is structured as a coil spring and engages a projection on the inner side of the angle lever and supports an abutment for a stop within the thumb lever. This refinement is especially advantageous with all abutments are united in one single structural element. This provides on one hand an economization of space and on the other hand simplified production.

Another feature of the invention is that the knob has a detachable cap which supports a cylindrical, inwardly turned collar with a peripheral ridge which catches in a corresponding peripheral groove in the bottom cylindrical portion of the knob. With this construction, it is possible, although the shifting members inside the knob are easily accessible, to mount retaining latches or the like inside, without modification of the flat external shape. Through the use-of a relatively long ring which rests against the wall in the lower cylindrical portion of the knob, a completely secure locking of the cap is obtained.

In the drawings:

FIG. 1 is a vertical section through a drawing head;

FIG. 2 is an enlarged section along linesII-II of FIG. 1;

FIG. 3 is a view similar to FIG. 1 of the shifting members in the resilient release position in the knob;

FIG. 4 is an enlarged detail view of portions of FIG. 3;

FIG. 5 is a view similar to FIG. 3, wherein the shifters are in the permanent release position;

FIG. 6 is an enlarged detail view of portions of FIG. 5; and

FIG. 7 is a plan view of the drawing head with the cap removed.

Reference is now made specifically to the drawings wherein like reference numerals designate similar parts throughout several views.

On rods 1 of a drafting machine is a drawing head 2 with its fixed support 3. In the support 3 is a bearing 4 secured thereto by screws. A scale square 6 is secured within bearing 4 by a rotatable bearing element 6a. The bearing element 6a is attached securely as by screws to a base 8, which supports a knob 10. The upper part of knob 10 is formed as a detachable cap 11. To the scale square 6 is attached the straightedge 5 (FIG. 7) and on the other side thereof is attached base shield 7 in order to protect the drawing head. In order to determine the angular displacement of the angle device of the scale square 6, a vemier plate 9 is securely attached to the support 3 and has thereon an angle graduation scale. The rotatable base 8 opposite this vemier plate, which is securely attached to the scale square 6, is provided with a vernier scale.

On the side of support 3 which is toward the base 8 is attached a ratchet plate or disc 12, with which a pawl 13 cooperates. The pawl is pivoted on the underside of base 8 by means of a pin 13a, which also serves as support for transmisof the structure I sion member '14' engaging through base 8, which, through drivepin 14a, is connected with the pawl 13. The ratchet plate 12 is so formed that locking of the drawing head is possible aftera rotation of 15.

For the operation of the pawl 13, the angled end of the transmission member 14 engaging through base 8 is connected with a push rod 15, which engages a short diameter end pin la through abore in the transmission member 14 and is secured by means of a spr'ing 15b. The other end of the push rod 15 is linked with an intermediate member or link 18, which is formed a adouble lever, pivotedby means of a bolt 16. The intermediate member 18 is rotatably mounted on a bearing block 20 (FIG. 2) on the base 8 by means ofa bearing bolt 19. Between the-two levers of the intermediate member 18 is a spacer 19a. The operation of these shifting members within the.knob,10 is instituted by an operating member 17 .which is formedas an angle lever, whereby one arm 17a extends through an opening a into the inside of the knob 10 and with its bifurcated end is pivotably connected by the bolt 16 with the intermediate-member 18. The operating member 17 is hollow and engages the bearing block 20. The arm 17b lying outside the knob serves as a thumb lever. A pin 22 on the bifurcated arm 17a comes into contact with intermediate arm 18 in'.response to a coil spring 21 acting on the operating member 17,and thereby limits the pivoting movement of the operating member 17' with respect to the intermediate member to a radial outward direction with respect to the knob. I t

The bearingblocklo has a recess20a for housing the coil spring 21- which engages a projection 25 integral with and within theoperating member 17. On the end of the bearing blocklying within knob 10 is formed a catch 26 on which one end of a tension spring 24 is engaged. This spring is connected with the transmission member 14, and hereby the pawl 13 is urged against the ratchet plate 12. On the opposite end the bearing block 20 has an'abutment 20b with which stop 23 in the form of a transverse rod cooperates, and which is within operating member 17. 1

The detachable capot' the knobhas an inwardly oriented ring-1 1a, which has a ridge at its lower end which fits into-a corresponding groove in the cylindrical: member 10b of the knob. -R ec.esses 11b and 11c in the ring 11a guarantee complete freedomof movement of the shifting members lying within the knob. 1

The drawing head-described is operated as follows. If the scale square 6 is to be swung with its drawing rules 5 out of a certain angular position determined by an engagement of the pawl 13, the thumb lever 17a of the operating member 17 is moved by lifting-movement of the thumb in the direction toward the knob shown in FIGS. 3 and 4, 'whereby the intermediate member 18 limits the pivoting movement by contact with a stop 27. Hereby the intermediate member 18 pivots, .whereby the pin 22 in contact withthe intermediate member causes the simultaneous movement of the intermediate member 18 and the operating'member '17. The movement of the intermediate member 18 causes displacement of the push rod against the bias of the spring 24, whereby the transmission member 14 and the pawl 13 coupled with it pivot outwardly around the pin 13a, and free the pawl from the ratchet plate 12. Now the scale square can be pivoted in relation to the'support 3, so long as the thumb lever 17b remains in the upward pivoted position. After release of the thumb lever 17b, the pawl 13, in response to spring 24, relocks in the next ad- 7 jacent groove of the ratchet plate.

If the scale square remains free from the support structure, the pawl 13 does not relock into ratchet plate 12 at the release of the thumb lever 17b, so that the thumb lever, in addition to its pivoting movement, must also be pressed inwardly which requires a force below the bolt 16. At this combined movernent the intermediate member 18 is pivoted and the push rod is moved, which disengages the pawl 13. Besides, because of the inward pressure the operating member pivots in relation to the intermediate member 18 around the pivoting pin 16,

whereby the pin 22 is released by the intermediate member 18. The pivoting is continued untilthe locking pin 23 locks behind the abutment 20b. This position, in which the pawl 13 remains free until further operation of the thumb lever, is shown in FIGS. 5 and 6. If the thumb lever is raised somewhat, so that the locking pin 23 frees itself from the abutment 201:, the pawl 13 is brought back into engaged position by the spring 24, whereby the shitting

members

14, 15 and 18 return to their original positions, shown in FIG. 1. The operating member is brought again to the initial position by the spring 21, whereby the pin 22 lies against the intermediate member What 1 Claim As My Invention And Desire To Protect By Letters Patent Of The United States ls:

1. A device for locking a rotatable drawing head of a drafting machine having a rotatable support means with scale squares extending therefrom, a toothed ratchet plate secured to said support means, a lock pawlsrotatable into and out of engagement with the teeth of said ratchet, base means, said pawl being rotatably mounted on said base means, a hollow hand knob connected to said base means, a lock operating thumb lever having a thumb engaging portion extending along the outside of said knob and an arm portion'extending inside said knob, an intermediate link member rotatably pinned at one end to the arm portion of said thumb lever, said thumb lever being movable inwardly relative to said link member, a push rod pivoted at one end to the said one end of said link member, said push rod acting against a transmission member attached to said lock pawl, spring means normally urging said lock pawl into ratchet contact, and lock pin means operable after a given inward'movement of said thumb lever to move said link member with said thumb lever and to thereby displace said push rod and transmission member and release said lock pawl from said ratchet plate upon continued inward movement of said thumb lever, said lock pawl returning into contact with the ratchet plate upon release of said thumb lever. Y

2. A device for locking a rotatable drawing head as defined in claim 1 and further including means to retain said lock pawl out of ratchet plate engagement after release of said thumb lever.

3. A device for locking a rotatable drawing .head as defined in claim 1 wherein said arm portion is of a length less than the thumb engaging portion and coil spring means urging said lock pin means against said link member after inward thumb lever movement commences.

4. A device for locking a rotatable drawing head as defined in claim 1, wherein said arm portion is bifurcated, said link member comprises two spaced similar plates within the bifurcated arm portion, and said push rod being pinned between said plates.

5. A device for locking a rotatable drawing head as defined in claim 3, wherein the link member is pivoted at its other end to a bearing block, said bearing block being mounted on said base means.

6. A device for locking a rotatable drawing head as defined in claim5 and further including a catch on said bearing block, said spring means being connected at one end to said transmission member and at the other to said catch,said bearing block also having a recess and said thumb lever having a projection on the inside thereof, said coil spring means'having one end engaging said projection and the other end thereof received in said recess.

7. A device for locking a rotatable drawing head as defined in claim 2 wherein said means to retain said lock pawl out of ratchet plate engagement includes a bearing block mounted on said base means, said bearing block having an abutment and a locking pin on the inside of said thumb lever engageable against said abutment.

8. A device for locking a rotatable drawing head as defined in claim 1, wherein said hand knob is provided with a detachable cap.

Claims

1. A device for locking a rotatable drawing head of a drafting machine having a rotatable support means with scale squares extending therefrom, a toothed ratchet plate secured to said support means, a lock pawl rotatable into and out of engagement with the teeth of said ratchet, base means, said pawl being rotatably mounted on said base means, a hollow hand knob connected to said base means, a lock operating thumb lever having a thumb engaging portion extending along the outside of said knob and an arm portion extending inside said knob, an intermediate link member rotatably pinned at one end to the arm portion of said thumb lever, said thumb lever being movable inwardly relative to said link member, a push rod pivoted at one end to the said one end of said link member, said push rod acting against a transmission member attached to said lock pawl, spring means normally urging said lock pawl into ratchet contact, and lock pin means operable after a given inward movement of said thumb lever to move said link member with said thumb lever and to thereby displace said push rod and transmission member and release said lock pawl from said ratchet plate upon continued inward movement of said thumb lever, said lock pawl returning into contact with the ratchet plate upon release of said thumb lever.

3. A device for locking a rotaTable drawing head as defined in claim 1 wherein said arm portion is of a length less than the thumb engaging portion and coil spring means urging said lock pin means against said link member after inward thumb lever movement commences.

6. A device for locking a rotatable drawing head as defined in claim 5 and further including a catch on said bearing block, said spring means being connected at one end to said transmission member and at the other to said catch, said bearing block also having a recess and said thumb lever having a projection on the inside thereof, said coil spring means having one end engaging said projection and the other end thereof received in said recess.