Improvements in and connected with Worm Gearing and in its Arrangement in connection with Elevator Apparatus.
Year: 1899

page_text: Date of Application, 22nd Mar., 1899
Complete Specification Left, 19th Dec., 1899-Accepted, 3rd Mar., 1900
Improvements in and connected with Worm Gearing and in its
Arrangement in connection with Elevator Apparatus.
I, ERNST GUSTAV HOFFMANN, of Hamlet House, Chelmsford, in the County of
Essex, Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to certain improvements in and connected with worm
gearing and in its arrangement in connection with elevator apparatus.
According to one form of my invention the worm may be of any usual or
convenient form, though the actual tooth is of a construction hereinafter described,
but in place of employing teeth on the worm wheel, or it may be the rack as an
equivalent thereof I insert studs on the periphery of the wheel either in line
with the radius or in line with the axis of the wheel,-
-or on the face of the
rack-and upon each of said studs a ring shaped roller having the outline of the
tooth it substitutes revolves on a ball bearing. In the case of an elevator such
racks would be preferably fixed to the sides of the well and the worm or worms
to the car platform, or of some suitable part of the car which would also carry a
suitable motor preferably electric with shafting and gearing connecting it to the
worm or worms to rotate same and thus move the car positively up or down, the
arrangement enabling the gearing to be self locking and permitting the car to
be counterbalanced to the extent desired.
When the worm is used in combination with a worm wheel it is preferable to
mount the rollers on the sides of the periphery of the wheel instead of the outer
periphery of same.
The ball bearing employed for the rollers consists of a stud one end of which
is provided with a head so formed as to be suitable for one track of the ball bear-
ing and below this the stud is screw-threaded and carries a ring adjustable on
the thread and forming the other track of the ball bearing and having a seat in,
preferably a recess in the part forming the base of the rack or the like the interior
face of the roller being suitably shaped to adapt itself to the balls. For securing
the stud to the wheel or the part forming the base of the rack or the like in such
a manner that it may be easily and securely applied from the outside which is
desirable in the case of a rack of an elevator when the base part is in its fixed
position. I utilise the difference in pitch of two threads in the manner herein-
after described, one of the threads being that for the adjustable ring above referred
to, and the other the usual screw thread employed to secure a stud bolt or the
like in a fixed part such thread being formed on the end of the stud.
For the first thread as an example I employ a pitch of 24 threads to an inch and
for the second thread I employ a pitch of say only 20 threads to the inch. When
screwing the stud into the fixed part it will be obvious that 20 threads per inch
will pull the stud into the rack faster than the 24 threads per inch will permit

page_text: the stud to move through the adjustable ring of the bearing and hence as the
latter is held to its seat on the part forming the base of the rack a strain is set
up between the two screws which affords a means of jamming or locking the stud
in the part in which it is being screwed. To further secure this stud against the
effects of concussions or vibrations. I may employ a small set screw so arranged
that it engages with the stud tangentially the end of the screw being cone shaped
for this purpose:
The thread or tooth of the worm I prefer to make of a special shape but what-
ever its shape according to my invention I provide that it shall not only bear
on the ball bearing roller but also shall be extended, diametrically to enable it to
enter the part forming the base of the rack or the like for which purpose a slot
is provided therewith of greater width than that of the party of the tooth passing
therein so that no contact is made with such part but an abutment is provided for
the teeth of the rack to engage with, should the stud and roller with which the
worm normally engages be broken off in which event the worm teeth would
engage with the slot (which would be preferably formed to provide a solid
continuous tooth on the rack) and thereby prevent (in the case of an elevator) the
car from falling.
+
[
I prefer that the faces of the worm teeth for this purpose where they are not
in contact with the ball bearing roller should be flat and parallel but the faces
which are in contact with the roller are formed at an angle similar to that of
bevel gearing, the angles of the faces opposite each other meeting in the axes of
the worm a construction which enables flat surfaces to be employed with an
increase contact surface. These could only be employed however if the periphery
speed of the points in contact were the same, which condition is fulfilled when
the point of contact can be constructed in the same way as bevel wheels.
17
Where the worm engages with a wheel instead of a rack the rollers would be
Becured to the side of the wheel instead of to the circumference and this con-
struction permits of using two worm wheels one on either side of the worni so
that both the dimensions of the ball bearing roller and the diameter of the worm
can be reduced.
"
Or the
In this case it is desirable that both worm wheels should be in gear with the
worm even if the divisioning of the ball bearing roller should be faulty and to
this end the two worm wheels might be mounted on their respective shafts in
such a manner that they would be compensating as between the two so as to
prevent any one wheel bearing more in any case than half the strain.
worm wheels might be fixtures on their shafts and the worm be slightly move-
able laterally as between the two wheels so that should the ball bearing rollers
on one side press heavily against the worm the worm would yield" sidewardly and
thus ensure the rollers on both sides bearing with equal pressure against the
worm. To accomplish this various constructions could be used, for instance the
worm might be mounted on a shaft in a kind of ball and socket joint, or on a
slide which moves sidewardly in which event of course the worm would require
to be attached to its shaft by a suitable coupling.
Where'it is desired to stop or hold the worm as in the case where it is applied
to elevator apparatus the worm may be provided on the exterior or interior with
a cone or suitable surface with which may engage a corresponding cone or surface
acting like a clutch and forming a brake which would be operated by some
suitable means.

page_text: Improvements in and connected with Worm Gearing and in its
Arrangement in connection with Elevator Apparatus.
I, ERNST GUSTAV HOFFMANN, of Hamlet House, Chelmsford, in the County of
Essex, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and-by the following statement:—
My invention relates to certain improvements in and connected with worm
gearing, and its arrangement in connection with elevator apparatus the object of
same being to produce a practical worm gearing adapted both by reason of its
easy running, absence of friction and its great safety for various mechanical
purposes, such as for elevator work where the use of a rack and worm is even
safer than a hydraulic ram by reason of the whole gearing being self locking or
holding in any position, so long of course as the worm does not exceed a certain
amount of incline.
According to one form of my invention the worm may be of any usual or con-
venient form, though the actual tooth is of a construction hereinafter described,
but in place of employing teeth on the worm wheel, or it may be the rack as an
equivalent thereof, I insert studs on the periphery of the wheel either in line
with the radius or in line with the axis of the wheel-or on the face of the rack-
and upon each of said studs a ring shaped roller having the outline of the tooth
it substitutes revolves on a ball bearing of a special construction.
In the case
of an elevator such racks would be preferably fixed to the sides of the well and
the worm or worms to the car platform, or of some suitable part of the car which
would also carry a suitable motor preferably electric with shafting and gearing
connecting it to the worm or worms to rotate same and thus move the car
positively up or down, the arrangement enabling the gearing to be self locking
and permitting the car to be counterbalanced to the extent desired.
I also employ various other details in carrying out my invention some of which
form an important feature of same and which will be claimed as part of same.
In the accompanying drawings illustrate various forms of my invention and
the manner of carrying it into effect. In these drawings
Fig. 1 is a section of a part of a worm and rack, the worm being partly in
elevation.
Figure 2 is a sectional plan through the rack and one of the roller studs shewn in
Fig. 1, the worm being viewed in plan.
Fig. 3 is a front elevation of an elevator platform and part of a well shewing
my invention applied thereto the side walls of the well being in section.
Fig. 4 is a side elevation of Fig. 3 partly in section on line y y of said figure
looking the direction of the arrow.
Fig. 5 is an elevation on a larger scale than Figs. 3 and 4 of the rack, worm,
and a part of certain appliances connected thereto.
Fig. 6 is a plan of the worm shewn in Fig. 5.
Fig. 7 is a modification, being a side elevation of a worm wheel engaging
with a worm.
Fig. 8 is a cross section through line
Fig. 7.
Fig. 9 is a similar view to Fig. 8 but shewing a modification of the worm
wheel.
Fig. 10 is a plan view partly in section of a modified arrangement over that
shewn in Figs. 7 and 8 in which the worm is allowed a play or movement and
Fig. 11 is an end view of same.

page_text: The gearing may consist of the ordinary form of worm but I prefer to use the
special form shewn most clearly in Figs. 1 and 5 where it will be seen that the
ordinary bevelled faces 1, 1 of the tooth of the worm 2 which engage in the present
case with the rollers are provided with a prolongation 4 which enters into the-
angularly arranged grooves 5 on the rack bar or base that is to say the tooth is
so extended diametrically that it enters the solid part of the rack. These grooves
or slots however have a margin of space on both sides of the tooth so that the
latter is not actually in contact with the rack, the object of this extension or
prolongation of the tooth being to provide a safety device whereof the tooth may
actually engage with a solid rack in the event of one of the rollers breaking
although normally the tooth is out of contact with this portion of the rack.
This forms a safety device of considerable value where much depends upon the
worm as in the case where same is used in elevator work.
The faces of the worm teeth are flat but of such an angle with the rollers as if
the two were bevel, wheels, the two angles meeting in the axis of the worm, this
construction enabling flat and therefore increased contact surfaces to be employed.
The rollers 3 as will be understood replace the usual teeth of the rack each
-roller being ring shaped and having the outline of the tooth it substitutes. The
ring or roller 3 is mounted on a ball bearing of the kind known as a "single row 4
track bearing." The head 7 of the stud 8 which holds the roller is conical on its
under side and forms a part of the ball bearing cone and adjoining it is a move-
able double cone 9 fitting on the stud by a screw thread 10 having for instance
24 threads per inch while the end of the stud is also provided with a screw
thread 11, which (with 24 threads on the first) preferably has only 20 threads per
inch this latter screwing into the rack body or base 6. Between the outer face
of the cone 9 and the cone face of the head 7 is situated a row of balls 12 which
bear on the double coned face forming the interior of the ring or roller 3. The
head 7 of the stud projects from the outer face of the ring and is suitably shaped
to enable it to be held by a wrench or tool so that the stud may be screwed into
the rack. The inner face of the cone 9 seats in a correspondingly shaped recess
in the rack base 6. It will be seen that in this way the stud may be screwed on
to the base 6 from the outside but in the operation of an elevator service for
instance it will be appreciated that unless some device were provided to secure
the stud the concussions would have a tendency to loosen it.
The device which I employ is the above described arrangement of the two
threads which are non-corresponding in their pitch together with if desired a
locking device.
With such threads when screwing the stud into the rack it will
be obvious that the 20 threads per inch portion will pull the stud into the rack faster
than the 24 thread per inch portion will allow it to pass through the cone 9 which
is seated in the rack base so that a slight straining is set up through the difference
between the two small threads with the result that a very gradual tightening of
the parts is produced, the operation being practically the same as if a screw
having 120 threads per inch were employed without the disadvantages which such
a fine thread as the latter would have.
As a matter of practice it may be said that with this construction of 24 and
20 threads per inch respectively one complete turn of the stud can be given to
same after the parts have just begun to tighten and this one complete turn shews
to what extent the members have been strained and jammed together.
The incline of the threads being thus so small no danger exists of the stud being
loosened by concussions when the above method is employed. To furthermore
secure the stud I employ a set screw 13 which passes through from the side of
the rack base 6 and is provided with a conical end 13 which bears tangentially
against the plain portion of the stud 8 and jams the latter after it has been
tightened up.
In applying the foregoing arrangement of parts to an elevator as shewn in 5
Figs. 3 to 6 I preferably employ two of the worms 2 and place them beneath the
platform 14 driving them by means of an electric motor 15 through a shaft 16

page_text: and couplings 17 the shafts 16 on the other side of said couplings driving
through bevel wheels 18, 18* (Fig. 5) the worms 2. Each worm is carried on
suitable bearings in a bracket 19 consisting of a top part, a bottom part 19b and
two vertical connecting bars, said brackets having a third connecting bar 19*
which is bolted at 19° to the upper part of the bracket 19 at the top and carries
the upper half 20 of the bearing for shaft 16. The lower half 20 of the bearing
is formed as part of the bottom 19. By releasing the bolt 19° the bar 19* can
be removed together with the upper part 20 of the bearing so that after undoing
the coupling 17 the part 16 of the shaft with the bevel wheel 18 can be removed
whereby the worm 2 can be reached for repair or removal.
To the bar 19 is pivoted at 21 lever 22 the yoke shaped end of which pivotally
carries a cone shaped ring or disc 23 which fits into a correspondingly shaped
recess 23 in the upper part of the worm 2 one of such coned parts bearing a
leather or other suitable facing. The lever 22 may be operated in some suitable
and well known way from the car and as will be seen may act on the coned part 23
to cause it to act as a clutch or brake or holding device for the worm in which
manner the worm proper becomes the means for stopping the car, the arrange-
ment being preferable to applying a brake direct to the motor shaft as the worm
is in direct and positive engagement with the rack.
The above described arrangement of gearing being absolutely self-locking
permits the car to be counterbalanced to any extent desired because the car can
neither go up nor down but can only move in the direction in which the worms
drive it as said worms wind their way either up or down the rack.
When the worm is used in connection with a worm wheel it is preferable to
mount the studs with their rollers on the side of the periphery of the wheel or at
right angles to such periphery as the arrangement affords greater facility for
carrying the construction into effect.
The advantage of this ball bearing and gearing is also very great when it
becomes necessary to drive the worm instead of the worm wheel. Such gearing
is frequently used where high speed is required but no great power is to be
transmitted except that wanted to create the speed.
As at present constructed such gears require the worm to have a very rapid
incline in order to make them work at all satisfactorily whereas the angle of the
worm thread can be much reduced when the present arrangement is employed
in consequence of the friction between the worm and the worm wheel teeth (which
in this instance are the rollers) being reduced to a mere rolling friction as against
a rubbing one in the ordinary construction.
In the construction shown in Figs. 7 and 8 the ball bearing rollers 3 are
carried on the opposite side of a yoke shaped portion 24* of the worm wheel 24
that is to say on the inside of such part 24 and opposed to each other, this double
construction enabling the dimensions of the ball bearing rollers forming the
worm wheel teeth and naturally the diameter of the worm to be considerably
reduced. The extension or safety teeth 4 in this case I prefer to form on the worm
wheel 24 on the crown of the part 24 the teeth passing between the teeth 1 of
the worm 2 but not engaging with same unless through the breakage of some of
the rollers. The teeth 4 however may be formed on the teeth 1 in the same way
as previously described and enter grooves in the parts 24ª between the rollers in
the same way.
It is desirable where the rollers are duplicated as in the above instance that
necessarily the rollers on both sides should be in gear with the worm which
might not be the case if the divisioning of the wheel in the setting of the rollers
is at all faulty. To obviate this I may employ the arrangement shewn in Fig. 9
where it will be seen that the worm wheel 24 is divided into two parts 24b
and 24° which are loose upon their shaft 25 so that they are compensating, the
play enabling the worm to bear equally on a roller on each side. The two
parts 24 and 24° drive through a number of pins 26 a wheel 24d placed between
the two parts 24 and 24° and fixed to the shaft 25, such pins 26 being pivotally

page_text: hung on studs 27 in slots 28 which studs are formed in this instance as screws
passing from the periphery of the wheel 24d through the slots. In this way the
pins while serving to drive wheel 24d can yet rock sufficiently to enable the com-
pensating movement to take place between the parts 24b 24°.
•
Or, when the worm wheel is arranged substantially as shewn in Figs. 7 and 8
that is to say is a fixture the worm may be allowed to be slightly moveable
laterally as between the two sets of rollers so that should those on one side press
heavily against the worm the latter will yield sidewardly and thus ensure àn
equal pressure on both sides. To accomplish this various constructions could be
used for instance the worm might be mounted on a shaft in a kind of ball and
socket joint or on a slide which moves sidewardly in which event of course the
worm would require to be attached to its shaft by a suitable coupling.
One arrangement which has been found suitable is shewn in Figs. 10 and 11.
In this the worm wheel 2 is provided with an opening through same formed with
outwardly flaring mouths at each end, as shewn at 30,, the curvature through the
hole being that of the segment of a circle which touches the shaft only at the
central point. The worm is capable of revolving with the shaft through a key 31
secured to the shaft and engaging in slots 32, the arrangement enabling the worm
to be drawn off the shaft. The worm is provided further with a central boss
portion the ends 33 of which are struck on the curve of a circle and which corre-
spond with abutments 34, 34, having similar curved faces; one of these abutments
being held against the boss portion of the worm by means of nuts 35 engaging
with a screwed portion of the shaft which forces the other abutment against a
fixed collar 36.
When the pressure of the nuts is properly adjusted the worm will be able to
rock slightly on the ball and socket joint which is thus formed and so may
adjust itself to inequalities of the other member.
=
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. In a worm gearing and in combination with the worm forming one member,
a revoluble ring forming part of the other member, a double cone face on the
inside of the ring, a stud for carrying the ring provided with a head having a
cone face, a second adjustable cone face carried by the stud, and antifriction balls
between the cone faces of the stud and ring substantially as described.
2. In a worm gearing, the combination with a roller forming a part of one
member thereof, a stud for holding same having separate threaded portions of a
different pitch, a base into which one threaded portion screws, and a threaded
part carried by the base into which the second threaded portion screws whereby
a straining or jamming is set up between the two parts as the stud is screwed in
substantially as described.
3. In a worm gearing and in combination a revoluble roller forming a part
of one member, a threaded stud for carrying same, a base forming a further part
of the same member, into which the stud is screwed, a further threaded portion
on the stud, the threads of which are of a different pitch to the first threads, an
adjustable párt, carried by such further threaded portion and adapted to seat on
the base whereby when the stud is screwed into the base a straining and jamming
is set up between the part seating on the base and the threaded portion screwing
into the latter substantially as described.
4. In a worm gearing, and in combination a revoluble ring forming a part of
one member, a threaded stud for carrying same, a cone shaped head on the
stud, a base forming a further part of said member into which the stud is screwed,
a further threaded portion on the stud the threads of which are of a different
pitch to the first threads, an adjustable cone shaped part carried by the latter.
threaded portion and adapted to seat on the base, and antifriction balls carried
between this coned part, the coned head, and the ring, the difference between the

page_text: pitch of the threads causing a straining and jamming between the part seated
on the base and the threaded portion screwing into the latter when the stud is
screwed in substantially as described.
5. In a worm gearing, the combination with a roller forming a part of one
member thereof, a stud for holding same, having separate threaded portions of
a different pitch, a base into which the threaded portion screws, a threaded part
carried by the base into which the second portion screws, whereby a straining
and jamming is set up between the two parts as the stud is screwed in, and a set
screw having a conical head screwing into the base and adapted to engage
tangentially with the stud substantially as described.
6. In a worm gearing, the combination with a worm forming one member
thereof, of rollers forming a part of the other member thereof, and means carried
by one of the members, and adapted to engage with the other member, in the
event of the rollers giving way substantially as described.
7. In a worm gearing, and in combination a worm forming one member
thereof, having a tooth provided with a prolongation and a base forming a part
of the other member thereof provided with grooves with which said prolongation
can engage in the case of a breakage of a part forming the rest of the member
substantially as described.
8. In a worm gearing, the combination with rollers forming one member
thereof, a base for carrying same, and grooves on such base between said rollers,
of a worm forming the other member the tooth of said worm being prolonged
to engage with said grooves in the event of the rollers giving way substantially as
described.
9. In a worm gearing a worm forming one of the members of same, a worm
wheel forming the other member of same two sets of antifriction rollers oppositely
arranged with which the worm engages means for carrying the rollers and means
for equalizing the pressure of the rollers on both sides of the worm substantially
as described.
10. The improved arrangement and combination of worm gearing and elevator
apparatus substantially as described and illustrated in the drawings.
Dated this 19th day of December 1899.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent for the Applicant.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent for the Applicant.