Improvements in and connected with Worm Gearing and Casings therefor, and in Means for Securing Rotating Bodies upon Shafts.
Year: 1893

page_text: Date of Application, 10th May, 1893
Complete Specification Left, 10th Feb., 1894-Accepted, 17th Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements in and connected with Worm Gearing and Casings
therefor, and in Means for Securing Rotating Bodies upon
Shafts.
I, MICHAEL HOLROYD SMITH, of 161 Trinity Road Upper Tooting, in the
County of Surrey, Engineer, do hereby declare the nature of this invention to be
as follows:-
This invention relates to improvements in and connected with worm gearing and
casings therefor and in means for securing a rotating body such as a worm wheel
upon a shaft or the like.
The class of worm gearing and casing to which this invention relates is preferably
that described in the Specification to Letters Patent No. 5664 of 1886. According
to the present invention the casing is formed with grooves or channels in its upper
part near the worm shaft so that the oil which is taken up by the worm wheel from
the lower part of the casings and is delivered to the worm, is, when thrown off by
the latter in its rapid revolution caught by the channel or channels and delivered
to the bearings or thrust block of the worm shaft.
For these bearings or thrust block I preferably employ balls carried between
removeable races the arrangement of the races worm and worm shaft being such
that after the shaft is withdrawn the worm races and balls may be clamped
together and lifted out without disturbing any other parts as in this construction
the thrust is taken directly by the bosses at the end of the worms and is
independent of the shaft.
The shaft is secured to the worm by a feather or feathers secured in long slots in
such a manner that the shaft may have a considerable endwise movement without
affecting the relation of the worm and wheel.
The casing is preferably formed in unequal halves the upper portion carrying
the worm wheel and parts above same so that the worm shaft (which may be the
armature shaft of an electric motor) may be withdrawn and the upper half of the
casing opened and thrown up for examination of the teeth of the worm wheel.
The lower part of the casing forms simply an oil reservoir and may be fitted with
an oil supply pipe the height of which will regulate the height of the oil in the
casing.
In securing a rotating body upon a shaft such as the worm wheel above referred
to upon the shaft it is intended to drive it has heretofore been the custom to
employ a square or nearly square key arranged so that about one half its bulk is in
the usual groove in the shaft while the other half is in a corresponding groove in the
hub of the wheel or the like the disadvantage of which is that the thrust upon one
corner of say the upper half is transmitted diagonally through the body of the key
to the opposite corner of the lower half so that the strain upon the key is always
tending to turn same over with the result that a key of this description soon wears
and loosens.
In place of such a key there is employed according to the present invention two
oblong keys one on each side of the shaft placed on either side of the centre line if
the shaft is not subject to reversals of its motion but placed on the same side if
subject to same. These keys are so arranged that one flat long side lies in the
groove in the shaft together with one shallow edge while the other edge and flat
side lie in a groove in the boss of the wheel, the thrust being so transmitted that
the upsetting action is minimized and the whole of the width of the key on both
sides is available for driving purposes.

page_text: In order that forms of teeth may be used different from those usually employed
on worm and gear wheels it is proposed to employ a shorter worm than usual and
to quicken the pitch at one or both ends depending upon whether said gear is
intended to reverse or not.
Dated the 10th day of May 1893.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Chartered Patent Agent,
For the Applicant.
COMPLETE SPECIFICATION.
Improvements in and connected with Worm Gearing and Casings
therefor, and in Means for Securing Rotating Bodies upon
Shafts.
I, MICHAEL HOLROYD SMITH, of 161, Trinity Road, Upper Tooting, in the
County of Surrey, 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. :-
This invention relates to improvements in and connected with worm gearing
and casings therefor and in means for securing a rotating body such as a worm
wheel upon a shaft or the like.
The class of worm gearing and casing to which this invention relates is preferably
that described in the Specification to Letters Patent No. 5664 of 1886.
In order that the invention may be clearly understood reference is made to the
accompanying drawings which form part of this Specification and in which
Fig. 1 is a side elevation partly in section of apparatus arranged according to this
invention. Fig. 2 is a sectional elevation on the line a r of Fig. 1. The method
of keying the worm wheel on the driving shaft is shown in Fig. 3, while Fig. 4 is
a plan view of the worm and adjacent parts, the top cover being removed, and
Fig. 5 is a diagrammatic view of a worm.
According to the present invention the casing is formed with grooves or
channels 1 in its upper part near the worm shaft 2 so that the oil which is taken
up by the worm wheel 3 from the lower part of the casings 4 and is delivered to the
worm, is, when thrown off by the latter in its rapid revolution caught by the
channel or channels and delivered to the bearings or thrust block of the worm
shaft.
For these bearings or thrust block I preferably employ balls 5 carried between
removeable races 6. 6. the arrangement of the races worm and worm shaft being
such that after the shaft 2 is withdrawn the worm races and balls may be clamped
together and lifted out without disturbing any other parts as in this construction
the thrust is taken directly by the bosses at the end of the worms and is independent
of the shaft.
The shaft is secured to the worm by a feather or feathers 7 secured in long
slots in such a manner that the shaft may have a considerable endwise movement
without affecting the relation of the worm and wheel. Or the method of keying
illustrated in Fig. 3 and hereinafter described may be employed.
The casing 4 is preferably formed in unequal parts the upper portion carrying
the worm wheel, the worm and spindle and when desired the electric or other
motor attached to the plate 14 and the whole may rest upon and be hinged to the
lower half which in the case illustrated forms an oil well and foundation plate.
To examine the teeth of the worm wheel or cleanse the oil well it is only necessary
to remove the bolt 12 and the whole upper portion can be turned back on the
hinge 13.
In other cases when the upper is fixed, held by the plate 14, or otherwise then

page_text: the lower portion forms simply an oil well which can be rocked down for cleansing
and examination.
In securing a rotating body upon a shaft such as the worm wheel 3 above
referred to upon the shaft it is intended to drive it has heretofore been the custom
to employ a square or nearly square key arranged so that about one half its bulk
is in the usual groove in the shaft while the other half is in a corresponding
groove in the hub of the wheel or the like the disadvantage of which is that the
thrust upon one corner of say the upper half is transmitted diagonally through the
body of the key to the opposite corner of the lower half so that the strain upon
the key is always tending to turn same over with the result that a key of this
description soon wears and loosens.
In place of such a key there is employed according to the present invention
one or two oblong keys 9, 9, if two, one on each side of the shaft placed on either
side of the centre line if the shaft is not subject to reversals of its motion, but
placed on the same side as shewn if subject to reversal. These keys are so
arranged that one flat long side lies in the groove in the shaft 10 together with
one shallow edge while the other edge and flat side lie in a groove in the boss 11
of the wheel, the thrust being so transmitted that the upsetting action is minimized
and the whole of the width of the key on both sides is available for driving
purposes.
In order to secure the maximum bearing surface between the worm thread and
wheel tooth and to eliminate as far as possible the rack and pinion element
accentuating the screw and nut action, the worm thread is made with a variable
lead by quickening the angle at each end thus securing the clearance required for
the wheel teeth to roll in and out of contact. Fig. 5 shows diagramatically the
method employed exaggerated for the sake of clearness. A short worm can thus
be used and the sides of the worm thread and wheel teeth can approximate to
straight lines.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In the casings of worm gear grooves or channels partially surrounding the
worm and shaft and adapted to deliver the lubricant collected therein to the
bearings substantially as described.
2. In the casings of worm gear a case formed in unequal parts, the lower forming
an oil reservoir supplied from a suitable pipe, the upper part being provided with
bearings carrying the worm wheel, all substantially as and for the purposes set
forth.
3. The combination with a driving shaft of a worm carried thereon and bosses
or bearings taking the thrust directly from the worm and independently of the
shaft substantially as set forth.
4. In worm gearing a thrust block consisting of removeable races enclosing balls
a worm bearing upon one side of said races and a permanent bearing upon the
other side substantially as set forth.
5. The improvement in keying together a shaft and surrounding boss substan-
tially as described.
6. In worm gearing a worm practically engaging throughout its entire length
with the worm wheel, the thread of such worm being quickened at one or both ends
substantially as and for the purposes set forth.
Dated the 10th day of February 1894.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Chartered Patent Agent,
For the Applicant.